High resistant earth fault occurs frequently in resonant grounding systems

and is difficult to detect. The existing transient analysis and transient faulty section location method is not suitable for high resistance earth fault. The unique role of parallel resonance between Peterson coil and system capacitance to ground is used. The variation laws of zero-sequence current

zero-sequence voltage and their transient components are analyzed in under-damping and over-damping resonant processes. The facts can be observed in this study that the transient currents of downstream fault points of detecting point are approximately orthogonal to the transient zero-sequence voltage

and the transient currents of upstream fault points of detecting point include transient current at the fault point proportional to the magnitude of the transient voltage. The fault information collected by the synchronous measurement unit is used to calculate the projection components of transient current on transient voltage in every detecting point. If the difference in current projection magnitudes between two adjacent detecting points is larger than the preset number

this section could be located as the fault section. Otherwise

the downstream last detecting point is the fault section. The proposed method is intended to perfect the fault transient analysis and faulty section location technology in non-solidly earthed network. The feasibility of the method is verified by simulation. This work is supported by National Natural Science Foundation of China(No. 51477184)

National High Technology Research and Development Program of China(863 Program)(No. 2014AA051901)and State Grid Corporation of China(No. 52130416000D).