The role of micro-structural and mechanical properties in the framework of the model for damage inception and growth from air-filled voids in Polyethylene-based materials for HVDC cables

An innovative, physical, aging and life model for polymeric insulation systems, founded on damage inception and growth at the level of microscopic cavities, was developed previously by the authors. This paper is focused on the role played by micro-structural and mechanical properties (such as crystallinity and Young's modulus) in the framework of such model. These concepts are applied to the case of LDPE, HDPE and XLPE matrixes. The relevant estimates of damage growth rate and time-to-failure as a function of void size and applied electric field in typical working conditions for HVDC power cables are performed. The results show that, under the assumptions made, the crystallinity level itself does not seem to affect significantly the life times, while the mechanical characteristics of the investigated materials (accounted for via the Young's modulus) seem to have a non-negligible impact on damage growth rate and time-to-failure of the polymeric matrix.