Risk-of-failure calculation accuracy

This paper presents a new method of risk-of-failure calculation for individual insulation at different stresses. The method gives some useful information about the choice of the parameters which are necessary in the simplified calculation. The analysis done on a significant number of cases provides a classification of various types of switching operations that have similar overvoltage distribution. The errors due only to the different simplification methods that were previously used can lead in some cases to a bad estimation of risk of failure evaluation. The purpose of this paper is that of comparing these simplified methods of calculation of risk, among them the well known IEC methods, with this newly designed method.