The combined effects of thermal aging and short-circuit stresses on transformer life

An experimental program involving small turn segment models demonstrated the inter-related effects of thermal aging and mechanical stressing on the integrity of transformer conductor insulation. The experimental data was used to develop mathematical relationships between insulation wear life and the thermal and mechanical parameters which influence it. While modeling limitations preclude the use of these relationships for absolute life predictions without further correlating experiments on larger transformer-like structures, the relationships can be applied on a relative basis to answer questions about loading guides and practices and about effects of different magnitudes and numbers of short-circults. Examples of such applications have been given and discussed.