A high-voltage ring main unit (HV RMU) is an electrical device that integrates a set of high-voltage switchgear in a steel plate metal cabinet or is configured as an assembled compartmentalized ring network power supply unit. Its core components include load switches and fuses, featuring advantages such as a simple structure, compact size, low cost, improved power supply parameters and performance, and enhanced power supply safety.
HV RMUs are widely used in power distribution stations at load centers (e.g., urban residential districts, high-rise buildings, large public buildings, factories, and enterprises) as well as in box-type substations. Generally classified into two types—air-insulated and SF₆-insulated—they are used to switch load current, interrupt short-circuit current and transformer no-load current, and switch charging current of overhead lines and cable lines over a certain distance. Serving control and protection functions, they are key switchgear for ring network power supply and terminal power supply. Within the cabinet, load switches with air insulation mainly include gas-generating, pressure-gas, and vacuum types, while those with SF₆ insulation are SF₆-type. Since SF₆ gas is sealed inside the shell, the isolation breakpoints formed are not visible.
Load switches in HV RMUs typically require three positions: cutting off load current, isolating the circuit, and achieving reliable grounding. Gas-generating, pressure-gas, and SF₆-type load switches can easily achieve these three positions, whereas vacuum interrupters can only interrupt current but cannot isolate the circuit. Therefore, HV RMUs with vacuum load switches are generally equipped with an additional isolating switch in front of the load switch to form an isolation breakpoint.
This article is edited and organized by DAYA Electric Group Co., Ltd. (https://www.hygraphics.com/). Please indicate the source when reprinting.