Research On Surface Charge Distribution Of Polymers And Its Influence On DC Flashover Characteristics

Polymer dielectrics are widely used in high-voltage electrical equipment due to their excellent electrical and mechanical properties.In DC electric field,a large amount of electric charges are likely to accumulate on the polymer surface,which directly affect the surface insulating performance.However,the influence of surface charges on the surface flashover characteristics of polymers is not clear yet,which becomes a fatal risk that threatens the reliable operation of electrical equipment.Therefore,it is essential to conduct in-depth research on this kind of issue.This work intends to carry out research on surface charge distribution of polymers and its influence on DC flashover characteristics.Firstly,the experimental study of DC surface flashover on three typical polymers(silicone rubber,epoxy resin,and organic glass)will be carried out under rod-rod,pin-pin and rod-plate electrodes.Through the image processing technology and numerical calculation method,the optical and electrical properties of surface discharge will be analyzed.The optical characteristics of surface flashover is quantitatively characterized by gray values of discharge image,discharge channel uniformity and fractal dimension,and the insulation performance of the spacer is reflected by the flashover voltage and discharge energy.Furthermore,the correlation between the optical and electrical properties of surface flashover will be explored.And then,the positive and negative charges are imposed on the polymer surface by means of the needle-plate electrode corona discharge.The surface potential of the polymer is measured by an active capacitance probe combined with an electrostatic voltmeter,and then the influence of voltage amplitude and polarity on the surface charge accumulation and dissipation will be studied.Based on the experiment results,the ability of surface charge accumulation and dissipation of polymers will be obtained.In addition,the main path of surface charge dissipation will be explored by comparing surface charge distribution,volume resistivity and surface resistivity of the samples.The optical and electrical characteristics of DC flashover of polymers with surface charges of different amounts and polarities are studied under different electrodes,and the sensitivity of flashover characteristics of different polymers to surface charges will be obtained by analyzing test results.Then surface charges are applied at the middle region between the two electrodes or near the electrodes,and the influence of the position where surface charges accumulate on the flashover characteristic will be studied.Finally,based on the surface charge characteristics and its effect on flashover performances,the influence mechanism of surface charges on surface flashover will be explored from two aspects: the effect of surface charges on the electric field strength of the polymer surface and the contribution of surface charges to the process of surface flashover.This work can effectively promote the in-depth study of surface charge accumulation and surface discharge theory,and provide reasonable references for the solution of insulating problems and optimization design of insulation system of electrical equipment.