Research On Detection Technologies And Characteristics Of Transformer Insulation Paper Aging Products

Transformer is one of key equipments of power system,once fails,it will cause great loss.As the main structure used in oil-immersed transformer,oil-paper suffers from thermal aging stress in the long-term running,deteriorating the insulating performance which accounts for a fairly large proportion of transformer fault.Therefore,it is of great significance to make insulation diagnosis and life estimation of transformer insulating paper.This paper mainly includes the following three points:(1)Spectroscopy combined with aniline acetate is used to detect furfural produced by aging insulating paper.Aniline as chromogenic agent reacts with furfural in transformer oil,then reaction conditions are optimized by orthogonal experimental design.The linear relationship is built between absorbance at characteristic wavelength and concentration of furfural.(2)Ultraviolet spectroscopy combined with partial least squares method are used to develop a partial least square regression model between total sugar content and ultraviolet spectral of its hydrolyzed solution.Variable-controlling approach is used to explore the best sugar acid dehydration reaction conditions,and the prediction accuracy and stability of models are compared with the partial wavebands(270~360 nm)regression model and the full wavelength(205~360 nm)one,then smoothing and derivative are used to get a optimization model.(3)Heating aging experiment at three groups of different temperature,namely 90?,100?and 110?,are designed,then total sugar content under different aging temperature and time are determined to study its connection between aging characteristic parameters.The results are as follows:(1)Furfural becomes a pink compound which exhibited a characteristic absorption peak at 514 nm when blended with aniline acetate,avoiding interference from transformer oil at 275 nm.An optimized process is obtained as follows: 1.5:1 volume ratio of chromogenic reagent to oil sample,and the reaction time 5 minutes.Characteristicabsorbance shows a favorable linear relationship with the concentrations of furfural in the range of 0.116 ~5.800 mg/L,with good reproducibility.(2)The optimum reaction condition of dehydration of saccharide is determined by 3m L 98% concentrated sulfuric acid added to 1 m L sugar solution.The prediction and stability of the model are significantly improved compared with the original spectrum after37 points smoothing.The model with full wavelength has better forecasting precision and fitness and the first and second derivatives do not optimize the model.(3)Sugars appears earlier than furfural and total sugar content is always much higher than that of furfural in the aging period.The higher aging temperature,the higher total sugar content.Total sugar content increases linearly with increasing of aging time,moreover at90?,100? and 110?,the correlation coefficient are 0.886,0.885 and 0.935,respectively.The regression equations of polymerization degree and logarithmic of total sugar content are built,with the goodness of fit 0.930,0.956 and 0.955 respectively,indicating that the linearity of polymerization degree and logarithmic of total sugar is well.Spectroscopy could be used as a fast detection method for furfural and total sugar and there is a certain relationship between the total sugar content and the aging degree of the insulation paper.This paper provides a new method for detection of products by aged insulation paper and a new idea for evaluating the aging state of insulation paper.