Adaptive Distance Relay Based on Estimation And Update of Two-Port Equivalent Across Transmission Lines

Apparent impedance measured by a distance relay during fault matches the impedance of the faulted line segment for bolted faults. However, it is not so for resistive faults wherein the effect of infeed from the remote end also influences the measured impedance. It depends on the prevalent pre-fault two-port equivalent across the protected line. In this paper, we propose adapting zone-1 characteristics of the distance relay by estimating and updating the two-port equivalent. The paper presents methods for estimating and updating the equivalent model which predominantly utilize measurements available locally at the relay station. It is also envisaged that based on these estimations, the power swing blinder position/timer settings can also be adapted. The proposed method is illustrated based on the IEEE 39 bus test system.