A Comprehensive Model for Electrical Degradation of Power Cable Insulation

The widely used cross-linked polyethylene (XLPE) cables for power distribution and transmission systems are subjected to a large number of stresses such as electrical, mechanical, chemical, environmental, and thermal stresses. Electrical stress is a phenomenon that significantly contributes to cable aging resulting in the reduction of its functionality. It is necessary to study the dielectric properties and their changes during the aging process to improve grid efficiency, stability, reliability. This paper proposes a comprehensive physical model to simulate and illustrate the electrical insulation degradation phenomenon in XLPE insulated medium voltage power cables. The statistical analysis of aging concerning the change in dielectric polarization is conducted to characterize XLPE insulation degradation in a 24 kV power cable. A three-dimensional finite-element analysis (FEA) cable model is developed in COMSOL Multiphysics software to illustrate the aging phenomenon. Six different cases with varying stress effects in the insulation region are evaluated and compared. Namely, the voltages stress on power cables when the progressive change in the electric polarization process in the insulation region takes place for a prolonged period. It also presents the electric polarization variation in the insulation region for different numbers of voids. The results of the study show the impact of the electric stress through the measurement of the polarization index in the insulation region.