Abstract: Tree-contact Single-phase-to-ground Fault (TSF) in distribution lines is prone to cause wildfire, which jeopardizes the safe operation of power systems. Aiming at the problems of insufficient field data of TSF, weak electrical characteristics of leakage current, and less proprietary model research, this paper builds a true-type test platform of TSF in 10 kV distribution network, and explores its ignition mechanism by analyzing the data of TSF phenomenon, vegetation temperature, leakage current and equivalent resistance value. Focusing on the heat accumulation phase before the TSF open fire drifting, a time-domain model of leakage current integrating vegetation size, moisture content and ambient temperature was developed. The correlation coefficient R2 between the simulated and measured RMS leakage current waveforms is verified to be 0.972 6, and the robustness and accuracy of the model is further verified by changing the initial test conditions (vegetation size, water content, and ambient temperature) and comparative analysis of the model. The research results lay a foundation for early failure identification of TSF, which is of great value for improving the prevention and control of wildfire.

Key words: Tree-contact Single-phase-to-ground Fault, leakage current, time domain model, forest fire prevention and control