FAULT CURRENT DETECTING CIRCUIT

摘要

A fault current detection circuit according to the invention comprises a primary current transformer that detects a current; a pair of secondary current transformers that convert a current detection signal into secondary conversion signals with a small current; a fault detection circuit section that determines whether or not a fault current occurs by comparing a current value according to a secondary conversion signal with a predetermined reference current value; a surge detection circuit section that determines whether or not a surge current occurs on the electric power circuit; and a trip determination unit that receives a fault detection signal and a surge detection signal, and generates a trip control signal when at least either one of the fault detection signal and the surge detection signal is received.