THE DETECTION AND TRIP METHOD OF THE LEAKAGE CURRENT VIA AUTOMATIC AMPLIFIED VARIABLE DEVICE WITHOUT ZERO-PHASE SEQUENCE CURRENT TRANSFORMER

摘要

PURPOSE: A method is provided to detect a leakage current by directly using the output of a current transformer which is an existing current sensor. CONSTITUTION: An automatic amplification varying device outputs a uniform current signal according to the size of a current signal according to a current transformer. A buffer(200) buffs the amplified current signal of each phase. A filter(300) removes noise in the current signal. An adder-subtracter(400) adds and subtracts the current signal. A comparator(500) compares the size of the output signal with a set value. An operation time setting device delays the output signal generated in the comparator.