Partial discharge detection test link, partial discharge detection system and methods for detecting partial discharge on a power cable
A partial discharge detection test link and system is disclosed to detect partial discharge of a power cable accessory. The power cable accessory includes a first accessory component and a second accessory component connected to each other. The partial discharge detection test link is a permanent or temporary substitute for a conventional service link, connects directly across the power cable accessory and includes a conductor member and a partial discharge sensor. The conductor member has an electrically conductive element and an insulation surrounding and extending along the electrically conductive element. The electrically conductive element is electrically connected directly between the first and second accessory components. The partial discharge sensor is disposed about the conductor member and has the electrically conductive element as a primary winding and a secondary winding with the insulation positioned between the primary and secondary windings.
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.