Influence Of Metallic Particle On Flashover Characteristics Of Spacer In Environment-friendly Gas Insulated Transmission Line

During the production,transportation,assembly and operation of GIL equipment,metallic conductive particles will inevitably remain inside.When these metallic particles meet certain stress conditions under the action of Coulomb force,gravity,electric field gradient force,and friction force,the metallic particles will adhere to the surface of the spacer,causing the electric field on the spacer surface to be distorted,causing the flashover of the spacer and reducing the insulation performance of GIL.In this paper,a spacer flashover test platform is established.The spacer flashover test is carried out in C4F7N/CO2 mixed gas,SF6 gas and Air to study the influence of different parameters of metal particles,mixing gas of ratio and electric field environment on the flashover characteristics of spacers.the test results are analyzed by Combining with the finite element electric field simulation and flashover mechanism.The results show that in the C4F7N/CO2 mixed gas,linear metallic particles are attached to the surface of the spacer.As the metallic particles keep away from the ground electrode,the flashover voltage firstly increases and then decreases;As the length of the metallic particles increases,the flashover voltage decreases continuously,when the metallic particles exceed a certain value,the flashover voltage drop rate slows down;As the metallic particle diameter increases,the flashover voltage continues to decrease.Analyzing the above reasons,the space charge generated by the corona discharge at the end of the metallic particles weakens the degree of distortion of the space electric field;At the same time,the CF3CN molecule generated by the decomposition of the C4F7N/CO2 mixed gas is a substance with high electrical strength and will also promote the flashover voltage Rising.Under different electric field environments,the flashover voltage in SF6 gas is higher than the flashover voltage in 20%C4F7N/80%CO2 mixed gas.When the spacer tilt angle is 90 degrees,the flashover voltage in C4F7N/CO2 mixed gas reaches 96%of the flashover voltage in SF6 gas.The electric field non-uniformity coefficient changed from 1 to 1.42.The flashover voltage in the C4F7N/CO2 mixed gas decrease by about 26%.The C4F7N/CO2 mixed gas was more sensitive to the non-uniform electric field than the SF6 gas.Based on the above studies,this paper analyzes and compares the flashover characteristics of different parameters of particles(attachment position,length and diameter)in C4F7N/CO2 mixed gas,SF6 gas and air,providing a certain test basis for the subsequent application of C4F7N and its mixed gas in GIL.