Abstract: In order to study whether the vegetation contacting with the low voltage distribution line fault will threaten the fire safety in the forest area, a 400 V overhead line vegetation touching the conductor fault simulation experimental platform was set up, common cedar and phoenix tail bamboo in the forest area were selected as typical vegetation samples, and in order to supplement experimental data, humulus and ivy were also added for the experiment. By analyzing the leakage current flowing through the vegetation during the fault, the temperature rise phenomenon of the vegetation and the charring traces on the surface of the vegetation, we study the possibility of ignition of low-voltage distribution lines in contact with different types of vegetation. The experimental study shows that: cedar contact single-phase conductor failure without obvious temperature rise phenomenon; high water content of the fenugreek contact single-phase conductor failure temperature rise obviously, there are obvious traces of charring near the fault point, the maximum temperature reaches 95.3 ℃, the maximum leakage current is 180 mA; the thermal effect of current accumulates at the fault point, causing the temperature in the area to rise and water to evaporate. With the reduction of water content, the effect of water evaporation on vegetation impedance gradually increases, resulting in a decrease in leakage current, and ultimately the temperature drops to room temperature, so the vegetation will not spontaneously combust or ignite nearby flammable materials through arcing, indicating that the failure of vegetation-touched single-phase conductor of low-voltage distribution line will not threaten the safety of fire prevention in the forest area. The special case of phoenixtailed bamboo across the two-phase conductor failure and humulus and ivy across the two-phase conductor failure temperature rise obviously, and accompanied by the phenomenon of discharge, under certain conditions can develop into a phase-to-phase short-circuit, short-circuit arcing ignition of flammable materials near the point of failure, threatening fire safety in the forest area. The results of the study are of great significance for the prevention of fires on low-voltage distribution lines through forested areas.

Key words: low voltage distribution lines, vegetation touching conductor faults, charring traces, phase-to-phase short circuits, ignition experiments