Protective relay device, system and methods for Rogowski coil sensors

• US 20070236208A1
• Filed: 04/07/2006
• Published: 10/11/2007
• Est. Priority Date: 04/07/2006
• Status: Active Grant

• Current Assignee: Eaton Intelligent Power Limited (Eaton Corporation PLC.)
• Original Assignee: Cooper Technologies Company (Eaton Corporation PLC.)
• Inventors: Williams, Stephen, Kojovic, Ljubomir
• Granted Patent: US 7,638,999 B2
• Time in Patent Office: Days
• US Class Current: 324/127
• CPC Class Codes: G01R 15/181 using coils without a magnetic core, e.g. Rogowski coils
• CPC Class Codes: H02H 1/0007 concerning the detecting means in general G01R or other subclasses of G01; reed switches H01H71/2445

Abstract

Relay devices, systems and methods for obtaining an accurate representation of a current monitored with a Rogowski coil, without integration of the Rogowski coil output voltage signal in the time domain.

Claims

1. A protective system for a current path in in an electrical power system, the system comprising:

a Rogowski coil generating an output voltage signal corresponding to current flow in the current path; and

a microprocessor based protection device receiving the output voltage signal, the microprocessor based protection device being responsive to the output voltage signal to cause the current path to be interrupted when a fault condition is detected, wherein the fault condition is detected without integration of the output voltage signal in the time domain.

2. The system of claim 1, wherein the voltage output signal is processed in the frequency domain.

3. The system of claim 1, wherein the phase of voltage output signal is digitally shifted by approximately 90 degrees.

4. The system of claim 3, wherein the voltage output signal is multiplied by a scalar.

5. The system of claim 1, wherein the microprocessor based device comprises a digital relay device, the relay device configured to detect the fault condition.

6. The system of claim 1, further comprising a second microprocessor based device separately provided from the protective device, the second microprocessor based device configured to detect the fault condition.

7. The system of claim 1, further comprising a second microprocessor based device separately provided from the protective device, the second device configured to integrate the voltage output signal to extract power analysis information.

8. The system of claim 1, further comprising a circuit protector operatively connected to the protective device, the protective device causing the circuit protector to open the current path in response to the output voltage signal.

9. A protective relay system for a current path in an electrical system, the system comprising:

a Rogowski coil generating an output voltage signal proportional to a time derivative of a current flow in the current path; and

a microprocessor based relay device receiving a non-integrated output voltage signal of the Rogowski coil, the relay device causing the current path to be interrupted when a fault condition is detected using the non-integrated output voltage signal.

10. The system of claim 9, wherein the fault condition is detected without integration of the output voltage signal in the time domain.

11. The system of claim 9, wherein the voltage output signal is processed in the frequency domain.

12. The system of claim 9, wherein the phase of the non-integrated voltage output signal is digitally shifted by approximately 90 degrees.

13. The system of claim 12, wherein the voltage output signal is multiplied by a scalar.

14. The system of claim 9, wherein the relay comprises a microprocessor and a memory, the microprocessor and memory configured to detect the fault condition.

15. The system of claim 9, further comprising a second microprocessor based device separately provided from the relay device, and wherein the second microprocessor based device processes the non-integrated output voltage signal.

16. The system of claim 9, further comprising a circuit protector operatively connected to the relay device, the relay device causing the circuit protector to open the current path in response to the output voltage signal.

17. A protective relay system for managing an electrical system, the system comprising:

a conductor defining a current path in the electrical system;

a Rogowski coil receiving the conductor and generating an analog output voltage signal proportional to a time derivative of current flow in the current path; and

a digital relay device receiving the analog output voltage signal, the relay device configured to digitize the signal and process the signal in the frequency domain to represent the current flow without integration of the output voltage signal in the time domain, the relay device causing the current path to be interrupted when a fault condition is detected using the represented current flow.

18. The system of claim 17, wherein the phase of the non-integrated voltage output signal is digitally shifted by approximately 90 degrees.

19. The system of claim 17, wherein the voltage output signal is multiplied by a scalar.

20. The system of claim 17, wherein the relay comprises a microprocessor and a memory, the microprocessor and memory configured to detect the fault condition.

21. The system of claim 17, further comprising a circuit protector operatively connected to the relay device, the relay device causing the circuit protector to open the current path in response to the output voltage signal.

22. A digital relay device responsive to an output voltage signal of a Rogowski coil, the relay device comprising:

a processor; and

a memory, wherein the processor and memory are configured to execute a control algorithm whereby the output voltage signal is processed in the frequency domain without integration of the output voltage signal in the time domain to determine a current signal corresponding to the output voltage signal.

23. The digital relay device of claim 22, wherein the processor and memory are further configured to detect a fault condition using the determined current signal.

24. The digital relay device of claim 22, further comprising a circuit protector, the relay causing the circuit protector to open a circuit path when the fault condition is detected.

25. The digital relay device of claim 22, wherein the output voltage signal is multiplied by a scalar to determine the current signal.

26. The digital relay device of claim 22, wherein the phase of the output voltage signal is digitally shifted to determine the current signal.

27. The digital relay device of claim 22, wherein the output voltage of the Rogowski coil is an analog signal, the relay comprising an analog to digital converter to digitize the output voltage signal.

28. A method of processing an output voltage signal of a Rogowski coil for control of a current path with a protective relay device, the method comprising:

obtaining the output voltage signal;

digitizing the output signal; and

determining a current signal corresponding the output voltage signal without integration of the output voltage signal in the time domain.

29. The method of claim 28, wherein determining the current signal comprises applying a discrete transform algorithm to the digitized output signal.

30. The method of claim 28, wherein determining the current signal comprises digitally shifting the phase of the digitized output signal.

31. The method of claim 28, wherein determining the current signal comprises multiplying the digitized signal by a scalar.

32. The method of claim 28, further comprising comparing the determined signal to a predetermined fault current signal, and detecting a fault condition based upon the compared determined signal and fault current signal.

33. The method of claim 29, further comprising causing a circuit protector to interrupt a current path extending through the Rogowski coil.

34. The method of claim 29, further comprising:

storing in the relay device data relating to the determined current over time;

extracting the data from the relay device; and

integrating the extracted data with a microprocessor based device separate from the relay device.

35. A protective system for an electrical network, comprising:

a Rogowski coil monitoring a current path in an electrical system; and

means for processing an output voltage signal of the Rogowski coil to provide a current signal corresponding to a time derivative of current flow in the current path, the means for processing providing the current signal while avoiding integration in the time domain of the output voltage signal.

36. The system of claim 35, wherein the means for processing comprises a digital relay device.

37. The system of claim 35, further comprising means for interrupting the current flow in the current path when the provided current signal corresponds to a fault condition.

38. The system of claim 35, further comprising means for storing data relating to the provided current signal over time, and means for extracting the stored data and analyzing the data.