Secured zone 3 protection during load encroachment using synchrophasor data

Abstract

Three-phase fault and load encroachment are balanced phenomena. A load encroachment function is incorporated in distance relay to improve the security of protection scheme, confuses with three-phase fault during high reactive loading condition. Zone 3 malfunction during such a situation often causes cascade line tripping leading to wide-area disturbance. In this work, voltage phasors of selected buses from a wide area measurement system (WAMS) are used to prevent zone 3 maloperation of a distance relaying scheme during load encroachment. The change in magnitude and phase of bus voltages are applied to discriminate three-phase fault from load encroachment. Performance of the proposed method is tested with New England 39 bus and IEEE 118 bus system simulated in EMTDC/PSCAD. Results show high accuracy as well as the speed of operation, is very fast of the proposed method.