Methods of statistical dimensioning of the outdoor insulation with respect to polluted conditions

This paper reviews the main principles of the statistical dimensioning of outdoor insulation with respect to polluted conditions used in Russia. The theoretical basis of the statistical method is presented together with its verification by service experience. Examples of different practical applications of statistical dimensioning are given using the results of laboratory and field tests. Typical statistical parameters of the distribution functions of the flashover voltages and pollution parameters are derived for the areas with natural and industrial pollution. The principles of statistical dimensioning were recently applied in the new software programs, insulator selection tool (IST) and line performance estimator (LPE), developed at STRI (Sweden). The results of the statistical dimensioning using IST program show very good agreement with demands of the Russian guide for insulator selection. A few further practical applications of the IST program are described.