| Brand | ROCKWILL |
| Series | RMR,RGIS,REC |
An air-insulated ring main unit purpose-built for secondary distribution — the workhorse of urban and industrial MV networks feeding distribution transformers. No SF6, sealed vacuum interruption, zero GWP.
The ring main unit is the classic secondary distribution device — and this version replaces SF6 with conditioned air insulation for a clean, low-footprint unit.
A secondary air insulated RMU sits at the point where the MV ring feeds a distribution transformer. It combines ring load-break switches on both sides with a transformer feeder (switch-fuse or VCB), all insulated by conditioned air and broken by a sealed vacuum interrupter. With no SF6 in the tank, the unit has zero global-warming potential and fits the typical kiosk, basement or pole-mount housing used across secondary networks worldwide.
Conditioned air sealed in the tank provides clean, breathable insulation with zero GWP.
Sealed vacuum handles transformer and fault currents independently of the air medium.
Built for kiosks, basements and pole-mount housings — the standard secondary-network enclosure.
No fluorinated gas — zero GWP, no leakage reporting, no recovery at end of life.
Air does not displace oxygen; no asphyxiation risk in kiosks and cable pits.
No gas-density top-ups; just sealed vacuum parts and simple pressure monitoring.
Cheaper to own over the asset life: no gas handling, no recovery contractor.
Steel enclosure and copper busbar recycle as standard materials at decommissioning.
Built to your ring layout and brand, with IEC 62271 documentation for tenders.
Representative values; the certified datasheet is prepared on request — contact us.
| Parameter | Typical value |
|---|---|
| Rated voltage | 12kV / 24kV |
| Power frequency withstand | 28kV (1 min) / 50kV (24kV class) |
| Lightning impulse withstand | 75kV / 125kV (24kV class) |
| Rated frequency | 50 / 60 Hz |
| Insulation medium | Conditioned air — SF6-free, GWP 0 |
| Breaking device | Sealed vacuum interrupter |
| 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) |
| Standard | IEC 62271-1, -102 / -103 |
It is a ring main unit for secondary distribution networks insulated by conditioned air instead of SF6, with vacuum interruption — the classic urban/industrial MV transformer feed point.
Yes. When dimensioned and type-tested to IEC 62271 withstand levels, conditioned air holds the same class as SF6 RMUs with sealed vacuum breaking.
Yes. The compact footprint is designed around the typical kiosk, basement and pole-mount enclosures used in secondary distribution.
Yes. We manufacture secondary air insulated RMUs for distributors and EPCs under OEM/ODM with your nameplate and documentation.
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