Fuji Electric Co., Ltd.

Takashi Hashimoto

Kiyoshi Tanigawa

Shoji Sasaki

Katsumi Watanabe

The earth leakage breaker of the invention includes a first comparator; a second comparator connected to the first comparator; a third comparator having a threshold higher than the threshold of the first comparator for distinguishing a leakage current from the grounding current caused by a lightning surge or by the heavy ground fault; a monostable multivibrator triggered by the output of the third comparator for forming a time gate of a predetermined period; a counter for detecting a pulse outputted from the first comparator to distinguish whether the grounding current is caused by the lightning surge or by the heavy ground fault; and a trip signal generator circuit for outputting a trip signal in the case of leakage and heavy ground fault. The earth leakage breaker facilitates avoiding unnecessary breaking of the impulsive grounding current caused by the lightning surge.

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Tochigi, Japan

Takashi Hashimoto