Developments in ring main unit design for improved MV network performance

Ring main units have evolved from their original application as simple MV/LV transformer tee-off points into a much move versatile tool. The key development has been the introduction of low-cost SF/sub 6/ rotating arc circuit breakers with integral earth and testing, as well as advances in communication and control technologies. Further improvements in network security and availability can be achieved by applying the RMU circuit breaker as a sectionalising point.