Effect of electrical discharge on oil decaying process

Since the electrical stress is unavoidable in power transformers, the ability of oil to resist decomposition under electrical stress is of paramount importance for the safety of these important devices. Electrical stress together with heat and moisture, in the presence of oxygen, oxidises the oil producing free radicals, acids and sludge that are deleterious to the transformer. In this paper, the effect of electrical discharges on oil properties is reported. The results indicate that the quality of oil is considerably affected, with increasing voltage stress. Comparing oil properties before and after voltage application allow assessing the outcome of random secondary chemical reactions between large oil born free radicals.