Investigation of XLPE Power Cable Insulation Degradation Under Chemical, Electrical, and Mechanical Stress

High voltage (HV) power cables are exposed to various stresses, such as chemical, electrical, mechanical, and thermal. These stresses contribute to the eventual failure of electrical power cables in an unpredictable manner. Cross-linked polyethylene (XLPE) is an essential component of a power cable's insulation layers, and unwanted stresses negatively affect the insulation layers' performance in various ways. In this paper, three 3D Maxwell finite element analysis (FEA) models of a single core, 30 kV DC power cable are built to study the effects of chemical stress, electrical stress, and mechanical stress on the characteristics of polymer insulation material. The main parameter utilized for determining insulation health in this work is the polarization index. Temporal evolution in the polarization index is investigated, as aging-induced stresses degrade the XLPE's structure. The severity of chemical stress, electrical stress, and mechanical stress is estimated and compared based on the polarization index, with a focus on chemical stress, highlighting the severity of the deformation caused within the inner polymeric structure of XLPE. The severity is obtained for the innermost and outermost insulation layers. It was discovered that the insulation layer's proximity to the cable's core is the main factor influencing degradation. Moreover, the obtained results successfully demonstrate the polarization index's ability to detect degradation after the 95-day mark, indicated by the substantial increase in polarization index values, common between all stress types applied.