Investigation Of Dielectric Recovery Characteristic And Its Influencing Factors For High Voltage SF6 Circuit Breaker

The investigations of insulation performance and interrupting characteristics are very important in development and design of high voltage SF6 circuit breaker. The research mainly covers the establishment of circuit breaker dynamic arc model, numerical analysis of electric field and flow field of arc quenching chamber as the well as solution of multi-physical coupling field during interrupting period.In this thesis, the electric field of 550kV SF6 circuit breaker with different opening stroke has been calculated and analyzed using the finite element method(FEM).By comparing of five different nozzle structure of arc quenching chamber, the influence of nozzle shape on electric field strength has been obtained and analyzed.Due to the flow field within SF6 circuit breaker has the characteristics of compressible, viscous, supersonic and some intricate physical phenomena, such as the shock wave and vortices during the interrupting, FVM method is applied to simulate the flow field in circuit breaker with multi-stage nozzle structure, in which the dynamic distribution of gas pressure, velocity, mach number with multi-stage convergent-divergent nozzle structure of arc quenching chamber has been simulated and analyzed.Based on the calculation of coupling electric field and flow field, the discharge theory is used to calculate and study the dielectric recovery characteristic of five different nozzle structure. From the calculation results, it can be found that: the key influencing factors of the dielectric recovery characteristic are electric field strength of stationary arcing contact, nozzle structure and shock wave position respectively. And the optimized position(the end of the stationary arcing contact, convergent-divergent level and throat of nozzle)of circuit breaker structure are determined based on the weak point of dielectric breakdown.During the investigation of dielectric recovery character on short current interrupting, based on the dynamic arc mathematical model and the influencing of copper vapors during the arcing period, the thermodynamic characteristics and transports properties of the hybrid SF6 gas and metal vapor is largely different from the pure SF6, different electrical conductivity and radiation has been adopted in different arcing period, which reflects the arc dynamic variation and the interaction between arc and current during the interrupting course. The dynamic distribution of temperature field, pressure field, velocity field varying with opening time and dielectric recovery characteristic are analyzed based on the simulation of the flow field of short current interrupting.