Study On The Dielectric Loss Characteristics Of Vegetable Oil Paper Insulation

As a new type of insulating oil for transformers,plant insulating oils and mineral insulating oils have different compositions and their physicochemical and electrical properties are not the same.This will inevitably affect the oil-paper insulation aging characteristics of the two.At present,the research on the plant insulating oil mainly focuses on the preparation technology and physical and electrical properties,and it lacks systematic research on the loss characteristics of the vegetable oil transformer oil-paper insulation.Through the test of the loss characteristics of the oil-paper insulation medium with different temperatures,micro-water,oxidation,and frequency,the characteristic parameters of the dielectric loss are obtained to reflect the oil-paper insulation state of the plant insulating oil transformer.In order to understand the dielectric loss characteristics,the second chapter introduces the types of dielectrics and the basic concept of dielectric polarization.Understanding the mechanism of dielectric loss based on the theory of dielectric polarization,a dielectric loss equivalent circuit model has been established and characterized by dielectric loss factor.Its loss characteristics summarize the factors that affect the liquid dielectric.Based on the above theories and models,an experimental method for the loss performance of plant insulating oils and insulating papers was given.The initial plant insulating oil,mineral insulating oil,plant insulating oil-impregnated paper board,and mineral insulating oil-impregnated paper board were subjected to dielectric loss test,and the results met the national standards.Claim.Based on the influence factors of the dielectric loss factor,the third chapter studies the effect of temperature,micro water content,oxidation and frequency on the dielectric loss properties of vegetable oil paper insulation from the experimental point of view.The results show that the vegetable oil and mineral oil have similar dielectric loss characteristics at low temperature.The dielectric loss temperature rise curve of vegetable oil from 32? to 141.4?rises significantly;the dielectric loss of plant insulating oil and mineral insulating oil varies greatly with the change of micro-water,and the loss factor of vegetable oil medium increases with the increase of micro-water,while the mineral oil is introduced.Loss increased slowly before slight water was 500mg/kg,and then increased rapidly.In accelerated heat aging experiments at 110?/3000h and 130?/1000h,the oil-paper insulation formed by vegetable insulating oil and mineral insulating oil respectively changed its oxidation parameters.Each is different;in the frequency domain dielectric response test,the transformers that inject plant insulating oil and mineral insulating oil respectively have different dielectric response curves,the frequency of the stage dielectric loss extremum is different,and the frequency of the maximum dielectric loss appears,the same.It can be seen that,under different influencing factors,the difference in the loss characteristics of oil-paper insulation composed of vegetable oil and mineral oil is significant.In order to reflect the insulation status of the oil-planted paper from the experimental data obtained,the correlation analysis of the vegetable oil-paper insulation aging parameters in the oxidation test at 110?/3000h was conducted in the fourth chapter,and it was found that the degree of polymerization between the insulating paper and the medium loss in the oil has Relevance.In order to verify the correctness of the correlation,correlation analysis was performed on aging parameters other than the degree of polymerization.It was found that the dielectric loss in oil was correlated with oil breakdown voltage,micro-water,volume resistivity,furfural,and acid value.Then directly use the correlation model between the degree of polymerization and other aging parameters to bring in the aging data at 130?.The predicted values of the last set of data are seriously inconsistent with the actual values.For this purpose,a semilogarithmic linear model is used to add oil medium.As a second variable,the loss was fitted to all 110? and 130? degrees of polymerization,furfural,and intermediate loss values.An improved semi-logarithmic linear model was obtained.The fitting accuracy was satisfactory.The loss of oil in oil can reflect the aging state of oil-paper insulation to a certain extent.