Systems and methods for arc fault detection

• US 20080106832A1
• Filed: 10/30/2007
• Published: 05/08/2008
• Est. Priority Date: 10/31/2006
• Status: Active Grant

• Current Assignee: Siemens Industry Incorporated (Siemens AG)
• Original Assignee: Siemens Industry Incorporated (Siemens AG)
• Inventors: Staley, Peter, Restrepo, Carlos, Mikani, Vaske, Kinsel, Hugh, Nayak, Amit
• Granted Patent: US 7,864,492 B2
• Time in Patent Office: Days
• US Class Current: 361/42
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 1/0092 concerning the data processing means, e.g. expert systems, neural networks
• CPC Class Codes: H02H 3/33 using summation current transformers H02H3/347 takes precedence

Abstract

In accordance with one aspect the present disclosure is directed toward a method for detecting arc faults on a power line. The method may include monitoring power signals associated with a power line and filtering the power signals to produce a high frequency signal and a low frequency signal. A mask signal may generated based on the low frequency signal, and the high frequency signal may be analyzed to extract a broadband portion of the high frequency signal. A fault counter may be incremented if the magnitude of the broadband portion is approximately greater than a first threshold level. A fault counter may be decremented if the magnitude of the broadband portion is approximately less than the first threshold level. A trip signal is provided to a switching device associated with the power line if the fault counter exceeds a predetermined fault limit.

Claims

1. An electrical fault detection device, comprising:

a high-frequency sensor coupled to an electrical distribution line for detecting a high-frequency component of a sinusoidal electrical power signal;

a series arc-detection circuit coupled to the high-frequency sensor and including;

a high-frequency module configured to identify a broadband portion of the high-frequency component; and

a detection module configured to;

rectify the sinusoidal electrical power signal;

store a fault count value representing a propensity of the high-frequency component to be an arc fault;

adjust the fault count value based on at least one characteristic of the broadband portion, the at least one characteristic including one or more of a quarter-cycle amplitude of the broadband portion during the quarter cycle following a zero crossing of the rectified sinusoidal electrical power signal, a non-quarter-cycle amplitude of the broadband portion after the quarter cycle, and a rate-of-change of the amplitude of the broadband portion, wherein each of the at least one characteristic has a respective weighted value compared with the other characteristics for adjusting the fault count value; and

generate a series-arc trip signal if the fault count value exceeds a fault count threshold; and

a trip circuit responsive to the series-arc trip signal for opening the electrical distribution line.

2. The electrical fault detection device of claim 1, wherein the high-frequency module includes a superheterodyne receiver.

3. The electrical fault detection device of claim 1, further comprising:

a low-frequency sensor coupled to the electrical distribution line for detecting a low-frequency portion of the rectified sinusoidal electrical power signal;

a parallel-arc detection circuit coupled to the low-frequency sensor and configured to;

monitor the amplitude of a current level associated with the low-frequency portion of the rectified sinusoidal electrical power signal; and

generate a parallel-arc trip signal if the amplitude of the current level of the low frequency portion exceeds a threshold parallel-arc current level, wherein the trip circuit is further configured to open the electrical distribution line in response to the parallel-arc trip signal.

4. The electrical fault detection device of claim 3, further comprising:

a differential sensor electromagnetically coupled to hot and neutral lines of the electrical distribution line for detecting a differential current between the hot and neutral lines;

a differential fault detection circuit coupled to the differential sensor and configured to generate a differential fault trip signal if the amplitude of the differential current exceeds a threshold differential current, wherein the trip circuit is further configured to open the electrical distribution line in response to the differential fault trip signal.

5. The electrical fault detection device of claim 4, further including:

a memory device adapted to record one or more of a series-arc trip signal, a parallel-arc trip signal, and a differential trip signal prior to an opening of the electrical distribution line; and

a display device adapted to display a signal indicative of one or more recorded trip signals.

6. The electrical fault detection device of claim 1, wherein the detection device is further configured to:

determine a dynamic range of the broadband portion; and

decrease the fault count value if the dynamic range of the broadband portion does not exceed a threshold dynamic range.

7. The electrical fault detection device of claim 1, wherein the detection module is configured to establish a zero-crossing time period representing the time period that the amplitude of the rectified sinusoidal electrical power signal is below a threshold level.

8. The electrical fault detection device of claim 7, wherein the threshold current level is selected such that the zero-crossing time period is about 2 milliseconds.

9. The electrical fault detection device of claim 7, wherein the detection module is further configured to:

detect a minimum amplitude of the broadband portion during the zero crossing time period; and

subtract the minimum amplitude from the amplitude of the broadband portion outside the zero-crossing time before adjusting the fault count value.

10. The electrical fault detection device of claim 7, wherein the detection module is further configured to:

decrease the fault count value at a first rate while the quarter-cycle amplitude at the end of the zero-crossing time period does not exceed a first amplitude threshold.

11. The electrical fault detection device of claim 10, wherein at the end of the zero-crossing time period includes about 200-400 microseconds after the end of the zero-crossing time period.

12. The electrical fault detection device of claim 10, wherein the detection module is further configured to:

decrease the fault count value at a second rate while the non-quarter-cycle amplitude outside the zero-crossing time period is less than a second amplitude threshold, wherein the second rate is less than the first rate.

13. The electrical fault detection device of claim 12, wherein the detection module is further configured to:

increase the fault count value at the second rate while the non-quarter-cycle amplitude outside the zero-crossing time period is greater than the second amplitude threshold.

14. The electrical fault detection device of claim 13, wherein the detection module is further configured to:

decrease the fault count value at a third rate while the rate-of-change is less than a slope threshold outside the zero crossing time period, wherein the third rate is greater than the first rate.

15. The electrical fault detection device of claim 14, wherein the detection module is further configured to:

identify a peak of the rate-of-change;

hold the peak rate-of-change to produce a decaying peak hold signal; and

prevent increase of the fault count value if the decaying slope reference signal is less than a peak hold threshold.

16. The electrical fault detection device of claim 7, wherein the detection module is further configured to:

detect a number of instances that the quarter-cycle amplitude and the non-quarter-cycle amplitude collectively cross a first amplitude threshold after the zero-crossing time period; and

decrease the fault count value by a first rate if the number of instances exceeds a first threshold crossing limit.

17. The electrical fault detection device of claim 16, wherein the detection module is further configured to:

detect a number of instances that the quarter-cycle and the non-quarter-cycle amplitude collectively cross a second amplitude threshold after the zero-crossing time period; and

decrease the fault count value by the first rate if the number of instances that the amplitude of the broadband portion exceeds a second threshold crossing limit.

18. The electrical fault detection device of claim 17, wherein the first amplitude threshold is less than the second amplitude threshold and the first threshold crossing limit is less than the second threshold crossing limit.

19. An electrical fault detection device, comprising:

a high-frequency sensor coupled to an electrical distribution line for detecting a high-frequency component of a rectified sinusoidal electrical power signal;

a series arc-detection circuit coupled to the high-frequency sensor and including;

a high-frequency module configured to identify a broadband portion of the high-frequency component; and

a detection module configured to;

rectify the sinusoidal electrical power signal;

subtract a minimum amplitude of the broadband portion proximate to a zero crossing of the rectified sinusoidal electrical power signal from the broadband portion;

increment a fault count value, representing a propensity of the high-frequency component to be an arc fault, when the broadband portion meets at least one increment criterion during select sub-cycles of the rectified sinusoidal electrical power signal;

decrement the fault count value when the broadband portion meets at least one decrement criterion during the select sub-cycles, the at least one decrement criterion including one of (a) the amplitude of the broadband portion not exceeding a magnitude threshold and (b) the amplitude exceeding a crossover threshold a predetermined number of times; and

generate a series-arc trip signal if the fault count value exceeds a fault count threshold; and

a trip circuit responsive to the series-arc trip signal for opening the electrical distribution line.

20. An electrical fault detection device, comprising:

a high-frequency sensor coupled to an electrical distribution line for detecting a high-frequency component of a sinusoidal electrical power signal;

a series arc-detection circuit coupled to the high-frequency sensor and including;

a high-frequency module configured to identify a broadband portion of the high-frequency component; and

a detection module configured to;

rectify the sinusoidal electrical power signal;

subtract a minimum amplitude of the broadband portion proximate to a zero crossing of the rectified sinusoidal electrical power signal from the broadband portion;

increment a fault count value, representing a propensity of the high-frequency component to be an arc fault, while the amplitude of the broadband portion exceeds a preset limit;

decrement the fault count value when the broadband portion meets at least one decrement criterion during the select sub-cycles, the at least one decrement criterion including one of (a) a dynamic range of the broadband portion not exceeding a threshold dynamic range and (b) a rate-of-change of the amplitude of the broadband portion not exceeding a slope threshold; and

generate a series-arc trip signal if the fault count value exceeds a fault count threshold; and

a trip circuit responsive to the series-arc trip signal for opening the electrical distribution line.

21. An electronic circuit for detecting series arcing conditions in a sinusoidal electrical signal, comprising:

a rectifier configured to obtain the absolute value of the sinusoidal electrical signal;

a superheterodyne receiver configured to extract a broadband component from the rectified sinusoidal signal;

a counter coupled to the receiver and configured to change a fault count value, the fault count value representing a propensity of the sinusoidal signal to include a series arcing condition, the change occurring at multiple rates based on one or more of a quarter-cycle amplitude of the broadband component during the quarter cycle following a zero crossing of the rectified sinusoidal signal, a non-quarter-cycle amplitude of the broadband component after the quarter cycle, and a rate-of-change of the amplitude of the broadband component; and

a comparator coupled to the counter for generating a series-arc trip signal when the fault count value exceeds a fault count threshold.

22. The electronic circuit of claim 21, wherein the counter decrements and the rate is higher when the quarter-cycle amplitude does not exceed a first amplitude threshold than when the non-quarter-cycle amplitude does not exceed the first amplitude threshold.

23. The electronic circuit of claim 21, wherein the counter decrements and the rate is higher when the quarter-cycle amplitude and the non-quarter-cycle amplitude collectively exceed a crossover threshold a predetermined number of times than when the non-quarter-cycle amplitude does not exceed the first amplitude threshold.

24. The electronic circuit of claim 22, wherein the electronic circuit comprises an ASIC and a microprocessor.

25. A method for electrical fault detection comprising:

detecting a high-frequency component of a sinusoidal electrical power signal;

identifying a broadband portion of the high-frequency component;

storing a fault count value representing a propensity of the high-frequency component to be an arc fault;

adjusting the fault count value based on at least one characteristic of the broadband portion, the at least one characteristic including one or more of the amplitude of the broadband portion during the rising quarter cycle of the sinusoidal electrical power signal, the amplitude of the broadband portion after the rising quarter cycle, and a rate of change of the amplitude of the broadband portion, wherein the at least one characteristic corresponds with a weighted adjustment factor, the weighted adjustment factor defining an amount by which the fault count value is adjusted upon detection of the at least one characteristic;

generating a trip signal if the fault count value exceeds a fault count threshold; and

providing the trip signal to a trip circuit for opening the electrical distribution line in response to the trip signal.