A Novel Methanol-detection-method for the Aging Prediction of Paper Insulation in Power Transformer

Paper insulation in transformers plays an important role in the operation of the power grid. At present, the aging evaluation and fault detection of transformers are mainly conducted by means of polymerization degree, CO/CO2, furfural. However, they have no sensitive response in the early aging of paper insulation. In this paper, methanol was chosen as an indicator to evaluate the aging of transformers. An evaluation method based on the measurement of methanol concentration was proposed. After the extraction from transformer oils, methanol was oxidized by potassium permanganate acid solution. Chromotropic acid solution was then chosen to react with the oxidation products (formaldehyde) to form a purple compound, after which methanol content was measured by the absorbance method. The mathematical correlation of methanol content and degree of polymerization (DP) was then established, and it could be used to predict the aging of paper insulation and the remaining life of the transformers.