Research On Arc Extinguishing Characteristics Of C₄F₇N/CO₂ Mixed Gas

Sulfur hexafluoride is widely used in power systems due to its excellent insulation and arc suppression performance.However,SF₆ has serious greenhouse effect.In order to eliminate or reduce the impact of SF₆ on the environment,scholars around the world have begun to try to find new environmentally friendly gases to replace SF₆.C₄F₇N gas,with its excellent electrical performance and low greenhouse effect,is considered to be the most environmentally friendly gas with the most potential to replace SF₆ which has been widely concerned by researchers since its introduction.However,due to the high liquefaction temperature of C₄F₇N itself,it is necessary to mix the buffer gas with lower liquefaction temperature to reduce its liquefaction temperature.CO₂ is considered to be a commonly used buffer gas.Therefore,it is of great significance to study the characteristics of C₄F₇N/CO₂mixture,especially its arc suppression performance,in the research field of high voltage electrical appliances.In this paper,the research status and trend of SF₆ substitute gas are introduced firstly,and the feasibility of replacing SF₆ with C₄F₇N/CO₂ mixture gas is proposed.Next,the theoretical basis of breaking arc research and the arc model used in subsequent simulations are explained.Taking SF₆,CO₂ and C₄F₇N/CO₂mixture as the research object,the arc models of CO₂,SF₆,C₄F₇N/CO₂mixture gas are established under the conditions of DC power supply,single nozzle and fixed electrode.The reasons for different arcing performance of different gas media are explored.Firstly,the arc characteristics of CO₂,SF₆and C₄F₇N/CO₂ mixed gas were analyzed in terms of arc temperature distribution,voltage distribution,pressure distribution and fluid velocity distribution.Next based on the arc radial temperature distribution,the effective thermal conductivity distribution and the influence of gas material performance on arc characteristics,arc characteristics of three kinds of arc quenching medium are analyzed contrastively,and the differences in arc shape and arc temperature cooling speed are also compared,so as to find the key physical parameters closely related to arc extinguishing performance of the gas,and the arc extinguishing performance of C₄F₇N/CO₂ mixture.On this basis,the arc characteristics of C₄F₇N/CO₂mixture under different influencing factors were studied,and the feasibility of replacing SF₆ with C₄F₇N/CO₂ mixture was studied.The simulation results show the arc characteristics of the two gases and the influence of the variable factors on the arc characteristics of C₄F₇N/CO₂ mixture gas,which provide a theoretical basis for the research and development of a new type of SF₆ alternative gases circuit breaker.