Application of statistical methods to the design of solid insulation systems

Statistical methods involving the Weibull distribution and regression equations to estimate service life from voltage endurance tests are widely used by insulation system designers. This paper reviews the ways in which these methods are applied to the design of high voltage equipment such as cables and rotating machines. The most popular use of statistical methods is to aid in material selection, primarily through comparative tests. In a few cases, the apparent existence of a threshold electric stress, below which electrical aging will not occur, has been used to set a maximum design stress for cables. The credibility of the above applications depends on simple and objective techniques to estimate various statistical quantities. Unfortunately, not all the required statistical techniques have been developed by statisticians as yet. This will impede the wider application of statistical designs.