(1) insulation damage cause a short-circuit fault. Power cable protection cover lead was damaged during installation or in the operation of the cable insulation by mechanical damage, cause and cable or lead insulation breakdown between the skin and the arc made of insulating material and fire broke out on cable covering material.
(2) the cable long time overload running. Long time overload operation, the operating temperature of the cable insulation materials more than the allowable temperature, normal fever has dried up cable insulation aging, this kind of phenomenon of insulation aging dry, usually occurs in the cable on the road. Due to cable insulation aging dry insulation material loss or lower insulating performance and mechanical performance, and therefore easy to burning occurrence breakdown, and even the whole length along the cable fire broke out on several at the same time.
(3) the oil filled cable due to the difference in drip, leak. When the oil immersion cable laying elevation, cable drip oil phenomena may occur. As a result of the running stream cable upper dry due to the loss of oil, the part of the thermal resistance of the cable, make paper insulated coking and breakdown in advance.