Quantitative characterization of the sulfur-corrosion reaction

According to the statistics of power utility, a great number of large transformers and shunt reactors failed due to the corrosive sulfur in the insulating mineral oil. The issue takes places because the corrosive sulfur reacts with copper conductors and silver contacts, resulting in the formation of metal sulfides which can contaminate the insulating paper. In order to study quantitative characterization mechanism of sulfur corrosion reaction, a series of accelerated aging tests were carried out on corrosive oil sample which had operated for 6 years, and made a comparison with 25# transformer fresh oil. By testing the total sulfur concentration and oil weight of the aging transformer oil samples, the absolute content of sulfur in oil increases with the aging time, indicating that sulfur comes into the oil with insulating paper splitting, increasing the total sulfur concentration. A new criterion for quantitative characterization of the sulfur corrosion was proposed, considering polymerization of insulating paper, total sulfur concentration and oil weight. The results provide useful references for the reliable operation of power transformers.