WO2021151858A1

WO2021151858A1 - Wind power device, electric / optical rotary joint, combined high voltage and fiber optic connector unit, coupling structure and electric cable

Info

Publication number: WO2021151858A1
Application number: PCT/EP2021/051671
Authority: WO
Inventors: Stefan Neuhold
Original assignee: Swiss Inventix Gmbh
Priority date: 2020-01-28
Filing date: 2021-01-26
Publication date: 2021-08-05

Abstract

A wind power device for converting wind energy into electric energy is provided. The wind power device comprises a wind power station (600) and a tether (500) for transferring the electric energy from the airborne wind power station (600) to a ground station (1). Interfaces (610, 250) between the tether (500) and the wind power station (600) as well as between the tether (500) and the ground station (1) are provided. In addition to a wind power device, the present invention also relates to an electric / optical rotary joint (700), a combined high voltage and fiber optic connector unit (701), a coupling structure and an electric cable (850).

Description

TITLE

WIND POWER DEVICE, ELECTRIC / OPTICAL ROTARY JOINT, COMBINED HIGH VOLTAGE AND FIBER OPTIC CONNECTOR UNIT, COUPLING STRUCTURE AND

ELECTRIC CABLE

TECHNICAL FIELD

The present invention concerns a wind power device for converting wind energy into electric energy. Wind power devices of this type usually comprise a wind power station, often also referred to as a flying apparatus, which comprises one or more electric generators for converting wind energy into electric energy, when the wind power station is airborne. The electric energy is transferred from the wind power station to the ground by means of a tether.

The present invention also concerns an electric / optical rotary joint, a combined high voltage and fiber optic connector unit, a coupling structure and an electric cable, which can, but do not have to, be part of such a wind power device.

PRIOR ART

For the conversion of wind energy into electrical energy, wind power devices with airborne wind power stations, also referred to as flying object or flying apparatus, are known and are increasingly being developed. Airborne wind power stations comprise one or more electric generators being mounted on a wind flying object which usually has an airplane-like construction. The propeller-equipped generators are driven by wind and by special flight manoeuvres, in order to produce electric energy. The electric energy is transferred to the ground by means of one or several tethers which connect the airborne wind power station to a ground-based station. In addition to the transmission of electric energy from the generators to the ground, the tethers can also serve to control the flight movements of the airborne wind power station. To bring the airborne wind power station from the ground station into an optimal position in the air for energy production or to retrieve it from a position in the air back to the ground station, the electric generators can be used as electric motors. In these start and retrieving phases of the operation, electric energy can thus be fed from the ground station to the airborne wind power station by means of one or more tethers.

Due to strong and often changing winds and during certain flight manoeuvres, the tethers are exposed to high mechanical tensile stress with varying amplitude. As a result, the electric tethers can show significant elongations of their original lengths under high load conditions. The tethers are also exposed to mechanical stress, when being wound up on a drum in the ground station during the retrieving phase. Bending a tether to the peripheral outer surface of a drum causes compression to the parts of the tether facing the centre of the drum and tension to the parts facing radially outwardly.

The one or several tethers that connect the airborne wind power station to the ground cannot only be used for energy transmission, but can also be used for signal transfer, in order to e.g. send control signals to the wind power station and / or to receive sensor signals from the wind power station. For this purpose, the tether(s) can comprise one or several optic fibers, in order to enable optic signal transmission. The signal transfer from the ground station to the airborne wind power station can e.g. also be established by wireless signal transmission via antennas or by modulated high frequency signals on a coaxial electric system of the tether.

A tether for connecting an airborne wind power station to a ground station is disclosed in the document WO 2016/062735 A1 of the applicant. The tether as disclosed by this document comprises electric conductors for energy transmission in the high voltage range and optic fibers for signal transfer. The tether is able to absorb large tension forces and is resistant against radial compression, while at the same time having a relatively lightweight construction. A method for producing such a tether in an efficient way is disclosed in the yet unpublished European application EP 18 209 728.7 of the same applicant.

A particular challenge in the design of wind power devices of the type mentioned are not only the large longitudinal and radial forces acting on the tether itself, but also the cyclic loads acting on the interfaces between the tether and the wind power station and between the tether and the ground station.

Furthermore, large torsional loads can act on the tether as well as on the interfaces depending on the movements carried out by the airborne wind power station in relation to the ground station during operation. Large torsional loads occur particularly, if the wind power station is not stationary with respect to the ground station, but flies e.g. along circular paths. In order to avoid torsional loads that might lead to damages of the tether and of the respective interfaces, attention has to be paid that the flying path of the wind power station relative to the ground station is reversed regularly. This, however, is not only challenging in practise, but also limits the electric energy generation due to non-optimal flight paths.

Since wind power devices of the type as mentioned are often used in remote areas and on spots that are exposed to wind, such as on hills, mountains, plains or even offshore, there is an imminent risk of lightning strikes, even when the wind power station is in its landed state.

Fiber optic rotary joints are disclosed in documents US 5,157,745 A and US 8,965,151 B1.

SUMMARY OF THE INVENTION

According to a first aspect, it is an object of the present invention to provide a wind power device, which allows the wind power station to fly along arbitrary paths. At the same time, large torsional forces acting on the tether or on the interfaces between the tether and other parts of the wind power device should be avoided.

This object is solved by a wind power device as claimed in claim 1. Further embodiments of the wind power device are provided in dependent claims 2 to 8.

Thus, according to this first aspect, the present invention provides a wind power device for converting wind energy into electric energy, comprising a wind power station with one or more electric power generators that are adapted to convert wind power into electric energy, when the wind power station is airborne; a tether for transferring the electric energy generated by the one or more electric power generators to a ground station; and an air interface for connecting the tether to the wind power station.

The air interface is adapted to connect the tether to the wind power station in such a way, that unlimited rotations of the wind power station with respect to the tether are possible.

By providing a rotatable connection between the wind power station and the tether, the wind power station can fly along arbitrary paths without causing large torsional forces to act on the tether. The wind power station is even able to e.g. fly along figure-8 paths or circular paths without twisting the tether. In the air interface, the electric energy is preferably transferred from the wind power system to the tether by means of one or more sliding contacts.

The airborne wind power station is usually designed as an airplane-like flying object. Thus, the wind power station preferably has an airplane-like configuration, advantageously with a fuselage defining a longitudinal main direction of the wind power station and with an airfoil extending perpendicularly to this longitudinal main direction. Thus, the wind power station can also be referred to as a flying apparatus. The wind power station preferably comprises stabilizers, such as horizontal and vertical stabilizers, e.g. fins, and control surfaces, such as ailerons, elevators and rudders.

The one or more electric power generators are preferably attached on the airfoil and / or the fuselage. The one or more electric power generators usually comprise a propeller and preferably an electric generator in each case. In certain embodiments, the one or more electric power generators can also be used, e.g. for launching and landing, to generate a forward thrust. When the wind power device is in operation and the wind power station airborne, the one or more electric power generators are preferably driven by the apparent wind, and the wind power is converted into electric energy that is transferred to the air interface and via the tether to the ground station. The air interface, which preferably comprises rotationally moveable and hinged parts, is usually fixedly attached on the wind power station.

The tether preferably comprises an elastic core and at least a first layer of electric conductors helically wound around the elastic core. The tether can also comprise an electric insulation layer surrounding the first layer of electric conductors and a second layer of electric conductors that is helically wound around the electric insulation layer. A first semi- conductive layer can be arranged between the first layer of electric conductors and the electric insulation layer. Preferably, the tether also comprises a load-bearing layer for absorbing tensile forces as well as radial compression forces acting on the tether, the load- bearing layer surrounding the first and, if present, second layer of electric conductors and defining the maximal axial elongation of the tether under a maximally to be expected tensile load. The load-bearing layer can comprise a compression resistant layer which is specifically adapted for absorbing radial compression forces and a tensile armour layer which is specifically adapted for absorbing tensile forces. The compression resistant layer can particularly be formed by a tubular hull comprising a plurality of ring-shaped elements and / or of tube-shaped elements, the ring-shaped elements and / or of tube-shaped elements being arranged one behind the other along the longitudinal direction of the electric cable. The tether can particularly be designed as specified in WO 2016/062735 A1.

The electric energy produced by the generators can be in the low- (up to 1 kV) or lower part of the medium-voltage range (1 kV to 52 kV). In order to save weight and decrease the diameter of the tether, the voltage level can, however, be transformed up to the medium- (1 kV to 52 kV) or high-voltage (at least 52 kV, in particular 52kV to 300 kV or more than 300 kV) range, especially for a transferred electric power of above 1 MW. Thus, the wind power device and in particular the one or more electric power generators and the tether can be adapted to these voltages in certain embodiments. Instead of a plane-like configuration, the wind power station could of course also be designed as a captive balloon, an airship or as any other flying object.

The air interface preferably comprises a connection element that is advantageously attached movably on the wind power station, in particular on the fuselage of the wind power station. The air interface preferably enables a releasable connection of the tether to the wind power station.

Unlimited rotations of the wind power station with respect to the tether are possible, if the tether is freely rotatable, i.e. rotatable by more than an arbitrary multiple of 360°, about its longitudinal center axis in the air interface with respect to the wind power station. Thus, the air interface provides a rotary connection between the tether and the wind power station.

In a particularly preferred embodiment, the air interface comprises at least one drive for rotating the tether, i.e. about its longitudinal center axis, with respect to the wind power station. In this way, an active rotation of the tether relative to the wind power station can be provided in the air interface, what allows overcoming friction-related residual torsional loads that might still be acting on the tether, even in the presence of a rotary connection between tether and wind power station. Preferably, the air interface also comprises a rotary encoder for measuring the rotation carried out by the tether with respect to the wind power station.

The wind power station can comprise a position direction and velocity measuring system, in order to determine the exact position in all three room-directions, the flight direction and/or the velocity of the wind power station.

The wind power device can additionally comprise a ground station. The ground station usually comprises at least one drum for storing the tether. The ground station preferably has a rotation unit with at least one drive for rotating the tether about its longitudinal center axis. The provision of the rotation unit in the ground station further helps to avoid any torsion of the tether during operation. Thus, the provision of a device to actively rotate the tether is not only preferred in the air interface, but also in the ground station. By means of the rotation unit in the ground station, it can also be ensured that the tether is not twisted when being wound onto and / or wound off the drum.

The wind power device is preferably adapted to control the wind power station to fly along circular paths and / or along figure-8 paths. The wind power device advantageously comprises a control unit that is configured to steer the wind power station along circular paths and / or along figure-8 paths. By flying along circular paths and / or along figure-8 paths, electric energy can be produced in particularly efficient way by the wind power device and the flight of the wind power station is easy to control especially with regard to long-term operations.

For determining the rotational position of the tether, and in particular for detecting the presence of possible torsional loads acting on the tether, the tether can comprise an orientation marking. The orientation marking preferably extends along the entire length of the tether. It can for example be a marking that is visible to the human eye and / or to an optic sensor. The orientation marking, however, can also be in the form of a surface structure, such as e.g. a groove or a longitudinal elevation, or in a not necessarily visible form by e.g. applying different materials in an outer protection layer of the tether and detecting the position of the orientation marking by e.g. ultrasonic waves or radar waves. The wind power device is preferably adapted to measure the rotational position of the tether, in particular based on the orientation marking, preferably in order to detect the torsional state of the tether. For this purpose, the wind power device preferably comprises at least one tether orientation sensor, which can in particular be arranged in the air interface and / or in the ground station. The measurement of the rotational position of the tether can also be used to ensure an essentially torsion-free winding up of the tether on the drum.

The air interface preferably comprises a connection element for rotatably connect the tether to the wind power station. The connection element can be fixedly attached on the wind power station. Preferably, however, in order to minimize the bending of the tether during operation, the connection element is pivotally, in particular pivotally in a plurality of or even all directions, attached to the wind power station. For this purpose, the air interface preferably comprises a gimbal for the attachment of the connection element to the wind power station. Alternatively, the air interface can comprise a dome-shaped coupling structure for attaching the connection element to the wind power station, wherein the dome shaped coupling structure preferably comprises a first shell and a second shell, the first shell being movably arranged in or on the second shell. The dome-shaped coupling structure preferably comprises a pressurised air or oil film bearing. The provision of a pressurised air or oil film bearing has the advantage that an essentially friction-free bearing between the first and second shell can be achieved.

According to a second aspect, it is an object of the present invention to provide a wind power device, which allows keeping the bending of the tether at a minimum during the operation of the wind power device.

This object is solved by a wind power device as claimed in claim 9. Further embodiments of the wind power device are provided in dependent claim 10 and 11.

Thus, according to this second aspect, the present invention provides a wind power device for converting wind energy into electric energy, in particular but not necessarily a wind power device as described above, comprising a wind power station with one or more electric power generators that are adapted to convert wind power into electric energy, when the wind power station is airborne; a ground station; and a tether for transferring the electric energy generated by the one or more electric power generators to the ground station.

The ground station comprises a drum for winding up the tether, the drum having a preferably horizontally extending longitudinal center axis.

The drum is rotatable about an axis, which extends essentially perpendicularly to the longitudinal center axis of the drum, such that, during operation, the orientation of the drum can be adapted to the direction of the tether and / or to the position of the wind power station. Preferably, the axis about which the drum is rotatable is a vertically extending axis.

By rotating the drum about an axis that extends perpendicularly to the longitudinal center axis, preferably about a vertically extending axis, during operation of the wind power device, the drum can always be optimally oriented with respect to the tether, even if e.g. permanent or cyclic position changes are carried out by the wind power station relative to the ground station. The adaptation of the orientation of the drum to the tether and / or to the position of the wind power station has the advantage that bending of the tether at the ground station can be minimized. The orientation of the drum can for example always be adjusted to the actual direction of the tether or it can be adjusted to an average position of the wind power station e.g. during its flight along circular paths and / or along a figure-8.

The preferably vertically extending axis, about which the drum is rotatable to be adapted to the direction of the tether and / or to the position of the wind power station, thus extends essentially perpendicularly to the usually horizontally extending longitudinal center axis, about which the drum is rotatable to wind up or off the tether. The vertically extending axis can, but does not need to, extend centrally or decentrally through the drum.

In order to reduce the frictional forces generated when adjusting the drum to the direction of the tether and / or to the position of the wind power station, the ground station preferably comprises bearings, in particular ball bearings and / or slide bearings, for bearing the drum on a stationary part of the ground station.

The rotations of the drum about the preferably vertically extending axis can be passive or active. The ground station can comprise at least one drive for providing active rotations, i.e. for rotating the drum about the vertically extending axis. By actively adjusting the orientation of the drum to the tether and / or the wind power station, friction-related residual misorientation of the drum can be avoided and bending of the tether during operation can be further minimized. The adjustments of the orientation of the drum by means of the drive are preferably carried out automatically by the wind power device.

According to a preferred embodiment, the ground station comprises a landing support for receiving the wind power station during landing operations and preferably for storing the wind power station when the wind power device is not in operation. In order to facilitate the landing operations and to minimize bending of the tether, the landing support is likewise rotatable about the preferably vertically extending axis of the drum, such that, during landing operations, the landing support can be oriented to the direction of the tether and / or to the position of the wind power station. The rotations of the landing support about the vertically extending axis can be passive or active. The ground station can comprise at least one drive for providing active rotations, i.e. for rotating the landing support about the vertically extending axis. The drive for rotating the drum about the vertical axis can be the same as the one for rotating the landing support.

The feature of having a drum that is rotatable about the preferably vertically extending axis is independent of the feature that an air interface is provided which enables a rotary connection between the tether and the wind power station. An embodiment of a wind power device having both features, however, is preferred, because in this case large torsional forces as well as bending are avoided with respect to the tether. For the sake of e.g. simplicity and cost-effectiveness, however, one or both of these features can well be missing in certain embodiments.

According to a third aspect, it is an object of the present invention to provide an electric / optical rotary joint which enables the coupling of a first electric and optic line with a second electric and optic line in such a way that unlimited rotations of the first electric and optic line relative to the second electric and optic line are possible.

This object is solved by an electric / optical rotary joint as claimed in claim 12. A further embodiment of the electric / optical rotary joint is provided in dependent claim 13.

Thus, according to this third aspect, the present invention provides an electric / optical rotary joint, in particular but not necessarily of or for one of the wind power devices as described above, for coupling a first electric and optic line with a second electric and optic line in such a way that unlimited rotations of the first electric and optic line relative to the second electric and optic line are enabled, the first electric and optic line and the second electric and optic line each comprising an outer electric conductor, an inner electric conductor and an optic fiber and the electric / optical rotary joint comprising an outer contact cylinder; an outer contact element which is rotatably arranged with respect to the outer contact cylinder; one or more outer contacts, in particular sliding contacts, for electrically connecting the outer contact cylinder with the outer contact element, in order to electrically couple the outer electric conductor of the first electric and optic line with the outer electric conductor of the second electric and optic line; an inner contact cylinder; an inner contact element which is rotatably arranged with respect to the inner contact cylinder; one or more inner contacts, in particular sliding contacts, for electrically connecting the inner contact cylinder with the inner contact element, in order to electrically couple the inner electric conductor of the first electric and optic line with the inner electric conductor of the second electric and optic line; and a fiber optic rotary joint for coupling the optic fiber of the first electric and optic line with the optic fiber of the second electric and optic line; wherein the outer contact cylinder radially encompasses the inner contact cylinder and the inner contact cylinder radially encompasses the fiber optic rotary joint.

Thus, by means of the electric / optical rotary joint, the outer electric conductors can be connected via the outer contact cylinder and the outer contact element, the inner electric conductors via the inner contact cylinder and the inner contact element and the optic fibers via the fiber optic rotary joint.

The roles of the outer contact cylinder and the outer contact element can of course be interchanged as well as and independently of the roles of the inner contact cylinder and the inner contact element. Thus, e.g. the outer electric conductor of the first electric line can be attached to the outer contact cylinder and the outer electric conductor of the second electric line can be attached to the outer contact element or vice versa.

The electric / optical rotary joint is preferably adapted to be used in the low- (up to 1 kV) or lower part of the medium-voltage range (1 kV to 52 kV), more preferably in the medium- (1 kV to 52 kV) or high-voltage (at least 52 kV, in particular 52 kV to 300 kV or more than 300 kV) range, especially for transferring electric power of above 1 MW. The electric / optical rotary joint is preferably adapted to establish an electric field between the outer and the inner cylinder, when in use.

The outer contact element and / or the inner contact element can for example have the form of a plate or of another cylinder. The outer contact element can be adapted to contact, via the one or more outer contacts, a surface of the outer contact cylinder, which is directed radially outwardly or inwardly. The outer contact element can also be adapted to contact both an outwardly directed surface and an inwardly directed surface of the outer contact cylinder. Likewise, the inner contact element can be adapted to contact, via the one or more inner contacts, a surface of the inner contact cylinder, which is directed radially outwardly or inwardly. The inner contact element can also be adapted to contact both an outwardly directed surface and an inwardly directed surface of the inner contact cylinder. The outer contacts can particularly be provided in the form of sliding contacts and/or rolling contacts.

The arrangements of the outer electric conductor, the inner electric conductor and the optic fiber in the first electric and optic line and in the second electric and optic line are preferably such, that in each case the outer electric conductor forms a first layer that surrounds a second layer formed by the inner electric conductor. The outer and inner electric conductors are preferably wound helically around a core of the respective electric and optic line. The core is advantageously an elastic core. The optic line is preferably arranged radially inside of the second layer formed by the inner electric conductor. If the electric and optic line comprises an elastic core, the optic line is preferably arranged centrally within the core. Each of the first and second electric and optic lines can comprise a single optic fiber or a plurality of optic fibers. The first and second electric and optic lines can particularly be designed in accordance with the specifications further above of the tether of the wind power device and more particularly as specified in WO 2016/062735 A1. Depending on the embodiment, the first and second electric and optic lines can form or be part of an electric and optic cable or of e.g. a tether used for connecting an airborne wind power station to the ground.

The first or second electric and optic line is preferably part of a cable or tether that also comprises a load-bearing layer adapted for absorbing tensile forces. In this case, the load- bearing layer is preferably fixedly attached to a holding structure or to a connection element, which advantageously is not formed by the outer contact cylinder, the outer contact element, the inner contact cylinder or the inner contact element.

The design of fiber optic rotary joints are well known to the skilled person. For the present electric / optical rotary joint, the fiber optic rotary joint can for example be constructed and designed as indicated in one of the documents US 5,157,745 A or US 8,965,151 B1.

In a preferred embodiment, the outer contact cylinder and the outer contact element define an inner space, in which the inner contact cylinder and the inner contact element are arranged. The inner contact cylinder and the inner contact element are then protected from external influences by means of the outer contact cylinder and the outer contact element. In a particularly preferred embodiment, the inner space is gas-tight with respect to the outside. A gas-tight inner space has the advantage that it can be filled with an electrically insulating gas or that a vacuum can be present, in order to reduce the necessary electric insulating distances by increasing the dielectric strength between the electrodes. The overall size of the electric / optical rotary joint can be reduced in this way.

The electric / optical rotary joint is preferably, but not necessarily, adapted to be used in or for one of the wind power devices as specified further above. If the electric / optical rotary joint is used in a wind power device, it can particularly be part of the connection element of the air interface as already mentioned above. In addition or alternatively, the electric / optical rotary joint can also be used to connect a tether or cable that is wound around a horizontally and / or vertically rotatable drum to an electric and optical cable that is attached to the drum.

Thus, the electric / optical rotary joint can be provided in a wind power device independently on the feature that an air interface is provided which enables a rotary connection between the tether and the wind power station and on the feature that the drum is rotatable about a preferably vertically extending axis, in order to be oriented to the tether and / or to the wind power station. The electric / optical rotary joint does not even have to be part of a wind power device or be suited for use in or with respect to a wind power device. An embodiment of a wind power device as indicated further above and having one or more electric / optical joints as mentioned, however, is preferred, because the electric / optical joint can particularly be used for the rotary connection of the tether to the wind power station and / or to the drum.

According to a fourth aspect, it is an object of the present invention to provide a combined high voltage and fiber optic connector unit, which has a simple construction and enables a safe coupling of electric conductors and optic fibers.

This object is solved by a combined high voltage and fiber optic connector unit as claimed in claim 14. Further embodiments of the combined high voltage and fiber optic connector unit are provided in dependent claims 15 and 16.

Thus, according to this fourth aspect, the present invention provides a combined high voltage and fiber optic connector unit, in particular but not necessarily of or for one of the wind power devices as described above, and more particularly of or for an electric / optical rotary joint as described above, comprising a female part, which comprises an electrically conducting socket and a first optic fiber extending through the socket; a male part, which is pluggable into the female part, and which comprises an electrically conducting contact body and a second optic fiber extending though the contact body; and a spring element arranged in the female part or in the male part, for pressing an end face of the first or the second optic fiber against an end face of the second or the first optic fiber, when the male part is plugged into the female part, in order to couple the first and the second optic fibers; wherein the contact body is adapted to be inserted into the socket, in order to establish an electric contact between the contact body and the socket.

By means of the combined high voltage and fiber optic connector unit, a first electric and optic line can safely be coupled to a second electric and optic line. The spring element, which preferably, but not necessarily, is in the form of a coil spring, serves to safely and reliably connect the optic fibers with each other. Owing to the spring element, the end faces of the optic fibers even abut each other in the presence of external mechanical influences, such as vibrations or similar. The first and second optic fibers preferably both extend centrally trough the socket and the contact body, respectively.

The male part of the high voltage and fiber optic connector unit preferably comprises a deflector for electric field control in an area where the high voltage and fiber optic connector unit is attached on a connector element, such as an electrically conducting plate or housing. The deflector is preferably made of a semi-conductive material. The deflector can particularly have the form of a funnel that widens towards the female part. In the direction towards the female part, an electric field with approximately radial field lines is preferably first established between the deflector and the electric conductor of e.g. an electric and optic line. In the direction towards the female part, the electric field preferably radially widens and the extension of the field lines continually changes from a radial to a more longitudinal direction. At the end of the deflector, the field lines preferably extend approximately along the longitudinal direction between the deflector and the socket or between the socket and a further electrically conducting element, such as a high-voltage shield, that is attached to the socket.

The part of the male part or of the female part, in which the spring element is arranged, preferably comprises a widened inner space for receiving an extra length portion of the first or second optic fiber. The extra length portion is preferably received in the widened inner space in the form of one or several windings. The provision of the widened inner space for receiving an extra length portion of the first or second optic fiber has the advantage that no axial tension is applied to the respective optic fiber by the spring element, neither in the coupled nor in the uncoupled state of the male and female parts. Furthermore, the assembly of the high voltage and fiber optic connector unit can be facilitated substantially in this way.

The female part preferably comprises a first fiber centering tube encompassing the first optic fiber in the region of its end face, and the male part preferably comprises a second fiber centering tube encompassing the second optic fiber in the region of its end face. The first and the second fiber centering tubes are advantageously arranged coaxially behind each other and are preferably abutting each other, when the male part is plugged into the female part. By means of the first and second fiber centering tubes, precise alignment and close abutment of the optic fibers can be ensured, in order to guarantee safe and reliable signal transmission. A precise alignment of the optic fibers can particularly be achieved, if the first and second fiber centering tubes and in particular their abutting ends are arranged within a common further centering tube, the inner diameter of which is preferably approximately the same or even slightly smaller than the outer diameter of each of the first and second fiber centering tubes.

For further improving the connection between the optic fibers, the end faces of the optic fibers can have complementary formed surface structures, in particular crown-shaped surface structures.

In order to ensure a safe connection of one or more electric conductors of e.g. an electric and optic line to the combined high voltage and fiber optic connector unit, the male part preferably additionally comprises a clamping cone with a conical outer surface and the contact body comprises a conical inner surface. In such an embodiment, the clamping cone is preferably adapted to be inserted into the contact body in such a way that the clamping cone is pressed against the one or several electric conductors owing to the mutual engagement of the conical inner and outer surfaces. By preferably even crimping the one or several electric conductors between the clamping cone and the contact body, a particularly safe connection can be achieved.

The combined high voltage and fiber optic connector unit is preferably, but not necessarily, adapted to be used in or for one of the wind power devices as specified further above, and more particularly as a part of the connection element of the air interface as already mentioned above and most particularly adapted to be used in or for the electric / optical rotary joint as specified above. In addition or alternatively to the use in combination with the air interface, the combined high voltage and fiber optic connector unit can also be used to connect a tether or cable to a horizontally and / or vertically rotatable drum. If the combined high voltage and fiber optic connector unit is used in or for the electric / optical rotary joint as mentioned above, the connector element to which the combined high voltage and fiber optic connector unit is attached or is adapted to be attached is preferably formed by the outer contact element or the outer contact cylinder of the electric / optical rotary joint.

Thus, the combined high voltage and fiber optic connector unit can be provided in a wind power device independently on the feature that an air interface is provided which enables a rotary connection between the tether and the wind power station and independently on the feature that the drum is rotatable about a preferably vertically extending axis, in order to be oriented to the tether and / or to the wind power station. The combined high voltage and fiber optic connector unit does not even have to be part of a wind power device or be suited for use in or with respect to a wind power device. An embodiment of a wind power device as indicated further above and having one or more electric / optical joints as mentioned, however, is preferred, because the combined high voltage and fiber optic connector unit can particularly be used for the coupling of the tether to an electric / optical rotary joint of the wind power device. Thus, the combined high voltage and fiber optic connector unit is preferably a part of or used in combination with an electric / optical rotary joint as indicated.

According to a fifth aspect, it is an object of the present invention to provide a coupling structure for coupling an electric and / or optical cable to a connection element, which is able to withstand large tensile forces.

This object is solved by a coupling structure as claimed in claim 17. Further embodiments of the coupling structure are provided in dependent claims 18 to 21 .

Thus, according to this fifth aspect, the present invention provides a coupling structure, in particular but not necessarily of or for one of the wind power devices as described above, and more particularly adapted for use in combination with an electric / optical rotary joint as described above, comprising a connection element, which preferably comprises the electric / optical rotary joint as described above; and an electric and / or optical cable coupled to the connection element and having an inner electric / optic line with an electric conductor and / or an optic fiber as well as an outer load-bearing layer for absorbing axial, i.e. tensile, loads, the load-bearing layer extending concentrically with respect to the electric / optic line.

At least one component of the load-bearing layer has an end part which, along the longitudinal direction of the electric and / or optical cable towards the connection element, is radially guided away from the electric / optic line, in order to be fixedly attached to the connection element at an increased radial distance from the electric / optic line which is guided radially inside of the end part of the load-bearing layer into the connection element.

By radially guiding the at least one component of the load-bearing layer away from the electric / optic line, the load-bearing layer can be attached in a particularly firm way to the connection element, because in this way, more space for attaching the load-bearing layer is gained, without affecting the electric / optic line. Thus, the attachment of the load-bearing layer to the connection element can particularly be effected distantly from the electric / optic line. Advantageously, the attachment of the load-bearing layer, in particular of the at least one component, to the connection element spatially surrounds the electric / optic line, in order to achieve a homogeneous distribution of the tensile forces in the coupling structure. The electric / optic line, i.e. at least the electric conductors and / or optic fibers of the cable, can extend further to or into the connection element and optionally be coupled to e.g. another electric / optic line, for example via an electric / optical rotary joint as specified above, at or within the connection element.

Furthermore, by radially guiding at least one component of the load-bearing layer away from the electric / optic line, the density of the components constituting the load-bearing layer, e.g. strands or filaments, usually decreases with increasing distance to the electric / optic line. As a result, the attachment of the load-bearing layer to the connection element can be carried out in a much firmer and more effective way. Thus, the at least one component of the load-bearing layer that has an end part, which is radially guided away from the electric / optic line towards the connection element, can particularly be formed by strands and/or filaments.

The electric and / or optical cable can particularly be designed in accordance with the specifications of the electric and optic lines and / or of the tether further above. More particularly, the electric and / or optical cable can be designed as specified in WO 2016/062735 A1.

In a preferred embodiment, the coupling structure additionally comprises a first clamp and a second clamp, which are fixedly attached to the connection element and serve for clamping the load-bearing layer, in particular the at least one component of the load-bearing layer. By radially guiding away the end part of the component of the load-bearing layer from the electric / optic line, clamping of the load-bearing layer without affecting the electric / optic line becomes possible. Preferably, the second clamp is adapted to clamp the load- bearing layer in a radially inward direction and the first clamp is adapted to clamp the load- bearing layer in a radially outward direction. Thus, the first clamp is preferably radially arranged between the electric / optic line and the load-bearing layer, in particular the at least one component of the load-bearing layer. The first clamp advantageously also serves to guide the electric / optic line. For this purpose, the first clamp advantageously comprises a longitudinal through-opening for receiving the electric / optic line. The first clamp preferably has a conical outer surface, which allows achieving an optimized and preferably constant increase of the clamping force along the length of the load-bearing layer towards the connection element. In the longitudinal direction away from the connection element, the second clamp preferably conically widens up, in order to allow certain lateral movements of the electric and / or optical cable with respect to the connection element.

In another, also preferred embodiment, the first clamp and the second clamp have meander-shaped clamping surfaces for clamping the load-bearing layer or the at least one component of the load-bearing layer in-between. By the provision of the meander-shaped clamping surfaces, a particularly large effective clamping surface can be achieved in a comparatively small space. Preferably, each of the meander-shaped clamping surfaces as a whole extend perpendicularly to the longitudinal direction of the electric / optic line. The clamping is advantageously effected by the meander flanks, but not or to a much lesser degree by the bottom and top faces between the flanks. In this way, a better fine adjustment of the clamping force over a certain clamp distance can be achieved.

In yet another, also preferred embodiment, the end part of the load-bearing layer or of the at least one component of the load-bearing layer forms a plurality of slings, in particular spliced slings, which e.g. extend around sling bolts that are attached to the connection element. The plurality of slings allows an attachment of the electric and / or optical cable on the connection element, which is particularly safe and reliable. The coupling structure is preferably, but not necessarily, adapted to be used in or for one of the wind power devices as specified further above, and more particularly for attaching the load-bearing layer of the tether to the connection element of the air interface as already mentioned above. In addition or alternatively to the use in combination with the air interface, the coupling structure can e.g. also be used to connect a tether or cable to a horizontally and / or vertically rotatable drum.

The coupling structure, however, can be provided in a wind power device independently on the feature that an air interface is provided which enables a rotary connection between the tether and the wind power station and independently on the feature that the drum is rotatable about a preferably vertically extending axis, in order to be oriented to the tether and / or to the wind power station. The coupling structure can also be advantageous in wind power devices that have a tether which is not rotatable with respect to the wind power station and / or that have a ground station with a drum that is not rotatable about a vertical axis. The coupling structure does not even have to be part of a wind power device or be suited for use in or with respect to a wind power device. It can be used for any other applications in which an electric and / or optical cable, that has to withstand certain tensile forces, needs to be coupled to a connection element. The coupling structure can of course also be used independently on the presence of a combined high voltage and fiber optic connector unit as described above as well as on the presence of an electric / optical rotary joint as indicated above. The combination of the coupling structure with an electric / optical rotary joint and with the combined high voltage and fiber optic connector unit, however, is particularly preferred for the connection of a tether in an air interface of a wind power device as indicated.

According to a sixth aspect, it is an object of the present invention to provide a wind power device that is well protected from lightning. The influence of the lightning protection system to the operation of the wind power device should be minimal.

This object is solved by a wind power device as claimed in claim 22.

Thus, according to this sixth aspect, the present invention provides a wind power device for converting wind energy into electric energy, in particular but not necessarily one of the wind power devices as described above, comprising a wind power station with one or more electric power generators that are adapted to convert wind power into electric energy, when the wind power station is airborne; a ground station with a lightning rod for protecting the wind power device from lightning; and a tether for transferring the electric energy generated by the one or more electric power generators to the ground station.

The lightning rod is retractable, in particular by a motor and preferably automatically, in order to not interfere with the wind power station or with the tether during landing and launching operations.

By designing the lightning rod of the ground station to be retractable, the lightning rod can be retracted at least during landing and launching operations, preferably at all times when the wind power station is airborne, in order to not interfere with the wind power station and / or with the tether. After the wind power station has landed and is in its storing position, i.e. during times when the wind power device is not in operation, the lightning rod can be extended, in order to protect the ground station and the wind power station from lightning. In order to be retractable, the lightning rod preferably has a telescopic design.

Several lightning rods can be provided, in order to have at least one lightning rod to be able to be extended, when the others are blocked by the landed wind power station.

A retractable lightning rod can be provided independently on the feature that the wind power station is rotatably connected to the tether and also independently on the feature that the drum of the ground station is rotatable about a preferably vertical axis. The idea of a retractable lightning rod is also independent on the electric / optical rotary joint, on the combined high voltage and fiber optic connector unit and on the coupling structure as indicated above. A combination of all of these ideas, however, is preferred, because in this way a wind power device can be achieved that allows an efficient generation of electric energy in the medium or high voltage-range.

According to a seventh aspect, it is an object of the present invention to provide an electric cable, which is adapted for a particularly high number of bending cycles.

This object is solved by an electric cable as claimed in claim 23. A further embodiment of the electric cable is provided in dependent claim 24. Thus, according to this seventh aspect, the present invention provides an electric cable, in particular a high voltage cable, in particular but not necessarily of or for one of the wind power devices as described above, comprising an elastic core; and at least one layer of one or more electric conductors helically wound around the elastic core.

One or more longitudinal elastic buffers are provided between the helical windings of the one or more electric conductors, in order to prevent direct contact of the windings of the one or more electric conductors.

In other words, the one or more longitudinal elastic buffers form a double helix with the one or more electric conductors in such a way that the windings of the one or more electric conductors do not directly contact each other. In this way, fretting between the windings of the one or more electric conductors lying next to each other under e.g. cyclic movements can be prevented effectively. The longitudinal elastic buffers are preferably formed by one or more strands. The friction between the surfaces of the longitudinal elastic buffers and of the electric conductors is preferably smaller, in particular by a multiple smaller, than the friction of the electric conductors on themselves.

In a preferred embodiment, at least two layers of one or more helically wound electric conductors are provided. The provision of more than one layer of helically wound electric conductors is particularly well suited for the transmission of electric energy in the medium or high voltage-range. In this case, the arrangement of a low friction layer between each pair of adjacent layers of electric conductors is preferred, in order to avoid fretting between the layers of electric conductors. The friction between the surfaces of the low friction layer and of the electric conductors is preferably smaller, in particular by a multiple smaller, than the friction between the layers of the electric conductors on themselves.

The electric cable is preferably, but not necessarily, adapted to be used in or for a wind power device as indicated above. The electric cable can particularly form a tether or at least a part of the electric line that connects an airborne wind power station to the ground. The electric cable as mentioned, however, can be provided independently on the feature that the wind power station is rotatably connected to the tether and also independently on the feature that the drum of the ground station is rotatable about a preferably vertical axis. A combination of the electric cable with the rotatable connection of the wind power station to the tether and / or with the rotatability of the ground station about a preferably vertical axis, however, is preferred, because in this way a wind power device can be achieved that allows an efficient generation of electric energy in the medium or high voltage-range.

SHORT DESCRIPTION OF THE FIGURES

Preferred embodiments of the invention are described in the following with reference to the drawings, which only serve for illustration purposes, but have no limiting effects. In the drawings, it is shown:

Fig. 1 a partial cross-sectional view of a ground station and a wind power station, in air, according to an inventive embodiment;

Fig. 2 a partial cross-sectional view of the ground station and the wind power station of fig. 1, landed;

Fig. 3 a partial cross-sectional view of a ground station with a wind power station on an offshore platform, landed, according to another inventive embodiment;

Fig. 4a a partial cross-sectional view of the air interface between the tether and the wind power station of fig. 1 ;

Fig. 4b a perspective view of the air interface of fig. 4a;

Fig. 4c a perspective view of a variant of the air interface;

Fig. 5a a partial cross-sectional view of another embodiment of the air interface;

Fig. 5b a side view of the inner shell of the air interface of fig. 5a;

Fig. 5c a cross-sectional detail view of one of the rolling ball bearings of the air interface of fig. 5a;

Fig. 5d a cross-sectional detail view of a part of the dome-shaped coupling structure of a variant of the air interface of fig. 5a;

Fig. 6 a longitudinal cross-sectional view of the rotary joint cylinder and of the low flection termination of the air interface of fig. 4a;

Fig. 7 a more detailed longitudinal cross-sectional view of the rotary joint cylinder of fig. 6;

Fig. 8a a partial longitudinal cross-sectional view of the low flection termination combined with a sling system, of the air interface of fig. 4a;

Fig. 8b a transverse cross-sectional view of the low flection termination of fig. 8a according to a first variant;

Fig. 8c a transverse cross-sectional view of the low flection termination of fig_. 8a according to a second variant; Fig. 9a a folded-up cross-sectional view of the low flection termination combined with a sling system, of the air interface of fig. 4a;

Fig. 9b a more detailed view of the low flection termination of fig. 9a;

Fig. 10 a partial cross-sectional view of the low flection termination combined with a meander clamp system, of the air interface of fig. 4a;

Fig. 11 a longitudinal cross-sectional view of the electric / optical rotary joint 700 of the rotary joint cylinder of fig. 7;

Fig. 12 a longitudinal cross-sectional view of one of the combined high voltage and fiber optic connectors 701 of the electric / optical rotary joint of fig. 11 , in the coupled state;

Fig. 13 a longitudinal cross-sectional view of the connector element 764 of the combined high voltage and fiber optic connector of fig. 12;

Fig. 14 a longitudinal cross-sectional view of the fiber optic connector unit 810 of the connector element 810 of fig. 13;

Fig. 15a a longitudinal cross-sectional view of a variant of a fiber optic connector unit of the connector element 810 of fig. 13;

Fig. 15b a transverse cross-sectional view of the fiber optic connector unit of fig. 15a;

Fig. 16 a longitudinal cross-sectional view of one of the combined high voltage and fiber optic connectors 701 of the electric / optical rotary joint of fig. 11, in the decoupled state;

Fig. 17 a longitudinal cross-sectional view of a part of the combined high voltage and fiber optic connector of fig. 12;

Fig. 18 a longitudinal cross-sectional view of the high voltage and fiber optic rotary joint 702 of the electric / optical rotary joint of fig. 11 , in coupled state;

Fig. 19 a longitudinal cross-sectional view of a variant of the high voltage and fiber optic rotary joint 702 of the electric / optical rotary joint of fig. 11 , in coupled state;

Fig. 20a a detailed cross-sectional view of one of the sliding contacts of the high voltage and fiber optic rotary joint 702 of fig. 18, according to a first variant;

Fig. 20b1 a detailed cross-sectional view of one of the sliding contacts of the high voltage and fiber optic rotary joint 702 of fig. 18, according to a second variant;

Fig. 20b2 a detailed cross-sectional view of two of the sliding contacts of the high voltage and fiber optic rotary joint 702 of fig. 18, according to a third variant;

Fig. 20c a detailed cross-sectional view of two of the sliding contacts of the high voltage and fiber optic rotary joint 702 of fig. 18, according to a fourth variant;

Fig. 21 a1 a detailed cross-sectional view of one of the sliding contacts of the high voltage and fiber optic rotary joint 702 of fig. 18, according to a fifth variant; Fig. 21 a2 a detailed cross-sectional view of one of the sliding contacts of the high voltage and fiber optic rotary joint 702 of fig. 18, according to a sixth variant

Fig. 21 a3 a detailed cross-sectional view of one of the sliding contacts of the high voltage and fiber optic rotary joint 702 of fig. 18, according to a seventh variant

Fig. 21b a detailed cross-sectional view of one of the sliding contacts of the high voltage and fiber optic rotary joint 702 of fig. 18, according to a eighth variant

Fig. 21c a detailed cross-sectional view of two of the sliding contacts of the high voltage and fiber optic rotary joint 702 of fig. 18, according to a ninth variant

Fig. 22 a longitudinal cross-sectional view of the high voltage and fiber optic rotary joint 702 of fig. 18, in decoupled state;

Fig. 23a a cross-sectional view of the combined optic and electric power interface 851 of the wind power station of fig. 1 ;

Fig. 23b a cross-sectional view of the contact pin 865 of the combined optic and electric power interface of fig. 23a;

Fig. 24 a longitudinal cross-sectional view of the high voltage connector 852 of the combined optic and electric power interface of fig. 23a;

Fig. 25a a side view of the high voltage cable 850 of the air interface of figures 4a to 4c;

Fig. 25b a longitudinal cross-sectional view of another embodiment of a high voltage cable 850;

Fig. 26 a top view of the guiding and adjusting system 330, of parts of the landing support 300, of the tether guiding system 400 and of the drum 200 of the ground station 1 of fig. 1 ;

Fig. 27a a detailed front view of the guiding and adjusting system 330 of fig. 26, according to a first embodiment;

Fig. 27b a detailed front view of the guiding and adjusting system 330 of fig. 26, according to a second embodiment;

Fig. 27c a detailed cross-sectional view of one of the distance sensors 337 of the guiding and adjusting system 330 of fig. 26;

Fig. 27d a detailed cross-sectional view of the guiding and adjusting system 330 of fig. 26, with a possible arrangement of the distance sensors 337;

Fig. 28 a cross-sectional view of the drum 200 and the tether guiding system 400 of the ground station of fig. 1;

Fig. 29 (top) a perspective view of the tether 500 of the wind power device of fig. 1 , with a first variant of a tether orientation marking;

Fig. 29a 1 a transverse cross-sectional view of the tether, with a second variant of a tether orientation marking; Fig. 29b2 a transverse cross-sectional view of the tether, with a third variant of a tether orientation marking; Fig. 29c1 a transverse cross-sectional view of the tether, with a fourth variant of a tether orientation marking; Fig. 29d1 a transverse cross-sectional view of the tether, with a fifth variant of a tether orientation marking; Fig. 30 a cross-sectional view of the position- and torsion-sensing unit 423 of the tether guiding system 400 of fig. 28; Fig. 31 a longitudinal cross-sectional view of a rotation unit 405' of the tether guiding system of fig. 28, according to a first embodiment - with adjustable roller pressure;

Fig. 32 a more detailed longitudinal cross-sectional view of the rotation unit 405' of fig. 31 and in particular of the adjustment cylinder 431 ; Fig. 33 a longitudinal cross-sectional view of a rotation unit 405" of the tether guiding system of fig. 28, according to a second embodiment; Fig. 34 a partial longitudinal cross-sectional view of the tether-cleaning unit 467 of the rotation unit 405" of fig. 33; Fig. 35a a cross-sectional view of one of the grip rollers 427 and associated components of the grip roller system 435 of the rotation unit 405" of fig. 33; Fig. 35b a cross-sectional view of one of the grip belt wheels 458 and associated components of the grip belt system 476 of the rotation unit 405' of fig. 31 ; Fig. 35c1 a cross-sectional view of a first variant of a possible arrangement of the grip rollers 427; Fig. 35c2 a cross-sectional view of a second variant of a possible arrangement of the grip rollers 427'; Fig. 35c3 a cross-sectional view of a third variant of a possible arrangement of the grip rollers 427"; Fig. 35d a cross-sectional view of a fourth variant of a possible arrangement of the roller bodies 429' of the grip rollers 427'"; Fig. 36 a side view of the tether guiding system 400 with the linear unit 404 of the ground station of fig. 2; Fig. 37a a detailed cross-sectional view of the linear unit 404 and of the tether guiding system 400 of fig. 36; Fig. 37b a detailed partial cross-sectional view of the height adjustment unit 495 of the linear unit 404 of fig. 36; Fig. 37c a top view of the tether guiding system 400 and the drum 200 of the ground station of fig. 2;

Fig. 38a1 a partial longitudinal cross-sectional view of the drum 200 according to a first embodiment;

Fig. 38a2 a partial longitudinal cross-sectional view of the drum 200 according to a second embodiment;

Fig. 38a3 a partial longitudinal cross-sectional view of the drum 200 according to a third embodiment;

Fig. 38b a transverse cross-sectional view of the ground interface 250 of the ground station of fig. 1 ;

Fig. 38c a cross-sectional view of the low flection termination 630 of the ground interface 250 of fig. 38b; and

Fig. 39 a longitudinal cross-sectional view of the rotary joint 100 of the ground station of fig. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, elements associated to the same embodiment or to different embodiments and having an identical or similar function are designated with the same reference numerals, possibly added by one or more apostrophes, in each case.

Figure 1 - Overview of the ground station and the wind power station, in air

Figure 1 shows an overview of an airborne wind power station 600 connected to a ground station 1 by means of a tether 500. The wind power station 600 can also be referred to as a flying apparatus. The wind power station 600, the tether 500 and the ground station 1 together form a wind power device for converting wind energy into electric energy. An air interface 610 between the tether 500 and the wind power station 600 and a ground interface 250 between the tether 500 and the ground station 1 are provided. The wind power station 600 generates electric energy when deployed at typical flight heights. Typical flight heights of the wind power station 600 for e.g. the energy production with low-level jet streams are 700 to 1500m over ground. However, in certain embodiments, the wind power station 600 can also be adapted to be applied at lower wind speeds and in less constant wind situations at e.g. 300 to 700m over ground. For generating the electric energy, the wind power station 600 comprises one or more electric power generators 601 , which are adapted to convert wind power of the apparent wind acting on the wind power station 600 into electric energy. The electric power generators 601 can particularly comprise a propeller in each case and be attached to a fuselage and / or an airfoil of the wind power station 600.

The electric energy is transferred from the wind power station 600 to the ground station 1 by means of the tether 500. The tether 500 provides mechanical, electrical and / or fiber optic connection between the wind power station 600 and the ground station 1. In order to minimize the bending and torsion loads acting on the tether 500 and to provide proper winding of the tether onto and from a drum 200 of the ground station 1, the tether 500 is guided by a tether guiding system 400. The air interface 610 provides mechanical, electrical and fiber optic connection between the tether 500 and the wind power station 600. The ground interface 250 provides mechanical, electrical and fiber optic connection between the tether 500 and the ground station 1. The rotatable drum 200 enables storage of the tether 500 and provides uncoiling and coiling capabilities for the tether 500 during rising and lowering of the wind power station 600. The drum 200 is also adapted to transfer the tension load of the tether 500 to a base structure 10 of the ground station 1.

From the ground interface 250 and the drum 200, the energy and data signals carried by an electric / optic system 510 of the tether 500 are transferred to a rotary table 50 of the ground station 1 by means of an electric / optical rotary joint 700. In order to adapt the orientation of the drum 200 and of the tether guiding system 400 to the direction of the tether 500 and to the position of the wind power station 600 in operation given by the present wind direction, the drum 200 together with the tether guiding system 400 are mounted on a revolving rotary table 50 with unlimited rotational capabilities. This alignment of the revolving rotary table 50 together with the drum 200 and with the tether guiding system 400 to the actual operational position of the wind power station 600 allows to avoid the need for a guiding wheel for redirecting the tether to the coiling direction of the drum and, therefore, helps to minimize bending fatigue of the tether 500. The guiding of the tether 500 for the uncoiling and coiling process on the drum 200 is carried out by means of the tether guiding system 400, which leads to a much larger bending radius than it is possible with a redirecting guiding wheel. In a particularly preferred embodiment of the wind power device, the minimal bending radius of the tether 500 during normal use of the device is defined by the outer diameter of the drum 200.

The energy and data signals of the tether 500 as well as possible auxiliary power and data signals associated to auxiliary motors and sensors installed on the drum 200, the tether guiding system 400, the rotary table 50 and / or a landing support 300 are transferred from the rotating rotary table 50 to an energy and signal interface 20 by means of a rotary joint 100 of the ground station 1. The rotary table 50 is supported by the base structure 10.

In operation, the wind power station 600 preferably flies crosswind, typically in circular paths or figure-8 paths, which leads to substantially varying tension forces acting on the tether 500. In order to adapt the function of the air interface 610 optimally to the function of the tether guiding system 400 in combination with the optimization of the rotational position of the rotary table 50, the flight direction, position and velocity of the wind power station 600 is measured by an on-board position, direction and velocity measuring system 605, which can e.g. comprise an inertial system, and transferred to the ground station 1. This can be achieved by applying measured data of e.g. a global positioning system (such as the NAVSTAR GPS), and / or differential GPS, and / or inertial navigation system (INS). Also partially ground-based methods, such as radar, for the determination of the position, direction and velocity of the wind power station 600 can be applied. An optimal rotational position is achieved, when the rotational axis of the drum and the axial direction of the tether 500 close to the ground station are perpendicular to each other.

To support the wind power station 600 for parking as well as for the starting and landing phase, a landing support 300 is provided, which can be positioned optimally in relation to the drum 200 and to the actual wind direction by means of circular tracks 301. For this manoeuvre, the entire landing support 300 can be rotated around the rotational axis of the rotary table 50. The wind direction and wind speed at the ground station 1 is preferably measured by a wind measurement system 401 of the ground station 1. Dependent on the actual rotational position of the rotary table 50 and of the tether 500, the landing support 300 is positioned in a way not to interfere with the tether 500 and the wind power station 600.

To protect the ground station 1 as well as the wind power station 600 in the landed state placed on the landing support 300 from lightnings, a lightning rod 290 is provided. The lightning rod 290 is connected to an earthing system 291 of the ground station 1. In order to prevent collision with the moving parts of the wind power station 600, the tether 500 and the landing support 300, the lightning rod 290 has a telescopic design, in order to be retractable. In figure 1 , the lightning protection rod 290 is shown in its retracted state, since the wind power station 600 is not in the landed position. To avoid a situation in which the position of the lightning rod 290 and the rotational position of the landing support 300 for an optimal parking position of the wind power station 600 under heavy wind conditions interfere, a second lightning rod 290 can optionally be provided, e.g. on the opposite site of the rotary table 50.

Figure 2 - Overview of the ground station and the wind power station, landed

Figure 2 shows an overview of the wind power station 600 connected to the ground station 1 by means of the tether 500, with the wind power station 600 in its landing position, i.e. parked on the landing support 300. For connecting the tether 500 to the drum 200 of the ground station 1 , the tether 500 comprises a low flection termination 630.

For the correct positioning of the wind power station 600 on the landing support 300, the landing manoeuvre is carried out with the help of a guiding and adjusting system 330. For this purpose, the guiding and adjusting system 330 is adapted to measure the position of the tether 500 with respect to both the decoiling and the actual wind direction, to calculate the necessary adjustments for bringing the wind power station 600 to its landing position and to provide this information to a wind power station steering unit. Based on this information, the wind power station steering unit controls a steering system of the landing support 300 to optimally position the rotary table 50 and the landing support 300 with respect to the wind power station 600 in such a way that minimal bending loads are acting on the tether 500 during the landing process.

The wind power station steering unit can be located in the fuselage 606 of the wind power station 600, at the ground station 1 or in another part of the wind power station 600. The steering signals are preferably transferred by optical fibers, electrical cables or wireless transmission.

The rotary table 50 comprises a rotary cylinder 51 and a carrier plate 210. A drum support 226, which is fixed on the carrier plate 210, serves to support axial bearings of the drum 200.

The landing support 300 comprises a main frame 350, the guiding and adjusting system 330 and a landing support base 313. The guiding and adjusting system 330 is held in place on the main frame 350 by a beam support 331. Together with a back frame 351 , the main frame 350 is adapted to carry the wind power station 600 in its landing position.

For positioning the landing support 300 relative to the rotary table 50, a landing support drive 306 is provided, which is mounted on the carrier plate 210. For this purpose, the landing support drive 306 comprises a drive gear 302. The drive gear 302 engages with a toothed ring 321 , which is mounted on a rotary plate 320. The rotary plate 320 has a rotational axis, which coincides with the one of the rotary cylinder 51. Towards the rotary cylinder 51, a bearing 304 is attached on a radial inner surface of the rotary plate 320. The bearing 304 is in contact with the rotary cylinder 51 in such a way, that the rotary plate 320 and the rotary cylinder 51 can still be rotated with low friction and independently with respect to each other.

Fixedly connected to the rotary plate 320 is the landing support base 313, which has wheels 305, in order to roll in and along circular tracks 301. A plurality of concentric circular tracks 301 can be provided, as shown in figure 2 with two concentric circular tracks 301. The circular track 301, which is arranged closer to the rotational center, is fixed on a rail foundation 307. The circular track 301 , which is arranged farther from the rotational center, is fixed on a tilt protection foundation 310.

Lifting forces acting on the wind power station 600 and on the landing support 300 caused by strong wind conditions are absorbed by a tilt protection support 311 , a tilt protection wheel 312 and the tilt protection foundation 310, which together prevent a lifting up of the landing support 300. Alternative and / or additional provisions are possible, in order to fixate the wind power station 600 in the landed position to the landing support 300, such as automated fixation clamps, which provide firm mechanical connections as soon as the wind power station 600 has landed. The tilt protection wheel 312 enables a low friction rotation of the landing support 300 around the center axis.

The tether guiding system 400 comprises a rotation unit 405 and a linear unit 404. The rotation unit 405 serves to guide the tether tangentially to the drum for the uncoiling and coiling processes as well as for possible adjustments with regard to an active torsion prevention. Furthermore, the rotation unit 405 keeps the part of the tether 500 between the tether guiding system 400 and the drum 200 in a straight, orthogonal position to the rotation axis of the drum 200 when the wind power station 600 flies crosswind, e.g. in a circular path.

The rotary cylinder 51 runs on bearings, which are mounted to the base structure 10. These bearings can for example include a cylinder bearing 35 and preferably an axial stiffness bearing 33. In another preferred embodiment, the bearing of the rotary cylinder 51 comprises a ball bearing 36 and preferably an axial stiffness bearing 33. A rotary cylinder drive 30, e.g. an electric motor, possibly equipped with a rotary encoder, serves to adjust the rotary position of the rotary cylinder 51 together with all the parts attached thereto, such as the drum 200 and the tether guiding system 400. The rotary cylinder drive 30 is fixedly attached on the base structure 10 and drives, via a drive gear 31, a toothed ring 32, which is fixed on the rotary cylinder 51.

The rotary joint 100 comprises a casing, which is fixed to the base structure 10 with the help of a rotary joint fixation 101.

Auxiliary supply and feedback cables 27 as well as the electric / optic system 510 coming from the rotary joint 100 are guided into various interface units for the connection to an electric grid or a central steering unit. The electric / optic system 510 is connected to a combined optic and electric power interface 851 , in order to split up optic signal transmission and electric power transmission. The electric power may then be adapted to the required voltage level and shape by an energy converter 21 and transferred to the electric grid by an energy cable 23.

Auxiliary energy supply for drives, sensors and steering units is generated by an auxiliary supply interface 22. Depending on the operational state of the wind power station 600, the auxiliary energy supply source can be in the form of an external unit, which is connected to the ground station 1 via an auxiliary supply cable 24. Alternatively or additionally, the auxiliary energy supply can also be provided by the wind power station 600 via the energy converter 21.

The ground station 1 and all connected equipment, such as the wind power station 600, can be controlled via a central control unit and communication interface 26 receiving its signals and data from an external unit via a control and communication cable 25. The control and communication signals can then be transferred from the central control unit and communication interface 26 to the combined optic and electric power interface 851 for further fiber optic distribution to the wind power system. Additionally or alternatively, the wind power station 600 can also be used to send and / or receive wireless data signals for communication and / or broadcast purposes using its elevated position. If sending and / or receiving wireless data is the main or only purpose, the more general term "flying apparatus" would be more adequate for the wind power station 600. In figure 2, the already mentioned lightning rod 290 is shown in its almost entirely extended state, risen above the other parts of the entire installation, in order to protect against lightning strikes. When the wind power station 600 is in its landed state, the lightning rod 290 can be extended to its full height, e.g. by a pneumatic or hydraulic system which extends the different telescopic elements to the required height. Alternatively, the lightning rod 290 can have a flexible shaft for retracting the lightning rod 290, in order to not interfere with the wind power station (600) or with the tether (500) during landing and launching operations.

Figure 3 - Ground station with wind power station on an offshore platform

Figure 3 shows an alternative embodiment, which differs from the one of figures 1 and 2 by the design and installation of the ground station 1' as an offshore platform 60. For this purpose, the base structure 10' is designed as a whole as a floating buoy. For fixing the base structure 10' to the ground, the base structure 10' can comprise sidewall-mooring connectors 61 , a bottom-mooring connector 62 as well as respective mooring ropes 70 and mooring rope connections 71. For stabilising purposes, a stabilising ballast 65 can be provided in the region of the bottom of the base structure 10'.

In the embodiment shown in figure 3, the lightning rod 290 is attached directly to the base structure 10', and the earthing system 291 is connected to an offshore earth connection 293.

For supporting the landing support 300, an auxiliary support 295 can be attached to the underside of the landing support base 313'. Inner and outer tilt protection wheels 305' and 312' that are attached to the auxiliary support 295 have wheel axles 296 that are arranged obliquely to the center axis of the base structure 10'. The tilt protection wheels 305', 312' run in and along a tilted support rail 297, which circumferentially extends around the sidewall of the base structure 10'.

Figure 4a - Overview of the air interface between the tether and the wind power station

Figure 4a shows an overview of the air interface 610 mounted on the wind power station 600 and providing a hinged and rotatable connection between the tether 500 and the wind power station 600. The air interface 610 serves to transfer mechanical forces, electric energy as well as electric and fiber optic signals. The air interface 610 comprises a low flection termination 630, a rotary joint cylinder 660, a longitudinal suspension 612, a transverse suspension 611 and a high voltage cable 850.

The low flection termination 630 is journaled at the rotary joint cylinder 660 and provides a low fatigue mechanical load transfer between the tether 500 and the rotary joint cylinder 660.

The rotary joint cylinder 660 is a connection element that provides an unlimited mechanical, electrical and fiber optic rotational connection between the low flection termination 630 and the part of the rotary joint cylinder 660, which is directly mounted to the longitudinal suspension 612.

The part of the rotary joint cylinder 660 facing the wind power station 600 is suspended by means of a suspension ring 677 at the longitudinal suspension 612 via a pivot bearing. The longitudinal suspension 612 is suspended at the transverse suspension 611. The longitudinal suspension 612 allows the rotary joint cylinder 660 to move along the flight direction of the wind power station 600. The transverse suspension 611 allows the rotary joint cylinder 660 to move along the span direction, i.e. perpendicular to the flight direction, of the wind power station 600. The combination of the two suspension elements 612 and 611 allows the wind power station 600 to change its position relative to the direction of the tether 500 when flying crosswind for generating electric energy, or for take-off and landing operations, while avoiding bending of the tether 500 at the tether interface to the wind power station 600.

The high voltage cable 850 provides the electrical and fiber optic connection of the part of the rotary joint cylinder 660 facing the wind power station 600 to the wind power station 600 via a combined high voltage and fiber optic connector 701.

In order to reduce the wind resistance of the air interface 610, a windshield 900 is provided surrounding the internal parts 630, 660, 612, 611, 677 and 850 of the air interface 610. A cross-section of the windshield 900 is shown in figure 4a. The windshield 900 features a streamlined form and adapts to the changes in angle between the axial direction of the tether 500 and the wind power station 600 by means of suspended shells.

Between the windshield 900 and the low flection termination 630, a glide connection 950 is provided, in order to provide free rotational movement of the low flection termination 630 in relation to the windshield 900.

Figure 4b - The air interface of Fig. 4a in a different view

Figure 4b shows a perspective view of the air interface 610 without the windshield 900. Additionally to figure 4a, a combined optic and electric power interface 851 is shown, which together with the combined high voltage and fiber optic connector 701 provides the connection of the high voltage cable 850 to the wind power station 600. The high voltage cable 850 is specially optimized to a high number of bending cycles, e.g. in the range of several million bending cycles.

Figure 4c - Another embodiment of the air interface

Figure 4c shows a perspective view of an air interface 610' according to a different embodiment, without the windshield 900. In this embodiment, the air interface 610' comprises a different suspension for the rotary joint cylinder 660. The longitudinal suspension 612' of the rotary joint cylinder 660 for movements along the flight direction of the wind power station 600 is here provided by a U-shaped element 615, which is fixedly attached to the rotary joint cylinder 660, but pivotally suspended at a central suspension ring 616. The suspension of the rotary joint cylinder 660 for movements along the span direction of the wind power station 600 is provided by the pivotable attachment of the central suspension ring 616 to the transverse suspension 611. Compared to the embodiment shown in Figure 4b, the option shown in Figure 4c features a central fulcrum, which may save space and weight and may help to get mechanically more optimized and simpler solutions for the construction of the windshield 900.

Figure 5a - Another embodiment of the air interface

Figure 5a shows an overview of a different embodiment of an air interface 610" as compared to the ones shown in figures 4a to 4c. Differently than in the embodiments of figures 4a to 4c, the air interface 610" for connecting the tether 500 to the wind power station 600 comprises a dome-shaped coupling structure 621 for mechanically coupling the rotary joint cylinder 660 to the wind power station 600. The mechanical forces, the electric energy and the electric and fiber optic signals are transferred from the tether 500 to the wind power station 600 and vice versa by the air interface 610". As in the embodiments of figures 4a to 4c, the air interface 610" additionally comprises a low flection termination 630 and a high voltage cable 850.

The dome-shaped coupling structure 621 allows the wind power station 600 to change its orientation relative to the tether 500 when flying crosswind for generating electric energy or during lifting and landing operations. Owing to the air interface 610", bending of the tether 500 at the interface to the wind power station 600 is avoided or at least reduced. The absence or at least reduction of cyclic bending of the tether 500 at the air interface 610" significantly reduces material fatigue of the tether 500. The dome-shaped coupling structure 621 allows a deviation of the axial direction of the low flection termination 630 in relation to the wind power station 600 in all directions and preferably up to a maximum angle a of e.g. between 15° to 30° in each direction.

The dome-shaped coupling structure 621 comprises a spherical inner shell 619 and a spherical outer shell 620. The inner shell 619 has a centrally arranged first opening, and the outer shell 620 has a centrally arranged second opening. The dimensions of the inner shell 619 and the first opening are smaller as compared to the ones of the outer shell 620 and the second opening, respectively. The inner shell 619 is movably arranged in such a way inside of the outer shell 620 that the second opening is completely covered from the inside by the inner shell 619. In the region of the first opening, the rotary joint cylinder 660 is fixedly attached to the inner surface of the inner shell 619. The low flection termination 630 extends through both the first and the second opening of the inner and the outer shell 619, 620, respectively.

A stop lip 609 can be attached to the inner shell 619, in order to limit the movability of the inner shell 619 relative to the outer shell 620. In order to prevent the inner shell 619 from moving away from the outer shell 620 e.g. at heavy wind conditions, a spherical tilt protection shell 607 is fixed to the stop lip 609. A gliding layer 608, applied on the surface of the tilt protection shell 607 facing towards the outer shell 620, provides low friction in case the two shells 607 and 620 get in contact with each other. The tilt protection shell 607 further protects the dome-shaped coupling structure 621 from environmental impacts like dust and rain. For improving the movability of the inner shell 619 relative to the outer shell 620, rolling ball bearings 640 can be provided. Stiffening supports 618 can be provided to strengthen the fixation of the rotary joint cylinder 660 on the inner shell 619 and to stiffen the spherical shape of the inner shell 619. A fixation frame 907 is used to attach the outer shell 620 to the wind power station 600. During crosswind flight, the forces induced by the wind power station 600 are transferred to the tether 500 via the fixation frame 907, and from the fixation frame 907 via the outer shell 620 to the inner shell 619 and from there via the rotary joint cylinder 660 to the low flection termination 630, which is attached to the end of the tether 500.

The electric energy and fiber optic signal transfer between the wind power station 600 and the tether 500 is provided by the high voltage cable 850 connected to the wind power station 600 by means of the combined high voltage and fiber optic connector 701 , and from the high voltage cable 850 via the rotary joint cylinder 660 to the low flection termination 630, which is attached to the end of the tether 500.

In order to avoid destruction of the high voltage cable 850 due to high torsion forces, axial rotation of the rotary joint cylinder 660 relative to the wind power station 600 needs to be prevented or at least limited. For this purpose, at least one stop element 623, i.e. in the form of a pin, is attached on the inner surface of the outer shell 620, which stop element 623 limits the motion of a lateral extension 622 provided at the periphery of the inner shell 619. By limiting the motion of the lateral extension 622, the stop element 623 prevents or at least limits rotation of the inner shell 619 relative to the outer shell 620. For an optimal fixation on the outer shell 620, the stop element 623 has a basis 624 that at least partly penetrates the outer shell 620.

For a low friction movement of the stop element 623 along the margins of the lateral extension 622, a freely rotatable roller 625 can be attached to the stop element 623, optionally by means of bearings 626.

The outer shell 620 can also serve as windshield hull. The outer shape of the outer shell 620 can additionally be modified aerodynamically, e.g. by adding wedge-shaped elements on both sides of the outer shell 620 along flight direction.

Figure 5b - The inner shell 619

Figure 5b shows a side view of the inner shell 619 together with the lateral extension 622 and with two stop elements 623.

Sufficient distance between the two stop elements 623 is required for a free movement of the lateral extension 622 in particular in the inclined position of the inner shell 619. A minimal gap with the dimension of the outer diameter of the rotation stop element 623 is sufficient between the lateral extension 622, touching e.g. the left stop element 623 and the outer surface of the right stop element 623 for most of the embodiments.

Figure 5c - The rolling ball bearing 640

In figure 5c), a possible design of the rolling ball bearing 640 is shown. A large rolling ball 643 is rolling on a hemispherical layer of small rolling balls 642, which are themselves arranged in a bearing support 644. In order to prevent the large rolling ball 643 from leaving its position and in order to prevent dust particles from entering the space between the large rolling ball 643 and the small rolling balls 642, an annular sealing element 641 is arranged around the large rolling ball 643.

Figure 5d - Another embodiment of a dome-shaped coupling structure 621 '

Figure 5d) shows a different embodiment of the dome-shaped coupling structure 621'. In contrast to the embodiment of figure 5a), the dome-shaped coupling structure 621' of figure 5d) comprises a pressurised air or oil film bearing. For this purpose, the outer shell 620' comprises a plurality of channels 646, which serve for the transportation of air or fluid to the space between the outer shell 620' and the inner shell 619, in order to establish a low friction air or fluid film between the shells 620' and 619. In case of loss of air pressure or oil pressure, additionally a gliding layer 645 can be attached to the inner surface of the outer shell 620' to achieve low friction between the shells 620' and 619 until the fluid medium film is re-established. At least one sealing element 647 is provided for sealing the space between the outer shell 620' and the inner shell 619 to the outside. The sealing element 647 can have a flexible anchoring basis 648 which is adapted to be inserted into a complementary shaped groove 649 provided on the outer shell 620', in order to fixate the sealing element 647 on the inner surface of the outer shell 620'. Stiff elements, such as a fixation rope, in particular a steel wire rope, can be embedded in the flexible anchoring basis 648, in order to improve the fixation of the sealing element 647 on the outer shell 620'. The geometrical shape of the sealing element 647 as shown in figure 5d is particularly suitable for a pressurised air film bearing. For the application of an oil film bearing, the geometrical shape has to be adapted to the respective requirements of an oil film.

Figure 6 - Rotary joint cylinder 660 and low flection termination 630 Figure 6 shows an overview of the rotary joint cylinder 660, the low flection termination 630 as well as of the main parts of the tether 500.

The rotary joint cylinder 660 provides an unlimited rotational connection between the tether 500 and the wind power station 600, transferring mechanical forces, electric energy and steering signals as well as fiber optic signals.

The tether 500 comprises an electric / optic system 510, which is adapted to carry out the electrical power and signal transmission as well as the fiber optic signal transmission between the wind power station 600 and the ground station 1. The electric / optic system 510 can also be referred to as an electric and optic line. The tether 500 also comprises a compression resistant layer 520 and an axial load-bearing layer 530. The compression resistant layer 520 of the tether 500 protects the electric / optic system 510 against high radial compressive forces induced by the axial load-bearing layer 530 under load and / or by bending or coiling operations of the tether 500. The axial load-bearing layer 530 is adapted to absorb tension loads acting on the tether 500 and induced by the wind power station 600 in operation. The tether 500 is preferably designed as specified in WO 2016/062735 A1 , the content of which is hereby included by reference in its entirety.

The function of the low flection termination 630 is to transfer high axial loads from the axial load-bearing layer 530 of the tether 500 to a tether termination plate 661 of the rotary joint cylinder 660 and vice versa. The tether termination plate 661 is a part of the mechanical load transfer chain between the wind power station 600 and the tether 500.

The low flection termination 630 further provides a protection of the electric / optic system 510 against contractional forces of the axial load-bearing layer 530 as well as a feed-through for the electric / optic system 510 to the rotary joint cylinder 660. The design of the low flection termination 630 is adapted to provide less flection loads to the tether 500 in operation, with the advantage of reducing the mechanical fatigue load and therefore optimizing the service lifetime of the tether 500 at the tether termination.

The low flection termination 630 comprises an inner tether clamp 635 and an outer tether clamp 631. The inner tether clamp 635 forms a continuation of the function of the compression resistant layer 520 to protect the electric / optic system 510 against high radial compressive forces induced by the axial load-bearing layer 530 under load. Furthermore, the inner tether clamp 635 provides a clamping force to the axial load-bearing layer 530, which is held between the inner tether clamp 635 and the outer tether clamp 631. For this purpose, the inner tether clamp 635 has an increasing outer diameter along the direction towards the tether termination plate 661. The outer tether clamp 631 is fixed to the tether termination plate 661 by means of outer fixation elements 632. The mechanical load transfer between the outer tether clamp 631 and the tether termination plate 661 is provided by the outer fixation elements 632. In order to achieve better control and long-term stability of the clamping forces that act on the axial load-bearing layer 530, outer fixation elements 632' can be provided which are equipped with a pressure spring 633. The pressure spring 633 can be a conventional helical spring or an annular spring providing high spring forces at a compact size.

The axial load-bearing layer 530 can be covered by an outer protection layer 503 (not shown in Figure 6, but in Figure 29), which protects the load-bearing layer 530 from wear and environmental impact like solar radiation, humidity and dust. If necessary, the outer protection layer 503 can be omitted in the portion where the axial load-bearing layer 530 is clamped. In order to prevent lumped loads to act against the axial load-bearing layer 530, the outer protection layer 503 can particularly be omitted in the portion of the tether 500 within the outer tether clamp 631.

The inner tether clamp 635 is fixed to the tether termination plate 661 by means of inner fixation elements 636. The clamping of the axial load-bearing layer 530 between the inner tether clamp 635 and the outer tether clamp 631 is achieved by a conical tube arrangement formed by the inner tether clamp 635 and the outer tether clamp 631. The outer tube diameter of the inner tether clamp 635 and the inner tube diameter of the outer tether clamp 631 both constantly increase towards the tether termination plate 661. This constant increase of the tube diameter leads to an equal clamping force along the entire outer surface of the inner tether clamp 635 and therefore also to a steep increase of the clamping force acting on the outer surface of the axial load-bearing layer 530 at the transition point between the compression resistant layer 520 and the inner tether clamp 635. This steep increase of the clamping force can lead to local damage of the axial load-bearing layer 530 leading potentially to a premature failure of the tether 500.

In order to achieve an optimized and preferably a constant increase of the clamping force along the length of the axial load-bearing layer 530, the increase of the outer tube diameter of the inner tether clamp 635' as well as the increase of the inner and outer diameters of the outer tether clamp 63T towards the tether termination plate 661 , 66T can be chosen in a way that the increase of the diameters is gradually, e.g. exponentially, increased towards the tether termination plate 661, resulting in a shape similar to the one shown by the inner tether clamp 635' and the outer tether clamp 631' on the left side of the illustration of the low flection termination 630 in figure 6.

The part of the outer tether clamp 631 , 63T beginning at the transition point between the inner tether clamp 635 and the compression resistant layer 520 and facing towards the ground station 1 preferably widens up along the direction towards the ground station 1, in order to allow for certain lateral movements of the tether 500 relative to the low flection termination 630 e.g. due to gust winds without damaging the axial load-bearing layer 530.

The axial load-bearing layer 530 of the tether typically comprises contrahelically wound high strength filaments of lightweight synthetic fibres like aromatic polyamide fibres (e.g. Kevlar^®) embedded in a high strength, flexible matrix material with good thermal conductivity like polyurethane. In order to prevent a pull-out of the fibers at the tether termination in the section where the clamping forces are effective, a more rigid material with a better adhesion to the fibres can be used, such as an epoxy resin matrix material. Thus, the epoxy resin matrix material can be used in in the section where the clamping forces are effective, while a conventional and / or different matrix material is used in other parts of the tether 500. Alternatively or additionally, epoxy resin with rubber addition, for example carboxyl- terminated butadiene-acrylonitrile random copolymer (CTBN) modified epoxy resin matrix material, can be used for improving the flexibility of the resulting fiber composite material.

The rotary joint cylinder 660 includes an electric / optical rotary joint 700, providing a rotatable electrical and fiber optic connection between the electric / optic system 510 of the tether 500 and the wind power station 600. The outer parts of the rotary joint cylinder 660 include the tether termination plate 661 , a first fixation ring 670, a second fixation ring 671 and a cylinder tube 674. The tether termination plate 661 is rotatably held between the first fixation ring 670 and the second fixation ring 671 by means of a ball bearing 664 shown on the right side of figure 6. Alternatively, a tether termination plate 66T can be provided which is rotatably held between a first fixation ring 670' and a second fixation ring 67T by means of a cylinder ball bearing 665 as shown on the left side of figure 6. The first fixation ring 670, 670' and the second fixation ring 671, 67 are fixed to each other by means of heavy load threaded connections 672. In order to protect the bearings 664, 665 against dust and other environmental impact like humidity, lip seals 666 can be provided. The first fixation ring 670, 670' is fixed on the cylinder tube 674 by means of further heavy load threaded connections 672. Likewise, the suspension ring 677 is fixed on the cylinder tube 674 by means of yet further heavy load threaded connections 672. As explained further above, the suspension ring 677 features a pivot bearing connection to the longitudinal suspension 612.

The parts of the electric / optical rotary joint 700, which rotate together with the wind power station 600 relative to the tether 500, are attached to the cylinder tube 674 by means of fixation plates. Outer fixation plates 675 are attached to or made in one piece with the cylinder tube 674. Inner fixation plates 735 are attached to or made in one piece with the electric / optical rotary joint 700. Each of the inner fixation plates 735 is fixed to a respective outer fixation plate 675 by means of a respective fixation 736, e.g. a screw-nut fixation extending through oblong holes.

The parts of the electric / optical rotary joint 700, which do not rotate with the wind power station 600, are attached to the tether termination plate 661, 66T by means of connection elements 662 and screws 663.

Figure 7 - Rotary joint cylinder 660' with active tether torsion compensation

Figure 7 shows a variation of the rotary joint cylinder 660', which differs from the rotary joint cylinder 660 of figure 6, by the implementation of an active tether torsion compensation.

In operation, the wind power station 600 flying crosswind typically carries out circular paths or figure-8 paths.

A continuous circular rotation of the wind power station 600 around the tether axis would automatically lead to an increasing torsion load to the tether 500 and soon lead to a failure. One possibility to avoid this, is to release the built up torsion load after a few rotations of the wind power station 600 by changing the direction of rotation from e.g. a clockwise rotation to a counter-clockwise rotation. However, in this case, cyclic torsion loads are still introduced to the tether 500.

The axial load-bearing layer 530 of the tether 500 typically comprises contrahelically wound layers with high strength filaments of lightweight synthetic fibres like aromatic polyamide fibres (e.g. Kevlar^®). Axial torsion load to a tether 500 having an axial load-bearing layer 530 made of contrahelically wound high strength filaments leads to a significant load imbalance between the filaments wound in clockwise direction and the ones wound in counter-clockwise direction, which can result in a premature fatigue of the axial load-bearing layer 530.

Instead of carrying out circular paths, the wind power station 600 could also fly along continuous figure-8 paths. In this case, cyclic load changes due to the changes of rotation direction of the wind power station 600 can adversely affect the tether 500.

The optimal solution in terms of generated electrical power, material fatigue, cable tangling and coiling would be a continuous circular trajectory of the wind power station 600. With a continuous circular trajectory, load changes and associated adverse effects are minimized. The rotary joint cylinder 660 as shown in figure 6 provides an unlimited rotational connection for transferring mechanical forces, electrical power and / or signals as well as fiber optic signals between the tether 500 and the wind power station 600. Since a certain amount of friction is inevitable with respect to the ball bearings 664, 665 of the rotary joint cylinder 660 under load, a simultaneous rotation of the tether 500 with the rotary joint cylinder 660 is still to be expected at least to a certain degree. To solve this problem and to prevent torsion of the tether 500, a controlled active rotation of the tether termination plate 661 provided. With this controlled active rotation, the tether termination plate 661 is actively rotated to compensate for any rotation of the wind power station 600 relative to the tether 500 such that no torsion of the tether 500 occurs. For this purpose, a drive 683, e.g. in the form of an electric motor, is provided. The drive 683 is fixed to the cylinder tube 674 and is adapted to rotate, via an adjusting gear 682, a toothed ring 680 which is fixed to the tether termination plate 661 by means of heavy load threaded connections 672. The rotational position of the tether termination plate 661 in relation to the cylinder tube 674 is measured by a rotary encoder 684 and transferred via a power and signal cable 685 to e.g. the central control unit and communication interface 26 shown in figure 2.

Based on the information of the angular velocity of the wind power station 600 flying circular paths, measured by the position, direction and velocity measuring system 605 (see figure 1 ), and based on the information of the rotational position of the tether termination plate 661 provided by the rotary encoder 684, the rotational position of the tether termination plate 661 can be adjusted by a controller via the central control unit and communication interface 26 in a way, that no torsion load is applied to the tether 500 by the wind power station 600. Further torsion compensation and readjustment in case of small deviations of the tether 500 from the untorsioned state induced by e.g. wind forces or small inner layer displacements in the tether 500 can be achieved by using the information of the rotary encoder 684 in combination with the information provided by the information unit 405 of tether guiding system 400, as explained later with respect to figures 26 to 30.

Figure 8 - Low flection termination 630 combined with sling system I

Figure 8 shows different views of an alternative embodiment of the low flection termination 630' compared to the one shown in figure 6.

As already mentioned in the description of figures 6 and 7, the axial load-bearing layer 530 of the tether 500 typically comprises contrahelically wound high strength filaments of lightweight synthetic fibres like aromatic polyamide fibres (e.g. Kevlar^®).

In figure 8a, the fixation of the axial load-bearing layer 530 to the tether termination plate 661" is not only effected via clamping forces, i.e. by means of clamps 635" and 631", as in the embodiment of figure 6, but is also effected by means of spliced slings 690, 691. The spliced slings 690, 691 are formed by the ends of the high strength filaments and are attached to the tether termination plate 661" by means of sling bolts 692 which are fixed to a fixation cylinder 693. The fixation cylinder 693 is fixedly attached on the tether termination plate 661" by means of outer fixation elements 632".

Typically, the contrahelically wound high strength filaments of the axial load-bearing layer 530 are arranged in different layers which can be distinguished by the winding direction of the filaments. In figure 8a, an example of two layers is shown, comprising inner layer filaments 688 and outer layer filaments 689 with different winding directions. Within the axial load-bearing layer 530, the filaments with different winding directions can be arranged for example in two different layers, but they can also be interwoven along a major part of the tether 500 and be separated in a filament section 687 at the end of the tether 500 towards the spliced slings 690, 691.

The load transfer from the tether 500 to the tether termination plate 661" and vice versa can be arbitrarily distributed to the tether clamps 635", 631" and the spliced slings 690, 691.

In a first transfer load distribution, the inner tether clamp 635" and the outer tether clamp 631" essentially only serve for guiding the high strength filaments and for preventing a bending of the high strength filaments. Here, essentially the entire axial load acting on the tether 500 is absorbed by the high strength filaments of the axial load-bearing layer 530 which transfer this load via the spliced slings 690, 691 to the sling bolts 692, from the sling bolts 692 to the fixation cylinder 693, and from there via the outer fixation elements 632" and the pressure spring 633 to the tether termination plate 661". In this case of load distribution, the filament section 687 could consist only of high strength filaments, without a matrix material for the embedding of the high strength filaments, since no load transfer via a clamping force is needed in this section.

In a second transfer load distribution, a significant part or even essentially all of the axial load acting on the tether 500 is transferred to the tether termination plate 661" via a clamping of the axial load-bearing layer 530 and the filament section 687 by means of the tether clamps 635", 631". For this purpose, provision of a suitable matrix material for the embedding of the high strength filaments in the filament section 687 is necessary. Examples of suitable matrix materials, which can be applied after the correct arrangement of the filaments and for an easy implementation of the inner and outer layer filaments 688, 689 as well as optionally of the spliced slings 690, 691 are polyurethane or elastomers like nitrile elastomers. Epoxy resin matrix materials are also possible.

Of course, the entire range of transfer load distributions between the first and the second of the above-mentioned load distributions is possible.

In figures 8b and 8c, different possible arrangements of the sling bolts 692 within the fixation cylinder 693 are shown. Each of figures 8b and 8c shows a cross-sectional view of the fixation cylinder 693 in a plane that extends through the sling bolts 692 and in a perpendicular direction with respect to the longitudinal direction of the tether 500.

As already mentioned, the different layers of the high strength filaments of the axial load- bearing layer 530 can be distinguished by the direction along which their respective filaments are wound, i.e. in a clockwise or counter-clockwise direction. The filaments wound in clockwise direction can for example form the inner layer filaments 688 and the filaments wound in counter-clockwise direction can form the outer layer filaments 689.

In order to preserve the mechanical stability of the tether termination, the spliced slings 690, 691 and the corresponding sling bolts 692 are preferably arranged along the helical path and with the same winding angle as the high strength filaments. An optimal load transfer between the spliced slings 690, 691 and the sling bolts 692 can be achieved when the longitudinal axes of the sling bolts 692 are orthogonal to the direction of the longitudinal direction of the spliced slings 690, 691. In relation to the axial direction of the tether 500, the angular orientation of the sling bolts 692 associated with the inner layer filaments 688 is preferably opposite to the one of the sling bolts 692 of the outer layer filaments 689, as seen in figures 8a, when viewed in synopsis with figures 8b and 8c, respectively.

Figure 8b shows a first possible arrangement of the sling bolts 692 within the fixation cylinder 693 of a low flection termination 630', the sling bolts 692 with different angular orientations, i.e. the sling bolts 692 connected to the inner layer filaments 688 and the sling bolts 692 connected to the outer layer filaments 689, arranged along the same radial directions.

Figure 8c shows a second possible arrangement of the sling bolts 692 within the fixation cylinder 693' of a low flection termination 630", the sling bolts 692 with different angular orientations, i.e. the sling bolts 692 connected to the inner layer filaments 688 and the sling bolts 692 connected to the outer layer filaments 689, arranged along different radial directions.

The way the sling bolts 692 are mounted in the fixation cylinder 693 is shown in figure 9b.

Depending on the specific geometrical shape of the fixation cylinder 693, on the number and the space requirements of the spliced slings 690, 691 and on the optimal placement of the holes for the outer fixation elements 632", one of the geometrical arrangements of the sling bolts 692 shown in figures 8b or 8c can be advantageous, or a solution in-between.

Figure 9 - Low flection termination 630 combined with sling system

Figure 9 shows a part of the circumference of the fixation cylinder 693 with spliced slings attached thereto in accordance with two further embodiments. In each case, the respective parts are shown in a radial cross-sectional view projected onto a plane.

In figure 9a, the different angular direction of the inner layer with the spliced slings 690, the respectively associated sling bolts 692 and the inner layer filaments 688 in the region of the low flection termination 630' can be seen, as compared to the angular direction of the outer layer with the spliced slings 691 , the respectively associated sling bolts 692 and the outer layer filaments 689. The alignment of the direction of the spliced slings 690, 691 with the winding angle of the high strength filaments shown in the filament section 687 can also be seen, as well as the orthogonal arrangement of the longitudinal axes of the sling bolts 692 in relation to the longitudinal directions of the spliced slings 690, 691.

In the embodiment shown here, the high strength filaments of the axial load-bearing layer 530 are not interwoven, but arranged in two separate layers with different winding directions. In the filament section 687, the high strength filaments are not embedded in the matrix material as in the other parts of the axial load-bearing layer 530. In the region between the filament section 687 and the sling bolts 692, the high strength filaments of the inner and outer layer filaments 688, 689 are arranged to multiple sets of interwoven bundles in each case, in order to form the spliced slings 690, 691 at the sling bolts 692. The spliced slings 690, 691 can be produced e.g. by applying the technique of a sewed-up splice, a plug-in splice or a “brummel lock” splice.

In figure 9b, the arrangement of the sling bolts 692 within the fixation cylinder 693 of the low flection termination 630' is shown in more detail. In order to get a balanced load transfer for the high strength filaments along the entire circumference of the axial load-bearing layer 530, load adjustment screws 694 are provided, in order to adjust the pretension of each of the individual spliced slings 690, 691 to an equal value (along the circumference). By means of a respective tool, such as a screwdriver or a hexagon wrench, the load adjustment screws 694 can be rotated through a corresponding hole of the fixation cylinder 693. The threaded connection between each load adjustment screw 694 and the respective sling bolt 692 allows to adjust the position of the sling bolts 692 within the fixation cylinder 693 and therefore to apply a controlled pretension to the high strength filaments of the spliced slings 690, 691.

For the installation of the spliced slings 690, 691 together with the sling bolts 692 and the load adjustment screws 694, in a first step, the spliced slings 690, 691 are placed in the corresponding openings of the fixation cylinder 693. In a next step, the sling bolts 692 are inserted into the openings of the fixation cylinder 693 and are then centered in the openings of the spliced slings 690, 691 . In the next step, the load adjustment screws 694 are inserted into the corresponding openings of the fixation cylinder 693 and screwed into the sling bolts 692^. In a last step, the individual spliced slings 690, 691 are pre-tensioned to a defined (and equal) value via the load adjustment screws 694. Figure 10 - Low flection termination 630 combined with meander clamp system

Figure 10 shows a further alternative way to fixate the ends of the high strength filaments in the low flection termination 630"' as compared to the previous figures 8 and 9. Instead of forming spliced slings and fixate these slings to the tether termination plate 661", the ends of the high strength filaments are clamped by means of meander-shaped clamps 697, 698 and 699 and are fixed via outer fixation elements 632"', 632"" to the tether termination plate 661'".

In the embodiment shown in figure 10, a separate fixation of the ends of the high strength filaments for two layers is shown. The ends of an inner layer form an inner layer end part 695 and the ends of an outer layer form an outer layer end part 696, as shown. Of course, a meander-shaped clamping system with a different number of separate layers 695, 696 can also be implemented. A separate clamping of the different layers with different helical winding directions can be provided, in order to avoid the “scissoring effect” which occurs, when filaments that cross each other are moved relative to each other and as a result get damaged. The “scissoring effect” becomes relevant especially at high numbers of load cycles.

In the embodiment of figure 10, the inner layer end part 695, which is formed by the high strength inner layer filaments 688' in combination with a suitable matrix material, is clamped between an upper meander clamp 699 and a middle meander clamp 698. The clamping force can be adjusted by outer fixation elements 632"" and pressure springs 633.

The outer layer end part 696, which is formed by the high strength outer layer filaments 689', is clamped between the middle meander clamp 698 and a lower meander clamp 697. The clamping force can be adjusted by further outer fixation elements 632'" and further pressure springs 633.

Similar to the embodiment shown in figures 8 and 9, in the filament section 687, the high strength filaments are not embedded in the matrix material of the axial load-bearing layer 530. Instead, the high strength filaments of the filament section 687 are embedded in a suitable matrix material, such as an epoxy matrix material or a polyurethane matrix material, in order to adapt the volume to be clamped to the gap between the clamps 635’” and 631 In figure 10, it can be seen that the clamping of the inner and outer layer end parts 695, 696 between the lower, middle and upper meander clamps 697, 698, 699 is achieved by the meander flanks, but not by the bottom and top faces between the flanks. In this way, it is not only possible to achieve a particularly large effective clamping surface, but also a better fine adjustment of the clamping force over a certain clamp distance. If using the bottom and / or top faces between the meander flanks to achieve the clamping, the radial diameter of the meander clamps 697, 698, 699 would have to be larger for achieving a similar effective clamping surface, which in turn would result in an unfavourably larger diameter of the low flection termination 630"'. The redirection over many meandering periods of the inner and outer layer end parts 695, 696 together with the resulting friction between the meander clamps 697, 698, 699 contribute to the load transfer between the axial load-bearing layer 530 and the tether termination plate 66T".

A possible decreasing volume content of high strength filaments in each of the outer layer end parts 695, 696 with increasing distance to the center axis of the low flection termination 630'" can be compensated by means of a higher volume content of a suitable matrix material or by means of a decreasing distance between the surfaces of the lower, middle and upper meander clamps 697, 698, 699 along the meander-shaped path of the inner and outer layer parts 695, 696 from the parts close to the center axis to the more peripheral parts.

Suitable matrix materials for the inner layer end part 695 and the outer layer end part 696 have already been mentioned further above in the description with respect to figures 6 and 8

With the clamping systems as described, the load transfer from the tether 500 to the tether termination plate 66T” and vice versa can be arbitrarily distributed to the tether clamps 635’”, 63T” and the meander clamps 697, 698, 699.

Figure 11 - Overview of the electric / optical rotary joint 700

Figure 11 shows a more detailed view of the electric / optical rotary joint 700 than shown in figures 6 and 7. The electric / optical rotary joint 700 as shown in figure 11 can be used for providing an electrical and fiber optic connection with unlimited rotational capabilities between the tether 500, i.e. the electric / optic system 510, and the wind power station 600 (as part of the air interface 610 shown in figure 2). The electric / optical rotary joint 700 shown in figure 11 is especially suited for an unlimited rotational connection between two parts of a medium- or high voltage system, since the electrode geometry of the electric conductors and the gaseous insulation allow the application of medium- or high voltages in a reliable way, also with respect to long-term uses. Moreover, the electric / optical rotary joint 700 can be used to provide a respective electrical and fiber optic connection between the drum 200 and the rotary table 50 of the ground station 1 (see figure 1) and / or as the rotary joint 100 between the carrier plate 210 and the base structure 10 (figure 1). In the following, the electric / optical rotary joint 700 is described with respect to the application for connecting the tether 500 and the wind power station 600, i.e. as part of the air interface 610.

The parts of the electric / optical rotary joint 700 that rotate with the wind power station 600 include a rotary joint cylinder 737, a connector fixation plate 740, a rotary connector bearing ring 720, a rotary connector plate 719, a further combined high voltage and fiber optic connector 701 shown in the upper part of figure 11 and the upper part of a high voltage and fiber optic rotary joint 702.

The electric / optical rotary joint 700 also comprises a rotary connector fixation plate 715 that does not rotate with the wind power station 600, but is attached to the tether termination plate 661 not shown in figure 11 , but shown e.g. in figures 6, 7 and 10, by means of connection elements 662, screw-nut connections 667 and screws 663, which allow an easy mounting and adjusting of the different parts of the electric / optical rotary joint 700. Further parts of the electric / optical rotary joint 700 that do not rotate with the wind power station 600, but are attached to the tether 500, include a seal spring limiter 730, a further combined high voltage and fiber optic connector 701 shown in the lower part of figure 11 and the lower part of the high voltage and fiber optic rotary joint 702.

The application of the electric / optical rotary joint 700 is generally not limited to the connection between a flying apparatus such as the wind power station 600 and a tether such as the tether 500. For example, the electric / optical rotary joint 700 can also be applied in the ground station 1 : Figure 28 shows the application of the electric / optical rotary joint 700, in order to form a rotary connection between the drum 200 and the carrier plate 210 (also see figure 2). Figure 39 shows the application of the electric / optical rotary joint 700, in order to form the rotary joint 100 between the carrier plate 210 and the base structure 10 (also see figure 2).

The outer shape of the electric / optical rotary joint 700 is mainly formed by a gas-tight cylinder comprising the rotary joint cylinder 737 and the connector fixation plate 740 as well as the rotary connector fixation plate 715, the rotary connector bearing ring 720 and the rotary connector plate 719. The rotary joint cylinder 737, which can also be referred to as a contact cylinder, is fixed to the connector fixation plate 740 by means of heavy load threaded connections 672 and sealed by means of an O-ring seal 723. The gas-tightness of the cylinder to the outside serves to protect the electric / optical rotary joint 700 from environmental impacts like dust, humidity and / or aggressive gases. Additionally, due to the gas-tightness, the application of an electrically insulating gas in the inner volume of the cylinder becomes possible, in order to reduce the necessary electric insulating distances by increasing the dielectric strength between the electrodes. To further reduce the necessary electric insulating distances and to minimise the necessary volume of the electric / optical rotary joint 700, the electrically insulating gas can be applied with a higher pressure than the ambient pressure. Suitable electrically insulating gases are for example pressurised clean air, carbon dioxide or gas mixtures containing fluoroketone, fluoronitrile or sulfurhexafluoride (SF₆). Suitable pressures are in the range of a few bars up to approx. 10 to 15 bar above ambient pressure.

In order to improve the withstand voltage of the gaseous electric insulation in the electric / optic rotary joint 700 and to prevent the so-called firefly motion of conducting particles in the electric field generated by a direct current transmission system, the parts of the high-voltage electrodes exposed to the electric field can be coated with thin layers of AI₂O₃ with a thickness in the range of a few 10 micrometres. The electric contact surfaces of the high voltage rotary joint contact system 837 are preferably not coated, in order to provide good electric contact. The prevention of the firefly motion helps to reduce the risk of a flashover in the gas compartment, i.e. in the interior of the rotary joint cylinder 737, when conducting particles are present. It is referenced in this respect to the document of Hasegawa T., Kawahara A., Hatano M., Yoshimura M., Fujii H., Inami K., Hama H., Nakanishi K.; Improvement of withstand voltage at particle contamination in DC-GIS due to dielectric coating on conductor; Gaseous Dielectrics VIII, Edited by Christophorou and Olthoff, Plenum Press, New York, 1998], the entire content of which is hereby incorporated by reference.

For evacuating and subsequent filling of the electric / optical rotary joint 700 with the electrically insulating gas, a gas exchange valve 741 is provided. Pressure control of the electrically insulating gas, in order to detect leakage and / or monitor for correct filling pressure, is provided by a gas density sensor 742 transmitting the measured signals via a signal cable 743.

In order to monitor the dielectric integrity of the electric insulation system of the electric / optical rotary joint 700, a partial discharge sensor 731 can be provided in the interior of the electric / optical rotary joint 700, e.g. mounted at the connector fixation plate 740. The electromagnetic partial discharge signals emitted from electric insulation defects in the ultra- high frequency range are detected by the partial discharge sensor 731 and transmitted via a further signal cable 733 to a monitoring system which allows defect diagnosis and provides information for decisions on countermeasures. The partial discharge sensor 731 is mounted, e.g. in the connector fixation plate 740, in a gas-tight way by extending through a circumferential seal 732. In order to provide a broadband signal transmission with a defined cable impedance and to shield the signal cable 733 from radio interference signals, the signal cable 733 is shielded with a coaxial cable shield 734.

The electric and fiber optic connections of the electric / optical rotary joint 700 comprise pluggable high voltage and fiber optic connectors 701 , which allow electric power and optic signal transmission via the high voltage and fiber optic rotary joint 702 which is axially aligned between and connected to two combined high voltage and fiber optic connectors 701. The high voltage and fiber optic rotary joint 702 allows unlimited rotations of the airborne wind power station 600 with respect to the electric / optic system 510.

In order to provide fiber optic signal transmission from and to parts of the device which are rotating with the rotary joint cylinder 737, branch line fiber optic cables 710 can be provided that extend from the upper part of the high voltage and fiber optic rotary joint 702 to a gas- tight feedthrough 712 arranged in the connector fixation plate 740 or in the rotary joint cylinder 737 and from there to a respective receiver and / or transmitting device of the fiber optic signals. The provision of branch line fiber optic cables 710 is particularly useful, if the electric / optical rotary joint 700 serves to provide an electrical and fiber optic connection between the drum 200 and the rotary table 50 of the ground station 1 and / or as the rotary joint 100 between the carrier plate 210 and the base structure 10 (see figure 1).

In order to provide fiber optic signal transmission from and to parts of the device which are not rotating with the rotary joint cylinder 737, further branch line fiber optic cables 710' can be provided that extend from the lower part of the high voltage and fiber optic rotary joint 702 to another gas-tight feedthrough 712' arranged in the rotary connector fixation plate 715 and from there to a respective receiver and / or transmitting device of the fiber optic signals.

The connection of the branch line fiber optic cables 710, 710' from and to the gas-tight feedthroughs 712, 712' can be established by means of connectors 711 , 71 T.

The electric / optical rotary joint 700 further comprises a gas-tight rotary sealing in the region between the periphery of the rotary connector fixation plate 715 and at the rotary connector bearing ring 720. The gas-tight rotary sealing comprises an upper gliding ring 725 which is attached, via the seal spring limiter 730, to the rotary connector fixation plate 715 and a lower gliding ring 722 which is attached to the rotary connector bearing ring 720. The seal spring limiter 730 is fixed to the rotary connector fixation plate 715 with the help of screws 663. A possible material combination of the lower gliding ring 722 and the upper gliding ring 725 to achieve a very low friction coefficient at the contact surface and to provide a gas- tight sealing under dynamic conditions is e.g. very fine polished steel with polytetrafluoroethylene (PTFE). E.g. the lower gliding ring 722 could be made of steel and the upper gliding ring 725 of polytetrafluoroethylene or vice versa..

A seal spring 728 is provided for achieving the necessary contact pressure for dynamic sealing between the lower gliding ring 722 and the upper gliding ring 725. The pressure force of the seal spring 728 is established between a stop surface formed by the seal spring limiter 730 and the upper gliding ring 725. Between seal spring 728 and the upper gliding ring 722, an O-ring seal 723 can be provided. For protecting the O-ring seal 723 against the seal spring 728, an O-ring seal protection 727, e.g. in the form of a metallic ring, can be provided between both parts.

Between the lower gliding ring 722 and the rotary connector bearing ring 720 a further O- ring seal 723 can be provided for static sealing. Also between the upper gliding ring 725 and the seal spring limiter 730 an O-ring seal 723 can be provided. The connection of the seal spring limiter 730 to the rotary connector fixation plate 715 as well as the connection of the combined high voltage and fiber optic connector 701 to the rotary connector fixation plate 715 are provided in a gas-tight manner. A further O-ring seal 723 can be provided, in order to achieve gas-tight sealing between the rotary connector bearing ring 720 and the rotary joint cylinder 737.

The tether rotary connector fixation plate 715 is rotatably held between the rotary connector bearing ring 720 and the rotary connector plate 719 by means of a rotary connector ball bearing 717 as shown on the right side of figure 11.

Alternatively, the rotary connector fixation plate 715' can be rotatably held between the rotary connector bearing ring 720' and the rotary connector plate 719' by means of a rotary connector cylinder bearing 718 as shown on the left side of figure 11.

The rotary joint cylinder 737 and the rotary connector bearing ring 720, 720' as well as the rotary connector plate 719, 719' are fixed to each other by means of heavy load threaded connections 672. In order to protect the bearings 717, 718 against dust and other environmental impact like humidity, lip seals 666 can be provided.

Considering e.g. a direct current (DC) electric power transmission between the airborne wind power station 600 and the ground station 1, a favourable electric circuit configuration would be a monopolar direct current transmission with e.g. the positive polarity associated with a center conductor of the electric / optic system 510 and the negative polarity associated with a screen conductor, i.e. a conductor arranged distant and radially outside of the center conductor, of the electric / optic system 510, or vice versa. One advantage of a monopolar direct current transmission is that only one of the conductors has to be equipped with an electric insulation system, which leads to a significant reduction of the weight per length and the mechanical complexity of the tether 500. The return current flowing in the screen conductor 517 (explained in detail with respect to figure 12) of the electric / optic system 510 also has to be transferred through the electric / optical rotary joint 700. The cross-section of the metallic structures or additionally installed earth path structures at the electric / optical rotary joint 700 are considered sufficient to carry the return current.

In order to protect the bearings 717, 718 against electro-erosion damage due to electric current flowing through the bearings 717, 718, an electrically conducting path with low resistance can be established between the rotary joint cylinder 737 and the rotary connector fixation plate 715 shown on the right side of figure 11 , different to the implementation on the left side. The electrically conducting path can be established by a contact element 828, connecting the rotary joint cylinder 737 with a metallic cylinder contact element 777 which is fixed to the metallic seal spring limiter 730' via a screw 663. The cylinder contact element 777 has an overall cylindrical shape. From the metallic seal spring limiter 730', the earth path current can flow to the connector fixation plate 740 and from there via a suitable screen earthing cable 750 to the folded back electric screen conductor 519 of the electric screen of the electric / optic system 510. Additionally or alternatively, a further sliding contact 840 in combination with a contact spring 838 and a contact ring 778 can be provided between the rotary joint cylinder 737 and the cylinder contact element 777. By implementing multiple numbers of sliding contacts 840 and / or contact elements 828, the resulting return path resistance between the rotary joint cylinder 737 and the rotary connector fixation plate 715 can be reduced.

To prevent possible electrically conductive dust to be generated by the operation of the sliding contacts 840 and / or the contact elements 828 and to enter the area where gaseous dielectric interfaces can be polluted and functionally impaired, a rotary joint seal 829 can be provided between the rotary joint cylinder 737 and the cylinder contact element 777, preferably with a material pairing that shows very low friction and wear. The rotary joint seal 829 can be fixed to the cylinder contact element 777.

In addition, the bearings 717, 718 can be made of a ceramic non-conductive material, in order to prevent an electric current flowing through the bearings.

Figure 12 - Overview of the combined high voltage and fiber optic connector 701

Figure 12 shows an overview of an embodiment of the combined high voltage and fiber optic connector 701. The combined high voltage and fiber optic connector 701 mounted onto the rotary connector fixation plate 715 is shown in this case. The combined high voltage and fiber optic connector 701 provides a pluggable high voltage and fiber optic connection in general, and specifically of the electric / optic system 510.

The combined high voltage and fiber optic connector 701 comprises a socket insulator 763, a connector element 764, a stress cone 761 , a deflector 760 as well as the electric / optic system 510.

The electric / optic system 510 comprises an elastic high voltage cable and a fiber optic cable 511 arranged in the center of the elastic high voltage cable. The fiber optic cable 511 can comprise a single or a plurality of fiber strands. The fiber strand or fiber strands can extend along a straight line within the fiber optic cable 511 or have a slightly helical arrangement for improving the longitudinal stretchability of the tether 500. The design of the tether 500 and in particular of the electric / optic system 510 are described in detail in WO 2016/062735 A1 , the entire disclosure of which is hereby incorporated by reference. The elastic high voltage cable comprises a central conductor formed by electric conductors 513 and a semi-conductive layer 514, insulated by an electric insulation layer 515 and screened, i.e. distantly surrounded, by a semi-conductive buffer layer 516 in combination with a screen conductor 517.

The semi-conductive layers 514, 516 serve to smoothen the surface of the electric conductors 513, 517, in order to minimize electric field strength variations in the electric insulation layer 515.

The electric conductors 513, 517 serve to guide the electric current for the electric power transfer between the wind power station 600 and the ground station 1.

An elastic core 512 in combination with a helical arrangement of the electric conductors 513, 517 in an optimal lay angle provides axial elasticity for the tether 500 and serves to minimize the material fatigue when the electric / optic system 510 is exposed to cyclic axial strain. An elastic buffer / protection layer 518 protects the electric conductor 517 against damage and environmental impacts.

At the termination of the electric / optic system 510, the electric screen conductors 517 are folded back, in order to form a folded back electric screen conductor 519, which is guided into a cable lug 775. This cable lug 775 is connected to the screen earthing cable 750 and to screws 663, in order to form an electrically conducting path with low resistance to the rotary connector fixation plate 715 for the return current flowing in the screen conductors 517 of the electric / optic system 510.

The description in the preceding paragraphs concerned the combined high voltage and fiber optic connector 701 shown in the lower part of figure 11 , i.e. the combined high voltage and fiber optic connector 701 mounted on the rotary connector fixation plate 715. The combined high voltage and fiber optic connector 701 shown in the upper part of figure 11 , i.e. the one mounted on the connector fixation plate 740, preferably has an analogous design and construction. For example, in the case of the combined high voltage and fiber optic connector 701 shown in the upper part of figure 11 , the screen earthing cable 750 would be connected to the connector fixation plate 740 (see figure 11).

The socket insulator 763, which belongs to the female part of the combined high voltage and fiber optic connector 701 , is electrically insulating, resistant to the inner gas pressure of the rotary joint cylinder 737 and mounted in a gas-tight manner with O-ring seals 723 on the rotary connector fixation plate 715 The socket insulator 763 is fixed to the rotary connector fixation plate 715 (or to the connector fixation plate 740) with the help of socket thread inserts 772 and screws 773.

In the upper part of the socket insulator 763, the connector element 764 is mounted, together with a high voltage shield 762.

The connector element 764 establishes a low resistance electric contact in combination with a low signal attenuation fiber optic connection between the tether 500 and the rotary joint 702.

The metallic high voltage shield 762 provides electric field relief between the socket insulator 763, the stress cone 761 and the metallic parts of the connector element 764.

The stress cone 761 in combination with the deflector 760 and the high voltage shield 762 provide electric field control at the termination of the electric / optic system 510 in a way, that the electric field has minimal variations below a maximum value.

The region formed by the electric insulation layer 515, the stress cone 761 and the semi- conductive material of the deflector 760 features a smooth, geometrically well-defined and continuous transition between the deflector 760 and the stress cone 761 along the surface of the electric insulation layer 515.

The semi-conducting deflector 760 is adapted to be on the same electric potential as the semi-conductive buffer layer 516 and to decrease the electric field strength between the semi-conductive layer 514 and the semi-conductive buffer layer 516 along the longitudinal direction and towards the connector element 764 in a continuous and smooth way.

The stress cone 761, which is made of a rubber-like electrically insulating material, and the deflector 760 are pressed towards the stiff and rigid material of the socket insulator 763 by means of a press ring 769 in combination with a spring 770.

Due to the pressing of the stress cone 761 and the deflector 760 against the socket insulator 763 and by providing a suitable electrically insulating grease at the interfaces of the electrically insulating parts of the combined high voltage and fiber optic connector 701, air gaps are avoided. Air gaps are associated with a lower dielectric strength than the surrounding solid insulating materials and are the source of partial discharges and possible dielectric failure.

The spring 770 abuts on the press ring 769 with a first end and on a press ring casing 768 with a second end. The press ring casing 768 is fixedly attached to the socket insulator 763 by means of threaded fixation elements 767, which are screwed into thread inserts 765 provided in the socket insulator 763.

To prevent high flection and peak mechanical loads of the electric / optic system 510 at the entry to the combined high voltage and fiber optic connector 701 , the press ring casing 768 has an entry part that widens up in the direction towards the electric / optic system 510 and towards the tether 500. As a further measure for preventing high mechanical loads acting on the electric / optic system 510, a flexible layer element 771 can be attached to the inner side of the entry part of the press ring casing 768.

Figure 13 - Connector element 764

Figure 13 shows an overview of the connector element 764 with details of the high voltage contact system.

The high voltage contact system provides a pluggable low resistance electric connection of the inner high voltage electric conductors 513 of the electric / optic system 510 to an electrically conducting conductor socket 792.

The high voltage contact system of the connector element 764 comprises the conductor socket 792 which represents the female part, and a contact body 785 which together with contact springs 786 represent the male part of the connection. The contact springs 786 ensure a low resistance electric contact between the conductor socket 792 and the contact body 785, suitable for many coupling cycles.

The electric conductors 513 of the high voltage center conductor are crimped onto a pressure resistant tube 781 by means of a crimping tube 783, which is deformed together with the electric conductors 513. The originally undeformed round electric conductors 513 are named as crimped electric conductors 782 in the deformed state in figure 13. The deformation of the pressure resistant tube 781 during the crimping process is marginal, in order to maintain a central passage for the fiber optic cable 511, as a continuation of the central passage of the elastic core 512. The semi-conductive layer 514 of the electric conductors 513 ends in the region or at the entry of the crimping tube 783.

A low resistance electric contact is provided between the contact body 785 and the crimped electric conductors 782 via the crimping tube 783 and a clamping cone 784. Thus, both the crimping tube 783 and the clamping cone 784 are made from an electrically conducting material.

The clamping cone 784 has a central cylindrical inner passage, a conical outer shape and can have longitudinal slits extending from each end over a length of approximately 70 to 90 percent of the total length of the clamping cone 784 (not shown in figure 13). The longitudinal slits extending from each end of the clamping cone 784 are preferably arranged offset to each other. The longitudinal slits enable a circumferential and, consequently, a radial compressibility of the clamping cone 784.

The contact body 785 comprises a central conical inner passage with a maximal diameter, which is smaller than the maximal outer diameter of the clamping cone 784, and with a minimal diameter, which is slightly larger than the minimal outer diameter of the clamping cone 784. The coni formed by the inner passage of the contact body 785 and by the outer shape of the clamping cone 784 have the same cone angles.

When inserting the clamping cone 784 into the inner passage of the contact body 785, the diameter of the clamping cone 784 is continually reduced due to the conical shapes of the clamping cone 784 and of the inner passage of the contact body 785. As a result, the crimping tube 783 is clamped together with the electric conductors 782 onto the pressure resistant tube 781 by the clamping cone 784. At the same time, a clamping force is established between the clamping cone 784 and the contact body 785. Consequently, a reliable low resistance electric contact is established between the contact body 785, the clamping cone 784, the crimping tube 783 and the crimped electric conductors 782.

The clamping cone 784 abuts a metallic pressure ring 780, which is arranged, along the axial direction, between the clamping cone 784 and the stress cone 761. In the region of the stress cone 761 , the metallic pressure ring 780 also abuts an end face of the electric insulation layer 515. The shape of the metallic pressure ring 780 in combination with the shape of the high voltage shield 762 is optimized with respect to low electric field stress at the interfaces of the electric insulation layer 515, the stress cone 761 , the socket insulator 763 and the conductor socket 792.

The fiber optic cable 511 of the electric / optic system 510, which can contain one or more optic fibers, is guided through the central inner passage of the pressure resistant tube 781 and are coiled to several windings 789 arranged in a hollow space between the contact body 785 and a fiber optic connector unit 810. From the windings 789, the fiber optic cable 511 extends into the fiber optic connector unit 810. The fiber optic connector unit 810 contains a pluggable fiber optic connector system, which connects the fiber optic cable 511 of the electric / optic system 510 with a further fiber optic cable 511 extending on the top side of the conductor socket 792 (in the view according to figure 13). The windings 789 provide enough fiber optic cable length for the coupling and the decoupling of the male and female parts of the connector element 764, e.g. for first assembly or repair work.

A first bordering element 788 is provided in the hollow space between the contact body 785 and an optic connector unit 810, in order to prevent too high flections of the fiber optic cable 511. The first bordering element 788 is fixed to the contact body 785 by means of screws 663. A second bordering element 791 is also arranged in the hollow space between the first bordering element 788 and the optic connector unit 810 and likewise serves to prevent too high flections of the fiber optic cable 511.

With its top face (in the view of figure 13), the conductor socket 792 is fixed to the high voltage and fiber optic rotary joint 702 shown in figure 11 by means of screws 663 in a gas- tight manner achieved by O-ring seals 723. The fiber optic cable 511 extends through an opening in the conductor socket 792. The respective opening is sealed in a gas-tight manner by means of a fiber optic cable seal 795.

Figure 14 - Fiber optic connector unit 810

Figure 14 shows a detailed view of the fiber optic connector unit 810 which has been introduced further above with respect to figure 13. The fiber optic connector unit 810 is shown in the coupled state in figure 14. The male part of the fiber optic connector unit 810 is represented by the combination of a plug pin 802 and a fiber centering tube 803, which together guide the fiber optic cable 511 extending through a central opening of the plug pin 802 and the fiber centering tube 803.

The female part of the fiber optic connector unit 810 is represented by the combination of a fiber connector socket 806, a fiber centering tube 805 and a centering tube 804, which together guide the fiber optic cable 511 extending through a central opening of the fiber connector socket 806, the fiber centering tube 805 and the centering tube 804.

In order to achieve minimal signal attenuation of the optical signals being transferred through the fiber optic connector unit 810, the optical fiber or fibers of the fiber optic cable 511 are precisely centered and fixed in the fiber centering tubes 803 and 805 and are precisely aligned by the centering tube 804 during the insertion process. The centering and alignment are preferably carried out with tolerances in the micrometre range and below depending on the optical fiber type applied.

For the insertion and later fixation of the optic fiber of the fiber optic cable 511 into the fiber centering tubes 803 and 805, various protection layers and coatings might have to be removed, e.g. when using a single mode glass fiber optic cable.

By for example providing a longitudinal slit in the centering tube 804 and / or by choosing a slightly smaller inner diameter for the centering tube 804 than the outer diameter of the fiber centering tubes 803, 805 (e.g. in the range of a few micrometres), low insertion and withdrawal forces in combination with a precise alignment can be achieved. The end(s) of the optical fiber(s) of the fiber optic cable 511 and the fiber centering tubes 803, 805 are preferably polished, in order to achieve low signal attenuation.

In the region between the fiber centering tubes 803, 805, the two fiber optic cables 511 , of which a first extends through the fiber centering tube 803 of the male part and a second through the fiber centering tube 805 of the female part, abut each other with their respective end faces. The direct physical contact of the abutting end faces of the optic fibers of the male and female parts of the pluggable fiber optic connector unit 810 is advantageously enhanced by a slightly crowned shape of the abutting end faces. A constant contact between the two end faces of the fiber optic cables 511 is ensured by the plug pin 802 which is pressed against the female part by a spring 801. As a result a glass / glass-transition without air is obtained, leading to low signal attenuation in the transition between the two ends of the fiber optic cables 511.

The spring 801 is arranged between the plug pin 802 and the second bordering element 791. In both the coupled and the uncoupled position of the fiber optic connector unit 810, the plug pin 802 is axially aligned by a plug body 800 and by the second bordering element

791. Both the plug body 800 and the second bordering element 791 are fixed to the first bordering element 788 with the help of screws 663 (also see figure 13).

Alignment during the insertion process of the plug pin 802 into the fiber connector socket 806 is facilitated and achieved by the centering of the plug body 800 in the conductor socket

792, by the centering of the plug body 800 in a socket body 807 by complementary conical surfaces, by the centering of the fiber centering tube 803 by the bell-shaped fiber connector socket 806 and by the centering by the centering tube 804.

The fiber connector socket 806 is held in place by the socket body 807 and a base plate 809, which are both fixed to the conductor socket 792 by means of screws 663.

The fiber optic connector unit 810 is adapted to be used for many coupling cycles.

Figure 15 - Multiple fiber optic connector unit 811

Figure 15 shows different views of a possible embodiment of a multiple fiber optic connector unit 811 as an alternative to the fiber optic connector unit 810 shown in figure 14. The multiple fiber optic connector unit 811 serves for simultaneously coupling a plurality of fiber strands of a fiber optic cable 511 .

A possible application for a fiber optic cable 511 with multiple fiber strands concerns for example the optical signal transmission to and from components of the ground station 1 with the help of branch line fiber optic cables 710. These components, such as sensors and drives of e.g. the drum or of the tether guiding system 400 (see further below), can each be connected to a central control unit by means of a branch line fiber optic cable 710.

By providing a coupling for a fiber optic cable 511 that has a plurality of fiber strands, a high signal transfer rate by means of individual fiber strands and / or individual fiber cables between different parts of the wind power station 600 and the ground station 1 can be achieved, which allows achieving a precise control of the flight path by sensors and actors as well as a high signal bandwidth for signal sending and reception by the wind power station 600. Alternatively or in addition, the ability of the wind power station 600 to send and receive signals could be applied for a secondary use of the wind power station, e.g. for mobile phone communications, military and / or industrial signal. transmission.

The embodiment shown in figures 15a and 15b allows seven simultaneous fiber optic connections to be present. Of course, also different numbers of connections can be established with a different geometrical arrangement of the individual fiber optic connections.

In figure 15a, a central cross-sectional view along the axial direction is shown, with a fiber connector socket 806' containing a multitude of fiber centering tubes 805 in combination with centering tubes 804 and fiber optic cables 511 in the female part of the connector unit shown in the upper part of figure 15a. A plug body 800' containing a multitude of plug pins 802' in combination with fiber centering tubes 803 and fiber optic cables 511 is shown in the lower part of figure 15a, representing the male part of the connector unit.

To provide optimal signal transmission with low attenuations, the plug pins 802' press the abutting surfaces of the fiber centering tubes 803 against the fiber centering tubes 805 by means of springs 80T.

The springs 80T are mounted between a stop surface of the plug pin 802' and the second bordering element 79T in each case. In both the coupled and the decoupled state of the multiple fiber optic connector unit 811 , the plug pins 802' are axially aligned by the plug body 800' and the second bordering element 79T. The plug body 800' and the second bordering element 791 ' are fixed to the first bordering element 788 by means of screws 663.

The fiber connector socket 806' is held in place by the socket body 807' and the base plate 809', which are both fixed to the conductor socket 792' by means of screws 663.

Figure 15b shows a cross-sectional view A-A of the multiple fiber optic connector unit 811 in a plane that extends perpendicularly to the axial direction.

Figure 16 - Combined high voltage and fiber optic connector 701 in the decoupled state

For better visibility of the male and the female parts of the combined high voltage and fiber optic connector 701 , the connector 701 is shown in a decoupled state in Figure 16.

Figure 17 - Combined high voltage and fiber optic connector 701' with electric functional grading material and insulation fixation

Figure 17 shows a different embodiment of the combined high voltage and fiber optic connector 701' than shown in e.g. figures 12 and 13, featuring a non-linear electric field grading material 797 and a fixation of the electric insulation layer 515'.

The application of a non-linear resistive electric field grading material like zinc oxide or silicon carbide allows to minimize the electric field stress in the combined high voltage and fiber optic connector 70T and, therefore, to enhance operational reliability. The electric resistance of these materials change in a non-linear way with the applied voltage. Especially at transient voltages introduced by electrical switching operations or induced voltages - not direct strikes - from lightning, the non-linear electric field grading material 797 can reduce the maximal electric field stress in the combined high voltage and fiber optic connector 70T.

In the present embodiment of a pluggable connector 70T, the non-linear electric field grading material 797 is applied between the electric insulation layer 515' and the stress cone 76T as well as between the semi-conductive buffer layer 516 and the deflector 760' as shown in figure 17.

Another difference as compared with the embodiments of figures 12 and 13 is the fixation of the electric insulation layer 515' at the metallic pressure ring 780'. According to the present embodiment, the fixation is established by a threaded connection, as shown in Figure 17. Also other types of fixations, e.g. with small screws placed at locations with very low or no electric field, are possible.

The advantage of a fixation of the electric insulation layer 515' at the metallic pressure ring 780' is to prevent a pull-back of the electric insulation layer 515' due to thermal expansion and contraction caused by electric loads as well as due to repetitive mechanical loads. A pull-back of the electric insulation layer 515 out of the metallic pressure ring 780 in a design as shown in figure 13 could lead to voids which can result in partial discharge and electric breakdown.

Figure 18 - High voltage and fiber optic rotary joint 702 Figure 18 shows a central cross-sectional view of the high voltage and fiber optic rotary joint 702.

The high voltage and fiber optic rotary joint 702 provides an electrical and fiber optic connection with unlimited rotational capabilities between the combined high voltage and fiber optic connector 701 rotating with the wind power station 600 (shown in the upper part of figure 11) and the combined high voltage and fiber optic connector 701 not rotating with the wind power station 600 (shown in the lower part of figure 11). In figure 18, parts of the conductor sockets 792 of the two high voltage and fiber optic connectors 701 mentioned above and described with respect to e.g. figures 13 and 14 are visible.

The electrical part and the optical part of the high voltage and fiber optic rotary joint 702 are arranged concentrically with respect to the same rotational axis.

The part of the high voltage and fiber optic rotary joint 702 rotating with the wind power station 600 comprises an inner contact cylinder 830, which is fixed to the conductor socket 792 of the combined high voltage and fiber optic connector 701 by means of screws 663. The part of the high voltage and fiber optic rotary joint 702 not rotating with the wind power station 600 comprises an outer contact cylinder 826, which is fixed to a base cylinder 820 by means of screws 663.

The inner contact cylinder 830 and the outer contact cylinder 826 form elements of the electrical part of the high voltage and fiber optic rotary joint 702. Further elements of the electrical part of the high voltage and fiber optic rotary joint 702 are the contact elements 828, which are attached to the outer contact cylinder 826, as well as the base cylinder 820. The base cylinder 820 is fixed to the conductor socket 792 by means of screws 663.

Between the inner contact cylinder 830 and the outer contact cylinder 826, electric current transfer is ensured by means of sliding contacts in the form of the contact elements 828. The inner contact cylinder 830, the outer contact cylinder 826 and the contact elements 828 form a high voltage rotary joint contact system 837 for unlimited turns.

To prevent possible electrically conductive dust generated by the operation of the contact elements 828 to enter the area where gas-to-solid-insulation interfaces can be polluted, a rotary joint seal 829 can be provided between the outer contact cylinder 826 and the inner contact cylinder 830, with a material pairing that shows very low friction and wear. The rotary joint seal 829 can be fixed to the outer contact cylinder 826. By applying a sliding contact material for the contact elements 828 like e.g. silver alloy with sliver graphite mixtures or gold on gold alloy with a very long lifetime, a rotary joint can be achieved that is practically maintenance-free.

To ensure gas-tightness of the gas-insulated part of the electric / optical rotary joint 700 towards the interface between the male and the female part of the combined high voltage and fiber optic connector 701 , the fixations of the inner contact cylinder 830 and the base cylinder 820 to the respective conductor sockets 792 are preferably sealed by means of Coring seals 723.

In operation, the high voltage and fiber optic rotary joint 702 usually is on a high voltage potential, while e.g. the rotary joint cylinder 737, the connector fixation plate 740, the rotary connector fixation plate 715 and the seal spring limiter 730 of the electric / optical rotary joint 700 are on ground potential (see figure 11).

The outer shape of the high voltage and fiber optic rotary joint 702 is designed in such a way, that the electric field strength between the fiber optic rotary joint 702 on high voltage potential and the parts of the electric / optical rotary joint 700 that are on ground potential is kept low and particularly below a maximum field strength value. For this purpose, e.g., the radii of various edges can be maximized and / or the distances towards the grounded parts can be kept maximal. The maximum tolerable field strength value is usually given by the insulation properties of the electric system and particularly depends on the electric insulation capability of the insulating parts and on the maximally occurring stationary and transient voltages in operation, in further consideration of a certain safety factor.

The fiber optic system of the high voltage and fiber optic rotary joint 702 rotating with the wind power station 600 includes the fiber optic cable 511 with windings 789 shown in the upper part of figure 18, a fiber connector 834, a fiber connector cylinder 832 as well as parts of a fiber optic rotary joint 825.

The fiber optic cable 511 shown in the upper part of figure 18 is protected against high flection by a rotating upper guiding element 836, which is fixed to the inner contact cylinder 830 with screws 663. The windings 789 provide sufficient spare length of the fiber optic cable for being coupled to a fiber socket 833 attached to the fiber connector cylinder 832 by means of the fiber connector 834 before the fiber connector cylinder 832 is moved into the inner contact cylinder 830 during assembly of the fiber optic rotary joint 702. Thus, the fiber optic cable 511 is connected to the fiber connector cylinder 832 by means of the fiber connector 834, which can be coupled to the fiber socket 833. In order to prevent high flection of the fiber optic cable 511 in the region of the fiber connector 834, a rotating lower guiding element 835 is provided at the fiber connector cylinder 832 in the region around the fiber socket 833.

The fiber connector cylinder 832 provides a flange for the mounting of a fiber socket 833, in order to establish a pluggable connection for the fiber optic cable 511 with a fiber connector 834 to the rotating part of the fiber optic rotary joint 825. Internally of the fiber connector cylinder 832, the fiber optic signal is guided by a fiber optic cable (not shown) and other optical components (not shown) to the rotating part of the fiber optic rotary joint 825. The fiber connector cylinder 832 provides internal space for the arrangement of the fiber optic cable 511 on the inside of the fiber connector cylinder 832 as well as for optical components preparing the optical signal for the passage from the rotating part of the fiber optic rotary joint 825 to the non-rotating part of the fiber optic rotary joint 825. With respect to figure 18, the lower part of the fiber connector cylinder 832 is fixed to the upper and inner part of the fiber optic rotary joint 825, which is the part of the fiber optic rotary joint 825 which is rotating with the wind power station 600.

The fiber optic rotary joint 825 can be constructed and designed for example as disclosed in one of the documents US 5,157,745 A or US 8,965,151 B1 , the contents of which are hereby included by reference in their entireties. The fiber optic rotary joint 825 has a part that rotates with the wind power station 600 and a part that does not rotate with the wind power station 600, but with the tether 500.

In the direction from the wind power station 600 to the tether 500, the optic signal passes from the windings 789 shown in the upper part of figure 19 through the fiber connector cylinder 832 and the fiber optic rotary joint 825 to the windings 789 of the fiber optic cable 511 shown in the lower part of figure 19. From there, the optic signal is transferred via the fiber optic cable 511 to the combined high voltage and fiber optic connector 701 shown in the lower part of figure 11.

In the region of the windings 789 shown in the lower part of figure 19, i.e. of the windings in the non-rotating part of the fiber optic rotary joint 702/702', a non-rotating upper guiding element 823 is provided, in order to prevent high flection of the fiber optic cable 511 . The non-rotating upper guiding element is fixed to the outer contact cylinder 826 by means of screws 663. In the region where the fiber optic cable 511 enters the combined high voltage and fiber optic connector 701 in the lower part of figure 19, high flection is prevented by a non-rotating lower guiding element 821 , which is fixed to the base cylinder 820 by means of screws 663.

The cylindrical outer surface of the fiber optic rotary joint 825 is fixed to the outer contact cylinder 826 by means of e.g. threaded connections (not shown). The upper part of the fiber optic rotary joint 825 facing towards the fiber connector cylinder 832 comprises a peripheral area which is not rotating and a central area which is rotating with the wind power station 600. The rotating central area of the fiber optic rotary joint 825 rotating with the wind power station 600 is connected to the rotating connector cylinder 832. The non-rotating peripheral area of the upper side of the fiber optic rotary joint 825 is fixed to the cylindrical outer surface of the fiber optic rotary joint 825. High precision bearings between the rotating and the nonrotating parts of the fiber optic rotary joint 825 provide an optimal function of the fiber optic rotary joint 825. The cylindrical outer surface of the connector cylinder 832 rotating with the wind power station 600 is clamped by means of a circumferential clamping pad 831 providing a separable fixation of the connector cylinder 832 to the inner contact cylinder 830. The clamping pad 831 may be made of a soft deformable pad of e.g. microcellular rubber. The separable fixation is particularly advantageous for assembly or disassembly of the high voltage and fiber optic rotary joint 702 in the production phase.

Figure 19 - High voltage and fiber optic rotary joint 702 with fiber optic branch lines 710

Figure 19 shows a central cross-sectional view of a possible embodiment of the high voltage and fiber optic rotary joint 702' for the unlimited rotatable fiber optic connection of multiple fibers as well as for unlimited rotatable electrical connection. The advantage of the application of multiple fiber optic cables 511 has already been mentioned in the description with respect to figures 11 and 15: The advantage particularly concerns the optical signal transmission to and from components of the wind power station 600 and / or the ground station 1 with the help of branch line fiber optic cables 710. These components can be separated from each other by e.g. freely rotatable joints, and one branch line fiber optic cable 710 may end in one component connected to the rotatable joint, and another branch line fiber optic cable 710 may end in the other component connected to the rotatable joint. For this purpose, the high voltage and fiber optic rotary joint 702' shown in figure 19 offers the possibility of guiding branch line fiber optic cables 710 in or out of the electric system of the electric / optic system 510.

Since the fiber optic cables 511 and specifically the branch line fiber optic cables 710 comprise electrically insulating materials like glass and plastics (among others), no significant influence on the electric insulation capability of the electric insulation system is to be expected.

By the provision of multiple fiber optic cables 511 in the electric / optic system 510 and of a fiber optic rotary joint 825' that is suitable for multiple optic fibers as well as by providing respective lateral openings for the passage of the branch line fiber optic cables 710 in the base cylinder 820' and in the inner contact cylinder 830', different parts of the wind power station 600 and / or the ground station 1 can be connected by fiber optic signal transmission. The lateral openings in the base cylinder 820' and the inner contact cylinder 830' can be e.g. round holes with rounded edges, in order to prevent scrubbing of the fibers and high electric field strengths.

The various guiding elements of the high voltage fiber optic rotary joint 702', such as the non-rotating lower guiding element 82T, the non-rotating upper guiding element 823', the rotating lower guiding element 835' as well as the rotating upper guiding element 836' of course have to be adapted to the space requirements of the additional fiber optic cables 511.

Additionally, the fiber connector cylinder 832' as well as the conductor socket 792' have to be dimensioned and designed with regard to the application of multiple fiber optic cables 511 and branch line fiber optic cables 710.

Figure 20 - Electric contact systems for the high voltage and fiber optic rotary joint 702 - 1

Figure 20 shows different embodiments of possible high voltage rotary joint contact systems 837 of the high voltage and fiber optic rotary joint 702 for the electric current transfer in the high voltage and fiber optic rotary joint 702 by means of sliding contacts.

In figure 20a, a cross-sectional view of a high voltage rotary joint contact system 837 is shown with a sliding contact 840', which is pressed towards the inner contact cylinder 830 by means of a contact spring 838' in the form of a helical spring. The sliding contact 840' electrically connects the inner contact cylinder 830 to the outer contact cylinder 826 via a contact element and a flexible electric conductor 839. The ends of the flexible electric conductor 839 are fixed to the sliding contact 840' and to the outer contact cylinder 826 by means of screws 663. The sliding contact 840' is radially guided with respect to its longitudinal axial direction by a guiding ring 841.

The application of a sliding contact 840' between the inner contact cylinder 830 and the outer contact cylinder 826 allows providing an unlimited rotatable electric connection with low electric resistance.

To increase the electric current transfer capability of the high voltage rotary joint contact system 837, several sliding contacts 840' can be arranged along the circumference of the fiber optic rotary joint 702, and / or on different axial levels of the inner contact cylinder 830.

In figures 20b1 and 20b2, perpendicularly oriented cross-sectional views of a different embodiment of a high voltage rotary joint contact system 837' are shown with different sliding contacts and pressure springs than shown in figure 20a. The high voltage rotary joint contact system 837' as shown in figure 20b1 and 20b2 features larger electric contact surfaces of the sliding contacts 840", which allows a higher electric current transfer.

In figure 20b1 , a cross-sectional view of the high voltage rotary joint contact system 837' is shown, with a sliding contact 840" pressed towards the inner contact cylinder 830 by a contact spring 838" in the form of a leaf spring. The sliding contact 840" electrically connects the inner contact cylinder 830 to the outer contact cylinder 826' via a contact element and a flexible electric conductor 839. The ends of the flexible electric conductor 839 are fixed to the sliding contact 840" and to the outer contact cylinder 826' by means of screws 663. The sliding contact 840" is laterally guided with respect to its central longitudinal direction by limiting plates 842.

To increase the electric current transfer capability of the high voltage rotary joint contact system 837', several sliding contacts 840" can be arranged along the circumference of the fiber optic rotary joint 702, and / or on different axial levels of the inner contact cylinder 830, as exemplary shown in figure 19b2 with two axial layers.

In figure 20c, a different embodiment of a high voltage rotary joint contact system 837" is shown, with a different lateral limitation of the movement of the sliding contacts 840" and with a connection plate 843 for achieving a large contact surface for the electrical connection via the sliding contact 840".

In figure 20c, a cross-sectional view of a of the high voltage rotary joint contact system 837" is shown, with sliding contacts 840"' that are pressed towards the inner contact cylinder 830 by means of respective contact springs 838"' in the form of leaf springs. Each of the sliding contacts 840'" electrically connects the inner contact cylinder 830 to the outer contact cylinder 826" via a contact element, a connection plate 843 and a flexible electric conductor 839. The connection plate 843 and the contact spring 838'" are fixed to the sliding contact 840'" by means of screws 663. One end of each of the flexible electric conductors 839 is fixed to a respective connection plate 843 by means of e.g. a crimp contact or a solder contact, the other end is connected to the outer contact cylinder 826" by means of a screw 663. The sliding contacts 840'" shown in figure 20 are laterally guided with respect to their central longitudinal direction by contact spring limiters 844, which are part of the outer contact cylinder 826".

The motion limitation of the sliding contacts 840', 840", 840'" along the radial direction of the high voltage rotary joint contact system 837, 837', 837" allows a controlled insertion of the inner contact cylinder 830 into the outer contact cylinder 826, 826', 826" during assembly of the fiber optic rotary joint 702, 702'.

Figure 21 - Electric contact systems for the high voltage and fiber optic rotary joint 702 -

Figure 21 shows further different embodiments of possible high voltage rotary joint contact systems 837'", 837"", 837'"" for the electric current transfer in the high voltage and fiber optic rotary joint 702.

Figure 21a shows an embodiment of a possible high voltage rotary joint contact system 837'" with a helical contact spring 838"" and a sliding contact 840"" which is here formed by multiple leaf spring contacts fixed to the outer contact cylinder 826"’.

The leaf spring contacts of the sliding contact 840"", which are preferably circumferentially arranged around the inner contact cylinder 830, are pressed radially inwards by the helical contact spring 838"", in order to establish a rotary electrical contact with low electric resistance between the inner and the outer contact cylinders 830, 826'". In figure 21 a2, a part of the circumference of the sliding contact 840"" together with a part of the helical contact spring 838"" is shown, illustrating a possible design of the finger contacts of the sliding contact 840"".

In figure 21a3, a top view of a single finger contact of the sliding contact 840"" together with a part of the inner contact cylinder 830 is shown, illustrating a possible cross-sectional shape of a finger contact of the sliding contact 840"".

Figure 21b shows a further different embodiment of a possible high voltage rotary joint contact system 837"" with a contact spring 838"'" in the form of finger-like leaf spring, arranged in a way similar to the finger contacts of the sliding contact 840"" shown in figure 20a2. The electric contact to the inner contact cylinder 830 is established by a sliding contact 840.. The sliding contact 840""' is fixed to the free end of the finger-like contact spring 838. , which is fixed to the outer contact cylinder 826'" and establishes an electrical rotary joint contact to the inner contact cylinder 830 with low electric resistance.

Figure 21 c shows another further embodiment of a possible high voltage rotary joint contact system 837'"" with two contact springs 838'"" in the form of finger-like leaf springs, similar to the contact system shown in figure 20b. The contact springs 838'"" are fixed to the outer contact cylinder 826"". The application of a second contact spring 838. together with the corresponding sliding contacts 840. allows further increasing the current transfer capability of the unlimited rotatable electrical connection in the high voltage and fiber optic rotary joint 702.

For an easy insertion of the inner contact cylinder 830' into the outer contact cylinder 826"" during assembly of the fiber optic rotary joint 702, the shape of the inner contact cylinder 830' as well as the positioning and dimensioning of the clamping pad 83T and of the fiber connector cylinder 832' have to be adapted accordingly, in order to allow an easy insertion and enough place for the inner contact springs 838'"" and their corresponding sliding contacts 840"'".

Figure 22 - High voltage and fiber optic rotary joint 702 in decoupled state

Figure 22 shows the high voltage and fiber optic rotary joint 702 in decoupled state and ready for assembly. The high voltage and fiber optic rotary joint 702 in the coupled or assembled state has already been shown in figure 18.

From figure 22, the advantage of having the windings 789 of the fiber optic cable 511 inside of the fiber optic rotary joint 702 can be understood: Due to the pluggable connection between the fiber connector 834 and the fiber socket 833 and due to the spare length of the fiber optic cable 511 owing to the windings 789, the fiber optic connection to the fiber connector cylinder 832 can already be established prior to the assembly of the high voltage and fiber optic rotary joint 702.

Figure 22 also shows the clamping pad 831 and the rotary joint seal 829 in their relaxed states.

Figure 23 - Combined optic and electric power interface 851

Figure 23a shows a cross-sectional view of the combined optic and electric power interface 851 at the wind power station 600 (see figures 4b and 4c). In this combined optic and electric power interface 851 , the fiber optic cables 511 coming from the wind power station 600 are brought together with the high voltage components of the wind power station 600, to be both guided toward the ground station 1 by means of the high voltage cable 850 and the tether 500. In the high voltage cable 850 and in the tether 500, the fiber optic cables 511 are arranged in the center of the electric conductors, i.e. in the center of the electric / optic system 510.

A comparatively large number of bending cycles occurs to the high voltage cable 850 at the interface between the rotating wind power station 600 and the electric / optical rotary joint 700, compared to a comparatively low number of bending cycles occurring to the tether 500 at spooling operations of the drum 200. In addition, the usually smaller bending radii of the high voltage cable 850 require a design to withstand to higher cyclic fatigue strain than the larger bending radius of the tether 500 at the drum 200. Consequently, the high voltage cable 850 can contain an electric / optic system 510, which is specifically designed for these fatigue life requirements.

The different fatigue life requirements of the high voltage cable 850 and the tether 500 can result in a specific design adaptation for each of the integrated electric / optic systems 510. Among other parameters, the specific design can include e.g. a specific helical winding angle of the electric conductors 513, 517. Other measures to further increase the fatigue life of the high voltage cable 850 will be shown with respect to figure 25.

The combined optic and electric power interface 851 has an e.g. cuboid or cylindrical outer shape and a preferably gas-tight inner space. The combined optic and electric power interface 851 comprises a housing with a circumferential sidewall 856, a bottom plate 853 and a cover plate 855. The bottom plate 853 is fixed, e.g. from the inside to an outer wall of the fuselage 606 (see figure 2) of the wind power station 600, by means of heavy load threaded connections 672. The bottom plate 853 as well as the cover plate 855 are fixed to the sidewall 856 by means of further heavy load threaded connections 672. At the interfaces between bottom plate 853, cover plate 855 and sidewall 856, the inner space of the combined optic and electric power interface 851 is preferably sealed by means of O-ring seals 723. The gas-tightness of the combined optic and electric power interface 851 serves to protect the components arranged in the inner space from environmental impacts like dust, humidity and aggressive gases. Additionally it allows the provision of an electrically insulating gas in the inner space of the combined optic and electric power interface 851 , in order to reduce the necessary electric insulating distances by increasing the breakdown voltage of the respective electrode arrangements, similar as in the electric / optical rotary joint 700 shown in figure 11.

To further reduce the necessary electric insulating distances and to minimize the necessary volume of the combined optic and electric power interface 851 , the electrically insulating gas in the inner space can have a higher pressure than the ambient pressure. Suitable electrically insulating gases are for example pressurised clean air, carbon dioxide or gas mixtures containing fluorine ketone, fluorine nitrile or sulphur hexafluoride (SF₆). Suitable pressures are in the range of a few bars up to approx. 10 to 15 bar above ambient pressure.

The evacuation and filling of the combined optic and electric power interface 851 with the electrically insulating gas can be carried out by means of a gas exchange valve 741. The pressure control of the electrically insulating gas, in order to detect leakage or monitor for correct filling pressure is provided by a gas density sensor 742 transmitting the measured signals via a signal cable 743.

In order to monitor the dielectric integrity of the combined optic and electric power interface 851 , a partial discharge sensor 731 can be provided in the inner space of the combined optic and electric power interface 851, e.g. mounted at the cover plate 855. The electromagnetic partial discharge signals caused from electrical insulation defects in the ultra-high frequency range are picked up by the partial discharge sensor 731 and transmitted via the signal cable 733 to a monitoring system which allows defect diagnosis and provides information for decisions on countermeasures. The partial discharge sensor 731 is mounted in a gas-tight way with a circumferential seal 732.

The combined optic and electric power interface 851 connects a high voltage cable 866, that comes from the wind power station 600, to the high voltage cable 850, in order to electrically connect the wind power station 600 to the tether 500 and, thus, to the ground station 1. For this purpose, the combined optic and electric power interface 851 comprises a pluggable high voltage connector 852 and a combined high voltage and fiber optic connector 701. Electric energy and optical signals are transferred between the combined high voltage and fiber optic connector 701 and the electric / optical rotary joint 700 by means of the high voltage cable 850. For connecting the fiber optic cables 511 coming from the fiber optic connector 701 via the high voltage cable 850 to further fiber optic cables 511 of the wind power station 600, connectors 711 are provided within gas-tight feedthroughs 712. The gas-tight feedthroughs 712 are mounted in a flange cover 854 that covers an opening in the sidewall 856 and is fixed to the sidewall 856 by means of heavy load threaded connections 672 and sealed with an O-ring seal 723.

The high voltage cable 866 that serves for the connection of the electric components of the wind power station 600 to the pluggable high voltage connector 852 can be a standard cable, in particular a standard medium- or high voltage cable, with normal flexibility, since this cable usually is in a fixed position within the fuselage 606 of the wind power station 600 and is not exposed to any excessive mechanical loads.

In the inner space of the combined optic and electric power interface 851, the high voltage connector 852 and the combined high voltage and fiber optic connector 701 are electrically connected to each other by means of a contact socket 862 and a contact pin 865. The contact socket 862 is attached to the high voltage connector 852. The contact pin 865 is attached to the combined high voltage and fiber optic connector 701 via an electro-optic separation cylinder 867. The combination of the contact socket 862, the contact pin 865 and the electro-optic separation cylinder 867 enables an easy assembly of the electrical connection between the high voltage connector 852 and the combined high voltage and fiber optic connector 701. Furthermore, an easy separation of the electric system and the fiber optic cables 511 is provided in this way. The assembly process of the electric and fiber optic system of the combined optic and electric power interface 851 described below, can best be carried out with the cover plate 855 not mounted. After the assembly process, in a final step, the cover plate 855 can be mounted and fixed and the male parts of the combined high voltage and fiber optic connector 701 and the high voltage connector 853 can be plugged as well as the connectors 711 of the fiber optic cables 511 coming from e.g. the wind power station 600.

In a first assembly step, the female part of the combined high voltage and fiber optic connector 701 can be fixed in the respectively provided opening of the bottom plate 853 and the fiber optic cables 511 coming from the combined high voltage and fiber optic connector 701 are guided through the lower opening of the electro-optic separation cylinder 867 and further guided through the side opening of the electro-optic separation cylinder 867.

In a second assembly step, the electro-optic separation cylinder 867 is attached to the combined high voltage and fiber optic connector 701 by means of screws 663.

In a third assembly step, the fiber optic cables 511 are then ready for being equipped with connectors 711 , which can then be connected to the gas-thigh feedthroughs 712 on the inside of the combined optic and electric power interface 851 mounted in the flange cover 854.

In a fourth assembly step, the female part of the high voltage connector 852 can be fixed in the respectively provided opening in the sidewall 856

In a fifth assembly step, the contact socket 862 is fixed to the high voltage connector 852 by means of screws 663.

In a sixth assembly step, the contact pin 865 is inserted into the contact socket 862 and fixed by means of screws 663 to the electro-optic separation cylinder 867. The contact socket 862 comprises socket contacts 863 for establishing a low resistance electrical contact between the contact socket 862 and the contact pin 865.

In figure 23b, a cross-sectional view of the contact pin 865 in a plane perpendicular to the one of figure 23a is shown. The combined optic and electric power interface 851 can be provided e.g. at the airborne wind power station 600, but also at the ground station 1 in the energy and signal interface 20.

Figure 24 - High voltage connector 852

Figure 24 shows a possible embodiment of the high voltage connector 852 together with a possible embodiment of a flexible high voltage cable 866' for the pluggable connection of the electric part of the combined optic and electric power interface 851 as shown in figure 23a.

For connecting the electric components and in particular the electric power generator(s) (601) of the wind power station 600 to the combined optic and electric power interface 851, a flexible high voltage cable 866, 866' in combination with a standard pluggable high voltage connector, which can for example be designed as disclosed in DE 39 35 360 A1 , can be applied.

In order to achieve very high flexibility with small bending radii of the high voltage cable 866’, a modified version of the electric / optic system 510 could for example be used as shown in figure 24. The design of the high voltage cable 866' can for example be similar as the one of the electric / optic system 510 of the tether 500 shown in figure 12, comprising an elastic core 512. The fiber optic cables 511 in the center of the elastic core 512 can be omitted in certain embodiments.

By combining a low helical pitch angle a for the electric conductors 513, 517 with a highly flexible electric insulation material like a rubber compound for the electric insulation layer 515 and with a highly flexible semi-conductive material like a special rubber compound for the semi-conductive layers 514, 516, a certain flexibility can be achieved for the high voltage cable 866'. The helical pitch angle a is illustrated in figure 25.

A combination of a less flexible electric insulation material like a cross-linked high density polyethylene XLPE, respectively a semi-conductive XLPE material for the semi-conductive layers, with a thermal treatment during the bending process to a small bending radius would also allow to lay the above described high voltage cable 866' in small radii within the fuselage 606. An electrically conducting high voltage contact cylinder 881 serves to transfer the electric current of the high voltage electric conductors 513 of the high voltage cable 866' to the contact socket 862 of the combined optic and electric power interface 851.

The fixation of the contact socket 862 to the high voltage contact cylinder 881 can be established with screws 663.

The further features of the high voltage connector 852 are the same or similar as in the combined high voltage and fiber optic connector 701 shown in figure 12.

Figure 25 - Conductor designs for the high voltage cable 850

Figure 25 shows different embodiments of the electric conductor arrangement for increasing the fatigue and wear resistance of the electric conductors 513, 517 of the tether 500 and / or of the high voltage cable 850 and / or of the high voltage cable 866' and in particular of their respective electric / optic system 510.

The special electric conductor arrangement as shown in figure 25 in combination with e.g. additional wear protection layers and / or wear protection elements serves to prevent fretting of electric conductors lying next to each other under cyclic movements induced by cyclic strain and / or bending of the tether 500 and / or of the high voltage cable 850 and / or of the high voltage cable 866'. The prevention of fretting of the electric conductors leads to a significantly increased fatigue lifetime.

In figure 25a, a longitudinal side view illustrating the arrangement of the electric conductors 513, 517, represented by a helically wound electric conductor 890, is shown. The electric conductor 890 is helically applied on an elastic core 512 with a helical pitch angle a. The electric conductor 890 is wound on the elastic core 512 in alternating order with longitudinal elastic buffers 891 , which prevent direct contact of the windings of the electric conductor 890. The longitudinal elastic buffers 891 prevent fretting of the electric conductor 890 by separating the windings of the electric conductor 890.

The longitudinal elastic buffers 891 can be in the form of an elongated strand similar to the electric conductors 890.

In order to prevent direct contact of the surfaces of the electric conductors 890 when applying several layers of electric conductors 890, the application of a low friction elastic buffer layer 892 is shown in figure 25b.

The material of the longitudinal elastic buffer 891 and / or the material of the low friction elastic buffer layer 892 could for example be a low surface friction thermoplastic material like polytetrafluoroethylene PTFE or polyamide 6 also known as Nylon^®.

The electric conductor 890 shown in figure 25 represents the electric conductor 513 applied on the elastic core 512. The electric conductors 890 can e.g. represent the electric conductor 517 applied on the semi-conductive buffer layer 516 of the electric insulation layer 515.

Figure 26 - Guiding and adjusting system 330

Figure 26 shows a top view of the guiding and adjusting system 330 together with the tether guiding system 400, for the guiding of the tether 500 and therefore also of the wind power station 600, in order to land the wind power station 600 precisely and safely on the landing support 300 (see figure 2).

For landing the wind power station 600, the position of the landing support 300 relative to the wind power station 600 needs to be continuously adjusted and optimized, which is carried out by means of respective flight manoeuvres of the wind power station 600 as well as by means of drives in the ground station 1. The drives in the ground station 1 are controlled with the help of data measured by sensors.

For this purpose, important measurement data is provided by the guiding and adjusting system 330 which measures the position of the tether 500 in relation to the landing support 300, by the wind measurement system 401 which measures the wind speed and / or direction at the level of the ground station 1 to know the optimal landing direction, by the position, direction and velocity measuring system 605 of the wind power station 600 to know the actual position and direction of the wind power station 600, and by the position encoders of various drives of the rotary table 50, the drum 200, the rotary plate 320 and the tether guiding system 400. With the help of these measurement data, the movable elements of the ground station 1 can be optimally positioned during retrieval of the wind power station 600. In order to land the wind power station 600 under optimal conditions, the wind power station 600 and, therefore, also the tether 500 are preferably positioned relative to the ground station 1 in a direction parallel or anti-parallel to the actual wind direction, wherein the wind direction at the level of the ground is considered.

Immediately before landing, the landing support 300 together with the guiding and adjusting system 330 are preferably positioned in the direction of the tether 500, such that the landing support 300 is facing towards the wind power station 600.

As explained in the description of figure 1, the landing support 300 can be positioned optimally along the circular tracks 301 in relation to the drum 200 and with respect to the wind direction. This positioning is achieved by means of the landing support drive 306 and a rotary encoder 308. The landing support drive 306 is powered and controlled via a power and signal cable 309.

The guiding and adjusting system 330 is adapted to measure the exact position of the tether 500 in relation to an outer surface 336 of the guiding and adjusting system 330, in order to detect and measure a possible misalignment of the tether 500 and the landing support 300 during the retrieving phase of the wind power station 600. This measurement data enables to adjust the drum 200, with the help of the drives in the ground station 1 and by means of respective flight adjustments of the wind power station 600, to optimally position the wind power station 600 and, thus, the tether 500 in relation to the adjusting system 330 for final retrieval of the wind power station 600 onto the landing support 300.

The outer surface 336 of the guiding and adjusting system 330 is shaped with rounded contours, in order not to damage the tether 500 in the case of contacts of the tether 500 with the outer surface 336, which may occur particularly during strong wind conditions. The outer surface 336 of the guiding and adjusting system 330 is mounted on or is part of a frame 335, which provides mechanical stability with regard to cases when the tether 500 touches the guiding and adjusting system 330.

The outer surface 336 of the guiding and adjusting system 330 together with the frame 335 are fixed to the landing support 300 with the help of a fork support 332, the beam support 331 (see also figure 2) and a transverse support 333.

In order to minimise damage to the tether 500 in case of touching under strong wind conditions, the cross sections of the beams of the beam support 331 and of the transverse support 333 preferably have a circular or oval shape in each case.

Figure 27 - Guiding and adjusting system 330 - detail

Figure 27 shows different detailed views of possible embodiments of the guiding and adjusting system 330.

Figure 27a shows a front view of the guiding and adjusting system 330 along the axial direction of the tether 500.

The guiding and adjusting system 330 is V-shaped with two legs and a rounded lower part in-between the legs, in order to facilitate the finding of the initial position of the tether 500 in the landing phase of the wind power station 600. Distance sensors 337 are provided in the guiding and adjusting system 330, in order to detect the position of the tether 500. The distance sensors 337 are preferably adapted to detect the position of the tether 500, when it is in the area between the two legs of the V-shaped guiding and adjusting system 330 as shown in figure 27a and when the tether 500 is outside of these two legs, i.e. in the view of figure 27a on the left or on the right side or above the guiding and adjusting system 330.

After having detected the position of the tether 500, the ground station 1 can be re positioned in such a way that the tether 500 is centrally positioned between the two legs of the V-shaped guiding and adjusting system 330, as shown in figure 27a, in order to prepare an optimal landing of the wind power station 600.

The continuous contour without sharp corners or edges of the outer surface 336 of the guiding and adjusting system 330 prevents damage of the tether 500 in case the tether 500 touches the outer surface 336, for example due to strong winds. The smooth transition between the beam support 331 and the ends of the outer surface 336 prevents the tether 500 to get stuck on the outside of the guiding and adjusting system 330.

Figure 27b shows an embodiment of the guiding and adjusting system 330' with a different shape of the outer surface 336' that provides a tighter mechanical guiding of the tether 500 once it has reached the U-shaped narrow part between the legs of the guiding and adjusting system 330', in case of deviations from the aimed center position, compared to the V- shaped narrow part between the legs of the guiding and adjusting system 330 in figure 27a. Figure 27c shows a cross section of the guiding and adjusting system 330 seen from above. A distance sensor 337 with the active part on the outer surface of the outer surface 336 is shown, connected to a measurement and control unit by the sensor cable 338. Examples of possible distance sensor principles are ultrasonic, capacitive, inductive, laser, optical and radar sensors.

Figure 27d shows a cross section of the guiding and adjusting system 330 shown in figure 27a. A possible configuration of an arrangement of multiple distance sensors 337 is shown, which enables to detect the position of the tether 500 at locations within the center region as well as outside of the center region of the guiding and adjusting system 330, during the landing operation of the wind power station 600.

Figure 27d also shows the fixation of the outer surface 336 on the frame 335 and the fixation of the frame 335 on the fork support 332.

Figure 28 - Top view of cross-section of drum 200 and rotation unit 405

Figure 28 shows a cross-sectional view from above of the drum 200 and of the rotation unit 405 which belongs to the tether guiding system 400. The tether guiding system 400 serves to guide the tether 500, in order to minimize bending and torsion loads acting on the tether 500 and to provide proper winding of the tether 500 onto and from the drum 200.

As already mentioned in the description of figure 2, the tether guiding system 400 can be subdivided into the rotation unit 405 and the linear unit 404. The rotation unit 405 serves to guide the tether 500 to the correct location on the drum 200 during the uncoiling and coiling processes as well as for possible adjustments with regard to an active tether torsion compensation.

The linear unit 404 serves to hold the rotation unit 405 in a position with respect to the axis of the drum 200, which allows an optimal winding of the tether 500 onto the drum body 220. The rotation unit 405 keeps the part of the tether 500 between the tether guiding system 400 and the drum 200 in a straight and essentially orthogonal angle to the rotation axis of the drum 200, when the wind power station 600 flies in e.g. a circular path. The internal guiding of the tether 500 in the rotation unit 405 is optimized to maintain large bending radii during the alignment process between the tether 500 on the wind power station 600 side and the tether 500 on the drum 200 side of the rotation unit 405, in order to minimize bending fatigue of the tether 500.

A first position- and torsion-sensing unit 423 on the side of the drum 200 is adapted to measure the inclination or lateral position of the tether 500 with respect to the longitudinal center axis of the rotation unit 405. The respective information can be used to wind the tether 500 in a well-defined way, i.e. with equally distanced, close windings, onto the drum 200, or to position the tether 500 exactly into a semi-circularly shaped channel of a helical grove provided on the surface of the drum body 220. A second position- and torsion-sensing unit 423 is arranged on the side of the wind power station 600.

The rotation unit 405 comprises two concentrically arranged cylinders, an inner cylinder 418 and an outer cylinder 419. The inner cylinder 418 is fixedly attached to the outer cylinder 419 via fixations 417. In other embodiments, a single cylinder could be provided instead of an inner cylinder 418 and an outer cylinder 419.

The outer cylinder 419 is pivotally held in linear slides 422 via outer cylinder bearings 421. This pivotal arrangement allows passively adapting the elevation angle of the rotation unit 405 with respect to the elevation angle of the tether 500.

The internal guiding of the tether 500 in the guiding system rotation unit 405 is provided by guiding funnels 410, which transfer forces that occur due to the alignment between the wind power station-side of the tether 500 and drum-side of the tether 500 via guiding tube outer supports 415 and guiding tube inner supports 416 to the inner cylinder 418, and from there via the fixations 417 to the outer cylinder 419 and to the linear slides 422.

Inside of the inner cylinder 418, grip rollers 427 are mounted on roller supports 426 each of which is attached on a respective grip guide body 425. Rows of several grip rollers 427 are fixed via their respective roller supports 426 and grip guide bodies 425 to a common grip guide support 420, which is fixed to the inner cylinder 418.

Each of the position- and torsion-sensing units 423 comprise several tether position sensors 411 , which are part of a sensor ring 412 and transmit their signals via sensor cables 413. The sensor ring 412 is attached to the outer cylinder 419 by means of a ring support 414 and fixed and with screws 663. In the lower part of figure 28, a central cross-sectional view of the drum 200 is shown. Particularly, the path of the electric / optic system 510 is visualised, via which the electric energy is transferred from and to the airborne wind power station 600 via the tether 500 to the ground station 1 and particularly to the rotary joint 100 (see figure 2). After passing the rotation unit 405, the tether 500 is wound on a body 220 of the drum 200. The part of the tether 500 that is wound on the drum body 220 is referred to as wound tether 501. One end of the wound tether 501 terminates in the ground interface 250 (see figure 1) which is arranged inside of the drum body 220. The ground interface 250 transfers the axial tension acting on the wound tether 501 to the mechanical structure of the drum body 220. From the ground interface 250, the electric power and optic signals of the electric / optic system 510 are guided further to the rotational axis of the drum body 220 and to the electric / optical rotary joint 700. The electric / optical rotary joint 700 connects the drum 200 to a further electric / optic system 510 arranged on the rotary table 50. The electric / optical rotary joint 700 is necessary due to the rotatability of the drum body 220 about its longitudinal center axis.

The electric / optical rotary joint 700 is attached to a side plate 221 of the drum 200 via radial fixation plates 231 and longitudinal attachment structures 230 by means of screws 663.

Drum bearings 223 are provided to bear the drum body 220. The drum bearings 223 are mounted in the side plate 221 and in a motor support structure 222, respectively. The motor support structure 222 also serves to support a drum drive or motor 224. The motor 224 serves to rotate the drum body 220 during spooling operations of the tether 500.

Figure 29 - Tether orientation marking

Figure 29 shows a perspective view of an exemplary part of the tether 500. As can be seen in the figure, the tether 500 comprises an orientation marking 502 in the form of a straight line, which preferably extends along in the entire longitudinal direction of the tether 500.

Torsion loads acting on the tether 500 can induce material fatigue and can significantly reduce the service lifetime. In order to keep the tether 500 in an untorsioned state during the operation of the wind power station 600, the orientation marking 502 serves as an indicator for measuring the torsional state of the tether 500. An active mechanism is provided to correct deviations from the untorsioned state of the tether 500 based on this measured indicator.

By means of an optical sensor, the rotational position of the tether 500 can be measured based on the orientation marking 502. Together with measurement data of the position- and torsion-sensing unit 423, deviations from the untorsioned state can be detected and the torsion of the tether 500 can be actively counteracted by the rotation unit 405', 405" (see figures 31 , 33), such that the windings of the tether 500 on the drum body 220 are torsion- free at all times.

Additionally or alternatively, orientation markings can be the provided in the form of conductive, semi-conductive or dielectric markings in the outer layer of the tether 500, that can be detected by electromagnetic measurements using antennas or radar, which has the advantage of less influence of possible pollution on the sensors.

Figure 29a1) shows an orientation marking 502 on the tether 500 in the form of an axial line along the surface of the tether 500. The axial line of the orientation marking 502 has a different colour than the outermost layer of the tether 500, which can for example be an outer protection layer 503.

Figure 29b1) shows an orientation marking 502' on the tether 500' in the form of an axial contour shape, which differs along the circumferential direction from the remaining contour shape of the outer protection layer 503'.

Figure 29c1) shows an orientation marking 502" on the outer protection layer 503" of the tether 500" in the form of an axial groove.

Figure 29d1) shows an orientation marking 502'" on the outer protection layer 503'" of the tether 500'" in the form of an axially extending elevation.

Figure 30 - Tether position sensor 411 of the tether guiding system 400

Figure 30 shows a cross-sectional view through a position- and torsion-sensing unit 423, presenting a possible arrangement of the several position sensors 411 along the circumference of the sensor ring 412.

The position- and torsion-sensing unit 423 can for example comprise six (or less or more) tether position sensors 411 that are circumferentially arranged in regular distances around the tether 500 and mounted in the sensor ring 412, which is fixed to the outer cylinder 419 by means of the ring support 414.

The presence of multiple tether position sensors 411 allows determining the exact position of the tether 500 within the area of the sensor ring 412. The tether position sensors 411 can be based on optical image sensors, in order to be able to detect and calculate the exact position of the tether 500 as well as the position of the orientation marking 502 to determine the torsional state of the tether 500. Also a combination of two different tether position sensors 411 is possible, in which one type of position sensors 411 detects the position of the tether 500 within the sensor ring 412 and another type of position sensor 411 detects the orientation marking 502 to know the torsional state of the tether 500. For the detection of the position within the sensor ring 412, e.g. ultrasonic detectors can be used and for the detection of the orientation marking 502, e.g. optical image sensors can be used.

To detect pollution or metal or dielectric inclusions in the outer protection layer 503 and / or in the elastic buffer / protection layer 518, additional sensor units can be provided e.g. based on radar or electromagnetic techniques. The measurements of these additional sensor units can for example be considered in the interpretation of the signals of the tether position sensors 411 for the measurement of the torsional orientation of the tether 500.

Figure 31 - Rotation unit 405' - adjustable roller pressure

Figure 31 shows a cross-section of a rotation unit 405' with a grip belt system 476 that allows an adjustable pressure to be acted on the tether 500.

Torsion loads acting on the tether 500 can result in material fatigue and significantly reduce the service lifetime. As explained in the description of figure 2, the rotation unit 405' carries out the torsion compensation by rotationally readjusting the tether 500 in case of small or large deviations from the untorsioned state induced by e.g. wind forces or small inner torsional tensions within the tether 500. The respective torsional imbalances can be readjusted with the information of the one or several position- and torsion-sensing units 423 in combination with the information of the rotary encoder 684. The monitoring and possible readjustments of the torsional state of the tether 500 can be controlled via the central control unit and communication interface 26 (figure 2). The position- and torsion-sensing unit 423 on the side of the tether guiding system 400 towards the wind power station 600 (see figure 28) is adapted to measure the torsional deviation of the tether 500 from the untorsioned state. Based on this information, rotational corrections can continuously be carried out by means of the rotation unit 405.

The position- and torsion-sensing unit 423 on the side of the tether guiding system 400 towards the drum 200 is adapted to measure the remaining torsional deviation of the tether 500 from the untorsioned state. Based on this information, fine adjustments of the rotational position of the tether 500 can be carried out by means of the rotation unit 405, in order to wind up the tether 500 on the drum body 220 in such a way, that no residual torsion can be detected anymore.

The active tether torsion compensation provided in the rotary joint cylinder 660' of the wind power station 600 (figure 7) is controlled in a way, that between the position- and torsionsensing unit 423 on the side of the rotation unit 405 towards the wind power station 600 and the rotary joint cylinder 660' of the wind power station 600, possible deviations from the untorsioned state of the tether 500 are regulated to zero.

The information of the initial untorsioned state of the tether 500 is known to a control system (e.g. a control system connected via the central control unit and communication interface 26), when the untorsioned tether is almost entirely spooled up on the drum 200 in the landed state of the wind power station 600.

Since the active tether torsion compensation provided by the rotary joint cylinder 660' of the wind power station 600 features a rotary encoder 684 for measuring the rotation angle and the position, direction and velocity measuring system 605 of the wind power station 600 continuously measures the position, direction and speed of the wind power station 600 in relation to the ground station 1, the state of torsion of the tether 500 between the position- and torsion-sensing unit 423 of the tether guiding system 400 on the side towards the wind power station 600 and the rotary joint cylinder 660' of the wind power station 600 is always known to the control system 26 during operation of the wind power station 600 and constantly regulated to zero torsion.

The position- and torsion-sensing unit 423 on the side towards the drum 200 further measures the lateral position of the tether 500. The respective information can be used to wind the tether 500 in equally distanced, close windings onto the drum 200. For applying corrective rotational movements of the tether 500, in order to compensate for possible torsions of the tether 500, the tether 500 needs to be firmly clamped in the rotation unit 405'. In order to prevent damage to the tether 500, the clamping has to be as uniform as possible along the circumferential and axial directions of the tether 500. For this purpose, a grip belt system 476 is provided in the rotation unit 405' to clamp the tether 500 and to thereby apply corrective rotational movements along a section of the tether 500. The grip belt system 476 is mounted in the inner cylinder 418' that is rotatable and runs on inner cylinder bearings 437.

The embodiment shown in figure 31 comprises a rotation unit 405' with a grip belt system 476 that allows a particularly good distribution of radial forces and torque along the circumferential and axial directions of the tether 500. Furthermore, the clamping pressure of the grip belt system 476 acting on the tether 500 can be regulated by means of an adjustment drive 442, which gives more flexibility to adapt the clamping pressure to the operational state and therefore minimize material fatigue.

Figure 31 also shows details of the drive mechanism for the rotation of the inner cylinder 418'. The inner cylinder 418' is rotatable relatively to the outer cylinder 419' and runs on three bearings - the two inner cylinder bearings 437 which are arranged in the region of the ends of the inner cylinder 418' and the inner cylinder bearing 452 which is arranged in a middle region of the inner cylinder 418'.

Shown in the bottom part of figure 31 , the inner cylinder 418' comprises a radially protruding toothed flange that serves to transfer the drive force of an inner cylinder drive 460 via an inner cylinder drive gear 461 to the inner cylinder 418', in order to rotate the inner cylinder 418' relative to the outer cylinder 419'. To know the exact position of the inner cylinder 418', the inner cylinder drive 460 comprises a rotary encoder 462. The inner cylinder drive 460 and the rotary encoder 462 are connected to the control system by means of a drive cable 463.

For reduced friction and wear of the tether 500, the guiding funnels 410 are covered with gliding layers 430 which could be made out of e.g. a thermoplastic material like polyamide (e.g. PA6, PA11 or PA66) or fluoropolymers like polytetrafluoroethylene (PTFE).

The grip belt system 476 comprises a grip belt 457, which is driven and pressed to the tether 500 by means of grip belt wheels 458. The grip belt wheels 458 run on respective bearings provided in a grip guide roller yoke 453.

The pressure of the grip belt system 476 applied onto the tether 500 can be adjusted by an axial movement of an adjustment cylinder 431. To increase the pressure of the grip belt system 476 onto the tether 500, the adjustment cylinder 431 can be axially moved towards the grip belt system 476, in order to press a ring with a cone-shaped inner surface onto grip guide roller levers 454, which as a result press the grip guide roller yoke 453 radially inwards against the tether 500.

The grip guide roller levers 454 are pivotally attached to the inner cylinder 418' at a lever joint 455 in each case. The maximal pivotal movement of the grip guide roller levers 454 can be limited by adjustment limiters 456.

To get an indication of the clamping pressure applied on the tether 500 and to be able to easily reproduce certain settings, a load sensor 447 can be provided between the part of the adjustment cylinder 431 with the cone-shaped inner surface and the inner cylinder 418'. A protection layer 446 can be provided, in order to protect the load sensor 447 from wear. The protection layer 446 as well as the load sensor 447 can both have the form of a ring segment. In order to reduce the influence of the annular stiffness of the cone-shaped inner surface of the adjustment cylinder 431 on the measurement results of the load sensor 447, the adjustment cylinder 431 can have axial slits next to the load sensors 447.

Data signals from and supply power for the load sensor 447 have to be transferred between the two cylinders 418', 419', which can rotate relatively to each other. In order to bridge the gap between the two cylinders 418', 419', a short distance wireless power and data transmission unit 450 can be provided for the transfer of power and data between the cylinders 418', 419'. The connections of the load sensor 447 to the rotating part of the wireless power and data transmission unit 450 and from its counterpart to the control system are provided by means of transmission cables 451. In order to transfer power and data independently of the rotational position of the inner cylinder 418', the non-rotating part of the wireless power and data transmission unit 450, can circumferentially extend along the entire inner surface of the outer cylinder 419'.

As already mentioned, the adjustment of the pressure of the grip belt system 476 on the tether 500 is implemented via axial movement of the adjustment cylinder 431. This axial movement is provided by the adjustment drive 442. The adjustment drive 442 drives a head shaft 441. The head shaft 441 has the form of a threaded rod, whose rotational movement is converted into a linear, i.e. axial, movement of an adjustment cylinder head 432 by engagement with a threaded hole in the adjustment cylinder head 432. The axial movements of the adjustment cylinder head 432 are guided by a guidance sleeve 440.

The adjustment cylinder head 432 is attached to the adjustment cylinder 431 , in order to be able to move the latter in the axial direction for adjusting the pressure of the grip belt system 476 onto the tether 500. Since the adjustment cylinder 431 is rotating with the inner cylinder 418' and the adjustment cylinder head 432 is fixed to the outer cylinder 419', the adjustment cylinder 431 is only axially, but not rotatably fixed to the adjustment cylinder head 432. A gliding layer 433 can be provided for reducing the friction between the respective parts.

On the left side of figure 31 , a different embodiment of an adjustment cylinder head 432' is shown. A further reduction of the friction between the adjustment cylinder head 432' and the adjustment cylinder 431 is achieved in this embodiment by the implementation of cylinder head bearings 434. The force transfer in this case is provided by the contact pressure of rolling cylinders on a plane surface of the adjustment cylinder 431.

In addition to the load sensor 447, a further control of the clamping pressure of the grip belt system 476 on the tether 500 can be achieved by providing a rotary encoder 443 for measuring the exact position of the adjustment cylinder head 432. Instead of the rotary encoder 443, linear encoders could also be applied for an absolute position measurement of the adjustment cylinder head 432. The rotary encoder 443 and the adjustment drive 442 are connected to the control center via an adjustment drive cable 444.

In order to achieve a well aligned axial movement of the adjustment cylinder 431 , preferably two adjustment cylinder heads 432 or 432' arranged on diametrically opposite sides of the adjustment cylinder 431 are provided. Optionally, even three or more adjustment cylinder heads 432 can be placed at regular distances along the circumference of the adjustment cylinder 431.

The inner cylinder bearing 452 is fixed on the outer cylinder 419' by means of a fixation ring 438. The inner cylinder bearing 437 shown in the top region of figure 31 is fixed on the inner surface of the outer cylinder 419' by means of a fixation ring 438 and bears against a bearing fixation 436 that is attached to the inner cylinder 418'. To provide guiding and gliding of the adjustment cylinder 431 for the axial movement relative to the inner cylinder 418', gliding rings 445 are provided between the inner cylinder 418' and the adjustment cylinder 431.

To provide low friction of the tether 500 in the guiding funnel 410 and on the gliding layer 430, respectively, especially on the side towards the airborne wind power station 600, support bearings 448 are preferably provided that are fixed on the inner surface of the inner cylinder 418' and extend radially inwards through respective apertures of the adjustment cylinder 431 , in order to hold the guiding tube inner supports 416 and / or the guiding tube outer support 415'. Thus, the support bearings 448 allow the guiding funnel 410 to follow the movement of the tether 500, when the tether 500 is touching the guiding funnel 410 or the gliding layer 430, respectively. The described movement is e.g. activated when the wind power station 600 is in operation and flying circular paths, resulting in a rolling movement of the inner surface of the guiding funnel 410 on the tether 500 surface with practically no friction.

In the embodiment of the grip belt system 476 as shown in figure 31 , two grip guide roller yokes 453 are pressed radially inwards towards the centrally arranged tether 500. As will be shown in figure 35, different arrangements with different numbers of pressing units are possible.

Figure 32 - Details of the adjustment cylinder 431

Figure 32 shows a cross-sectional view in different planes offset to each other of the rotation unit 405' for a further explaining of the adjustment cylinder 431. The planes A - A and B - B of the cross-sectional view are indicated in the figure 31 and correspond to the respective indications A - A and B - B at the bottom of figure 32.

It can be seen that the adjustment cylinder 431 comprises rectangular apertures in the cylindrical surface, in order to enable radial passages for the guiding tube outer supports 415’ and the guiding tube inner supports 416'. In the axial direction of the adjustment cylinder 431 , these rectangular apertures are larger than along the circumferential direction, in order to provide space for the movement of the adjustment cylinder 431 in the axial direction for the adjustment of the pressure of the grip belt system 476.

Figure 33 - Rotation unit 405" - tether-cleaning unit 467 & detail of 435 Figure 33 shows a central cross-sectional view of the rotation unit 405" with a detailed view of the grip rollers 427, the roller supports 426 and the grip guide body 425 as shown in figure 28. The combination of grip rollers 427, roller supports 426 and grip guide bodies 425 forms a grip roller system 435. The embodiment of figure 33 also comprises one possible implementation of an optional tether-cleaning unit 467.

The grip roller system 435 allows applying a predefined clamping pressure to the tether 500. Each of the grip rollers 427 run on a bearing in the respective roller support 426. The roller support 426 is pressed by a pressure spring 466 towards the tether 500. The radial displaceability of each roller support 426 and, therefore, of each grip roller 427 can be individually limited by means of an adjustment screw 465. The roller support 426 together with the pressure spring 466 and the adjustment screw 465 are mounted in the grip guide body 425, which is fixed to the grip guide support 420 with screws 663.

Air pollution in combination with fog and / or rain may reduce the effectiveness of the clamping of the tether 500 due to the building up of gliding layers between the tether 500 and the clamping device such as e.g. the guiding grip rollers 427 or the grip belt 457. Removal of these gliding layers can be achieved by the application of a tether-cleaning unit 467.

The tether-cleaning unit 467 can be fixed to the inner surface of the inner cylinder 418". The necessary power and data for the tether-cleaning unit 467 can be transferred between the rotatable inner cylinder 418" and the stationary outer cylinder 419" by means of a wireless power and data transmission unit 450. Further details of the tether-cleaning unit 467 are shown in figure 34.

Figure 34 -Tether-cleaning unit 467

Figure 34 shows a cross-sectional view of the tether-cleaning unit 467. The cleaning of the tether 500 is carried out in a continuous process when the tether is spooled or unspooled on the drum 200.

The cleaning unit 467 can be provided as a ring-like unit arranged around the tether 500, in order to clean the entire circumference of the tether 500. For easier construction and mounting, the cleaning unit 467 can also be subdivided into several ring-segment modules. Figure 34 illustrates the cleaning process by means of the cleaning unit 467. With regard to the following explanations, it is assumed that the tether 500 is moved upwards, i.e. in the direction from the lower part to the top part of the figure.

In a first step, a cleaning agent applicator 474 of the cleaning unit 467 applies a cleaning agent on the tether 500. The cleaning agent can be any agent which serves to clean the outer surface of the tether 500 without damage. Typical cleaning agents are distilled water or water with tensides. The tether 500 with the applied cleaning agent then reaches a first wiper 472 that removes dirt and cleaning agent. Remaining dirt and cleaning agent are then removed by a second wiper 470. When the tether 500 is longitudinally moved further, it passes a drying system 469 of the cleaning unit 467, where the surface of the tether 500 is dried. The drying system 469 preferably comprises a fan.

The cleaning agent applicator 474, the first and the second wipers 472, 470, as well as the air guiding sidewall of the casing 468 of the drying system 469 surround the tether 500, in order to clean the entire circumference of the tether 500.

To remove the removed dirt and the used cleaning agent between the first wiper 472 and the second wiper 470 as well as between the first wiper 472 and the cleaning agent applicator 474, small tubes can be provided for applying a vacuum to this area. Dirt particles and used cleaning agent can be sucked away through these tubes, which are not shown in figure 34.

The cleaning unit 467 comprises a casing 468 for holding and housing the first wiper 472, the second wiper 470, the cleaning agent applicator 474 and the drying system 469. A part of the casing 468 also contains the cleaning agent, which is applied by the cleaning agent applicator 474. The casing 468 is fixed to the inner cylinder 418" by means of screws 663.

The drying system 469 is powered via the wireless power and data transmission unit 450 and the transmission cable 451. The first wiper 472 is fixed to the casing 468 via a first wiper fixation 473. The second wiper 470 is fixed to the casing 468 via a second wiper fixation 471.

Since tether-cleaning units 467 can, along the longitudinal direction, be placed on both sides of the rotation unit 405", it is possible to clean the tether 500 not only during the unspooling operation as exemplary shown in figure 34, but also during the spooling operation, with an arrangement similar to the one shown in figure 34. Figure 35 -Tether grip rollers and belts 427 & 476

Figure 35 shows detailed cross-sectional views of different arrangements of tether clamping systems implemented with the grip roller system 435 and the grip belt system 476.

The grip roller system 435 has already been introduced with respect to figures 28 and 33. Figure 35a) shows a more detailed view of an exemplary combination of a grip roller 427, a roller support 426 and a grip guide body 425 of the grip roller system 435.

The grip roller 427 comprises a stiff and stable roller body 429 - preferably made of metal - and a softer, rubber-like grip layer 428, which are pressed towards the tether 500. The grip roller 427 runs on bearings in the roller support 426 via a respective roller axle 424.

The grip belt system 476 has already been introduced with respect to figure 31. Figure 35b) shows a more detailed view of the grip belt system 476. The grip belt 457 preferably comprises a rubber-like fiber reinforced material which is pressed towards the tether 500 by means of the grip belt wheel 458. The grip belt wheel 458 runs on bearings in the grip guide roller yoke 453 via a respective wheel axle 459.

In order to reduce wear of the grip belt 457, when applying rotational forces to the tether 500 to restore its untorsioned state, guiding gliders 475 can be provided between the grip guide roller yoke 453 and the grip belt 457.

The rotation unit 405, 405' can additionally serve, by means of the grip belt 457 or of the grip roller 427, to tension the tether 500 in the region between the drum 200 and the rotation unit 405, 405', in order to ensure a proper winding up of the tether 500 on the drum 200.

Figure 35c1) shows a simple arrangement of the grip roller system 435, in which two grip roller systems 435 are arranged on diametrically opposed sides of the tether 500.

Figure 35c2) shows a different arrangement of the grip roller system 435', in which three grip roller systems 435' are arranged at equal distances along the circumference of the tether 500. Compared to the arrangement shown in figure 35c1), an increased surface contact can be achieved in this way by the grip rollers 427', which also results in a more homogeneous distribution of the load acting on the tether 500.

Figure 35c3) shows a different arrangement of the grip roller system 435", in which four grip roller systems 435" are arranged at equal distances along the circumference of the tether 500. Compared to the arrangement shown in figure 35c2), an increased surface contact can be achieved in this way by the grip rollers 427", which also results in a more homogeneous distribution of the load acting on the tether 500.

In principle, the arrangements shown in the figures 35c1 , 35c2 and 35c3 can also be applied in an analogous way for the grip belt system 476.

Figure 35d) shows a further optimized arrangement of the grip roller system 435"', similar to the arrangement as shown in figure 35c2), featuring modified roller bodies 429' with arcshaped outer surfaces, which allow to distribute the pressure force transfer via the grip layers 428' equally around the entire circumference of the tether 500. An even more increased surface contact can be achieved in this way by the grip rollers 427", which also results in an even more homogeneous distribution of the load acting on the tether 500. Since the roller bodies 429' preferably touch each other, practically no pressure adjustment is possible in this case, which can be an advantage or disadvantage.

Figure 36 -Tether guiding system 400 with linear unit 404

Figure 36 shows a side view of the tether guiding system 400 which comprises a linear unit 404 and a rotation unit 405. The tether guiding system 400 as well as the rotation unit 405 and the linear unit 404 have already been explained in the descriptions of figure 2 and figure 28.

The linear unit 404 can be subdivided into an upper and a lower part. The upper part of the linear unit 404 serves to vertically position the tether guiding rotation unit 405 to the correct height, in order to minimize bending loads acting on the tether 500. The lower part of the linear unit 404 serves to horizontally position the tether guiding rotation unit 405 to the correct position in relation to the drum 200, in order to get a regular and space-optimized uncoiling and coiling of the tether 500 on the drum 200.

The linear unit 404 is movable, with its lower part, in parallel to the axial direction of the drum 200. For this purpose, the linear unit 404 comprises a linear slide 484 on which a frame 480 is fixed. The linear slide 484 is movable in parallel to the axial direction of the drum 200 by means of a horizontal drive 481 and glides on a linear slide base 485 which is fixed to the carrier plate 210. The linear slide base 485 extends in parallel to the axial direction of the drum 200.

The horizontal drive 481 is fixed on the linear slide 484 and moves the linear slide 484 by rotating a drive gear 482 which transfers the rotational force into a linear force by engaging with a toothed rack 483. Since the toothed rack 483 is fixed on the linear slide base 485, the linear slide 484 is linearly moved in parallel to the axial direction of the drum 200 upon rotation of the drive gear 482.

The functional elements of the upper part of the linear unit 404 are mounted on the frame 480 and comprise two wire ropes 488 that are attached with both ends to a respective linear slide 422, in order to form a closed loop on each side of the tether guiding rotation unit 405. The ends of the wire ropes 488 are attached to the linear slides 422 by means of a fixation element 490 in each case. Together, the wire ropes 488 and the linear slides 422 form a height adjustment unit 495. The height adjustment unit 495 serves to optimally position the tether guiding rotation unit 405 which is pivotally hold by the two linear slides 422. The linear slides 422 are slideably mounted on an upper base structure 487 in each case. Each of the two upper base structures 487 is attached to an upper part of the frame 480 and extends in an inclined direction with respect to the gravitational direction and approximately in a perpendicular direction relative to the axis of the drum 200

On each side of the tether guiding rotation unit 405, two force transmission wheels 489 are provided, in order to hold and tension the respective closed loop formed by the wire rope 488 and the linear slide 422. At least one force transmission wheel 489 on each side of the tether guiding rotation unit 405 can be driven by a motor, in order to move the height adjustment unit 495 and in particular the linear slides 422 along the upper base structure 487 for adjusting the height of the tether guiding rotation unit 405. Thus, when the force transmission wheels 489 are rotated by the motor, the tether guiding rotation unit 405 is moved linearly along the upper base structure 487.

Centrally within each linear slide 422, an outer cylinder axle 491 is pivotally held by means of respective bearings. The outer cylinder axles 491 are fixedly attached on either side of the outer cylinder 419, 419', 419". In this way, a rotatable connection between the tether guiding rotation unit 405 and the linear slides 422 is achieved. Figure 37 - Details of linear unit 404 and of tether guiding system 400 with drum

Figure 37 shows different cross-sectional views of parts of the linear unit 404 and of the height adjustment unit 495 (figures 37a) and 37b)), as well as a top view of the tether guiding system 400 and the drum 200 (figure 37c)).

Figure 37a) shows a cross-sectional view of the upper part of the linear unit 404 with details of a possible mounting of the height adjustment unit 495 on the upper base structure 487 and on the frame 480.

The rotation unit 405 keeps the part of the tether 500 between the tether guiding system 400 and the drum 200 in a straight, orthogonal position to the rotation axis of the drum 200, when the wind power station 600 moves in e.g. a circular path. This redirecting of the tether 500 by the tether guiding rotation unit 405 can result in large mechanical forces acting on the tether guiding rotation unit 405 in all spatial directions. In order to nevertheless provide precise guiding of the linear slides 422 also under these circumstances, a massive outer frame 492 is attached to each of the upper base structures 487 via screws 663 as shown in Figure 37a).

The outer cylinder 419 can rotate in the linear slides 422 via the outer cylinder axles 491. The linear slides 422 glide in a guided way on the upper base structures 487. These upper base structures 487 are fixed to the frame 480 as well to the outer frame 492 by means of screws 663.

On the left side of figure 37a), an implementation of the wire rope 488 with a steel rope having a circular cross-section is shown. On the right side of figure 37a), an implementation of the wire rope 488' with a chain having a rectangular cross-section is shown.

The redirecting forces of the tether guiding rotation unit 405 acting on the tether 500 can induce large forces to the wire ropes 488. A measuring of these forces can be carried out by means of annular load sensors 447 that are arranged within the fixation elements 490 for further control of the system. The powering of the sensors and the transmission of the measured data between the height adjustment unit 495 and the outer frame 492 of the linear unit 404 can be established via a wireless power and data transmission unit 450 and transmission cables 451. For the purpose of simplicity, the outer frame 492 and the wireless power and data transmission unit 450 on the left side of figure 37a) are not shown.

Figure 37b) shows a central longitudinal cross-sectional view of the height adjustment unit 495. Each of the fixation elements 490 comprises a force transmission fixation 493, which provides a mountable fixation to the linear slide 422 for the wire rope 488. The force transmission fixation 493 comprises a longitudinally extending through-hole through which the wire rope 488 extends. During assembly, the wire rope 488 is moved through the through-hole, through the annular load sensor 447 and through an end fixation 494. After levelling the end of the wire rope 488 to the end surface of the end fixation 494, the end fixation 494 can be fixed to the end of the wire rope 488 by e.g. pressing. In a last step, the end of the wire rope 488 together with the end fixation 494, the annular load sensor 447 and the force transmission fixation 493 are fixed inside of the linear slide 422 by means of a thread-engagement between the linear slide 422 and the force transmission fixation 493.

The connection of the annular load sensor 447 to the control center can be established via transmission cables 451 and the wireless power and data transmission unit 450. For the insertion of the transmission cable 451 during assembly of the height adjustment unit 495, a slit or groove extending along the longitudinal direction of the thread of the linear slide 422 can provide the required space for the transmission cable 451 (not shown in figure 37b).

Figure 37c) shows a top view of a further embodiment of the tether guiding system 400 and the drum 200. The embodiment of figure 37c) particularly differs from the one of figure 36 by a different principle for linearly displacing the upper part of the linear unit 404' in parallel to the longitudinal center axis of the drum 200.

Furthermore, a wheel drive 498 is shown in figure 37c) which serves to drive a wheel axle 497 on which the two lower force transmission wheels 489 of the upper part of the linear unit 404 and 404' are attached. Thus, the wheel drive 498 serves to move the height adjustment unit 495 and in particular the two linear slides 422 along the upper base structures 487, in order to position the tether guiding rotation unit 405 along the vertical direction. The wheel drive 498 is supplied with electric power and controlled by control signals, which are both transmitted by a wheel drive power and data cable 499. The two upper force transmission wheels 489 are fixed to another wheel axle 497 which is freely rotatable mounted in the frame 480.

Different elements providing a linear movement of the upper part of the linear unit 404 parallel to the direction of the longitudinal center axis of the drum 200 have already been described further above with respect to figure 36.

In the embodiment of figure 36, the linear movement the linear unit 404 in parallel to the longitudinal center axis of the drum 200 is achieved via the interface between the drive gear 482 and the toothed rack 483. In the embodiment of figure 37c), a base frame 552 is provided which is fixed to the carrier plate 210 and extends along the longitudinal center axis of the drum 200.

The linear unit 404' is attached, via the frame 480, to two laterally arranged slide blocks 551. Each of the slide blocks 551 has a threaded through-hole. A connection structure 555 can be provided that connects the two slide blocks 551 , in order to improve their structural stability. A threaded rod 550 extends along the longitudinal center axis of the drum 200 and through the threaded through-hole of each of the slide blocks 551. The ends of the threaded rod 550 are attached in such a way to lateral holding elements 553 of the base frame 552, that the threaded rod 550 is freely rotatable about its longitudinal center axis.

By means of rotating the threaded rod 550 about its longitudinal center axis, the slide blocks 551 , and, thus, the linear unit 404' can be moved in parallel to the longitudinal center axis of the drum 200 owing to the engagement of the threaded rod 550 with the threaded through-holes of the slide blocks 551. The linear movability of the linear unit 404' is limited in each direction by the lateral holding elements 553. The base frame 552 can comprise a slideway for the slide blocks 551 , in order to precisely guide the slide blocks 551 and, thus, the linear unit 404’ with as little friction as possible.

The rotation of the threaded rod 550 about its longitudinal center axis is effected by a rod drive 554. The rod drive 554 is supplied with electric power and controlled by control signals, which are both transmitted via a drive power and data cable 496.

The rotation of the drum body 220 is effected by the motor 224, as already explained further above with respect to figure 28. The motor 224 is supplied with electric power and controlled by control signals, which are both transmitted via a power and data cable 235. Figure 38 - Drum 200 and ground interface 250

Figure 38 shows cross-sectional views of surface structures and of layers on the drum body 220 of the drum 200 (figures 38a 1) to 38a3)) as well as an overview (figure 38b)) and a detailed view (figure 38c)) of the ground interface 250 at the drum 200 (see also figure 1).

During operation of the wind power station 600, spooling and unspooling operations are usually carried out by the drum 200, while substantial tension forces of the wind power station 600 are acting via the unspooled part of the tether 500 and the wound tether 501 on the drum body 220 and, thus, on the drum 200. Since these tension forces can be high, an optimal design of the drum body 220 and / or the provision of buffer layers on the drum body 220 can help to increase the fatigue life of the tether 500 by distributing the resulting radial pressure on a larger part of the circumference of the wound tether 501.

Figure 38a) shows a partial cross-sectional view of different surface structures on the drum body 220 of the drum 200. In the embodiment of figure 38a1), the surface structure is formed directly by the drum body 220'. In the embodiments of figures 38a2) and 38a3), the surface structures are formed by a buffer layer 228, 228' which is attached on the outer surface of the drum body 220. The surface structures serve to increase the contact surface of the wound tether 501 with the drum body 220 or with the buffer layer 228, respectively, as a result of which the local radial pressure acting on the wound tether 501 is decreased. The fatigue life of the tether 500 can be increased in this way.

Figure 38a1) shows a partial cross-sectional view of the drum body 220' featuring a helical, rounded groove on its cylindrical outer surface, for increasing the contact surface of the wound tether 501 to the drum body 220'. The structured outer surface of the drum body 220' can for example be made of polished high strength steel.

Figure 38a2) shows a partial cross-sectional view of the drum body 220 with a buffer layer 228. The buffer layer 228 is made of a flexible material, which leads to a deformation of its outer surface in the presence of the tensioned wound tether 501. This contact surface between the wound tether 501 and the buffer layer 228 is increased in this way, which helps to increase the fatigue life of the wound tether 501.

Figure 38a3) shows a partial cross-sectional view of the drum body 220 with a buffer layer 228'. The outer surface of the buffer layer 228' is pre-shaped with a helical, rounded groove, which leads to an increased contact surface of the wound tether 501 to the buffer layer 228'.

In the embodiments of figures 38a2) and 38a3), the hardness of the buffer layer 228' can be selected independently of the hardness of the material of the drum body 220, in order to optimize the contact surface to the specific characteristics of the wound tether 501. The material of the buffer layer 228, 228' can for example be an elastomer, such as a polyurethane material, having a suitable Shore-hardness. The material Hytrel^® of DuPont is considered to be a particularly suitable material for the buffer layer 228, 228' or specifically designed synthetic rubber materials. More rigid thermoplastic materials, such as polyamide (e.g. PA6, PA11 or PA66) or fluoropolymers like polytetrafluoroethylene (PTFE) can also be used.

Figure 38b) shows a transverse cross-sectional view of the drum body 220. Particularly, the wound tether 501 and the ground interface 250 with the low flection termination 630 are visible in figure 38b). The mechanical forces (if the tether 500 is fully wound off from the drum body 220), the electric energy and the electric and fiber optic signals between the tether 500 and the ground station 1 are transferred to the ground station 1 by the ground interface 250. The wound tether 501 is guided through an opening in the cylindrical outer surface of the drum body 220 to the low flection termination 630. In order to minimize bending load and maximize the bending radius of the tether termination at the ground station 1 , the drum 200 comprises a ground interface support 251 for holding and guiding the tether 500 from the opening in the cylindrical outer surface of the drum body 220 to the low flection termination 630. The ground interface support 251 forms an inner structure of the drum 200 and is fixed to the drum body 220. A preferred embodiment of a low flection termination 630 and variations thereof for use at the air interface 610 have been already described with respect to figures 6, 8, 9, and 10. The low flection termination 630 at the drum 200 and as shown in figure 38b) can be designed in an analogous way.

The low flection termination 630 is fixed to the cylindrical drum body 220 via the ground interface support 251 , i.e. the inner structure of the drum 200. The tension forces acting on the wound tether 501 are transferred via the low flection termination 630 to the ground interface support 251 and, thus, to the drum 200 of the ground station 1.

The function of the low flection termination 630 is to transfer high axial loads induced by the wind power station 600 during e.g. crosswind-flight and carried by the axial load-bearing layer 530 of the tether 500 to the ground interface support 251. The low flection termination 630 also provides a protection of the electric / optic system 510 against contractional forces of the axial load-bearing layer 530 as well as a feed-through for the electric / optic system 510 to an aperture in the ground interface support 251. From the aperture in the ground interface support 251, the electric / optic system 510 is guided further through an opening in the axle of the drum body 220 to the electric / optical rotary joint 700 at the side of the drum 200, as shown in figure 28.

Figure 38c) shows a central longitudinal cross-sectional view of the low flection termination 630 fixed to the ground interface support 251 by means of inner fixation elements 636 and outer fixation elements 632'.

The different design variations of the low flexion termination 630 as described with respect to figures 6, 8, 9, and 10 in relation to the air interface 610 can also be applied with respect to the low flection termination 630 applied at the ground interface 250 and described with respect to figure 38.

Figure 39 - Rotary joint 100

Figure 39 shows a central longitudinal cross-sectional view of the rotary joint 100. The rotary joint 100 generally serves to transfer low voltage electric power, low voltage electric signals as well as high voltage electric power and fiber optic data signals between a part with unlimited rotational capabilities and a fixed part. In the present application, the rotary joint 100 provides an unlimited rotational connection for transferring electric energy and steering signals, including fiber optic signals, between the rotatable carrier plate 210 and the energy and signal interface 20 (figure 1), in particular the stationary interfaces 22, 26 and 851, which are attached to the base structure 10.

The electric energy and the data signals of the electric / optic system 510, the auxiliary power and the data signals of various auxiliary motors and sensors of the drum 200, the tether guiding system 400, the wind measurement system 401 , the rotary table 50 and the landing support 300 are transferred from the rotating rotary table 50 to the energy and signal interface 20 by means of the rotary joint 100.

Since the energy transfer is typically in the medium or high voltage range, a special design as described in the following is required for the rotary joint 100 to manage the high electric field strengths and to prevent flashover in operation. In particular, the rotary joint 100 comprises an electric / optical rotary joint 700 as already described e.g. with respect to figure 11 for transferring electric energy as well as fiber optic signals between the drum 200 and the energy and signal interface 20. The electric / optical rotary joint 700 of the rotary joint 100 is also able to transfer fiber optic data of other parts of the ground station 1 via the branch line fiber optic cable 710'. Details of possible embodiments of the electric / optical rotary joint 700 have already been explained with respect to figures 11 - 22.

The rotary joint 100 comprises a stationary part being fixed to the base structure 10 and a rotatable part being fixed to the carrier plate 210. The stationary part of the rotary joint 100 particularly comprises a cylindrical joint casing 105 and a contact support cylinder 115 with sliding contacts 840""' '. The joint casing 105 of the rotary joint 100 is fixed to the base structure 10 by means of the rotary joint fixation 101. The rotatable part of the rotary joint 100 particularly comprises a central cylinder 110, an insulating cylinder 111 and slip rings 113.

The auxiliary supply and feedback cables 27 (see figure 2) as well as the electric / optic system 510 are guided from the stationary part of the rotary joint 100 to various interface units for the connection to an electric grid or to a central steering or control unit. The electric / optic system 510 on the side of the base structure 10 is connected to the combined optic and electric power interface 851 , in which the optic signal transmission and the electric power transmission are split up, i.e. physically separated from each other.

The electric power and data signals of the auxiliary supply and feedback cables 27 coming from the drum 200 and through respective apertures in the rotating carrier plate 210 are electrically connected to the slip rings 113. From these slip rings 113, the electric contact to the non-rotating auxiliary supply interface 22 is established by means of the sliding contacts 840'"" ' and in each case further via a flexible electric conductor 839', a contact plate 128, a cable connection 127, a cable coupling 126 and via an auxiliary supply and feedback cable 120. The auxiliary supply and feedback cables 120 are electrically insulated by a respective cable insulation 121.

In order to achieve a good electric contact between the sliding contacts 840'"" ' and the slip rings 113, the sliding contacts 840'"" ' are preferably pressed against the slip rings 113 by means of contact springs 838'"" '. Sliding contact insulators 125 are provided, in order to electrically insulate the sliding contacts 840. against the contact support cylinder 115. For the rotatable part of the rotary joint 100, electric insulation of the slip rings 113 against the central cylinder 110 is achieved by means of the insulating cylinder 111.

To prevent dust and humidity of entering the contact system provided in the coaxially arranged cylinders 110 and 115, lip seals 666 can be provided, along the longitudinal direction, at both ends of the insulating cylinder 111. The lip seals 666, which are preferably attached to the contact support cylinder 115, serve to seal the space between the two cylinders 110, 115 against the outside. For easy assembly of the contact system, the lip seals 666 at the lower end of the insulating cylinder 111 (in view of figure 39) are attached via a respective seal holder 112 to the contact support cylinder 115 and are only attached to the latter after the central cylinder 110, together with the insulating cylinder 111 , has been inserted into the contact support cylinder 115.

For the transfer of the auxiliary power and the data signals, a sliding cylinder bearing 116 is provided between the rotatable and the stationary parts of the rotary joint 100. The sliding cylinder bearing 116 is mounted between the contact support cylinder 115 and a bearing fixation 130, which is attached to the carrier plate 210 by means of heavy load threaded connections 672. The sliding cylinder bearing 116 is hold in place by a first fixation ring 131 that is fixed on the bearing fixation 130 and by a second fixation ring 117 that is fixed on the outer surface of the contact support cylinder 115. For easy assembly, each of the first fixation ring 131 and the second fixation ring 117 can preferably be split into two pieces forming a half cycle in each case.

The central cylinder 110 is fixed to the carrier plate 210 by means of heavy load threaded connections 672. The electric / optical rotary joint 700 is axially aligned with the central cylinder 110 and the contact support cylinder 115.

To prevent the entering of dust and water into the space between the joint casing 105 and the central cylinder 110, further lip seals 666 can circumferentially be provided between the joint casing 105 and the carrier plate 210.

The electric / optical rotary joint 700 of the rotary joint 100 comprises inner fixation plates 735, which are fixed to corresponding outer fixation plates 675 that are fixedly attached to the inner surface of the joint casing 105. The inner fixation plates 735 are fixed to the outer fixation plates 675 by means of fixations 736, which allow a precise axial alignment and fixation of the stationary part of the rotary joint 100 to the rotatable part of the rotary joint 100.

The non-rotatable parts of the electric / optical rotary joint 700 are further fixed to the contact support cylinder 115 by means of outer heavy load threaded connections 672. The rotatable parts of the electric / optical rotary joint 700 are fixed to the central cylinder 110 by means of inner heavy load threaded connections 672.

Thus, the electric / optical rotary joint 700 cannot only be used to connect the wind power station 600 to the tether 500, but also at the ground station 1 between the drum 200 and the carrier plate 210 (see figure 28) as well as in the rotary joint 100 between the carrier plate 210 and the base structure 10 (figure 39).

REFERENCE NUMERALS Ground station 115 Contact support cylinder Base structure 116 Sliding cylinder bearing Energy and signal interface 117 Second fixation ring Energy converter 120 Auxiliary supply and Auxiliary supply interface feedback cable Energy cable 121 Cable insulation Auxiliary supply cable 125 Sliding contact insulator Control and communication 126 Cable coupling cable 127 Cable connection Central control unit and 128 Contact plate communication interface 130 Bearing fixation Auxiliary supply and 131 First fixation ring feedback cable 200 Drum Rotary cylinder drive 210 Carrier plate Drive gear 220 Drum body Toothed ring 221 Side plate Axial stiffness bearing 222 Motor support structure Cylinder bearing 223 Drum bearing Ball bearing 224 Motor Rotary table 226 Drum support Rotary cylinder 228 Buffer layer Offshore platform 230 Attachment structure Sidewall-mooring connector 231 Fixation plate Bottom-mooring connector 235 Power and data cable Stabilising ballast 250 Ground interface Mooring rope 251 Ground interface support Mooring rope connection 290 Lightning rod Rotary joint 291 Earthing system Rotary joint fixation 293 Offshore earth connection Joint casing 295 Auxiliary support Central cylinder 296 Wheel axle Insulating cylinder 297 Tilted support rail Seal holder 300 Landing support Slip ring 301 Circular tracks Drive gear 419 Outer cylinder Bearing 420 Grip guide support Wheel 421 Outer cylinder bearing Landing support drive 422 Linear slide Rail foundation 423 Position- and torsion-sensing Rotary encoder unit Power and signal cable 424 Roller axle Tilt protection foundation 425 Grip guide body Tilt protection support 426 Roller support Tilt protection wheel 427 Grip roller Landing support base 428 Grip layer Rotary plate 429 Roller body Toothed ring 430 Gliding layer Guiding and adjusting system 431 Adjustment cylinder Beam support 432 Adjustment cylinder head Fork support 433 Gliding layer Transverse support 434 Cylinder head bearing Frame 435 Grip roller system Outer surface 436 Bearing fixation Distance sensor 437 Inner cylinder bearing Sensor cable 438 Fixation ring Main frame 440 Guidance sleeve Back frame 441 Head shaft Tether guiding system 442 Adjustment drive Wind measurement system 443 Rotary encoder Linear unit 444 Adjustment drive cable Rotation unit 445 Gliding ring Guiding funnel 446 Protection layer Tether position sensor 447 Load sensor Sensor ring 448 Support bearing Sensor cable 450 Wireless power and data Ring support transmission unit Guiding tube outer support 451 Transmission cable Guiding tube inner support 452 Inner cylinder bearing Fixations 453 Grip guide roller yoke Inner cylinder 454 Grip guide roller lever Lever joint 496 Drive power and data cable Adjustment limiter 497 Wheel axle Grip belt 498 Wheel drive Grip belt wheel 499 Wheel drive power and data Wheel axle cable Inner cylinder drive 500 Tether Inner cylinder drive gear 501 Wound tether Rotary encoder 502 Orientation marking Drive cable 503 Outer protection layer Adjustment screw 510 Electric / optic system Pressure spring 511 Fiber optic cable Tether cleaning unit 512 Elastic core Casing 513 Electric conductors Drying system 514 Semi-conductive layer Second wiper 515 Electric insulation layer Second wiper fixation 516 Semi-conductive buffer layer First Wiper 517 Screen conductors First wiper fixation 518 Elastic buffer / protection Cleaning agent applicator layer Guiding glider 519 Folded back electric screen Grip belt system conductor Frame 520 Compression resistant layer Horizontal drive 530 Axial load-bearing layer Drive gear 550 Threaded rod Toothed rack 551 Slide block Linear slide 552 Base frame Linear slide base 553 Holding element Upper base structure 554 Rod drive Wire rope 555 Connection structure Force transmission wheel 600 Wind power station Fixation element 601 Electric power generator Outer cylinder axle 605 Position, direction and Outer frame velocity measurement system Force transmission fixation 606 Fuselage End fixation 607 Tilt protection shell Height adjustment unit 608 Gliding layer Stop lip 664 Ball bearing Air interface 665 Cylinder ball bearing Transverse suspension 666 Lip seal Longitudinal suspension 667 Screw-nut connection U-shaped element 670 Fixation ring Central suspension ring 671 Fixation ring Stiffening support 672 Heavy load threaded Inner shell connection Outer shell 674 Cylinder tube Dome-shaped coupling 675 Outer fixation plate structure 677 Suspension ring Lateral extension 680 Toothed ring Stop element 682 Adjusting gear Basis 683 Drive Roller 684 Rotary encoder Bearing 685 Power and signal cable Low flection termination 687 Filament section Outer tether clamp 688 Inner layer filaments Outer fixation element 689 Outer layer filaments Pressure spring 690 Spliced sling Inner tether clamp 691 Spliced sling Inner fixation element 692 Sling bolt Rolling ball bearing 693 Fixation cylinder Annular sealing element 694 Load adjustment screw Small rolling ball 695 Inner layer end part Large rolling ball 696 Outer layer end part Bearing support 697 Lower meander clamp Gliding layer 698 Middle meander clamp Channel 699 Upper meander clamp Sealing element 700 Electric / optical rotary joint Flexible anchoring basis 701 Combined high voltage and Groove fiber optic connector Rotary joint cylinder 702 High voltage and fiber optic Tether termination plate rotary joint Connection element 710 Branch line fiber optic cable Screw 711 Connector Gas-tight feedthrough 771 Flexible layer element Rotary connector fixation 772 Socket thread insert plate 773 Screw Rotary connector ball bearing 775 Cable lug Rotary connector cylinder 777 Cylinder contact element bearing 778 Contact ring Rotary connector plate 780 Metallic pressure ring Rotary connector bearing ring 781 Pressure resistant tube Lower gliding ring 782 Crimped electric conductors O-ring seal 783 Crimping tube Upper gliding ring 784 Clamping cone O-ring seal protection 785 Contact body Seal spring 786 Contact spring Seal spring limiter 788 First bordering element Partial discharge sensor 789 Windings Circumferential seal 791 Second bordering element Signal cable 792 Conductor socket Coaxial cable shield 795 Fiber optic cable seal Inner fixation plate 797 Non-linear electric field Fixation grading material Rotary joint cylinder 800 Plug body Connector fixation plate 801 Spring Gas exchange valve 802 Plug pin Gas density sensor 803 Fiber centering tube Signal cable 804 Centering tube Screen earthing cable 805 Fiber centering tube Deflector 806 Fiber connector socket Stress cone 807 Socket body High voltage shield 809 Base plate Socket insulator 810 Fiber optic connector unit Connector element 811 Multiple fiber optic connector Thread insert unit Fixation element 820 Base cylinder Press ring casing 821 Non-rotating lower guiding Press ring element Spring 823 Non-rotating upper guiding element 850 High voltage cable Fiber optic rotary joint 851 Combined optic and electric Outer contact cylinder power interface Contact element 852 High voltage connector Rotary joint seal 853 Bottom plate Inner contact cylinder 854 Flange cover Clamping pad 855 Cover plate Fiber connector cylinder 856 Sidewall Fiber socket 862 Contact socket Fiber connector 863 Socket contact Rotating lower guiding 865 Contact pin element 866 High voltage cable Rotating upper guiding 867 Electro-optic separation element cylinder High voltage rotary joint 881 High voltage contact cylinder contact system 890 Electric conductor Contact spring 891 Longitudinal elastic buffer Flexible electric conductor 892 Low friction elastic buffer Sliding contact layer Guiding ring 900 Windshield Limiting plate 907 Fixation frame Connection plate 950 Glide connection Contact spring limiter

Claims

1. A wind power device for converting wind energy into electric energy, comprising a wind power station (600) with one or more electric power generators (601) that are adapted to convert wind power into electric energy, when the wind power station (600) is airborne; a tether (500) for transferring the electric energy generated by the one or more electric power generators (601) to a ground station (1); and an air interface (610) for connecting the tether (500) to the wind power station (600); characterized in that the air interface (610) is adapted to connect the tether (500) to the wind power station (600) in such a way, that unlimited rotations of the wind power station (600) with respect to the tether (500) are possible.

2. The wind power device according to claim 1 , wherein the air interface (610) comprises at least one drive (683) for rotating the tether (500) with respect to the wind power station (600).

3. The wind power device according to claims 1 or 2, additionally comprising the ground station (1), wherein the ground station (1) has a rotation unit (405) with at least one drive (460) for rotating the tether (500) about its longitudinal center axis.

4. The wind power device according to one of the preceding claims, being adapted to control the wind power station (600) to fly along circular paths and / or along figure-8 paths.

5. The wind power device according to one of the preceding claims, wherein the tether (500) comprises an orientation marking (502) for determining the rotational position of the tether (500), and wherein the wind power device is adapted to measure the rotational position of the tether (500), preferably in order to detect the torsional state of the tether (500).

6. The wind power device according to one of the preceding claims, wherein the air interface (610) comprises a connection element (660) that is pivotally, in particular pivotally in a plurality of directions, attached to the wind power station (600).

7. The wind power device according to claim 6, wherein the air interface (610) comprises a gimbal (611, 612; 611, 615, 616) for the attachment of the connection element (660) to the wind power station (600).

8. The wind power device according to claim 6, wherein the air interface (610) comprises a dome-shaped coupling structure (621) for attaching the connection element (660) to the wind power station (600), the dome-shaped coupling structure (621) in particular comprising a first shell (619) and a second shell (620), the first shell (619) being movably arranged in or on the second shell (620).

9. A wind power device for converting wind energy into electric energy, in particular a wind power device according to one of the preceding claims, comprising a wind power station (600) with one or more electric power generators (601) that are adapted to convert wind power into electric energy, when the wind power station (600) is airborne; a ground station (1); and a tether (500) for transferring the electric energy generated by the one or more electric power generators (601) to the ground station (1); wherein the ground station (1) comprises a drum (200) for winding up the tether (500), the drum (200) having a longitudinal center axis; characterized in that the drum (200) is rotatable about an axis, which extends essentially perpendicularly to the longitudinal center axis, such that, during operation, the orientation of the drum (200) can be adapted to the direction of the tether (500) and / or to the position of the wind power station (600).

10. The wind power device according to claim 9, wherein the ground station (1) comprises at least one drive (30) for rotating the drum (200) about the vertically extending axis.

11. The wind power device according to claim 9 or 10, wherein the ground station (1) comprises a landing support (300) for receiving the wind power station (600) during landing operations, and wherein the landing support (300) is likewise rotatable about the vertically extending axis, such that, during landing operations, the landing support (300) can be oriented to the direction of the tether (500) and / or to the position of the wind power station (600).

12. An electric / optical rotary joint (700), in particular of a wind power device according to one of the preceding claims, for coupling a first electric and optic line (510) with a second electric and optic line (510) in such a way that unlimited rotations of the first electric and optic line (510) relative to the second electric and optic line (510) are enabled, the first electric and optic line (510) and the second electric and optic line (510) each comprising an outer electric conductor (517), an inner electric conductor (513) and an optic fiber (511) and the electric / optical rotary joint (700) comprising an outer contact cylinder (737); an outer contact element (715, 730, 777) which is rotatably arranged with respect to the outer contact cylinder (737); one or more outer contacts, in particular sliding contacts (828, 778), for electrically connecting the outer contact cylinder (737) with the outer contact element (715, 730, 777), in order to electrically couple the outer electric conductor (517) of the first electric and optic line (510) with the outer electric conductor (517) of the second electric and optic line (510); an inner contact cylinder (830; 826); an inner contact element (826; 830) which is rotatably arranged with respect to the inner contact cylinder (830; 826); one or more inner contacts, in particular sliding contacts (828), for electrically connecting the inner contact cylinder (830; 826) with the inner contact element (826; 830), in order to electrically couple the inner electric conductor (513) of the first electric and optic line (510) with the inner electric conductor (513) of the second electric and optic line (510); and a fiber optic rotary joint (825) for coupling the optic fiber (511) of the first electric and optic line (510) with the optic fiber (511) of the second electric and optic line (510); wherein the outer contact cylinder (737) radially encompasses the inner contact cylinder (830; 826) and the inner contact cylinder (830; 826) radially encompasses the fiber optic rotary joint (825).

13. The electric / optical rotary joint (700) according to claim 12, wherein the outer contact cylinder (737) and the outer contact element (715, 730, 777) define a gas-tight inner space, in which the inner contact cylinder (830; 826) and the inner contact element (826; 830) are arranged.

14. A combined high voltage and fiber optic connector unit (701), preferably of a wind power device according to one of claims 1 to 11 , more preferably of an electric / optical rotary joint (700) according to claims 12 or 13, comprising a female part, which comprises an electrically conducting socket (792) and a first optic fiber (511) extending through the socket (792); a male part, which is pluggable into the female part, and which comprises an electrically conducting contact body (785) and a second optic fiber (511) extending though the contact body (785); and a spring element (801 ) arranged in the female part or in the male part, for pressing an end face of the first or the second optic fiber (511) against an end face of the second or the first optic fiber (511), when the male part is plugged into the female part, in order to couple the first and the second optic fibers (511); wherein the contact body (785) is adapted to be inserted into the socket (792), in order to establish an electric contact between the contact body (785) and the socket (792).

15. The combined high voltage and fiber optic connector unit (701) according to claim 14, wherein the part of the male part or of the female part, in which the spring element (801) is arranged, comprises a widened inner space for receiving an extra length portion, which in particular is in the form of a winding (789), of the first or second optic fiber (511).

16. The combined high voltage and fiber optic connector unit (701) according to claims 14 or 15, wherein the female part comprises a first fiber centering tube (805) encompassing the first optic fiber (511) in the region of its end face, and the male part comprises a second fiber centering tube (803) encompassing the second optic fiber (511) in the region of its end face, the first and the second fiber centering tubes (805, 803) being arranged coaxially behind each other and preferably abutting each other, when the male part is plugged into the female part.

17. A coupling structure, in particular of a wind power device according to one of claims 1 to 11, comprising a connection element (660); and an electric and / or optical cable (500) coupled to the connection element (660) and having an inner electric / optic line (510) with an electric conductor (513, 517) and / or an optic fiber (511) as well as an outer load- bearing layer (530) for absorbing axial loads, the load-bearing layer (530) extending concentrically with respect to the electric / optic line (510); characterized in that at least one component of the load-bearing layer (530) has an end part which, along the longitudinal direction of the electric and / or optical cable (500) towards the connection element (660), is radially guided away from the electric / optic line (510), in order to be fixedly attached to the connection element (660) at an increased radial distance from the electric / optic line (510) which is guided radially inside of the end part of the load-bearing layer (530) into the connection element (660).

18. The coupling structure according to claim 17, additionally comprising a first clamp (635; 698) and a second clamp (631; 697, 699) which are fixedly attached to the connection element (660) and serve for clamping the at least one component of the load-bearing layer (530).

19. The coupling structure according to claim 18, wherein the first clamp (635) has a conical outer surface and is radially arranged between the electric / optic line (510) and the at least one component of the load-bearing layer (530).

20. The coupling structure according to claim 18, wherein the first clamp (698) and the second clamp (697, 699) have meander-shaped clamping surfaces for clamping the at least one component of the load-bearing layer (530) in- between.

21. The coupling structure according to claim 17, wherein the end part of the at least one component of the load-bearing layer (530) forms a plurality of slings (690, 691) which extend around sling bolts (692) that are attached to the connection element (660).

22. A wind power device for converting wind energy into electric energy, in particular a wind power device according to one of claims 1 to 11 , comprising a wind power station (600) with one or more electric power generators (601) that are adapted to convert wind power into electric energy, when the wind power station (600) is airborne; a ground station (1) with a lightning rod (290) for protecting the wind power device from lightning; and a tether (500) for transferring the electric energy generated by the one or more electric power generators (601) to the ground station (1); characterized in that the lightning rod (290) is retractable, in particular by a motor, in order to not interfere with the wind power station (600) or with the tether (500) during landing and launching operations.

23. An electric cable (850), in particular a high voltage cable, preferably an electric cable of a wind power device according to one of claims 1 to 11, comprising an elastic core (512); and at least one layer of one or more electric conductors (890) helically wound around the elastic core (512); characterized in that one or more longitudinal elastic buffers (891) are provided between the helical windings of the one or more electric conductors (890), in order to prevent direct contact of the windings of the one or more electric conductors (890).

24. The electric cable (850) according to claim 23, wherein at least two layers of one or more helically wound electric conductors (890) are provided, and wherein a low friction layer (892) is arranged between each pair of adjacent layers of electric conductors (890).