A STUDY OF DEGRADATION OF CELLULOSIC INSULATION MATERIALS IN A POWER TRANSFORMER .2. TENSILE-STRENGTH OF CELLULOSE INSULATION PAPER

When cellulose insulation paper ages, its physical and chemical properties change, the paper loses its strength and becomes brittle. A study of the accelerated ageing of cellulosic insulation paper in insulation oil has been performed in the temperature range 129-166 degrees C under vacuum. The tensile strength of paper that has been subjected to accelerated ageing as well as of paper retrieved from a retired transformer were measured in the cross machine direction (CMD), The results were found to be consistent with the observed changes in the molecular weight of the insulation paper. The relationship between tensile strength and molecular weight has been delineated and correlated with information on the kinetics of degradation of the insulation paper.