Distribution Of Micro-water In Oil-paper Insulation And Its Influence On Dielectric Spectra In Frequency Domain

Oil-paper insulation system composed of ordinary insulating oil and cellulose insulation paper is the main insulation method of power transformer at present.The moisture content of oil-paper insulation has an important effect on the electrical performance,aging rate and service life of the insulation system.At present,the nondestructive testing method of the micro-water content in the oil-paper insulation of the transformer is mainly the dielectric response method,among which the frequency-domain dielectric spectroscopy has attracted the attention of many researchers with its unique advantages.Therefore,it has great significance to explore the effect of oil-paper insulation on micro-water distribution in the frequency domain.In this paper,a set of test platform for dielectric measurement is set up in the laboratory.The source of the interference is analyzed and the corresponding anti-jamming method is adopted to quantitatively analyze the errors of the test results.The error of system measurement under this experimental condition is calculated and corrected to meet the precision requirement of this experiment.The actual distribution of the transformer temperature distribution is uneven and the insulation is a multi-layer structure,and oil paper moisture distribution and temperature-related,so the actual winding insulation is the uneven moisture distribution of multi-layer oil-paper insulation structure.In this paper,oil paper insulation samples with different initial moisture contents were prepared.The experiment was carried out to verify the law of water transfer in oil paper at different temperatures.The influence of multi-layer structure and moisture distribution on the dielectric curve was also studied.The simulation results show that the dielectric properties of the transformer winding insulation under different water in homogeneities are simulated by the simulation model of oil immersed insulation paper.The main research results in this paper are as follows:(1)Experiments were carried out to verify the transfer rule of micro-water in oil-paper insulation at different temperatures: As the temperature increased,the moisture in the oil-paper insulation test sample was transferred from the insulating paper to the insulating oil,the temperature was higher,The moisture content in insulation paper is lower.The higher the initial moisture content is,the higher the moisture transfer rate is.However,when the moisture content is low,the change of temperature has little effect on water transfer.(2)Dielectric test of oil-paper insulation of multi-layer structure: Compared with single-layer paperboard,multi-layer paperboard produced interface polarization at the interface of two layers of insulation paper,resulting in a large amount of charge accumulated here,polarization degree The tanδ characterization of the dielectric loss will increase;the dielectric response curves between the different layers of the multilayer insulating paperboard are different from those of the monolayer,due to the existence of the polarization effect between the multilayer insulation paperboard and the energy consumption polarization.There was no significant difference.(3)By comparing the experimental data of monolayer and multilayer structure with different temperature and different micro water content,it was found that the increase of dielectric loss caused by multi-layer structure compared with single layer structure,Rise and increase in moisture content.(4)The finite element simulation model is established to simulate the actual model.The results show that the dielectric loss of the model increases with the increase of water content in different combinations.Measured oil-impregnated cardboard into the phase coincide.