Network protector control for spot network fed from feeder sources having voltage differences

Patent metadata

Field	Value
Publication number	US-10096991-B2
Application number	US-201615180638-A
Country	US
Kind code	B2
Filing date	Jun 13, 2016
Priority date	Jun 13, 2016
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

Abstract

In one embodiment, a network protector for a spot network includes a circuit breaker and a network protector relay coupled to the circuit breaker. The network protector relay is structured and configured to have network protector relay non-sensitive trip settings for controlling operation of the circuit breaker that will cause the network protector to remain closed when: (i) an angular difference (±) between a transformer phase-to-neutral voltage of the first feeder branch and a transformer phase-to-neutral voltage of the second feeder branch is less than or equal to a first threshold value, and (ii) a magnitude difference (±) between the transformer phase-to-neutral voltage of the feeder branch and the transformer phase-to-neutral voltage of the second feeder branch is less than or equal to a second threshold value.

First claim

What is claimed is:

1. A network protector for a spot network having a first feeder branch and a second feeder branch, comprising:
a circuit breaker; and
a network protector relay coupled to the circuit breaker, wherein the network protector relay is structured and configured to have network protector relay non-sensitive trip settings for controlling operation of the circuit breaker that will cause the network protector to remain closed when: (i) an angular difference (±) between a transformer phase-to-neutral voltage of the first feeder branch and a transformer phase-to-neutral voltage of the second feeder branch is less than or equal to a first threshold value, and (ii) a magnitude difference (±) between the transformer phase-to-neutral voltage of the first feeder branch and the transformer phase-to-neutral voltage of the second feeder branch is less than or equal to a second threshold value.

2. The network protector according to claim 1 , wherein the first threshold value is ±4 degrees and the second threshold value is ±3%.

3. The network protector according to claim 1 , wherein the network protector relay is structured and configured to have network protector relay close settings and characteristics that will cause the network protector to automatically reclose when: (i) the transformer phase-to-neutral voltage of the first feeder branch lags a network phase-to-neutral voltage of the first feeder branch by no more than a third threshold value, and (ii) a magnitude of the transformer phase-to-neutral voltage of the first feeder branch is lower than a magnitude of the network phase-to-neutral voltage of the first feeder branch by no more than a fourth threshold value.

4. The network protector according to claim 1 , wherein the network protector relay is structured and configured to detect backfeed due to a single line-to-ground (SLG) fault on the first feeder branch when a feeder circuit breaker in the first feeder branch is open based on a zero-sequence voltage of the first feeder branch.

5. The network protector according to claim 4 , wherein the zero-sequence voltage of the first feeder branch is determined using a circuit that is part of or separate from the network protector relay.

6. The network protector according to claim 4 , wherein the network protector relay is structured and configured to detect backfeed due to a single line-to-ground (SLG) fault on the first feeder branch when a feeder circuit breaker in the first feeder branch is open based on determining that a parameter proportional to the zero-sequence voltage of the first feeder branch exceeds a predetermined threshold for a predetermined amount of time.

7. The network protector according to claim 4 , wherein the network protector relay is structured and configured to detect that the feeder circuit breaker in the first feeder branch is open in the absence of a fault based on a capacitance of one or more power factor correction capacitors connected from one phase of the first feeder branch to ground.

8. A method of controlling a network protector for a spot network having a first feeder branch and a second feeder branch, the network protector including a circuit breaker and a network protector relay coupled to the circuit breaker, the method comprising:
controlling operation of the circuit breaker from the network protector relay based on network protector relay non-sensitive trip settings, wherein the controlling includes causing the network protector to remain closed when: (i) an angular difference (±) between a transformer phase-to-neutral voltage of the first feeder branch and a transformer phase-to-neutral voltage of the second feeder branch is less than or equal to a first threshold value, and (ii) a magnitude difference (±) between the transformer phase-to-neutral voltage of the first feeder branch and the transformer phase-to-neutral voltage of the second feeder branch is less than or equal to a second threshold value.

9. The method according to claim 8 , wherein the first threshold value is ±4 degrees and the second threshold value is ±3%.

10. The method according to claim 8 , further comprising controlling operation of the circuit breaker from the network protector relay based on network protector relay close settings and characteristics by causing the network protector to automatically reclose when: (i) the transformer phase-to-neutral voltage of the first feeder branch lags a network phase-to-neutral voltage of the first feeder branch by no more than a third threshold value, and (ii) a magnitude of the transformer phase-to-neutral voltage of the first feeder branch is lower than a magnitude of the network phase-to-neutral voltage of the first feeder branch by no more than a fourth threshold value.

11. The method according to claim 8 , further comprising detecting backfeed due to a single line-to-ground (SLG) fault on the first feeder branch when a feeder circuit breaker in the first feeder branch is open based on a zero-sequence voltage of the first feeder branch.

12. The method according to claim 11 , further comprising determining the zero-sequence voltage.

13. The method according to claim 11 , wherein the detecting backfeed comprises determining that a parameter proportional to the zero-sequence voltage of the first feeder branch exceeds a predetermined threshold for a predetermined amount of time.

14. The method according to claim 11 , further comprising detecting that the feeder circuit breaker in the first feeder branch is open in the absence of a fault based on a capacitance of one or more power factor correction capacitors connected from one phase of the first feeder branch to ground.

15. A network protector relay including a non-transitory computer readable medium encoded with a computer program comprising program code for implementing the method of claim 8 .

Assignees

• Cooper Technologies Co
• Eaton Intelligent Power Ltd

Inventors

• Smith David R
• Faulkner Marc Andre

Classifications

• H02H3/26 Primary

  responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents · CPC title

• G01R31/086

  in power transmission or distribution networks, i.e. with interconnected conductors · CPC title

• H02H1/0007

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

• H02H3/302

  involving phase comparison · CPC title

• H02H1/06

  Arrangements for supplying operative power {(power supply arrangements in general G05F, H02M)} · CPC title