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.

I. Introduction

The power transformer plays a significant role in the electric power system and the life of the insulating paper mainly determines that of transformers [1]. The insulating paper in the transformer degrades due to the effect of thermal, electrical, mechanical and chemical stress. Among those forms of aging, thermal aging is the primary and most commonly found aging form [1], [2]. Therefore, monitoring the insulating paper degradation is important to the safe operation of transformers.