Overloading and loss-of-life assessment guidelines of oil-cooled transformers

Estimation of a power transformers' remaining life is of concern to most owners, especially when it is known to have been overloaded either continuously or intermittently over long periods. Therefore, to make economical decisions for transformer replacement, it is critical to be able to estimate with reasonable accuracy the transformer remaining life expectancy. This paper discusses, in detail, the insulation aging and life expectancy estimation of oil-filled transformers and provides simplified transformer overloading guidelines.