Detection of symmetrical fault and discrimination from power swing using MOPSVC approach

Abstract

Abstract Distance relay are designed with swing blocking/tripping logic to maintain reliable and secure operation of power system. To prevent this from happening, the relay is functioned with a power swing blocking (PSB) logic. However, ensuring proper detection to swing event requires to overcome from the dependable situation such as three-phase fault. The relay refuses to behave normally if both swing and three-phase fault occur simultaneously. Reliable setting is essential to generate trip/block command. Unsymmetrical faults are easily detected during the swing condition due to the presence of negative and zero sequence components, but such components are absent in the case of symmetrical/three-phase fault. As a result, symmetrical fault under blocking condition is unidentified many a times by the distance relay, arising security issues. To improve the relay operation during swing and symmetrical fault conditions, a MOPSVC (multiplication of positive sequence voltage and current) based index is developed in this work. The MOPSVC index helps to discern power swing from three-phase fault. To test the efficacy of the method, a 230 kV, 50 Hz two-area four machine system, and Indian Eastern Regional Grid (IERG) network are considered. Simulation task is conducted using EMTDC/PSCAD software. To investigate the performance of the proposed method, various swing phenomena, faults, CT saturation, switching transients, and the presence of noise cases are considered, and the results demonstrate the robustness of the proposed algorithm. Responses under stressed power system conditions are also investigated, and a report on comparisons with existing methods is provided. Simulated results confirm that the proposed algorithm can balance the dependability and security aspects of the protection logic.