Abstract: In order to study the heat transfer mechanism and combustion characteristics of 220 kV high-voltage cables fire, a full-scale fire experiment was carried out. The internal temperature distribution and combustion phenomenon were recorded, and the longitudinal temperature propagation progress of cable cores, cross-linked polyethylene (XLPE), filler materials and outer sheaths were analyzed. The results show that: there will be voids between the copper core and the extruded corrugated aluminum sheath during the combustion progress. After the high-voltage cable was heated, the heating response time of the inner copper core at different longitudinal positions is basically the same. In addition, in the heating stage of the cable, the average temperature gradient of the core, cross-linked polyethylene,filling material and outer sheath is 2.125,1.938, 1.688 and 1.375 ℃/cm respectively. In the continuous stage of the fire, due to the poor thermal conductivity of XLPE, with the increasing distance from the fire source, there is an obvious hysteresis phenomenon in the temperature change, and the average speed of combustion spread of XLPE is about 3.6 cm/min. The XLPE insulation part of the high-voltage cable will melt when heated, and will accumulate at the cable end. When its gravity is greater than the surface tension, it will form high-temperature molten droplets, which are easy to ignite the combustibles.

Key words: 220 kV high-voltage cable, cable fire, heat transfer, combustion characteristic