Research On Influence Factors Of Accumulation And Decay Characteristics Of Surface Charge On Insulator Under DC Voltage

Gas insulated transmission line has the advantages of large transmission capacity,small loss,safe and reliable and environmental friendliness,and it is widely used in the field of high voltage transmission.Under the dc voltage,the charge will accumulate on the surface of the insulator,which will reduce the flashover voltage of the insulation structure and hinder the extension and application of the gas insulated transmission line to the dc field.It is of great significance to study the accumulation influence factors and decay characteristics of surface charge on insulator in dc voltage.The author designed the electrostatic probe with the principle of capacitive divider which can meet the needs of research.Cooperated with the flat electrodes and the model of cylindrical PTFE insulators and the stepper motors with matched control device which drive the insulator and probe in order to make the probe measure the whole surface of insulator,the author built the surface charge experiment system.In this paper,the influence of local factors such as metal particle attachment,electrode contact and surface scratch on the surface charge accumulation of insulator is studied with the surface charge experiment system.It has been found that the surface charge accumulation near the particle is obvious when the insulator is attached to the metal particles,and the charge polarity is consistent with that of the nearby metal particles.Gas conduction and surface conduction decide the charge distribution together.When the electrode contact is bad,a large amount of heteropolar charge is accumulated near the contact negative electrode,and the normal electric field is dominant to the distribution of positive and negative charge on the surface of insulator.When the surface is scratched,there is a large number of different charge on both sides of the scratch under lower voltage,and there is no obvious distribution characteristic at higher voltage level.At the same time,this paper studies the decay process of positive charge on the surface of the insulator under different external voltage.The results show that when the external voltage is 0,the charge mainly decays by neutralization with the ions in gas.When the external voltage is +20kV,the positive charge is hard to decay and increases lightly.Applied voltage of-20 kV,additive positive charge near the high voltage electrode decays quickly,and which is near the grounding electrode with shielding electrode changes extremely slowly with time when decays to a certain degree.The applied voltage mainly influences the conduction of charge along the surface,which influences the decay characteristics of charge.