Study On Aging Evaluation Of Transformer Insulation Paper Based On Methanol In Oil

With the rapid development of China's power grid,the operation of ultra-high voltage and ultra-high voltage substations has become more and more demanding for the safety and reliability of oil-immersed transformers.Accurate transformer assessment is particularly important.At present,the analysis of transformer oil is a common means of quickly reacting the operating state of the transformer.The commonly used analytical parameters mainly include the analysis of dissolved gas components in the oil and the analysis of furfural content.The former detection principle leads to low accuracy,while the latter The oxidative property of furfural lead to unsatisfactory results in field applications.A good correlation between the content of methanol in the oil and the degree of polymerization has been shown by current studies..Andthe degree of polymerization is the most accurate parameter for the reaction state of the oil-paper,while methanol has relative to other marker products.The stability and the high production capacity,the measurement and analysis of the methanol content in the oil can theoretically reflect the insulation aging state of the transformer oil paper more accurately.In this paper,the method of headspace injection-gas chromatography-mass spectrometry(HS-GC-MS)for the determination of methanol in oil was summarized and summarized.The optimum conditions were explored and optimized to determine the heating temperature of the headspace sampler at 120 °C.For 20 min,the measurement accuracy is 27 ppb and the standard curve is y=431.71*x+3.06.Based on molecular simulation technology,this paper analyzes the mechanism of cellulose breakage and the formation of furfural and methanol in the aging process of insulating paper,and conducts heat aging experiment using #25 insulating oil and cellulose insulating paper,which is obtained at 110,130,150 °C.The relationship between the methanol content in the oil and the furfural content in the oil was compared with the molecular simulation results.The results show that in the process of cellulose chain scission,the formation path of methanol is more diverse than that of furfural.The absolute content of methanol in oil is greater than that of furfural in the early stage of aging,and the degree of aging changes.The main reason for reflecting sensitivity.The experimental results show that the methanol content in oil and the degree of polymerization of insulating paper are linearly correlated in the early stage of aging(DP>400).There is no correlation in the late aging period.This characteristic of methanol can make up for the characteristic quantity of furfural and reflect the pre-aging of oil-paper insulation.Not obvious disadvantages.At the same time,different aging temperature,moisture content and insulating oil type will affect the methanol content in the insulating oil.The experimental results show that the higher the aging temperature,the higher the moisture content,the higher the methanol content in the aging result,the natural ester.The oil-paper insulation system cannot be evaluated for aging using the methanol content of the oil.