Study On The Surface Charge Accumulation Characteristics Of Polypropylene Under The Control Of Shape And Surface Morphology Parameters

With the development of the national economy,China’s energy distribution is uneven.The emergence of high-voltage direct current(HVDC)transmission and flexible grids is an effective means to address the imbalance of energy distribution.Dielectric materials serve as core components in electrical equipment,playing a key role in electrical insulation,mechanical support,and physical protection.During long-term operation,surface charges accumulate on the surface of dielectric materials.The accumulated surface charge induces electric field distortion on the surface of the dielectric materials and provides seed charges for the development of surface discharge,which reduces the flashover voltage of the dielectric material and accelerates the formation of the flashover process.In order to improve the flashover voltage of dielectric materials,the accumulation characteristics of surface charge can be improved by altering different factors,such as shape,surface morphology,temperature,surface fluorination,etc.However,the influence of shape and surface morphology on surface charge accumulation has not been comprehensively evaluated by the process of charge injection and discharge simulation under gas-solid interface interaction.Therefore,this article researches the charge transfer paths under different shapes,electric field distortions and trap distributions under different morphologies,and charge accumulation simulation at gas-solid interfaces.This helps to deeply understand the mechanism of charge transport and accumulation,provides an important theoretical basis for the development and application of dielectric materials.A high-voltage discharge platform and a surface potential measurement platform are developed.Polypropylenes with different shapes(square,circular)and different surface morphologies are prepared.The surface potential distributions of the samples are obtained through surface potential measurement platform.The results show that the amplitude of surface potential gradually decreases from the center to the edge of the square and circular sample.The surface potential distribution of square samples gradually dissipates from bell-shaped to onesided collapse,which is mainly cause by the inconsistent path of the escape of surface charge.The surface potential distribution of circular samples dissipates slowly from the bell shape to the crater-like shape,which is mainly cause by the neutralization of air ions and the changes in the surface conductivity of the sample.With the increase of surface roughness of the polypropylene,the accumulation and dissipation of surface charges are inhibited.The main reason is that the increase of the roughness of the samples can lead to the distortion of electric field on the surface of the samples,which hinders charge accumulation.Meanwhile,the density of trap level decreases with the increase of roughness,which reduces charge carrier mobility and suppresses charge dissipation.A two-dimensional axisymmetric model is constructed by the COMSOL finite element simulation software.Based on the principles of fluid dynamics,a theoretical equation for the corona discharge process in ambient air is established from the perspectives of microscale ion reactions and macroscale charge ion transport.The initial surface potential distributions of square and circular samples are simulated,and the curves of the initial surface potential are plotted.The results show that the simulation results are consistent with the measurement results.Then,the influence of roughness on the electric field is simulated.The results show that increasing roughness cause the distortion of electric field on the surface of the samples,and the surface electric field intensity can reach 7×105 V/m,which hinders charge migration to the surface of the samples.Finally,the curve of trap level distribution is plotted based on the theory of isothermal potential decay.The results show that the increase of roughness lead to the increase of the trap density,which suppresses charge dissipation.The influence of shape and surface topography on the charge accumulation characteristics of polypropylene is investigated by combining theoretical analysis,experiments,and simulations.It helps to further study the mechanism of charge migration and accumulation,which provides important data support for analyzing the insulation performance of dielectric materials and improving the reliability and safety of electrical equipment.