The Research On Arc Characteristics Of Double-break Vacuum Circuit Breakers

In the wake of growing network voltage capacity, more attention has been paid on the research and development of high voltage circuit breakers with good operation performance and high reliability. Vacuum circuit breakers (VCBs) are limited while developing to high-voltage grade because of the saturation effect of vacuum gaps. So the concept of multi-break vacuum circuit breakers has been proposed. The characteristics of vacuum arc are key influence factors related to the interruption performance of multi-break circuit breakers. Thus, the research on vacuum arc of multi-break vacuum circuit breakers has naturally become one of the frontier topics in the field of circuit breakers. Vacuum arcs of double-break circuit breakers during arc period and post arc dielectric recovery period are separately analyzed in this paper, with the help of numerical simulation and experiments. Theoretical support is provided by research results in this paper for the design of double-break vacuum circuit breakers.First, a physical model for erect-typed double-break circuit breakers during the arc time is proposed in this paper. So is a two-temperature Magneto Hydro Dynamics (MHD) model of subsonic vacuum arc plasma during arc period according to mass conservation equation, momentum conservation equation, energy conservation equation, as well as Maxwell equations. A model for axial magnetic field calculation between the gaps of double-break circuit breakers is built in Maxwell14.0. The axial magnetic field values between the gaps of each break are got through calculation and are plugged into MHD model. Then, parameters such as density, pressure, velocity, Mach number and temperature are obtained through numerical simulation using COMSOL software. When comparing the arc of both breaks, more evenly distributed parameters with lower values are found in the break with shorter gap length. The greater the differences of gap length between two breaks, the larger are the differences of parameters. When one break’s gap length is3mm larger than another, the ratio of their maximum heat flux to anode reaches up to1.346. So, the difference of gap length between two gaps should not be too great, or it will go against the regulation and control of vacuum arc.Simultaneously, continuous transition model for post arc dielectric recovery period is built in ATP software. The interruption and breakdown mechanisms are analyzed. Moreover, the influence of different opening velocity of each break on transient recovery voltage distribution is analyzed. If the interrupter closer to ground has longer gap length, the voltage grading can be improved.Finally, the arc images during the breaking process of circuit breakers are captured using CMOS high-speed camera. The calculated light intensities derived from MHD model numerical calculation are compared with arc images. It’s showed that they are in agreement with each other. So, the effectiveness of MHD model is verified. In addition, the arc modes evolution processes for both breaks of double-break circuit breakers are analyzed when two breaks interrupt asynchronously.