Arc-fault and ground fault interrupter using a single ground fault sensor and single ADC

• US 9,810,741 B2
• Filed: 09/13/2013
• Issued: 11/07/2017
• Est. Priority Date: 09/13/2013
• Status: Active Grant

• Current Assignee: Schneider Electric USA, Inc. (Schneider Electric SE)
• Original Assignee: Schneider Electric USA, Inc. (Schneider Electric SE)
• Inventors: Dram, Issa Vignon, Gass, Randall James
• Primary Examiner(s): Huffman, Julian
• Assistant Examiner(s): Konczal, Michael
• Application Number:
  US14/911,685
• Publication Number:
  US 20160202321A1
• Time in Patent Office: 1,516 Days
• CPC Class Codes: G01R 19/2509 Details concerning sampling, digitizing or waveform capturing
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
• CPC Class Codes: G01R 31/3277 of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 3/093 with timing means in general H02H3/027; thermal delay H02H3/085; timing means for undervoltage protection H02H3/247
• CPC Class Codes: H02H 3/16 responsive to fault current to earth, frame or mass with balanced or differential arrangement H02H3/26 ; monitoring earth connection H02H5/105
• CPC Class Codes: H02H 3/167 combined with other earth-fault protective arrangements
• CPC Class Codes: H02H 3/33 using summation current transformers H02H3/347 takes precedence

Abstract

Sampling for arc-fault detection, ground-fault detection, and grounded-neutral fault detection uses a single analog-to-digital converter (ADC). The arc-fault and ground-fault sampling occurs at regular sampling periods that are relatively short com pared to the time between them, thus allowing grounded-neutral fault sampling to occur before and/or after one of these sampling periods. A predefined event may be used to ensure the grounded-neutral fault sampling occurs immediately before and/or after one of the periodic sampling periods. The predefined event may be the expiration of a timer or the time for a sinusoidal signal in a ground fault sense circuit to make a predefined number of zero-crossings. This avoids interference between the arc-fault sampling, the ground-fault sampling and grounded-neutral fault sampling, allowing a single ADC to perform all samplings concurrently. The timing of the predefined event may be periodically reset to compensate for any changes due to temperature and/or over time.

Claims

1. A method of performing arc-fault sampling, ground-fault sampling, and grounded-neutral fault sampling in a circuit breaker device, comprising:

performing the arc-fault sampling during a plurality of arc-fault sampling periods, the arc-fault sampling periods occurring at regular intervals and each arc-fault sampling period lasting a fixed duration that is shorter than the time in between consecutive arc-fault sampling periods;

monitoring for an occurrence of a predefined event in the circuit breaker device, the predefined event being timed to occur coincident with one of the plurality of arc-fault sampling periods; and

performing the grounded-neutral fault sampling near the occurrence of the predefined event such that the grounded-neutral fault sampling is performed between said one of the plurality of arc-fault sampling periods and an immediately adjacent arc-fault sampling period;

wherein the arc-fault sampling, ground-fault sampling, and the grounded-neutral fault sampling are performed during a common detection interval.

2. The method according to claim 1, further comprising calculating a delay time for the predefined event, the delay time ensuring that the predefined event occurs coincident in time with one of the plurality of arc-fault sampling periods.

3. The method according to claim 1, further comprising generating a sinusoidal signal in the circuit breaker device, wherein the predefined event is the final zero-crossing in a predefined number of zero-crossings made by the sinusoidal signal.

4. The method according to claim 1, wherein the predefined number of zero-crossings is any number between one and 50.

5. The method according to claim 1, wherein the grounded-neutral fault sampling is performed between said one of the plurality of arc-fault sampling periods and an immediately preceding arc-fault sampling period and between said one of the plurality of arc-fault sampling periods and an immediately following arc-fault sampling period.

6. The method according to claim 1, wherein the ground-fault sampling is performed in a different portion of the common detection interval from the grounded-neutral fault sampling.

7. The method according to claim 1, wherein the arc-fault sampling and the ground-fault sampling are based off a zero-crossing of a supply line voltage.

8. The method according to claim 1, wherein the arc-fault sampling and the ground-fault sampling are based off a timer programmed for a predetermined amount of time and the predefined event is timed to occur based off said timer.

9. A system for performing arc-fault sampling, ground-fault sampling, and grounded-neutral fault sampling in an circuit breaker device, comprising:

a single system controller programmed to perform the arc-fault sampling, ground-fault sampling, and the grounded-neutral fault sampling during a common detection interval;

a ground fault sense circuit connected to the system controller and configured to provide ground-fault sensor input and grounded-neutral fault sensor input to the system controller for performing the ground-fault sampling and the grounded-neutral sampling; and

an arc-fault sense circuit connected to the system controller and configured to provide arc-fault sensor input to the system controller for the performing arc-fault sampling;

wherein the single system controller is configured to monitor for an occurrence of a predefined event in the circuit breaker device and perform the grounded-neutral fault sampling near the occurrence of the predefined event such that the grounded-neutral fault sampling is performed between one of a plurality of arc-fault sampling periods and an immediately adjacent arc-fault sampling period.

10. The system according to claim 9, wherein the grounded-neutral fault sensor input includes a sinusoidal signal and the predefined event is the final zero-crossing in a predefined number of zero-crossings made by the sinusoidal signal.

11. The system according to claim 10, wherein the predefined number of zero-crossings is a number that allows a peak-to-peak voltage of the sinusoidal signal to decay to within a predefined voltage range.

12. The system according to claim 9, wherein the single system controller is further configured to calculate a delay time for the predefined event, the delay time ensuring that the predefined event occurs coincident in time with said one of the plurality of arc-fault sampling periods.

13. The system according to claim 9, wherein the single system controller is further configured to perform the grounded-neutral fault sampling between said one of the plurality of arc-fault sampling periods and an immediately preceding arc-fault sampling period and an immediately following arc-fault sampling period.

14. The system according to claim 9, wherein the single system controller performs the arc-fault sampling periods at a predefined time interval relative to each other and each arc-fault sampling period is performed for a fixed duration that is shorter than the predefined time interval.

15. The system according to claim 9, the circuit breaker device is connected to a supply line voltage and the single system controller is further configured to initiate the arc-fault sampling and the ground-fault sampling upon a zero-crossing of a supply line voltage.

16. A controller in a circuit breaker device configured to perform arc-fault sampling and grounded-neutral fault sampling, comprising:

an analog-to-digital converter module (ADC) having a single input and a single output, the ADC configured to receive arc-fault sensor signals, ground-fault sensor signals, and a grounded-neutral fault sensor signal, the grounded-neutral fault sensor signal including a decaying sinusoidal signal;

a comparator module configured to receive the grounded-neutral fault sensor signal and to detect zero-crossings made by the decaying sinusoidal signal;

an input capture module configured to receive an indication of a zero-crossing detected by the comparator module and capture a timestamp for the zero-crossing; and

an output compare module configured to initiate the decaying sinusoidal signal received by the ADC and the comparator;

the controller being configured to;

operate the output compare module to initiate the decaying sinusoidal signal;

operate the ADC to receive the decaying sinusoidal signal;

operate the comparator module to detect zero-crossings made by the decaying sinusoidal signal; and

operate the input capture module to obtain a timestamp for a zero-crossing;

the controller being further configured to monitor for a predefined zero-crossing and perform the grounded-neutral fault sampling predefined zero-crossing, the predefined zero-crossing occurring coincident in time with one of a plurality of arc-fault sampling periods such that the grounded-neutral fault sampling is performed between said one of the plurality of arc-fault sampling periods and an immediately adjacent arc-fault sampling period;

wherein the arc-fault sampling, grounded-fault sampling, and the grounded-neutral fault sampling are performed during a shared detection interval.

17. The controller according to claim 16, further comprising an arc-fault and ground fault detection module operated by the controller to detect arc-faults and grounded-neutral faults based on the arc-fault sensor signals and the grounded-neutral fault sensor signal.

18. The controller according to claim 16, further comprising a grounded-neutral sensor test control module operated by the controller to calculate a delay time for the predefined zero-crossing, the delay time ensuring that the predefined zero-crossing occurs substantially coincident in time with said one of the plurality of arc-fault sampling periods.

19. The controller according to claim 18, further comprising a timer operable by the controller to count down the delay time and by the comparator module to detect zero-crossings made by the decaying sinusoidal signal.

20. The controller according to claim 16, further comprising a voltage reference programmed by the controller, the voltage reference allowing the comparator module to determine when the decaying sinusoidal signal has made a zero-crossing.