Effect of Electric Field on Methanol Generation in Transformer

Abstract

Chemical indicators were widely used in condition assessment of transformers. Methanol is considered as a better method than furfural to assess the condition of transformer with higher detection rate and thermal stability. However, the effect of electric field on the generation of methanol still needs further investigation. In this report, insulation oil and 5mm-thick cellulose paper were put into aging cell with a weight ratio of 10:1 after degased and dehydration. Aging experiments were carried out at 120°C with and without an electric field of 2kV/mm, respectively. Degree of polymerization, concentration of methanol, furfural and ethanol dissolved in oil were measured after accelerated experiments. The concentration of methanol in oil was much higher than that of furfural at early aging while it increased with aging time. Samples aged under electric field had higher methanol concentration, and the amount of methanol was proportional to the number of scissions of cellulose chain. It was indicated that the electric field accelerated the generation of methanol by aggravating the scission of cellulose chain.