Thermal analysis of underground electrical power cables buried in non-homogeneous soils

A numerical study based on a control-volume formulation of the finite-difference method is performed to determine the thermal resistance existing between an underground electrical power cable and the ground surface, assuming that the filling of the rectangular trench where the cable is buried consists of two superimposed horizontal layers of different materials, stacked above the cable bedding. A large number of numerical simulations have been executed for different values of the trench depth and width, the burial depth of the cable, the thicknesses of the two backfilling layers and the cable bedding, as well as their thermal conductivities and the thermal conductivity of the mother soil. A semi-empirical correlating equation much more reliable and efficient than the calculation method recommended in the International Standard IEC 60287 currently in use worldwide for the design of buried electrical power cables, has been derived by the application of a multiple regression procedure.