Hybrid DC circuit breakers (HDCCBs) are among the most promising solutions for DC breaking. HDCCBs based on forced commutation have the shortcomings of conduction loss or high cost, which hinders their large-scale application. HDCCBs based on natural commutation, despite their lower cost and smaller volume, are limited by the arc voltage. Therefore, this paper proposes a type of multibreak mechanical switch applicable for medium-voltage natural commutation HDCCBs. Possessing the advantages of compact size and high arc voltage, the switch consists of a four-break gas chamber and a vacuum chamber, the former of which realizes the series connection of multiple arcs through a bridge contact structure. The vacuum chamber is used to bear the turn-off overvoltage. Combined with high-speed observation methods, the mechanical characteristics and arc characteristics of the multibreak mechanical switch are analyzed, and the influence mechanism of different factors on the arc characteristics of the four-break chamber is revealed. On this basis, a principle prototype of the 15 kV medium-voltage natural commutation HDCCB was developed, and breaking tests were carried out. The breaking current can reach 15 kA, and the breaking time is less than 3 ms.
