DE2327629A1 - FEED-THROUGH INSULATOR FOR HIGH VOLTAGE DEVICES AND METHODS FOR ITS MANUFACTURING - Google Patents

Description

Bushing insulator for high voltage facilities and its method of manufacture

The invention relates to a method of manufacture a bushing insulator for high-voltage equipment with an insulation body with capacitor inserts is provided, one end of which is at least in a liquid Medium is arranged and forms a potential transition zone.

Electrical devices with high operating voltages of, for example, 200 kV are often liquid or gaseous Surrounding media - cooling the high-voltage parts or improving the high-voltage resistance of the institutions are supposed to bring about. The medium must come from the outside of the electrical device, for example a high voltage cable or a transformer. It must therefore be isolated in a sufficiently long manner Route through a potential gradient before it can reach the high-voltage parts. Rollover in the medium can then be prevented.

Pure oil-cooled power supplies are therefore appropriate Hollow cylindrical high-voltage bushings with insulation bodies have been developed to reduce stress in the Effect oil without breakdowns or spray discharges can occur in the medium. A bushing insulator known from German patent specification 853 027 has in inside a cylindrical bolt. This tubular bolt consists of a material with good electrical conductivity, for example copper, and represents the high-voltage lead It also serves as a mechanical support body for the concentrically attached to its outer wall.

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brought high-voltage insulation bodies. This insulation body, which can for example be a hard paper roll, is provided with concentrically arranged, controlling foil inserts, so-called capacitor inserts. The cylindrical one The winding is turned out conically on the lower part of the insulation body in the oil part so that the edges of the foil inlays open a conical surface, so lie under oil. The capacitor inserts thus effect the conical on the outer surface Turning out a continuous tension transition in the Oil from the earth potential of a flange on the outer jacket of the insulation body to the metallic bolt on high voltage.

Potential gradients also occur in high-voltage bushings in cryogenic media such as nitrogen, hydrogen and helium of, for example, 40 kV and more. To build up or reduce tension, there is the option of oil feedthroughs known measure, by means of capacitor inserts a potential transition zone on a bushing insulator in the cryogenic medium, especially the dielectric strengths for liquid helium and oil, for example are approximately the same.

Bushing insulators are required, for example, for superconducting cables, coils or machines during their operation the superconductors at a temperature below the jump. temperature of the superconducting material can be maintained have to. The coolant in these electrical devices must be in close contact with the live ones There are ladders that are under high voltage. It must do this at one point. for example on a cable termination, from the earth potential of the cooling equipment, for example a helium liquefaction plant, to the high voltage of the live conductor.

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However, it has been recognized that the known bushing insulator with epoxy resin insulation body cannot be used for this purpose because of the strong Temperature gradient between room and superconducting temperature in it mechanical stresses can occur, which too Lead cracks in its insulation body. These mechanical stresses occur because the support body f used metal inner tube, which is also called electrical Conductor is used, "when cooling to 4.2 K, for example 5 to 10 times less than the epoxy resin Has contraction and thus tearing the outer Epoxy resin body leads.

The object of the invention is therefore to provide the known bushing insulator for electrical equipment, especially its use at cryogenic temperatures to enable. The invention is based on the consideration that the essential design features of the known Bushing insulator are also suitable for cryogenic media if the metallic support body is not available.

The stated object is thus achieved according to the invention solved that the support body formed with a self-supporting Insulation body is provided and then removed again. The advantages achieved with the invention are in particular that mechanical stresses in the insulation body can largely be avoided, especially if the expansion coefficient of the capacitor inserts corresponds to the expansion coefficient of the Insulation material matches. It can thus with the Cooling of the insulation body no cavities arise, and Partial discharges, which can lead to the destruction of the entire insulation body, are avoided. The isolator is therefore also suitable for high voltages. ■

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To further explain the invention, reference is made to the drawing, in which, in FIG. 1, one half of a bushing insulator for electrical high-voltage devices according to the invention in longitudinal section schematically illustrated is. Fig. 2 shows as an application example an end closure with power and coolant supply of a superconducting Three-phase phase with a bushing insulator according to the invention.

In Fig. 1 one half of a hollow cylindrical bushing insulator according to the invention is shown, the
at least with its conical end in one
Cryogenic medium, "for example in liquid helium. It contains epoxy resin, for example, or something impregnated with epoxy resin under vacuum as insulation material
Special paper and can be used for high voltage bushings
for example 200 kV at 50 Hz can be provided. In his
Insulation body £ are capacitor inserts 3 Ms 15 arranged concentrically to the axis A of the hollow cylindrical body 2_, as indicated by dashed lines parallel to the axis in the figure. The capacitor inserts and that
The insulation material of the insulation body 2_ advantageously have approximately the same expansion coefficient. Mechanical stresses then occur in the insulation body when it cools down
does not respond to cryogenic temperatures. The capacitor inserts are advantageously arranged stepped to one another at one end in such a way that there is an approximately linear potential gradient along the beveled side 16 of the insulating body 2_ from the inside to the outside in the cryogenic medium surrounding them
can form when the innermost control insert 3 is placed, for example, on high voltage potential and the outermost
Control insert 15 is connected to the ground potential. For this purpose, the control insert 15 is provided with an electrical connection 17 and the control insert 3, for example, with one
metallic flange part 18 at the end of the insulation body 2 / connected.

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The approximately linear potential characteristic of the insulator on its beveled side 16 can be described in a known manner Way by a suitable choice of the radial distances between the individual capacitor inserts 3 to 15 and achieve their length..In the figure they are therefore with reproduced in different lengths.

Such bushing insulators for high-voltage devices can, for example, be manufactured in such a way that one • a mechanically stable core as a carrier body, for example a metal pipe, with the insulation material, for example with individual layers of a special paper, concentrically encased, between the individual "layers of paper Introduces capacitor foils one after the other, and then soak the resulting winding with a plastic, for example epoxy resin, under vacuum. Uach solidification of the insulation material can then be the core, which is only used as a support body for the insulation material with the capacitor control inserts served, removed, for example drilled out, so that the insulator now only consists of the self-supporting, mechanically stable insulation body with the control inserts drawn into it.

The insulation body can also consist of self-amalgamating polyethylene tapes, between which the individual Capacitor inserts are arranged.

Of course, the bevel of side 16 of the isolator is provided on the side facing the axis if in an arrangement with such an isolator on this side a potential transition in a cryogenic Medium is required. Pig. 1 Corresponding isolators can be used wherever in a cryogenic · Medium, such as helium, a large potential gradient must be overcome. This applies, for example, to coolant feeds for cryogenic cables, in particular superconducting high voltage cables, for superconducting magnets

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- 6 or machines with superconducting windings.

In Fig. 2 is a vertically arranged end closure of a preferably superconducting phase conductor 21 of a three-phase

■ kabeis with a bushing insulator for high voltage equipment shown according to the invention. The isolator is denoted by 20. The termination is from one vakuumdichtη hollow cylinder 22 surrounded. The phase conductor 21 contains a hollow cylindrical inner conductor 23 at high voltage potential, which is enclosed concentrically by an outer conductor 24 at ground potential. The ladder are for example made up of a large number of superconducting individual wires. The inner conductor 23 is at its upper one End with a disc-shaped contact plate 25. » whose Diameter is greater than the diameter of the inner conductor, · contacted. This is on the outer edge of this contact plate 25 lower end of a tubular inner normal conductor 26 electrically connected. Around this inner normal conductor is insulated at a predetermined distance from the inner normal conductor 26 corresponding outer conductor 27 concentrically

• arranged. The lower end of the tubular outer normal conductor 27 is attached to the inside of a concentric, annular contact plate 28 in an electrically conductive manner. With the outer edge of this contact plate 28 is the upper, concentrically outwardly widened end of the outer conductor 24 electrically connected. The contact plate 28 surrounds the inner contact plate 25 in an annular manner. About the Contact plates 25, 28 are accordingly fed to conductors 23, 24 with the current supplied via E normal conductors 26, 27. The parts 23, 25 »26 are at high voltage potential, the parts 24, 28, 27 surrounding them are at ground potential. That from the cold end 2_9_ of the power supply, which is formed in one plane and is arranged in one plane, represents the cover of a hollow cylindrical vessel 30 for a cooling medium A. A tubular one Hollow body, which represents the outer wall 31 of the vessel 3j0, is stepped downwards and narrowing.

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forms. Between him with the connecting phase conductor 21 and the vacuum-tight hollow cylinder surrounding it 22 is a radiation shield 32, for example is cooled with nitrogen, indicated. The inner wall of the vessel J30 is formed by an insulating body 33, which concentrically surrounds the inner conductor 23, but that The upper end of the inner conductor 23 leaves free. Through the annular gap between the contact plate 25 and the end of the insulation body 33, the cooling medium A reaches the interior of the coolant-transparent inner conductor 23. The insulation body 33 is surrounded by a high-voltage winding 34, the to control the potential transition in the cooling medium A with capacitor inserts corresponding to the insulator 20 according to FIG Invention can be provided.

In the vessel 3 (3 there is arranged a container 35 of approximately the same design for a further cooling medium B. Its outer wall 36 is fastened in a gas-tight manner to the outer contact plate 28, and its inner wall 37 to the inner contact plate 25. The container 3j5 is like this. arranged in the vessel 30 so that between the walls 36 and 31 and the walls 37 and 34 or 33 there is a sufficient space for guiding the cooling medium A. The lower part 39 of the hollow cylindrical insulator 20 according to FIG Invention. This insulator 20 is arranged in the upper part of the end seal between the inner and outer normal conductors 26 and 27 and between the two contact plates 25 and 28 in such a way that exhaust gas produced in the container 35 is parallel to both of its sides along the normal conductors 26, 27. The lower part 39 of the insulator 20, which is located in the container 35, has on its inside an inwardly drawn potential control according to FIG Representation in Fig. T. This potential control advantageously has an approximately linear characteristic.

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The supply and discharge of the cooling medium for the entire cable or part of the cable takes place in the cable termination. When using superconducting conductors 23 and 24, the only suitable cooling medium is practically only helium. in the Cable termination two separate helium baths are available: Boiling helium B, which the tank _55. fills in, is used for Absorption of power supply losses. Furthermore, single-phase helium A and G are used in closed circuits and under pressure to dissipate the losses of the phase inner conductor

23 or phase outer conductor 24.

The supply of the boiling helium B and the control of the helium level can advantageously be carried out at ground potential. The voltage transition from earth to high voltage potential in helium B takes place evenly via a corresponding large distance by means of the potential-controlled lower part 39 of the retracted insulator 20 according to the invention its advantageous, approximately linear potential characteristic. Due to pressure differences in the inner and outer gas space Vibrations of the helium B caused on both sides of the insulator 20 can advantageously be carried out by a fine-pored filter 40 are damped between the lower end of the lower part 39 of the insulator 20 and the Bottom of the container _3J? is arranged.

The outer and inner conductors 23 or

24 of phase 21 designed to be helium-permeable, so that the helium supply to the cooling circuits takes place at ground potential can. The distribution of the helium flow A, C for the internal and external cooling of the phase conductor 21 takes place for example via a three-way valve 41 which is at the helium inlet temperature. The helium A for cooling the inside of the conductor is on when flowing through the space between the winding 34 around the insulation body 33 and the wall 37 Brought high voltage potential, i.e. the build-up of voltage

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takes place between the inner and outer conductor in the end seal via the winding 34, which can advantageously be provided with capacitor inserts. TJm is the dielectric strength of / Cooling medium A not to deteriorate, it must Flow velocity be relatively low. This is made possible by a correspondingly large distance between the Wrap 34 and the wall 37 reached. The helium supply for cooling the outer conductor 24 and the outer conductor 24 are passed through the helium bath A for the inner conductor 23.

In this embodiment, the insulator 20, 39 is an end closure freely insertable. At its upper end it is at room temperature against the helium gas from the container 35 sealed and fixed so that there is no difficulty .. in the thermal contraction of its low-temperature part 39 there.

9 claims
2 figures

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Claims (9)

7PA 7 3/756 !? - 10 - Claims Method of manufacturing a bushing insulator "for high-voltage equipment with an insulation body which is provided with capacitor inserts, one end of which is arranged at least in a liquid medium and forms a potential transition zone, characterized in that da3 a carrier body is provided with the self-supporting insulating body (2_) and then again Will get removed. 2. A method for producing a bushing insulator for high-voltage devices with an insulation body which is provided with capacitor inserts, one end of which is arranged at least in a liquid medium and forms a potential transition zone, characterized in that a carrier body, the material of which has approximately the same coefficient of expansion as the material of the insulating body (2) , provided with the insulating body (2_) and then at least partially removed again. 3. The method according to claim 1 or 2, c & characterized by that the insulation body (2_) made of a cast resin and / or a self-curing plastic is made. 4. The method according to claim 2, characterized in that let the carrier body alternately with a layer of a self-amalgamating polyethylene tape and a Capacitor insert (3 to 15) is provided. 5. The method according to claim 3, characterized in that a thermoplastic is used. 6. The method according to claim 1 or 2, characterized in that the carrier body alternately with a layer AO9850 / 0651 2327623 TPA 73/7565 - 11 - Special paper and a capacitor insert (3 "to 15) is provided and that then the resulting lap is impregnated under vacuum with a casting resin and / or a plastic. 7. bushing insulator according to one of claims 1 to 6, characterized in that the insulating body (2) is self-supporting is formed and that its end provided with the potential transition zone (16) is in a cryogenic medium is arranged. . 8. bushing insulator according to claim 7, characterized in that that the potential transition zone (16) a has approximately linear potential characteristics. 9. Bushing insulator according to one of claims 1 to 8, characterized in that the expansion coefficient the material of the insulation body - (2?) and the material of the capacitor inserts (3 to 15) at least approximately are the same. AO9 850/06 53