Transient Regime to Support Steady State Directional Function in Presence of Strong Capacitive Currents in Compensated MV Systems

An SLG fault detection task can be out of reach of steady state methods, based on detection of active component in faulty currents. Efficiency of these methods may not be assured when strong capacitive currents on faulty feeder squeeze the phase shift between the faulty and the sound zero sequence currents below actual acquisition limits. Then the way to assure the directional decision is to exploit data recorded in transient regime, where an apparent phase difference is more important than actual phase difference in steady state. This is a consequence of the way the transient regime develops, beginning just after the fault inception with phase opposition between the faulty and the sound current residuals and finishing in steady state with a slight phase advance of the faulty residual over all the sound ones.