| 摘要 |
PURPOSE: A circuit for preventing surge operation error of leakage current breaker is provided to prevent an operation error of leakage current breaker due to a lightning by discriminating a lasting leakage current from a temporary surge voltage to operate a trip coil in case a leakage current detection signal is generated. CONSTITUTION: A power line(10a,10b) passes through a zero phase current transformer(16). A secondary voltage of the zero phase current transformer(16) is induced in case a leakage current is generated, and transformed into a voltage by a resistance(R1). A detection comparator(26) compares the detection voltage permitted through a low pass filter(24) with a threshold voltage, and permits the detection voltage to an integrator(28) and to an input tab of an AND-gate(AND2) if the detection voltage is higher than the threshold voltage. A latch circuit(32) operates in case the voltage permitted through a delay circuit(30) is higher than an input threshold voltage of the latch circuit(32), and the output operates as a logic input of an AND-gate(AND1) for operating an SCR(silicon control rectifier) driving circuit(36). A circuit which consists of one shot timer(34) and the AND-gate(AND1,AND2) discriminates whether or not the detection voltage output from the detection comparator(26) is a temporary surge signal. The SCR driving circuit(36) triggers an SCR and a trip coil(12) trips a trip switch(12a).
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