Analysis of Mechanical Stress Degradation of Medium Voltage Cable Insulation

MV cables are widely used to deliver electrical power from a transmission system to the consumers. XLPE (Cross-Linked Polyethylene) is the most common material used for cables insulation due to its excellent dielectric and mechanical properties. The XLPE cables are exposed to different types of stresses that impacts their functionality. Under elevated temperature conditions, thermal expansion in the insulation region can contribute to the development of mechanical stress. Mechanical stress greatly affects the performance of the cable and can contribute to faster aging when exposed for a prolonged period. Presence of voids or impurities can accentuate the impact of mechanical stress due to a reduction in the dielectric properties of the insulation. This paper provides a brief review of the phenomenon of mechanical stress due to severe thermal conditions and its impact on the different mechanical properties of the cable. The paper also illustrates the cable insulation properties for different number of voids in the insulation region. Finite Element Analysis (FEA) technique on COMSOL multiphysics software is used in this study. The paper will illustrate the correlation between the tensile stress in the insulation region and the aging time with regards to the increase in the number of voids. The study provides thermo-mechanical stress distribution of the cable and the influence of mechanical stress on the cable functionality.