DEPOLYMERIZATION PROCESSES IN THE THERMAL-DEGRADATION OF CELLULOSIC PAPER INSULATION IN ELECTRICAL TRANSFORMERS

A dynamic heating experiment was used to examine the influence of temp erature on the degradation of the Kraft insulating paper in transforme r oil. The degradation was monitored by measuring a number of key indi cators on selected samples as a function of progressive ageing. These indicators included the degree of polymerization (DP), level of furani c compounds and level of gases such as carbon oxides and oxygen. The r esults show that the formation of furanic compounds and of gases begin s significantly after a large reduction in DP, indicating a two-stage process: firstly scission leading to a sharp drop in DP and secondly f ormation of low molecular weight degradation products. (C) 1998 Elsevi er Science Limited. All rights reserved.