Gharehpetian - Elec. Eng. Department Amirkabir University of Technology Tehran ۱۵۹۱۴, Iran
Mohseni - Elec. Eng. Department University of Tehran Tehran ۱۴۳۹۹,Iran

This paper presents general and practical information about the most important thermal considerations of transformers. At the first part the main definitions about temperat ure- rise and its test have been described. Then the loading of the transformers beyond the nameplate rating has been presented. In the last part of the paper the aging of insulating materials and the loss of transformer life expectancy have been discussed.

Temp erature-rise, Hot-spot, Aging, Life expectancy, Transformer