A study of degradation of cellulosic insulation materials in a power transformer, part 1. Molecular weight study of cellulose insulation paper

Abstract

As a transformer ages, the chemical and physical properties of the cellulose insulation paper will change. For example, the average molecular weight of the cellulose chains decreases with age, as does the strength of the insulation paper. The molecular weight changes can be studied by several methods. However, the GPC method reported in this paper has an advantage over the other methods because it yields the total molecular weight distribution. In order to understand the mechanism of the degradation of the cellulosic insulation materials in a power transformer, a study of the accelerated ageing of cellulosic insulation paper in insulation oil has been performed in the temperature range 129–166 °C, under vacuum. The molecular weight and molecular weight distribution of the cellulose chains present in the insulation paper were measured by GPC techniques. The results provide information on the kinetics of degradation of the insulation paper. The results of the molecular weight study in the accelerated ageing experiments were found to be most useful for monitoring the condition of the insulation paper in an operational transformer.