Electromagnetic Characteristics and Magnetic Arc Blow of Vacuum Multi-breakers in Parallel

The short-circuit breaking demand of the large-capacity generator circuit breaker (GCB) far exceeds the capacity limit of a single vacuum interrupter (VI). Vacuum Multi-breakers in Parallel is an effective solution to enhance the overall breaking capacity. A transient electromagnetic simulation model based on vacuum six-breakers in parallel was established for the million-kilowatt-class GCB. It was found that the magnetic field distribution of the parallel system under the large current was unbalanced, characterized by small center and large edge. On the side away from the center of parallel layout (CPL), the magnetic field strength inside the vacuum arc was greater, and the uneven magnetic field distribution caused the arc electrodynamic force to be eccentric, pointing along the distribution radius toward the CPL. The electrodynamic force will drive the arc to move, which was the main reason for the magnetic arc blow. Further, the effects of distribution radius and contact opening distance on the arc electrodynamic force were analyzed. A larger distribution radius and smaller contact gap contributed to weakening magnetic field coupling between different branches, which suppressed magnetic arc blow and arc bias erosion. In addition, the effect of magnetic arc blow on the erosion morphology of contacts was investigated, revealing the cooperative mechanism of the tractive effect of arc electrodynamic force and the restrictive effect of contact plate grooves on the “triangular bias erosion area”. The conclusions will contribute to the practical application of vacuum multi-breakers parallel breaking technology.