Extended ground distance relaying with fault resistance compensation

Fault resistance introduces an error in traditional ground distance relay apparent impedance measurement process. If not accordingly considerated it produces primary protection zone underreach. Line asymmetry also affects relay operation producing overreaching. So due to these two aspects protection zone limits of ground distance relays present low precision. In order to increase these precision limits, a new protection algorithm is proposed. The proposed method is based in phase coordinates and uses a fault resistance estimate to develop the trip decision procedure. The estimation procedure uses one-terminal voltage and current data in an iterative process. The proposed algorithm results are compared to traditional ground distance relay for method validation.