| Brand | Rw Energy |
| Series | RGIS,DFW,XGN15 |
A ring main unit (RMU) is a compact, metal-enclosed switchgear for medium-voltage secondary distribution — typically two ring incomers and a transformer feeder, built to protect, switch and isolate network branches. Rockwell Energy supplies RMUs from 12–24kV, with SF6-free options.
An RMU is the workhorse of urban and industrial MV networks — the unit that connects distribution transformers to the ring, isolating faults and keeping supply flowing.
A ring main unit sits between two live feeders of a ring network and feeds a distribution transformer. It typically combines ring switches on both sides with a transformer feeder that uses a switch-fuse combination or a vacuum circuit breaker. RMUs are rated to IEC 62271 and built in a compact, metal-enclosed, often SF6-filled or, increasingly, SF6-free package for installation in kiosks, basements and pole-mount housings.
Load-break switches connect the unit to both ring feeders, allowing sections to be isolated while the ring stays live.
A switch-fuse or VCB bay protects and switches the distribution transformer fed from the ring.
If a cable faults, the affected section is isolated and the rest of the ring keeps power.
The insulation medium is the biggest differentiator in RMU design today.
Traditional RMUs use SF6 gas, which has a global warming potential around 23,500 times that of CO2. The industry is shifting to zero-GWP alternatives. Rockwell Energy's SF6-free RMU range uses pure air, dry air or solid insulation with sealed vacuum interruption — no greenhouse gas, no F-gas reporting, no recovery cost at end of life. If you are comparing options, read our pure air vs SF6 guide and see the SF6 alternative RMU.
| SF6 RMU | SF6-free RMU | |
|---|---|---|
| Insulation | SF6 gas | Pure/dry air or solid |
| Global warming potential | ≈ 23,500 × CO2 | Zero |
| Interruption | SF6 / vacuum | Sealed vacuum |
| End of life | Gas recovery | Standard recycling |
Representative values; the certified datasheet is prepared on request — contact us.
| Parameter | Typical value |
|---|---|
| Rated voltage | 12kV / 24kV |
| Rated frequency | 50 / 60 Hz |
| Busbar rated current | 630A (up to 1250A on request) |
| Rated short-time withstand | 20kA / 3s (25kA on request) |
| Configuration | 2 ring incomers + transformer feeder (switch-fuse / VCB) |
| Insulation | SF6-free: pure/dry air or solid — GWP 0 |
| Enclosure | Metal-enclosed, for kiosk / basement / pole-mount |
| Standard | IEC 62271-1, -102 / -103 |
It is a compact metal-enclosed switchgear unit for MV ring distribution — normally two ring incomers and a transformer feeder — used to switch, protect and isolate sections of the network.
Typically 12kV to 40.5kV, matching secondary distribution voltages. Higher classes are available on request.
Yes. Sealed vacuum interrupters handle current breaking and air/solid insulation handles voltage, type-tested to IEC 62271.
Yes. We manufacture for distributors and EPCs under OEM/ODM with your nameplate and documentation.
Login
