Chemical degradation of cellulosic insulation paper for power transformers

In this paper some results of a study of the physical and chemical properties of new Kraft insulation paper and paper retrieved from a retired transformer are presented. These results have been compared with those found for a series of experiments in which new insulation paper was artificially aged at elevated temperatures. Molecular weight studies on the cellulosic components of the paper following artificial ageing have allowed the rate constant for chain scission to be calculated for a range of degradation temperatures. An Arrhenius analysis of these rate parameters yielded an activation energy for chain scission of 79.5 kJ mol^-1. These data have been used to prepare lifetime prediction curves for transformer insulation at the typical operational temperatures of power transformers