It is a high-voltage switchgear housed in a metallic enclosure—either stand-alone or modular in design—where each unit functions as a part of the ring's spine. In essence, the RMU's busbar is a segment of the circular main line, making every installed unit a contributing link in. The main purpose of using a ring main unit is to provide an uninterrupted power supply to consumers even in fault conditions. According to IEC 62271-200 standards, RMUs serve as load connection points in ring-type distribution. Ring Main Units are compact modules that are gas-insulated and sealed, comprising main switching devices and ancillary components to ensure continuous secondary power distribution. The precise arrangement and configuration of components always depend on the particular application and loading. Here, we provide an overview of common substation busbar configurations—Single Bus, Main and Transfer, Double Breaker/Double Bus, Ring Bus/Ring Main, and Breaker and a Half. Without them, this system cannot operate. They ensure reliability in medium voltage networks.
[PDF Version]