Detection of cross-country faults

Patent metadata

Field	Value
Publication number	US-10474142-B2
Application number	US-201715718145-A
Country	US
Kind code	B2
Filing date	Sep 28, 2017
Priority date	Sep 28, 2017
Publication date	Nov 12, 2019
Grant date	Nov 12, 2019

Abstract

Disclosed herein are a variety of systems and methods related to detection of a cross-country fault in an electrical power system. In one embodiment, a system consistent with the present disclosure may be configured to monitor electrical parameters in the electrical power system. The system may determine when a voltage magnitude of one phase exceeds a first voltage threshold. The one phase that exceeds the first voltage threshold may be identified as an un-faulted phase. The system may further be configured to determine that the voltage magnitude of the un-faulted phase exceeds a second threshold based on a zero-sequence voltage. The system may further be configured to determine that a phase angle between the un-faulted phase and the zero-sequence voltage is within a range. A protective action to clear the cross-country fault condition may be implemented upon identification of a cross-country fault.

First claim

What is claimed is:

1. A system configured to detect a cross-country fault in an electric power system, comprising:
a data acquisition subsystem configured to receive a plurality of representations of electrical conditions associated with at least a portion of the electric power system;
a magnitude and angle subsystem configured to:
identify a first condition comprising a voltage magnitude of one phase exceeding a first voltage threshold based on the plurality of representations of electrical conditions;
identify the one phase that exceeds the first voltage threshold as an un-faulted phase;
identify a second condition comprising the voltage magnitude of the un-faulted phase exceeding a second threshold based on a zero-sequence voltage based on the plurality of representations of electrical conditions;
identify a third condition comprising a phase angle between the un-faulted phase and the zero-sequence voltage being within a range based on the plurality of representations of electrical conditions;

a fault determination module configured to:
identify a cross-country fault condition based on identification of the first condition, the second condition, and the third condition by the magnitude and angle subsystem;
annunciate the cross-country fault condition;

a protective action module configured to implement a protective action to clear the cross-country fault condition.

2. The system of claim 1 , wherein the magnitude and angle subsystem is further configured to determine that the zero-sequence voltage exceeds a nominal threshold.

3. The system of claim 2 , wherein the magnitude and angle subsystem is further configured to:
determine that the zero-sequence voltage has exceeded the nominal threshold for a delay period; and
assert a ground fault alarm condition after the delay.

4. The system of claim 3 , wherein the magnitude and angle subsystem is further configured to:
determine that the zero-sequence voltage has fallen below the nominal threshold for a reset period; and
de-assert the ground fault alarm condition after the reset period.

5. The system of claim 1 , wherein the protective action module is further configured to block a single-phase-to-ground protective action based on identification of the cross-country fault condition.

6. The system of claim 1 , further comprising a settings subsystem configured to receive a first user-provided value and to calculate the second threshold based on and a maximum value of the zero-sequence voltage.

7. The system of claim 1 , further comprising a settings subsystem configured to receive a second user-provided value and to calculate the range.

8. The system of claim 1 , wherein the electrical power system is ungrounded.

9. The system of claim 1 , further comprising a monitored equipment interface configured to issue the control instruction to monitored equipment.

10. The system of claim 1 , further comprising a communications interface configured to annunciate the cross-country fault.

11. The system of claim 10 , wherein the communications interface is configured to annunciate the cross-country fault condition to a Supervisory control and data acquisition.

12. A method for detecting a cross-country fault in a multi-phase electrical power system, the method comprising:
identifying a first condition comprising a voltage magnitude of one phase exceeding a first voltage threshold based on the plurality of representations of electrical conditions;
identifying the one phase that exceeds the first voltage threshold as an un-faulted phase;
identifying a second condition comprising the voltage magnitude of the un-faulted phase exceeding a second threshold based on a zero-sequence voltage based on the plurality of representations of electrical conditions;
identifying a third condition comprising a phase angle between the un-faulted phase and the zero-sequence voltage being within a range based on the plurality of representations of electrical conditions;
identifying a cross-country fault condition based on identification of the first condition, the second condition, and the third condition by the magnitude and angle subsystem;
annunciating the cross-country fault condition;
implementing a protective action to clear the cross-country fault condition.

13. The method of claim 12 , further comprising:
determining that the zero-sequence voltage exceeds a nominal threshold.

14. The method of claim 12 , further comprising:
determining that the zero-sequence voltage has exceeded the nominal threshold for a delay period; and
asserting a ground fault alarm condition after the delay.

15. The method of claim 14 , further comprising:
determining that the zero-sequence voltage has fallen below the nominal threshold for a reset period; and
de-asserting the ground fault alarm condition after the reset period.

16. The method of claim 12 , further comprising:
blocking a single-phase-to-ground protective action based on identification of the cross-country fault condition.

17. The method of claim 12 , further comprising:
calculating the second threshold based on a first user-provided value and a maximum value of the zero-sequence voltage.

18. The method of claim 12 , wherein the range is determined based on a second user-provided value.

19. The method of claim 12 , wherein the electrical power system is ungrounded.

20. The method of claim 12 , wherein annunciating a cross-country fault condition comprises one of communicating the condition and logging the condition in an event report.

Assignees

• Schweitzer Engineering Lab Inc

Inventors

• Haes Dennis
• Fischer Normann

Classifications

• H02H7/26

  Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured (locating faults in cables G01R31/08) · CPC title

• H02H3/347

  using summation current transformers · CPC title

• H02H3/353

  involving comparison of phase voltages · CPC title

• H02H3/042

  combined with means for locating the fault (locating faults in cables G01R31/08) · CPC title

• G01R19/2513

  Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging · CPC title