Power swing blocking (PSB) function for distance relay using prediction technique

Abstract

Power swing leads to mis-operation of distance relays due to variations in system current (I) and voltage (V) magnitudes. PSB function is crucial to distinguish power swing and fault properly and prevent relay pickup during power swings to avoid unintended outage of the transmission lines. Moreover, the relay should initiate trip command in case of fault during power swing. This paper introduces a prediction based PSB function to block the relay operation during power swing and also to unblock it in case of occurrence of a fault during power swing. This method predicts current and voltage samples during power swing using auto-regression technique and subsequently calculates the predicted impedance observed by the distance relay (V/I). Blocking is invoked if predicted impedance is inside the distance relay protection zones. The differential components computed using actual and predicted values are used to detect fault in the transmission system. The proposed method is tested for two-area four-machine power system and compared with available methods.