CHT Prediction of Thermal State of Underground Conductor in Power Distribution Networks

Abstract

This research aims at a deeper understanding of the steady-state thermal behavior of underground cables using Computational Heat Transfer (CHT) techniques modeling. The results concern the thermal study of 33 kV single and multiple copper conductors with a nominal conductor cross-section of 615 mm2 buried in the ground for a single cable, two cables and for three cables in horizontal position. The most unfavorable summer conditions, the burial depth as well as the physical properties of the soil as a function of the moisture content, are studied. The operating current of the conductors is taken 940 A. The results show that the temperature of the cables decreases with the burial depth, a compromise temperature/cost of installation corresponds to 80 cm of burial depth. Further, the maximum temperature of a single cable buried in the ground is considerably lower than that allowed (363 K) for a good use, namely 313 K in summer conditions, so there is a considerable margin to increase its ampacity, also the temperature decrease with increase of water content of the soil surrounding the cable of approximately 2 to 5 degrees. The results obtained are in good agreement with those of the literature.