Impact of Service Life Duration on Electric Losses in Power Transformers: An Analytical Review

Transformers of metal plants include numerous devices past their rater service life. Their ongoing operation is made possible by regular maintenance and backup. Defining the transformer replacement sequence is a relevant problem due to the high costs of such equipment. Another important problem is cutting electricity losses depending on the actual efficiency that reduces over the long service life. In the majority of papers, the transformer power parameter data is based on the no-load and short-circuit losses calculated using the rated values. These parameters change over time, thus, such calculations cannot be accurate. The authors suggest an efficiency assessment method based on experimental measurements and calculations using the obtained results. An experiment was conducted to assess the electric losses in the transformer that has been in operation for over 55 years. An increased steel loss and a 0.5% efficiency reduction were confirmed, which are not critical. Accounting for the electric loss changes is deemed feasible when the service life of a transformer is over 20 years. To prolong the service life, the authors suggest using online technical condition monitoring systems.