High-impedance differential protection using a diversity of signals

Patent metadata

Field	Value
Publication number	US-12418168-B2
Application number	US-202418419092-A
Country	US
Kind code	B2
Filing date	Jan 22, 2024
Priority date	Jan 25, 2023
Publication date	Sep 16, 2025
Grant date	Sep 16, 2025

Abstract

A system for high-impedance differential protection for power systems using a variety of signals from the power system. A fault may be detected using filtered phase current or filtered phase voltage magnitudes from current transformers (CTs) connected in parallel by phase. A fault may be detected using filtered phase voltages and raw phase voltages from the CTs. A fault may be detected using raw phase currents and raw phase voltages from the CTs. A fault may be detected using filtered phase currents and raw phase currents. A fault may be detected using raw phase currents and raw neutral currents. The embodiments herein maintain dependability and security of a differential element even when low-class CTs are used. The embodiments herein may allow users to optimize pickup settings even when low-class CTs are used.

First claim

What is claimed:

1. A protective device for use in an electric power system, the protective device comprising:
a first input configured to receive a first signal from a transformer in electrical communication with a first portion of the electric power system, and to generate a first raw signal representative of a first electrical condition in the first portion of the electric power system;
a second input configured to receive a second signal from a second transformer in electrical communication with a second portion of the electric power system, and to generate a second raw signal representative of a second electrical condition in the second portion of the electric power system; and
a logic subsystem configured to:
compare the first raw signal to a first threshold;
compare the second raw signal to a second threshold;
generate a count representing samples when the first raw signal is outside the first threshold and when the second raw signal is outside the second threshold; and
generate a protective action signal based on the count.

2. The protective device of claim 1 , wherein the protective device is configured to operate with transformers of a class rating of 50 or higher.

3. The protective device of claim 1 , wherein the first signal represents a current and the second signal represents a voltage.

4. The protective device of claim 3 , wherein the first signal comprises a summation of currents in a single phase in the electric power system.

5. The protective device of claim 1 , wherein the first signal comprises a summation of currents from a plurality of current transformers in a single phase in the electric power system and the second signal comprises a current.

6. The protective device of claim 5 , wherein the second signal comprises a summation of currents from a plurality of current transformers in all phases in the electric power system.

7. The protective device of claim 1 , wherein the protective device provides differential protection to at least a portion of the electric power system.

8. The protective device of claim 1 , further comprising a high-impedance module in electrical communication with the first input and the second input; and wherein the high-impedance module is disposed between the transformer and the and the first input and the second input.

9. The protective device of claim 1 , wherein use of the first input and the second input improve security against a single event upset.

10. The protective device of claim 1 , further comprising a first buffer to store approximately one cycle of samples representing the count of samples in which the first raw signal is outside the first threshold or the second raw signal is outside the second threshold.

11. The protective device of claim 10 , further comprising a second buffer in communication with the first buffer, and configured to store a count of a number of samples in the first buffer that satisfy a criteria;
wherein the logic subsystem is further configured to assert the protective action signal when the count exceeds a first number.

12. The protective device of claim 11 , further comprising a third buffer to store approximately one cycle of samples representing the count of samples in which the second raw signal is outside the second threshold.

13. The protective device of claim 12 , further comprising a fourth buffer in communication with the third buffer, and configured to store a count of a number samples in the third buffer that satisfy a criteria;
wherein the logic subsystem is further configured to assert the protective action signal when the count exceeds a second number.

14. The protective device of claim 13 , wherein the second number is greater than the first number.

15. The protective device of claim 14 , wherein the fourth buffer is configured to update approximately each quarter cycle of the electric power system.

16. A method of using a protective device in an electric power system, the method comprising:
receiving, using a first input, a first signal from a transformer in electrical communication with a first portion of the electric power system, the first transformer generating a first raw signal representative of a first electrical condition in the first portion of the electric power system;
receiving, using a second input, a second signal from a second transformer in electrical communication with a second portion of the electric power system, the second transformer generating a second raw signal representative of a second electrical condition in the second portion of the electric power system;
comparing, using a logic subsystem,
the first raw signal to a first threshold, and
the second raw signal to a second threshold;

generating, using the logic subsystem, a count representing samples when the first raw signal is outside the first threshold and when the second raw signal is outside the second threshold; and
generating, using the logic subsystem, a protective action signal based on the count.

17. The method of claim 16 , wherein the protective device is configured to operate with transformers of a class rating of 50 or higher.

18. The method of claim 16 , wherein the first signal represents a phase current and the second signal represents a voltage.

19. The method of claim 16 , wherein the first signal represents a current and the second signal represents a voltage.

20. The method of claim 16 , further comprising providing a high-impedance module in electrical communication with the first input and the second input; and wherein the high-impedance module is disposed between the transformer and the first input and the second input.

Assignees

• Schweitzer Engineering Lab Inc

Inventors

• Fischer Normann
• Dissanayake Anushka M
• Hartshorn Jay
• Donolo Marcos A

Classifications

• H02H1/0007

  concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445) · CPC title

• H02H7/042 Primary

  for current transformers · CPC title

• H02H7/22

  for distribution gear, e.g. bus-bar systems; for switching devices {(detecting mechanical or electrical defects in gas-insulated switchgears H02B13/065)} · CPC title

• H02H3/283

  and taking into account saturation of current transformers · CPC title

• H02H7/045 Primary

  Differential protection of transformers · CPC title