Arc fault detection

• US 9,945,894 B2
• Filed: 02/19/2013
• Issued: 04/17/2018
• 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.
• Primary Examiner(s): Raymond, Edward
• Application Number:
  US13/770,382
• Publication Number:
  US 20130226479A1
• Time in Patent Office: 1,883 Days
• Field of Search: 702 58, 702182-185
• 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 method comprising:

acquiring a first waveform using an arc-fault detection circuit having active filters and signal amplifiers;

determining, using a hardware processor, a first Average Magnitude Different Function (AMDF) of the first waveform acquired using the arc-fault detection circuit;

locating a first minimum peak of the first AMDF; and

determining whether an arc fault is detected as a function of the first minimum peak.

2. The method of claim 1, further comprising:

deriving a modified waveform by applying a time-delay to the first waveform;

calculating a frequency-response plot of the modified waveform;

calculating a high frequency minima in a high-frequency range of the frequency-response plot, the high-frequency range being outside of a pass-band of the arc-fault detection circuit;

calculating a low-frequency minima in a low-frequency range of the frequency-response plot, the low-frequency range being within the pass-band of the arc-fault detection circuit;

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

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

3. The method of claim 2, calculating the frequency-response plot, comprising:

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

4. The method of claim 3, further comprising

smoothing the FFT.

5. The method of claim 1, wherein acquiring the first waveform comprises acquiring the first waveform using an arc-fault detection circuit having active filters and signal amplifiers arranged in a Sallen-Key topology.

6. A method comprising:

acquiring a first waveform using an arc-fault detection circuit having active filters and signal amplifiers;

calculating, using a hardware processor, a frequency-response plot of the waveform acquired using the arc-fault detection circuit;

estimating a noise amplitude in a high-frequency range of the frequency-response plot, the high-frequency range being outside of a pass-band of the arc-fault detection circuit, the noise amplitude 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 to calculate an amplitude in the low-frequency range, the low-frequency range being within the pass-band of the arc-fault detection circuit, the function being 1/f^β

-dependent, where;

0<

β

<

2; and

determining whether an arc fault is detected based on a ratio of the noise amplitude in the high-frequency range and the amplitude in the low-frequency range.

7. The method of claim 6, 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 first linear curve fit producing a first value at a first selected frequency.

8. The method of claim 7, 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 second linear curve fit producing a slope and a second value at a second selected frequency.

9. The method of claim 8, determining whether the arc fault is detected comprising:

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

10. The method of claim 9, further comprising:

determining whether the calculated ratio exceeds a predetermined threshold; and

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

11. The method of claim 8, further comprising:

determining whether the slope is less than zero; and

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

12. The method of claim 11, 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 the arc fault is detected in response to the SD being less than threshold_SD.

13. The method of claim 12, 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.

14. The method of claim 13, further comprising:

indicating that the 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.

15. The method of claim 7, 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 6, wherein acquiring the first waveform comprises acquiring the first waveform using an arc-fault detection circuit having active filters and signal amplifiers arranged in a Sallen-Key topology.