Time-domain differential line protection of electric power delivery systems

• US 10,310,004 B2
• Filed: 09/16/2016
• Issued: 06/04/2019
• Est. Priority Date: 09/18/2015
• Status: Active Grant

• Current Assignee: Schweitzer Engineering Laboratories, Incorporated
• Original Assignee: Schweitzer Engineering Laboratories, Incorporated
• Inventors: Schweitzer, III, Edmund O., Mynam, Mangapathirao Venkata, Whitehead, David E., Kasztenny, Bogdan Z., Guzman-Casillas, Armando, Skendzic, Veselin
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): Pretlow, Demetrius R
• Application Number:
  US15/269,904
• Publication Number:
  US 20180212421A1
• Time in Patent Office: 991 Days
• Field of Search: 324637-646, 324500
• CPC Class Codes: G01R 31/085 in power transmission or distribution lines, e.g. overhead
• CPC Class Codes: G01R 31/11 using pulse reflection methods
• CPC Class Codes: H02H 1/0007 concerning the detecting means in general G01R or other subclasses of G01; reed switches H01H71/2445
• CPC Class Codes: H02H 1/0092 concerning the data processing means, e.g. expert systems, neural networks
• CPC Class Codes: H02H 3/083 for three-phase systems
• CPC Class Codes: H02H 7/263 involving transmissions of measured values comparison of currents or voltages using pilot wires H02H3/30
• CPC Class Codes: H02H 7/265 making use of travelling wave theory

Abstract

The present disclosure relates to detection of faults in an electric power system. In one embodiment, a time-domain traveling wave differential subsystem is configured to determine at a first terminal a first index between an arrival maximum of a traveling wave generated by a fault at the first terminal and an exit maximum of the traveling wave. The traveling wave subsystem also determines a second index between an arrival maximum of the traveling wave at the second terminal and an exit maximum of the traveling wave. An operating quantity and a restraint quantity may be determined based on a magnitude of the representations of electrical conditions in the first index and the second index. A fault may be declared based on a comparison of the operating quantity and the restraint quantity. A protective action subsystem may be configured to implement a protective action based on the declaration of the fault.

Claims

1. A system configured to detect a fault in a power line of an electric power delivery system, comprising:

a data acquisition subsystem in electrical communication with the power line of the electric power delivery system, configured to acquire a plurality of time-domain representations of electrical conditions at a plurality of index values in the electric power delivery system at each of a first terminal of the power line and a second terminal of the power line;

a time-domain traveling wave differential subsystem configured to determine;

a first maximum of a traveling wave generated by a fault at the first terminal and at a first index value based on the plurality of time-domain representations of electrical conditions;

a second maximum of the traveling wave at the second terminal and at a second index value based on the plurality of time-domain representations of electrical conditions;

a first exit window at the first terminal based on the second maximum, a propagation time between the first and second terminal and a variability margin;

a second exit window at the second terminal based on the first maximum, the propagation time between the first and second terminal and the variability margin;

a third maximum within the first exit window at a third time;

a fourth maximum within the second exit window at a fourth time;

a first index duration based on the first time and the third time;

a second index duration based on the second time and the fourth time;

an operating quantity based on a magnitude of the representations of electrical conditions in the first index and the second index;

a restraint quantity based on the magnitude of the representations of electrical conditions in the first index and the second index; and

,

a fault detector subsystem configured to declare a fault based on a comparison of the operating quantity and the restraint quantity; and

a protective action subsystem configured to implement a protective action on the electric power delivery system based on the declaration of the fault.

2. The system of claim 1, wherein the operating quantity is based on a summation of the magnitudes of the values in the first index and the second index.

3. The system of claim 1, wherein the restraint quantity is based on a summation of the magnitudes of the values in the first index and the second index.

4. The system of claim 1, wherein the data acquisition subsystem further comprises a differentiator smoother, and wherein the first index and the second index are processed by the differentiator smoother.

5. The system of claim 1, wherein the differential subsystem is further configured to determine a fault location.

6. The system of claim 1, wherein the fault detector subsystem further declares the fault based on a minimum pickup value.

7. The system of claim 6, wherein the minimum pickup value varies based on the fault location.

8. The system of claim 1, wherein the system is configured to monitor each phase of a three-phase power system and to identify the fault on at least one phase of the three-phase power system.

9. The system of claim 1, wherein the fault detector subsystem is further configured to declare the fault based on the existence of an overcurrent condition.

10. The system of claim 9, wherein the electric power delivery system comprises a multi-phase system, and the fault detector subsystem is further configured to declare the fault based on the existence of the overcurrent condition and the traveling wave on a phase of the multi-phase electric power system.

11. The system of claim 1, wherein the variability margin is selected to compensate for at least one of a measurement error, a time synchronization error, and a sag in an electrical transmission line.

12. A method for detecting a fault in an electric power delivery system, comprising:

acquiring a plurality of time-domain representations of electrical conditions at a plurality of index values in the electric power delivery system at each of a first terminal and a second terminal;

detecting a first maximum of a traveling wave generated by a fault at the first terminal and at a first index value based on the plurality of time-domain representations of electrical conditions;

detecting a second maximum of the traveling wave at the second terminal and at a second index value based on the plurality of time-domain representations of electrical conditions;

determining a first exit window at the first terminal based on the second maximum, a propagation time between the first and second terminal and a variability margin;

determining a second exit window at the second terminal based on the first maximum, the propagation time between the first and second terminal and the variability margin;

determining a third maximum within the first exit window at a third time;

determining a fourth maximum within the second exit window at a fourth time;

determining a first index duration based on the first time and the third time;

determining a second index duration based on the second time and the fourth time;

determining an operating quantity based on the representations of electrical conditions in the first index and the second index;

determining a restraint quantity based on the representations of electrical conditions in the first index and the second index; and

,

declaring a fault based on a comparison of the operating quantity and the restraint quantity; and

implementing a protective action based on the declaration of the fault.

13. The method of claim 12, wherein determining the operating quantity comprises summing the magnitudes of the values in the first index and the second index.

14. The method of claim 12, wherein determining the restraint quantity comprises summing the magnitudes of the values in the first index and the second index.

15. The method of claim 12, wherein the time-domain traveling wave differential subsystem further comprises a differentiator smoother, and wherein the first index and the second index are processed by the differentiator smoother.

16. The method of claim 12, further comprising determining a fault location.

17. The method of claim 16, wherein the fault detector subsystem further declares the fault based on a minimum pickup value.

18. The method of claim 17, wherein the minimum pickup value varies based on the fault location.

19. The method of claim 12, declaring the fault further comprises detecting an overcurrent condition.

20. The method of claim 12, further comprising selecting the variability margin to compensate for at least one of a measurement error, a time synchronization error, and a sag in an electrical transmission line.