Research on the new phase selector based on impedance measurement

In order to solve the misoperation problem of the traditional impedance based phase selector, a new method for phase selection in microprocessor based protective relay is presented in this paper. The relationship between the magnitude and phase angle of the phase impedance and the load impedance are used in this new method. The performance of this new phase selection method under different fault conditions such as high resistance ground fault, cross-country fault and fault in weak in-feed system are verified by the simulation tests. The simulation results show that this new method is suitable for using as the steady state phase selection element in the EHV transmission line protective relay.