Correlation analysis between crystalline behavior and aging degradation of insulating paper

The insulating paper in the transformer undergoes degradation during operation. Condition monitoring and assessment for insulating paper is of great significance as the life of insulating paper mainly determines that of transformers. Accelerated thermal aging experiments were performed for insulating papers at 120°C and 130°C, respectively. The crystallinity index of insulating paper was calculated with the X-ray diffraction pattern and the refractive index of insulating paper was measured. The results showed that the crystallinity index and refractive index of the insulating paper increase with the decrease of degree of the polymerization in general. The above work is a fundamental attempt in investigating the correlation between paper degradation and its crystalline behavior, which indicates that the crystallinity index and refractive index of the cellulose fibers in insulating oil may be a feasible index to diagnose the paper degradation.