Development of an Ultrafast Hybrid Circuit Breaker With a Novel Arc-Enhanced Lightweight Mechanical Switch for Low-Voltage DC Applications

The hybrid DC circuit breaker (HCB) is crucial for clearing faults and ensuring a reliable power supply in DC grids. However, the fault current can rise rapidly in the low-voltage DC systems, and existing traditional HCB solutions cannot meet the demands of speed and size due to the structure design of the fast mechanical switch and additional assisted commutation devices. In this letter, a novel arc-enhanced lightweight ultra-fast mechanical switch is proposed for low-voltage HCBs. Compared to traditional fast mechanical switches designed for HCBs, the proposed ultrafast mechanical switch offers an extremely fast inherent opening time and current interruption time by eliminating the unnecessary arc extinguishing chamber and applying an innovative dual-stage motion design. Meanwhile, the structure of double-point contact enhances the arc voltage, enabling faster current commutation to the power electronic switch without any bulky auxiliary device. After parameter design and optimization, a compact 750 V HCB prototype based on the novel ultra-fast mechanical switch is built to verify the feasibility. The prototype has an inherent opening time of 70 μs and can interrupt a 26 kA current within 400 μs.