Ring Main Unit

HBG-12 Full-Insulation Ring Main Unit

The HBG-12 ring main unit combines cable switching and protection in a compact, fully insulated assembly for 12 kV distribution networks. Its sealed tank uses dry air or high-purity nitrogen as the insulation medium, providing an SF6-free option for urban cable networks and secondary substations.

The 630 A series offers load-switch, switch-fuse and vacuum circuit-breaker functions. The 25 kA designation refers to breaking or short-time withstand duty according to the unit selected. Cable connections and remote-control requirements are defined for the installation.

Technical Specifications

Rated Voltage	12 kV
Rated Current	630 A
Short-Circuit Rating	25 kA (breaking or withstand duty, by unit)
Insulation Medium	Dry air / 99.99% N₂ gas
Switching Units	Load switch / switch-fuse / vacuum circuit breaker
Gas Tank IP Rating	IP67

Key Features

Dry-air / 99.99% N₂ gas insulation
No SF6 greenhouse gas
Compact sealed design intended to reduce routine maintenance; inspection follows the equipment manual and site conditions.
For urban cable ring networks

Typical Applications

Hospitals and schools
Residential communities and office buildings
Factories and transport facilities

Installation & Aftercare

Prepare the site, plan routine checks and keep service records.

What needs to be ready before installation?

Catalogue normal conditions: -40 to +40 °C ambient, 24-hour average at most +35 °C, altitude at most 2000 m.
Provide cable termination space, operating access and the specified pressure-relief clearance around the installed assembly.
The gas tank is IP67; separately protect controls and cable compartments against site water, contamination and condensation.

What should operators check during routine rounds?

During rounds, check switching indications, alarms and any fitted gas-pressure indicator against its permitted operating range.

What is covered during planned maintenance?

At planned isolation, inspect external mechanisms, interlocks, cable connections, earthing and enclosure seals; remove accessible contamination.
A pressure alarm or unexplained pressure change needs authorised service; opening or refilling the sealed tank is not routine operator maintenance.

Customization Options

Define the electrical configuration and the details needed for your site.

Network arrangement: Incoming ring circuits, transformer feeders, terminal supplies and future extension requirements.
Switching units: Choose from this model’s listed load-switch, switch-fuse and breaker units; match protection to the transformer or feeder.
Protection & metering: Fuse or relay protection arrangement, CT ratios, metering and fault-indication requirements.
Cable interfaces: Cable count, cross-section, termination type and earthing connections.
Insulation & controls: Dry-air or nitrogen arrangement as listed; operating mechanism, auxiliary supply and remote signalling for engineering review.

Project-specific options and accessories are confirmed in the quotation and approved drawings.