| With the continuous development of electric construction,the State Grid is expanding continuously,and the capacity of power grid is also increasing.In order to reduce the floor area of transmission corridor,double circuit parallel overhead high voltage transmission lines on the same tower are growing day by day.As an indispensable part of the transmission line,GIS fast grounding switch can safely and reliably cut off the induced current of the fault line,which has become a hot research topic.SF6or SF6 gas mixture is generally used as gas insulation medium in the traditional GIS fast grounding switch.However,it has serious greenhouse effect and serious environmental pollution.Looking for a new type of SF6alternative gas with excellent comprehensive performance is of great significance to the research and development of environmental protection switch products in China.CO2as insulating medium,its GWP value（global warming potential index）is less than one ten thousandth of SF6gas.In 2012,ABB of Switzerland successfully developed the first 72.5k V high voltage circuit breaker with CO2as insulation medium.In 2020,China Ping Gao Group Co Ltd.has successfully developed 126k V fluorine-free environment-friendly gas insulated metal enclosed switchgear.In this paper,the fast grounding switch of 126k V fluorine-free environment-friendly gas insulated metal enclosed switchgear is used as a prototype to study the arc dynamic characteristics and dielectric recovery characteristics during the opening process of CO2environment-friendly GIS fast grounding switch.The main work is as follows（1）Based on the basic governing equation of gas field and gas state equation,the mathematical model of multi-physical field coupling arc is established.Two kinds of GIS fast grounding switch airflow field simulation models are established,one is a direct moving structure,the other is a pressurized air structure.The arc simulation calculation of the breaking process under 0.8MPa pressure was carried out for the two models respectively,and the influence of air blowing device on the temperature,density and pressure in the air chamber of GIS fast grounding switch was analyzed by comparing the calculation results.（2）The influence of different factors on the interruption of electromagnetic induced current by GIS fast grounding switch.Aiming at the breaking process of GIS fast grounding switch in compressed air device,the arc simulation calculation under different speed and pressure is carried out.The influence of different factors on the air pressure characteristics of fast grounding switch is analyzed.（3）According to streamer theory and Pedersen’s critical breakdown criterion,the mathematical model of dielectric recovery is established.Combined with the calculation results of electric field and air flow field of GIS fast grounding switch,the change curve of CO2dielectric recovery intensity with time in back arc chamber is calculated.The influence of different factors on the dielectric recovery characteristics of fast grounding switch is studied,and the minimum opening and closing speed is given to meet the requirements of successful breaking induced current of grounding switch.Finally,the test of GIS fast grounding switch breaking electromagnetic induced current is carried out to verify whether the fast grounding switch can be broken successfully. |
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