Zero-sequence current blocking device for two phase AC systems

Abstract

Resonantly grounded power systems require fault current limitation in order to meet current standards and to ensure personal safety. A current limiting transformer (CLT), based on an isolating transformer, is investigated here. The major advantages of CLT, compared to an isolating transformer, are power derating, reduction of uk value and thus reduced losses and reactive power demand during service. MATLAB/Simulink® is used to investigate the electrical behavior of CLT. Simulations of a phase-to-ground fault are made to proof the reduction of fault currents by CLT. Modelling CLT in symmetric components shows the blocking mechanism of the zero-sequence currents. In this context special attention has to be paid to resonant currents in resonantly grounded networks, when using CLT.