Abstract
Oxidation ageing experiments on paper and transformer oil insulation has been performed using two different techniques. First, we used oxygen pressurized bottles with oil-paper isolation where oil and paper are sampled at certain intervals during 8 months and degree of polymerization is measured. Second, a microcalorimeter measuring continuously the heat flow from the paper-oil sample was used. We find that the degradation reaction rate is not linear with oxygen concentration and that the activation energy of oxidation is different from what has earlier been found for hydrolysis. The microcalorimeter seems to mimic ageing characteristics for oxidation and can potentially be a useful tool for quick ageing investigations.