ELECTRICAL SWITCHING ARRANGEMENT

Abstract

An electrical switching arrangement for an electrical power supply includes a live conductor. The live conductor includes electrodes for switching between first and second sides of the live conductor. The electrical switching arrangement also includes a ground conductor, an insulation block between the electrodes and the ground conductor, a first insulation member extending from the insulation block on the first side of the electrodes, and a second insulation member extending from the insulation block on the second side of the electrodes. The insulation block includes a first groove in which an edge of the first insulation member is located and a second groove in which an edge of the second insulation member is located.

Claims

1. An electrical switching arrangement for an electrical power supply, the electrical switching arrangement comprising: a live conductor, wherein the live conductor comprises a set of electrodes for switching between a first side of the live conductor and a second side of the live conductor; a ground conductor; an insulation block between the set of electrodes and the ground conductor; a first insulation member extending from the insulation block on the first side of the set of electrodes; and a second insulation member extending from the insulation block on the second side of the set of electrodes; wherein the insulation block comprises a first groove in which an edge of the first insulation member is located and a second groove in which an edge of the second insulation member is located.

2. The electrical switching arrangement as claimed in claim 1, wherein the live conductor comprises a live conducting plate and the ground conductor comprises a ground conducting plate.

3. The electrical switching arrangement as claimed in claim 2, wherein the live conducting plate and the ground conducting plate are substantially parallel to each other.

4. The electrical switching arrangement as claimed in claim 1, wherein the set of electrodes comprises a spark gap.

5. The electrical switching arrangement as claimed in claim 1, wherein the set of electrodes comprises an array of spark ball gaps.

6. The electrical switching arrangement as claimed in claim 1, wherein the insulation block member is formed from polyethylene.

7. The electrical switching arrangement as claimed in claim 1, wherein the edges of the insulation block are tapered in a direction towards the respective edges.

8. The electrical switching arrangement as claimed in claim 1, wherein the first and second insulation members comprise a first set of one or more insulation sheets and a second set of one or more insulation sheets.

9. The electrical switching arrangement as claimed in claim 8, wherein the first set of one or more insulation sheets are folded and tucked into the first groove and the second set of one or more insulation sheets are folded and tucked into the second groove.

10. The electrical switching arrangement as claimed in claim 8 or 9, wherein the first and second sets of one or more insulating sheets are made from a polyester.

11. The electrical switching arrangement as claimed in claim 1, wherein the first and second grooves are formed in a side of the insulation block facing the ground conductor.

12. The electrical switching arrangement as claimed in claim 1, wherein the first and second grooves extend in a direction perpendicular to the directions in which the first and second sides of the live conductor extend from the set of electrodes.

13. The electrical switching arrangement as claimed in claim 1, wherein the first groove extends into the insulation block at an angle of less than 90 degrees to the face of the insulation block in the direction in which the first insulation member extends from the first groove and the second groove extends into the insulation block at an angle of less than 90 degrees to the face of the insulation block in the direction in which the second insulation member extends from the second groove.

14. The electrical switching arrangement as claimed in claim 1, wherein the electrical switching device is arranged to connect a voltage source and a load, and the voltage source comprises one or more capacitors.

15. The electrical switching arrangement as claimed in claim 1, wherein the electrical switching arrangement is arranged to switch a voltage of at least 30 kV.

16. An electrical power supply for supplying an output voltage to a load, the electrical power supply comprising: one or more capacitors for generating a voltage, wherein the one or more capacitors comprise: a live terminal and a ground terminal; and an electrical switching arrangement for connecting the voltage generated by the one or more capacitors to the load, wherein the electrical switching arrangement comprises: a live conductor connected to the live terminal of the capacitor, wherein the live conductor comprises a set of electrodes for switching between a first side of the live conductor and a second side of the live conductor; a ground conductor connected to the ground terminal of the capacitor; an insulation block between the set of electrodes and the ground conductor; a first insulation member extending from the insulation block on the first side of the set of electrodes; and a second insulation member extending from the insulation block on the second side of the set of electrodes; wherein the insulation block comprises a first groove in which an edge of the first insulation member is located and a second groove in which an edge of the second insulation member is located.

Description

[0060] Certain preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0061] FIG. 1 shows schematically a system for supplying a high voltage pulse to a load through an electrical switching arrangement in accordance with the present invention; and

[0062] FIG. 2 shows schematically a cross-section of an electrical switching arrangement in accordance with an embodiment of the present invention.

[0063] Switching arrangements are important components in high voltage systems, e.g. when discharging a high voltage from a capacitor to deliver a high voltage pulse to a load. Embodiments of an electrical power supply and an electrical switching arrangement in accordance with the present invention will now be described.

[0064] FIG. 1 shows schematically an electrical power supply system 1 for supplying a high voltage pulse generated by a capacitor 4 to a load 6 through an electrical switching arrangement 2 in accordance with an embodiment of the present invention. The capacitor 4 (or array of capacitors) is connected to the electrical switching arrangement 2 (which comprises an array of spark ball gaps) by a first live conductor 8 and ground conductor 7. The load 6 is connected to the electrical switching arrangement 2 by a second live conductor 10 and ground conductor 9.

[0065] An embodiment of the electrical switching arrangement will now be described in more detail with reference to FIG. 2. FIG. 2 shows schematically a cross-section of an electrical switching arrangement 11 in accordance with an embodiment of the present invention.

[0066] The electrical switching arrangement 11 comprises an array of spark ball gaps 12 that connect a first side 14 and a second side 16 of a live conductor plate. The electrical switching arrangement 11 comprises a trigger 13 for triggering switching of the electrical switching arrangement 11.

[0067] The first side of the live conductor plate 14 connects the spark ball gaps 12 to the live output of a capacitor. The second side of the live conductor plate 16 connects the spark ball gaps 12 to a load. The electrical switching arrangement 11 also comprises a ground conductor plate 18 that extends across the electrical switching arrangement 11 between the capacitor and the load. The ground conductor plate 18 lies parallel to the first and second sides of the live conductor plate 14, 16.

[0068] A solid insulation block 20, formed from polyethylene, is positioned between the ground conductor plate 18 and the first and second sides of the live conductor plate 14, 16. The solid insulation block 20 is generally planar with tapered edges and two grooves 22, 24 formed in the side of the solid insulation block 20 that faces the ground conductor plate 18. The grooves 22, 24 extend into the thickness of the solid insulation block 20 at an acute angle and extend across the width of the solid insulation block 20, aligned with the sets of spark balls at the edges of the array of spark ball gaps 12.

[0069] A first set of eight 75 micron Mylar® insulation sheets 26 is folded into the first groove 22 of the insulation block 20. The first set of insulation sheets 26 extends from the first groove 22 along the surface of the insulation block 20 to and beyond the tapered edge of the insulation block 20. The first set of insulation sheets 26 extends from the edge of the ground conductor plate 18.

[0070] A second set of eight 75 micron Mylar® insulation sheets 28 is folded into the second groove 24 of the insulation block 20. The second set of insulation sheets 28 extends from the second groove 24 along the surface of the insulation block 20 to and beyond the tapered edge of the insulation block 20. The second set of insulation sheets 28 extends from the edge of the ground conductor plate 18.

[0071] The first and second insulation sheets 26, 28 coupled with the solid insulation block 20 provides a relatively low volume of insulation between the two sides of the live conductor plate 14, 16 and the ground conductor plate 18, thus helping to reduce the inductance of the electrical switching arrangement 11.

[0072] Operation of the electrical power supply and the electrical switching arrangement will now be described with reference to FIGS. 1 and 2.

[0073] To deliver a high voltage pulse from the capacitor 4 to the load 6 of the electrical power supply system 1, the capacitor 4 is first charged at a high voltage to store a large charge. As will be explained, the design of the electrical switching arrangement 11 shown in FIG. 2 helps to reduce the risk of dielectric breakdown of the charge on the capacitor, e.g. through the electrical switching arrangement 11.

[0074] As the capacitor 4 is being charged, the main route for dielectric breakdown (by surface tracking) between the first and second sides of the live conductor plate 14, 16 is via the side of the solid insulation block 20 that faces the ground conductor plate 18.

[0075] However, the route for any surface tracking is blocked by the first and second insulation sheets 26, 28 extending and folding into the first and second grooves 22, 24 of the solid insulation block 20. The first and second grooves 22, 24 and the first and second insulation sheets 26, 28 thus together form a trap for any surface tracking, thus reducing the risk of surface tracking via this route.

[0076] The first and second insulation sheets 26, 28 together with the solid insulation block 20 also provides a barrier between the first and second sides of the live conductor plate 14, 16 and the ground conductor plate 18. This reduces the risk of dielectric breakdown between these conductor plates 14, 16, 18.

[0077] When the capacitor 4 has been charged, the trigger 13 is energised to initiate corona discharge in the air between the spark balls of the spark ball gaps 12. This forms a conducting path across the spark ball gaps 12 between the first and second sides of the live conductor plate 14, 16 between the capacitor 4 and the load 6, thus allowing the capacitor 4 to discharge a high voltage and high current pulse through the electrical switching arrangement 11 to deliver to the load 6.

[0078] Owing to the reduced inductance of the electrical switching arrangement 11, the high voltage and high current pulse can be delivered quickly from the capacitor 4 to the load 6, through the electrical switching arrangement 11.

[0079] It will be seen from the above that, in at least preferred embodiments, the invention provides an electrical switching arrangement and electrical power supply that has a relatively low inductance while being able to be used to switch a high voltage and high current with a relatively low risk of dielectric breakdown and surface tracking.