| Epoxy resin insulator plays an important role in Gas Insulated Switchgear(GIS)and Gas Insulated Transmission Line(GIL).Under the action of long-term direct current(DC)high voltage,the electric field distortion caused by charges accumulated on its surface could lead to surface flashover.Besides,the distribution characteristic of surface charge is affected by the moving metal particle due to the vibration during the operation of GIS/GIL.It is of great significance to figure out the influence of vibration on the dynamic behavior of metal particle and surface charge accumulation.In this paper,the vibration system for a 126 k V disc insulator was designed,based on which the effect of vibration on the surface charge accumulation and the changes in charge distribution characteristics induced by linear metal particle with vibration were investigated,so as to provide reference for further revealing the surface charge accumulation mechanism of disc insulator.The main work of this paper is as follows,1.The periodic vibration schemes of high amplitude/low frequency and low amplitude/high frequency was designed to apply on the insulator.The corresponding vibration systems were built on the basis of pull/push solenoid and vibration motor respectively and the vibration could be controlled during the charging process.The vibration acceleration and velocity curves of insulator under two vibration modes were obtained by piezoelectric acceleration sensor.The results indicate that the maximum vibration acceleration can reach 338.9 m/s~2 and 4.6 m/s~2,and the vibration frequency are 1.1 Hz and 107.5 Hz,respectively.2.The effect of vibration mode on the surface charge accumulation characteristic of disc insulator was studied under±30 k V DC voltage.The results showed that the vibration led to the decrease of the amount of homo-charge on the surface,especially on the nonplanar region.When a discharge source was set on the electrode,the changes of homo-charge amount and its distribution area were more significant than that without discharge source.In addition,the change of homo-charge amount was greater than that of hetero-charge with the same area.The decline in homo-charge amount under+30 k V was more obvious when compared to that under-30 k V with the same vibration mode.Under the same voltage polarity,the percentage of homo-charge decrease caused by high amplitude/low frequency vibration mode was higher than that caused by the other mode.The main reasons for the change of charge accumulation characteristic are that the detrapped homo-charge resulted from vibration dissipates into the gas along the normal electric field,and recombines with hetero-charge through the tangential electric field.3.The motion of metal particle at different initial positions was observed under high amplitude/low frequency vibration condition.The effects of length,lifting pattern,motion path and final static position of the particle on the surface charge accumulation characteristic at-30 k V were studied.It was found that when the metal particle finally rested at the junction of insulator or the planar region near the edge of grounded electrode,a large number of positive charges were significantly accumulated near the particle.When the particle left the electrode through the way of rolling first and then lifting,even if the metal particle only collided rather than rested at the junction,the charges were easy to accumulate on the insulator.The amplitude of the surface charge density increased with the length of the metal particle.The positive and negative charges were distributed zonally along the rolling path of the longest particle.The electric field was simulated by COMSOL Multiphysics software.It is indicated that local electric field distortion caused by the charge quantity and the position of particle would affect the surface charge accumulation characteristic. |
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