Preventing Maloperation of Distance Protection due to CCVT Transients

Unsecured operation of backup distance relay during an external fault results in removing a needed energy link and can jeopardise overall system stability. This problem that is well known as distance relay overreach is very likely during coupling capacitor voltage transformer (CCVT) transients mainly under high system impedance ratio (SIR) conditions. To tackle this challenging problem, a new methodology consisting of three stages is proposed in this study. It is capable of solving the overreaching problem which occurs under high SIR conditions, without sacrificing the operation speed of distance relay for inside the first zone faults. Comprehensive simulation studies are carried out to test the proposed methodology. The obtained results demonstrate its feasibility and effectiveness for practical applications in the power system.