Life expectancy of electrical insulation under multi-stress ageing

Ageing of high voltage insulation during operation takes place due to combined effect of electrical, mechanical, thermal and environmental stresses. For design of reliable insulation, therefore, it is necessary to evaluate life expectancy under conditions of multi-stress ageing. The total problem of life expectancy and reliability of insulation system essentially consists of its (a) calculation and forecasting (b) control and improvement. The present status of the solution of first aspect is characterized by efforts towards formulation of the correct physical models of failure of insulation in the wide range of testing conditions, including those near the working one´s mathematical analysis of the models and methods of testing.