Investigating the Effect of Convection on the Rating of Buried Cables Using the Finite Element Method

This paper presents the effect of convection heat flow across the ground surface on the thermal rating of three single-core, 132kV, XLPE cables buried underground. The cable was modelled for thermal analysis using the Finite Element Method (FEM). This study demonstrates the use of FEM to investigate the effect of convection on the rating of buried cables in flat formations using QuickField Finite Element Simulation software under steady-state heat transfer analysis. As a result, developing a model to simulate this type of situation necessitates important considerations such as the following boundary conditions: burial depth, soil thermal resistivity, and soil temperature, which play an important role in the simulation's accuracy and reliability. The results show that when the ground surface is taken as a convection interface, the conductor temperature rises and may exceed the maximum permissible temperature when rated current flows. This is because the ground surface acts as a convection interface between the soil and the air (fluid). This result correlates when compared with the results obtained using the IEC60287 analytical method, which is based on the condition that the ground surface is an isotherm.