Fast orthogonal search approach for distance protection of transmission lines

A distance protection scheme for transmission lines based on analyzing the measured voltage and current signals at the relay location using fast orthogonal search (FOS) is presented in this paper. FOS has the ability to accurately provide fast estimate of the voltage and current fundamental frequency phasors that are required for a digital distance relay. Compared to the conventional FFT, FOS can estimate the fundamental phasors with higher accuracy and less number of samples. The proposed scheme has been tested on a transmission line model to verify the merit of this approach. The tests presented include solid ground faults, phase faults, and high impedance faults at different fault locations and loading conditions. The proposed scheme can classify all fault cases in less than one cycle after the inception of the faults.