Volumetric Power Density Distribution in Low Voltage Cables With Maxwell Equations and FEM Simulations

Air voids within cables insulated with cross-linked polyethylene (EPR) are identified as vulnerabilities due to their association with operational charges resulting from partial discharges. These voids generate intense and nonuniform electric fields, leading to an increase in dissipated power. Therefore, this work investigates the impact of voids in the conductor and insulating layers of three-phase cables. Simulations are carried out using COMSOL Multiphysics software based on the Finite Element Method (FEM). The research focuses on evaluating the behavior of electrical cables with copper and aluminum cores with inserted air voids. A voltage of 1 kV, frequency of 60 Hz with alternating current (ac), and a 120° phase shift are applied. In addition, an analytical solution based on Maxwell’s equations and Ampere’s law is developed for two cables of identical cylindrical geometry and a length of L =15 m for copper and aluminum cores. It was found that power cables with copper cores exhibit better conduction of volumetric power density, resulting in superior efficiency in the transmission of electrical energy in three-phase systems compared to aluminum power cables. However, under the effect of electric field accumulation, the present voids may rupture, triggering a series of detrimental phenomena to the functioning of the electrical system. Partial discharge activity is influenced by various factors, including applied voltage, shape, size, and location of voids, as well as the presence of small protrusions on the conductor surface. The results reveal an increase in volumetric power densities attributed to the presence of air voids, highlighting the significant influence of the voids’ location on the behavior and functionality of the electrical system during operation.