Ampacity of MV underground cables: The influence of soil thermal resistivity

The thermal capacity of Medium Voltage underground cables depends on several factors, which include type and depth of installation, ambient temperature and thermal resistivity of the soil. In this contest, the thermal resistivity of the soil plays an important role and it is very sensitive to several parameters, like soil moisture and salts contents. This means that the thermal resistivity may increase significantly along the route of the underground cable and in dependence with the different seasons of the year (meteorological conditions). Furthermore, as the moisture content of a soil increases its resistivity decreases.