Influence of the surroundings and mainly of the soil on MV cable systems

The increase of the load of some Medium Voltage (MV) cables, due to, amongst other things, the development of decentralized production, brings up “new” issues. A practical case of failure in Belgian MV cable networks, highlighted the importance of the thermal characteristics of the soil around highly loaded cables. An analysis of the thermal physical parameters of three types of soil (backfill, sandy and “local soil” type) used around the Belgian cable networks was performed. In order to assure good heat evacuation during the life time of the cable, the characteristics of the soil around loaded MV cables, especially if a “local soil” is used, have to be defined by a set of parameters and not only by the thermal resistivity.