Investigation of using dynamic phasors for improving the speed of distance protection

Abstract

The application of dynamic phasors (DPs) in overhead line protection was investigated. Equations to estimate the fault loop inductance and resistance were derived using the principles of DPs. A systematic amplitude comparator-based line distance protection scheme was developed using the equations derived to estimate the fault loop inductance and resistance. A least-squares-based DP extraction method that mitigates the effect of decaying dc components was used to extract the DPs and their derivatives from time-domain signals. The performance of the algorithm was investigated using a power system simulated in PSCAD/EMTDC. Testing under different fault scenarios with different fault locations, fault resistance, and fault inception angles showed that the proposed line distance protection scheme is capable of operating successfully for forward and reverse faults, short circuits and high impedance faults, evolving fault conditions, and under a wide range of source impedance ratios. The operating time of the proposed scheme was compared with the standard quadrilateral relay, and the results showed that the operating times of the proposed scheme are faster for close-in phase-to-ground faults but not significantly improved for phase-to-phase and three-phase faults compared to the standard quadrilateral distance relay.