| As an important factor that determines the life of a transformer,insulating paper is constantly aging during operation of the transformer.Aging not only leads to power outages,but may also cause explosions and the leakage of transformer oil.The thermal aging process of insulating paper in the laboratory was simulated,the generation rules of typical characteristic decomposition products were analyzed,and the insulating paper aging prediction model was established.The main research content and conclusions include:(1)A thermal aging simulation device for insulating paper was designed,the change process of the cellulose surface micro-morphology during the thermal aging process of the insulating paper and the type of functional group of the aging products were studied.During the aging process of cellulose,the surface of cellulose changed from dense and smooth to rough and twisted,and obvious pores were gradually formed,fine fibers were continuously detached.In addition,a large number of polar functional groups were produced.(2)The concentration of methanol,total sugar and 5-hydroxymethyl furfural were proposed as the new method for judging the aging degree of insulating paper,and the detection technologies of these characteristic products were studied.·The HPLC method for the detection of furfural and 5-hydroxymethyl furfural was explored;·Using acetonitrile as the extractant and GC-MS to detect methanol in the oil-paper insulation system was proposed,and the minimum detection concentration was 10?g/L;·The full spectrum detection technology combined with partial least squares(PLS)was used to optimize the traditional spectrophotometric method,a new technique for detection of total sugar by spectroscopy was proposed,and the goodness of fit was 0.99;In addition,according to the demand for on-site detection of furfural and methanol,the rapid detection technologies of furfural and methanol were studied.·Using the aniline color method combined with the spectrophotometric method to detect furfural,the new method directly detected furfural in transformer oil,the complicated steps and experimental errors of the national standard was avoided.·A new technology for the detection of methanol by spectroscopy was studied.In addition,a new technology using solid phase extraction-headspace method to detect methanol in transformer oil was studied.Through heating to desorb the methanol,the interference caused by the eluent to the experiment was avoided.(3)Through the laboratory simulation of the thermal aging process of insulating paper,the change of the degree of polymerization of insulating paper with aging time at different temperatures was studied,and the second-order kinetic model of thermal aging of insulating paper was established.In addition,the breaking rate of?-1-4glycosidic bonds was studied.The breaking rate decreased exponentially with aging time.(4)The generation rules of aging characteristic products were studied.As the aging time increased,the degree of polymerization decreased,and the concentration of degradation production was increased;the higher the temperature,the faster these degradation production producted.There was a linear relationship between methanol concentration and the degree of polymerization,a piecewise linear relationship between the 5-hydroxymethylfurfural concentration and the degree of polymerization,and a logarithmic relationship between furfural and total sugars concentration and the degree of polymerization.(5)A prediction model for the aging degree of insulating paper based on the aging characteristic product was established,and the applicability,advantages and disadvantages were analyzed.In addition,a prediction model for the degree of polymerization was established,and the apparent activation energy of insulating paper degradation was calculated,E_a=73.6 k J/mol.The combination of prediction models can better judge the aging degree of insulating paper,can avoid pollution such as power outages and the leakage of transformer oil,and reduce the waste of resources,which is the research trend of aging diagnosis in the future. |
PDF Full Text Request