Apparatus and method for ground fault detection and location in electrical systems
First Claim
1. A ground fault detection and location system comprising:
- a ground fault main unit, said ground fault main unit comprising a frequency generator, said frequency generator generating an oscillating ground current in a normally ungrounded circuit at a pre-determined target AC frequency;
a low-noise pre-amp;
a ground fault location apparatus, said ground fault location apparatus comprising;
a bandpass filter coupled to said low-noise pre-amp;
a bias floating ground coupled to said resonating capacitor and said bandpass filter;
a diode coupled to said bias floating ground;
a signal level display coupled to said diode;
a comparator with hysterisis coupled to said bandpass filter;
a low pass filter coupled to said bandpass filter and said comparator with hysterisis; and
an internal power supply;
a resonating capacitor coupled to said low-noise pre-amp, said resonating capacitor and said low-noise pre-amp being configured to amplify a current signal, thereby creating an amplified current signal;
a communication link coupling said frequency generator to said ground fault location apparatus; and
a current transformer, said current transformer being selectively coupled to said ground fault location apparatus, said current transformer monitoring said oscillating ground current and locating a ground fault by detecting said target AC frequency.
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Abstract
The present invention is implemented by deploying an enhanced ground fault detection and location apparatus and by using the apparatus in conjunction with specific circuit analysis methods, using the information generated by the ground fault detection and location apparatus. The ground fault detection and location apparatus comprises the functionality of a voltmeter, an ammeter, a frequency generator, and a variable power supply, thereby providing for a variety of signals and analyses to be performed on a unintentionally grounded circuit in an ungrounded AC or DC power distribution system. The apparatus includes a main unit and a remote unit, which may be a portable hand-held unit. In a first mode, the apparatus of the present invention can be used to detect ground faults. By switching to a second mode, the apparatus of the present invention can be used to locate ground faults. The methods of the present invention involve the generation of various signals by the main ground fault detection and location unit. The generated signals are introduced into the electrical distribution system and monitored by various means, including one or more remote units. By analyzing the system-level response to the generated signals, the specific location of the ground fault or faults can be more readily ascertained, thereby promoting rapid and efficient repair and recovery practices. The apparatus of the present invention may be implemented as a dedicated, permanent installation or as a temporary portable system. Additionally, the system may be implemented as an automatic computer-controlled ground fault location and detection system.
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Citations
18 Claims
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1. A ground fault detection and location system comprising:
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a ground fault main unit, said ground fault main unit comprising a frequency generator, said frequency generator generating an oscillating ground current in a normally ungrounded circuit at a pre-determined target AC frequency; a low-noise pre-amp; a ground fault location apparatus, said ground fault location apparatus comprising; a bandpass filter coupled to said low-noise pre-amp; a bias floating ground coupled to said resonating capacitor and said bandpass filter; a diode coupled to said bias floating ground; a signal level display coupled to said diode; a comparator with hysterisis coupled to said bandpass filter; a low pass filter coupled to said bandpass filter and said comparator with hysterisis; and an internal power supply; a resonating capacitor coupled to said low-noise pre-amp, said resonating capacitor and said low-noise pre-amp being configured to amplify a current signal, thereby creating an amplified current signal; a communication link coupling said frequency generator to said ground fault location apparatus; and a current transformer, said current transformer being selectively coupled to said ground fault location apparatus, said current transformer monitoring said oscillating ground current and locating a ground fault by detecting said target AC frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method comprising the steps of:
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detecting a ground fault in a normally ungrounded circuit; generating an oscillating current in said normally ungrounded circuit, said oscillating current being oscillated at a target AC frequency; connecting a current transformer to a ground fault location apparatus, said ground fault location apparatus comprising; a bandpass filter coupled to a low-noise pre-amp; a bias floating ground coupled to said resonating capacitor and said bandpass filter; a diode coupled to said bias floating ground; a signal level display coupled to said diode; a comparator with hysterisis coupled to said bandpass filter; a low pass filter coupled to said bandpass filter and said comparator with hysterisis; an internal power supply; and a resonating capacitor coupled to said low-noise pre-amp, said resonating capacitor and said low-noise pre-amp being configured to amplify a current signal, thereby creating an amplified current signal; and monitoring said oscillating current with said current transformer and locating said ground fault by detecting said amplified current signal. - View Dependent Claims (17, 18)
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Specification