Method and apparatus for detecting high-impedance faults in electrical power systems
First Claim
1. A method for detecting high impedance faults on a power line, the steps comprising:
- a) sensing a plurality of cycles of currents attributable to a power line and generating a signal representative thereof;
b) computing a first derivative of cycle-to-cycle maxima or minima of said current;
c) transforming said derivatives into a frequency domain representation thereof, the power spectrum of which frequency domain representation being usable by means for processing information;
d) applying said power spectrum to means for processing information using artificial intelligence techniques to detect a high-impedance fault and to generate a fault signal indicative thereof; and
e) actuating a switch in response to said fault signal.
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Abstract
The present invention features a method and apparatus for detecting and enabling the clearance of high impedance faults (HIFs) in an electrical transmission or distribution system. Current in at least one phase in a distribution system is monitored in real time by sensors. Analog current signature information is then digitized for processing by a digital computer. Zero crossings are identified and current maxima and minima located. The first derivatives of the maxima and minima are computed and a modified Fast Fourier Transform (FFT) is then performed to convert time domain to frequency domain information. The transformed data is formatted and normalized and then applied to a trained neural network, which provides an output trigger signal when an HIF condition is probable. The trigger signal is made available to either a network administrator for manual intervention, or directly to switchgear to deactivate an affected portion of the network. The inventive method may be practiced using either conventional computer hardware and software or dedicated custom hardware such as a VLSI chip.
106 Citations
32 Claims
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1. A method for detecting high impedance faults on a power line, the steps comprising:
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a) sensing a plurality of cycles of currents attributable to a power line and generating a signal representative thereof; b) computing a first derivative of cycle-to-cycle maxima or minima of said current; c) transforming said derivatives into a frequency domain representation thereof, the power spectrum of which frequency domain representation being usable by means for processing information; d) applying said power spectrum to means for processing information using artificial intelligence techniques to detect a high-impedance fault and to generate a fault signal indicative thereof; and e) actuating a switch in response to said fault signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for detecting high impedance faults on a power line, comprising:
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a) providing a rules-driven expert system; b) sensing voltages and/or currents attributable to a line of a power distribution system and generating a signal representative thereof; c) computing a first derivative of cycle-to-cycle maxima or minima of said voltages and/or currents; d) mathematically preconditioning said signal; e) transforming said preconditioned signal representative of said line voltages and/or line currents into a frequency domain representation usable by said rules-driven expert system; f) applying said frequency domain representation to said expert system to detect a high-impedance fault and to generate a fault signal indicative thereof; and g) initiating an event in response to said fault signal. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for detecting high impedance faults on a power line, comprising:
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a) sensing a plurality of cycles of current attributable to a power line and generating a signal representative thereof; b) detecting changes in the cycle-to-cycle positive and negative peaks of the current waveform; and c) initiating an event only when said changes are detected; wherein the step (b) of detecting changes in the cycle-to-cycle positive and negative peaks of the current waveform comprises; i) computing a first derivative of cycle-to-cycle maxima or minima of said current; ii) transforming said derivatives into a frequency domain representation thereof, the power spectrum of which frequency domain representation being usable by means for processing information; and iii) applying said power spectrum to means for processing information using artificial intelligence techniques to detect a high-impedance fault and to generate a fault signal indicative thereof. - View Dependent Claims (24, 25, 26)
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27. A method for detecting high impedance faults on a power line, comprising:
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a) sensing a plurality of cycles of voltage attributable to a power line and generating signal representative thereof; b) detecting changes in the cycle-to-cycle positive and negative peaks of the voltage waveform; and c) initiating an event only when said changes are detected; wherein the step (b) of detecting changes in the cycle-to-cycle positive and negative peaks of the voltage waveform comprises; i) computing a first derivative of cycle-to-cycle maxima or minima of said voltage; ii) transforming said derivatives into a frequency domain representation thereof, the power spectrum of which frequency domain representation being usable by means for processing information; and iii) applying said power spectrum to means for processing information using artificial intelligence techniques to detect a high-impedance fault and to generate a fault signal indicative thereof. - View Dependent Claims (28, 29, 30, 31, 32)
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Specification