Disconnecting device and protective-gas-insulated medium-voltage power switchgear

Abstract

The present invention relates to a disconnecting device, comprising: at least one contact (6), which has a first spring apparatus (13, 16) in order to form a pressing force against a counter contact (7); and a holding device (11, 12) for the contact (6), characterized in that a thermal conduction device (22, 23, 24, 25, 31, 32, 35) is designed to press the holding device (11, 12) and the contact (6) against each other. The present invention further relates to protective-gas-insulated medium-voltage power switchgear having the disconnecting device according to the invention.

Description

[0001] The invention relates to a disconnector according to the preamble of claim 1 and to a protective gas-insulated medium-voltage power switchgear according to claim 6.

[0002] Gas-insulated medium-voltage power switchgear is known, for example, from the product brochure "Fixed-Mounted Circuit-Breaker Switchgear, Type 8DA and 8DB up to 40.5 kV, Gas-Insulated," Catalog HA 35.11 2006, Siemens AG, Order No.: E50001-K1435-A101-A9. Pages 14 to 18 show examples of switchgear with separate switchgear for each medium-voltage phase. Each switchgear is housed in a fluid-tight enclosure and electrically insulated with the protective gas sulfur hexafluoride. A vacuum interrupter serves as the circuit breaker. A three-position disconnector with the switching positions Open, Close, and Earth is connected in series. In the Closed position, the disconnector electrically connects the vacuum interrupter to a busbar.

[0003] On page 18 of the brochure, the second image from the top shows the On position. The disconnector has a plurality of contacts designed as contact fingers arranged in pairs, with a gap between the pairs of contact fingers to accommodate a mating contact connected to the busbar. Four pairs of contact fingers are provided so that, depending on the high currents to be switched, eight contact points are formed between the contact fingers and the mating contact. The contact fingers are arranged in a cage or box as a holding device, from which the contact fingers protrude. To generate a pressing force on the mating contact, a first spring device is provided which presses the contact fingers against the mating contact to form a connection with good electrical conductivity.

[0004] Like any electrical device, gas-insulated medium-voltage switchgear with current-carrying components must be cooled to dissipate the power loss generated by the resistance. This is achieved primarily by transferring the lost heat into the protective gas, i.e., by convection. The heat is dissipated to the environment via the switchgear's metallic enclosure. High currents and resistances lead to high power loss, which increases the temperature within the switchgear. Normative limits must be observed at contact points. This limits the potential currents to ensure safe operation of the metal-enclosed, gas-insulated switchgear.In addition to heat dissipation through the atmosphere within the enclosure by convection, non-current-carrying components also serve to dissipate heat through conduction, transferring the heat to the enclosure components at available interfaces, which ultimately dissipate it to the environment. The temperature limit ranges for corresponding interfaces and connection variants are defined by standards and must not be exceeded, for example, according to IEC 62271-1, Edition 20.0 2017-7.

[0005] At the contact transition point between the movable contact fingers and the fixed contact, the current path constriction leads to high contact resistance. This, along with the high current, causes high power dissipation and generates high temperatures on the contact fingers and the fixed contact. For example, the aforementioned standard IEC 62271-1 stipulates for the contact fingers on pages 64 and 65 that when using carbon hexafluoride as a not-oxidizing gas (NOG, see "Point 5" on page 67) and an ambient temperature of maximum 40°C, the contacts may reach a maximum temperature of 115°C if the contacts are made of pure copper or are coated with silver or nickel. The ambient temperature must be taken into account here, because heat transfer always depends on a temperature difference between the interior of the housing and the environment. Other standards, such as the IEEE Standard C37.100, which is valid in the USA, apply.1-2018, page 28, even specifies a maximum temperature of 105°C for the same conditions. The corresponding GBT standard applicable in China also specifies 105°C.

[0006] Until now, measures to cool particularly hot components have been implemented by enlarging the cooling surfaces using additional heat sinks within the system enclosure. Materials with particularly good thermal conductivity properties, such as aluminum or copper, are used for the heat sinks. The heat is dissipated to the housing components by pure convection and thermal radiation. Alternatively, the resistance of the main current path is lowered, thus reducing the resulting power loss, which enables higher currents. However, this usually means an increase in the cross-section in the conductive main current path, which is only possible to a very limited extent within a given installation space. For particularly high currents, such as the one according to the aboveIf the current to be tested is 3150A according to IEC 62271-1, high temperatures occur inside the switchgear enclosure and active cooling of the switchgear housing by external fans may be necessary to comply with the prescribed temperature limits of the contacts and other components.

[0007] On the other hand, moving components such as fans are generally not included inside the enclosure, as additional moving parts are inherently more prone to failure and thus potentially require shorter service lives and shorter maintenance intervals. For this reason, operators of medium-voltage switchgear reject such designs.

[0008] Furthermore, the publications GB 569 088 A and DE 10 2004 056622 B3 are known, which deal with isolating devices for switchgear.

[0009] The object of the invention is to provide a separating device based on known separating devices which allows a comparatively high heat dissipation to the environment and at the same time can be manufactured cost-effectively.

[0010] The invention solves this problem by a separating device according to claim 1.

[0011] The disconnector is preferably designed for use in a medium-voltage power switchgear system. The so-called primary distribution level for medium-voltage typically has voltages between 12 kV and 40.5 kV, which requires vacuum switching technology in such systems. Disconnectors are also required to ensure reliable galvanic isolation.

[0012] For example, contact fingers arranged in pairs can be used. Depending on the expected currents to be switched, anything from a single contact finger to five or more pairs of contact fingers can be used.

[0013] The first spring device can, for example, comprise a spiral spring or a disc spring. A leaf spring can also be advantageously used. The spring device pushes or pulls the contact and mating contact together in the ON position to ensure good electrical conductivity. Preferably, one spring device is used per contact or contact finger. Alternatively, a single spring can be selected for all contacts.

[0014] The holding device positions the contacts within the housing and is rotatable, for example, in order to be able to assume the different switching positions.

[0015] The first spring device and / or the holding device are preferably made of a non-magnetic material to avoid additional heating and interference effects caused by magnetic fields and induced currents. Steel and iron are therefore generally ruled out, while copper, aluminum, or brass are suitable due to their comparatively low cost.

[0016] The holding device can, for example, be designed as a box or cage that surrounds the contacts or contact fingers and supports them springily.

[0017] The heat-conducting device with the second spring mechanism enables the heat loss generated by heat conduction at the contact points between the contacts and the mating contact to be more effectively dissipated to the holding device. This significantly increases the available surface area for heat dissipation.

[0018] The heat-conducting device is designed to create a pressure force between the holding device and the contact by means of a second spring device. This is advantageous because it ensures a connection with high thermal conductivity.

[0019] The second spring device is made of a non-magnetic material to avoid additional heating and interference from magnetic fields and induced currents. Steel and iron are therefore generally unsuitable, while copper, aluminum, or brass are suitable due to their comparatively low cost. The second spring device can, for example, comprise a coil spring or a disc spring. A leaf spring can also be used advantageously.

[0020] In a preferred embodiment of the separating device according to the invention, the heat conducting device is arranged on the holding device.

[0021] In a preferred embodiment of the separating device according to the invention, the heat-conducting device is arranged on the contact. For example, the contact can be designed as a contact finger, essentially as a flat, cuboid-shaped workpiece made of metal. The contact can have a recess on its longest side for receiving the heat-conducting device with the second spring device, so that the heat-conducting device does not unnecessarily increase the required installation space for the contact in the separating device. Accordingly, the heat-conducting device is pressed out of the recess only to bridge a small gap over the contour of the contact. For example, the gap is smaller than 10 mm, preferably smaller than 5 mm.

[0022] The heat-conducting device has a metallic contact material. Due to its high thermal conductivity, copper is preferably used, at least in part, for the heat-conducting device. Copper has the further advantage that it can be attached particularly cost-effectively using ultrasonic welding. Alternatively, aluminum or brass can be used, at least in part.

[0023] The metallic contact material comprises several stranded conductors. Stranded conductors have the advantage of being flexible and can therefore be easily bent and pressed by the second spring device. Preferably, the stranded conductors can be combined into a stranded bundle, e.g., by twisting. Alternatively, the strands in the bundle can be arranged essentially parallel and provided with a cap or welded at their free ends.

[0024] The metallic contact material is made at least partially of copper. Due to its high thermal conductivity, copper is preferably used, at least partially, for the heat-conducting device. Copper has the further advantage that it can be attached particularly cost-effectively using ultrasonic welding.

[0025] In a preferred embodiment of the separating device according to the invention, the heat-conducting device essentially comprises a non-magnetic material. This avoids additional heating and disruptive effects caused by magnetic fields and induced currents. Steel and iron are therefore generally ruled out, while copper, aluminum, or brass are non-magnetic and particularly suitable due to their comparatively low cost.

[0026] Several contacts are designed as contact fingers arranged in pairs, with a gap being formed between the pairs of contact fingers to accommodate the mating contact.

[0027] In a preferred embodiment of the isolating device according to the invention, the isolating device is designed as a three-position isolating device with the switching positions EARTH, OFF and ON, wherein in the switching position ON the at least one contact is pressed onto the counter contact.

[0028] The object of the invention is to provide a switchgear based on known protective gas-insulated medium-voltage power switchgear which allows a comparatively high heat dissipation to the environment and at the same time can be manufactured cost-effectively.

[0029] The invention solves this problem by a protective gas-insulated medium-voltage power switchgear according to claim 6.

[0030] The vacuum switching arrangement includes, for example, a vacuum interrupter to quickly extinguish the arc during separation.

[0031] In a preferred embodiment of the inventive, gas-insulated medium-voltage power switchgear, the medium-voltage power switchgear has a fluid-tight housing designed to be filled with a sulfur hexafluoride-free, electrically insulating protective gas. For example, so-called "clean air," i.e., essentially moisture-free compressed air, or a mixture of essentially nitrogen and carbon dioxide, can be used. This is advantageous because replacing the climate-damaging sulfur hexafluoride gas generally results in lower electrical insulation capacity. The energy absorption and energy dissipation are also often comparatively lower. Thus, the inventive solution can be advantageously used to facilitate the dissipation of heat from the contacts to the housing.By using the heat conduction device, the system is able to transfer the power loss to the cooler housing very efficiently through heat conduction. This heat conduction process occurs independently of the insulating gas used and the set gas pressure. The switchgear can therefore be designed more cost-efficiently while simultaneously transmitting high currents.

[0032] In a preferred embodiment of the inventive, gas-insulated medium-voltage power switchgear, the isolating device is spaced from the housing by an electrically non-conductive and non-magnetic holding means. This is advantageous because it ensures electrical insulation of the current path from the housing. The holding means can, for example, be made of a plastic, a ceramic, or a cast resin.

[0033] In a preferred embodiment of the protective gas-insulated medium-voltage power switchgear according to the invention, the holding means is designed to transport heat from the holding device to the housing. This enables heat conduction to the outside, while also creating an additional possibility for dissipating heat via the surface of the holding means to the protective gas inside by convection. The holding means preferably has a thermal conductivity of at least 2.5 W / (m*K). A thermal conductivity of more than 3.5 W / (m*K) is particularly advantageous.

[0034] In a preferred embodiment of the inventive, gas-insulated medium-voltage power switchgear, the holding means is rotatably mounted on the housing and movable by means of a drive device arranged outside the housing to set the earth, off, and on positions of the disconnecting device. This is advantageous because this design is simple and proven. For example, a motor can be provided for automatic control of the disconnecting device and / or a hand crank for manual operation.

[0035] To better explain the invention, the following schematic representations show Figure 1 shows a known 3-position disconnector of a protective gas-insulated medium-voltage power switchgear, and Figure 2 shows a first embodiment of a disconnecting device according to the invention, and Figure 3 shows a second view of the disconnecting device according to Figure 2, and Figure 4 Components of a dismantled separating device according to Figure 2 , and Figure 5 shows a first embodiment of a heat conducting device, and Figure 6 shows a second schematic view of the heat conducting device according to Figure 5 , and Figure 7 shows a second embodiment of a heat conducting device, and Figure 8 shows a second embodiment of a separating device according to the invention.

[0036] Within the framework of the preceding description and the following presentation of preferred exemplary embodiments, it will be apparent to the person skilled in the art that different variants of the embodiments and exemplary embodiments can be freely combined in order to constructively implement the basic idea according to the invention of improved heat dissipation from the contacts of the separating device.

[0037] The Figure 1shows an excerpt of a known protective gas-insulated medium-voltage power switchgear with a fluid-tight metal housing 1 made of, for example, cast aluminum (AlSi10Mg), which is designed to be filled with an electrically insulating protective gas. A busbar 2 is connected to a mating contact 7, which is essentially designed as a flat forged part.

[0038] The isolating device 3 has a holding device 5 with four pairs of contacts, which are designed as so-called isolating fingers or contact fingers 6. The diagram shows the switched-on state, in which the contacts 6 touch the mating contact 7 and provide a current path via a joint 3 and a conductor 8 to the vacuum circuit breaker (not shown). An earth contact 4 serves to earth the isolating device or the vacuum circuit breaker. The holding device 5 with the contacts 6 can be moved in a semicircular arc from the illustrated ON switching position via OFF (holding device 5 perpendicular and in line with conductor 8) to earth contact 4 for the EARTH switching position.

[0039] Figure 2 and Figure 3show two views of a separating device 6, 9, 10-16 according to the invention, which is spaced from the housing 1 by an electrically non-conductive and non-magnetic holding means 9. The holding means 9 is designed for heat transport from the holding device to the housing. At the same time, it provides a large surface for heat dissipation by convection to the surrounding protective gas. The holding means 9 is rotatably attached to the housing. It is movable by means of a drive device 14 arranged outside the housing in order to set the switching positions EARTH, OFF, and ON of the separating device. In addition, a plain bearing with high thermal conductivity is provided as a contact transfer point to the housing.

[0040] The holding means 9 is essentially shoe-shaped; it tapers towards the sliding bearing or drive device 14. The sole 15 is shaped to serve as a fastening for a box-shaped holding device 11, 12, 13, 14 for the eight contacts 6, which are designed as contact fingers with contact points 10 for the mating contact. Each pair of contact fingers 6 is spaced apart by a gap bridged by two first spring devices 13, 14, each designed as a spiral spring. If the holding means 9 is rotated, the holding device 11 rotates with it and pushes the contact fingers 6 at their contact points 10 onto a mating contact. The holding device 11 is essentially box-shaped and has two webs 12 at the end facing away from the contact points 10; it is made of cast aluminum (AlSi10Mg).

[0041] Figure 4shows components of a disassembled separating device, in particular contacts 6 with the first spring devices 13, 16 and contact points 10. Mounting plates 21, 26 serve to attach the contacts 6 in the holding device 11. For heat dissipation by conduction, the contacts 6 each have a heat conducting device 22 which, in the assembled state, connects the holding device 11 and the contacts.

[0042] Figure 5 shows a first embodiment of a heat-conducting device 22, which has a first flat area 26, a bundle of stranded copper wires 23, and a terminal clamp 24. The terminal clamp 24 reconnects the individual strands of the stranded wire bundle.

[0043] Figure 6 and 7 show a schematic detailed view of the embodiment according to Figure 5The contact finger 22 has a contact area 10 and a recess 33 at the longest edge of the essentially cuboid-shaped contact 22. A non-magnetic, metallic spring plate—preferably a copper spring plate 25—is arranged in the recess 33 as a second spring device for clamping the copper stranded wire 22 against the inside of the cage or box of the holding device. Rivets 32 or screws are used to connect the copper spring plate 25 and the contact finger 22. Copper stranded wire has a high thermal conductivity of approximately 370 W / (m*K). They are preferably arranged at the attachment point 32 using the very cost-effective ultrasonic welding method. Alternatively, the more expensive method of electron beam welding can also be used.

[0044] Direct heat dissipation through conduction is made possible by the newly installed solid bodies 22 within the separator. The large surface area of ​​the holding device 11, or the so-called separator cage, already achieves a medium single-digit temperature reduction at the contact fingers 6. In addition, heat is transferred to the housing 1 via the holding means 9.

[0045] Simultaneously maintaining insulation from the current paths ensures that no additional components need to be installed in the critical dielectric field area. Heat transfer takes place in the so-called field shadow, so no additional design measures are required that would increase the distances to the interior of the housing. This variant is considered cost-neutral compared to a design with alternative heat sinks, which are usually mounted externally on the housing parts of heated components, due to the complexity of the assembly sequence.

[0046] As an alternative to the flat spring 25, the stranded bands 22 could be screwed to the holding device 11, but this requires more assembly effort because typically up to 10 stranded bands have to be screwed manually.

[0047] Instead of stranded wire strips 23, copper lamella strips (small current strips) produced by resistance welding could alternatively be used, which are screwed together.

[0048] Figure 8 shows an alternative embodiment of the separating device in which the heat conducting device is firmly connected to the inside of the holding device with copper stranded wire 22 and spring plate 25.

Claims

1. Disconnecting device for a protective-gas-insulated medium-voltage circuit-breaker switchgear, having at least one contact (6), which has a first spring device (13, 16) for forming a pressure force on a counterpart contact (7), and having a holding device (11, 12) for the contact (6), characterized in that a heat-conducting device (22, 23, 24, 25, 31, 32, 35) is configured to press the holding device (11, 12) and the at least one contact (6) against one another to facilitate removal of heat from the contacts to a housing of the protective-gas-insulated medium-voltage circuit-breaker switchgear, wherein multiple contacts (6) are in the form of contact fingers arranged in pairs, wherein a gap for receiving the counterpart contact (7) is formed between the pairs of contact fingers, and in that the heat-conducting device (22, 23, 24, 25, 31, 32, 35) is configured to produce a pressure force between the holding device (11, 12) and the contact (6) by means of a second spring device (25) composed of substantially non-magnetic material, and in that the heat-conducting device (22, 23, 24, 25, 31, 32, 35) has multiple stranded conductors which are formed at least in part from copper.

2. Disconnecting device according to Claim 1, characterized in that the heat-conducting device (22, 23, 24, 25, 31, 32, 35) is arranged on the holding device (11, 12).

3. Disconnecting device according to Claim 1, characterized in that the heat-conducting device (22, 23, 24, 25, 31, 32, 35) is arranged on the contact (6).

4. Disconnecting device according to one of the preceding claims, characterized in that the heat-conducting device (22, 23, 24, 25, 31, 32, 35) has substantially non-magnetic material.

5. Disconnecting device according to one of the preceding claims, characterized in that the disconnecting device (6, 9, 10-16) is in the form of a three-position disconnecting device with the switching positions EARTH, OFF and ON, wherein, in the switching position ON, the at least one contact (6) is pressed onto the counterpart contact (7).

6. Protective-gas-insulated medium-voltage circuit-breaker switchgear having a vacuum switching arrangement and a disconnecting device (6, 9, 10-16) according to one of Claims 1 to 5.

7. Protective-gas-insulated medium-voltage circuit-breaker switchgear according to Claim 6, characterized in that the medium-voltage circuit-breaker switchgear has a fluid-tight housing (1) which is configured for filling with a sulphurhexafluoride-free electrically insulating protective gas.

8. Protective-gas-insulated medium-voltage circuit-breaker switchgear according to Claim 6, characterized in that the disconnecting device (6, 9, 10-16) is spaced apart from the housing (1) by way of an electrically non-conductive and non-magnetic holding means (11).

9. Protective-gas-insulated medium-voltage circuit-breaker switchgear according to Claim 8, characterized in that the holding means (9) is configured for heat transport from the holding device (11) to the housing (1).

10. Protective-gas-insulated medium-voltage circuit-breaker switchgear according to one of Claims 6 to 9, characterized in that the holding means (11) is rotatably mounted on the housing (1) and is movable by means of a drive device (14), which is arranged outside the housing (1), in order to set the switching positions EARTH, OFF and ON of the disconnecting device (6, 9, 10-16).

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