Computation of underground cables series impedance using the finite element method

The study of electromagnetic transients in underground power cables requires an accurate knowledge of their electrical parameters over a wide frequency range. In this work, a methodology for frequency dependent underground cables series impedance is presented, using the Finite Element Method (FEM) by means of commercial software COMSOL Multiphysics 4.4®. The values obtained by numerical simulations are compared with analytical approximations proposed by Schelkunoff [1] and Saad et al. [2] for coaxial conductors impedance and earth return impedance, respectively. According to the results, it can be concluded that FEM is a practical tool for determining electrical parameters, with the advantage that this approach can be applied to any underground cables arrangement with complex geometries and even taking into account multi-layer soil.