The Influence of Transformer Oil Aging to Dielectric Dissipation Factor and Its Insulating Lifetime

The transformer oil was thermal aged at 115degC by opened-cup deterioration method (GB7599 standard), using infrared spectroscopy analyzed thermal aging of transformer oil, according to absorption peaks, absorption strong and changes of absorption figures to judge the change trend of functional group during oil aging . For evaluating the lifetime of transformer oil model, a constant-stress test was used in accelerated life tests, and inverse power model was used to fit test data´s and calculated voltage endurance coefficients for the mean lifetime. The results show that the aldehyde and the acids compounds are produced in aging; The dielectric dissipation factor (tgdelta) becomes the logarithm relation with acid number. The partial discharge (PD) has immediately effect on the electricity aging life of transformer oil, along with the electrical aging, its dielectric dissipation factor increases gradually.