How thermal conductivity of excavation materials affects the behavior of underground power cables

The necessity of dissipating properly the heat generated by underground power cables, due to the Joule effect, during the exertion phases is very important because the thermal stress in the insulating materials enveloping the cables must be avoided. This is why it is so important to investigate how the thermal resistivity of the soil surrounding the conductor affects the heat dissipation. Design engineers can make an estimation of this value through the IEC 287, a standard providing a simplified formula for this type of calculation (though it underestimates the problem since it does not take into consideration how complex the underground cable laying is). Thanks to the reproduction scale in the laboratory of an experimental apparatus, a 2D FEM model was validated for the investigation of those heat exchange problems affecting underground cables. This paper is the sequel of a previous article (about the influence of the geometrical parameter of the excavated area), written by the very same authors of this article, and it examines the influence of the thermal conductivity characterizing the different materials surrounding the cable and how it provides a dimensionless coefficient to correct the IEC formula.