Effects of Backfilling on Cable Ampacity Analyzed With the Finite Element Method

Expressions for computing the external thermal resistance (T
₄
) of buried cables, in both the IEEE and the IEC standards, are applicable to a limited number of installation geometries. In this paper, a method for the computation of T
₄
using the finite element approach is presented. With this method, a parametric study on how cable ampacity is affected by different configurations of the backfills is performed. The obtained results are compared with those of the IEC and IEEE standards (Neher-McGrath) and published extensions by El-Kady and Horrocks. Important differences can be observed for nonstandardized situations.