基于电弧磁流体仿真的 DC 1 500 V 两极塑壳断路器气道优化设计

Solar photovoltaic, wind farms and many other new energy power generations are developing rapidly in China to realize the ‘Carbon Peaking and Carbon Neutrality Goals’. Especially the 1 500 V PV power generation solution gains the most attention because of its high energy density and efficiency. Due to the increment of the system voltage level, system protection for a short circuit also becomes more difficult. However, there is still a vacancy of a reliable, compact, and inexpensive DC circuit breaker for the DC 1 500 V PV systems, and quadrupole-series AC circuit breakers are used as a temporary stand-in for customized DC circuit breakers, which brings large volume and mass heat generation. Therefore, a new-type two-pole DC molded case circuit breaker prototype is developed for PV and energy storage applications. The distribution of all the components is changed, and the arc chambers and contact gaps are placed along the longest side of the circuit breaker to use as many arc chutes as possible in every single pole for the high-voltage arc extinction. Although the new structure theoretically improves the breaking capacity of the single poles with a very compact volume, the small dimension also limits heat dissipation and gas flow, finally limiting arc cooling and extinction. Hence, designing an appropriate arc chamber to realize smoother gas flow and faster arc movement is critical to developing the new DC 1 500 V two-pole circuit breaker. Firstly, experiments of DC 1.5 kV/15 kA with a time constant of 10 ms are carried out. It is found that the speed of arc voltage climbing to 350 V greatly affects the performance of the current limiting and interruption of the circuit breakers. To accelerate the arc movement and arc voltage increment, a 2-D arc magneto hydrodynamics (MHD) model of the contacts part is built to calculate the temperature, pressure distribution, and the fluid velocity variation. The simulation results indicate that the mechanism of arc immobility is the gas blocking between the contacts and the inlet of the arc chamber. Irregularly distributed arc chutes are proposed to release the pressure in the blocking area. There is enough space for the arc to accelerate after its generation to gain enough speed to rush into the arc chutes. Experiments and high-speed movies are carried out to verify the optimization. The irregularly distributed arc chutes release the pressure between the contacts and the arc chamber, making the arc flow into the arc chutes smoother. Furthermore, it is also found that the gas flow is blocked at the outlet of the arc chamber because the gas flow has to swerve sharply here to move forward to the circuit breaker vent. A flow diversion cone is introduced into the arc chamber to guide the flow forcibly and to release the pressure at the outlet of the arc chamber. Experiments are also conducted to verify whether the optimization works. The arc voltage waveforms and the film taken by a high-speed camera show that the flow diversion cone positively affects the arc movement. This paper has great practical meaning in developing the new-type DC 1 500 V two-pole circuit breakers.