Arc Fault Detection

• US 20130226479A1
• Filed: 02/19/2013
• Published: 08/29/2013
• Est. Priority Date: 02/29/2012
• Status: Active Grant

• Current Assignee: Innovative Scientific Solutions, Inc.
• Original Assignee: Innovative Scientific Solutions, Inc.
• Inventors: Grosjean, Dennis F.
• Granted Patent: US 9,945,894 B2
• Time in Patent Office: Days
• US Class Current: 702/58
• CPC Class Codes: G01R 31/12 Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing G01R31/08, G01R31/327 and G01R31/72 take precedence; measuring in plasmas G01R19/0061; measuring dielectric constants G01R27/2617; ESD, EMC or EMP testing of circuits G01R31/002
• 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 3/40 responsive to ratio of voltage and current

Abstract

The present disclosure provides systems and methods for detecting arc faults. For some embodiments, arc faults are detected from waveforms that are acquired and processed, preferably using an Average Magnitude Difference Function (AMDF). The characteristics of the waveform provide an indication of whether or not an arcing fault occurred.

Claims

1. A process for detecting arc faults, the process comprising:

determining a first Average Magnitude Different Function (AMDF) of a first waveform, the first AMDF being defined as;

2. A method for detecting arc faults, the method comprising:

determining a first Average Magnitude Different Function (AMDF) of a first waveform;

locating a first minimum peak of the first AMDF; and

deriving a modified waveform from the first waveform; and

determining whether or not an arc fault is detected as a function of the first minimum peak.

3. The method of claim 2, further comprising:

determining a second AMDF of the modified waveform;

locating a second minimum peak from the second AMDF; and

determining whether or not an arc fault is detected as a function of the second minimum peak.

4. The method of claim 3, the first AMDF being:

5. The method of claim 4, the second AMDF being:

AMDF(τ

_k)=<

|X(t)−

X(t−

δ

)−

X(t−

τ

_k)+X(t−

δ

−

τ

_k)|>

where t is time;

τ

_k is a time delay of k; and

δ

is a dominant period, the dominant period correlating to the first minimum peak.

6. The method of claim 3, determining whether an arc fault is detected, comprising:

determining whether the first minimum peak exceeds a first predetermined threshold;

determining whether the second minimum peak exceeds a second predetermined threshold;

responsive to the first minimum peak exceeding the first predetermined threshold and the second minimum peak exceeding the second predetermined threshold, indicating that an arc fault is detected, otherwise indicating that no arc fault is detected.

7. The method of claim 2, further comprising:

calculating a frequency-response plot of the modified waveform;

calculating a high-frequency minima in a high-frequency range of the frequency-response plot;

calculating a low-frequency minima in a low-frequency range of the frequency-response plot;

calculating a ratio of the low-frequency minima to the high-frequency minima; and

determining whether an arc fault is detected as a function of the calculated ratio.

8. The method of claim 7, calculating the frequency-response plot, comprising:

performing a Fast Fourier Transform (FFT) on the modified waveform.

9. The method of claim 8, further comprising

smoothing the FFT.

10. A method for detecting arc faults, comprising:

calculating a frequency-response plot of a waveform;

estimating noise in a high-frequency range of the frequency-response plot, the noise being estimated by performing a first curve fit of a high-frequency range;

performing a second curve fit of a low-frequency range to a function, the function being 1/f^β

-dependent, where;

0<

β

<

2; and

determining whether an arc fault is detected as a function of the first curve fit and the second curve fit.

11. The method of claim 10, estimating the noise, comprising:

generating a logarithm of the frequency-response plot;

performing a first linear curve fit on the high-frequency range of the logarithm of the frequency-response plot, the high-frequency range being outside of a pass-band of a circuit, the first linear curve fit producing a first value at a first selected frequency.

12. The method of claim 11, performing the second curve fit, comprising:

performing a second linear curve fit on the low-frequency range of the logarithm of the frequency-response plot, the low-frequency range being within the pass-band of the circuit, the second linear curve fit producing a slope and a second value at a second selected frequency.

13. The method of claim 12, determining whether the arc fault is detected, comprising:

calculating a ratio of the second value to the first value.

14. The method of claim 13, further comprising:

determining whether the calculated ratio exceeds a predetermined threshold; and

indicating that an arc fault is detected in response to the ratio exceeding the predetermined threshold.

15. The method of claim 11, calculating the frequency-response plot, comprising:

performing a Fast Fourier Transform (FFT) on the waveform.

16. The method of claim 15, further comprising:

smoothing the FFT.

17. The method of claim 12, further comprising:

determining whether the slope is less than zero; and

indicating that an arc fault is detectible in response to the slope being less than zero.

18. The method of claim 17, further comprising:

determining whether a standard deviation (SD) of the second curve fit is less than a predetermined SD-threshold (threshold_SD); and

indicating that an arc fault is detectible in response to the SD being less than thresholds.

19. The method of claim 18, further comprising:

calculating a ratio of the second value to the first value;

determining whether the calculated ratio exceeds a predetermined ratio threshold (threshold_RATIO); and

indicating that no arc fault is detected in response to the ratio not exceeding threshold_RATIO.

20. The method of claim 19, further comprising:

indicating that an arc fault is detected in response to;

the slope being less than zero;

the SD being less than threshold_SD; and

the ratio exceeding threshold_RATIO.