A ring main unit (RMU) is a factory assembled, metal enclosed set of switchgear used at the load connection points of a ring-type distribution network. It includes in one unit two switches that connect both sides of the load to the main conductors and a fusible switch or circuit breaker that tee-off to feed a distribution transformer medium voltage to low voltage (MV to LV).
A Ring Main Unit includes a combination of one or more Load Break Switch (LBS) cum Earth Switch as incomer and outgoing feeder and Vacuum Circuit Breaker with associated Disconnector and Earth Switch for load feeders. All the switching devices and the bus bars are enclosed in a sealed for life SS enclosure filled with SF6 to make the design compact while ensuring a high level of safety and reliability and also a maintenance-free system.
Depending on the requirement, RMU is available in different voltage ratings and are suitable for both indoor and outdoor installation.