Analysis On The Energy Separation Nozzle Of High Voltage SF₆ Circuit Breaker And The Dynamic Resistance Chain Arc Model

As a leading product of high-voltage switch, high-voltage SF₆ circuit breaker plays an important role in control and protection of high-voltage, extra-high voltage and ultra-high voltage power transmission system. However, in the short-circuit interruption of high-voltage SF₆ circuit breaker, the interactive effect of electric arc and gas flow will directly affect the interruption performance and media recovery ability of the switch. Therefore, in modern design study of high-voltage SF₆ circuit breaker, accurate establishment of nozzle structure and electric arc model becomes a key point of studies on circuit breaker. Nozzle is the key part of helping blast gas transform from subsonic velocity into supersonic velocity. The current studies on nozzle structure mainly focus on alteration for the molded surface structure and size of nozzle throat and downstream part. In this way, the gas can realize radial kinetic energy exchange in the interruption process and radial temperature gradient will be formed. Besides, energy separation of high pressure gas flow can be realized.A three-dimensional gas flow field physical and mathematical model of describing kinetic characteristics of gas flow in the arc extinguish chamber is established, and numerical solution is gained for the gas flow field of high-voltage circuit breaker containing high-speed rotating gas structure via finite volume method. Meanwhile, this paper also studies the influence of “X-shape” flow deflector in the upstream structure of nozzle on flow parameters in the arc extinguish chamber under interruption of small capacitive current. Based on stream theory, numerical calculation and quantitative analysis are conducted for media recovery characteristic of circuit breaker with and without flow deflector structure. The flow deflector structure will change the gas flow form and flow velocity of gas near the wall decreases; the gas presents strongly swirling flow of large rotational curvature and shows the form of combined vortex motion. Meanwhile, a three-dimensional drag chain arc model is set up; mutual coupling effect among electric field, magnetic field, gas flow field and radiation field is formed, and SF₆ physical property parameters change with temperature and pressure in the arc extinguish chamber. Besides, a strategy of combining realizable k-e turbulent flow equation with wall function is proposed. Meanwhile, secondary development is conducted for computational fluid mechanics（CFD） commercial software based on finite volume method through C++ language self-programming and user-defined macro function by applying the multi-zone subdivision method of combining structured and unstructured grid characteristics. In this way, the influence of gas flow in the arc extinguish chamber with nozzle of flow deflector structure on the electric arc is analyzed.In order to build flow deflector structure, three-dimensional electric field distribution calculation should be conducted for the arc extinguish chamber. Test voltages of different classes are loaded according to DL/T593-2006 electric power industry standards to gain three-dimensional electric field distribution of energy separation nozzle. The influences of nozzles with and without flow deflector structure on the maximum electric field intensity in the arc extinguish chamber are compared. By directing at the specific structure characteristics of rotating gas nozzle, comparison analysis is made for electric field intensity along the internal and external walls of flow deflector nozzle structure and rotating gas nozzle.Based on similarity theory, study is carried out by combining CFD calculation with energy separation effect test. The aerodynamic similarity criterion and similar function expression of circuit breaker are derived via similarity theory equation. A three-dimensional aerodynamic performance model of scale model is established, and numerical simulation is conducted for no-load gas flow field, so as to verify the similarity of theoretical model and practical model. Based on energy separation effect, an experimental platform is set up, and temperature subdivision of vortex flow caused by energy separation effect is measured.Multiple nonlinear dielectric materials exist in the circuit breaker electric field domain, and meanwhile it has strong spatial and temporal heterogeneity. A tiny change of structure in the arc extinguish chamber will cause great changes of the electric field. In order to analyze the inherent properties of electric field, field domain visibility networking method based on visibility principle is proposed, and important information contained in electric field is explored. By establishing a complex network model for uniform electric field of plate electrode and slightly non-uniform electric field of high-voltage SF₆ circuit breaker, the electric field domain distribution is studied by introducing complex network theory. According to the results, uniform electric field network of plate electrode presents characteristics of regular networks, and slightly non-uniform electric field in the arc extinguish chamber of SF₆ circuit breaker under different opening ranges possesses scale-free and small world characteristics which belong to complex network characteristics. Network formation via field domain visibility method inherits some characteristics of electric field. By introducing complex network theory, electric field distribution can be studied from a new perspective.