Effect of Individual Sulfide on the Stability against Oxidation of Transformer Oil and Its Electrical Parameters

This study is devoted to the improvement of the transformer oil quality, using a new inhibiting additive, since the extensively used inhibitory additive ionol is sensitive to organosulfur compounds of sulfur oils. From the earlier works, the organosulfur compounds are known to affect ambiguously the transformer oils characteristics. Therefore, it was of interest to study the individual sulfides as the inhibitory additives. The goal was achieved by the researches with the use of the model mixtures consisting of the selectively purified transformer oil (free from ionol) along with the individual sulfides, decylcyclohexylsulfide and decylfenylsulfide, at concentration of 0.5 %, Their effect on stability against oxidation of the selectively purified oil, on its electric strength and tangent of the dielectric losses’ angle was studied. The primary results obtained were, firstly, the rate slowing down of water formation in oil and of water-soluble acids formation in oil upon its oxidation in the presence of the individual sulfides, and, secondly, an increase in the electric strength and decrease in the dielectric losses compared to the transformer oil, containing ionol. It was established that decylcyclohexylsulfide inhibitory properties are stronger compared to those of decylfenylsulfide, which was testified by less quantities (by 1.8 times) of the water formed and of water-soluble acids (by 2.22 times). The introduction to oil of 0.5 % decylcyclohexylsulfide and decylfenylsulfide increased the oil electric strength, correspondingly, by 2.6 and by 5.5 times, upon water concentration in oil equal to 15·10-2 g/kg. The significance of the results obtained is in improving the transformer oil quality produced from the sulfur oils with the use of a novel additive.