High resistance ground fault protection
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United States of America Patent
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Oct 31, 1989
Grant Date -
N/A
app pub date -
Sep 7, 1988
filing date -
Sep 16, 1987
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A protection device for high resistance ground faults in a power network according to the invention has a fault detection principle which is based on an indirect study of non-harmonic frequency components of the phase currents. When such a fault has occurred, a considerable change of the energy contents of these frequencies arises. This change can be detected by a device according to the invention. If by comparison (4e) between digitized input signals (I') and a harmonic Fourier model (4d) of the same signals, i.e. generation of the residuals of the system, it is found that a difference exists, and if the corresponding loss function V.sub.N (4f) for a certain time exceeeds a lower limit value - all on condition that a zero sequence current (I.sub.O) exists - then there is a high resistance ground fault on any of the phases of the network.
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