Device for preventing malfunction of ground fault protection relay and method for preventing malfunction

摘要

PROBLEM TO BE SOLVED: To provide a malfunction prevention device for a ground fault protection relay capable of preventing, in simple configuration, a malfunction of the ground fault protection relay caused by a neutral point unstable phenomenon without sacrificing responsiveness of unlocking of a lock signal for malfunction prevention, and a malfunction prevention method.SOLUTION: A malfunction prevention device 25 for a ground fault protection relay comprises: strength acquisition means which defines at least either a zero-phase voltage or a zero-phase current as a target electricity amount and acquires a first strength that is a strength of a fundamental wave component in the target electricity amount and a second strength that is a strength of a component in a frequency different from a fundamental wave in the target electricity amount extracted on the basis of a second frequency characteristic with a cross point between a first frequency characteristic for extracting the fundamental wave component and the second frequency characteristic; a comparison part 8 which outputs a lock signal when a magnitude relation of the first strength and the second strength satisfies a predetermined reference; and a lock part 9 which supplies a cutoff signal to a circuit breaker when the lock signal is not output, and stops supplying the cutoff signal to the circuit breaker when the lock signal is output.