An investigation into the operation life of transformers

This paper presents results of a study on solid insulation aging of a number of oil-immersed power transformers, some of them have operated for more than 40 years. The contents of furfurol were measured, in addition to that of dissolved gases in transformer oil, by applying the HPLC method. Based on measured data and the traditional theory of solid insulation aging, it is suggested that the aging of solid insulation in these transformers is not serious even after 50 years´ of continued operation, because there has been no local overheating or sustained transformer overload during their operation.