The Research On Assessment Method Of Oil Paper Insulation Aging Based On Methanol Content In Oil

In oil-paper insulation system,the mechanical strength of insulation paper depends on the average length of cellulose chain,which makes degree of polymerization the index of measuring average length of cellulose chain become the most direct measured parameters of evaluating the aging condition of insulation paper.However,In the actual operation of the transformer,the degree of polymerization is not available to direct measurement.Normally,it is required to study insulation paper's aging and degradation,and products dissolved in insulating oil to indirectly reflect the aging state of insulation in transformer.because traditional assessment method of the state of insulation based on oil gas and furfural content in the oil more or less has some defects,and with the progress and matureness of detection technology and equipment,searching for more effective and precise aging products as evaluation index of oil-paper insulation state has a more practical significance.In order to study the relationship between methanol,the product of oil-paper insulation aging,and the cellulose pyrolysis of insulating paper,aging test under different tempatures and initial water content were designed in the Article,the advanced GC-MS with headspace sampling in chemical analysis was used to measure methanol content in aging oil.An aging dynamic model taking degree of polymerization of insulating paper as parameter was established,after introducing Mark-Houwink equation,cellulose pyrolysis rate under different aging conditions were determined,extracting the characteristic parameter of cellulose pyrolysis and methanol separately,which will be analyzed by using the fitting analysis for Arrhenius.The results showed that the rising of aging temparature could promote the rate of methanol generation and the pyrolysis rate of cellulose chain,without any obvious influencing rule on catalysis of methanol generated by aging.The presence of water and oxygen catalyzed the transformation of cellulose pyrolysis products to methanol.The intermediate product of cellulose hydrolysis was less likely to produce methanol.Methanol mainly came from the intermediate product of oxygen cellulose solution and its intermediate product need synergy of water to get further reaction of methanol.On this basis,the design of the intermediate aging experiment provides the certain proof for the conclusion.On the basis of research about characteristics of methanol in cellulose pyrolysis,by establishing the relationship model between methanol and the degree of polymerization,the paper predicts the life of oil paper insulation system under laboratory conditions.The results show that the life of cellulose insulation reduces by half when moisture content in insulation paper increases by 0.5%;the life of insulation paper reduces by half when the temperature rise 8-10C,which is consistent with many studies.The steady state equilibrium distribution of methanol in oil paper system was studied experimentally.The results show that a large portion of methanol produced by cellulose cracking exists in insulating paper at normal aging temperature.It provides a reference for the establishment of transformer condition evaluation system based on methanol content in oil.