Zero-sequence current blocking device for two phase AC systems

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 u
_k
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.