Temperature field around underground power cable for dry and saturated conditions under static and cyclic thermal loads

Abstract

The safe operation of underground power cables is limited by the temperature of insulation around the conductor which heats up due to joule heating. The insulation temperature depends on the seasonal and diurnal power demand and variations in the surrounding soil’s moisture content. The previous scientific investigations are limited to theoretical and numerical analyses for cyclic loads and experimental studies for only dry conditions with static thermal loads. In this study, a series of large-scale laboratory tests are performed for static and cyclic thermal loads with dry and saturated sand. The cyclic thermal loads with symmetrical and unsymmetrical heating-cooling times are done with dry sand, which is the worst-case scenario for heat dissipation. The cyclic thermal loading on dry sand shows strong thermal charging and is higher with a shorter relaxation time. The static thermal loading results show a significant improvement in the heat dissipation ability with saturated sand due to higher thermal conductivity. However, the heat transfer with saturated sand suggests a strong convection cell formation after three days of heating above the heater. The channelisation of heat with convection cell sand facilitates cooling but is not desirable for power cables below crop fields.