Unsynchronised fault-location technique for three-terminal lines

This study describes a new fault-location technique using negative-sequence voltage for three-terminal lines. The ratios between the negative-sequence voltage magnitudes measured at each terminal are utilised to first determine the faulted section and then to estimate the exact fault location within the section. Since the current data is not deployed, the influence of inherent errors of current transformers can be avoided. The proposed method can accurately locate the unbalanced faults, that is, single-phase-to-ground, double-phase-to-ground, and phase-to-phase faults, regardless of the fault resistance and pre-fault conditions and without any need to identify the fault type. The method requires only the negative-sequence reactance behind each terminal which can be estimated by the short-circuit analysis with an acceptable accuracy. Reliability and practicality of the proposed method make it an attractive option to include in numerical protective relays. Simulation experiments with different fault cases reveal the capability of the proposed method.