Study On The Space Charge Characteristics Of Nano Modified Insulating Pressboard

As an important part of UHVDC transmission system,the converter transformer is directly related to the safe and stable operation of the entire transmission system.Converter transformer in operation will withstand AC,DC and AC-DC superimposed voltage,and face the problem of the uneven distribution of internal electric field and other issues under the action of DC electric field.Therefore,in this paper,nano doping technology was used to make a kind of nano modified insulating pressboard to improve the problem of uneven electric field distribution and the interface space charge accumulation problem.The research work carried out include:The molecular structure of insulating pressboard is described in this paper.Drawing on the production process of insulating pressboard in industry,the preparation of modified pressboard sample is completed by nano SiC and nano Al₂O₃ in the laboratory.The samples were oiled impregnation according to the standard,then the microstructure of cellulose and nano particles in the modified pressboard was observed by scanning electron microscope,and the feasibility of nano modified insulating pressboard was verified.The dielectric properties and space charge distribution characteristics of the modified pressboard were tested.The study results on the dielectric properties of modified pressboard show that the conductivity of nano SiC modified pressboard increases with the increase of nano doping ratio,and the non-linearity increases with the increase of electric field under high electric field.The dielectric constant and dielectric loss increase with the decrease of nano doping ratio at first,and then increase with the increase of nano doping ratio;AC and DC breakdown field strength decrease with the increase of nano doping proportion.The conductivity of nano Al₂O₃ modified pressboard firstly decreases and then increases with the increase of nano doping ratio,and increases with the increase of temperature,and the nonlinearity is more obvious with the increase of temperature.The dielectric constant and dielectric loss increase at first with the increase of nano doping ratio,and then increased;AC and DC breakdown field strength increased with the increase of nano doping ratio increased at first,and then decreased.The study results on space charge characteristics of modified pressboard show that during the process of applying voltage,the electric charge quantity of nano SiC modified pressboard is more than that of ordinary insulation pressboard,while the electric charge quantity of nano Al₂O₃ modified pressboard is less than that of ordinary insulation pressboard;the maximum distortion rate of field strength of nano SiC modified pressboard is higher than ordinary insulation pressboard,and nano Al₂O₃ modified pressboard is lower than ordinary insulating paper;adding nano SiC promoted the pressboard space charge injection and accumulation,while the addition of nano Al₂O₃ inhibited pressboard space charge injection and accumulation.In the process of removing voltage,the higher the electric field strength and temperature are,the faster the dissipation rate of the space charge of the nano SiC modified pressboard is,which can promote the dissipation of space charges;the dissipation rate of the space charge of the nano Al₂O₃ modified pressboard is higher than ordinary insulation pressboard,which can inhibit the space charges.