Life expectancy of high voltage electrical insulation under multi-factor ageing

The degradation mechanism in high voltage electrical insulation exposed to combination of stresses is complex, since the interaction between the factors of influence may accelerate the ageing. The paper reviews the present status of problem of prediction of life of Insulation under multi-factor ageing. Various aspects of approaches for prediction of life generally adopted have been outlined. Different physical models of failure mechanism have been touched upon. Importance of test conditions, end point criteria and parameters of spread of data is impressed upon for correlation of accelerated studies to normal operating conditions. Theoretical approach for prediction of life under multi-factor influences based on single factor data are detailed. Ageing studies conducted and planned in this direction and the typical data have also been presented