Importance

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Abstract

A device for detecting and isolating a downed conductor in a three-phase four-wire multi-grounded distribution system cooperates with a power supply protective device if the device has a breaking capacity less than the maximum prospective short-circuit current of the distribution line, and the device is installed at a lateral of the distribution line. The device comprises a current detecting device, a high-pass filter, a band-pass filter, two arcing ground fault current-detecting circuits, a first overcurrent-detecting circuit that delivers an output when the output current form the current detecting device exceeds a predetermined value, a second overcurrent-detecting circuit that detects an overcurrent exceeding the breaking capacity of the device which has a breaking capacity less than the maximum prospective short-circuit current of the distribution line, a no-voltage detecting circuit for sensing that the distribution line is not electrically charged, and a trip mechanism. This trip mechanism opens the device either when the no-voltage detecting circuit produces an output after the second overcurrent-detecting circuit produces an output or when any one or more of the arcing ground fault current-detecting circuits or the first overcurrent-detecting circuit produces an output while the second overcurrent-detecting circuit produces no output.

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First Claim