Abstract: The signal injection method is a common method for small current grounding fault line selection and fault location, and along with its wide application, its limitation appears obviously day by day. Based on the summary of the maturational theory and experience of predecessors, using the S injection method, the single phase grounding fault of 10kV distribution network was researched. Considering the influence of the transition resistance and the line length on line selection and the influence of the line length on the fault location effect comprehensively, using the PSCAD simulation, the disadvantages of S injection method for line selection and the effective length of the fault location were obtained.

Key words: small current grounding fault line selection, fault location, signal injection method (S injection method), transition resistance, line length