Fault phase selector on the weak feed backside of transmission line using voltage symmetrical components

The fact that the voltage vector on the weak feed backside and that at fault location have approximately the same directions on transmission lines motivates to analyze the relationships among the voltage sequence components for different faults, and to propose an efficient method to determine the fault phases. The voltage considered in the phase-selection criterion is the steady-state voltage at the location of the protection device without the abrupt discontinuous components, so that the proposed fault phase selector can be used during the whole period after the fault is encountered. The margin of the phase-angle is big enough to select the fault phases. The results of EMTP and physical simulations show that the selector can determine fault phases accurately and meet the requirement of phase-selection on the weak feed backside in a practical environment.