Study On Insulation Characteristics And Application Of Eco-friendly CF₃I Gas Mixture

So far,environmentally friendly SF₆ substitute gas has been widely studied,and trifluoroiodine methane?CF₃I?has been widely considered as one of the most likely substitutes for SF₆ due to its excellent electrical properties and physicochemical properties.The basic insulation characteristics,physical and chemical properties of CF₃I gas have been widely recognized.However many works have been not researched,especially on the application of CF₃I mix gases in high-voltage equipment.In this paper,the theoretical calculation method,simulation iteration,basic insulation test,equipment optimization and characteristics researches and other aspects of comprehensive research,formed a more systematic research framework for CF₃I and its mixed gas application characteristics,to provide help for del the environment-friendly gas product application technology development.First,we compared the differences of key transport parameters of CF₃I,SF₆ mixed with N₂ and CO₂.CF₄ through the calculation of Boltzmann equation.The influences of the type and proportion on the macroscopic characteristics can effcetviely provide criteion for the subsequent selection and optimization of gas mixture.Simulation results show that N₂ is the best option of buffer gas mixed with CF₃I based on the insulation performance.Based on solving parameters of Boltzmann equation and partial differential equation with coefficient method,the parameter values of the discharge process are calculated innovatively.The effects of the electric field distribution,gas type and pressure,electrode shape and the electric field of the stream on the actual discharge process are considered.The design and the optimization of key parameters such as structure modeling,parameter definition,multiple physical fields and boundary setting were carried out according to the actual test conditions.The calculated results are in good agreement with the measured data,which proves that the simulation method is applicable to the study,interpretation and prediction of the discharge process of such insulation systems as medium-voltage gas insulation equipment and high-voltage combination appliances,and has certain practical value.In order to obtain the key insulation characteristic parameters of gas insulated electrical equipment,the high-pressure tank test device was designed,and the basic insulation characteristic of CF₃I with mixed proportion of application value under high pressure and long gap was carried out.The critical parameters of mixed gas in different basic electrode structures are obtained as important reference data for the design of gas insulation equipment.Based on the basic insulation characteristic data,the structure design optimization,electric field simulation verification and test verification of 126 kV GIS bus and 252 kV voltage grade GIL product were studied.The results show that the environment-friendly high-pressure equipment with CF₃I gas insulation can meet the specific application standards and operation requirements with appropriate proportion of mixed gas and pressure,and with the optimized structure design,and has great application value.This paper also carried out a systematic study on medium voltage gas insulation products,such as the 12 kV/24 kV ring mian unit,12 kV load switch and 40.5 kV C-GIS.By optimization design,gas mixing ratio adjustment and special treatment of composite insulation,these products successfully passed all tests of the insulation.The experimental study of 12kV load switch shows that When the content of CF₃I is greater than 40%,these switches filling with CF₃I mix gases can break successfully 200A of load current.It can been cetified that these mix gases of CF₃I possess certain capability of arc interrupting.Applying high-speed cemara to shoot the arcing process for studying arcing characteristic:when the arc-quenching capability is better with gas-blowing,but it is difficult to interrupting the arc without gas-blowing.At the same time,it can been found that the synchronism of three phases operation and overshoot,rebound of the operation mechanism heavily influence the arc-quenching capability.