On the Estimation of Life of Power Apparatus Insulation Under Combined Electrical and Thermal Stress

Results of combined electrical and thermal stress aging studies conducted on scaled-down models of rotating machine insulation are presented. In order to save time and cost, accelerated stress testing procedure with type II censoring is adopted. The service life of insulation is estimated by extrapolation. The model for aging used here is essentially a power law, the parameters of which are treated as temperature dependent. These parameters and their statistical variability have been evaluated using relevant statistical techniques.