Systems and methods for generator ground fault protection

• US 8,405,940 B2
• Filed: 10/12/2010
• Issued: 03/26/2013
• Est. Priority Date: 10/13/2009
• Status: Active Grant

• Current Assignee: Schweitzer Engineering Laboratories, Incorporated
• Original Assignee: Schweitzer Engineering Laboratories, Incorporated
• Inventors: Schweitzer, Edmund O. III, Skendzic, Veselin, Benmouyal, Gabriel, Hall, Bruce A., Scharlach, Rogerio
• Primary Examiner(s): Leja, Ronald W
• Application Number:
  US12/903,104
• Publication Number:
  US 20110085272A1
• Time in Patent Office: 896 Days
• Field of Search: 361/42
• US Class Current: 361/42
• CPC Class Codes: H02H 3/17 by means of an auxiliary voltage injected into the installation to be protected using summation current transformers H02H3/33
• CPC Class Codes: H02H 7/06 for dynamo-electric generators; for synchronous capacitors

Abstract

A generator winding-to-ground fault detection system is disclosed that includes a signal injection source in electrical communication with a winding of an electric power generator via an injection transformer. The winding may be coupled to ground via a winding-to-ground path and the signal generation source may generate an injection signal capable of being injected to the winding using the injection transformer. The disclosed system may further include a protection module in communication with the signal injection source and the electric power generator configured to receive the injection signal and a signal relating to the current through the winding-to-ground path, and to determine the occurrence of a winding-to-ground fault condition based at least in part on the injection signal and the signal relating to the current through the winding-to-ground path.

Claims

1. A generator winding-to-ground fault detection system, comprising:

a first signal injection source in electrical communication with a first winding of a first electric power generator via a first injection transformer, the first signal injection source comprising a first signal generator for generating a first injection signal capable of being injected to the first winding using the first injection transformer, the first winding being coupled to ground via a first path; and

a protection module in communication with the first signal injection source and the first electric power generator, the protection module configured to receive the first injection signal and a signal relating to the current through the first path and to determine the occurrence of a winding-to-ground fault condition based at least in part on the first injection signal and the signal relating to the current through the first path,

wherein the first injection signal is configured to enable the protection module to differentiate the first injection signal from signals resulting from normal operation of the first electric power generator.

2. The system of claim 1, wherein the first injection source is a variable waveform source.

3. The system of claim 1, wherein the first injection signal comprises a random signal.

4. The system of claim 1, wherein the first injection signal comprises a multisine signal.

5. The system of claim 4, wherein the multisine signal comprises a select subset of frequencies.

6. The system of claim 5, wherein the select subset of frequencies comprises frequencies that are not harmonically related to a nominal operating frequency of the generator.

7. The system of claim 4, wherein the multisine signal is a Schroeder multisine signal.

8. The system of claim 1, wherein the first injection signal comprises multiple frequencies.

9. The system of claim 1, wherein the protection module is configured to take action to protect the electric power generator from damage when the occurrence of a winding-to-ground fault condition is detected.

10. The system of claim 1, wherein:

the first signal injection source is in electrical communication with a second winding of a second electric power generator via a second injection transformer,

the first signal generator of the first signal injection source is configured to generate a second injection signal capable of being injected to the second winding using the second injection transformer, the second winding being coupled to ground via a second path, and

the protection module is in communication with the second electric power generator and is configured to receive the second injection signal and a signal relating to the current through the second path and to determine the occurrence of a winding-to-ground fault condition based at least in part on the second injection signal and the signal relating to the current through the second path.

11. The system of claim 10, wherein the protection module is further configured to determine which of the first and second windings are experiencing a winding-to-ground fault condition.

12. The system of claim 1, further comprising:

a second signal injection source in electrical communication with a second winding of a second electric power generator via a second injection transformer, the second signal injection source comprising a second signal generator configured to generate a second injection signal capable of being injected to the second winding using the second injection transformer, the second winding being coupled to ground via a second path,

wherein the protection module is in communication with the second electric power generator and is configured to receive the second injection signal and a signal relating to the current through the second path and to determine the occurrence of a winding-to-ground fault condition based at least in part on the second injection signal and the signal relating to the current through the second path, and

wherein the first and second electric power generators are connected to a transformer in parallel.

13. The system of claim 12, wherein the system further comprises a communications port and a processor in communication with the communications port, wherein the protection module and a communications module is executed by the processor.

14. The system of claim 12, wherein the first injection signal is different from the second injection signal.

15. The method of claim 14, wherein the injection signal comprises multiple frequencies.

16. The method of claim 14, wherein the detecting a winding-to-ground fault condition includes measuring the impedance of the winding-to-ground path.

17. The method of claim 14, wherein the method further comprises taking action to protect the electric power generator from damage when the occurrence of a winding-to-ground fault condition is detected.

18. A method for detecting winding-to-ground faults in a generator comprising:

injecting, by a signal injection source comprising a signal generator in electrical communication with a winding of a electric power generator via an injection transformer, an injection signal to the winding using the injection transformer, the winding being coupled to ground via a winding-to-ground path; and

detecting, by a protection module in communication with the signal injection source and the electric power generator, the occurrence of a winding-to-ground fault condition based at least in part on the injection signal and a signal relating to the current through the winding-to-ground path,

wherein the injection signal is generated to enable the protection module to differentiate the injection signal from signals resulting from the normal operation of the electric power generator, and wherein the protection module receives the injection signal.

19. The method of claim 18, wherein the injection source is a variable waveform source.

20. The method of claim 18, wherein the injection signal comprises a noise-like signal.

21. The method of claim 18, wherein the injection signal comprises a multisine signal.

22. The method of claim 21, wherein the multisine signal comprises a select subset of frequencies.

23. The method of claim 22, wherein the select subset of frequencies comprises frequencies that are not harmonically related to a nominal operating frequency of the generator.

24. The method of claim 22, wherein the multisine signal is a Schroeder multisine signal.

25. The method of claim 24, wherein the protection module is configured to detect a winding-to-ground fault condition using the multiple frequencies.

26. An intelligent electronic device, comprising:

an injection output configured to be couple to a winding of a generator;

a processor;

a computer readable storage medium, comprising;

a signal injection module executable on the processor and configured to generate an injection signal capable of being injected to the winding of the generator via the injection output, the winding being coupled to ground via a path; and

a protection module executable on the processor and configured to receive the injection signal and a signal relating to the current through the path and configured to determine the occurrence of a winding-to-ground fault condition based at least in part on the injection signal and the signal relating to the current through the path.