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 proper ties change, the paper loses its strength and becomes brittle. A study of the accelerated ageing of cellulosic insulation paper in insulatio n oil has been performed in the temperature range 129-166 degrees C un der vacuum. The tensile strength of paper that has been subjected to a ccelerated ageing as well as of paper retrieved from a retired transfo rmer were measured in the cross machine direction (CMD), The results w ere found to be consistent with the observed changes in the molecular weight of the insulation paper. The relationship between tensile stren gth and molecular weight has been delineated and correlated with infor mation on the kinetics of degradation of the insulation paper.