Numerical Calculation Of Dielectric Recovery Characteristic In High Voltage SF₆ Circuit Breaker

The dielectric recovery characteristic of high voltage SF₆ circuit breaker (HVCB) is the determining factor which can reflect the interrupting capability. And the coupling calculation and analysis of the flow field and the electric field is the major strategy in the theoretical research on the dielectric recovery characteristic. The electrical structure of the HVCB is complex, and there exists multiple dielectric medium, variable flow route and asymmetric structures, therefore, the conventional 2D model can not truly reflect the dynamic variations of the physical and electrical specifications during the practical interruption. And there exist dynamic variation of 3D arc plasma which is effected by the interaction between the flow field and the electric field in the 3D field of the chamber.In order to describe the dielectric recovery characteristic under the impact of 3D multi-physical field during the interruption, HVCB is taken as the investigating object in this thesis. According to the flow field characteristic of CB, the method which incorporates the FVM and TVD scheme is applied to solve the 3D cold gas flow field in HVCB by self-programming. And the program is applied to analyze CFD classical examples, by comparing with the classical solutions, it is verified that the proposed method has strong shock capturing ability and high solution efficiency, and the program is available in 3D flow field calculation of the HVCB.According to the application of the above numerical methods, the cold gas flow field of the rotary gas HVCB with novel blade nozzle is numerically calculated to simulate the gas motion state in the arc quenching chamber during the small capacitive current interruption. Five different blade structures are established and compared with no blade structure, and the rational blade structure is obtained. The distributions and variation property of the mach number, the pressure and the density in the field are analyzed, and the results show that the novel blade nozzle can control the gas flow more efficiently, which is beneficial to increase the interrupting capability of the CB.Moreover, the 3D electric field in the arc-quenching chamber is calculated based on the finite element method, in order to research the impact of the blade structure on the electric field. And the distributions of the electric potential and the electric field strength of different structure are compared and analyzed. The maximum of the electric field strength in the chamber and the electric field strength distribution at the terminal of the contacts are obtained. The results show that the requirement of insulation is reasonable.According to the research above, the dielectric recovery characteristic of flow field of novel rotary gas CB with blade nozzle is numerically calculated and quantificationally analyzed based on the streamer theory. And the result shows the blade structure has better dielectric recovery characteristic.