Numerical Model of the External Thermal Resistance of Underground Cables Buried in the Multi-layers Soil for Ampacity Calculation

This paper presents the application of the Adaptive Higher-Order Finite Element up to 9th - order for simulating the thermal field of underground cables system buried in the multi-layers soil in steady state. The aim of this task is to improve the estimation of the thermal resistance surrounding ducts of cables that is one of steps in ampacity calculation procedures. To demonstrate the high accuracy of this approach, it is firstly applied to solve a 2D heat benchmark problem with errors evaluation. Afterward, the proposed method is also tested on a real model of 110 kV high voltage cables line in Ho Chi Minh city, Vietnam. Moreover, the wrong formulas for modeling the heat convection boundary of the underground cables using the classical finite element analysis in some published papers have been corrected to help the readers can understand the solving problem more clearly in physical aspect.