Natural Commutation Type Hybrid DC Circuit Breaker Based on Hybrid Mechanical Gaps

Hybrid DC circuit breakers (HDCCBs) are promising solutions to DC breaking issues. However, HDCCBs based on forced commutation have the disadvantages of high conduction loss and high cost. Natural commutation HDCCBs have low loss and cost but face the contradictions of high arc voltage and fast post-arc recovery. This paper proposes a natural commutation-type hybrid DC circuit breaker based on a series vacuum and gas gap. The high arc voltage characteristic of the gas gap is used to drive natural commutation, and the fast dielectric recovery characteristic of the vacuum gap is used to withstand transient overvoltage. It has the advantages of low cost and compact volume. The characteristics of the arc voltage of the gas mechanical switch are analyzed, and the influence of different factors, such as the opening speed, arc current, gas type, magnetic field and gas pressure, on the arc voltage of the gas mechanical switch is studied. Moreover, a design method for the gas mechanical switch is proposed. On this basis, a prototype of a 10 kV natural commutation-type DCCB based on hybrid gaps is developed and tested, and the breaking current can reach 15 kA, which verifies the feasibility of the natural commutation method.