Study on sequence component based fault phase selector during power swings

For digital distance relays, in order to get the correct measuring impedance, phase selector is widely used to identify the fault phases first. However, when a fault occurs at the line during power system swings, the traditional sequence component based phase selector might not identify the fault phase correctly, which leads to mal-operation of distance relays. Therefore, how to improve the existing sequence component based phase selector, especially at the condition of power system swings, is crucial. The relationship between the relative phase and amplitude of the sequence component of various asymmetric faults is analyzed. An improved asymmetric fault phase selector during power swings is proposed according to the corresponding relationship between the zero, negative sequence current components and the asymmetric fault types. The simulation results have shown the effectiveness of the method under power swings. Combining with fault component phase selector in no power swing, this method can perfectly solve the phase selection problem of transmission lines.