Patent ID: 6873508

Claim:
A protective relay system comprising: oscillation detection means for detecting an oscillation of a power system to perform a relay operation, based on an amount of electricity of the power system; negative-phase-sequence forward fault determination means for performing a relay operation during system faults between opposed terminals to be protected, based on a relationship in phase between a negative-phase-sequence voltage and a negative-phase-sequence current that are extracted from a voltage and a current of the power system; telecommunication means for transmitting/receiving a circuit breaker trip permissive signal between the opposed terminals to be protected; and circuit means for transmitting a circuit breaker trip permissive signal from one terminal of the opposed terminals to other terminal thereof through the telecommunication means when the oscillation detection means and the negative-phase-sequence forward fault determination means perform a relay operation and for giving a trip command to a circuit breaker at the one terminal when the one terminal receives a circuit breaker trip permissive signal from the other terminal.