Novel Rotary-gas Arc-blowing Nozzle For SF₆ Circuit Breaker And Its Interrupting Capability Research

For studying on modern design for the high-voltage SF6 circuit breaker, it becomes one of key research subjects to control the movement of gas blow reasonably in order to form the advantageous arc-quenching'environment'in stationary and moving contacts region. The nozzle is an important component to realize gas flow from the subsonic speed to the supersonic transformation. At present, for nozzle structure in each kind of research, mainly emphasis is to change nozzle throat and the downstream profile structure and the size in order to achieve the goal of gas flow control. In this dissertation, a new method for rotary-gas arc-blowing is presented according to the change upstream structure of nozzle throat.The main thought of this method is:The mode of gas flow movement is changed in process of arc-blowing gas flow from the gas cylinder to stationary and moving contacts region by the changing upstream structure of nozzle. It forms the movement mode of axial arc-blowing+rotary-gas arc-blowing when gas flow arrives at the arc region. The function between cooling gas flow and arc is enhanced by the'twistable'movement of rotary component. The axial component guaranteed the arc-blowing gas making arc energy escape to the downstream, thus realizes the promotion of interrupting capability for circuit breaker. The study contents for rotary-gas are as follow.1. Research the upstream structure of nozzle to achieve the design idea for actively controlling gas flow arc-blowing. Two kinds of upstream rotary-gas nozzle structures have been developed. 2. Three-dimensional gas flow field mathematical model for the description of rotary gas flow movement has been established. In study on three dimensional gas flow field mathematical model, in order to reflected accurately arc movement, the three-dimensional energy source dynamic arc mathematical model are proposed; The finite volume method +TVD form to carry on the equation the separated solution is used to enhance the shock wave to be seized and the conservation properties of discrete governing equation.3. Design and research on rotary-gas blades structure nozzle are completed. Gas flow movement under different blade structure and various physical parameter change rule in the interrupter are studied. Based on velocity, density of gas, pressure and Mach distribution in the interrupter, the reasonable numbers of blade and the best angle match are obtained.4. Design and research on rotary-gas grooves structure nozzle are completed. The influence on velocity of gas flow and the density of arc-blowing gas are studied for rotary-gas nozzle with different groove shapes, the number of grooves and the inclination angle of rotary-gas grooves. The change rule studies for various physical parameters along with to stroke are finished. Numeric simulation experiment study under no-load state and short-circuit interrupting has proved that this new type structure nozzle exists the match relations among best groove shape, the number of grooves and inclination angle of grooves.5. In view of 252 kV high-voltage SF6 circuit breaker structure, rotary-gas nozzle structure optimized design has completed. The prototypical product has been trial-manufacture and experimental verify for short-circuit interruption, and it passed T100S(b) short-circuit experiment. The test results have shown that the principle for new type of SF6 circuit breaker design with rotary-gas nozzle is correct and feasible. All of research work has provided theoretical basis and further improvement for new type of SF6 circuit breaker nozzle.