HIGH-SPEED FAULT CURRENT DETECTION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a high-speed fault current detection circuit which can minimally suppress the possibility of malfunction with respect to a surge signal and in which trip control decision time is very short.SOLUTION: The high-speed fault current detection circuit includes: a current detection unit which outputs a current detection signal flowing in a power circuit; a first comparison circuit unit which compares the current detection signal with a prescribed reference current value and outputs a first output signal when the current detection signal is equal to or larger than the reference current value; a differentiator which differentiates the current detection signal and outputs a change rate of the current detection signal; a second comparison circuit unit which compares the change rate of the current detection signal with a prescribed reference change rate value and outputs a second output signal when the change rate of the current detection signal is equal to or lager than the reference change rate value; a third comparison circuit unit which compares the current detection signal with a prescribed current detection limit reference value 4 and outputs a third output signal 5 when the current detection signal is equal to or larger than the current detection limit reference value 4; and a trip determination unit which outputs a trip control signal 3 only when the first output signal and the second output signal are maintained to be received during a prescribed short time and the third output signal 5 is not received.