Review of the fault location methods for phase-to-ground short circuits in unearthed sub-transmission networks

This paper provides a coherent classification of the existing methods for phase-toground fault location in power sub-transmission networks operated with unearthed neutral. The theoretical background of each approach is briefly presented, specifying whether a method is suitable for on-line or off-line applications. The analysis is mainly focused on comparing the limitations of the algorithms, especially concerning the general properties of the lines of a subtransmission power system. The aim of authors is to present an overview of the existing approaches in literature by identifying five method categories, i.e. signal injection method, impedance-based method, travelling wave method, fault transient analysis method and composite location method. The main pros and cons of each method are described in order to give the reader a useful guide to identify the better fault location procedure, on the basis of the user own needs.