Ultra-fast switches- a new element for medium voltage fault current limiting switchgear

In the past many uneconomic solutions for fault current limiting circuit breakers (FCLCB) have been introduced. Among them, a promising hybrid system has been published, wherein a combination of fast switches, power semiconductors and a resistor forms a very effective FCLCB. This paper presents a significantly improved and simplified approach that replaces the semiconductors with ultra-fast switching elements. Laboratory tests and computer simulations verify the feasibility of this approach. Its elegance lies in the simplicity of the switches and in the improved use of the characteristics of the switching arc over many series breaks, namely cathode-fall and instantaneous recovery. In addition, an ultra-high speed repulsion drive provides an extremely short breaking time (a few 100 microseconds) and the contact separation scatter is within microseconds. These features are the basis for a completely new approach to creating medium-voltage switchgear, and are particularly suited for fault-current limitation.