GB2551307A

GB2551307A - Electrical switching assembly

Info

Publication number: GB2551307A
Application number: GB1605996.6A
Authority: GB
Inventors: Hubert John Hopkins WIlliam; Jones Brian; Newton Christopher
Original assignee: J W & E Morris & Son Ltd
Current assignee: J W & E Morris & Son Ltd
Priority date: 2016-04-08
Filing date: 2016-04-08
Publication date: 2017-12-20
Anticipated expiration: 2036-04-08
Also published as: GB2551307B

Abstract

An electrical arc suppressor actuating assembly 200 reconfigures an arc suppressor 207 between electrically conducting and isolating states in dependence on the rotation of a shaft 202, rotatably coupled to a housing 201 and connected to the arc suppressor via coupling means 203,205. The actuating assembly may be arranged to maintain the suppressor in conducting or isolating states as the shaft rotates through respective first and second rotational ranges, which may be non-overlapping. The coupling means may comprise an actuating arm 205 pivotally coupled to the housing, and a cam 203 rotatably coupled to the housing. The shaft and cam may be rigidly coupled together and arranged to rotate about a common rotational axis. A switching assembly for high voltage circuits (figure 1) may comprise first and second electrical terminals 101,102, and a contact 106 arranged to pivot around the first terminal in an angular range comprising: a first range (contact forms a first path between the terminals), a second range (contact forms a second path between the terminals and the arc suppressor actuating assembly), and a third range (two terminals are electrically isolated). The first and second ranges may partially overlap with each other and be non-overlapping with the third range.

Description

ELECTRICAL SWITCHING ASSEMBLY

The present invention relates to an electrical arc suppressor actuating assembly. The present invention also relates to an electrical switching assembly and particularly but not exclusively to an electrical switching assembly for switching high voltage electrical circuits.

Electrified overhead lines for powering trains and the like typically operate with a high electrical potential difference, such as 25kV. In the event that a section of the overhead line requires repairing, then it is necessary to remove electrical power from whole sections of the line before any work can commence. This is clearly disruptive to passengers and affects regions of the rail network when only a specific section of line may require repair.

Accordingly, electrical switching assemblies are typically sited along the length of electrified overhead lines so that sections of line can be electrically isolated for repair and maintenance. However, when switching electrical circuits carrying high voltages and electrical currents, it is well known that electrical arcing can occur between electrical contacts as the contacts open and close. This arcing is clearly dangerous and damages the switching assemblies leading to premature failure.

We have now devised an improved electrical switching assembly.

According to a first aspect of the present invention, there is provided an electrical arc suppressor actuating assembly for reconfiguring an arc suppressor between a first state in which the suppressor is arranged to pass an electrical current and a second state in which the suppressor is arranged to prevent the passage of an electrical current, the assembly comprising a housing, a shaft rotatably coupled with the housing, and coupling means disposed within the housing for mechanically coupling the shaft with the suppressor, wherein the assembly is arranged to reconfigure the suppressor between the first and second state in dependence upon a rotational configuration of the shaft.

In an embodiment, the assembly is arranged to maintain the suppressor in the first state as the shaft rotates through a first rotational range, and is further arranged to maintain the suppressor in the second state as the shaft rotates through a second rotational range. The first and second rotational ranges are preferably nonoverlapping ranges.

In an embodiment, the coupling means comprises an actuating arm which is pivotally coupled at a proximal end thereof to the housing, and a cam which is rotatably coupled to the housing. In an embodiment, the shaft and cam are rigidly coupled together and arranged to rotate about a common rotational axis.

In an embodiment, the cam and arm extend in substantially the same plane.

In an embodiment, the cam comprises a first portion which is arranged to abut the arm along the first rotational range of the cam and a second portion which is arranged to abut the arm along the second rotational range of the cam. The first portion comprises a first arcuate portion of the cam which extends at a first radius from the rotational axis, and the second portion comprises a second arcuate portion of the cam which extends at a second radius from the rotational axis. The second radius is preferably greater than the first radius, such that as the cam rotates, the arm is arranged to pivot about its proximal end as the contact of the cam with the arm passes between the first and second portions.

In an embodiment, the cam is arranged to contact the arm at a position intermediate a proximal and distal end of the arm.

In an embodiment, the assembly comprises biasing means, such as a spring, for biasing the cam to rotate into a rotational configuration within the first and second rotational range.

In an embodiment, the assembly further comprises a catch arrangement rigidly coupled to the shaft for releasably engaging with a moveable contact of an electrical switching assembly.

In an embodiment, the housing further comprises means for securing an electrical arc suppressor thereto. The means may comprise apertures for receiving fasteners for example.

In an embodiment, the housing comprises a polycarbonate based moulding.

In an embodiment, the assembly further comprises an electrical arc suppressor.

According to a second aspect of the present invention, there is provided an electrical switching assembly for switching high voltage electrical circuits, the switching assembly comprising a first and second fixed electrical terminal, and a contact which is electrically connected to the first fixed terminal, the contact being pivotable about a proximal region thereof to form an electrical contact with the second fixed terminal, the contact being arranged to pivot through an angular range comprising: a first range, in which the contact forms a first electrical path between the first and second terminal, a second range in which the contact forms a second electrical path between the first and second terminals, the second electrical path comprising an electrical arc suppressor and an electrical arc suppressor actuating assembly according to the first aspect, and, a third range in which the first and second terminals are electrically isolated, wherein at least a portion of the first range and at least a portion of the second range overlap, such that both the first and second electrical paths exist for an angular range of movement of the contact.

In an embodiment, the third range is separate from the first and second range and is non-overlapping with the first or second range.

In an embodiment, the contact comprises a distal region having a first portion which is arranged to create the first electrical path and a second portion which is arranged to create the second electrical path.

In an embodiment, upon switching a circuit to an open circuit configuration, the second portion of the contact maintains an electrical path, namely the second path, between the first and second terminals after the first portion has moved to open the first electrical path between the first and second terminals. Similarly, upon switching a circuit to a closed circuit configuration, the second portion of the contact is arranged to establish the second electrical path between the first and second terminals before the first portion of the contact establishes the first electrical path.

In an embodiment, the electrical arc suppressor actuating assembly comprises a catch arrangement which is rigidly coupled to the shaft for releasably engaging with the second portion of the contact. The catch arrangement is preferably electrically connected with an electrical contact associated with the arc suppressor, and may comprise a forked arrangement of contactors.

In an embodiment, the catch arrangement and thus the shaft are arranged to rotate about the rotational axis of the shaft as the contact moves through the first and second angular range.

In an embodiment, the combined first and second angular range of the contact corresponds with the first and second rotational range of the cam, such that as the contact moves through the combined first and second angular range, the cam is arranged to move through the combined first and second rotational range.

In an embodiment, the switching assembly further comprises a third fixed electrical terminal disposed in the third angular range of the contact. The third terminal preferably comprises an electrical earth.

In an embodiment, the electrical switching assembly further comprise drive means for driving the contact to pivot within the first, second and third angular ranges. The drive means may comprise an electric motor or a manually operated drive unit.

Whilst the invention has been described above it extends to any inventive combination of the features set out above, or in the following description, drawings or claims. For example, any features described in relation to any one aspect of the invention is understood to be disclosed also in relation to any other aspect of the invention.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is plan view of an electrical switching assembly according to an embodiment of the present invention, with the contact arranged in the first angular range;

Figure 2 is a view of the electrical switching assembly illustrated in figure 1 from a first side;

Figure 3 is a view of the electrical switching assembly illustrated in figure 1 from a second side;

Figure 4 is perspective view of an electrical arc suppressor actuating assembly according to an embodiment of the present invention;

Figure 5a is a view through the actuating assembly illustrated in figure 3 from the underside;

Figure 5b is a view through the actuating assembly illustrated in figure 3 from the side; and,

Figure 6 is an view from the underside of the actuating assembly illustrated in figure 5, with a portion of the housing removed.

Referring to figures 1-3 of the drawings, there is illustrated an electrical switching assembly 100 for switching high voltage electrical circuits, such as circuits operating at a potential difference of 25kV. The switching assembly 100 is typically sited at an elevated position and is designed to switch high voltage electrified overhead lines (not shown) for powering trains and the like, but the skilled reader will recognise that the invention could be applied to other technical disciplines.

The switching assembly 100 comprises a first fixed electrical terminal 101, which may comprise the live electrical feed to the switching assembly 100 for example, a second fixed electrical terminal 102 which may comprise a neutral electrical terminal for example, and a third fixed terminal 103 which may comprise the electrical ground terminal, for example. The first, second and third terminals 101, 102, 103 separately comprise a substantially linear, elongate conductor 101a, 102a, 103a and in the case of the first and second terminals 101, 102, the respective conductors 101a, 102a extend through a respective electrically insulating bushing of stacked ceramic discs 104. The terminals 101, 102, 103 are orientated substantially vertically and mounted on a support base 105.

The fixed terminals 101, 102, 103 are oriented substantially parallel and configured to a substantially trigonal configuration. The assembly 100 further comprises a contact 106 which is pivotally coupled at a proximal end thereof to an upper region of the first terminal 101 (however, the skilled reader will recognise that the contact may instead be pivotally coupled to an upper region of the second terminal 102). The contact 106 is electrically coupled with the conductor 101a of the first terminal 101 and is arranged to pivot in first a horizontal plane through an angular range which enables the contact to separately form an electrical connection with the conductors 102a, 103a of the second and third electrical terminals 102,103.

The contact 106 comprises a substantially linear, elongate body 106a and a distal region of the contact comprises a first and second portion 107, 108 which are separately arranged to form a first and second electrical path between the first and second terminals 101, 102. The first portion 107 is substantially collinear with the body 106a of the contact 106 and is arranged to form a mechanical sliding contact with a receiving portion 109 of the second terminal 102. In this respect, the first electrical path is created and maintained through an angular range of movement of the contact 106, while the first portion 107 of the contact 106 remains in sliding contact with the receiving portion 109.

The second portion 108 of the contact extends within a second horizontal plane, which in use, is disposed above the first horizontal plane and is electrically coupled to the body 106 via a bridging member 110. The bridging member 110 and second portion 108 may be formed integrally and diverge from the first portion 107 within a horizontal plane, as illustrated in figure 1 of the drawings. The second portion 108 of the contact 106 comprises a pin 111, which extends substantially vertically therefrom and is arranged to locate within a catch arrangement 210 of an electrical arc suppressor actuating assembly 200, according to an embodiment of the present invention, as illustrated in figures 3-6 of the drawings.

The electrical arc suppressor actuating assembly 200 comprises housing 201 and a shaft 202 which is rotationally coupled to a housing 201, which may comprise a polycarbonate moulding for example. The shaft 202 is arranged to rotate about a substantially vertical rotational axis and extends from within the housing 201, out from the housing 201. Referring to figure 5 and 6 of the drawings, a proximal region of the shaft 202 is rigidly coupled to a cam 203 disposed within the housing 201, such that the cam 203 is arranged to rotate in conjunction with the shaft 202, about the rotational axis, within a substantially horizontal plane. The cam 203 comprises an arcuate cam surface 204 and a first portion 204a of the cam surface 204 extends at a first radius from the rotational axis whereas a second portion 204b of the cam surface 204 extends at a second radius from the rotational axis, which is greater than the first radius.

The cam surface 204 is arranged to abut an arm 205 located within the rotational plane of the cam 203. The arm 205 is pivotally coupled at a proximal end 205a thereof to the housing 201 and the cam surface 204 is arranged to contact the arm 205 at a region intermediate opposite ends of the arm 205. The first portion 204a of the cam surface 204 is arranged to abut the arm 205 as the cam 203 rotates through a first rotational range and the second portion 204b of the cam surface 204 is arranged to abut the arm 205 as the cam 203 rotates through a second rotational range, which is separate from the first rotational range. In this respect, as the cam 203 passes between the first and second rotational ranges, the differing radii of the first and second portions 204a, 204b causes the arm 205 to pivot about its proximal end, and thus cause a distal end 205b of the arm 205 to deflect through an actuating range.

The arm 205 is hingedly coupled at the distal end 205b thereof to an actuating armature 206 of an electrical arc suppressor 207, which may comprise a vacuum bottle for example, for quickly extinguishing electrical arcs. The arc suppressor 207 is detachably coupled to the housing 201 via fasteners 208 which extend through the housing 201 into a body of the arc suppressor 207 and the actuating armature 206 extends from the suppressor 207 into the housing 201 of the actuating assembly 200. Accordingly, as the arm 205 pivots about its proximal end 205a, the armature 206 is arranged to move longitudinally of the suppressor 207 to reconfigure the suppressor 207 between a first state in which the suppressor 207 is arranged to pass an electrical current and a second state in which the suppressor 207 is arranged to prevent the passage of an electrical current. The arc suppressor 207 itself comprises a live and neutral electrical terminal (not shown) and the live terminal is electrically connected to the shaft 202 of the actuating assembly 200, whereas the neutral terminal (not shown) is electrically connected to the second fixed terminal 102, such that electrical current is required to pass through the arc suppressor 207 in passing from the first to the second fixed terminal along the second path.

The actuating assembly 200 and electrical arc suppressor 207 are detachably coupled to a bracket 209 mounted upon the second fixed terminal 102. The catch arrangement 210 of the actuating assembly 200 comprises a pair of contactors 211, 212 which are coupled at a proximal end to the shaft 202, whereas a distal end of the contactors 211, 212 diverge away from each other in a horizontal plane to facilitate the locating of the pin 111 between the contactors 211, 212 as the contact 106 moves relative to the second terminal 102.

The contactors 211, 212 comprise a linear portion disposed intermediate the proximal and distal ends thereof, and the linear portions are configured to extend in a substantially parallel configuration within a horizontal plane. The contactors 211,212 are electrically coupled with the shaft 202 and the pin 111 is arranged to form an electrical contact with the contactors 211,212.

Referring to figure 1 of the drawings, the contact 106 (illustrated with the solid line) is shown in a first orientation in which the first electrical path is formed directly between the first and second electrical terminals 101, 102. In this configuration, electrical current, which is typically in excess of 1000A, is configured to pass from the first terminal 101, through the body of the contact 106 and the first portion 107 of the contact 106, through the receiving portion 109 of the second terminal 102, and out from the assembly 100 via the second terminal 102. This configuration represents the situation with the switching assembly 100 in the fully closed state.

With the switching assembly 100 configured in this fully closed state, the second electrical path also exists in which electrical current is permitted to pass from the first terminal 100, through the body of the contact 106 and the second portion 108 of the contact 106, through the pin 111 and into the actuating assembly 200 via the contactors 211, 212 and shaft 202. The electrical current is further permitted to pass through the arc suppressor 207 owing to the closed state of the suppressor 207 and out from assembly 100 via the second terminal 102. However, owing to the reduced electrical resistance of the first path compared with the second path, the electrical current preferentially passes along the first path.

When it is desired to reconfigure the switching assembly 100 to the fully open configuration, the contact 106 is caused to pivot about the first terminal 101. This may be achieved by a drive unit (not shown) which may comprise an electrical motor or a manually operated drive unit for example. As the contact 106 is pivoted, the first electrical path will be maintained while the first portion 107 remains in contact with the receiving portion 109. In this respect, the first electrical path will remain while the contact 106 passes through a first angular range. During this movement however, the pin 111 located upon the second portion 108 of the contact 106 will begin to move along and between the contactors 211, 212 of the catch arrangement 210, as the contact 106 moves relative to the second terminal 102. This results in the contactors 211, 212 and thus the shaft 202 rotating about the rotational axis which drives the cam 203 to rotate.

As the contact 106 moves out of the first angular range and into a second angular range, the first electrical path will open owing to the first portion 107 of the contact moving out of electrical contact with the receiving portion 109. However, this transition from the first to the second angular range of the contact 106 does not prevent the current from flowing between the first and second terminals 101, 102, since electrical current can instead pass along the second electrical path which comprises the arc suppressor 207.

As the contact 106 continues to pivot about the first terminal 101, the shaft 202 will continue to rotate about the rotational axis and once the cam 203 has rotated through a first rotational range, the second portion 204b of the cam surface 204a will abut the arm 205 to cause the arm 205 to pivot and thus lift the armature 206 relative to the arc suppressor 207 to cause the suppressor 207 reconfigure to an open configuration and thus prevent electrical current from flowing along the second electrical path.

The high voltage difference between the first and second terminals 101, 102 causes an electrical arc to form between the terminals (not shown) of the suppressor 207, but this arc is quickly suppressed within the suppressor 207, namely within the vacuum bottle, to avoid excessive damage to the suppressor terminals. The arcuate length of the first portion 204a of the cam surface 204, in addition to the divergence of the second portion 108 of the contact 106 relative to the first portion 107 enables the first portion 107 of the contact 106 to become suitably separated from the receiving portion 109 to prevent any arc forming therebetween, which would otherwise be more damaging, since the arc between the first portion 107 and receiving portion 109 would not be confined within the arc suppressor.

As the contact 106 continues to rotate, the shaft 202 and cam 203 will continue to rotate until the contact 106 passes out from the second angular range. At this point, the pin 111 associated with the second portion 108 of the contact 106 will pass out from between the contactors 211, 212 and thus discontinue driving the shaft 202 about the rotational axis. This limit to the second angular range corresponds with the second rotational range of the cam 203.

Upon further driving the contact 106 into a third angular range, the first portion 107 is arranged to form an electrical connection with the third fixed terminal 103, which may comprise a electrically earthed terminal, to minimise any electrical shocks from the first terminal 101. This configuration of the contact 106 represents the situation with the switching assembly 100 in the fully open state.

When it is desired to reconfigure the switching assembly 100 from the open configuration to the closed configuration, the contact 106 is driven to pivot about the first terminal 101 away from the third terminal 103 toward the second terminal 102. As the contact moves out of the third angular range into the second angular range, the pin 111 associated with the second portion 108 will become captured between the contactors 211,212 of the catch arrangement 210. An electrical contact will thus be established between the pin 111 and the contactors 211,212, and thus the shaft 202. As the contact 106 continues to move through the second angular range, the cam 203 will rotate and as the cam 203 rotates from the second rotational range into the first rotational range, the arm 205 will pivot to cause the armature 206 to move relative to the arc suppressor 207 and thus cause the suppressor 207 to move to a closed configuration. As the cam 203 transitions from the second to the first rotational range and thus as the suppressor 207 reconfigures from the open to the closed configuration, an electrical arc will form between the terminals (not shown) of the suppressor 207 but this will become quickly extinguished to minimise any damage to the terminals thereof. The continued rotation of the shaft 202 and thus the cam 203, as the contact 106 pivots, will re-establish the second electrical path so that electrical current can pass between the first and second terminal 101, 102. Further pivoting of the contact 106 will cause the first portion 107 of the contact 106 to become electrically coupled with the receiving portion 109 of the second terminal 102 to re-establish the first electrical path, however owing to the current already flowing along the second path, no electrical arc is created between the first portion 107 and the receiving portion 109.

In order to ensure that the catch arrangement 210 remains in the required orientation to catch the pin 111 when switching the assembly 100 between the open and closed configuration, the actuating assembly 200 further comprises biasing means for biasing the cam 203 separately within the first and second rotational ranges. The biasing means comprises a spring 213 which extends at the underside of the cam 203, namely the side opposite the side to which the shaft 203 is coupled. The spring 213 is coupled at one end to a coupling point 214 on the housing 201 and at the other end to an anchor point 215 on the cam 203 which is angularly disposed equidistant between opposite ends of the arcuate cam surface 204. This creates an over-centre bias, whereby the spring 213 extends to a maximum extension at a rotational position of the cam 203 which aligns the spring 213 with an intersection between the coupling point 214 and the anchor point 215. As the cam 203 subsequently rotates in either direction, the spring will create a pulling force upon the cam 203 which will hold the cam in the corresponding rotational configuration until it is further driven to rotate by the contact 106.

From the foregoing therefore it is evident that the provision of a secondary electrical path comprising an electrical arc suppressor, in connection with the actuating assembly provides for an improved electrical switching assembly which enables the electrical connection between electrical terminals operating at a high potential difference to be disconnected and reconnected without having to first remove the electrical supply to the terminals.

Claims

1. An electrical arc suppressor actuating assembly for reconfiguring an arc suppressor between a first state in which the suppressor is arranged to pass an electrical current and a second state in which the suppressor is arranged to prevent the passage of an electrical current, the assembly comprising a housing, a shaft rotatably coupled with the housing, and coupling means disposed within the housing for mechanically coupling the shaft with the suppressor, wherein the assembly is arranged to reconfigure the suppressor between the first and second state in dependence upon a rotational configuration of the shaft.

2. An electrical arc suppressor actuating assembly according to claim 1, wherein the assembly is arranged to maintain the suppressor in the first state as the shaft rotates through a first rotational range, and is further arranged to maintain the suppressor in the second state as the shaft rotates through a second rotational range.

3. An electrical arc suppressor actuating assembly according to claim 1 or 2 wherein the first and second rotational ranges are non-overlapping ranges.

4. An electrical arc suppressor actuating assembly according to any preceding claim, wherein the coupling means comprises an actuating arm which is pivotally coupled at a proximal end thereof to the housing, and a cam which is rotatably coupled to the housing.

5. An electrical arc suppressor actuating assembly according to claim 4, wherein the shaft and cam are rigidly coupled together and arranged to rotate about a common rotational axis.

6. An electrical arc suppressor actuating assembly according to claim 4 or 5, wherein the cam and arm extend in substantially the same plane.

7. An electrical arc suppressor actuating assembly according to any of claims 4 to 6, wherein the cam comprises a first portion which is arranged to abut the arm along the first rotational range of the cam and a second portion which is arranged to abut the arm along the second rotational range of the cam.

8. An electrical arc suppressor actuating assembly according to claim 7, wherein the first portion comprises a first arcuate portion of the cam which extends at a first radius from the rotational axis, and the second portion comprises a second arcuate portion of the cam which extends at a second radius from the rotational axis.

9. An electrical arc suppressor actuating assembly according to claim 8, wherein the second radius is greater than the first radius, such that as the cam rotates, the arm is arranged to pivot about its proximal end as the contact of the cam with the arm passes between the first and second portions.

10. An electrical arc suppressor actuating assembly according to any of claims 4 to 9, wherein the cam is arranged to contact the arm at a position intermediate a proximal and distal end of the arm.

11 .An electrical arc suppressor actuating assembly according to any of claims 4 to 10, further comprising biasing means, for biasing the cam to rotate into a rotational configuration within the first and second rotational range.

12. An electrical arc suppressor actuating assembly according to any preceding claim, further comprising a catch arrangement rigidly coupled to the shaft for releasably engaging with a moveable contact of an electrical switching assembly.

13. An electrical arc suppressor actuating assembly according to any preceding claim, wherein the housing further comprises means for securing an electrical arc suppressor thereto.

14. An electrical arc suppressor actuating assembly according to claim 13, wherein the means comprise apertures for receiving fasteners.

15. An electrical arc suppressor actuating assembly according to any preceding claim, wherein the housing comprises a polycarbonate based moulding.

16. An electrical arc suppressor actuating assembly according to any preceding claim, further comprising an electrical arc suppressor.

17. An electrical switching assembly for switching high voltage electrical circuits, the switching assembly comprising a first and second fixed electrical terminal, and a contact which is electrically connected to the first fixed terminal, the contact being pivotable about a proximal region thereof to form an electrical contact with the second fixed terminal, the contact being arranged to pivot through an angular range comprising: a first range, in which the contact forms a first electrical path between the first and second terminal, a second range in which the contact forms a second electrical path between the first and second terminals, the second electrical path comprising an electrical arc suppressor and an electrical arc suppressor actuating assembly according to any preceding claim, and, a third range in which the first and second terminals are electrically isolated, wherein at least a portion of the first range and at least a portion of the second range overlap, such that both the first and second electrical paths exist for an angular range of movement of the contact.

18. An electrical switching assembly according to claim 17, wherein the third range is separate from the first and second range and is non-overlapping with the first or second range.

19. An electrical switching assembly according to claim 17 or 18, wherein the contact comprises a distal region having a first portion which is arranged to create the first electrical path and a second portion which is arranged to create the second electrical path.

20. An electrical switching assembly according to claim 19, wherein upon switching a circuit to an open circuit configuration, the second portion of the contact maintains the second electrical path between the first and second terminals after the first portion has moved to open the first electrical path between the first and second terminals.

21. An electrical switching assembly according to claim 19, wherein upon switching a circuit to a closed circuit configuration, the second portion of the contact is arranged to establish the second electrical path between the first and second terminals before the first portion of the contact establishes the first electrical path.

22. An electrical switching assembly according to any of claims 19 to 21, wherein the electrical arc suppressor actuating assembly comprises a catch arrangement which is rigidly coupled to the shaft for releasably engaging with the second portion of the contact.

23. An electrical switching assembly according to claim 22, wherein the catch arrangement is electrically connected with an electrical contact associated with the arc suppressor.

24. An electrical switching assembly according to claim 22 or 23, wherein the catch arrangement and the shaft are arranged to rotate about the rotational axis of the shaft as the contact moves through the first and second angular range.

25. An electrical switching assembly according to any of claims 17 to 24, wherein the combined first and second angular range of the contact corresponds with the first and second rotational range of the cam, such that as the contact moves through the combined first and second angular range, the cam is arranged to move through the combined first and second rotational range.

26. An electrical switching assembly according to any of claims 17 to 25, further comprising a third fixed electrical terminal disposed in the third angular range of the contact.

27. An electrical switching assembly according to claim 26, wherein the third terminal comprises an electrical earth.

28. An electrical switching assembly according to any of claims 17 to 27, further comprising drive means for driving the contact to pivot within the first, second and third angular ranges.

29. An electrical arc suppressor actuating assembly substantially as herein described and with reference to the accompanying drawings.

30. An electrical switching assembly substantially as herein described and with reference to the accompanying drawings.