Ring Main Unit (RMU) Components Functions Types and Applications - Ring Main Unit (RMU) is a switchgear device used in secondary distribution systems, i.e., between the distribution substation and the end consumer to ensure continuous power supply and isolate the faulty section from the network.
Though RMUs are integral to ring network configurations, their utility extends far beyond. Load switch-based high-voltage switchgear has become increasingly prevalent across non-ring distribution systems; hence, the term “Ring Main Unit” has become widely applied to any high-voltage cabinet that predominantly utilizes load switches.
alfanar Ring Main Units ( RMUs) are a gas insulated, compact, enclosed, and extendable type of MV Switchgear up to 36 KV. The RMUs are installed in a photovoltaic power plant to control and protect the supplied energy from the photovoltaic transformers.
A simplified schematic diagram of RMU is shown in figure below. The incomer as well as outgoing feeders are enclosed in an SF6 environment as to make the design compact. Compatible instrument for monitoring of SF6 gas pressure is mounted on the Ring Main Unit, RMU to monitor the gas pressure.
Indoor as well as outdoor types of Ring Main Units are available. Ring Main Unit comprises of one incomer feeder and one or more outgoing feeder. The incomer feeder is either Vacuum Circuit Breaker or SF6 Circuit Breaker with associated Disconnect Switch and Earth Switch.