Adaptive distance relay during voltage collapse

This paper presents a new technique to prevent the false distance relay tripping during voltage instability and voltage collapse by integrating the adaptive setting of zone 3 distance relay, rate of change of voltage (dV/dt) and voltage stability index (VSI). The existing dV dt approach is not able to differentiate between a fault and near voltage collapse condition and may initiate the false tripping signal. Therefore, a rigorous indicator, VSI is proposed as an additional relay feature to prevent such signals to be initiated. The performance of proposed technique is evaluated by comparing it with the dv/dt and the combination of dv/dt with system status indicator (SSI).