Correlation analysis of dispersion staining color of cellulose fibers in insulating oil and paper degradation

Abstract

Paper insulation in transformers degrades due to the effect of thermal, electrical, mechanical and chemical stress and monitoring of the insulating paper aging thus becomes important to the safe operation of transformers. In this paper accelerated thermal aging experiments were conducted at 130 centigrade degrees for insulation paper with insulating oil. The cellulose fibers in insulating oil of each aging state were filtered through a membrane and then obtained. The dispersion staining color of cellulose fibers was observed using a polarized light microscope with a central stop dispersion staining objective. The intensity ratio of three primary colors (r, g and b) of the dispersion staining images were calculated and (r, b) points were plotted. With the increase of aging degree, r increases while b decreases. The dispersion staining color of cellulose fibers in insulating oil shows a potential to be a marker for paper aging.