New diagnosis method of aging degradation for insulating paper in power transformers by measuring the refractive index of cellulose fibers

This paper proposes a new diagnosis method for aging degradation of insulating paper in power transformers. We took notice of cellulose fibers that suspended in insulating oil in transformers as useful samples for estimating degradation of insulating paper in transformers. The Mahalanobis-Taguchi System was applied for investigating the relationship between degradation and refractive indices of cellulose fibers measured. It was found that aging degradation of cellulose fibers on insulating paper accompanies a change of dispersion color. This result shows that it is capable to estimate degradation of the paper in oil-immersed power transformers by measuring dispersion color of fibers suspended in insulating oil.