A STUDY OF DEGRADATION OF CELLULOSIC INSULATION MATERIALS IN A POWER TRANSFORMER .1. MOLECULAR-WEIGHT STUDY OF CELLULOSE INSULATION PAPER

As a transformer ages, the chemical and physical properties of the cel lulose insulation paper will change. For example, the average molecula r weight of the cellulose chains decreases with age, as does the stren gth of the insulation paper. The molecular weight changes can be studi ed by several methods. However, the GPC method reported in this paper has an advantage over the other methods because it yields the total mo lecular weight distribution. In order to understand the mechanism of t he degradation of the cellulosic insulation materials in a power trans former, a study of the accelerated ageing of cellulosic insulation pap er in insulation oil has been performed in the temperature range 129-1 66 degrees C, under vacuum. The molecular weight and molecular weight distribution of the cellulose chains present in the insulation paper w ere measured by GPC techniques. The results provide information on the kinetics of degradation of the insulation paper. The results of the m olecular weight study in the accelerated ageing experiments were found to be most useful for monitoring the condition of the insulation pape r in an operational transformer.