Overheating of Underground Power Cable Line Due to Its Partial Exposition to Solar Radiation

Current-carrying capacity of underground power cable lines depends, among others, on thermal resistivity of the soil and cables layout: trefoil formation, flat formation with or without spacing. If conditions for heat transfer in the ground are favorable, the current-carrying capacity is relatively high. Therefore, it generates risk of the power cables overheating, if part of the cable line is located vertically in the air, to be connected with an overhead power line at its pole. Risk of the overheating is very high especially during strong solar radiation. The maximum permissible cable load for underground thermal condition is too optimistic for part of the cable line placed in the air. This paper presents computer modelling and simulations of thermal conditions of an underground low-voltage cable line, which part is located at the pole of the overhead line. Results of simulations indicate that part of the cables in the air can be strongly overheated.