An experimental research platform for the impact of mountain fire on safe operation of 10 kV and 35 kV transmission lines is designed and established. Pine

straw and shrubs are burnt to simulate the mountain fire fault of 10 kV and 35 kV transmission lines

and the variation characteristics of three-phase voltage

conductor to ground leakage current and zero-sequence voltage of transmission lines under mountain fire are studied. The effects of flame height and flame width on the insulation of 10 kV transmission line are studied and analyzed too. The test results show that mountain fire can cause single-phasehigh resistance grounding and phase to phase short circuit of transmission line

which are the results of the joint action of voltage level

distance to ground

flame height

flame width and other factors

and whether the flame bridges the air gap is an important factor affecting air insulation. The phenomena that the transmission line discharges to the flame and the voltage of one phase affected by the flame is lower than that of other phases during the test are studied

and the causes and laws of mountain fire on 10 kV and 35 kV transmission lines are obtained.