Study On The Mechanism Of Metal Particles On The Surface Charge Accumulation Of Post Insulators In The DC GIL

DC GIL (Gas Insulated Transmission) is practicable in which the traditional DC overhead line system is limited under certain conditions in power transmission system. Also, the DC GIL has a broad application prospect in constructing the global energy Internet. However, metal particles and surface charge accumulation are two main factors that reduce the insulation strength of DC-GIL. Worsely, the combined action of metal particles and surface charge accumulation will impose huger threat on the DC GIL insulation system.In this paper, aiming at the problem of conducting particle pollution in DC-GIL, the impacts of metal particles contamination on the process of surface charge accumulation are studied. Firstly, based on the Maxwell equations, the mechanism of surface charge accumulation is analyzed theoretically. And further more taking the contamination of metal particles as well as the effects of ions’formation, recombination, migration and diffusion in gas space into account, to establish the microscopic model of the accumulation process of surface charge on insulators by COMSOL, the multi-physics field simulation software. Based on the models the time-dependent effect and the voltage characteristic of surface charge accumulation under DC voltage are analysised. And obtain the influence of metal particle on surface charge accumulation. On the other hand, to verify the validity and reliability of simulation models, a charge measurement platform with rotary detectors is built. Experiments are carried out to research on the time-dependent effect and voltage characteristic as well as the effects of particle size and attachment position of metal particles on the insulator according to the simulation analysis. Deriving from the experimental results, the deteriorating characteristic of GIL’s insulation is investigated when the surface discharge and metal particles are considered. Furtherly, establish entity models of charge accumulation on insulators influenced by metal particles to probe into the distribution characteristics of surface charge when particles are adhering to the insulators or hovering in the cavity.Conclusions drawn from the simulation analysis and experimental results are in accordance with each other when considering the particle contamination, which verifies the reliability of simulation model. To be specific, conclusions included from the research work are shown as follows. Firstly, the surface charge distribution of insulator is consistent with normal component of the electrical field on the insulator. Secondly, the particles adhering to the insulator surface can cause a surge of surface charge. What’s more, the conductive particles attached to the surface of the insulator can cause the accumulation of surface charge surge. In addition, the amount of charge caused by the particles attached to the middle part is more remarkable, and the electrical property of the accumulated charge is opposite to that of the particles, and is also opposite to the electrode of the tip of the particle. On the other hand, the floating particles have little effect on the accumulation of surface charge, and when the distance between a suspended particle and the insulator’s surface is more than 4 times the particle diameter, its effect on the surface charge accumulation can be neglected. In summary, the research conclusions are conducive to deepening the exploration of mechanism of surface flashover and particle induced breakdown in DC-GIL, and providing theoretical guidance for the structural design of DC GIL as well as optimizing particulate harmless measures.