Abstract: In recent years there have been numerous wildfire disasters caused by various factors, which have seriously affected the safe operation of overhead distribution lines. For single-phase ground faults caused by wildfire fire plume, we designed and constructed an experimental platform for fire plume breakdown characteristics as well as a simulation platform for wildfires in 10 kV and 35 kV distribution networks, studied the breakdown voltage characteristics of fire plume, the characteristics of leakage currents through the fire plume, and the characteristics of fire plume impedance under different vegetation types and different spacing, and analyzed the mechanism of the different fire plume electrical characteristics. The study shows that the lowest average breakdown voltage of the fire plume under the overhead line does not appear in the flame height at the highest stage, but appears in the flame bridging line and the flame height decreases in the stage; capacitance current has no significant effect on the amplitude of the leakage current flowing through the fire plume before the arc discharge; the fire plume transient impedance before the arc discharge shows a decreasing trend in general. The research in this paper can provide a reference for early warning of wildfire accidents under overhead distribution lines as well as for post-disaster accident cause determination.

Key words: overhead line, wildfires, breakdown voltage, leakage current, fire plume impedance, impact mechanisms