Key Technology For Optimizing Surface Insulation Properties Of Spacer In Gas Insulated Transmission Line

Gas Insulated Transmission Line,GIL is a transmission method with large capacity and low loss,the research of GIL has been widely concerned at home and abroad.With the higher power requirements of human production activities and the implementation of a new round of infrastructure policies,it is expected that more GIL covering various voltage levels will be put into operation in the future.With the development of GIL and the improvement of environmental protection requirements,the traditional insulating medium SF6 in GIL has been restricted to use because of SF6 high greenhouse effect index.The new generation GIL,which uses C4F7N and its mixed gas as the insulating medium,has become the focus of electrical equipment manufacturers and research units.GIL will inevitably produce particles during manufacturing,transportation,assembly,operation,etc.The particles will be charged and tend to move toward the spacer due to the electrical gradient force in the GIL.The presence of these particles will affect the charge distribution on the spacer surface and cause the electric field distortion.At the same time,the spacer is a key component in the GIL.The insulating material needs to withstand long-term operating voltage.Its physical and chemical morphology affect the charge dissipation ability of the insulating material and withstand of flashover voltage,which ultimately restricts the GIL’s operating stability.In this thesis,from the perspective of suppressing particles,perfecting the formulation,optimizing the surface morphology,and improving the surface components of insulating materials,relying on National Key R&D Program of China,referring to the engineering practice,surface insulation properties optimizing suggestions in the GIL are put forward,the m ain contents are as follows:The flashover voltage,movement characteristics and distribution of powder particles under the AC voltage of environmentally friendly gas were recorded,and suggestions on the arrangement of particle traps were proposed.The influence of powder particles on insulating material surface property were obtained A downsized GIL particle movement experiment platform was built,using ultrasonic signals,UHF signals,and image recording methods to study the movement and distribution of different meshes of metals,semiconductors,and insulating powder particles in different initial positions under environmentally friendly gases and under AC voltages.According to the distribution characteristics of the of particles,grid and strip traps with different parameters were designed,and the trapping coefficient of the trap is proposed.According to the capturing effect,a combined trap arrangement type was proposed in which a grid-shaped trap with 8 mm width groove is provided under the spacer and shield also a strip-shaped trap with 30 mm width is provided in the remaining part in the GIL.The plasma filler fluorination method was explored,and the filler fluorination modification scheme was determined.A plasma filler fluorination modification platform with DBD structure was built,and the micron AlN filler was fluorinated.The XRD,SEM,FTIR and XPS characteristics of the filler and composite materials before and after the modification were tested.The test results show that plasma fluorination can change the size of the filler,and it can be grafted with fluorine and form a stable CF bond in the composite without changing the crystal structure of the filler.The relationship between the charge dissipation characteristics and the flashover characteristics was analyzed,and a fluorination modification method for the filler was proposed.The relationship between the surface morphology of epoxy resin and the flashover was studied,the roughness control suggestions were proposed.The surface roughness of epoxy resin samples produced by GIL insulator manufacturers were modified.The effects of roughness and the direction of the polished texture on the flashover characteristics of the insulating material along the surface were studied.The relationship between roughness and the traps distribution and secondary electron emission was explored.According to the flashover characteristics of AC and DC voltages in environmentally friendly gas,the optimal value for the insulating materials surface roughness was obtained.That is,the roughness is 1.3 μm,which one direction polished during DC,the texture direction is perpendicular to electric field line.And multi directions polished in AC.Experiment on epoxy resin plasma surface modification was carried out,and modification optimization reference was recommended.Using the aforementioned plasma fluorination platform,the surface of the epoxy resin samples were plasma-treated without changing the material formula.The modification time was changed.Through plasma modification,the surface roughness of the sample was changed,and a large area of fluorine element appeared on the surface.Overly long modification will cause damage to the sample substrate.According to the flashover characteristics of AC and DC in the environmentally friendly gas,the mechanism of the influence of physical and chemical characteristics and flashover voltage is revealed.It is recommended that the flashover voltage can be maximized when treated for 10 minutes.