METHOD AND CIRCUIT ARRANGEMENT FOR THE DETECTION OF GROUND FAULTS ON ELECTRONIC TRIPS FOR LOW-VOLTAGE CIRCUIT BREAKERS COMPRISING SERIALLY CONNECTED MEASURING AMPLIFIERS

摘要

One problem during the detection of ground faults consists of the fact that the measuring amplifiers have a great amount of tolerance regarding the amplification factor thereof, resulting in a substantial error when errors are handled by means of software. According to the invention, the output signals of the measuring amplifiers are summed up phase by phase in a pulse-modulated manner in a summing amplifier. The duration of the pulses generated by the trip are controlled in accordance with the amplification factor of the respective associated measuring amplifier while the output of the summing amplifier represents a ground fault monitoring signal.