Device for monitoring fault in closed alternate current circuit of protection device, has generation unit for comparing integrated current measurement signal with predetermined threshold level and for generating trigger signal

摘要

The device (10) has an evaluation unit (12) for generating a trigger signal (13) to trigger security function and comprising a filter unit (14). An integration device (16) generates an integrated current measuring signal (17) in a frequency range outside a fundamental mode of alternate current (AC) line frequency. A comparison and trigger signal generation unit (18) compares the integrated current measurement signal with a predetermined threshold level (19) and generates the trigger signal when the measurement signal exceeds the threshold level. Independent claims are also included for the following: (1) a protection device for protecting an electrical AC circuit (2) a method for monitoring fault in a closed AC circuit.