Correlation Analysis and Regression Fitting of Multiple Sulfide Aging Characteristic Parameters

Abstract

The corrosion of transformers by multiple sulfides seriously affects the safe operation of transformers. However, there is a lack of quantitative characterization of the extent to which temperature and oxygen as well as changes in sulfide species affect the aging of oil–paper insulation. In this study, the aging characteristics of oil–paper insulation systems were analyzed in terms of the moisture in the oil, moisture in the paper, acid value, and furfural in the presence of multiple sulfides, where the temperature and the oxygen concentration are used as independent variables. A strong positive correlation between the acid value and the furfural obtained by means of Spearman’s correlation analysis. The acid value and furfural content in the oil were then analyzed and compared according to a nonparametric test, and it was found that both the oxygen changes and the temperature changes had a relatively obvious effect on the acid value in the oil. The effect of the temperature change on the furfural was greater than the effect of the oxygen change on the furfural. Finally, a multiple linear regression analysis was performed for the change in the acid value of the oil with the change in the oxygen content and temperature to obtain the linear fitting formulas for the effects of the time, temperature, oxygen content percentage, and sulfide groups on the acid value. This study can be used to quantify the magnitude of the influences of the oxygen, temperature sulfide groups, and other factors on the aging characteristic parameters of the oil–paper insulation system and to provide a certain reference for studying the quantitative characterization of the sulfur corrosion degree by using the change in the acid value in oil.