Study On Chaotic Behavior Of Airflow Field Of High Voltage SF₆ Circuit Breaker With Opening Characteristic Curve

The high-voltage SF₆ circuit breaker,as a control and protection switch,plays a decisive role in the reliable and stable operation of the entire power system?power plant and substation sites?.An arc will be generated during the breaking process of a circuit breaker like other contact switch electrical devices.The spatial and temporal evolution of the arc is chaotic.The study in this paper is based on chaos theory with the airflow dynamics of arc-blowing of high-voltage SF₆ circuit breaker as the research object.The breaker has three-stage zoom nozzle.The unsteady and nonlinear time-series diagram of the arc,shock wave and turbulent airflow dynamics are studied.The impact of opening characteristic curve on physical nature and motion pattern of airflow variable's evolution of complex arc-extinguishing systems is also investigated.By applying two-dimensional Fourier series expansion to an mathematical equation describing the air flow pattern of short-circuit arc,a new equation describing the chaotic characteristics of arc and airflow pattern of the breaker has been obtained.The equation has two primary variables:temperature and vorticity.The existence of chaotic characteristics of the arc and air motion pattern of the breaker is verified by analyzing time history diagram,phase diagram and lyapunov exponent diagram.An experimental platform with detachable arc extinguishing chamber is used to collect data such as current and arc voltage during the arc's breaking process.The collected data then is processed by using the C-C algorithm.Experiments show the chaos of arc and air motion system will appear when both the rated current and the arcing speed of the circuit breaker reach certain values;the maximum lyapunov exponent value will be also getting higher while the rated current and arcing flowing speed inrease.The method of stacking grid is used to simplfy the previous regional griding method and remove the negative volume generated from the grid motion.At mean time,the number of the grid within the calculated fluid area is reduced;the number of disappeared grid is controlled,and the calculation efficiency of the airflow field is also improved.The motion of the grid and air pressure variables are programed in with C++.Based on the finite volume method,the airflow field of the circuit breaker under no-load is modeled.The resulting variable values of the airflow field such as speed,pressure,turbulence are obtained and used to support the improvement of the opening characteristic curve.The opening characteristic curve is corrected on the basis of chaos theory.The speed value of the corrected opening characteristic curve is then discretized and introduced,as a variable,into the UDF for further software development.Thereafter the arc extinguishing chamber and the hydraulic mechanism are simulated together to obtain the corrected variable values and the time series diagram of the place where the shock is generated.Finally the variable values and the diagram are used to understand the influence of the time series variation of bandwidth on the chaos's dynamic behaviorThe work carried out in this paper is of great significance for further optimizing the design and improving the mechanical properties of circuit breakers.