A review on power swing blocking schemes of distance relay during stable power swings

Abstract

Distance relays operate very fast compare to over current relays against faults to protect the transmission lines. Besides faults, distance relays can also operate due to power swings, it would be treated as relay maloperation. This maltripping of distance relays may lead to severe blackouts. So, primary requirement is to differentiate the short circuit fault and the stable power swing and need to block the mho type distance relay operation when the power swing is stable and unblock the distance relay operation when the power swing is unstable. This review paper discusses about different Power Swing Blocking (PSB) proposed schemes used for detecting and blocking the operation of relay when the power swing is stable and to avoid maltripping of the relays and severe blackouts. Comparison is made among different PSB schemes.