| 摘要 |
PROBLEM TO BE SOLVED: To conduct shutdown operation by detecting tracking short-circuit, without causing malfunction by load current or rush current, even if a plurality of household electrical appliances are used concurrently. SOLUTION: In a determination circuit 5, current information of a cable run detected by a current transformer 1 and voltage information of the cable run, detected by a voltage detection circuit 3, are inputted. A calculation circuit 8 compares the peak value for each half period, determines it as tracking short- circuit if a condition, where the variance in the peak value exceeds 5 amperes in current and a voltage variance exceeds 5 volts occurs 10 times continuously, and outputs the operating current of a tripping circuit 7 from an output circuit 11, to make a tripping coil 6 operate and operate a contact 13.
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