ENHANCING THE PERFORMANCE OF DISTANCE PROTECTION DURING POWER SWING

Abstract

Power swing is a transient phenomenon arises due to several reasons including line switching, line outage, sudden load increment or decrement, faults, etc. Unnecessary tripping during power swing and unnecessary blocking for faults occurring during power swing result in distance relay mal-operation. This thesis introduced two schemes for supervising distance relays during swings and throughout faults during swings at different fault conditions including high impedance faults. The schemes rely on constructing a locus diagram for the current and voltage differences between the two ends of the protected line using phasor measuring units. The schemes only calculate two mathematical features, the length of semi-major and semi-minor axes for each locus. The applied threshold values for the schemes are calculated depending on the ellipse circumference and the rate of change of ellipse circumference during fast power swing respectively. The achieved results proved that the proposed schemes are immune to fault inception angles and slip frequencies in different locations of zone-1 and zone-2 of distance relays, while the maximum detection time of the algorithm was 4 ms and with a communication latency of 50 milliseconds using 4G technology. The proposed schemes ensure salient features for detecting fault cases with adequate speed and approved their superiority over conventional algorithms.