Blocking the distance relay operation in third zone during power swing using polynomial curve fitting method

The power swing caused by various transient disturbances which exists only for a few seconds will affect the zone 3 distance relay behavior and may result in relay mal-operation. By improving the operation of zone 3 distance relays, it is possible to prevent mal-operations, so that the cascaded line tripping is avoided. This paper proposes a transient stability prediction based on polynomial curve fitting method. The novelty of the proposed method is that it accurately predicts the transient stability based on only few samples of fault data with solving computationally extensive electromechanical dynamics and also determine the optimal tripping time for zone 3 so that the relay will be block the tripping for stable power swings. Performance of the proposed scheme is evaluated on the IEEE 14 bus system and the results are presented in this paper.