Aging behaviour of cross-linked polyethylene (XLPE) as an insulating material for high (HV)- and extra-high voltage cables (EHV)

The objective of this paper is the scientific investigation of the electrical long-time response of XLPE-insulation. The electrical XLPE-insulation system is susceptible to aging when subjected to the thermal, electrical, environmental and mechanical stresses experienced under service conditions. Based on extensive experimental research work concerning the breakdown behaviour of XLPE, it is shown in this paper that beyond the statistical history, space charge processes contribute to the AC dielectric strength decrease of thick-walled XLPE-insulation. Values for the AC breakdown strength from long time tests on a cable model and 2 real cables are given and an example for calculation with approximation methods, to compare the values, is carried out. Weibull statistical analysis of area and volume effects on the breakdown strength in XLPE, for a coaxial cylindrical electrode configuration, is examined.