The Study On Multi-physical Coupling Field Simulation And Characteristics Of 500kV GIL

With the construction of a large number of hydropower stations,transmission lines river crossing and urban utility tunnel in China,Gas insulated transmission lines(GILs)have been widely used because of its large transmission capacity,low-loss,low environmental impact,long service life,convenient operation and maintenance,high reliability and so on.Calculating the physical quantities and characteristics accurately of operation GIL provides a theoretical basis for its design and operation,which is of great significance to ensure the safe and reliable operation of GIL.Firstly,the mathematical model and mathematical relationship of physical field of GIL is analyzed,and multiphysics simulation mathematical model of GIL is built.Secondly,the multiphysical coupling field model of GIL about electric,magnetic,thermal,flow and force is studied,and simulation results are basically in consistent with the experimental data or theoretical calculations,which is verified the model.Thirdly,the electric-magnetic,thermal-flow and thermal-force distributions of multi-physical fields are analyzed,and the effects of proximity effect,edge effect and compression factor on the simulation results are discussed.Finally,the effects of radius ratio of shell to conductor,load current,ambient temperature and gas pressure on insulation margin,temperature,thermal expansion displacement and so on have been studied,including the relationship between them.Besides,fitting formulas of insulation margin,shell temperature and thermal expansion displacement are proposed,and these characteristics are analyzed further for the structural design and operation management of GIL.The conclusions below are drawn based on this research.The electric field of GIL trends to concentrate on the conductor,and the thermal expansion displacement are nonuniform as well as the temperature.The flow field and thermal field change sharply in the boundary layer region and slightly in the main flow region.The proximity effect and compression factor have little influence on the model,and the edge effect can be neglected when the unit length is longer than 7.5 m.With the increase of radius ratio of shell to conductor,the insulation margin decreases,the temperature increases and the thermal expansion displacement also increases.With the increase of load current,the temperature increases and the thermal expansion displacement also increases.With the increase of ambient temperature,the temperature increases but the temperature rise of relative ambient temperature is basically unchanged,and the thermal expansion displacement increases.With the increase of gas pressure,the insulation margin increase,the temperature decreases and the thermal expansion displacement decreases.These research results contribute to providing theoretical basis for product design and operation management of GIL,which is of great significance for ensuring the safe and reliable operation of GIL.