In an electrical power distribution system, 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 can connect the load to either or both main conductors, and a fusible switch or circuit breaker and switch that feed a distribution transformer.  The metal-enclosed unit connects to the transformer either through a bus throat of standardized dimensions, or else through cables and is usually installed outdoors. Ring main cables enter and leave the cabinet. This type of switchgear is used for medium-voltage power distribution.

The Precision Service Centre is having an expert team for the maintenance & testing of medium voltage substations.