Partial discharge detection test link, partial discharge detection system and methods for detecting partial discharge on a power cable

• US 20030151412A1
• Filed: 03/17/2003
• Published: 08/14/2003
• Est. Priority Date: 01/27/2000
• Status: Active Grant

• Current Assignee: Prysmian Cables & Systems Limited (Prysmian SPA)
• Original Assignee: Prysmian Cables Ltd. (Prysmian SPA)
• Inventors: Gregory, Brian, Barclay, Andrew Leslie
• Granted Patent: US 6,930,491 B2
• Time in Patent Office: Days
• US Class Current: 324/536
• CPC Class Codes: G01R 15/14 Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
• CPC Class Codes: G01R 15/181 using coils without a magnetic core, e.g. Rogowski coils
• CPC Class Codes: G01R 31/1272 of cable, line or wire insulation, e.g. using partial discharge measurements locating faults in cables G01R31/083
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72

Abstract

A partial discharge detection test link (20) and system detect partial discharge of a power cable at a power cable accessory (6). The power cable accessory includes a first accessory component and a second accessory component connected to each other. The partial discharge detection test link (20) is a permanent or temporary substitute for a conventional service link, connects directly across the power cable accessory and includes a conductor member (22) and a partial discharge sensor (24). The conductor member (22) has an electrically conductive element (26) and an insulation (28) surrounding and extending along the electrically conductive element. The electrically conductive element (26) is electrically connected directly between the first and second accessory components. The partial discharge sensor (24) is disposed about the conductor member (22) and has the electrically conductive element as a primary winding and a secondary winding with the insulation positioned between the primary and secondary windings. The partial discharge detection system includes the conductor member, the partial discharge sensor, a first converter device, a second converter device, and a partial discharge measuring instrument. The first converter device converts partial discharge electrical signals into alternative energy signals. The second converter device converts the alternative energy signals into electrical output signals. The partial discharge measuring instrument reads the electrical output signal and measures the partial discharge from the power cable. Methods for detecting partial discharge on an energized power cable are also described.

Claims

1. A partial discharge detection test link for detecting partial discharge of a power cable at a power cable accessory including a first accessory component and a second accessory component connected to each other, the partial discharge detection test link comprising:

a conductor member including an electrically conductive element and an insulation surrounding and extending along the electrically conductive element, the electrically conductive element having a pair of opposite ends with a respective one of ends adapted for electrical connection to a respective one of the first and second accessory components; and

a partial discharge sensor disposed about the conductor member, the partial discharge sensor having a primary winding in a form of the electrically conductive element and a secondary winding with the insulation positioned between the primary winding and the secondary winding.

2. A partial discharge detection test link according to claim 1, further comprising an electrically conductive cable lead operably connected to and extending from the partial discharge sensor.

3. A partial discharge detection test link according to claim 1, wherein at least one end projects from the insulation.

4. A partial discharge detection test link according to claim 3, wherein at least one end includes an electrically conductive connector.

5. A partial discharge detection test link according to claim 1, wherein the electrically conductive element is fabricated from a flexible cable material.

6. A partial discharge detection test link according to claim 1, wherein the electrically conductive element is a bonding lead.

7. A partial discharge detection test link according to claim 1, wherein the partial discharge sensor is a radio frequency current transformer.

8. A partial discharge detection test link according to claim 7, wherein the radio frequency current transformer is one of a ferrite-cored construction, an air-cored construction and a rogowski-coil construction.

9. A partial discharge detection test link according to claim 7, wherein the radio frequency current transformer is an isolation type.

10. A partial discharge detection test link according to claim 7, wherein the radio frequency current transformer is operative to sense electromagnetic pulses emanating at a rapid rate from the power cable while the conductor member tolerates substantial power frequency currents flowing through the electrically conductive element.

11. A partial discharge detection test link according to claim 10, wherein the radio frequency current transformer is optimized to yield high sensitivity to the electromagnetic pulses emanating at the rapid rate.

12. A partial discharge detection test link according to claim 1, wherein the secondary winding is electrically isolated from the electrically conductive element.

13. A partial discharge detection test link according to claim 1, wherein the partial discharge sensor is connected to the conductor member.

14. A partial discharge detection test link according to claim 1, further comprising a current transformer disposed about the conductor member and operative to sense power frequency flowing in the conductor member.

15. A partial discharge detection test link according to claim 14, wherein the current transformer is connected to the conductor member.

16. A partial discharge detection test link according to claim 1, wherein the conductor member is connected directly across the accessory.

17. A partial discharge detection test link according to claim 1, wherein the insulation has a thickness and the electrically conductive element has a diameter whereby the thickness of the insulation is at least one half of the diameter of the electrically conductive element.

18. A partial discharge detection test link according to claim 1, wherein the power cable accessory is one of a cable termination and a pair of bonding lead clamps.

19. A partial discharge detection test link according to claim 1, further comprising a ground cable electrically connected to the electrically conductive element.

20. A partial discharge detection test link according to claim 1, further comprising an electrically insulative connector element sized and adapted to connect the first accessory component and the second accessory component together while electrically insulating the first accessory component and the second accessory component from one another.

21. A partial discharge detection system for detecting partial discharge of a power cable at a power cable accessory including a first accessory component and a second accessory component connected to each other, the partial discharge detection system comprising:

a conductor member including an electrically conductive element and an insulation surrounding and extending along the electrically conductive element, the electrically conductive element having a pair of opposite ends with a respective one of ends adapted for electrical connection to a respective one of the first and second accessory components;

a partial discharge sensor disposed about the conductor member and operative to detect the partial discharge of the power cable as partial discharge electrical signals;

a first converter device electrically connected to the partial discharge sensor and operative for receiving the partial discharge electrical signals from the partial discharge sensor and converting the partial discharge electrical signals to alternative energy signals representative of the partial discharge electrical signals;

a second converter device in communication with the first converter device and operative for receiving the alternative energy signals and converting the alternative energy signals to electrical output signals representative of the alternative energy signals; and

a partial discharge measuring instrument coupled to the second converter device and operative to read the electrical output signals and measure the partial discharge from the power cable.

22. A partial discharge detection system according to claim 21, wherein the alternative energy signals are one of optical signals and radio frequency signals.

23. A partial discharge detection system according to claim 22, wherein when the alternative energy signals are optical signals, the first converter device is an optical encoding transmitter and the second converter device is an optical decoding receiver and when the alternative energy signals are radio frequency signals, the first converter device is a radio frequency transmitter and the second converter device is a radio frequency receiver.

24. A partial discharge detection system according to claim 21, further comprising a current transformer disposed about the conductor member and operative to sense power frequency current flowing in the conductor member.

25. A partial discharge detection system according to claim 24, wherein the current transformer generates a power frequency current signal used in conjunction with the partial discharge measuring instrument for synchronizing the partial discharge measuring instrument with voltage frequency and voltage phase of voltage in the power cable when energized.

26. A partial discharge detection system according to claim 21, further comprising an electrically insulative connector element sized and adapted to connect the first accessory component and the second accessory component together while electrically insulating the first accessory component and the second accessory component from one another.

27. A method for detecting partial discharge on an energized power cable having an accessory interposed therein, the accessory including a first accessory component and a second accessory component coupled to each other and connected by a service link, the method comprising the steps of:

providing a test link;

removing the service link;

replacing the service link with the test link by directly electrically connecting the first accessory component and the second accessory component together using the test link thereby providing electrical communication between the first and second accessory components through the test link;

detecting the partial discharge of the energized power cable at the test link by generating partial discharge electrical signals representative of the detected partial discharge; and

interpreting the partial discharge electrical signals in a manner to measure the partial discharge of the energized power cable.

28. A method according to claim 27, further comprising the steps of detecting power frequency current of the energized power cable at the test link as frequency current signals and synchronizing the measured partial discharge of the energized power cable with voltage frequency and voltage phase of voltage in the energized power cable determined from the step of detecting power frequency current of the energized power cable.

29. A method for detecting partial discharge on a plurality of energized power cables with each energized power cable interconnected by an accessory having a first accessory component and a second accessory component coupled to each other and connected by a service link, the plurality of energized power cables disposed apart from one another in a juxtaposed relationship and positioned in an enclosure defined by an arrangement of walls, the method comprising the steps of:

providing at least one electrically insulative barrier and a plurality of test links;

replacing the service links with test links by directly electrically connecting the respective ones of the first accessory components and the second accessory components to each other using respective ones of the plurality of test links thereby providing direct electrical communication between the respective ones of the connected first and second accessory components;

positioning the at least one electrically insulative barrier between juxtaposed ones of the plurality of energized power cables so that flashover is inhibited;

detecting partial discharge of the plurality of energized power cables at respective ones of the test links by generating partial discharge electrical signals representative of the detected partial discharge of the respective energized power cables;

converting the partial discharge electrical signals adjacent the enclosure to alternative energy signals representative of the partial discharge electrical signals;

transmitting the alternative energy signals to a location remote from the enclosure; and

interpreting the alternative energy signals at the remote location in a manner to measure the partial discharge of the respective energized power cables.

30. A method according to claim 29, further comprising the step of detecting power frequency current of each of the energized power cables at the respective test links as frequency current signals.

31. A method according to claim 30, further comprising the step of transmitting the frequency current signals to the remote location for synchronizing the measured partial discharge of the respective energized power cables with voltage frequency and voltage phase of voltage in the respective energized power cables.

32. A method according to claim 29, wherein the interpreting step includes converting the alternative energy signals to electrical output signals and reading the electrical output signals to measure the partial discharge of the respective energized power cables.

33. A method according to claim 29, further comprising the step of placing at least another one of the electrically insulating barriers between a selected one of the energized power cables and a selected one of the walls to further inhibit flashover.