Speedy Detection of Very High Resistance Faults During Power Swing

The dynamic changes in the power system may lead to severe power swing resulting in sustained oscillation in impedance seen by the distance relay. Malfunctioning of the relays in response to these events may trigger catastrophic failure which is utmost detrimental for power system stakeholders. Fast and accurate isolation of faulty circuit is one of the prime necessities to save the system from blackouts and maintain the system stability. In this paper, a novel exponential change of admittance based fault discrimination index (FDI) is proposed to detect all types of faults (symmetrical/ asymmetrical) during power swing. The proposed algorithm can be included in dual-use line relay (DULR) to have fast and accurate detection of the fault in presence of power swing. The proposed index has been tested with single machine infinite bus (SMIB) and WSCC 9-bus system for a large range of fault environment including variations in fault resistance (R_f), the distance of fault from relay location, power angle, and swing type (fast/slow). To prove the robustness of the index the response of the FDI in case of large load rejections and faults in series compensated lines has also been investigated. The simulated results confirm the proficiency of the proposed algorithm in detecting faults during power swing.