Study On Activity Inhibition And Active Control Of Metal Particles In GIL

High Voltage Direct Current transmission(HVDC)provides its technical solution to the large-capacity long-distance power transmission from energy base to load center in China,due to its unique advantages in long-distance energy transmission.As a power transmission mode with unique advantages in terms of transmission capacity,reliability,land occupation,and environmental protection,the direct current gas insulated metal enclosed transmission line(GIL)has broad prospects.However,the existence of metal particles has seriously restricted the stable operation of GIL,so we must take measures to inhibit its activity and movement.In this paper,the activity and inhibition of the movement of metal particles,i.e.,the electrode coating and the particle trap,are studied.The electrode coating can inhibit the activity of the metal particles by influencing and inhibiting the charging process of the metal particles under the electric stress.The particle trap achieves the capture of moving metal particles through the construction of low electric field and its structural features,so as to achieve the effect of improving the system's dielectric strength.By setting up the charge measurement and movement observation platform of metal particles,we observe the charging and movement of the metal particles on the bare electrode and the coated electrode,propose the "activity index" M of the metal particles and analyze the activity of the particles under different coating conditions.The experimental results show that there is a time lag characteristic when the particles are dielectrically coated,and the time delay under negative polarity is 16%higher than that under the positive polarity.After the lower plate is coated,the particles are charged by conduction and micro-discharge when they are stationary,and the micro-discharge is charged when the particles collide with the dielectric membrane during the movement.After the electrode coating,the starting voltage of the particles can be increased by about 10%,and the "activity index" M of the particle movement can be reduced by 69%-94%.By comparing the movement behavior and the activity index of the metal particles under three different coating modes,it can be concluded that the ground electrode coating should be taken at a positive voltage and the double electrode coating at a negative voltage.In order to study the electric field shielding effect of metal particle trap in GIL and its capture effect on metal particles,a closed and semi-closed coaxial cylindrical electrode experimental platform was set up to simulate the electric field distribution in the actual GIL and construct the corresponding three-dimensional simulation model,The trap parameters are optimized through simulation calculation.Based on this,the particle trap design based on "capture parameter"-Pcap is proposed,and the trap effect of particle traps with different parameters is experimentally studied.The results show that the probability of metal particles being captured increases with the increase of the capture parameters,and the capture probability tends to be stable when the Pcap value is about 0.8.In addition,this paper studies the motion of metal particles near the insulator under DC voltage,determines the particle concentration area,and conducts the targeted trap placement strategy through the control experiment,which not only achieves good results but can guide the engineering design.