Method and apparatus for detecting arcing in AC power systems by monitoring high frequency noise
First Claim
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1. A method for detecting the presence of electrical arcing on an AC power line of frequency F and period T=1/F, comprising the following steps:
- monitoring the line current, line voltage, or energy emitted from the line as a waveform;
supplying the monitored waveform to the input of a narrow bandpass variable-frequency filter having a minimum pass frequency substantially higher than F; and
examining the signal passing through the filter as a function of time, to detect recurring features indicative of arcing.
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Abstract
Arcing in an AC power system is detected by monitoring the power waveform for wideband high-frequency noise, and examining the detected noise for patterns of variation in its amplitude synchronized to the power waveform. A narrowband, swept-frequency detector and synchronous averaging may be employed to improve discrimination of arc noise from background interference. An arcing fault interrupter for controlling a single circuit, and a whole house monitor, for detecting arcing anywhere in a house, are described.
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Citations
51 Claims
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1. A method for detecting the presence of electrical arcing on an AC power line of frequency F and period T=1/F, comprising the following steps:
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monitoring the line current, line voltage, or energy emitted from the line as a waveform; supplying the monitored waveform to the input of a narrow bandpass variable-frequency filter having a minimum pass frequency substantially higher than F; and examining the signal passing through the filter as a function of time, to detect recurring features indicative of arcing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. In an AC electrical network, wherein any electrical contact arcing in the network superimposes wide bandwidth high frequency noise on a power supply line, the amplitude of the superimposed noise exhibiting patterns of regular variation substantially synchronized to the AC line cycle, a method for synchronous averaging of the noise on the line for improved discrimination of the patterns exhibited by the noise, and for detecting such patterns, comprising the steps of:
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dividing the line cycle into a plurality of portions of equal length; sampling the amplitude of the noise during each portion of a number of successive line cycles; summing and scaling the amplitudes of the noise sampled during corresponding portions of successive line cycles, thereby producing a synchronously averaged waveform; and examining the synchronously averaged waveform in order to locate patterns of regular variation in the amplitude of the waveform substantially synchronized to the line cycle. - View Dependent Claims (16)
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17. Apparatus for detecting the presence of electrical arcing on an AC power line, comprising:
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means for monitoring one of the line voltage, line current, or energy emitted from the line and for extracting high-frequency noise therefrom; means for synchronously averaging the extracted noise signal, comprising; means for dividing the AC line cycle into a plurality of portions of equal length; means for sampling the amplitude of the noise during each portion of a number of successive line cycles; and means for summing the amplitudes of the noise sampled during corresponding portions of successive line cycles, thereby producing a synchronously averaged noise signal; and means for examining the synchronously averaged noise signal to detect arcing on the power line, comprising; means for comparing portions of the synchronously averaged noise signal to one another, in order to locate patterns of regular variation in the amplitude of the noise substantially synchronized to the AC line cycle. - View Dependent Claims (18, 19, 20, 21)
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22. Apparatus for detecting electrical contact arcing in an electrical network having at least one AC power supply line, such that any arcing in the network superimposes wide bandwidth high frequency noise on the AC power waveform, the amplitude of the superimposed noise exhibiting patterns of regular variation substantially synchronized to the AC power waveform, comprising:
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frequency-domain analysis means, for examining high-frequency noise on the power waveform as a function of frequency; time-domain analysis means for examining a signal proportional to the amplitude of the high-frequency noise on the power waveform as a function of time; and means for providing a signal that arcing is present, if; (1) said frequency-domain analysis means determines that high-frequency noise on the power waveform exhibits frequency components conforming to predetermined characteristics of arcing-induced noise; and (2) said time-domain analysis means determines that said signal proportional to the amplitude of the high-frequency noise on the power waveform exhibits predetermined patterns of variation in amplitude conforming to predetermined characteristics of arcing-induced noise. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. Apparatus for detecting contact arcing in an electrical network having AC power supply lines, such that arcing in the network superimposes wide bandwidth high frequency noise on the power supply lines, the amplitude of the superimposed noise exhibiting patterns of regular variation substantially synchronized to the AC power waveform, comprising:
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a swept-frequency bandpass filter, for filtering high frequency noise from the power lines, and for discriminating wide bandwidth noise on the power lines from impulse and specular noise; and means for examining an output signal from the swept-frequency bandpass filter to determine whether said output signal exhibits patterns characteristic of arcing on the power lines. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A method for detecting the presence of arcing in an AC power distribution system, such that such arcing impresses high-frequency noise exhibiting predetermined variation with time on the power waveform, comprising the steps of:
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performing a frequency-domain test, to determine whether the frequency of noise on said power waveform conforms to predetermined criteria indicative of arcing; performing a time-domain test, to determine whether the amplitude of noise on said power waveform varies in conformity with predetermined patterns indicative of arcing; and determining that arcing has been detected only when both said frequency-domain and said time-domain tests have been satisfied. - View Dependent Claims (45, 46, 47, 48, 49, 50, 51)
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Specification