Multi-frequency ground fault circuit interrupter apparatuses, systems, and method

Patent metadata

Field	Value
Publication number	US-11394190-B2
Application number	US-202017085301-A
Country	US
Kind code	B2
Filing date	Oct 30, 2020
Priority date	Oct 30, 2020
Publication date	Jul 19, 2022
Grant date	Jul 19, 2022

Abstract

A GFCI includes a current sensor system providing a current sensor signal indicating a leakage current of the AC power system. A magnitude detector is configured to provide a first channel signal indicating an RMS value of the current sensor signal. A reference signal generator is configured to provide a second channel signal indicating a trip reference value responsive to a frequency of the current sensor signal. A fault detector is configured to provide a fault trip signal indicating ground fault condition of the AC power system in response to the first channel signal and the second channel signal. A circuit breaker mechanism is configured to open a circuit of the AC power system in response to the fault trip signal.

First claim

The invention claimed is:

1. An apparatus, comprising:
a current sensor system operatively coupled with an AC power system and configured to provide a current sensor signal indicating a leakage current of the AC power system;
a first channel operatively coupled with the current sensor system and including a magnitude detector configured to provide a first channel signal indicating a magnitude of the current sensor signal;
a second channel operatively coupled with the current sensor system and including a reference signal generator configured to provide a second channel signal indicating a trip reference value varying in response to a frequency of the current sensor signal;
wherein the reference signal generator includes:
a frequency-to-voltage converter configured to output a voltage value responsive to a frequency of the current sensor signal, and
an amplifier operatively coupled with the frequency-to-voltage converter and configured to output the second channel signal in response to the voltage value;

a fault detector operatively coupled with the first channel and the second channel and configured to provide a fault trip signal indicating ground fault condition of the AC power system in response to the first channel signal and the second channel signal; and
a circuit breaker mechanism operatively coupled with the fault detector and configured to open a circuit of the AC power system in response to the fault trip signal.

2. The apparatus of claim 1 , wherein the current sensor system comprises a current transformer operatively coupled with at least a phase conductor and a neutral conductor of the AC power system on a primary side and operatively coupled with an impedance component on a secondary side wherein the current sensor signal comprises a voltage across the impedance component.

3. The apparatus of claim 2 , wherein the current sensor system includes an amplifier operatively coupled with the impedance component and configured to amplify the voltage across the impedance component to provide the current sensor signal.

4. The apparatus of claim 1 , wherein the magnitude detector includes a rectifier configured to rectify the current sensor signal and an amplifier operatively coupled with the rectifier and configured to output an RMS value of the rectified current sensor signal as the first channel signal.

5. The apparatus of claim 1 , wherein the reference signal generator includes a frequency divider configured to reduce the frequency of the current sensor signal and to provide the reduced frequency current sensor signal to the frequency-to-voltage converter.

6. The apparatus of claim 1 , wherein the reference signal generator includes a sine-to-square wave converter configured to convert a sinusoidal shape of the current signal to a square shape and to provide the square-shaped current sensor signal to the frequency-to-voltage converter.

7. The apparatus of claim 1 , wherein the fault detector comprises a voltage comparator including a first input configured to receive the first channel signal and a second input configured to receive the second channel signal.

8. The apparatus of claim 1 , wherein the circuit breaker mechanism includes a driver configured to drive a solenoid operatively coupled with a breaker switch in response to the fault trip signal.

9. The apparatus of claim 1 , wherein the current sensor signal, the first channel signal, and the second channel signal comprise voltage signals.

10. The apparatus of claim 1 , comprising a third channel operatively coupled with the current sensor system and including a second fault detector configured to provide a second fault trip signal to the circuit breaker mechanism in response to the current sensor signal.

11. The apparatus of claim 10 , wherein the second fault detector is configured to provide the second fault trip signal a time before the first trip signal would be provided by the fault detector in response to the current sensor signal exceeding a second trip reference value greater than the trip reference value of the second channel.

12. A method, comprising:
operating a current sensor system to provide a current sensor signal indicating a leakage current of an AC power system;
providing the current sensor signal to a first channel including a magnitude detector; operating the magnitude detector to provide a first channel signal indicating a magnitude of the current sensor signal;
providing the current sensor signal to a second channel including a reference signal generator;
operating the reference signal generator to provide a second channel signal indicating a trip reference value responsive to a frequency of the current sensor signal;
wherein the operating the reference signal generator includes converting a frequency of the current sensor signal to a voltage and determining the second channel signal in response to the voltage;

detecting a ground fault condition of the AC power system in response to the first channel signal and the second channel signal; and
opening a circuit of the AC power system in response to the detecting the ground fault condition.

13. The method of claim 12 , wherein the operating the current sensor system comprises operating a current transformer operatively coupled with at least a phase conductor and a neutral conductor of the AC power system on a primary side and operatively coupled with an impedance component on a secondary side to provide a voltage across the impedance component.

14. The method of claim 12 , wherein the operating the current sensor system comprises amplifying a voltage across the impedance component to provide the current sensor signal.

15. The method of claim 12 , wherein the operating the magnitude detector comprises determining an RMS value of the rectified current sensor signal, and providing the RMS value as the first channel signal.

16. The method of claim 12 , wherein the operating the reference signal generator includes one or both of (a) converting the current sensor signal from a sinusoidal shape to a square shape, and (b) reducing the frequency of the current sensor signal.

17. The method of claim 12 , wherein the detecting a ground fault condition includes comparing the first channel signal and a second channel signal, and indicating the ground fault condition if the first channel signal exceeds a value of the second channel signal.

18. The method of claim 12 , wherein the current sensor signal, the first channel signal, and the second channel signal comprise voltage signals.

19. The method of claim 12 , comprising providing the current sensor signal to a third channel and detecting a second ground fault condition of the AC power system in response to the current sensor signal, and opening the circuit of the AC power system in response to the detecting the second ground fault condition.

20. The method of claim 19 , wherein the detecting a second ground fault condition occurs before a time required for the detecting the ground fault condition of the AC power system in response to the first channel signal and the second channel signal.

Assignees

• Abb Schweiz Ag

Inventors

• Rivers Cecil
• Lituchy David Joseph

Classifications

• H02H3/33 Primary

  using summation current transformers (H02H3/347 takes precedence) · CPC title

• H02H3/006

  Calibration or setting of parameters · CPC title

• G01R15/183

  using transformers with a magnetic core · CPC title

• H02H3/334

  with means to produce an artificial imbalance for other protection or monitoring reasons or remote control (H02H3/338 takes precedence) · CPC title

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title