Electrical life threshold models for solid insulating materials subjected to electrical and multiple stresses. II. Probabilistic approach to generalized life models

For pt.I see ibid., vol.27, no.5, p.974-86 (1992). Probability distribution functions valid for solid insulating materials subjected to multiple electrical and thermal stresses, which show life lines tending towards electrical threshold, are presented. They are based on the Weibull distribution. The probabilistic life models are checked on the basis of the results of life tests performed on different insulating materials, i.e. XLPE, composite Nomex-Myler-Nomex, epoxy resin, and polyimide. They provide the estimates of failure time percentiles at selected probabilities and stress sao that life curves at fixed failure probabilities can be drawn. These models should help in the choice of compatible thermal and electrical stresses for the design of insulation systems, apparatus, and components.<>