Aging Assessment Model of Transformer Insulation Based on Furfural Indicator under Different Oil/Pressboard Ratios and Oil Change

Oil change, as an effective method, could improve the performance of liquid insulation. However, due to the furfural loss in oil after the oil change, the aging assessment results of cellulose insulation based on the traditional furfural-degree of polymerization (DP) model is not accurate. Besides, the different oil/pressboard mass ratio of the transformer also has a significant impact on the aging assessment results. Current research only focuses on the aging assessment based on furfural analysis under the single oil/paper mass ratio and oil change conditions. In view of this, the aging assessment model for transformer insulation based on furfural indicator under different oil/pressboard ratios and oil change conditions was studied. First, oil/pressboard insulation systems with different oil/pressboard mass ratios were performed for total oil changes. Then, the initial furfural-DP equation and the furfural corrected equation were obtained. Finally, the modified furfural-DP model extended to different oil/pressboard mass ratios under oil change was established. The proposed model is expected to promote the accuracy of the aging assessment of transformer cellulose insulation under different oil/pressboard mass ratios and oil change conditions.