Advanced 3D FEM Modeling for Thermal Management of Underground Cable Systems and Crossings

(3D) thermal pinch points (PP) that can significantly constrain cable ampacity. While traditional two-dimensional (2D) methods remain effective in some cases, they can mischaracterize thermal behavior where multiple crossings, limited separation, or deep installations are present.

This paper presents a repeatable 3D Finite Element Method (FEM) modeling framework to quantify these effects and evaluate mitigation strategies, including pumped dielectric fluid.

Seven real-world pinch points along three parallel 230 kV High Pressure Fluid Filled (HPFF) transmission circuits were analyzed using a progressive FEM workflow benchmarked against

CIGRE Technical Brochure (TB) 880 and extended to steady-state and transient 3D simulations. Results show that conductor upsizing provides the dominant ampacity benefit at most locations, while pumped fluid circulation produces measurable temperature reductions primarily in thermally saturated crossing clusters with closely spaced heat sources. In contrast, deep horizontal directional drilled (HDD) installations exhibited minimal benefit from circulation due to the absence of localized thermal hot spots.