Influence Of Double-break On The Dielectric Recovery Of SF₆Circuit Breaker

Dielectric recovery characteristic is the important point of the study and the difficulty of the circuit breaker. It reflects the breaking performance. The numerical calculations of the dielectric recovery characteristic are the basis of the research of the breaking capacity. In order to improve the SF6circuit breaker breaking capacity, double breaks in series are the important way. However, double breaks in series of SF6circuit breaker is not simply by the electrical connection structure,it will take the the influence on the distribution of electric field and gas flow field. And the dielectric recovery characteristic changed accordingly. The analysis of the electric field and the flow field with the double breakers structure is important to determine the variation of the dielectric recovery characteristic.Based on the energy perturbation method, the equivalent capacitance of the break and the break to the earth are simulated, and the parallel capacitance is determined, furthermore the double-break potential-ratio is obtained. Based on the potential-ratio, the finite element method is used to simulate the asymmetrical3D electric field of the arc quenching chamber with the multiple dielectric media and the parallel capacitors. Compared with the quantitative analyses and the distribution of the electric field intensity of the contacts surface for the550kV single-break and the1100kV double-break arc-quenching chambers, the insulation variation of different arc extinguishing units is obtained, and the simulation basis of the electric field for analyzing the dielectric recovery characteristic and designing the double break in series SF6circuit breaker is provided.Based on the dynamic mesh method, according to the movement and the deformation of the boundary, and the calculation region grid is reformed. Double-breaks SF6circuit breaker opening process is simulated. And the finite volume method is used to numerically simulate the flow field within the SF6circuit breaker which has the characteristics of compressible, viscous, supersonic, and some intricate physical phenomena. Compared with the quantitative description and analysis about the flow field characteristics of the entity arc quenching chamber and the regions of the nozzle, static arcing contacts and moving arcing contacts of550kV single-break and double-breaks, the flow field variations of different flow paths is obtained, and it could be the basis of the numerical field simulation for analyzing and designing the double-breaks SF6circuit breaker.Electric field and the airflow field analysis based media streamer theory, the dielectric recovery characteristic of1100kV "T"-type structure of the double-breaks SF6circuit breaker and the550kV SF6single break circuit breaker have been calculated. And the influence of the double breakers on the dielectric recovery characteristic of SF6circuit breaker has been calculated.