Phase-to-ground fault location methods in unearthed sub-transmission networks: A review

This paper provides a coherent classification of the existing methods for phase-to-ground fault location in power sub-transmission networks operated with unearthed neutral. The theoretical background of every approach is briefly presented, specifying whether each method is applicable on-line or off-line. The analysis is mainly focused on comparing the limitations of the algorithms, especially concerning the general properties of the lines of a sub-transmission power system.