In large-scale 2D finite element steady-state thermal models for underground cable ampacity calculations, where the lateral and lower boundaries are adiabatic, the ground surface may be represented by isothermal Dirichlet, convective Robin, or coupled convection–radiation conditions. In such cases, the soil temperature at depths significantly below the cables tends to be equal or to exceed the temperature of reference soil or air. This paper proposes a novel approach addressing this issue by dividing the native soil into two layers, introducing an effective thermal conductivity for the upper layer, and assuming distinct reference soil temperatures at the cable depth and at the lower bounda... More >

In the last decade, design engineers have been increasingly required to calculate the ampacities of cable lines using the finite element method (FEM) according to IEC TR 62095, especially for cases that cannot be solved analytically based on IEC 60287. In this regard, CIGRE Study Committee B1 noted in 2020 that there are many gaps in the technical report IEC TR 62095 and then published in 2025 a technical brochure. However, a certain number of those gaps still remained unaddressed. This paper proposes concrete solutions for addressing several gaps related to underground single-core power cables in trefoil formations. 110 kV single-core cables with cross-linked polyethylene insulation are con... More >