Monitoring phase faults of three-phase AC mains for establishing zero passages

摘要

The method for monitoring phase faults includes determining the zero passages of the phase voltages of the respective phases. The zero passage signals are evaluated for producing a pulse sequence used for the monitoring. The intersection points respectively between the two-phase voltages are determined and are also used as intersection point signals for forming the pulse sequence. The level condition of the pulse sequence alters respectively, by the changing successive zero point signals and intersection point signals. A time expiry is started dependent on each pulse or specified pulses. With a faultless three-phase network the time expiry course is stopped within a specified time. With the reaching or exceeding of the specified time, a fault signal is transmitted.