Infrared detection of transformer insulation degradation due to accelerated thermal aging

Regular monitoring of the paper insulation of electrical windings is necessary to ensure safe and reliable operation of oil-paper insulated electrical transformers. The degradation of the paper insulation due to thermal aging yields furanic derivatives which are specific to the paper and cannot be produced by general oxidation of the oil. The concentration of such furan compounds in the oil gives an accurate indication of the condition of the paper insulation. Normally, off-line methods such as HPLC (high performance liquid chromatography) are applied to periodically assess the furan concentration within oil samples which have been extracted from the transformer. We report experimental findings on the production of the furan compound FFA (furfuraldehyde) in an oil-paper system subject to accelerated thermal aging. Our approach is based on IR spectroscopy. This technique could lay the basis for the construction of direct online monitoring equipment suitable for monitoring of transformer winding insulation.