Research On Metal Particle Movement And Particle Traps In DC GIS

With the rapid progress of Gas Insulated Switchgear(GIS)and the rapid increase in power transmission energy in China,in recent years,GIS substations have increased significantly and have widely used in power systems.Although the operation stability of GIS is relatively high,GIS will inevitably produce metal particles during production,installation,and operation.The particles will move under the action of electric field force,which will seriously affect the insulation performance of the system.Compared with AC voltage,the problem of particle pollution under DC voltage is more serious.Because the particles are subjected to a single direction of electric field force,the particles make repeated collisions between the cavities,which may cause partial discharge breakdown.In addition,the particles near the basin insulators tend to move to the basin insulators,and some particles will be adsorbed on the surface of the basin insulators,causing partial discharge on the surface of the basin insulators.More seriously,it may cause flashover of the basin insulators and lead to the decrease of flashover voltage,which greatly reduces the insulation performance of the equipment and endangers the safety of the system.Aiming at the problem of particle pollution,the study on the movement characteristics and suppression measures of particles under DC voltage is of great importance.The main research contents of the thesis are as follows.Firstly,the thesis establishes a quarter shell experimental model that is consistent with the change trend of the coaxial cylinder in the radial electric field.The experiment analyzes the motion trajectory and hazards of different shapes and different numbers of particles,and simulates the motion trajectory of the iron ball particles.Experiments verify the correctness and feasibility of the simulation model,and provide a certain basis for the study of particle motion characteristics in a slightly uneven field of GIS.Secondly,the actual size of GIS uneven field model is established to simulate and analyze the influence of different factors on the particle motion characteristics,and the effect of the particle on the basin insulator.Finally,the influence of particle traps on electric field distribution,particle movement and trapping characteristics is analyzed.Studies have shown that in the coaxial cylindrical electrode,no matter how the shape of the particles changes,the take-off voltage and breakdown voltage of the particles increase with the increase of the particle size.For linear particles experiencing four states of standing,bouncing,collision and penetrating motion,the shell of A-shaped flake particles makes a small jump and rotational swing.The take-off voltage and breakdown voltage of the particles decrease with the increase of the number of particles.The movement of iron ball particles goes through two stages: take-off and collision,according to the displacement of the iron ball in the z-axis direction,the correctness and effectiveness of the simulation model are verified by experiments.In the slightly uneven field,the motion of spherical particles mostly goes through three stages: horizontal sliding,take-off and collision.When the voltage amplitude,the initial position of the particle,the particle material,and the particle radius change,the particle’s motion trajectory also changes.The horizontal sliding distance of particles decreases as the applied voltage increases.The closer the initial position of the particle is to the basin insulator,the shorter the horizontal sliding distance of the particle,and the greater the velocity of the particle at the same time.The reasons for the influence of particle radius and material on the trajectory of particles are basically the same,which change the gravity of the particles.The movement of aluminum particles shows great randomness,while the movement ranges of iron ball particles and copper particles are relatively small.For the particles near the basin insulators,they climb on the surface of the insulator after taking off,and then collide with the conductor and bounce back in the cavity to make a resonant motion.For the particle traps installed on the inner surface of the housing,round hole traps have a greater impact on the electric field distortion at the bottom of the trap than rectangular hole traps.The width,depth,and interval changes of the rectangular traps all have an effect on the electric field.The average field strength at the bottom of the trap increases approximately positively with the width of the trap,and decreases as the depth and interval of the trap increase.Because of the electric field distortion caused by trap,the trajectories of particles change,and the width of trap has more obvious effect on the trajectories than the depth of trap.Based on the mentioned above,the analysis shows that the trap value K gradually decreases with the increase of the trap width.Since the increase of the trap width reduces the shielding effect of the field strength,the probability of particle trapping decreases,and the distance between the critical position based on the K value and the take-off point is increased.The trap value K increases with the increase of the particle radius,and the distance between the critical position based on the K value and the take-off point decreases.