The furfural content in oil may dispersedly change along with the operating time of transformer

which makes it difficult to evaluate the paper insulation aging status of oil-immersed transformers. To overcome this shortage

the methanol

ethanol and other low molecular alcohols are theoretically analyzed and experimentally verified as new characteristic products of paper insulation aging evaluation. The generation principles and ways of low molecular alcohols such as methanol and ethanol are theoretically explored by analyzing the aging mechanism of insulating paper and the order of chemical bond breaking. The content of furfural

methanol and ethanol in two groups of insulating oil samples obtained from two old transformers are measured by gas chromatography-mass spectrometry. The experimental results show that no furfural but a considerable amount of ethanol is detected in the two groups of samples. Moreover

the detecting results of the two transformers newly put into operation are compared

the results show that compared with furfural

ethanol can be used as a more effective characteristic product to present the aging of transformer insulation paper.