GB2050061A

GB2050061A - Medium voltage switch-gear

Info

Publication number: GB2050061A
Application number: GB8013377A
Authority: GB
Original assignee: Krone GmbH
Current assignee: ADC GmbH
Priority date: 1979-04-25
Filing date: 1980-04-23
Publication date: 1980-12-31
Also published as: BE882891R; NL8002262A; LU82374A1

Abstract

Medium voltage switch-gear includes a housing wall 10' which contains a liquid or gaseous insulating medium. An insulated part 11 is located within an aperture in the wall defines a tapering recess at the base of which is an electrical contact 4'. The contact is connected to parts within the housing and for the purpose of providing test facilities a capacitive voltage divider 11a can be located in the recess and held in sealing relationship therein by a retaining ring 11a'. The divider carries a first contact 4'' for connection with the contact 4' and a test contact 6'. <IMAGE>

Description

SPECIFICATION Medium voltage switch-gear This invention relates to medium voltage switch-gear incorporating load isolating and/ or circuit breaker switches and az plurality of cable outlets.

In an existing medium voltage switch-gear with load isolating or circuit breaker switches and a plurality of cable outlets, which was specifically developed with a view to providing a more reliable switch-gear which could be easily tested prior to installation and subsequently maintained, the switching device is accommodated in one part of the encapsulating housing which is adapted to be unscrewed from another housing part, both said parts, in use, containing a gaseous or liquid insulating medium.

Whilst it is known to use electro-negative gases, compressed air or liquids by way of insulating media for high tension equipment and, for example to make use of SF6 particularly for voltages upwards of 100 kV, the application of such media, e.g. SF6 has hitherto been unknown in the medium voltage sector.

One of the reasons for this is that for the purpose of testing the components of the switch-gear it has been necessary to partly dismantle the switch gear in order to gain access to the electrical connections therein.

The process of dismantling the switch-gear has. posed the problem of draining off the insulating medium and replacing the medium once testing has been completed. As a result it has been the practice to avoid if possible the aforesaid forms of insulating medium. In cases where it has proved necessary to employ the medium then the maintenance of the switch-gear and its testing has proved expensive.

It is the aim of the present invention to improve the said earlier developed medium voltage switch-gear in such a way as to provide facilities for cable testing by a direct electrical connection with the cable lead-ins without having to open the space which contains the gaseous or liquid insulating medium.

According to the present invention this aim is achieved thanks to the provision of a capacitive voltage divider, e.g. in the region of the cable inlet passage.

This provision has the advantage of enabling voltage tests to be carried out by fitting a capacitive voltage divider or alternatively a test probe.

Further advantageous aspects and significant, particularly constructional features of the invention are characterised in the sub-claims.

An embodiment of the invention is more particularly described with reference to the accompanying drawings wherein:- Figure 1 shows the insulating part in section, which is secured to the metal housing wall; Figure 2 is a sectional view showing the insulating part with the capacitive voltage divider fitted therein; and Figure 3 is a sectional view showing the insulating part with a gauge pin inserted therein.

With reference to the drawings, a section of the wall of the housing of the switch gear is shown at 10' and is formed from metal. A cup shaped electrically insulating part 11 extends through an aperture in the wall and has a flange which engages the outer surface of the wall about the aperture. The part 11 is retained by means of a ring 11' which is in screw-thread engagement with the part and which engages the inner surface of the wall. A sealing ring 12' is accommodated within a groove defined in the aforesaid flange to prevent the escape of the insulating medium 13' for example SF6 from the interior of the housing.

The internal wall of the part 11 tapers inwardly towards the base wall and secured in the base wall and extending to the interior of the housing is an electrical contact 4'. A cable connection 5' is connected to the contact 4' within the housing.

A capacitive voltage divider shown at 11 a in Fig. 2 can be located in the part 11 and retained therein by means of a threaded flanged ring 11 a' which is engaged with the part 11.

The ring has projections to facilitate tightening of the ring using a suitable tool. The body of the voltage divider 11 a has a tapered configuration and when the ring is tightened the gap 3' between the surface of the body and the tapered internal surface of the part 11 is sealed. The body of the divider is formed from silicone rubber.

The voltage divider 11 a mounts a contact 4" which when the divider is in position engages the contact 4' and a further contact terminal 6' which is accessible from the exterior of the housing for the purpose of testing.

If for some reason an alternative method of testing is required then the capacitive voltage divider 1 1a can be removed from the part 11 and a probe substituted in its place. This is shown in Fig. 3 where a pin located within an insulating body 7' is fitted into the part 11 and again retained by the ring 1 la'. The body 7' has a shape complementary to that of the internal surface of the part 11 to provide the aforesaid sealing function.

1. Medium voltage switch-gear incorporating load isolating and/or circuit breaker switches and a plurality of cable outlets, and wherein the switching device is accommodated in one part of an encapsulating housing which is adapted to be unscrewed from another housing part and which in use contains a gaseous or liquid insulating

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

SPECIFICATION Medium voltage switch-gear This invention relates to medium voltage switch-gear incorporating load isolating and/ or circuit breaker switches and az plurality of cable outlets.

In an existing medium voltage switch-gear with load isolating or circuit breaker switches and a plurality of cable outlets, which was specifically developed with a view to providing a more reliable switch-gear which could be easily tested prior to installation and subsequently maintained, the switching device is accommodated in one part of the encapsulating housing which is adapted to be unscrewed from another housing part, both said parts, in use, containing a gaseous or liquid insulating medium.

Whilst it is known to use electro-negative gases, compressed air or liquids by way of insulating media for high tension equipment and, for example to make use of SF6 particularly for voltages upwards of 100 kV, the application of such media, e.g. SF6 has hitherto been unknown in the medium voltage sector.

One of the reasons for this is that for the purpose of testing the components of the switch-gear it has been necessary to partly dismantle the switch gear in order to gain access to the electrical connections therein.

The process of dismantling the switch-gear has. posed the problem of draining off the insulating medium and replacing the medium once testing has been completed. As a result it has been the practice to avoid if possible the aforesaid forms of insulating medium. In cases where it has proved necessary to employ the medium then the maintenance of the switch-gear and its testing has proved expensive.

It is the aim of the present invention to improve the said earlier developed medium voltage switch-gear in such a way as to provide facilities for cable testing by a direct electrical connection with the cable lead-ins without having to open the space which contains the gaseous or liquid insulating medium.

According to the present invention this aim is achieved thanks to the provision of a capacitive voltage divider, e.g. in the region of the cable inlet passage.

This provision has the advantage of enabling voltage tests to be carried out by fitting a capacitive voltage divider or alternatively a test probe.

Further advantageous aspects and significant, particularly constructional features of the invention are characterised in the sub-claims.

An embodiment of the invention is more particularly described with reference to the accompanying drawings wherein:- Figure 1 shows the insulating part in section, which is secured to the metal housing wall; Figure 2 is a sectional view showing the insulating part with the capacitive voltage divider fitted therein; and Figure 3 is a sectional view showing the insulating part with a gauge pin inserted therein.

With reference to the drawings, a section of the wall of the housing of the switch gear is shown at 10' and is formed from metal. A cup shaped electrically insulating part 11 extends through an aperture in the wall and has a flange which engages the outer surface of the wall about the aperture. The part 11 is retained by means of a ring 11' which is in screw-thread engagement with the part and which engages the inner surface of the wall. A sealing ring 12' is accommodated within a groove defined in the aforesaid flange to prevent the escape of the insulating medium 13' for example SF6 from the interior of the housing.

The internal wall of the part 11 tapers inwardly towards the base wall and secured in the base wall and extending to the interior of the housing is an electrical contact 4'. A cable connection 5' is connected to the contact 4' within the housing.

A capacitive voltage divider shown at 11 a in Fig. 2 can be located in the part 11 and retained therein by means of a threaded flanged ring 11 a' which is engaged with the part 11.

The ring has projections to facilitate tightening of the ring using a suitable tool. The body of the voltage divider 11 a has a tapered configuration and when the ring is tightened the gap 3' between the surface of the body and the tapered internal surface of the part 11 is sealed. The body of the divider is formed from silicone rubber.

The voltage divider 11 a mounts a contact 4" which when the divider is in position engages the contact 4' and a further contact terminal 6' which is accessible from the exterior of the housing for the purpose of testing.

If for some reason an alternative method of testing is required then the capacitive voltage divider 1 1a can be removed from the part 11 and a probe substituted in its place. This is shown in Fig. 3 where a pin located within an insulating body 7' is fitted into the part 11 and again retained by the ring 1 la'. The body 7' has a shape complementary to that of the internal surface of the part 11 to provide the aforesaid sealing function.

1. Medium voltage switch-gear incorporating load isolating and/or circuit breaker switches and a plurality of cable outlets, and wherein the switching device is accommodated in one part of an encapsulating housing which is adapted to be unscrewed from another housing part and which in use contains a gaseous or liquid insulating medium, characterised by means secured in the wall of the housing which carries an electrical contact accessible from the exterior of the housing for the purpose of testing.

2. Switch-gear according to Claim 1 in which said means comprises an electrically insulating part which extends through an aperture in the wall of the housing.

3. Switch-gear according to claim 2 in which said part is secured by a threaded ring within the housing and sealing means is provided to provide a fluid seal.

4. Switch-gear according to Claim 2 including a capacitive voltage divider having a body which is located within a recess in said insulating part, said body being retained in said recess by a further threaded ring.

5. Switch-gear according to Claim 4 in which said body and the wall of said recess are tapered configurations, the gap between said body and wall of the recess being sealed by the pressure exerted by said further threaded ring.

6. Switch-gear according to Claim 5 in which the body of the voltage divider mounts a first contact for engagement with the contact carried by said part and a second contact accessible from the exterior of the housing.

7. Switch-gear according to Claim 3 in which said part defines a tapering recess, and a test probe including an insulating body is located within said recess and retained therein by a further threaded ring.

9. Medium voltage switch-gear incorporating load isolating and/or circuit breaker switches comprising the combination and arrangement of parts substantially as hereinbefore described.