Deterioration Degree Assessment of Multiple Sulfides in Transformer Oil Based on the Entropy-weight Method

The corrosive sulfur phenomenon has decades of history and current research is mainly focused on DBDS. However, the transformer oil usually contains multiple sulfides. Up to now, there is still a lack of appropriate quantitative methods to characterize the degree of multiple sulfur corrosion. In this paper, accelerated thermal aging experiments on oilpaper insulation containing dibenzyl disulphide (DBDS), dibenzyl sulfide (DBS) and dodecyl mercaptan (DDM) with different concentrations at 140 °C are described. During the aging process, samples are regularly taken characteristic indexes, such as the color of copper sheet, the degree of polymerization of the insulating paper, the furfural in the oil, the moisture in the oil and paper, and the acid value in the oil are measured. Data are processed by the entropy-weight method and the contribution of each group of sulfides to the deterioration of the insulation system are comprehensively evaluated. Finally, a general formula for the relationship between the aging time and the deterioration degree under different sulfides is obtained, which can quantitatively predict the degree of sulfur corrosion. This study can provide some reference for monitoring the protection of oil-paper insulation and prevent the occurrence of sulfur corrosion failure.