Cyclic Loading of Underground Cables Including the Variations of Backfill Soil Thermal Resistivity and Specific Heat With Temperature Variation

The aim of this paper is to calculate the temperature distribution of a cable conductor and the soil surrounding the cable under cyclic loading conditions, taking into account the formation of a drying zone in the backfill material. The thermal model of an underground cable is considered by using the IEC 60853-2 method, including the effects of the variations in temperature on the thermal resistivity and specific heat of the soil. The results are compared with IEC 60853-2 and thermoelectric equivalent method calculations. This study is done on eight sandy soil types as backfill materials, and calculations are carried out by using a 33-kVx cable. The results indicate that the modifications done on the IEC 60853-2 method are required to improve its capability to simulate the field conditions during load cycling of power cables.