Research On Dynamic Arc Zero Zone Characteristics And Influencing Factors Of C₄F₇N/CO₂ Hybrid Gas Circuit Breaker

The suppression of arc generation and development is a key problem in the field of high voltage switches.The SF₆ is widely used in high voltage switches because of its strong electronegativity and its ability to capture free electrons and form negative ions.In recent years,with the improvement of people’s awareness of environmental protection,the greenhouse effect brought by SF₆ has attracted attention.Therefore,it has become an urgent problem to find SF₆replacement gas.Compared with SF₆,the new environmental protection gas C₄F₇N has a short life in the atmosphere and its greenhouse effect is much lower than SF₆,so it has attracted much attention.Because C₄F₇N is easy to liquefy,it is often mixed with buffer gas to reduce the liquefaction temperature.CO₂ is the main buffer gas currently because of its low cost and easy availability.Therefore,the research on the arc characteristics of C₄F₇N/CO₂ gas is particularly important for the research and development of new environmental protection gas switch.The zero zone is the key to the extinction of AC arc.The arc in the zero zone changes rapidly,and the parameters process directly affects the reignition of the media behind the arc.Therefore,it is of great significance to extract the characteristics of the zero-zone arc and analyze the complex electrothermal behavior and influencing factors in the zero-zone of C₄F₇N/CO₂,so as to study the extinction of SF₆ substitute gas.Based on the basic theory of AC arc breaking and the structure of arc extinguishing chamber of real products,a two-dimensional axisymmetric arc model was established with C₄F₇N/CO₂ and SF₆ as the research object.The influence of turbulence on arc development was considered,and the electric field,air field and temperature field were solved coupling.Firstly,the electrical and temperature characteristics of C₄F₇N/CO₂ and SF₆ arc in steady-state combustion stage were studied,and the zero-zone arc input parameters were obtained by the steady-state phase.Then,C₄F₇N/CO₂and SF₆ arc were compared and analyzed from the view of zero zone arc morphology,electrical characteristic parameters and temperature distribution characteristics.The results showed that the zero-zone arc morphology and temperature distribution of C₄F₇N/CO₂ mixture were highly similar to that of SF₆,but the zero-zone arc voltage of C₄F₇N/CO₂ mixture was lower and the zero-zone arc conductivity was higher than that of SF₆.Finally,the zero-zone arc voltage and arc conductance of 10%C₄F₇N/90%CO₂mixture and 5%C₄F₇N/95%CO₂ mixture at 5atm were analyzed by comparing with SF₆.The results showed that the variation of arc voltage and arc conductance of 10%C₄F₇N/90%CO₂ gas was closer to that of SF₆ at 5atm charging pressure.Appropriately increasing the charging pressure could improve the arc extinguishing performance of C₄F₇N/CO₂ mixture gas.The simulation results in this thesis provide some reference for the research of SF₆ alternative gas arc extinguishing and the research and development of new environmental protection circuit breaker,and have guiding significance for the application of C₄F₇N/CO₂ mixture gas in practice.