A STUDY OF THE DEGRADATION OF CELLULOSIC INSULATION MATERIALS IN A POWER TRANSFORMER .3. DEGRADATION PRODUCTS OF CELLULOSE INSULATION PAPER

The cellulosic insulation materials in operational transformers underg o a slow thermal degradation during the life-time of the transformer t o form furans which dissolve in the insulation oil of the transformer. There are six furans formed in significant quantity in an operational transformer. They are 2-furfuraldehyde, 5-hydroxymethyl-2-furfuraldeh yde, 2-methyl-furfuraldehyde, 2-acetyl furan, 2-furoic acid and furfur yl alcohol. The concentrations of these furans can be measured by HPLC analysis of the oil. In this paper the furan products formed by accel erated ageing of cellulose insulation paper in Shell Diala B transform er insulation oil over the temperature range 130-170 degrees C are inv estigated, and the results have been correlated with those observed fo r the changes in the molecular weight and tensile strength of the insu lation paper.