HXGN Air-insulated Sealed Ring Main Unit

"H" — box-type enclosure,

"X" — ring network,

"G" — air-insulated,

"N" — indoor

HXGN Air-insulated Sealed Ring Main Unit metal-enclosed switchgear designed for 6kV–24kV ring main and radial distribution systems. Unlike SF6-insulated RMUs, this unit uses air as the main dielectric medium, with all live parts enclosed in a sealed, dust-protected metal cabinet.

What does it do?

1. Connects and isolates power loops in secondary distribution

2. Protects distribution transformers via load-break switches and fuse combinations

3. Provides visible isolation gaps for safe maintenance

4. Serves as an economical alternative to gas-insulated switchgear

The HXGN Air-insulated Sealed Ring Main Unit is widely used in applications where SF6 gas is restricted, where frequent visible disconnection is required, or where budget constraints favor a proven, simple technology without compromising safety.

Product Description

Our HXGN Air-insulated Sealed Ring Main Unit is a next-generation air-insulated ring main unit designed for indoor installation in substations, industrial plants, commercial buildings, and rural power distribution networks. Rated voltage ranges from 6kV to 24kV, with a rated current of 630A for main busbars and 125A for fuse-protected transformer circuits.

Core technical features:

1. Air insulation with optimized phase spacing and insulated barriers

2. Sealed enclosure design (IP3X or IP4X) preventing dust and rodent ingress

3. Three-position load-break switch (closed / open / earthed) with visible break

4. Integrated current-limiting fuse protection for transformers (up to 125A)

5. Optional vacuum circuit breaker module for feeder protection

6. Mechanical interlocks preventing incorrect operations

7. Front panel mimic bus with clear position indication

The HXGN Air-insulated Sealed Ring Main Unit offers a transparent, easy-to-inspect design--- operators can visually confirm the open position of the load switch, a feature highly valued during maintenance and lockout/tagout procedures. No special gas handling equipment is required for installation or decommissioning.

Product Parameter (Specification)

Product Feature And Application

Key Features

● SF6‑free and environmentally friendly---Uses only air as insulating medium, no greenhouse gas emissions.

● Visible break---Load-break switch provides a clearly visible isolating gap, simplifying safety procedures.

● Sealed against dust and rodents---Enclosure meets IP3X or IP4X, preventing common causes of air-insulated switchgear failures.

● Compact footprint---Unit width typically 500---600mm, suitable for space-constrained indoor substations.

● Cost-effective---Lower initial investment compared to SF6 or solid-insulated RMUs.

● Simple maintenance---No gas pressure monitoring or refilling required; only visual inspection and contact cleaning.

● Interlock safety---Mechanical interlocks prevent closing the earth switch while the load switch is closed.

Application Scenarios

● Rural and township power grids

● Industrial facilities---Factories, mining sites, cement plants (with dust protection)

● Commercial buildings---Shopping malls, office complexes, hotels

● Small to medium substations---6kV-24kV distribution nodes

● Renewable energy---Small hydro, biomass, and distributed solar (indoor installation)

● Retrofit projects---Replacing outdated air-insulated switchgear with modern sealed units

Q&A

Q1: How does the HXGN Air-insulated Sealed Ring Main Unit perform in dusty environments like cement plants or grain silos?

A: Excellent. The HXGN Air-insulated Sealed Ring Main Unit features a fully sealed enclosure rated IP3X as standard (IP4X optional), meaning no dust particles larger than 2.5mm or 1mm can enter. This prevents tracking and flashovers commonly seen in open-type air-insulated switchgear. We recommend the IP4X version for heavy dust areas, along with periodic external cabinet cleaning.

Q2: Is air insulation reliable in high-humidity coastal regions?

A: Yes, with proper design. Our HXGN Air-insulated Sealed Ring Main Unit uses hydrophobic insulated barriers and creepage distance extended to 240mm (for 12kV) and 360mm (for 24kV). Additionally, the sealed enclosure prevents humid air circulation, and optional anti-condensation heaters can be installed in the cable compartment. We have successfully deployed hundreds of units in southern coastal provinces with 90%+ annual humidity.

Q3: How does this product compare to an SF6-insulated RMU?

A: SF6 RMU are more compact and fully sealed but require gas handling and have higher upfront cost. The HXGN Air-insulated Sealed Ring Main Unit is larger but offers:

● Lower initial purchase price (Generally offers a lower initial investment than comparable SF6-insulated solutions, depending on the configuration and project requirements.)

● No gas leakage concerns

● Visible disconnection for safer maintenance

● Easier decommissioning and disposal

For customers prioritizing low lifecycle cost and environmental impact without extreme space constraints, the HXGN is an ideal choice.

Q4: What fuses are compatible with your HXGN RMU?

A: Our fuse compartment accepts standard DIN 43625 or BS 2692 high-voltage current-limiting fuses. We can supply fuses matched to your transformer protection requirements (typically 6.3A to 125A). Fuse striking pin operation is mechanically linked to the three-position switch for single-phase fault protection.

Production Details

Enclosure and Sealing

The HXGN Air-insulated Sealed Ring Main Unit features a 2.0mm thick cold-rolled steel or optional stainless steel enclosure, finished with electrostatic powder coating (minimum 80μm thickness, RAL 7035 light grey). The coating passes 500-hour salt spray testing. Sealing is achieved through polyurethane foam gaskets on all doors and panels, ensuring IP3X protection. Cable compartments are separately sealed from the main switch compartment to prevent arc propagation.

Load-Break Switch Design

The three-position load-break switch is a rotating blade type with self-cleaning silver-plated contacts. The arc extinguishing chamber uses a magnetic blow-out principle combined with insulated arc chutes, enabling interruption of up to 630A load current and making/breaking of cable charging currents (up to 10A). The switch has two visible break positions (open and earthed) and one closed position — all clearly indicated on the front mimic panel.

Fuse-Combination Unit

For transformer protection, our HXGN Air-insulated Sealed Ring Main Unit integrates a fuse compartment with a striker-operated trip mechanism. When one phase fuse operates, the striker mechanically triggers the load-break switch to open all three phases, preventing single-phase operation. The fuse compartment is interlocked with the earthing switch — the compartment can only be opened when the load switch is open and the earth switch is closed.

Insulation System

All busbars and connections are insulated with heat-shrink tubing (creepage-enhanced type) or epoxy powder coating. Phase barriers are made of DMC (dough molding compound) or SMC (sheet molding compound) with arc resistance rated Class 1 according to IEC 60243. The minimum air clearance is:

● 12kV: 125mm between phases, 100mm to earth

● 24kV: 220mm between phases, 180mm to earth

Quality and Testing Assurance

Each HXGN Air-insulated Sealed Ring Main Unit undergoes routine tests before delivery:

● Main circuit resistance measurement (micro-ohmmeter)

● Power-frequency withstand voltage (42kV/1min for 12kV, 65kV/1min for 24kV)

● Induced voltage withstand test

● Mechanical operation test (200 cycles for each switch)

● Auxiliary circuit insulation test (2kV/1min)

● Enclosure protection verification (IP3X or IP4X probe test)

● Partial discharge measurement (<20pC at 1.5× rated voltage)

After-Sales Service Commitment

Warranty period: 12 months from shipment date (extendable to 24 or 36 months with paid service contract)

Technical support: Lifetime free technical consultation; response within 1 hour of notification