JP2016208022A - Gas insulating surge arrester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surge arrester which can be manufactured cost-effectively and can be easily assembled.SOLUTION: A surge arrester (1) of the present invention has at least one active part (2) arranged in a fluid tight casing (3). The casing (3) have a side surface (4) and a bottom portion (5). The end portion facing the bottom portion (5) is closed by a lid (6). The side surface (4) and the bottom portion (5) are integrated. The bottom part (5) has one opening (7) for each active part (2), the one active part (2) can be introduced through the opening (7). Each opening (7) is fluid tightly closed by a closing lid (8).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a gas-insulated surge arrester.

Surge arresters are protection systems, for example for high-voltage or intermediate-voltage switchgear, which protect the overvoltage from grounding when an overvoltage occurs due to a lightning or other partial system malfunction. The other parts in the switchgear are protected by flowing.
This type of surge arrester includes one or more active parts having a plurality of cylindrical arrester elements, each of these arrester elements also being constituted by a plurality of cylindrical varistor elements. And the varistor stack extends along the cylindrical axis. A characteristic of the varistor element is a resistance depending on voltage. These function as insulators at low voltages. Beyond certain voltage thresholds determined by the material, they exhibit good conductivity. The varistor element is generally made of a metal oxide such as zinc oxide. Both ends of the arrester element are in contact with the end mounting base, and these end parts are electrically connected to the switchgear and the ground. In order to ensure good electrical contact even under mechanical loads, the varistor stack must be held under pressure. This can be achieved, for example, by securing a plurality of restraining elements, such as resin ropes or rods, in particular reinforced with glass fiber, to both end mounts under tension. In that case, the restraining elements form a cage around the varistor stack by surrounding the varistor stack.

For use in a gas insulated switchgear, the surge arrester has a fluid tight casing that surrounds the arrester element. In this case, the casing is filled with a fluid, usually sulfur hexafluoride (SF ₆ ), in order to increase the dielectric breakdown strength. This casing is usually made of metal and is electrically grounded. One end mount of the surge arrester stack is grounded via a contact that is led through its casing. The other end mounting base is electrically connected to a high-voltage contact outside the casing via one casing bushing, and connection to the switchgear is performed by this contact.

  The subject of the present invention is a surge arrester for a gas insulated switchgear.

  This type of surge arrester having a gas insulating casing having three active parts is known (see, for example, Patent Document 1). This casing is composed of one cast cylindrical side surface portion, one high voltage side lid having one high voltage bushing for each active portion, and one ground side lid. This earth side lid has a large number of openings and mounting members, which are cumbersome and expensive to manufacture. Furthermore, since all the active parts must be attached to the lid, the assembly of the surge arrester is troublesome. Thereafter, the lid is attached to the side of the casing along with a plurality of active parts attached thereto. At that time, the plurality of active portions must be respectively inserted into corresponding holding portions provided on the high-voltage side lid, which is troublesome.

European Patent Application Publication No. 2846333

  An object of the present invention is to provide a surge arrester whose manufacture is cost-effective and can be easily assembled.

  According to the present invention, a surge arrester having at least one active part arranged in a fluid tight casing such as used in a gas insulated switchgear is provided for the above purpose. As is well known in the case of surge arresters, the active part is a stack of voltage-dependent resistance groups, so-called varistor groups, which are fixed between two end mounts. . The present invention relates to a surge arrester having one or more active parts. However, a special advantage is provided in a configuration with three active parts. The casing has a side wall and a bottom portion, and an end portion facing the bottom portion is closed with a lid. The side walls and the bottom are integrally formed and are cast, for example, in a unitary structure, for example made of aluminum or steel. The bottom has one dedicated opening for each active part, through which one active part can be introduced into the casing. To that end, the shape and inner edge of the opening must be designed so that one complete assembled active part can be introduced into the casing through the opening. Each opening is fluid tightly closed by one closing lid. Preferably, the surge arrester has a plurality, in particular three active parts. The bottom is provided with one opening for each active part, so in the case of three active parts, the bottom has three openings.

  Such casings can often be produced at low cost, for example by abandoning the bottom that can only be made by machining, and thus casting the bottom together with the side walls into a single structure. Furthermore, such a surge arrester can be easily assembled. This is because a plurality of active parts can be assembled by individually introducing them through the opening instead of collectively.

  In an advantageous embodiment of the invention, each opening passes through a flange, which is arranged outside the bottom, in particular cast into a single structure. The flange surrounds the opening in a plane perpendicular to the longitudinal axis. The flange is used to attach a closure lid, thereby making it easy to assemble. In particular, the flange is warped outward, thereby allowing easy access to the flange.

  In particular, the outer diameter of the casing tapers toward the bottom and increases toward the lid. Thereby, the inner diameter of the casing is adapted to the insulation distance that increases towards the lid over the height of the casing, thus reducing the volume of the casing. This saves on the one hand material for the casing and on the other hand saves the insulating fluid for filling.

  It is likewise advantageous if the closing lid and the opening cross section are square, in particular square. In the alternative, these are circular. Both embodiments allow a particularly simple production of the closure lid and thus also a cost-effective production.

  In another advantageous embodiment, each active part is attached to one closing lid, which allows simple manufacture.

  Preferably, one active part is electrically connected to one through conductor of one bushing, and the through conductor is electrically insulated from the above-mentioned closing lid and guided through the closing lid. It is good to be. The bushing introduces an electrical connection from the outside into the casing. The electrical connection is insulated to the casing, in particular to the closing lid that is in electrical contact with the casing. Since the electrical connection is introduced through the closing lid, post-processing of the casing, for example post-processing by forming a hole for the through conductor, can be omitted.

  Advantageously, one active part is attached to a through conductor which can be implemented as a bolt, for example. In this way, the mounting of the active part is simplified.

  In particular, it is advantageous if the closing lid, the bushing and the active part constitute one unit that is preassembled outside the casing. In this case, the bushing is closed and attached to the lid, and the active part is attached to the through conductor. This can be done outside the casing and is therefore simpler than in a tight space environment inside the casing. Attachment of the entire pre-assembled unit can be done by inserting the active part into the opening until the closing lid rests on the flange. Thereafter, it is only necessary to attach the closing lid to the flange.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

It is a fragmentary sectional view of the surge arrester by a prior art. It is a fragmentary sectional view of the surge arrester by this invention. FIG. 2 is a detailed view of a portion of FIG. 1.

  In all the drawings, parts corresponding to each other are denoted by the same reference numerals.

  FIG. 1 shows a known surge arrester 1 according to Patent Document 1 mentioned above. One encapsulated fluid-tight casing 21 has a tubular casing wall 22, which is provided with a flange 38 at each end of the tube. A high voltage bushing 34 is attached to the flanges 38 on the high voltage connection side, and a lid 39 is attached on the ground connection side so as to be fluid tightly closed. The casing 21 is mainly made of a conductive material such as steel or aluminum, and is grounded during operation. The lid 39 is, for example, a single plate made of metal, and may have one pressure relief opening 35 that is closed by a rupture plate or a film (not shown). Further, the lid 39 has one opening for the ground side bushing 15 for each active part 2 arranged in the casing 21. The high voltage bushing 34 includes an insulating portion 36 made of an electrically insulating material such as a casting resin and a frame portion 37 in which the insulating portion 36 is combined. The active portion 2 arranged in the casing 21 is provided in the insulating portion 36. A plurality of high-voltage contacts 28 are fitted so as to correspond to each one. Via the high voltage contact 28, a high voltage potential can be introduced into the casing 21 from the outside without risk of flashover between the high voltage and the ground casing 21.

  In the casing 21, one or more active parts 2 are arranged between the ground connection side 32 and the high voltage connection side 31. Here, three active parts 2 are arranged in the casing 21, but only two of them are visible because of the cross-sectional view. Each active part 2 has one cylindrical arrester element 20 extending along the longitudinal axis 30. The arrester element 20 is generally configured as a stack composed of a cylindrical varistor element group having one voltage-dependent resistance. One end mounting bases 23 and 24 are arranged at both ends of the arrester element 20, respectively. For example, a plurality of restraining elements 25 made of glass fiber reinforced resin surround the arrester element 20 parallel to the longitudinal axis 30 and are fixed to the end mounting bases 23 and 24 under tension. These restraining elements 25 are also used to press the varistor element groups together, thereby making good electrical contact between the varistor elements and holding the stack together. These restraining elements 25 also serve to protect the stack, for example so as to prevent the varistor elements from coming off during transport. On the ground connection side 32, the end mounting base 23 is directly fitted or preferably screwed to the through conductor 16. The through conductor 16 is a ground contact. As a result, an electrical contact portion for the outside of the casing 21 is formed, and the electrical contact portion is connected to the ground during operation.

  On the high voltage connection side 31, the end mounting base 24 has a shielding hood 27. The shielding hood 27 is used to shield the corners or edges of the end mount 24 against a high voltage electric field.

  2 and 3 show an embodiment of a surge arrester 1 according to the present invention. In FIGS. 2 and 3, three active parts 2 are arranged in the fluid-tight casing 3, but only two or one of them can be seen because of the cross-sectional view. The casing 3 is configured in a bowl shape with a conductive material. The substantially cylindrical side wall 4 transitions to the bottom 5 without a break in the region of the ground connection side 32. The transition is performed in the bulging portion 10. The side wall 4 and the bottom part 5 are integrally formed, and are cast from, for example, steel or aluminum.

  On the side facing the bottom 5, the casing 3 is closed with a lid 6. The lid 6 is implemented as a high voltage bushing 34. There, a disc-shaped insulating portion 36 made of, for example, cast resin is provided in a ring-shaped frame 37. The high voltage contact 28 fitted in the insulating portion 36 achieves a conductive connection from the inside of the casing 3 to the outside. The lid 6 is attached to the flange portion 38 of the casing 3 by bolts. The tip end portion of the high voltage side end mounting base 24 of the active portion 2 is fitted into a corresponding concave portion of the high voltage contact 28, thereby fixing in a direction orthogonal to the longitudinal axis.

  The bottom 5 has one opening 7 for each active part 2, and the inside of the opening can introduce one active part 2 through the opening 7 along the longitudinal axis 30 into the casing 3. It is set to be possible. The cross section of the opening 7 has a square shape with rounded corners. However, it may be circular.

  The bottom 5 has a flange 9 that is rounded along the edge of each opening 7 and protrudes outward. The outer side of each flange 9 has a flat surface on which a closing lid 8 is placed. The flange 9 and the bottom 5 are integrally formed with the side wall 4 and are formed as a single cast part, for example.

  An active portion 2 is attached to the inside of the flange 9. The active part 2 is directly attached to the closing lid 8 and is either electrically connected to the closing lid 8 or attached via an electrically insulating intermediate piece.

  In the illustrated embodiment, the attachment is performed by a single bushing 15. The bushing 15 includes a single through conductor 16 that is introduced from the outside into the casing 3 and a bushing body 17 that includes two parts made of an electrically insulating material such as cast resin. A first part of the bushing body 17 is outside the closed lid 8, and a second part is inside the closed lid 8. One or both portions of the bushing body 17 may have a sealing member for the closing lid 8. The through conductor 16 penetrates both parts of the bushing body 17 and the closing lid 8. The closing lid 8 is preferably made of a conductive material, for example a metal. In this case, the through conductor 16 is electrically insulated from the closing lid 8. The through conductor 16 has a shoulder at the outer end thereof, and the shoulder is supported by the bushing body 17. The through conductor 16 has a male screw at its inner end, and the end mounting base 23 of the active portion 2 is screwed onto the male screw. Thereby, the active part 2 is electrically insulated from the closing lid 8 and the casing 3. Therefore, the closing lid 8, the bushing 15, and the active part 2 constitute one unit that can be assembled outside the casing 3. For this purpose, the through conductor 16 is inserted through the first portion of the bushing body 17 and the hole of the closing lid 8. Further, from the other side of the closing lid 8, the second portion of the bushing body 17 is fitted onto the through conductor 16, and the active portion 2 is screwed onto the through conductor 16. For this purpose, the end mounting base 23 on the ground side of the active part 2 has a corresponding internal thread oriented in the longitudinal direction 30. Fluid tightness is ensured by the two sealing members 19.

  The unit assembled in advance in this way is incorporated into the casing 3. When the active part 2 is introduced into the casing 3 through the opening 7 along its longitudinal axis 30, the closing lid 8 will rest on the flange 9. At that time, on the opposite side, that is, on the high voltage connection side 31, the tip of the end mounting base 24 fits into a corresponding recess of the high voltage contact 28 of the high voltage bushing 34. The closing lid 8 is attached to the flange 9 by a bolt 18. The seal member 19 is set so that the casing is closed in a fluid-tight manner.

The inner diameter of the casing 3, that is, the inner diameter measured in a direction orthogonal to the longitudinal axis 30 is tapered toward the bottom 5 and increases toward the lid 6. Thereby, if the wall thickness of the casing 3 is almost equal, a larger outer diameter is generated in the range of the lid 6, that is, on the high voltage side than in the range of the bottom portion 5, that is, on the ground side. On the high voltage side, a significantly higher voltage is generated in the active part 2 than on the ground side. For this reason, on the high voltage side, both the insulation distance between the plurality of active parts 2 and the insulation distance between one active part 2 and the normally grounded casing 3 are both larger than those on the ground side. Must be big. In the prior art, the casing inner diameter is constant over the casing length and is designed based on the required insulation distance on the high voltage side. In comparison, the configuration according to FIG. The casing 3 has a diameter equal to that of the prior art only in the range on the high voltage side, but has a diameter that is clearly reduced compared to that over the majority of the height of the casing 3. Thus to, on the one hand, saves material for the casing manufacture, and, so that the fluid insulated by reduced volume, for example, SF ₆ is saved on the other hand.

DESCRIPTION OF SYMBOLS 1 Surge arrester 2 Active part 3 Casing 4 Side wall 5 Bottom part 6 Lid 7 Opening 8 Closing lid 9 Flange 10 Swelling part 15 Earth side bushing 16 Penetration conductor 17 Bushing body 18 Bolt 19 Sealing member 20 Arrester element 21 Casing 22 Casing wall 23 End part Mounting base 24 End mounting base 25 Restraining element 27 Shielding hood 28 High voltage contact 30 Long axis 31 High voltage connection side 32 Ground connection side 34 High voltage bushing 35 Pressure relief opening 36 Insulating part 37 Frame 38 Flange 39 Earth side cover

Claims (8)

A surge arrester (1) having at least one active part (2) arranged in a fluid-tight casing (3),
The casing (3) has a side wall (4) and a bottom (5), and an end facing the bottom (5) is closed by a lid (6);
The side wall (4) and the bottom (5) are integrally formed,
The bottom (5) has one opening (7) for each said active part (2), through which said one active part (2) can be introduced,
Surge arrester (1), characterized in that each said opening (7) is fluid-tightly closed by a closing lid (8). Surge arrester (1) according to claim 1,
Surge arrester (1), wherein each opening (7) is provided as an opening led to the outside of the bottom (5) by one dedicated flange (9). Surge arrester (1) according to claim 1 or 2,
Surge arrester (1) characterized in that the inner diameter of the casing tapers toward the bottom (5) and increases toward the lid (6). Surge arrester (1) according to one of claims 1 to 3,
Surge arrester (1), characterized in that the closing lid (8) and the opening (7) are square, in particular square. Surge arrester (1) according to one of claims 1 to 4,
Surge arrester (1), wherein each active part (2) is attached to one closing lid (8). Surge arrester (1) according to one of claims 1 to 5,
One bushing (15) has one through conductor (16) electrically connected to one active part (2), and the through conductor (16) is electrically connected to the closing lid (8). Surge arrester (1) characterized in that it is insulated with respect to the closed lid (8). Surge arrester (1) according to claim 6,
The surge arrester (1), wherein the active part (2) is attached to the through conductor (16). Surge arrester (1) according to claim 6 or 7,
The closing lid (8), the bushing (15), and the active part (2) form a single unit that can be assembled separately from the casing (3). Surge arrester (1).