WO2020057915A1

WO2020057915A1 - Surge arrester having a pressure relief device and production method for a surge arrester

Info

Publication number: WO2020057915A1
Application number: PCT/EP2019/072854
Authority: WO
Inventors: Markus Sulitze
Original assignee: Siemens Aktiengesellschaft
Priority date: 2018-09-17
Filing date: 2019-08-27
Publication date: 2020-03-26

Abstract

The invention relates to a surge arrester having a pressure relief device, characterized in that the pressure relief device has a pressure relief valve. The present invention also relates to a production method for a surge arrester.

Description

description

Surge arrester with a pressure relief device and manufacturing method for a surge arrester

The invention relates to a surge arrester according to the preamble of claim 1 and a manufacturing method according to claim 9.

Surge arresters are used in the medium-voltage and high-voltage range in order to reliably reduce so-called overvoltages, i.e. voltages far above the nominal voltages provided during operation. This will damage equipment such as Avoided transformers. For example, a surge arrester for high voltage can be arranged on an overhead line and lead to impermissibly high currents to earth in the event of a lightning strike or short circuit.

Surge arresters usually contain So-called varistors (“variable resistors”), ie electrical resistors whose electrical resistance value is very high up to a design-related threshold voltage and greatly reduced above the threshold voltage, so that the surge arrester becomes a good electrical conductor. For example, metal oxide resistors arranged in disks one above the other in a housing and connected to the high-voltage potential and the earth potential at the respective ends of the housing. The surge arrester is hardly conductive during normal operation, so that only a small leakage current flows to the earth .

From the publication EP 2998970 Bl a surge arrester is known, which is equipped to improve the mechanical stability with a tubular housing made of an insulating material such as porcelain or glass fiber reinforced plastic. On the tube-like housing, a second housing with screens that extend the creepage distance and is made of a silicone material is arranged. Inside is a lead column arranged with several stacked disc-shaped Varis gate blocks. The discharge column is fixed between two end fittings, which at the same time close the tubular housing. In order to enable the surge arresters to be installed, the arrester column is pre-assembled during manufacture in a first step. For this purpose, the disc-shaped varistor blocks are arranged between two holding plates. The deflecting column formed in this way is looped under tension by means of elastic tensioning devices, which are each fixed to the holding plates and run between the holding plates. The pre-assembled deflecting column can then be inserted in a second step by means of a crane from above into the vertical tubular housing. Then the end fittings and the second housing can be added. Air surrounds the discharge column within the fluid-tight tubular housing. In the event of a fault, pressure can build up inside the surge arrester due to heat. In order to prevent the housing from being destroyed in an uncontrolled manner as a result of pressure build-up, a pressure relief device is provided which is designed as a membrane between the air-filled interior and the surroundings. The diaphragm is designed in such a way that it tears in the interior of the housing in the event of a design-related overpressure and can thus release overpressure into the environment.

It is also known from the publication "Breathable Membrane" by G. Barenthin and M. Sulitze, The IP.com Journal, December 2006, Volume 6, Number 12A, ISSN 1533-0001, page 132, instead of a fluid-tight one Membrane to use a membrane that is liquid-tight and yet allows gas exchange with the inside of the housing, thus overpressure can be safely relieved and, in addition, the air exchange with the surroundings improves cooling of the inside of the arrester. The invention has for its object to provide a generic surge arrester which is comparatively easy to manufacture and particularly safe in operation.

The invention solves this problem by a surge conductor according to claim 1.

The invention has the advantage that an overpressure in the arrester can be reduced non-destructively if an increased temperature arises inside as a result of high electrical stress. Another advantage is that the surge arrester performs better because less heat builds up in the interior.

In a preferred embodiment of the surge arrester according to the invention, an essentially tubular housing is closed with end fittings, a first end fitting having an opening at which the pressure relief valve is arranged. This is an advantage because end fittings are often made of metal such as Steel or aluminum are manufactured and therefore particularly good for making defined openings, e.g. by drilling. For example, an electrically non-conductive material such as e.g. a glass fiber reinforced plastic is used.

In a further preferred embodiment of the surge arrester according to the invention, the pressure relief valve is releasably attached to the first end fitting. This is an advantage because it allows easy valve replacement. Furthermore, the valve can be easily removed to perform a leak test by applying a defined excess pressure through the opening. If the applied overpressure falls within a predetermined period of time, the surge arrester has not been manufactured to be fluid-tight. For example, a screw connection or a bayonet lock can be selected to form the detachable connection. In a further preferred embodiment of the surge arrester according to the invention, the pressure relief valve has an external thread and is detachably screwed into the opening of the first end fitting, the opening having an internal thread. This is an advantage because the two threads create a simple and durable detachable connection. For example, commercially available screw-type pressure relief valves from Gore can be used, which can be found in the product brochure "Protective Vents screw-in series", code number PTV-031-R9-DSH-DE-JUNE 8, W. L. Gore & Associates GmbH, 2018 be used.

In a further preferred embodiment of the surge arrester according to the invention, the pressure relief valve is fixed to the first end fitting with an adhesive connection. This is an advantage because an adhesive connection is simple and inexpensive.

In a further preferred embodiment of the surge arrester according to the invention, the pressure relief valve has a larger diameter than the diameter of the opening and is glued in an overlap area over the opening. This is an advantage because the valve can be glued on from the outside, which is simple and saves time in production.

In a further preferred embodiment of the surge arrester according to the invention, the Druckentlastungsvor direction has a membrane which is designed to tear when exceeding a design-related pressure drop. This is an advantage because the additional use of the membrane further increases safety: if, for example, the pressure relief valve fails and the pressure cannot be reduced in time without destruction, the membrane tears. In a further preferred embodiment of the surge arrester according to the invention, the opening for receiving the pressure relief valve is arranged in the membrane.

The object of the invention is to provide a method for producing a surge arrester, with which a surge arrester can be comparatively easily manufactured and which can also be operated particularly safely.

The invention solves this problem by a method according to claim 9.

The process takes advantage of the fact that an opening is already provided in the end fitting for the pressure relief valve. This opening is used to automatically stack varistor blocks in the tubular housing. This eliminates the need to pre-assemble the lead column and to stabilize it mechanically using elastic loops or glass fiber-reinforced tension rods. The method according to the invention thus has the advantage of admitting a particularly simple, fast, material-saving and inexpensive production to previous methods of production. Furthermore, the method according to the invention is easy to automate, which brings further cost advantages.

It is known from the publication "Assembly of high-voltage arresters" by Erhard Pippert, Prior Art Journal, # 19 2017, pages 102 and 103, to stack varistor blocks directly in a housing. The varistor blocks are held by a movable, temporary resistance holder or A lifting rod is brought into position. At the lower end of the housing there is a transfer to a temporary stack holder. The lower closure parts are placed on the resistance holder, whereupon the entire stack is moved up again. The resistance holder remains in position until the lower ones The resistance stack is now in the correct position and can be mounted at the top as usual, in contrast to the solution according to the invention It is therefore proposed in the prior art to carry out several intermediate steps after stacking in the housing and before assembling the lower closure (or an end fitting): the temporary stack holder is first required to hold the varistor stack in the housing, which Lifting rod is withdrawn, the lower closure parts are placed on the lifting rod and finally fixed to the housing after removal of the temporary stack holder. Consequently, the method according to the invention can be implemented more easily and quickly without a temporary stack holder, which offers cost advantages compared to the prior art.

In a preferred embodiment of the manufacturing method according to the invention, the lifting means is withdrawn in each case by a length which essentially corresponds to a width of a varistor block. This is an advantage because it essentially results in a flat plane from an upper side of the lifting means or the last stacked resistance with the upper edge of the tubular housing. This means that a new resistor can simply be pushed sideways, which is particularly easy. Jamming is avoided.

Alternatively, for the first stacking step, the stroke can be arranged somewhat lower than the edge of the tubular housing, so that the resistance slides directly into the tubular housing when inserted and a lateral fixation takes place immediately. If the lifting device is too deep, e.g. by more than half a width of a varistor block, however, should be avoided so that no jamming can occur when inserting.

In a further preferred embodiment of the manufacturing method according to the invention, a lifting rod is used for the lifting means. A rod in the sense of the invention is any elongated body that is suitable in its cross section to be inserted through the opening. For example, a round cross section or a rectangular one Cross section for the lifting rod can be selected. A jamming of the resistors when stacking several times becomes less likely the larger the cross section of the opening and the lifting device is designed, because this increases the contact area between the lifting device and the resistor.

In a further preferred embodiment of the manufacturing method according to the invention, a lifting plate is used for the lifting means, which is releasably fixed to the lifting rod from above before the first placement of a varistor block, the lifting plate remaining between a varistor block and the first end fitting when the lifting rod is pulled out . The lifting plate can, for example, be of the same size or only slightly smaller than the varistor blocks, so that there is a maximum contact area between the varistor block and the lifting means. This is an advantage because jamming when lowering the resistors in the housing is prevented since no tilting conditions are possible. The lifting plate can, for example, as a disc made of an electrically conductive material such as be formed of a metal which has substantially the same dimensions as a varistor block. The lifting plate can have a recess in which the lifting rod can be fixed. In a simple case, the opening is a hole into which the lifting rod is inserted. However, it can also be provided, for example, by a screw connection.

In a further preferred embodiment of the manufacturing method according to the invention, a second end fitting is fixed in such a way on the other end of the tubular housing that the lead column is compressed between the two end fittings. This is an advantage because, on the one hand, the housing is sealed off in a fluid-tight manner and, on the other hand, good electrical contact between the individual varistor blocks with one another and with the respective end fittings is achieved by the compression. In a further preferred embodiment of the manufacturing method according to the invention, a second housing with shields extending the tracking path is fixed on the tubular housing. For example, a second housing made of a material can be applied in an injection molding step, which at least partially has a silicone rubber.

For a better explanation of the invention show the schematic representation

Figure 1 shows a first embodiment of a surge arrester, and

Figure 2 shows a second embodiment of a pressure relief device, and

Figure 3 shows a third embodiment of a pressure relief device, and

Figure 4 shows a first manufacturing step of a surge arrester, and

Figure 5 shows a second manufacturing step of a surge arrester, and

Figure 6 shows a third manufacturing step of a surge arrester, and

Figure 7 shows an alternative manufacturing step with egg lifting plate.

Figure 1 shows a first embodiment of a surge arrester 1. The surge arrester 1 has a tubular housing 2 made of a glass fiber reinforced plastic. A first end fitting 3 and a second end fitting 35 made of metal are provided at the ends of the tubular housing 2. Via the outside of the tubular housing 2 and in some cases also via the end fittings 3, 35, a two housing 19 made of a silicone rubber is applied in an injection molding process. The second housing 19 has shielding 20 extending creep path. Provided within the housing is a discharge column of length 13, which has varistor blocks 8 as electrical resistors. The electrical resistors 8 are clamped to form a column in that clamping means 7 are provided between holding plates 10, 12. The tensioning means 7 can be, for example, elastic bands known from the prior art or glass fiber-reinforced plastic rods tensioned under tension. The first end fitting 3 has an opening 14 into which a pressure relief device 6 is inserted. This is a pressure relief valve 6. The pressure relief valve 6 has an external thread 5 which is screwed into an internal thread of the end armature 5. The surge arrester 1 is thus sealed in a fluid-tight manner. Inside the surge arrester 1 there is 8 air between the tubular housing 2 and the lead column with the varistor blocks. This air can flow through a channel in the holding plate 12 and the pressure valve 6 to the outside (indicated by the arrow 4) when a great heat and associated overpressure occurs inside due to strong electrical stress.

Figure 2 shows a second embodiment of a pressure relief device. The first end fitting 3 is covered on the outside by a pressure relief valve 6. The opening 14 has a first diameter 17 which is smaller than a second diameter 16 of the pressure relief valve 6. As a result, an overlap area 15 is formed between the first end fitting 3 and the pressure relief valve 6 attached to the outside. In this overlap area 15, an adhesive connection between the pressure relief valve 6 and the first end fitting 3 is provided.

FIG. 3 shows a third exemplary embodiment of a pressure relief device, in which a step 40 for receiving a membrane 18 is formed in the first end fitting 3 is. In the stage 40, the membrane 18 is inserted and fastened. This can be done for example by means of an adhesive connection between the membrane 18 and the first end fitting 3. In this case, the opening 14 is provided within the membrane 18. For this purpose, the membrane 18 has an internal thread within the opening 14 into which the pressure relief valve 6 is screwed with its external thread 5.

FIG. 4 shows a first manufacturing step 21 of a surge arrester, in which a first end fitting 3 is placed on the tubular housing 2 at the bottom. The opening 14 in the first end fitting 3 has a diameter 24. A lifting means 23, which is designed as a lifting rod with a diameter 25, is inserted in the direction 22 from below through the opening 14 into the interior of the tubular housing 2. The diameter 25 of the lifting means 23 should be the same size or slightly smaller than the diameter 24 of the opening 14 in order to enable easy insertion and sliding through the fitting.

FIG. 5 shows a second production step, in which case the lifting means 23 is pushed into the tubular housing to such an extent that its upper edge lies at the same height as the upper edge of the tubular housing 2.

The inside of the tubular housing 2 has an inner diameter 30. For introduction into the tubular housing, Va ristorenblocks 8, which are each designed as disks with a diameter 31 and a width 34, are provided. The diameter 31 of the varistor blocks 8 is dimensioned such that it is the same size or slightly smaller than the diameter 30 in the interior of the tubular housing 2. This enables easy insertion and insertion of the varistor blocks 8 into the tubular housing. The manufacturing process provides that, starting from the state presented, the lifting rod 23 is pulled out a little in the direction of the device 26 from the end fitting 3 and the tubular housing 2. It is preferably retracted step by step by a length equal to the width 34 corresponds to a varistor disk 8. As a result, the cross-striped varistor block 8 is lowered down into the tubular housing until it forms a plane with its upper part and the upper edge of the tubular housing 2. By pushing in laterally along the direction 27, further blocks 8 can each be inserted on the lead column to be stacked. By repeated repetition of the lowering of the lifting means 23 in the direction 26 and lateral insertion of a further block 8 in the direction 27, the lifting rod 23 can be pulled out until finally the bottom varistor block 8 strikes a contact surface 29 of the first end fitting 3. This state is shown in FIG. 6. The advantage of this manufacturing process is given by the fact that intermediate steps for mechanical stabilization and pre-assembly of a lead column with varistor blocks 8 can be completely eliminated. In the prior art, such lead pillars with several varistor blocks 8 are usually assembled by bracing loops made of an elastic material or bracing using glass fiber reinforced plastic rods to form a pillar, which is then inserted as a complete part by crane from above into the tubular housing. The material for this mechanical stabilization and the additional work steps of the preassembly are completely eliminated, rather, in the production method according to the invention, the already existing opening 14 for the pressure relief valve 6 is used for this, by means of the lifting means 23, an easy to automate production directly into the housing 2 to be carried out. Another advantage is that the lead column can be made smaller than known in the prior art without tension for pre-assembly in diameter. This makes a smaller diameter of the tubular housing 2 and the second housing 19 possible with otherwise the same electrical performance of the arrester, which additionally saves material and costs and relieves the environment.

Figure 7 shows an alternative embodiment of the method, which is particularly advantageous when the diameter of the lifting means 23 and the opening 14 are comparatively small in relation to the diameter of the varistor blocks to be stacked. In such a case, there could be a tilting of the varistor blocks 8, because the contact surface between a varistor block 8 and the lifting rod 23 is comparatively small. In the worst case, jamming could occur, which prevents further stacking and assembly of the arrester. This problem can be avoided if the lifting plate 32 is provided. The lifting plate 32 is formed essentially with the same dimensions as a Va ristorenblock 8, but has a central recess 33 for receiving the lifting rod 23. In the simplest case, the lifting rod 23 is simply inserted into the lifting plate 32 from below. In this way, a maximally large contact surface is formed between the lifting plate 32 and a varistor block 8 indicated by a dashed line. Now, in the manner according to the invention, the lifting rod 23 is drawn downward out of the tubular housing and finally through the opening 14 out of the first end fitting 3, the hub plate 32 remains in the housing and contacts the first end fitting 3 at the stop 29.

Claims

1. surge arrester (1) with a pressure relief device (6.14),

characterized in that

the pressure relief device (6, 14, 18) has a pressure relief valve (6).

2. Surge arrester (1) according to claim 1, characterized in that

an essentially tubular housing (2) with end fittings (3, 6) is closed,

wherein a first end fitting (3) has an opening (14) at which the pressure relief valve (6) is arranged.

3. surge arrester (1) according to claim 2, characterized in that

the pressure relief valve (6) is detachably fixed to the first end fitting (3).

4. surge arrester (1) according to claim 3, characterized in that

the pressure relief valve (6) has an external thread (5) and is detachably screwed into the opening (14) of the first end fitting (3), the opening (14) having an internal thread.

5. surge arrester (1) according to any one of the preceding claims, characterized in that

the pressure relief valve (6) is fixed to the end fitting with an adhesive connection (15).

6. surge arrester (1) according to claim 5, characterized in that

the pressure relief valve (6) has a larger diameter (16) than the diameter (17) of the opening (14) and is glued over the opening (14) in an overlap area (15).

7. surge arrester (1) according to any one of the preceding claims, characterized in that the pressure relief device (6, 14, 18) has a membrane (18) which is formed to tear up if a pressure drop due to the design is exceeded.

8. surge arrester (1) according to claim 7, characterized in that the opening (14) for receiving the pressure relief valve (6) in the membrane (18) is arranged.

9. Manufacturing method (21) for a surge arrester, with the steps:

Fixing a first end fitting (3) with an opening (14) at one end of a substantially tubular housing (2), and

vertical installation of the tubular housing (2) so that the first end fitting (3) with the opening (14) is at the bottom angeord, and

Pushing (22) a lifting device (23) through the opening (14) to the other end of the tubular housing (2), and repeatedly placing (27) a respective varistor block (8) on the lifting device (23) and withdrawing the lifting device (23 ) until a deflection column having a plurality of varistor blocks (2) strikes the first end fitting (3), and

Pull out the lifting device (23).

10. Manufacturing method (21) according to claim 9, characterized in that

The lifting means (23) is withdrawn in each case by a length which essentially corresponds to a width (34) of a varistor block (8).

11. Manufacturing method (21) according to claim 9 or 10, characterized in that a lifting rod (23) is used for the lifting means (23).

12. Manufacturing method (21) according to claim 11, characterized in that a lifting plate (32) for the lifting means is used, which is releasably fixed on the lifting rod (23) from above before the first placement of a varistor block, the lifting plate (32) when the lifting rod (23) is pulled out between a varistor block (8) and the first display ( 3) remains.

13. Manufacturing method (21) according to one of claims 9 to 12, characterized in that a second end fitting (6) is fixed on the other end of the tubular housing (2) in such a way that the discharge column between the two end fittings (3.35 ) is pressed together.

14. Manufacturing method according to one of claims 9 to 13, characterized in that a second housing (19) with creep path-extending screens (20) on the tubular Ge housing (2) is fixed.