Symmetrical Fault Detection of Distance Relay to prevent Cascade Tripping during Power Swing

Power System disturbances such as line switching, generator disconnection and sudden removal of faults may cause instability which lead to the power swing. Distance relay finds difficulty between symmetrical fault and power swing which causes undesired tripping of the transmission line. This paper proposes a new method Park's Transformation and Fast Fourier Transform algorithm which is used to differentiate between the three phase fault and power swing and also to support backup zone of distance relay. This technique is tested for normal and abnormal conditions with different load angles and fault locations in IEEE 14-bus system is simulated in MATLAB/Simulink. The Simulation results shows the ability to avoid unwanted tripping decision of relay quickly and precisely.