A novel aging indicator of transformer paper insulation based on dispersion staining colors of cellulose fibers in oil

Diagnosis of aging of the paper insulation in transformers has long been of interest to transformer manufacturers and utilities [1]-[3]. Such insulation is irreversibly aged during long-term operation, losing its mechanical strength and becoming brittle. The loss of mechanical strength is an important factor limiting the life expectancy of the transformer [4], [5]. Consequently diagnosis of aging and evaluation of residual life of paper insulation is important for the safe operation, condition-based maintenance, and replacement of power transformers [6]-[9].