Review of chemical indicators of degradation of cellulosic electrical paper insulation in oil-filled transformers

Chemical and thermal degradation of electrical insulation in oil-filled transformers, mechanisms of failure and methods of condition monitoring and of life prediction are reviewed. An insulation life prediction model is developed and estimates of insulation life are presented under a variety of oil/paper conditions. Systematic measurements of the concentration of chemical indicators in transformer oil are used to demonstrate that furaldehyde and related products can be used to detect high rates of paper degradation. Similarly, phenol and related products indicate electrical degradation in phenol-formaldehyde resins.