| Gas insulated metal enclosed system(GIS)which use SF6 as insulating medium have the advantage of stable performance,high reliability,large transmission capacity,low loss,environmentally friendly and other advantages,and have a wide application prospect in UHV transmission and offshore large-scale wind power transmission and other fields.In the process of production,transportation and operation and so on in GIS,the uncontrollable factors such as vibration,friction and desorption of the equipment will inevitably lead to the production of metallic partical,which seriously damage the insulation performance of GIS.Sepecific performances are as follows:1)In the electric field,the metal particles on the surface of outer apertures will distort the surface electric field distribution,and cause internal partial discharge;2)Occur directional movement by electric field force in the chamber of GIS,thus leading to reduce the gap,and cause breakdown;3)Move directionally and attach to the surface of post insulator,distorting the surface electric field distribution of insulating parts,reducing the surface flashover voltage and leading surface flashover.Related research shows,the existence of metal particles in GIS can lead to a decrease of 90% of the internal insulation strength,seriously affect the stability and reliability of GIS operation.The surface coating of the external cavity is an important measure to re strain the movement of metal particles and improve the problem of metal particles pollution.After coating,the colliding performance between the particles and electrodes,the amount of charge,and the lifting voltage can change.According to the principle of kinematics,the coefficient of restitution measurement platform was built,and the coefficient of restitution between the particles and the electrode was studied.The effect of particle size,colliding velocity,coating materials and coating thickness on the coefficient of restitution were obtained,and the regression analysis was carried out.Experimental results show that the silicone rubber which has small hardness and good elasticity can reach the purpose of controling the height of particle bounce after the colliding with the electrodes.Based on the Faraday cage,an experimental platform was built to measure the amount of charging particles in the air under DC voltage,and gained the law.This paper measured the charging amount of different dielect ric films(such as PET film,silicon rubber and so on),from the experiment we find eventually the amount of charge won't be affected by coating,and the effect of coating just prolong the charging time of particles.According to the conduction mechanism be tween the particles and the dielectric film,the above results were explained.In this paper,the lifting experiment platform of metal particles was established,and the lifting voltage of metal particles in the air under DC voltage was obtained.The experimental results show that the film has a remarkable electrostatic adsorption effect on the particles,which makes the lifting voltage significantly improved.The effects of the film material and thickness on the lifting voltage were studied.The experimental results show that particle lifting voltage of silicone rubber coated electrode is larger than that of PET film,with the increasing of the thickness of film,the lifting voltage has an increasing trend,but the effect is not obvious.The experimental results show that the movement of the particles after coating is obviously weakened,and the particles will appear time-delay lifting and intermittent jumping phenomenon.At last,this paper points out the problems existing in the research and the problems to be studied,and makes a prospect of the research on the pollution of metal particles in GIS. |
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