| Brand | ROCKWILL |
| Series | RMR,RGIS,REC |
A medium-voltage ring main unit insulated by conditioned, dry pure air instead of SF6. Delivers 12–24kV ring-network and transformer protection with zero greenhouse-gas impact and sealed vacuum interruption.
A ring main unit (RMU) is the compact switchgear installed at secondary substations for ring-feed incomers and transformer protection. In a pure air insulated RMU, the insulation between live parts and earth — the job SF6 traditionally does — is provided by strictly dried, conditioned air sealed in the tank, while current interruption is handled by a vacuum interrupter. The result is an SF6-free, zero-GWP RMU.
Air is dried and sealed in a welded, pressure-monitored tank. No fluorinated gas, nothing to recover at end of life.
Load-break and fault-level switching use sealed vacuum interrupters — proven, silent and maintenance-light for decades.
Earthed, hermetically sealed enclosure segregates busbar, switch and cable compartments for safe daily operation.
Pure-air design separates insulation and interruption — each handled by the best SF6-free technology.
Two ring-feed cables enter the sealed earthed tank and connect to the busbar.
Conditioned dry air holds off 12–24kV between live parts and earth — zero GWP.
Load-break switches and a switch-fuse / vacuum CB clear load and fault current.
Air pressure, position and SCAD
A interface feed the distribution automation system.
No SF6 means no F-gas reporting, recovery or phase-out risk — future-proof for the next 30 years.
Air does not displace oxygen. No asphyxiation hazard in cable pits, no special gas handling.
No gas-density top-ups. Pressure monitoring plus sealed vacuum parts keep maintenance minimal.
Dimensions and cable entry match conventional RMUs — easy installation and retrofit.
At the end of service the unit is recycled as standard metal-enclosed gear, no special disposal.
Optional condition monitoring and remote control turn the RMU into an intelligent grid node.
Representative values of our pure-air insulated RMU range. The certified datasheet for your project is prepared on request — contact us.
| Parameter | Typical value |
|---|---|
| Rated voltage | 12kV / 24kV |
| Rated frequency | 50 / 60 Hz |
| Insulation medium | Conditioned pure dry air (SF6-free, zero GWP) |
| Arc interruption | Sealed vacuum interrupter |
| Busbar rated current | 630A |
| Rated short-time withstand | 20kA / 3s |
| Configuration | 2–4 ring incomers + transformer feeder (switch-fuse / VCB) |
| Standard | IEC 62271-1, -102 / -103 |
| Degree of protection | Up to IP4X / IP5X, indoor type |
| Monitoring | Air pressure, position; optional SCADA / DA interface |
Send us your single-line diagram, voltage and fault-level requirements. We will reply with a configuration, certified datasheet and export quote within one working day.
SF6 is a potent greenhouse gas; pure air insulation uses strictly conditioned dry air sealed in the tank for dielectric strength, paired with vacuum interruption. Same IEC 62271 class performance, zero GWP.
Yes. The vacuum interrupter handles current breaking — a technology proven across millions of feeders — and the pure-air medium provides steady-state insulation. Units are type-tested to IEC 62271.
Pure-air RMUs are designed to match conventional footprints and cable arrangements, making them a practical replacement when legacy SF6 units reach end of life.
Yes. We serve distributors and EPC companies through an OEM/ODM model—we invite you to learn more about our SF6-free Ring Main Unit (RMU) manufacturing services. We offer a 2-year warranty, with options to extend coverage to 5 or even 10 years depending on the region, and the units have a service life of 30 years.
Read our technical guide: Pure Air vs SF6 Switchgear.https://www.iee-business.com/knowledge/dry-air-vs-sf6-switchgear-which-insulation-medium-5370
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