Modelling the thermal effect of solar radiation on the ampacity of a low voltage underground cable

Abstract

Compared with other underground cables, low voltage cables are most intensely heated by the sun due to the low laying depth. Accordingly, the main purpose of this paper is to show how the heat of solar radiation affects the ampacity of a 0.4 kV multi-core cable through different cool pavements at laying depths between 0.4 and 1.0 m where this effect is significant. The objectives of this study are as follows: (i) to simulate experimentally the effect of thermal emissivity of the cool pavement surface on the cable in known laboratory conditions, (ii) to express the effect of solar absorptivity of the cool pavement surface on the cable based on an analogy between the thermal effect of the laboratory interior and the thermal effect of outdoor solar radiation, and (iii) to simulate numerically the thermal effect of solar radiation using a large-size FEM-based model for the most unfavourable summer conditions and the most common winter conditions. All the defined objectives have been successfully met and it has been shown that the ampacity of the cable installed at a depth of 0.7 m can be increased up to 45% in summer and up to 12.1% in winter compared to the corresponding base cases.