A microprocessor-controlled variable impedance adaptive fault current limiter

The design and modeling of a microprocessor-controlled variable-impedance fault current limiter is described. The limiter consists of an LC series circuit tuned to be of minimum impedance at the supply frequency. A thyristor-controlled reactor is shunt connected across the capacitor. By varying the firing angle of a thyristor pair, the impedance of the limiter is varied to allow the necessary current limitation so that the system is protected and all circuit-breaker relays can operate. The fault current limiter is modeled using a digital computer and validated in the laboratory with a prototype test setup