Production Pattern of Furfural in Esters-Immersed Paper and Aging Evaluation Methods

With the increasing requirements of environment protection and fire prevention, esters insulation oils including natural esters and synthetic esters have been widely used in transformers. Studies have shown that esters can retard the aging rate of insulation paper. However, whether the aging-delaying phenomenon affects the production pattern of furfural and aging assessment models is not yet known. To address this issue, accelerated thermal aging experiments with different oil-paper systems were carried out and discussed. The results indicate that ester insulation oils can delay the aging rate of insulation paper while also reducing the furfural production amount. Upon degree of polymerization (DP) values of insulation paper decreasing to 550, the total furfural amount produced in the synthetic ester, soybean oil, and linseed oil-paper systems is 0.8, 0.59, and 0.54 times that in the mineral oil-paper system, respectively. This discrepancy is attributed to significant differences in moisture solubility and oxidative stability among different insulation oils, which decreases the moisture content in esters immersed in insulation paper and the oxidative degradation process, thereby decreasing the total furfural amount. In order to eliminate the impact of various insulation oils on the furfural assessment model, the relationship between furfural contents and DP values in different esters should be reestablished.