400 V class high-speed current limiting circuit breaker for electric power system

In Japan, a new network distribution system with advanced protective and operational functions designed to meet the needs of today´s information society is being studied. For this new distribution system, the authors have developed high-speed current limiting equipment using gate turn-off thyristors (GTOs), to lower the breaking capacity of switches and to suppress instantaneous voltage drops. The main components of this equipment are a high-speed vacuum switch and a GTO switch connected in parallel. The usual load current is carried by the vacuum switch. In the case of a system fault, the fault current is commutated to and interrupted by the GTO switch by opening the vacuum switch. The time from fault occurrence to current interruption is less than 1 ms. This response time is about 100 times as fast as that of mechanical breakers. This equipment dose not require a large cooling system and is compact compared with conventional solid-state equipment