WO2015124365A1

WO2015124365A1 - Lightning arrester

Info

Publication number: WO2015124365A1
Application number: PCT/EP2015/051128
Authority: WO
Inventors: John Nieuwenhuizen
Original assignee: Siemens Aktiengesellschaft
Priority date: 2014-02-18
Filing date: 2015-01-21
Publication date: 2015-08-27
Also published as: DE102014202951A1

Abstract

The invention relates to a lightning arrester (1) for a rotor blade (2) of a wind turbine (5), comprising an electrically conductive plate (10) for introduction into the interior (20) of the rotor blade (2), an electrically conductive pin (11) which is passed through the plate (10) and which has at least one externally located end region (110) having a first coupling element (111), said lightning arrester further comprising at least one electrically conductive receiver (12) having a second coupling element (121), wherein a receiver (12) is coupled by means of first and second coupling elements (111, 121) to the pin (11). The invention further relates to a rotor blade and to a wind turbine.

Description

description

Lightning Protection Device The invention describes a lightning protection device, a rotor blade and a wind turbine.

The wind turbines of a wind turbine are generally placed in the most exposed position possible. Therefore, it is important to protect a wind turbine from lightning. Various lightning protection devices are known. For example, a lightning protection device may comprise a plurality of receptors at exposed locations of the wind turbines, in particular at the rotor blade ends, since a rotor blade is particularly endangered due to its length and its narrow shape. Such a receptor is connected to a lightning current lead. The receptor gives a defined impact point, and the lightning current is dissipated via the lead - for example, a lightning protection cable inside the rotor blade or along the leaf edges - via a grounding cable into the ground or seabed. Thus, a lightning protection device provides the lightning current a defined and preferably low-impedance current path in the direction of the earth. To effectively serve as a fulcrum, often an electrically conductive receptor is attached to the outside of the front and / or rear of the rotor blade and bolted to an electrically conductive solid block in the blade interior. The block is in turn connected to the lightning current lead. In general, the block is provided with a threaded bush, so that a receptor placed outside on the rotor blade can be screwed into the block through the outer wall of the rotor blade. A lightning strike will usually strike the outer end of an exposed object - for example, the outer tip of a rotor blade. Due to the aerodynamics, but also to reduce noise, a rotor blade tip runs quite flat out. In the known lightning protection devices, however, the block must have a certain thickness in order to allow a stable screw connection with one or more receptors. The known lightning protection devices therefore have

the disadvantage that the block can be installed only where the sheet provides a sufficiently large cavity. The larger the block, the closer to the hub it must be installed. Accordingly, a receptor screwed to the block has a disadvantageously large distance from the thin tip of the blade, so that the protective effect of such a lightning protection device is not always guaranteed.

Furthermore, block and receptor must be produced from a corrosion-resistant, highly conductive material. Generally, such components are made of stainless steel. Due to the required block thickness, such a lightning protection device contributes significantly to the overall weight. Another disadvantage of the known lightning protection devices is that the preparation of one or more internal thread in the hard steel is very complex and correspondingly expensive.

It is therefore an object of the invention to provide an improved and cheaper lightning protection device for a wind turbine.

This object is achieved on the one hand by a lightning protection device according to claim 1, by a rotor blade according to claim 14 and by a wind turbine according to patent claim 15.

The lightning protection device according to the invention for a rotor blade of a wind turbine comprises an electrically conductive plate for insertion inside the rotor blade and an electrically conductive pin guided through the plate, which has at least one outer end area provided with a first coupling element, and at least one with a second coupling element provided with electrically conductive receptor, wherein a receptor is coupled by means of first and second coupling elements outside of the rotor blade with the pin. An advantage of the lightning protection device according to the invention is that a coupling of the pin takes place with one or more receptors outside of the rotor blade. Thus, the plate does not have to be provided with an internal thread. Consequently, the plate must be made of a 'soft' material, since a screw connection between plate and receptor is not needed. The lightning protection device can thus be manufactured comparatively cheap. Another advantage of the lightning protection device according to the invention is that the plate thickness does not depend on a minimum depth of thread, since the plate does not have to be coupled directly to a receptor. Thus, the plate can be comparatively thin and advantageously be introduced far in the direction of the blade tip. The rotor blade according to the invention comprises at least one such lightning protection device. At least one receptor can each be mounted on the front or rear side of the rotor blade. An advantage of the rotor blade according to the invention is that the effectiveness of the lightning protection device is increased by the shortened proximity of the receptor to the blade tip and the life of the rotor blade can be correspondingly long. Also, the total weight and the cost of the rotor blade can be kept relatively low, since a massive block of heavy steel inside the blade does not need to be installed.

The wind turbine according to the invention comprises at least one such rotor blade. As a rule, three rotor blades are attached to the hub of a wind turbine. In order to conduct the lightning current in a controlled manner, the discharges from the rotor blades are connected to the hub. Generally allows an arrangement made of carbon fiber brushes or similar a forwarding of the lightning current in a ground line, which leads for example through an outer wall of the nacelle and further through the tower in the direction of the bottom or seabed.

An advantage of the wind turbine according to the invention is that the lightning protection devices for the rotor blades are relatively cheap and at the same time have a high efficiency. Thus, the wind turbine is reliably protected from the consequences of lightning.

The dependent claims and the following description contain particularly advantageous developments and refinements of the invention, wherein in particular the claims of one claim category can be developed analogously to the dependent claims of another claim category.

As already mentioned, a receptor on the outside of the sheet is electrically connected to a lead in the blade interior, so that the lightning current can be conducted to the earth conductor. In the following it is assumed that the plate is electrically connected inside the blade with such a lightning arrester. For example, the Abieiter can be held between the plate and a suitable clamping element.

Preferably, edges of the lightning protection device have a rounding, e.g. the plate is preferably made without sharp edges. Such rounded edges prevent the formation of a corona leader, i. a hot plasma channel, which could promote a discharge inside the leaf.

Coupling between a receptor and the stylus can be achieved in different ways. For example, the pen and receptor can be plugged together by a suitable plug connection or a suitable snap closure. In a particularly advantageous embodiment have first and second coupling elements complementary threads, so that receptor and pin can be screwed together. For a screw connection between pin and receptor one of the two objects to be screwed is provided with an external thread, and the other is provided with an internal thread. In one possible embodiment of the invention, the pin could have an internal thread in the end region, and the receptor could be provided with a projecting screw. Thus, the receptor can be in the pen

be screwed into it. In a particularly advantageous embodiment, however, the pin has an outer thread at an outer end, while the receptor is equipped with a corresponding threaded bushing. Thus, the receptor can be screwed onto the pin like a threaded nut. The external thread must thus be worked only at the outer end of the pin. The pin can be guided by the blade inside through the plate and an outer wall of the rotor blade. In this embodiment, the pin may be provided at the end remaining in the rotor blade with a head which is used on the plate when the receptor is screwed on the outside of the other pin end. In this embodiment, some space in the blade interior is needed to move the pen from inside to outside. In a particularly advantageous embodiment, the pin is guided from outside the rotor blade through the receiving block. Thus, the relatively flat receiving block can advantageously be accommodated deep in the blade interior in the direction of the blade tip. Particularly preferably, the plate is embedded or introduced in the outermost end of the blade tip. The rotor blade is - during or after completion - provided with appropriate through holes. For example, two simple circular through holes can be sawn on opposite rotor blade sides per pin or milled out. In such an embodiment, the pin may have two outer end portions of sufficient length, ie, the pin may "overhang" upon insertion on both sides of the rotor blade, and then two receptors may be attached or screwed to these overhanging end portions.

In a particularly advantageous embodiment, the plate for the passage of the pin on a smooth Durchgangsboh- tion. By this is meant that the through hole is machined without thread. For example, the through-hole may be formed as a simple bore having a substantially circular cross section for receiving a corresponding cylindrical pin.

Of course, pin or through hole may have any but complementary shapes. For example, pin and through hole each have a substantially rectangular cross-section. In order to reliably guide the lightning current from the receptor to the plate and then to a lead laid inside the blade, there is preferably an electrical contact between these components. In a particularly advantageous embodiment, a washer is placed between the plate and the receptor. When screwing a receptor, the corresponding washer between the receptor and plate is squeezed. Particularly preferred is a washer made of a deformable and highly conductive material. For example, a washer made of aluminum can be manufactured.

In a further preferred embodiment, through-hole and pin have a tapered shape. With regard to the pin, it is sufficient if this has a tapered shape in the area of the through hole. The end portions may have a simple cylindrical shape. If a receptor is attached to one or both end regions of the pen under tension, for example by The tapered portion offers a beneficial counteracting effect, particularly when the receptor adjacent to the "narrow" end is attracted to a greater degree, thus allowing a tight fit between the stylus and the receptor (s).

In another embodiment, the pin, starting at one end, may have a tapered or tapered shape over most of its length, so that the pin is worked out as a 'cone' in this section. At the narrow end of the cone, the pin may have a cylindrical and externally threaded end portion for receiving a receptor. In this embodiment, the pin may be configured so that the broad tail (the 'bottom' of the cone) remains outside the rotor blade. Thus, this wide tail itself can serve as a receptor.

A thread can be worked clockwise or anti-clockwise. If the pin is provided with an external thread on both end areas, one can be left-handed and the other clockwise. In a particularly advantageous embodiment, however, the direction of rotation of the thread on both end pieces of the pin is the same. For example, a right-handed external thread is worked out at both ends. In this embodiment, each receptor provides the other with an advantageous counter-pull during tightening.

A lightning current can amount to several thousand amperes, and values of 300 kA - 400 kA can be exceeded. To withstand such a high current and to lead to the derivative, a receptor is preferably prepared as a solid solid. For example, a receptor can be made as a block or thick slice. Preferably, a good-conducting, stainless metal is used, for. As stainless steel.

The plate is as solid as possible, to lead a high current as directly as possible to the derivative. Because the plate is relatively thin, an advantageous high mass is instead achieved by a larger area. In a particularly preferred variant of the invention, the plate has a maximum thickness of 3 - 5 mm. The width and thickness of the plate are determined by a required conductor cross-section. For example, a plate of copper preferably has one

Cross-sectional area of at least 50 mm ² .

Since the pin fulfills an important function as an electrical connection between receptor and plate, it should also have the highest possible mass. A maximum length of the pen is z. T. determined by the leaf thickness in the receptor area and the strength of the receptors. Therefore, an advantageous high mass of the pin can be achieved by a suitable diameter. In a particularly preferred

Variant of the invention, the receptor has a diameter of about 20 - 30 mm to accommodate a pin with a diameter of 8 - 12 mm can. The invention will be explained in more detail below with reference to the accompanying figures with reference to embodiments. Show it:

Figure 1 shows an embodiment of an inventive

Lightning protection device;

Figure 2 is a perspective view of a plate of Figure 1;

Figure 3 is a perspective view of a pin of Figure 1;

Figure 4 is a perspective view of a receptor of Figure 1;

Figure 5 shows another embodiment of a lightning protection device 1 according to the invention;

FIG. 6 shows a further exemplary embodiment of a lightning protection device 1 according to the invention;

Figure 7 shows a part of a lightning protection device according to the prior art. FIG. 1 shows an exemplary embodiment of a lightning protection device 1 according to the invention. The lightning protection device 1 is installed in the rotor blade tip 21 of a rotor blade 2. The main components of the lightning protection device 1 in this embodiment are an electrically conductive plate 10 housed inside the rotor blade 2, and two electrically conductive receptors 12 externally mounted on both sides of the rotor blade 2. Through a through hole in the plate 10, the pin 11 can be pushed from the outside through the plate 10. The pin 11 has an external thread on both end regions 110, and a receptor 12 is screwed on each of the two end regions 110. Simply by tightening the receptors 12 creates an advantageous inward pulling force F, which pulls the receptors to the washers 13 and the washers 13 to the plate. This results in a reliable electrical connection between receptors 12 and plate 10th

Due to the advantageous embodiment of the lightning protection device 1 according to the invention with an "outwardly displaced" coupling or screwing the plate 10 can be prepared relatively flat and moved accordingly deep into the blade tip 21. This is an advantageous short distance di between the receptor 12 and blade tip 21st allows.

Figure 2 shows a perspective view of the plate 10 of Figure 1. Preferably, the plate 10 is worked on a piece of a suitable metal. The figure shows that the plate 10 is relatively wide and flat. In this example, the plate 10 may have a thickness Si ₀ of only 3.0 mm, so that the plate 10 far into the

Blade tip can be accommodated. The breadth of organic

Plate is then determined based on the required conductor cross-section. For example, a plate 10 made of copper may have a conductor cross-section of 50 mm ² , so that an appropriate sene width bio of about 18 mm could be chosen for this example. A hole 100 or a through hole 100 is milled or drilled for the later recording of

Pin. The plate 10 is preferably made of a relatively 'soft' material, for. As aluminum or an aluminum alloy. Such a soft metal can be used, since the preparation of a thread on the through hole 100 is dispensed with. Rather, the through hole 100 may have a simple or smooth inner wall 101. A lightning current lead 3 is clamped between the plate 10 and a terminal block 4 by means of screws 40. As a result, an advantageous transition between the plate 10 and lightning current 3 is guaranteed. The lightning current lead 3 can be led over the length of the rotor blade in the direction of the hub. As mentioned above, the plate is made without sharp edges to prevent the formation of a 'corona leaders' inside the blade. A 'leader' can therefore arise only from the receptor 12, so that a lightning strike is conducted exclusively through the receptor 12 via the plate 10 to the lightning current discharge 3.

Figure 3 shows a perspective view of the pin 11 of Figure 1. The pin 11 can be made in one piece of a suitable 'hard' metal, for. For example, be made of corrosion-resistant steel. At its two end regions 110, the pin 11 has an external thread 111. This can be worked out as left-handed or right-handed thread 111. As already mentioned, both threads preferably have the same rotation, z. B. the threads are clockwise in both cases. In the middle region 112-ie, the area later in the rotor blade-the pin 11 can have a simple, smooth surface. The diameter Du of the pin 11 is determined on the basis of a desired volume (eg in order to be able to guide a certain maximum lightning current) and a predetermined length (for example the distance between the opposite sheet outer sides in the region of the pin 11). Figure 4 shows a perspective view of a receptor 12 of Figure 1. This can also be in one piece from a suitable 'hard' metal, for. B. made of corrosion-resistant steel. The receptor may have a height H ₁₂ of 10 - 30 mm. The receptor 12 has a threaded bushing 120, with a thread 121 which has been worked out to the thread 111 at the end portion 110 of the pin 11. Thus, the receptor 12 can be easily bolted to the pin 11. If both external threads 111 have the same rotation, two receptors 12 can simply be screwed onto the pin in the opposite direction. As a result, an advantageously high compression can be achieved, so that a long-lasting screw connection is formed.

FIG. 5 shows a further exemplary embodiment of a lightning protection device 1 according to the invention. The figure shows a conically extending pin 11 'with a first, wide end region 113 and a second, narrow end region 110. Correspondingly, passage openings 213, 210 having different diameters are developed in the rotor blade 2. In this embodiment, the plate 10 has a conical passage 100 '. The pin 11 'can thus be pushed by one side of the rotor blade 2 through the plate 10. The narrow end portion 110 is provided with an external thread 111 as described above, so that a receptor 12 can be screwed on, and a washer 13 between receptor 12 and plate ensures a satisfactory electrical contact. The broad end portion 113 of the "wedge" is designed so that it projects slightly above the leaf surface, and thus serves as receptor 12 'The conical fit of the wide end portion 113 and the passage 100' provides a counterforce when screwing, so that the pin 11 'is pressed in the central area against the side walls of the conical passage 110' The resulting pressure ensures an advantageous electrical connection between receptors, pin 11 'and plate 10. Here is also a advantageously short distance di between receptor 12, 12 'and blade tip 21 possible.

FIG. 6 shows a wind turbine 5 according to the invention with three rotor blades 2. Each rotor blade 2 has a lightning protection device 1 according to the invention in the blade tip 21. A lightning strike on a receptor 12 can thus be safely led to a lightning current dissipation in the blade interior, to then be passed through a ground line 30 through hub 50, nacelle 51 and tower 52 in the ground or seabed.

Figure 7 shows a part of a lightning protection device according to the prior art. In this case, a block 70 is installed in the interior of the blade and a receptor 71 is attached to the outside of the rotor blade 2. The receptor 71 is provided with a threaded pin 72 which is screwed into a threaded bushing 73 of the block 70 in the blade interior. A lightning current lead 3 is clamped between block 70 and leaf inner surface. As

As already explained above, the block 70 must have sufficient mass to withstand the lightning current. In addition, the block 70 must have sufficient for the preparation of the threaded bush 73 material thickness S ₇ o in order to receive the threaded pin 72 satisfactorily. This required material thickness S ₇₀ in turn means that the block 70 - and consequently also the receptor 71 - must occupy a disadvantageous large distance d ₇ to the blade tip 21.

It is finally pointed out again that it is in the structures described above to exemplary embodiments and that the basic principle can be varied within a wide range by those skilled in the art, without departing from the scope of the invention, as far as it is specified by the claims. In particular, it is possible to make the shape of the main components - namely plate, pen and receptor - arbitrary. Several pins can be passed through a plate; an oblong shaped receptor can be attached to two pins, etc. It will be the For the sake of completeness, it should also be noted that the use of the indefinite article does not exclude "a" or "an" that the characteristics in question may also be present multiple times.

Claims

claims

1. Lightning protection device (1) for a rotor blade (2) of a wind turbine, with

- An electrically conductive plate (10) for insertion in the interior (20) of the rotor blade (2), and

an electrically conductive pin (11, 11 ') guided through the plate (10) and having at least one outer end area (110) provided with a first coupling element (111), and

at least one electrically conductive receptor (12) provided with a second coupling element (121),

wherein a receptor (12) is coupled to the pin (11, 11 ') by means of first and second coupling elements (111, 121).

2. Lightning protection device according to claim 1, characterized in that first and second coupling elements (111, 121) have complementary threads (111, 121).

3. Lightning protection device according to claim 1 or 2, characterized in that the first coupling element (111) comprises an external thread (111) and the second coupling element (121) comprises an internal thread (121).

4. Lightning protection device according to one of claims 1 to 3, characterized in that the pin (11, 11 ') from outside the rotor blade (2) through the receiving block (10)

passed through.

5. Lightning protection device according to one of claims 1 to 4, characterized in that the plate (10) has a smooth through hole (100) for receiving the pin (11, 11 ').

Lightning protection device according to claim 5, comprising at least one washer (13) for forming an electrical contact between the plate (10) and the receptor (12).

7. lightning protection device according to one of claims 1 to 6, characterized in that the pin (11) has two on the opposite outer surfaces of the rotor blade (2) outer end portions (110).

8. Lightning protection device according to claim 7, characterized in that the threads at the end regions (110) of the pin (11) have the same direction of rotation.

Lightning protection device according to one of claims 1 to 8, characterized in that the receptor (12) comprises a solid body (12) made of stainless steel.

10. Lightning protection device according to one of claims 1 to 9, characterized in that the plate (10) in the outermost end of the blade tip (21) is embedded.

11. Lightning protection device according to one of claims 1 to 10, characterized in that the plate (10) has a thickness

(Sio) has a maximum of 5.0 mm.

12. Lightning protection device according to one of claims 1 to 11, characterized in that the pin (11) has a diameter (Du) of at least 8.0 mm.

13. Lightning protection device according to one of claims 1 to 12, characterized in that the plate (10) in the blade interior with a lightning current arrester (3) is electrically connected.

14. rotor blade (2) with at least one lightning protection device (1) according to claims 1 to 13.

15. Wind turbine (4) with at least one rotor blade (2) according to claim 14.