Inhibition technique of transformer insulating oil degradation - evaluation of the effectiveness of oxidation degradation inhibitors

To operate power transformers long-term, as well as ensuring their insulating reliability, an adequate study must be conducted on the age-related decline of various insulating oil characteristics and the method to inhibit the same. Accordingly, in the present study, 1,2,3-benzotriazole (BTA) and 2,6-dibutyl-4-methylphenol (DBPC), which are expected to be effective in preventing oxidation degradation, were added to the test oil and an accelerated degradation test was conducted to examine their effect. Consequently, for new oil, an deactivating effect on copper by the addition of BTA was confirmed and the ability to prevent the decline in characteristics caused by the degradation of the dissipation factor and volume resistivity could be observed. For aged field oil, however, the effect was less than that for new oil. Since phenol compounds structurally similar to DBPC may have been present in aged field oil, a study was conducted on the increasing tendency of concentration and saponification value of the former. As a result, it emerged that the presence of phenol compounds inhibited the increase in the saponification value and boosted oxidation degradation inhibition, even if BTA or DBPC had not been added. Based on the above results, it was clarified that, where an oxidation degradation inhibitor was added or structurally similar compounds were contained, an inhibitory effect on the aging of insulating oil could be obtained.