WO2009076975A1

WO2009076975A1 - Medium-voltage switchgear assembly

Info

Publication number: WO2009076975A1
Application number: PCT/EP2007/011019
Authority: WO
Inventors: Dietmar Gentsch
Original assignee: ABB Technology AG
Current assignee: ABB Technology AG
Priority date: 2007-12-14
Filing date: 2007-12-14
Publication date: 2009-06-25
Anticipated expiration: 2010-06-14

Abstract

A low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in the preamble of patent claim (1). In order in this case to ensure that greater functional integration is made possible, the invention proposes that the disconnector is in the form of a three-position switch cartridge in which the switching element comprises a metallic piston which can be moved in an at least partially insulating ceramic (if appropriate) cartridge between the open and closed positions and grounded position via a pressure medium or fluid.

Description

Medium-voltage switchgear assembly

The invention relates to a low-voltage, medium-voltage or high-voltage switchgear assembly, as claimed in the preamble of patent claim 1.

In addition to a circuit breaker, which is generally permanently installed, electrical switchgear assemblies, in particular medium-voltage switchgear assemblies, also have a disconnector, which may assume three positions: connected position, disconnected position and grounding position; that is to say in the form of a three-position switch.

A connection is made to the live busbar in the connected position, and to ground in the grounding position. In the disconnected position, the moving contact piece of the disconnector is in a central position between the connected position and the grounding position.

Conventional three-position disconnectors are known in the form of linear-travel or knife switches. It is also known that an analogous functionality can advantageously also be provided by a "three-position vacuum interrupter" . One such is known from DE 102 20 110 Al.

In general, disconnectors are used as an autonomous device in the same gas area as the load-break switch or circuit breaker or in a separate gas area, particularly in the case of double-busbar arrangements. The electrical part of these devices is always a component of the gas area and is connected by means of a gas- tight bushing to the drive, which is located outside the gas area and, for medium-voltage applications, is normally in the form of a mechanical or magnetic drive.

The disadvantages of this are as follows . As an autonomous device and if arranged in the same area as the load-break switch or circuit breaker, a disconnector requires a correspondingly large enclosure or, if arranged separately, its own gas area. The last- mentioned once again means additional bushings between the various gas areas.

Both situations involve additional complexity for material, assembly and testing. The dimensions of the switchgear assembly are correspondingly large. Furthermore, use in a solid- insulated installation or a pole part is not feasible in this form.

The invention is therefore based on the object of developing further a medium-voltage switchgear assembly of this generic type so as to allow greater functional integration.

In a medium-voltage switchgear assembly of this generic type, the stated object is achieved according to the invention by the distinguishing features of claim 1.

Further advantageous refinements are specified in the dependent claims .

The essence of the invention is that the disconnector is in the form of a three-position switch cartridge in which the switching element comprises an electrically conductive piston which can be moved in an at least partially insulated, (ceramic or plastic) , cartridge between the open and closed positions and grounded position via a pressure medium or fluid. In this case, via its outer casing, the correspondingly- moving piston switches said switch positions between the respective contacts which are arranged in or on the inner wall of the cartridge, which acts like a cylinder, and in which the piston can move. The cartridge may, of course, also be non-cylindrical (as a "flat" cartridge) .

In one advantageous refinement, the pressure medium of the fluid is carried in a closed pumped line system. The pressure which is required to move the piston can then be built up on an ad-hoc basis in this way for the switching process.

In a further advantageous refinement, the pressure medium or the fluid^' is insulating oil. The use of oil as a pressure medium has the advantage in comparison to gas of being considerably less compressible, thus allowing the switching process to be controlled more objectively.

The pressure medium may, however, also be SF₆ gas, which has excellent insulation characteristics.

Furthermore, in one advantageous refinement, the cartridge is provided with a window in the form of an elongated hole for viewing the piston position. As is normal in the case of a disconnector, this makes it possible to see the instantaneous switch position visually even in this special form.

In a further advantageous refinement, the pump is arranged directly adjacent to the center part or to the end parts of the switch cartridge. This results in short pressure-medium paths and thus fast switching operations. - A -

In a further advantageous refinement, the piston position or the switch positions are monitored via micro switches (or else visually) . The instantaneous switch position can also be checked in this way.

In one advantageous refinement, the switch cartridge is cylindrical and is closed at both ends by covers, with at least one of the covers being transparent . The instantaneous position of the piston can also be seen visually via this cover.

In a further advantageous refinement, the switch cartridge is incorporated in a plastic or an insulating material, thus resulting in a solid- insulated pole part. The disconnector is therefore in the form of a pole part .

In a further advantageous refinement, the switch cartridge is integrated in a connecting flange such that this results in a two-position or three-position bushing for a switchgear assembly.

In a final advantageous refinement, the current is transferred to the piston via a current strip, a spiral contact or else a multicontact strip.

Overall, the result of this is as follows:

For compact low-voltage, medium-voltage and high- voltage switchgear assemblies with high functional integration, it appears to be advantageous to arrange the disconnector - in the form of a three-position switch cartridge - directly in functionally relevant parts, for example a cartridge in the gas area, or to integrate it as a cast-resin bushing, or to design the three-position switch cartridge such that (with its insulators) it itself forms the bushing. In the first- mentioned case, the encapsulation technology is well known and is prior art .

The normal object of a three-position switch cartridge is to connect the live current paths of different gas areas and to isolate them from the grounded encapsulation. At the same time, the bushing can provide mechanical robustness between different enclosures, and can also keep them spaced apart. It is also possible to integrate this simple device in a switchgear assembly, freely suspended, since there is no need for any drive via a conventional spindle or else a push rod. In consequence, there is also no need for any rotating bushings either. Furthermore, it is possible to encapsulate the three-position switch cartridge in a pole part, thus creating a solid- insulated installation or device.

The invention is illustrated in the drawing and will be described in more detail in the following text.

The drawing uses one exemplary embodiment to show a three-position switch cartridge comprising one or two insulators 1 and the two or three required metal parts 2, 3, 8 which transfer the current via a multicontact strip or a spiral contact 5 to an inner piston element

4 (conductiveIy) . The piston 4 may be in the three positions: connected position, disconnected position

(central position) or else grounding position. In order to move to a new position, the piston 4, which is sealed from the enclosure, is moved by oil pressure (or compressed air, or SF₆ gas as a minimum) of the insulating oil. For this purpose, a toothed-wheel pump or piston pump 6 (or else some other (volume) controlled pump) is arranged on the system and, when a switching movement takes place, pumps the oil (the air, the gas) from one volume in the device to the other volume, and moves the piston in a corresponding manner. The pressure medium areas are sealed by means of an 0-ring seal 7 which rests on the piston 4 and is therefore inserted, forming a seal, between the piston 4 and the enclosure.

The load-break switch or circuit breaker is connected to one side of the three-position switch cartridge. The three-position switch cartridge, as an electrical part of the disconnector, may be completely encapsulated in cast resin, in which case the cast-resin body may be in the form of a bushing.

The other side of the three-position switch cartridge forms the direct connection to the busbar.

On the other hand, the connection of the three-position switch cartridge may be linked to a solid- insulated rail, such that it can be plugged in. In this case, the bushing is designed to be proof against direct contact on the side associated with the busbar, that is to say provided with a conductive coating. The busbar may be connected via a plug contact which is part of the bushing.

The proposed two-position or three-position switch is based on an intrinsically closed cartridge which is filled with a small amount of insulating oil preferably - (or compressed air or else SF₆ gas as minimum) .

In the case of the three-position switch, the cartridge itself comprises two insulators and the three required metal parts, see the drawing, which transfers the current via a multicontact strip or a spiral contact to an inner piston element (conductiveIy) . The piston may be located at the three positions: connected position, disconnected position (central position) or else grounding position. In order to be moved to a new position, the piston, which is sealed against the enclosure, is moved by oil pressure (or compressed air, or SF₆ gas as a minimum) of the insulating oil. For this purpose, a toothed-wheel pump or piston pump (or else some other volume-controlled pump) is arranged on the system and, when a switching movement occurs, pumps the oil (the air, the gas) from one volume of the device into the other volume, and moves the piston in a corresponding manner.

The functional advantages are:

• Physically small cartridge and can also be used in solid- insulated switchgear (SIS) .

• High dielectric strength of the assembly, minimum oil filling (or gas filling, for example also air or SF₆) .

• Hermetically sealed from the outside.

• Drive comparatively very small (no spindle and no rotation protection required on the piston) . • The position of the switch (position of the piston) can be monitored via a window or transparent components .

• Possibly, no SF₆ gas in the device, only an insulating oil - preferably - or compressed air (for example environmentally friendly silicone oil or dry air) , which is also used for drive purposes (via the oil or air pump) .

• A micro switch or optical switch can also be integrated in the device (preferably under oil) . • Based on a technique which is already available in house, cast-resin insulators and metallic covers for transmission of the current (+ multicontacts or spiral contacts) . Comparatively low production cost.

Claims

Patent Claims :

1. A low-voltage, medium-voltage or high-voltage switchgear assembly, having at least one circuit breaker and at least one disconnector, wherein the disconnector is in the form of a three-position switch cartridge in which the switching element comprises an electrically conductive piston (4) which can be moved in an at least insulating, for example partially ceramic, cartridge between the open and closed positions and grounded position via a pressure medium or fluid.

2. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in claim 1, wherein the pressure medium or the fluid is carried in a closed pumped line/pump system (6) .

3. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in claim 1 or 2 , wherein the pressure medium or the fluid is insulating oil.

4. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in claim 1 or 2 , wherein the pressure medium or the fluid is SF₆ gas.

5. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in one of the preceding claims, wherein the cartridge, that is to say the enclosure which is composed of metallic (2, 3, 8) and insulating, ceramic, plastic or filled plastic elements (1) , is provided with a window in the form of an elongated hole for viewing the piston position.

6. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in one of the preceding claims, wherein the pump (6) is arranged directly adjacent to the center part or to the end parts of the switch cartridge.

7. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in one of the preceding claims, wherein the piston position or the switch positions are monitored via a micro switch system, an optical sensor switch system or via a proximity sensor switch system.

8. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in one of the preceding claims, wherein the switch cartridge has a cylindrical, oval or "flat" cuboid or rectangular format and is closed at both ends by covers (2, 3) .

9. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in claim 8, wherein at least one of the two covers may be transparent.

10. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in one of the preceding claims, wherein the switch cartridge is incorporated in a plastic or an insulating material, thus resulting in a solid- insulated pole part .

11. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in one of the preceding claims, wherein the switch cartridge is integrated in a connecting flange such that this results in a two-position or three-position bushing for a switchgear assembly.

12. The low-voltage, medium-voltage or high-voltage switchgear assembly as claimed in one of the preceding claims, wherein the current is transferred to the piston (4) via a current strip, a spiral contact or else a multicontact strip (5) .