Models for insulation aging under electrical and thermal multistress

A review of the methods and models used in lifetime studies of solid insulators under single- and multiple-stress conditions is presented. The statistical methods used with this type of data are described briefly, including the two-parameter Weibull distribution and the log-normal distribution, which are the two distributions most frequently used in aging studies. Lifetime models under multiple stresses are discussed. In particular, several models under combined electrical and thermal stresses are presented and their applicability is analyzed and discussed. These include multistress models proposed by L. Simoni (1981, 1984) and T.S. Ramu (1985, 1987), both employing the inverse power law for electrical aging, the exponential model by B. Fallou (1979), the probabilistic model by G.C. Montanari (1989), and the physical model by J.-P. Crine (1989). Trends in the development of these models are discussed