Phase distance relaying for transmission systems

Distance Relays are widely used to protect transmission lines. However, due to underreaching and overreaching phenomena, there is a low precision in protection zone limits of distance relays. Thus, in this work, an extension of an existing state-of-the-art algorithm based in phase coordinates is proposed to increase the precision in zone protection limits. The proposed method uses the fault current to estimate the fault resistance and compensate the apparent impedance calculated. The equation development was done for phase-phase type faults. Comparative tests with state-of-the-art formulations verified the efficiency of the proposed method.