EP0651400B1 - Leadthrough with special electrode supports in particular for high voltage - Google Patents

Abstract

The invention relates to a bushing (feedthrough) for connecting an electrical apparatus, which is insulated by gas, to a connection point (5) which is located in atmospheric air, has at least one field control electrode (23,33) (which is arranged coaxially about at least one bushing conductor) at that end of the bushing conductor which faces the region of the bushing carrying potential, and has an insulating tube (25,35) which is assigned to each field control electrode and is arranged coaxially with respect to the bushing conductor. The bushing is distinguished by the fact that the one or more field control electrodes (23,33) are designed as tubes and the one or more insulating tubes (25,35) are connected to that end of the associated control electrode which is on the earth potential side, and are connected to this control electrode via a conductive clamping-in element (24,34). <IMAGE>

Description

The invention relates to a bushing, in particular for high voltages, for connecting a gas-insulated electrical device with a connection point lying in atmospheric air, with a union insulator, with at least one field control electrode arranged coaxially around at least one bushing conductor on the bushing carrying the potential-carrying area (on the potential side ) facing end of the feed-through conductor, and an insulating tube assigned to each field control electrode and arranged coaxially to the feed-through conductor for holding the field control electrode.

Such an implementation is known for example from DE 42 40 118. The at least one field control electrode is formed by conductive sections on at least one insulating tube on an end facing the potential-carrying area of the bushing, the at least one insulating tube being arranged coaxially around at least one bushing conductor and by a holder on its earth potential-side end outside the one with a high field strength loaded area is held on one side.

With this implementation, operational reliability is increased, in particular increased, compared to other known implementations Dielectric strength achieved even with smaller dimensions.

However, in the case of control electrodes which are formed by a very thin metallic coating on insulating tubes, there is a risk of mechanical injuries to this sensitive layer through "handling" (assembly, etc.); Also, small gas gaps in the boundary layer between the insulating tube and the electrically conductive layer cannot be completely ruled out. There, due to the different dielectrics of the enclosed gas and the insulating tube, they can lead to increased electrical field strengths which cause partial discharges and, in extreme cases, mechanical damage to the conductive layer. Such damage to the conductive layer can, however, be the starting point for electrical breakdowns between the field control electrode and the adjacent high-voltage electrode.

The invention was therefore based on the object of further improving the electrical strength of the implementation mentioned at the outset while maintaining the advantages already achieved.

This object is achieved with the above-mentioned implementation in that the at least one field control electrode is designed as a tube and the associated insulating tube connects to the end of the field control electrode facing away from the electrical device and is connected to the latter via a preferably conductive clamping element.

By means of this clamping element, which fixes both the end region of the field control electrode and the start region of the insulating tube, it is possible, in cooperation with the insulating tube, for the To clamp the field control electrode concentrically with respect to the feed-through conductor at a particularly low cost. This in turn is a reason for increasing the dielectric strength of the bushing according to the invention, since deviations from the ideally concentric position can lead to a one-sided shortening of the insulation distance and thus to flashovers.

Another advantage results from a precise joining of the clamping element and the field control electrode (tube) with an exact fit at the joint between these parts, so that the coaxial cylinder field between the lead-through conductor and the field control electrode remains largely unaffected by the joint.

Since the field control electrode in the form of a tube is also considerably less sensitive, the dielectric strength of the overall arrangement is further increased by this design.

An advantageous embodiment of the invention consists in producing the clamping element and the field control electrode preferably from aluminum; other materials are also possible.

The clamping element can also be designed as a bead-shaped termination of the field control electrode. As a result, the clamping element has a multiple function. On the one hand, it serves for the mechanical connection of the field control electrode to the insulating tube and for the concentric fixing of the field control electrode; on the other hand, due to its bead-like design, the field profile at the end of the field control electrode is influenced favorably and in the desired manner.

The diameter of the insulating tube is preferably larger than the diameter of the associated field control electrode. In this case, the insulating tube can overlap an end region of the field control electrode. Furthermore, the clamping element can have an inner electrode ring lying between the insulating tube and the field control electrode, and an outer electrode ring which clamps the end region of the insulating tube from the outside and clamps. For this purpose, the outer electrode ring has a preferably slotted outer clamping ring.

The at least one insulating tube is held by at least one insulating disk arranged in the region of its end facing the connection point.

The insulating washers can be attached coaxially to a support tube surrounding the lead-through conductor or conductors.

The bushing preferably has a first, outer and a second inner field control electrode arranged coaxially thereto, each with a first outer and a second inner insulating tube.

The end of the second field control electrode facing the electrical device can be displaced relative to the same end of the first field control electrode in the direction of the connection point of the bushing. Furthermore, the end of the second inner insulating tube facing the connection point can lie within the first insulating tube. Alternatively, the first and the second insulating tube can also have a common end on the connection point side.

The insulating washers can each have a conical fastening ring resting on the support tube Be fixed in the axial direction, wherein the ring engages in a recess of the respective insulating washer.

The field control electrodes are preferably bulged at their ends to avoid impermissibly high field strength peaks. Furthermore, the gas contained in the bushing can be under increased pressure.

The implementation according to the invention can finally be used in current, voltage or combination converters.

Further details, features and advantages of the invention result from the following description of exemplary embodiments with reference to the drawings.

Fig. 1

eine erste Ausführungsform der erfindungsgemäßen Durchführung in einer teilweise angeschnittenen Gehäuseansicht eines Stromwandlers mit einer Feldsteuerelektrode;

Fig. 2

eine zweite Ausführungsform der erfindungsgemäßen Durchführung in einer teilweise angeschnittenen Gehäuseansicht eines Stromwandlers mit zwei Feldsteuerelektroden;

Fig. 3

eine Darstellung des unteren Abschnitts einer dritten Ausführungsform der Erfindung;

Fig. 4

eine vierte Ausführungsform der erfindungsgemäßen Durchführung als Spannungswandler und

Fig. 5a und 5b

eine Detaildarstellung zweier erfindungsgemäßer Ausführungsformen des Einspannelementes.

Show it:

Fig. 1

a first embodiment of the implementation according to the invention in a partially cut housing view of a current transformer with a field control electrode;

Fig. 2

a second embodiment of the implementation according to the invention in a partially cut housing view of a current transformer with two field control electrodes;

Fig. 3

an illustration of the lower portion of a third embodiment of the invention;

Fig. 4

a fourth embodiment of the implementation according to the invention as a voltage converter and

5a and 5b

a detailed view of two embodiments of the clamping element according to the invention.

Figure 1 shows a transducer 1, the upper housing head 2 with cover 3 is designed as a cast aluminum housing and which has the potential of a current conductor 4 during operation. The current conductor 4 is enclosed in the interior of the housing head 2 by the core of the transducer 1 with a core shield 11. From the coil of the transducer 1, a current-carrying connection is created by means of the bushing according to the invention to an external location lying in atmospheric air, ie to a junction box 5 which is mounted on a base 9 lying at earth potential. The potential difference between the housing head 2 and the base 9 lying at earth potential is bridged by a coupling insulator 6, which together with the housing head 2, the housing cover 3 and the base 9 forms a gas-tight space, which is preferably filled with sulfur hexafluoride (SF ₆ ) as the insulating gas is and can also be under pressure to increase the insulation effect. The lead-through lead (s) is / are surrounded by a support tube 7.

The housing head 2 is continued down into the region of the union insulator 6 with a high-voltage electrode 20 which has a bead-shaped end 22. A first field control electrode 23 is arranged coaxially with the high-voltage electrode 20 as well as the support tube 7 and the union insulator 6, the upper end 21 of which is formed in a bead shape in order to avoid local increases in field strength.

The first field control electrode 23 represents an aluminum tube, the lower end of which is formed by a first clamping element 24. This clamping element also ensures that the field control electrode 23 is mounted concentrically with the support tube 7 and the union insulator 6 with great accuracy.

A first insulating tube 25 connects to the lower (earth potential-side) end of the first field control electrode 23. This insulating tube preferably has a slightly larger diameter than the first field control electrode 23 and overlaps it in a transition region. The diameter of the insulating tube 25 can, however, also be smaller or the same size as that of the field control electrode 23. These two parts can be connected to one another both overlapping and abutting or abutting or flange-like. As is clear from FIG. 1 (and in detail from FIG. 5), the upper end of the insulating tube 25 is fixed to the field control electrode 23 via the clamping element 24. The insulating tube 25 is also held on the support tube 7 by means of two first insulating washers 14, 14 ′ in the region of its end on the earth potential side. The distance between the two first insulating disks 14, 14 ', which are firmly connected to the insulating tube 25, results in a mechanically large clamping length, which results in a correspondingly robust mounting of this tube. The insulating washers are axially fixed on the support tube 7 by conical fastening rings 12 which engage in corresponding recesses in the insulating washers.

The support tube 7 is fixed on the earth potential side to the base 9 with a fastening part 8. Openings 15 are provided in the first insulating washers 14, 14 ' allow easier drying and impregnation of the space between the insulating washers.

Figure 2 shows a second embodiment of the invention. In contrast to FIG. 1, the feedthrough according to FIG. 2 additionally has a second inner field control electrode 33, the upper end 31 of which is displaced relative to the upper end 21 of the first field control electrode 23 in the direction of the earth potential side, that is to say it lies within the first field control electrode 23. The lower end of this second field control electrode 33 is closed with a second clamping element 34. Like the first clamping element, this second clamping element 34 also serves to fasten the upper end of a second insulating tube 35, which connects to the second field control electrode 33 in the direction of the earth potential-side end of the bushing. The second field control electrode 33 is also designed as an aluminum tube. In this embodiment, the second insulating tube 35 ends within the first insulating tube 25, so it is considerably shorter than this. Second insulating washers 16, 16 'in the region of the end of the second insulating tube 35 on the earth potential side serve in a similar manner, as shown in FIG. 1, for coaxially fastening the second insulating tube to the support tube 7. The second insulating washers 16, 16' are on the support tube 7 in axial direction also defined by conical fastening rings 12 which engage in corresponding recesses in the second insulating washers.

In the third embodiment of the invention shown in FIG. 3, in contrast to the second embodiment, the inner, second insulating tube 35 extends in the axial direction up to the lower end of the first insulating tube 25. In this case, the first insulating washers 14, 14 'serve as common holders for both insulating tubes, the conical fastening rings 12 in turn serving to axially fix the insulating washers.

Of course, further field control electrodes, each with an associated insulating tube, can also be provided. By increasing the number of field control electrodes, the diameter and the length of the coupling insulator, which is preferably made of glass fiber reinforced plastic, can be further reduced, or bushings for higher voltage ranges can be realized with the same dimensions.

Figure 4 shows a fourth embodiment of the invention. It is a voltage converter, while current transformers are shown in FIGS. 1 to 3. In this embodiment, too, a support tube 7 is provided, which contains one or more lead-through conductors. The housing head 2 is at ground potential, while the support tube 7 and connection plate 36 are live in this implementation. Correspondingly, a ground potential electrode 40 with a bead-shaped end 42 connects to the housing head. The first field control electrode 23, to which the first insulating tube 25 is connected, is provided at the end of the support tube 7 facing the earth potential-side region of the bushing. These two parts are each arranged coaxially to the support tube 7 and the union insulator 6. In this embodiment too, the diameter of the insulating tube 25 is slightly larger than the diameter of the field control electrode 23. However, as already described above, other diameter ratios are also possible here. In the transition area between these two parts there is again a Clamping element 24, which has the same functions as in the embodiments of FIGS. 1, 2 and 3.

The structure also essentially corresponds to that shown in FIG. 1, the end of this bushing on the high-voltage potential being terminated with an end plate 36.

In this embodiment too, a plurality of field control electrodes arranged coaxially to one another can be provided, each of which is connected to an insulating tube.

FIGS. 5a and 5b finally show detailed representations of the clamping element 24, 34 in the transition area between the field control electrode and the insulating tube. It is particularly clear from this illustration that the clamping element essentially consists of an inner electrode ring 242 and an outer electrode ring 241. The inner electrode ring 242 lies between a field control electrode 23, 33 and the associated insulating tube 25, 35, while the outer electrode ring 241 surrounds the insulating tube 25, 35 from the outside. The clamping element 24, 34 is used both for mechanical mounting and coaxial fixing of the field control electrode 23, 33 with respect to the support tube 7 by means of the insulating tube 25, 35 fastened coaxially to the support tube with insulating disks, and also as an electrical termination of the field control electrode with which to avoid field strength peaks and voltage flashovers a desired field profile is achieved. For this purpose, the radii of both the inner and the outer electrode ring are selected in a suitable manner.

The reference number 37 designates the joint between the field control electrode 23, 33 and the inner electrode ring 242.

The outer electrode ring 241 can furthermore be formed in two parts, an outer, preferably slotted clamping ring serving to improve the mechanical fixation.

In contrast to FIG. 5a, the end of the inner and outer electrode ring facing away from the field control electrode is recessed or hollowed out in the area adjacent to the insulating tube in FIG. 5b.

The illustrated embodiments of the invention are particularly suitable for voltage ranges between approximately 250 and 400 kV.

Reference list

1

Transducer

2nd

Housing head

3rd

Housing cover

4th

Conductor

5

Junction box

6

Union insulator

7

Support tube

8th

Fastener

9

base

11

Core shielding

12th

Mounting ring

14.14 '

first insulating washers

15

opening

16.16 '

second insulating washers

20th

High voltage electrode

21

potential-side end of the first field control electrode

22

End of the high voltage electrode

23

first field control electrode

24th

first clamping element

25th

first insulating tube

31

potential-side end of the second field control electrode

33

second field control electrode

34

second clamping element

35

second insulating tube

36

Connection plate

37

Joint

241

outer electrode ring

242

inner electrode ring

40

Earth potential electrode

42

End of the earth potential electrode

Claims (18)

1. Bushing for connecting a gas-insulated electric appliance to a connecting point situated in atmospheric air, having a cap insulator, having at least one field-control electrode (23, 33) disposed coaxially around at least one bushing conductor at the end of the bushing conductor directed towards the electric appliance, as well as one insulating conduit (25, 35) associated with each field-control electrode (23, 33) and disposed coaxially relative to the bushing conductor for holding the field-control electrode, characterized in that the at least one field-control electrode (23, 33) takes the form of a tube and the associated insulating conduit (25, 35) adjoins the end of the field-control electrode (23, 33) remote from the electric appliance and is connected by a preferably conductive clamping element (24, 34) to the field-control electrode.
2. Bushing according to claim 1, characterized in that the at least one field-control electrode (23, 33) and the at least one clamping element (24, 34) are made of aluminium.
3. Bushing according to claim 1 or 2, characterized in that the at least one clamping element (24, 34) forms a bead-shaped termination of the field-control electrode (23, 33).
4. Bushing according to one of the preceding claims, characterized in that it is filled with gas, preferably sulphur hexafluoride (SF₆) .
5. Bushing according to one of the preceding claims, characterized in that the diameter of the at least one insulating conduit (25, 35) is greater than the diameter of the associated field-control electrode (23, 33).
6. Bushing according to one of the preceding claims, characterized in that the insulating conduit (25, 35) overlaps an end region of the associated field-control electrode (23, 33).
7. Bushing according to one of the preceding claims, characterized in that the clamping element (24, 34) comprises an outer electrode ring (241) and an inner electrode ring (242), the inner electrode ring (242) lying between the field-control electrode (23, 33) and the insulating conduit (25, 35) and the outer electrode ring (241) embracing the insulating conduit (25, 35).
8. Bushing according to claim 7, characterized in that the outer electrode ring (241) comprises a preferably slit, outer clamping ring.
9. Bushing according to one of the preceding claims, characterized in that the at least one insulating conduit (25, 35) is held by at least one insulating disc (14, 14'; 16, 16') in the region of the end of the insulating conduit (25, 35) directed towards the connecting point.
10. Bushing according to claim 9, characterized in that the insulating discs (14, 14'; 16, 16') are fastened coaxially to the carrying tube (7) surrounding the at least one bushing conductor.
11. Bushing according to one of the preceding claims, characterized by a first, outer field-control electrode (23) and a second, inner field-control electrode (33) arranged coaxially therewith, having in each case a first outer insulating conduit (25) and a second inner insulating conduit (35).
12. Bushing according to claim 11, characterized in that the end (31) of the second field-control electrode (33) directed towards the electric appliance is disposed offset, relative to the corresponding end (21) of the first field-control electrode (23), in the direction of the connecting point of the bushing.
13. Bushing according to claim 12, characterized in that the end of the second, inner insulating conduit (35) directed towards the connecting point is offset, relative to the end of the first insulating conduit (25), in the direction of the end of the bushing directed towards the electric appliance.
14. Bushing according to claim 11 or 12, characterized in that the first (25) and second insulating conduit (35) have a common end directed towards the connecting point.
15. Bushing according to one of claims 9 to 14, characterized in that the insulating discs (14, 14'; 16, 16') are fixed in an axial direction by means of, in each case, one conical fastening ring (12) fastened to the carrying tube (7), each fastening ring (12) engaging into, in each case, one recess of an insulating disc (14, 14'; 16, 16').
16. Bushing according to one of the preceding claims, characterized in that it is filled with gas, which is under increased pressure.
17. Current or combined instrument transformer having a bushing according to one of the preceding claims, characterized in that the field-control electrode (23, 33) lies at the high-voltage potential-side end of the at least one bushing conductor and the associated insulating conduit (25, 35) adjoins the end of the field-control electrode (23, 33) directed towards the earth potential-carrying region of the bushing.
18. Voltage transformer having a bushing according to one of claims 1 to 16, characterized in that the field-control electrode (23, 33) lies at the earth potential-side end of the at least one bushing conductor and the associated insulating conduit (25, 35) adjoins the end of the field-control electrode (23, 33) directed towards the potential-carrying region of the bushing.

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