SE520775C3 - switchgear Station - Google Patents

Description

5 35 520 775 mainly relates to the magnetic circuit of such a machine and how it is constructed according to classical technology. Since the magnetic circuit referred to in most cases is in the stator, the magnetic circuit below will generally be referred to as a stator with a laminated sheet metal core, the winding of which will be referred to as stator winding, and the grooves in the sheet metal core of the winding will be referred to as stator grooves or entirely. single track.

Most synchronous machines have a field winding in the rotor, where the main flow is generated with direct current, and an alternating current winding Sometimes the latter in the stator. The synchronous machines are usually three-phase. the synchronous machines are designed with distinct poles. has the AC winding in the rotor.

The stator body for larger synchronous machines is often made of sheet steel with a welded construction. The sheet metal core is normally made of lacquered 0.35 or 0.5 mm sheet metal. For larger machines, the sheet metal is punched in segments that are attached to the stator body with the sheet metal core, wedges / salmon are held together. with pressure fingers and pressure rings.

For cooling the windings of the synchronous machine, three different cooling systems are available. During air cooling, both the stator and rotor windings are cooled by flowing cooling air. The cooling air ducts are also found in the stator plate soni in the rotor. For radial ventilation and air cooling, the sheet metal core is at least for medium-sized and large machines divided into packages with radial and axial ventilation ducts embedded in the core.

The cooling air can consist of ambient air, but at higher effects, mainly closed, cooling systems with heat exchangers are used.

Hydrogen cooling is used in turbo generators and in large synchronous compensators. The cooling method works in the same way as for air cooling with heat exchangers, but instead of air using hydrogen gas. The hydrogen gas here has a better cooling capacity than air, but difficulties arise with seals and monitoring for leaks. For turbogenerators in the higher power range, it is known to apply water cooling of both the stator and rotor windings. The cooling channels consist of tubes that are placed inside conductors in the stator winding. A problem for large machines is that the cooling tends to be uneven and that there are thus temperature differences across the machine.

The stator winding is placed in grooves in the sheet metal core and where the grooves usually have a cross section like a rectangle or like a trapezoid. Each winding phase consists of a number of series-connected coil groups and each coil group of a number of series-connected coils. The different parts of the coil are called the coil side for the part that is placed in the stator and the coil for the part that A coil consists of one or height and / or width. Between each conductor there is a thin insulation, eg epoxy / fiberglass. is outside the stator. several conductors combined in the Harness are insulated against the groove with a harness insulation, ie an insulation intended to withstand the rated voltage of the machine against earth. Various plastic, lacquer and fiberglass materials can be used as insulation material. Commonly used so-called Mica tape, which is a mixture of mica and hard plastic, specially developed to provide resistance to partial discharges, which can quickly break down the insulation. The insulation is applied to the skein by wrapping the Mica tape around the skein in several layers. The insulation is impregnated and then the coil side is painted with a carbon-based paint to improve the contact with the surrounding stator which is connected to earth potential.

The conductor area of the windings is determined by the current current and by the cooling method. Conductors and coils are usually designed with a rectangular shape to maximize the amount of conductor material in the groove.

A typical tangle is formed by so-called ruble rods, where some of the rods can be made hollow for coolant. A ruble rod consists of a plurality of rectangular, parallel-connected copper conductors, which are transposed 360 degrees along the track. Ringlandsta- var med. 540 degree transpositions and other transpositions also occur.

The transposition is necessary to avoid the occurrence of circulating currents generated in a cross section of the conductor material seen from the magnetic field.

For mechanical and electrical reasons, a nmskin can not be made as large as possible. The machine power is mainly determined by three factors: - The conductor area of the windings. At normal operating temperature, for example, copper has a maximum value of 3-3.5 A / mmz.

- Maximum flux density (magnetic flux) in the stator and rotor material.

- Maximum electric field strength in the insulating material, the so-called electric strength.

Multiphase AC windings are made as single- or two-layer windings. For single-layer windings there is only one warp side per track, for two-layer windings two warp sides per track. Two-layer windings are usually performed as transition windings, while in this context current single-layer windings can be performed as transition windings or planar windings. In the case of transition winding, only one (or possibly two) torsional widths occur, while planar windings are carried out as concentric windings, ie with widely varying torsional widths. Twisting width refers to the distance in arc dimensions between two twisting sides belonging to the same twist, either in relation to the actual pole division or in the number of intermediate track divisions. Usually different variants of coding are applied, eg step shortening to give the winding desired properties. The winding type mainly describes how the coils in the grooves, the coil sides, are connected outside the stator, ie at the coil ends.

Outside the stator's sheet metal package, the coil is not provided with a painted semiconducting earth potential layer. The end face is normally provided with an E-field guide in the form of so-called glow protection varnish to convert a radial field to an axial field, which means that the insulation on the end faces ends up at a high potential relative to earth. This sometimes gives rise to glimmers. rotary electric machine.

Normally, all larger machines are made with 2-layer winding and equally large skeins. Each tangle is placed with one side in one This means With more than two layers, these intersections complicate winding work and the layer and the other side in the other layer. that all coils cross each other in reverse. impairs reversal.

It is generally known that the connection of a synchronous machine / generator to a power grid must take place via an A / Y-connected so-called "step-up" transformer, since the voltage of the power grid is generally at a higher level than the rotating voltage of the electric machine. This transformer thus, together with the synchronous machine, forms integral parts of a plant.

The transformer is an extra cost and also has the disadvantage that the overall efficiency of the system is reduced.

Thus, if it were possible to manufacture machines for significantly higher voltages, the "step-up" transformer can be excluded.

In recent decades, there has been a desire for rotary electric machines for higher voltage than has been possible to design and manufacture before. The maximum voltage level which, according to the state of the art, has been possible to achieve for synchronous machines with a good yield in the coil production is 25-30 kV.

Some attempts at new thinking regarding the design of synchronous machines are described, among other things, in an article "Water-and-oil-cooled Turbogenerator TVM-300" in J. Elektrotechnika, Nr. 1,970, pages 6-8, in US 4,429,244 "Stator of generator" and in Russian patent specification CCCP patent 955369. The water and oil cooled synchronous machine described in J.

Electrical engineering is intended for voltages up to 20 kV. The article describes a new insulation system consisting of completely Oil can then be used as cooling oil / paper insulation, which makes it possible to soak the stator in oil. dium while being used as insulation. To prevent there is at the core the Stator winding is made of conductors with an oval hollow shape oil in the stator to leak out towards the rotor, inner surface a dielectric oil separating ring. fitted with oil and paper insulation. The warp sides with their insulation are fastened in the grooves formed with a rectangular cross-section by means of wedges. Oil is used as a coolant both in the hollow conductors and in holes in the large walls. Such cooling systems, however, mean that there will be a large number of connections of both oil and electricity at the reversers. The thick insulation also means an increased radius of curvature on the conductors, which in turn leads to an increased size of the coil alignment.

The above-mentioned U.S. patent relates to the stator part of a synchronous machine which comprises a magnetic core of laminated sheet metal with trapezoidal grooves for the stator winding. The grooves are tapered because the need for insulation of the stator winding is less towards the rotor where the part of the winding that is located. The stator part includes closest to the neutral point is located. in addition, a dielectric oil separating cylinder closest to the inner surface of the core. This part may increase the need for networking relative to a machine without this ring. The stator winding is made of oil-soaked cables with the same diameter for each twist bearing. The bearings are separated from each other by means of spacers in the grooves and secured with wedges. What is special about the winding is that it consists of two so-called half-windings connected in series. One of the two half-windings is centrally located inside an insulating sleeve. The stator winding conductors are cooled with ambient oil. A disadvantage of so much oil in the system is the risk of leakage and the large remediation work that can result from a fault condition. The parts of the insulating sleeve that are located outside the grooves have a cylindrical part and a conical shield electrode whose task is to control the electric field strength in the area where the cable leaves the plate.

CCCP 955369 states in another attempt to increase the rated voltage of the synchronous machine that the oil-cooled stator winding consists of a high-voltage cable with the same dimension for all bearings. The cable is placed in stator grooves shaped as circular radially placed openings corresponding to the cross-sectional area of the cable and the necessary location of coolant. surrounded by and fixed in insulating pipes. for fixing and The various radially placed bearings of the winding Insulating spacers fix the pipes in the stator groove. Due to the oil cooling, an inner dielectric ring is also needed here for sealing the oil coolant against the inner air gap. The construction shown has no stepping of the insulation or of the stator grooves.

The construction has a very narrow radial waist between the various stator grooves, which means a large groove leakage flow which significantly affects the magnetization needs of the machine.

A report from the Electric Power Research Institute, EPRI, EL-3391 from April 1984 presents a review of machine concepts for achieving higher voltage in a rotating electric machine in order to be able to connect a machine to a power grid without an intermediate transformer. Such a solution is judged by the inquiry to provide good efficiency gains and major economic benefits. The main reason why it was considered possible in 1984 to start developing generators for direct connection to power grids was that. a superconducting rotor had then been developed. The large magnetizing capacity of the superconducting field makes it possible to use air of sufficient thickness to stand and combine it to construct one against the electrical stresses. According to the project's most promising concept 10 l5 20 25 35 520 775 magnetic circuit with winding, so-called "monolithhe cylinder armature", a concept where two cylinders of conductors are enclosed in three cylinders of insulation and the whole structure is attached to an iron core without teeth, the assessment was made that a rotating electric machine for high voltage could be directly connected to a power grid. The solution meant that the main insulation had to be made thick enough to withstand network-to-network and network-to-ground potentials. Obvious disadvantages of the proposed solution are that in addition to requiring a superconducting rotor, a very thick insulation is required, which increases the machine size. The invaders. must be insulated and cooled with oil or freons to control the large electric fields The entire machine must be hermetically sealed to prevent the liquid dielectric from absorbing moisture at the ends. from the atmosphere.

The above report consequently shows that today's switchgear stations leave a lot to be desired.

This is conditioned both by the generator design itself and by the fact that according to conventional technology “step-up” transformers are required.

It is pointed out that the term switchgear station here refers to a station which is intended for the collection and / or distribution of electrical energy and includes equipment required for this activity, including, among other things, equipment for connection and monitoring.

SUMMARY OF THE INVENTION The object of the present invention is primarily to provide a switchgear station, in which at least one or some of the disadvantages discussed above, which are known +. . . . technology, eliminated. The primary object is achieved by means of a station of the type defined in the appended claims, and then immediately in claim 1.

In a broad sense, it is stated that the design according to the invention, by creating the possibility to contain mainly the electric field arising due to said electric conductor in the insulation system, reduces losses which occur so that consequently the machine can operate with a higher efficiency. The reduction of the losses in turn gives rise to a lower temperature in the device, which reduces the cooling demand and means that any existing cooling devices can be designed more easily than in the absence of the invention.

The conductor / insulation system according to the invention can be realized as a flexible cable, which entails significant advantages in terms of manufacture and assembly compared with hitherto conventional rigid windings in prefabricated form. The insulation system used according to the invention also means a lack of gaseous and liquid insulation media.

The rotating electric machine according to the invention thus creates conditions for operation with such a high voltage that the previously mentioned "step up" transformer can be excluded. The machine can thus be operated with significantly higher voltage than machines according to the state of the art for making a direct connection to an electric power grid. This entails significantly lower investment costs for systems with a rotating electric machine and the system's overall efficiency can be increased. The invention eliminates the need for special field control measures at certain areas of the winding, which field control measures have been necessary according to prior art.

A further advantage is that the invention makes it easier to provide under- and over-magnetization for the purpose of reducing reactive effects which occur when voltage and current are out of phase with each other. This makes the switchgear station as a whole more efficient through reduced losses. In addition, the station as a whole will be simplified so that it not only becomes cheaper but also takes up less space.

The design of the winding so that along at least a part of its length comprises an insulation formed of a solid insulating material, inside this insulation an inner layer and outside the insulation an outer layer with these layers of containing it. field in the entire machine within the winding. "although the term insulating material is used here" the winding shall have no liquid or gaseous insulation, for example in the form of oil. Instead, the insulation is intended to be formed of a polymeric material. The inner and outer layers are also formed of a polymeric material, however a semiconducting one.

The inner layer and the solid insulation are firmly connected to each other over substantially the entire interface. The outer layer and the solid insulation are also firmly connected to each other over substantially the entire interface therebetween. The inner layer has a potential equalizing and thus equalizing with respect to the electric field outside the inner layer as a consequence of its semiconducting properties. The outer layer is likewise intended to be formed of a semiconducting material and has at least an electrical conductivity which is higher than that of the insulation in order for the outer layer to have a relatively equal potential due to relatively otherwise low ground or to be able to function as a potential equalizer. mainly contain it due to said electrical conductor layer. Å _ g. A +. HRS . When the electric field is inside the outer other side, the outer layer should have a resistivity which is sufficient to minimize the electric losses therein.

The solid connection between the insulating material and the inner and outer semiconducting layers must be so uniform over substantially the entire interface that no cavities, pores or the like occur. At the high voltage levels referred to in the invention, the electrical and thermal loads that may occur will place extremely high demands on the insulation material. It is known that so-called partial discharges, PD, generally pose a serious problem for insulation materials in high-voltage installations. If cavities, pores or the like occur, internal corona discharges can occur at high electrical voltages, whereby the insulation material gradually breaks down and this can eventually. This can The insulation should lead to electrical penetration through the insulation. cause serious breakdowns in the nmskinen. thus being homogeneous.

The inner layer inside the insulation shall have an electrical conductivity which is lower than that of the electrical conductor but sufficient for the inner layer to function as a potential equalizer refers to the electric field outside the inner layer. and thus leveling what This in combination Ined the insulation over substantially the entire interface, ie the absence of cavities etc, means a substantially uniform electric field outside the inner layer and minimal risk of PD.

It is preferred that the inner layer and the solid insulation consist of materials with substantially equal coefficients of thermal expansion. The same is preferred as far as it ..4_4. A 1, -I *. + - ^ + - h »l -F 4- '1' '" the outer layer and the rust insulation. temperature change 10 15 20 25 30 u) (fl 520 775 12 ar expands and contracts uniformly as a monolithic part without these temperature changes giving rise to any destruction or disintegration in the interfaces.

Thus, intimacy in the contact surface between the inner and outer layers and the solid insulation is ensured and it is a prerequisite to maintain this intimacy for long periods of operation.

It is further pointed out that it is essential that the materials in the inner and outer layers and in the solid insulation have high elasticity so that the materials are able to withstand the stresses that arise when the cable is bent and when the cable is subjected to thermal stresses during operation. Of particular importance is a good adhesion between the solid insulation and the inner and outer layers and a high elasticity of these layers and the solid insulation, respectively, in the event that the materials in the layers and the solid insulation would not be of substantially equal coefficients of thermal expansion. In addition, it is advantageous that the materials in the inner and outer layers and in the solid insulation have substantially equal elasticity (E-modulus), shear stresses "in the boundary zone between the layers and the solid something which will counteract the formation of the insulation.

It is further pointed out that it is essential that the materials in the inner and outer layers and in the solid insulation have high elasticity so that the materials are able to withstand the stresses that arise when the cable is bent and when the cable is subjected to thermal stresses during operation. Particularly important is a good adhesion. Between the solid insulation and the inner and outer layers and a high elasticity of these layers and the solid insulation, respectively, in the event that the material in the layers and the solid insulation would not have significant coefficients of thermal expansion. In addition, it is advantageous- QJ _11. _LI \ FJ that the materials in the inner and outer layers and in the solid insulation have substantially equal elasticity, slightly 10 15 20 25 35 520 775 ¿¿¿: ggize, 13 shear stresses in It will counteract the formation of the boundary zone between the layers and the solid insulation. It is explained that the materials in the inner and outer layers and in the solid insulation have an E-modulus that is less than 500 MPA, 200 MPA. In order to be able to form windings by means of the cable, it is essential that its flexibility is preferably less than hot. It is preferred that the cable be capable of being subjected to bending without adversely affecting the function, with a radius of curvature being 20 times the cable diameter or less, preferably 15 times the cable diameter or less. It is preferred that the cable should be able to bend to a radius of curvature of 4 to 5 times the cable diameter or even smaller without compromising adequate function.

The electric load on the insulation system decreases as a result of the fact that the inner and outer layers of the insulating material around the insulation will tend to constitute substantially equipotential surfaces and that the electric field in the insulation itself will be distributed relatively evenly over the thickness of the insulation.

It is known that high voltage cables for the transmission of electrical energy can be built up of conductors with an insulation of a solid insulation material with inner and outer layers of semiconducting material. When transferring electrical energy, it has long been established that the insulation must be free from defects. In the case of high-voltage cables for transmission, however, the electrical potential does not change along the length of the cable, but the potential is in principle at the same level. However, even with high-voltage cables for transmission use, transient predominant potential differences can occur due to, as in the case of lightning strikes. According to the present invention, the electromagnetic device is used as a winding '1. + - 4-' 1 'in a design according to the following claims. A further improvement can be achieved by the fact that the electrical conductor in the winding is built up of lower so-called strands, from each other. of which at least some are isolated By making these parts with a relatively small cross-section, preferably approximately round, the magnetic field over the parties will have a constant geometry in relation to the field and the occurrence of eddy currents is thereby minimized.

According to the invention, the winding thus preferably consists of a cable comprising the electrical conductor and the one described, the inner insulation system of the conductor extending around the conductors' parts. Outside this inner semiconductor layer is the main insulation of the cable in the form of a solid insulating material.

According to the invention, the outer semiconductor layer must exhibit such electrical properties that a potential equalization along the conductor is ensured. However, the outer layer must not exhibit such conductive properties that a current will be conducted along the surface, which would give rise to losses. For those (at ) as defined in the following claims 5 and 6. the semiconductor layer must have sufficient electrical conductivity to ensure equipotential bonding of the electric field, but at the same time this layer must have such resistivity that the confinement of the electric field is ensured.

It is important that the inner layer evens out irregularities in the conductor surface and forms an equipotential surface with a high surface finish at the interface with the solid insulation. The inner layer can be formed with varying thickness but to ..1 ensure a smooth surface with. with respect to the leader. and in the solid insulation, the thickness is suitably between 0.5 and 1 mm.

One such flexible winding cable which is used according to the present invention in its rotating machine is a further development of the PEX cable used per se for transmission purposes or a cable with EP rubber insulation. The further development includes, among other things, a new design both as far as the parts of the electrical conductor are concerned and also that the cable, at least in certain designs, is not intended to have any outer casing for mechanical protection of the cable.

However, it is possible according to the invention that a conductive metal shield and an outer jacket are arranged outside the outer semiconducting layer. The metal screen will thereby acquire the character of external mechanical and electrical protection, for example against lightning strikes. It is preferred that the inner semiconductor layer be at the potential of the electrical conductor. For this purpose, at least one of the strands of the electrical conductor is intended to be uninsulated and arranged so that good electrical contact is achieved with the inner semiconductor layer. Alternatively, different strands may be alternately conductive. The decisive advantage of a cable-shaped winding according to the invention is that the electric field is enclosed in the winding and that there is thus no electric field outside the outer semiconductor layer. the electric field appears only in the fixed main isolation- The provided ring.

A significantly reduced thermal stress on the stator is achieved.

Temporary overloads of the machine thus become less critical and it becomes possible to operate the machine in case of overload for a longer period of time without risking damage. This means Fi ... HRS . s for power plant operators who in the event of disruptions today are quickly forced to switch to other equipment to ensure statutory delivery requirements. With a rotating electrical machine according to the invention, maintenance costs can be significantly reduced due to the fact that the transformer and switch do not have to be included in the system for connecting the machine to the power grid.

It has already been described above whether the outer semiconducting layer of the winding cable is intended to be connected to earth potential. The intention is that the layer along the entire length of the winding cable should be kept at substantially ground potential.

It is possible to divide the outer semiconductor layer by cutting into a number of sections distributed along the length of the winding cable, whereby each individual layer section can be connected directly to earth potential. This creates the conditions for greater uniformity along the length of the winding cable.

It has been mentioned above how the solid insulation and the inner and outer layers can be achieved by, for example, extrusion. However, other techniques are also quite possible, for example the formation of these inner and outer layers or the insulation by means of spraying on the material in question.

It is preferred that the winding cable be designed with a circular cross section. However, other cross-sections can also be used in cases where it is desired to obtain a better packing density.

To build up voltage in the rotating electrical machine, the winding cable is laid in several successive turns in grooves in the magnetic core. The winding can be designed as a multi-layered end face junction. concentric cable winding to reduce the number The cable can be made with stepped insulation to make better use of the magnetic core, whereby the design of the grooves fi). . . . . . * r can also be adapted to the tapered insulating LQ io F? 5 10 15 20 25 30 520 775 j_j; ¿§Fl @ 17 A significant advantage in the application of the invention to a rotating electric machine is that the electric field is close to zero in the reversal region outside the outer semiconductor and that with earth potential on the outer semiconductor layer the electric field is not needed controlled. This means that you can not get any field concentrations either within the core, in regions of origin or in the transition between these.

In summary, an electromagnetic device in the form of a rotary electric machine according to the invention entails a significant number of important advantages over corresponding machines according to the prior art.

First, the machine according to the invention can be connected directly to a power grid at all types of high voltage. Another significant advantage is that earth potential has been consistently carried along at least part of and preferably along the entire winding, which means that the turning region can be made compact and that bracing devices in the turning region can be applied to, in the near future, earth potential. As already pointed out above, oil-based insulation and cooling systems also disappear with rotating electrical machines. This means that no sealing problems arise and that the previously mentioned dielectric ring is no longer needed. It is also important that all forced cooling can take place at ground potential.

Brief Description of the Drawings With reference to the accompanying drawings, a more detailed description of exemplary embodiments of the invention follows.

In the drawings: Fig. 1 is a partially cut-away view showing the parts included in the current modified standard cable, 10 15 20 25 U) CÖ 35 Fig 2 Fig 3 Fig 4 Fig 5 Fig 6 Fig 7 Fig 8 Fig 9 Fig 10 520 775 18 is an axial end view of a sector / pole division of a magnetic circuit according to the invention, a schematic view illustrating prior art, i.e. a step-up transformer connected between a generator and associated switchgear, a view illustrating an inventive device according to the invention, with the step-up transformer eliminated, a perspective view illustrating a conventional generator set, a similar view illustrating the simplification that arises as a consequence of the application of the invention, an over (SVC) single-line diagram static and a switchgear according to the prior art, VAR compensation a single-line diagram over an embodiment according to the invention in contrast to the conventional one in Fig. 7, a known technique equipped with a static converter in to-back 'design with DC link, one-line diagram of a switchgear illustration according to the reverse and a single line diagram illustrating, as a contrast to the known embodiment in Fig. 9, whether one according to the invention is designed. stable station Ined rotary inverters become significantly simpler and require a smaller amount of space in comparison with the station according to Fig. 9 with static inverters. wi-šnwnnn fl mn rwrnwñnnxwnniFnnnp- * p I: unLL / nnuuvn u .L 1. ' An important condition for being able to manufacture a magnetic circuit in accordance with the invention is that for the winding having an inner semiconducting layer between the insulation and one or more turns a conductor cable with fixed electrical insulation, internal electrical conductors and with an external semiconductor cables, layers are located outside the insulation. Such as standard cables for other power engineering applications, namely power transmission. In order to be able to account for an embodiment, a brief description of a standard cable must initially be given. The internal live conductor consists of a number of strands. Around the strands there is a semiconducting inner layer or casing. Outside this semiconducting inner layer is an insulating layer of solid insulation. The solid insulation is formed from a polymeric material with. low electrical losses and high impact (PE) and (EP).

As concrete examples may be mentioned polyethylene (PEX) A metal shield and an outer semiconducting strength may be arranged around the outer semiconducting layer. especially crosslinked polyethylene and ethylene propylene insulating casing. The layers consist of a polymeric material, with an electrically conductive component, for example ethylene copolymer, for example conductive soot. Such a cable will be referred to below as a power cable.

A preferred embodiment of a cable intended as winding in the rotating electrical machine is shown in Figure 1. The cable 1 is shown in the figure as comprising a live conductor 2 which comprises transposed both uninsulated and insulated strands. Electrically machined, permanently insulated strands are also conceivable. These strands can be beaten / transposed in a number of layers. Around the conductor there is an inner semiconducting layer 3 which in turn is surrounded by a homogeneous layer of a solid insulating material. In the insulation 4,. . . There is thus a complete lack of insulation material of the liquid and gas type. The cable used as the winding in the preferred embodiment This layer 4 is surrounded by an outer semiconducting layer 10 l5 20 25 years) 0 35 520 775 20 ring shape may be provided with a metal shield and outer sheath but need not be this. In order to avoid induced currents and associated losses in the outer semiconductor layer 5, this is cut off, the alignment, preferably in the reverse direction, ie in the transitions from the sheet metal package to the twist basket. The cut-off is made so that the outer semiconducting layer 5 will be divided into several parts distributed along the cable. Each cut-off part is then connected to earth, whereby the electrically completely or partially separated outer semiconductor layer 5 will be kept apart or almost at ground potential for the entire length of the cable. This means that around the permanently insulated winding at the end faces, the touchable and, after a certain period of use, dirty surfaces only have negligible potentials to earth and that they also cause negligible electric fields.

In order to optimize a rotating electric machine, the design of the naked circuit with regard to the grooves and the teeth, respectively, is important. The grooves should be connected as close to the casing side casing It is also desirable that the teeth of each ra- This is important to as possible. The level is as wide as possible. minimize machine losses, magnetization needs, etc.

With access to a conductor for the winding such as the cable mentioned above, there are great opportunities * to be able to optimize the magnetic core from the mentioned points of view. In the following, reference is made to a magnetic circuit in the stator of the rotary electric machine. Figure 2 shows an embodiment of an axial end view of a sector / pole division 6 of a machine according to the invention.

Rotor with rotor pole is denoted by 7. The stator is conventionally composed of a laminated core of electrical sheet successively composed of sector-shaped sheets. From a radially outermost ridge portion 8 of the core, a number of teeth 9 extend radially towards the rotor. Between the teeth there is a corresponding number of grooves 10. The use of cables 11 as above allows, among other things, that the depth of the grooves for high-voltage machines can be made larger than has been possible according to the state of the art. The groove has a tapered cross-section towards the rotor as the need for cable insulation is lower for each winding layer towards the rotor. As can be seen from the figure, the groove consists essentially of a circular cross-section 12 around each layer of the winding with narrower waist portions 13 between the layers. rightly referred to as a "bicycle chain track". Since in such a track cross-section a relatively large number of layers will be needed and the availability of current cable dimensions in terms of insulation and outer semiconductor is limited, it can in practice be difficult to achieve a desirable continuous phasing out of cable insulation and the stator groove, respectively. In the exemplary embodiment shown in Figure 2, cables with three different dimensions of cable insulation are used, arranged in three sections 14, 15 and 16 dimensioned accordingly, ie in practice there will be a modified cycle chain groove. The figure also shows that the stator teeth 9 can be designed with a practically constant radial width along the entire depth of the groove.

In an alternative embodiment, the cable used as winding may be a conventional power cable such as the one mentioned above. by peeling off the metal shield and sheath of the cable on the suitable grounding of the outer semiconducting layer 5 then takes place.

Within the scope of the invention, a large number of alternative embodiments are accommodated, depending on the available cable dimensions in terms of insulation and the outer semiconductor layer, etc. Also forms of expression. so-called bicycle chain tracks "can be nwdified in addition to what is described here.

As indicated above, the magnetic circuit may be located in the stator and / or rotor of the rotating electric machine. However, the design of the magnetic circuit will broadly correspond to the above description, regardless of whether the magnetic circuit is located in the stator and / or the rotor.

A winding is preferably used as a winding which can be described as a multilayer concentric cable winding. such a winding means that the number of intersections at the ends of the hairs has been minimized by all the hairs within the same group being placed radially outside each other. This also allows a simpler procedure in the manufacture and threading of the stator winding in the various grooves. Due to the fact that the cable used according to the invention is relatively easily bendable, the winding can be achieved by a relatively simple threading operation, in which the flexible cable is inserted into the openings 12 present in the grooves 10.

The known solution shown in Fig. 3 comprises a conventional generator. The latter because the conventional generator 20 generates voltage at relatively required to reduce low level. The transformer 21 the transmission losses, d Xr s to bring up the voltage to the required degree.

Between the transformer and the high-voltage switchgear is designated 22. both the generator and the transformer and between the switchgear are arranged switches 23 and 24, respectively. With 25 is designated a disconnector.

Conventional current and voltage transformers 26 and 27, respectively, are used in conventional manner. The generator 20 is coordinated with a magnetizing transformer 28 and a control unit 29 for magnetizing. An auxiliary power transformer is designated 30. This is connected to an auxiliary power switchgear 3l. ": there are conventional valve diverters serving L: ... J _, .L UVLLKJ rande: for surge protection. Grounds are designated 33. 10 15 20 25 520 775 23 In Fig. high voltage generator 34 equipped with one or more windings in accordance with the present invention is here so high voltage that it is able to be connected directly to the distribution or transmission network in question via the high voltage switchgear 35. the feeder according to the embodiment in Fig. 3 is completely omitted. This means that step-up transfer- A drastic simplification of the switchgear station results.

There are some additional differences. according to Fig. 3, the auxiliary power transformer is replaced by an auxiliary power winding on the generator 34. Otherwise, the notable difference is that a special protection device 36 has been added in the line between the generator and the high voltage switchgear 35. This protection device is intended to function overcurrently limiting. More specifically, this overcurrent limiting function takes place by the device in the event of a fault being detected in the formation of a low-impedance current path to earth. If the 21 according to the embodiment according to Eïg 3 is omitted, a possible fault, the transformer embodiment according to Fig. 4, for example in the isolation system of the generator 34, could give rise to the full power of the mains being loaded on the generator for at least some time before the circuit breaker . The overcurrent diverting device 36 is intended to operate significantly faster in order to divert the overcurrent and thus avoid it hitting the generator 34 in full. it in the event of faults causing According to executor currents limit these. preferably, said current limiting reactor is placed in line 37 between that generator 34 and the high voltage switchgear 35 so that the current limiting reactor is located between it. - ._ __..- fn fifi rmaf. -m fi wa a: 'ÅA 4 .. A vciotruinloavicdafïdc auc-Iuuiugcus .rutniïïg to lcoñiigc fi ie so that the reactor will fun- Lu O: 7 and the generator 34, make current limiting for current that tends to from the network 10 15 20 25 35 520 775 24 float in the direction of the generator in the event of a fault in it.

Fig. 5 illustrates in perspective a conventional switchgear station comprising two generators 38 which via high current rails 39 and a high current switchgear module 40 each supply their step-up transformer 41, which in turn are connected to the high voltage switchgear 42. Additional auxiliary equipment so - as auxiliary power transformers etc. are added. In addition, it is pointed out that the transformers 41, which are of conventional oil-filled design, require both fire separations in the form of walls, etc. and safety measures in the form. of oil capture plants. As can be seen, the station as a whole is extremely complex and expensive. It may be mentioned that the oil-insulated transformers 41 are placed outside the building 43 which contains the generators due to the great fire risk associated with oil-filled transformers.

Fig. 6 illustrates the practice of the invention, i.e. direct connection of high-voltage generators 44 directly on power grids without intermediate step-up transformers. As previously explained, the key to this possibility is the design of the generators' windings. In Fig. 6 it is indicated whether cables 45 running from the generators 44 go to the high-voltage switchgear 46. The networks and the network by means of a high-voltage cable reduce In addition, transformers etc. can be eliminated. The design according to Fig. 6 is significantly more environmentally friendly because the use of transformer oil can be completely avoided. The risk of fire is also significantly reduced. static In Fig. 7, a conventional (SVC) stand is normally illustrated by switching devices in the high-voltage switchgear design for VAR compensation together with switchgear. An SVC station is a transformer 48 which transforms the voltage down to a level that thyristors 49, 50 can handle, reactors. Most transmission applications require an automatic voltage (AVR). The disadvantage of the system is that there are many devices and they occupy capacitors and bidirectional thyristor valves, regulators such as thyristor control, with this large space.

Fig. 8 illustrates a station according to the invention with a rotating synchronous compensator and a high voltage switchgear 52. No transformer is needed between the synchronous compensator and the high voltage switchgear because the synchronous compensator 51 is designed to handle the current transmission voltage, which is a consequence of the winding of the synchronous compensator is performed by means of a cable according to the invention.

As can be seen from Fig. 8, the design becomes significantly simpler than that in Fig. 7 and it also requires less space. Fig. 9 illustrates a conventional switchgear station equipped with a static inverter in “back-to-back” design with DC link. station that the required area becomes large, which seems to be a significant disadvantage of this type of mainly due to the amount of filters. The transformers are complicated and specially designed for these plants.

Fig. 10 illustrates a diagram of a switchgear station having a rotary inverter 53. Each of these consists of a motor / generator provided with a winding in accordance with the description supplied above. The embodiment according to Fig. 10 is * particularly suitable when communication is to be established between two different networks with different parameters in some respect.

For example, the network 54 may be at a different voltage level, one or have a different number of different phase positions, a different frequency, phases than the other alternating voltage network 55. The illustrated interconnection of the networks by means of motors / generators where thus one unit 53 will operate the other solves the communication problem without causing any interference between the networks. As before, there are high-voltage switchgear 56 and various switches, etc. Here, too, it is more closely guided by the protection device described in Fig. 4 and more specifically in a dual edition under the designation 57 on either side of the motor / generator pair. Thus, the protection devices 57 will protect the pair of motor / generator from both networks 54, 55. In other respects, there are also components which have already been explained with the aid of previous figures.

From the above description it appears that the switchgear station according to the invention entails distinct advantages in addition to prior art in a variety of embodiments of rotating electric machines having magnetic circuits. The basic advantages of the invention have already been discussed above. As an additional factor, it must also be emphasized that it is a significant winding of the nose rail that will lead to a better environment in value that the inventive design of the vicinity of the switchgear station as a consequence of lower electric field especially at its cable connection. genetically and around the machine and in POSSIBLE MODIFICATIONS It is a given that the invention is not only limited to the embodiments described above. Thus, those skilled in the art will recognize that a variety of detailed modifications are possible once knowledge of the basic inventive concept has been obtained without departing from the spirit of the invention as defined in the appended claims. By way of example, it is pointed out that the invention is not limited to the specific material choices exemplified above. Functionally equivalent materials can thus be used instead. With regard to the manufacture of the insulation system according to the invention, it is pointed out that techniques other than extrusion and spraying are also possible as long as intimacy between the different layers is achieved. It is further pointed out that more equipotential layers could be arranged. For example, one or more equipotential layers of semiconductor material could be placed in the insulation between those referred to above as "inner" and "outer".

Claims (31)

10 15 20 25 30 35 520 775 28. Switchgear station, comprising at least one switchgear (35, 46, 52) and at least one rotating electrical machine for high voltage, which machine has at least one winding (1), which comprises at least one electrical conductor (2) and an insulation system comprising an insulation (4) formed of a solid insulation material, in that the insulation system inside the insulation comprises an inner layer (3) with an electrical conductivity which is lower than that of the electrical conductor but sufficient for the inner layer (3) to function as a potential equalizer and thereby equalizing with respect to the electric field outside the inner layer, that the insulation system outside the insulation comprises an outer layer (5), which has an electrical conductivity which is higher than that of the insulation so that the outer layer by connection to earth or otherwise relatively low potential must be able to function as a potential equalizer and to contain it mainly due to the said electrical conductors (2) emerging electric field inside the outer layer (5). Station according to claim 1, characterized in that said at least one conductor (2) constitutes at least one induction revolution. Station according to one of the preceding claims, characterized in that the inner and / or outer layer (3, 5) comprises a semiconducting material. Station according to any one of the preceding claims, characterized in that the inner layer (3) and / or the outer layer (5) has a resistivity in the range 106 Qcm - 100 kQcm, preferably 10'3-1000 Qcm, preferably 1-500 Qcm, in particular 10 - 200 Qcm. Station according to any one of the preceding claims, wherein the inner layer (3) and / or the outer layer (5) has a resistance which per meter of conductor / insulation system is within range 50 uQ- 5 MQ. Station according to one of the preceding claims, in that the solid insulation (4), the inner layer (3) and / or the outer layer (5) consist of polymeric materials. Station according to one of the preceding claims, characterized in that the inner layer (3) and / or the outer layer (5) and the solid insulation (4) are firmly connected to one another over substantially the entire interface in order to maintain the adhesion between the respective layers. and the solid insulation in the event of temperature changes and bending of the conductor and its insulation system. Station according to one of the preceding claims, characterized in that the inner layer (3), the outer layer (5) and the solid insulation (4) consist of materials with substantially equal coefficients of thermal expansion. Station according to one of the preceding claims, characterized in that the inner layer (3) and the outer layer (5) are produced by extrusion simultaneously with the extrusion of the solid insulation (4). Station according to one of the preceding claims, characterized in that the conductor (2) and its insulation system form a winding formed by means of a flexible cable (1). Station according to one of Claims 1 to 10, characterized in that the inner layer (3) is in electrical contact with the at least one electrical conductor (2). Station according to claim 11, wherein said at least one electrical conductor (2) comprises a number of strands and at least one strut of the electrical conductor (2) is at least partially uninsulated and arranged in electrical contact with the inner layer (3). Station according to one of the preceding claims, in that the inner and outer layers (3, 5) and the insulation (4) are made of material with such elasticity that the layers retain their adhesion to the solid insulation despite the temperature variations which occur during operation. . Station according to Claim 13, characterized in that the materials in the layers and the solid insulation have an E-modulus of less than 500 mPA, preferably less than 200 mPA. Station according to one of Claims 13 and 14, characterized in that the adhesion between the layers and the insulation is of at least the same order of magnitude as in the weakest of the materials. Station according to one of the preceding claims, characterized in that the conductor (2) and its insulation system are designed for high voltage, suitably above 10 kV, in particular above 36 kV and preferably above 72.5 kV. Station according to one of the preceding claims, in that the outer layer (5) is divided into a number of parts, each of which is connected to earth or otherwise has low potential. Station according to claim 1, characterized in that said at least one winding is arranged in the stator and / or rotor of the machine. Station according to one of Claims 1 and 18, characterized in that the magnetic field generating circuit comprises one or more magnetic cores (8) with grooves (10) for the winding (1). 10 15 20 25 30 35 520 775 ät Machine according to claims 18-19, in that with the outer layer (5) connected to earth potential, the electric field of the machine outside the outer layer is close to 0 both in the grooves (10) and in the reversal region. Station according to one of Claims 18 to 20, characterized in that the grooves (10) are formed as a number of axially and radially spaced cylindrical openings (12) separated by a narrower waist portion between the cylindrical openings. Station according to Claim 21, characterized in that the cross section of the openings of the grooves (10) decreases from a ridge portion (8) of the magnetic core. Station according to Claim 22, characterized in that the cross section of the grooves (10) decreases continuously or discontinuously. Station according to one of Claims 18 to 23, characterized in that the machine consists of a generator, motor or synchronous compensator. Station according to Claim 24, characterized in that the generator is of the hydrogen generator or turbogenerator type. Station according to one of Claims 1 to 25, characterized in that the machine is directly connected to an excessively strong voltage network, preferably 36 kV and above, without an intermediate transformer. Station according to claim 26, characterized in that the rotating electrical machine is connected to the switchgear via one or more flexible cables which form continuations of the winding in the machine. Station according to claims 24 and 26, 15. 520 775, i. . =. 39. by the fact that the machine is connected to a distribution or transmission network via the switchgear. Station according to any one of the preceding claims, in that the rotating electrical machine consists of a rotating synchronous converter or an asynchronous converter. Station according to one of the preceding claims, characterized in that an overcurrent diverting device (36) is connected to a line between the rotating electrical machine and the switchgear to divert any overcurrents to earth or otherwise lower potential in the event of a fault. Station according to one of the preceding claims, characterized in that a current-limiting reactor is connected to the line between the rotating electrical machine and the switchgear in order to limit these in the event of a fault.