Applying distance relay for voltage sag source detection

This paper proposes the application of distance relay information for a voltage sag source detection problem. It is found that the magnitude and angle of impedance before and after the sag event clearly indicate on which side of the power-quality (PQ) monitor, the sag source lies. The required information on impedance can be obtained by the PQ monitor using the estimates of distance relay at that point or applying the algorithm of such relay.