Thermal modelling of cables in conduits: (air gap consideration)

A distribution cable system in a conduit with specific dimensions and shape has been considered in this study. The main objective of this paper is to find out the effect of the size of the air gap surrounding the cable inside the conduit on the cable ampacity i.e. the heat dissipation from the cable through the soil. Because the air gap acts like an insulation material (low thermal conductivity) the amount of heat transfer from the cable to the surrounding media is reduced and heat could accumulate and cause breakdown of the cable if unreasonably loaded for a long time. Two approaches are used to solve the problem, computer modelling and laboratory tests.