- The Functions and Working Principles of Ring Main Units
- 2015/12/5 DAYA Electric
Ring Main Units (RMUs)
A ring main unit (RMU) is a type of electrical equipment consisting of a set of high-voltage switchgear installed in a steel plate metal cabinet or configured as an assembled compartmentalized ring network power supply unit. Its core components include load switches and fuses, offering advantages such as a simple structure, compact size, cost-effectiveness, improved power supply parameters and performance, and enhanced power supply safety. It is widely used in power distribution stations at load centers (including urban residential districts, high-rise buildings, large public buildings, factories and enterprises) as well as in box-type substations.
RMUs are generally classified into three types based on insulation: air-insulated, solid-insulated, and SF6-insulated. They are used to switch load current, interrupt short-circuit current and transformer no-load current, and handle charging current of overhead lines and cable lines over a certain distance. Serving as key switching equipment for ring network power supply and terminal power supply, they fulfill control and protection functions.
In the cabinet, air-insulated load switches mainly include gas-generating, air-blast, and vacuum types, while SF6-insulated load switches are of the SF6 type. Since SF6 gas is sealed inside the shell, the isolation break formed by it is invisible.
Load switches in RMUs typically require three working positions: cutting off load current, isolating the circuit, and enabling reliable grounding. Gas-generating, air-blast, and SF6 load switches can easily achieve these three positions, whereas vacuum arc-extinguishing switches can only interrupt current but not isolate the circuit. Therefore, vacuum load RMUs are generally equipped with an additional isolating switch in front of the load switch to form an isolation break.
This article is compiled and edited by Daya Electric Group Co., Ltd. (//yardscreeksoaring.com/). Reproduction is permitted with proper attribution.
- Introduction to the Relevant Working Environment of High-Voltage Ring Main UnitsBrief Introduction to High-Voltage Ring Main Units
中文版
Service Hotline：0577-67391666