Compact Sealed Fully Insulated RMU

The Compact Sealed Fully Insulated RMU (Ring Main Unit) is a factory-assembled, type-tested metal-enclosed switchgear. It integrates load-break switches, vacuum circuit breakers, fuses, and earthing switches into a single fully sealed and fully insulated stainless steel tank.

What does it do?

Connects and isolates power loops in secondary distribution networks (6kV–24kV)

Provides fault isolation and loop switching for high-reliability power grids

Unlike traditional air-insulated RMUs, this Compact Sealed Fully Insulated RMU uses SF6 or eco-friendly insulating gas as the primary insulation medium, eliminating moisture ingress, dust accumulation, and animal intrusion---making it ideal for coastal, desert, high-altitude, and heavily polluted areas.

Product Description

Our Compact Sealed Fully Insulated RMU is a next-generation ring main unit developed for urban power distribution, industrial parks, wind/solar power plants, and infrastructure projects such as airports and data centers. Rated voltage ranges from 12kV to 24kV, with a rated current of 630A for main busbars and 125A for fuse-protected circuits.

Core technical features:

1. Fully sealed stainless steel tank (IP67 protection rating)

2. SF6 gas insulation (or alternative eco-friendly gas)

3. Internal arc classification IAC AFLR 20kA/1s

4. Mechanical life: up to 5,000 operations for load-break switches

5. Integrated cable connection compartments with strain relief

6. Optional remote control and SCADA integration

7. The Compact Sealed Fully Insulated RMU requires no internal cleaning or anti-condensation heating, drastically reducing maintenance costs compared to open-type switchgear.

Product Parameter (Specification)

Product Feature And Application

Key Features

1. Fully sealed, fully insulated---No influence from humidity, salt fog, dust, or small animals.

2. Compact structure---Width typically 350–450mm per unit, saving up to 50% floor space.

3. Arc-proof design---Complies with IAC AFLR 20kA/1s, ensuring operator safety.

4. Maintenance-free for 20+ years---No need for cleaning, drying, or gas refilling under normal conditions.

5. Visible break ---Optional observation window for load-break switch position.

6. High mechanical reliability --- Stainless steel mechanism with sealed bearings.

7. Smart ready --- Can be equipped with PT, CT, and motorized operating mechanisms for automation.

Application Scenarios

● Urban power distribution networks---Residential complexes, commercial buildings, hospitals, data centers.

● Renewable energy projects---Wind turbine step-up stations, solar farm collection lines.

● Infrastructure construction---Airports, subways, tunnels, ports.

● Temporary and emergency power supply---Mobile substations, construction sites.

● Industrial zones---Factories requiring high reliability and low maintenance.

Q&A

Q1: How does the Compact Sealed Fully Insulated RMU perform in high-humidity coastal environments?

A: Excellent. Because the Fully Insulated RMU uses a fully sealed stainless steel tank with IP67 protection, moisture cannot enter the insulation compartment. No anti-condensation heaters are required. This is a major advantage over open-type switchgear, which often suffers from internal flashovers in high-humidity regions.

Q2: What is the gas leakage rate? Do I need to refill during its lifetime?

A: Our manufacturing process includes helium leak testing to ensure a leakage rate of less than 0.1% per year. Under normal operation, no gas refilling is needed within 30 years. A low-pressure alarm is included as an optional feature for early warning.

Q3: Is the Compact Sealed Fully Insulated RMU fire-safe?

A: Yes. The tank is made of 2mm thick stainless steel, and the internal arc test ensures that in the rare event of an internal fault, the arc is contained without ejecting hot gases to the front or sides. For fire-sensitive applications (e.g., hospitals, data centers), we also offer an optional passive fire protection coating.

Q4: Can I integrate this RMU with my existing SCADA system?

A: Absolutely. The Compact RMU supports motorized operating mechanisms, auxiliary contacts, and communication modules (RS485, Modbus, IEC 61850 optional). Real-time position, fault, and pressure status can be remotely monitored.

Q5: What is the difference between your RMU and traditional air-insulated cabinets?

A: Traditional air-insulated cabinets require regular cleaning, large clearance distances, and anti-condensation heating. Our Compact Sealed Fully Insulated RMU eliminates all these requirements — smaller footprint, higher reliability, and lower total cost of ownership over 10–20 years.

Q6: Do you offer a 12-month warranty?

A: Yes, we offer a standard 12-month warranty from the date of shipment, with an option to extend to 24 or 36 months under a paid service contract. During the warranty period, any manufacturing defects are repaired or replaced free of charge.

Production Details

Tank and Sealing Process

The tank of the Compact Sealed Fully Insulated RMU is manufactured from 2mm thick AISI 304 stainless steel, laser-welded and helium-leak-tested. The sealing uses dual O-rings made of hydrogenated nitrile rubber (HNBR), which maintains elasticity for over 30 years without aging or cracking. All bushings are epoxy-cast with embedded shields to eliminate partial discharge.

Insulation and Arc Interruption

The load-break switch operates in SF6 gas at 0.04–0.05 MPa relative pressure. The puffer-type arc extinguishing design ensures interruption of up to 630A load current and making/breaking of cable charging currents. Optional vacuum circuit breaker modules are available for transformer protection, integrated with current-limiting fuses to form a "combo" unit.

Operating Mechanism

The three-position switch (closed / open / earthed) is driven by a spring-assisted mechanical mechanism with a clear position indicator. All moving parts are sealed inside the tank, eliminating oxidation and dust accumulation. The front panel includes mechanical interlocks preventing:

1. Closing the earth switch when the load switch is closed

2. Opening the cable compartment cover when the earth switch is open

Cable Connection and Earthing

Cable compartments are designed for single or parallel cables with stress cone support. Standard cable boxes accept heat-shrink or cold-shrink terminations. An integrated copper earth bar runs through all units, with dual earthing points for safety compliance.

Quality and Testing Assurance

Every Compact Sealed Fully Insulated RMU undergoes routine tests before shipment:

● Main circuit resistance measurement

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

● Lightning impulse test (75kV peak for 12kV; 125kV peak for 24kV)

● Gas leakage test (helium mass spectrometry)

● Mechanical operation test (200 cycles)

● Partial discharge measurement (<5pC)

● Internal arc verification (type test, performed by third-party lab)

● All products comply with IEC 62271-200, GB 3906, GB/T 11022, and GB/T 3804.

Packaging & Delivery

Packaging: Wooden export crates with shock-proof foam and moisture barrier. Each unit is individually wrapped in vacuum-sealed plastic with desiccant bags.

Accessories: Operation handle, earthing kit, spare O-rings, cable lugs, and installation manual.

Delivery: FOB Shanghai or Ningbo. Standard delivery 25–35 days after order confirmation. Air freight available for urgent projects.

Why Choose Lugao Power? — Advantages Over Competitors