A Probabilistic Insulation Life Model for Combined Thermal-Electrical Srresses

The Weibull distribution is widely used in statistical problems related to aging of solid insulating materials subjected to electrical stress. The main object of this paper is to explain the Weibull probability function in such a way that it can be applied to the statistical analysis of the risk of failure for solid insulating materials or structures subjected to single or combined (in particular thermal-electrical) stress situations. For this purpose, appropriate expressions for the scale and shape parameters of the two-parameter Weibull function are proposed, starting from a model for combined-life, based on the inverse power model for electrical life and the Arrhenius relationship for thermal life. The agreement of the statistical model thus obtained has been verified by means of experimental tests carried out on Low-Density Polyethylene.