Thermal analyses of high voltage underground cables

Current carrying capacities of high voltage underground cables are calculated by performing thermal analyses. In thermal analyses, carried current value at the highest allowed temperature for the cable insulation is determined. In this thesis, the thermal analyses of high voltage underground cables are realized by finite element method and current carrying capacities are calculated for different ambient conditions and installation formats. Thermal analyses are performed for different ranges of parameters as the thermal conductivity of bedding material, the temperature of ground surface, the burial depth of cables, the convective heat transfer coefficient, soil thermal conductivity, pipe diameter and pipe wall thickness, later current carrying capacity is calculated according to the volumetric heat generation in the conductor. The effects of the types of screens as horizontal, reverse-U and closed that are made of copper, aluminum and structural steel on cable temperature are determined for different screen thicknesses and different distances between cable and screen in the cases of direct-buried and with pipe. And current carrying capacity values are calculated again in accordance with such conditions. Ampacity analyses are performed with IEC-60287 standard and finite element method for different clearances between cables and different thermal conductivity values of bedding material. In the case of using bedding material, significant differences that can be occurred between the two methods is observed. In the results chapter, analyzed laying conditions and ambient parameters for high voltage underground cable system are evaluated and the obtained results are given with offering suggestions.