An active power filter for protective relaying at EHV line

Nonsinusoidal voltages and currents affect the performance of protective relays under normal as well as fault conditions. The intent of this paper is to present an active power filter for relaying operations. The active power filter provides harmonics-free voltage and current signals to the relay, thereby ensuring its designed performance. Combined shunt and series active power filters are used to filter out the voltage as well as current harmonics from the input signal to the relay. Simulation studies for a single phase to earth fault on a 220 kV transmission line have been presented.