Research On Insulation Failure Of Metal Particles In DC GIL

As a new type of transmission technology,gas-insulated metal-enclosed transmission lines are widely used around the world.One of the research hotspots is the internal insulation problem of GIL systems,including the metal particles generated during the transportation,assembly and operation of GIL,and the freedom of charge during high-voltage operation The gas breakdown caused by the movement and the flashover of the insulator along the surface.This paper focuses on the DC GIL harmful metal particles and the typical problems of its insulating insulation failure,pilot studies and cause the movement of particles from the insulator surface flashover,respectively,the main contents are as follows:（1）The force model of the electric field of metal particles at different positions in the GIL coaxial cylindrical electrode structure is established,and the force of the metal particles is analyzed.A test platform for metal particle motion observation was built,and the test steps and image processing methods were determined.Simulation study on electric field distribution inside the test chamber of coaxial cylindrical electrode.（2）Experiments were carried out on the free-moving metal particles inside the DC GIL.By changing the particle size,SF₆ gas pressure,polarity,etc.,the movement laws of metal particles under different test conditions were analyzed.The results show that:the lifting field strength of metal particles is positively correlated with its radius;the lifting method of metal particles is closely related to its length and SF₆ gas pressure;when the polarity is negative,the particles tend to fly around the guide rod,and the particles will The surface climbs up or collides with the surface,and the presence of the insulator has no obvious effect on the axial movement of the particles.（3）In order to study the effect of linear metal particles on the DC flashover characteristics of basin insulators,a metal copper pin is used to simulate metal particles,and the experimental method is used to measure the flashover voltage of the insulator when the metal particles are attached.The gas pressure is considered in the experiment The effect of particle position change and particle length change on the DC flashover voltage of the insulator.The test results show that the variation of flashover voltage on the convex and concave surfaces of the insulator is different.The reason for this difference is due to the different electric field distribution on the surface of the insulator;the experiment also found that as the gas pressure increases,the influence of the metal particles on the flashover voltage of the insulator Significantly.（4）In order to analyze the effect of linear metal particles on the electric field distribution on the surface of the insulator,based on the finite element analysis method,a three-dimensional electric field simulation geometric model of the insulator was established,and the electric field distribution trend of linear metal particles on the surface of the insulator was studied.The position of the particles was considered in the simulation,Particle size and other factors.The simulation results show that the electric field at the end of the linear metal particles adhering to the surface of the insulator is severely distorted,and as the metal particles move away from the high-potential electrode,the distortion effect gradually weakens;as the length of the metal particles increases,the electric field strength at the end of the particles increases approximately linearly.