Investigation Of The Dielectric Strength Recovery Property In SF6 Circuit Breaker Considering The Influence Of Shake Wave And Turbulent Flow

The early decades of this century, there is an increasing development for the electrical power system. And the power system will face the great challenges. High voltage SF6 circuit breaker has been considered as the important electrical equipment. The investigation of its key technology covers several subjects, such as electromagnetic, heat and mechanical fields. Focus on it to have theoretical study will have realistic significance for increasing the design level of switch industry.The investigation of interrupting characteristic is very important in development and design of high-voltage circuit breakers. For solving the numerical problem with complex gas flow and space time processing synchronously, the analysis on the flow field of circuit breaker is important for investigating the interrupting characteristic. The arc nozzle of SF₆ circuit breaker is thought as the kernel of arc quenching chamber, because of its controlling effect on gas flow property during the breaking process. In this thesis, the 252kV SF₆ circuit breaker is taken as the investigation subject. The influences on gas flow and dielectric strength recovery properties, which are caused by changing the angle of elevation, the dimension and the contour of arc nozzle of SF₆ circuit breaker, have been investigated. According to the theory of shock wave and the relation between flow velocity(Mach number)and ratio of section area in Laval nozzle, the influences on controlling effect on gas flow and dielectric strength recovery properties, which are caused by local "convergence-divergence" nozzle and "two-segment" contour nozzle, have been investigated for first time. And the dielectric strength recovery properties of different contour and dimension of arc nozzle have been compared. The result shows that the contour of arc nozzle effects remarkably on dielectric strength recovery property during the breaking process.Most of the fluid flow manifests turbulent flow. But some problems have still not been solved or discussed clearly up to now because of its extremely complexity property. In this thesis, various turbulent flow models and nozzle contours have been chosen in numerical simulation to analyze the influences on controlling effect on gas flow and dielectric strength recovery properties, which are caused by turbulent flow, from macro viewpoint. The results show that the gas flow is represent as laminar flow in flat nozzle contour and turbulent flow in scraggly nozzle contour; The local "convergence-divergence" nozzle and "two-segment" contour play an important role in the form and development of turbulent flow; The turbulent flow can reduce the totally velocity of gas flow which is good for the dielectric strength recovery properties.A theoretical basis has been provided for improving the dielectric recovery characteristics of high voltage circuit breaker. The conclusion is very valuable for the optimum design for arc nozzle of SF₆ circuit breaker and miniaturization design for arc quenching chamber.