Setting frequency relays and voltage relays to protect synchronous distributed generators against islanding and abnormal frequencies and voltages

Abstract

This study concerns frequency relays and voltage relays applied to the protection of synchronous distributed generators operating in reactive power control mode without a frequency regulation function. The effect of active and reactive powers combination, load power factor, and reactive power imbalance are investigated for their implication for the anti-islanding setting of the frequency relay. Results reveal that the effect of these factors must be considered when setting the relay for islanding detection. For the voltage relay, results reveal that the effect of active and reactive powers combination, load power factor, and active power imbalance must be considered when setting the relay for islanding detection. The effect of multi-stage tripping on the frequency relay ability to detect island was also investigated. Results show that multistage tripping can improve the anti-islanding performance of the frequency relay.