Prony method implementation in distance relays to mitigate the effect of series-compensated transmission lines

This paper characterizes the error in distance relay operation due to the existence of asynchronous frequency components when a fault in a line with series compensation occurs. The distance relay model and the impact of non-filtered frequency components using the conventional digital filters is presented, an error will appear in voltage and current fundamental frequency phasors estimation and, by consequence an error, in apparent impedance estimation. Then, the proposed distance relay algorithm using the Prony method as a filter and its application considerations are described. Next, the line series compensation effects in distance relay estimation are presented, showing the importance of the estimation of the fundamental frequency phasor. Afterward, the effect of series compensation in distance relay performance is characterized by evaluating a simulated fault event. Finally, the proposed algorithm is evaluated in reach and operation time of the simulated and real fault events using a 3D operation characteristic of the relay.