Low Gas Interlock System metal enclosed RMU

The Low Gas Interlock System metal enclosed RMU (Ring Main Unit) is a factory-assembled, type-tested switchgear designed for medium voltage distribution networks (up to 24kV). It combines SF6 insulated or SF6-free gas technology with a mechanical and electrical low gas pressure interlock system.

What it does:

The RMU safely connects, isolates, and protects transformers and cable circuits in ring networks. The “Low Gas Interlock System” automatically prevents operation (closing or grounding) when internal gas pressure drops below safe thresholds – eliminating risks of internal arcing due to insufficient dielectric strength. The metal-enclosed construction provides robust physical protection and electromagnetic shielding.

Key functions:

● Load making/breaking

● Earth switch operation with interlock

● Fault current protection (with fuse or relay)

● Low gas pressure alarm and lockout

● Visible isolation under metal enclosure

Every Low Gas Interlock System metal enclosed RMU from Lugao Power complies with IEC 62271-200 and GB/T 3906 standards, ensuring seamless integration into smart grids.

Product Parameter (Specification)

Product Feature And Application

Core Features (with Q&A Section)

Feature 1: Low Gas Pressure Interlocking Mechanism

Prevents closing or earthing when gas density is insufficient.

Mechanical lock + auxiliary contact feedback to RTU.

Feature 2: Metal Enclosed, Fully Sealed Tank

Stainless steel tank with laser welding.

No external exposed live parts.

Feature 3: Integrated Mechanical/Electrical Interlocks

●Load switch – earth switch – front cover interlock chain.

Key-lock and padlock provisions.

Feature 4: Compact & Modular Design

Width as low as 375mm per unit.

Expandable on both sides.

Feature 5: Maintenance-Friendly Gas System

Self-sealing valves; gas pressure gauge with low-pressure zone marked in red.

Applications

1. Secondary distribution networks (residential & commercial complexes)

2. Wind/solar power collection stations (environmental adaptability)

3. EV charging hub switchgear rooms

4. Data center backup feeders

5. Industrial plant ring networks

Q&A---Product Feature Deep Dive

Q1: Does low gas interlock affect normal operation speed?

A: No. Under normal pressure, the interlock is transparent. Only when gas leaks (e.g., due to seal aging) does the lock engage---typically after 10+ years. It adds zero delay during routine switching.

Q2: What is the typical gas refill interval?

A: For SF6 version, >20 years under normal conditions. The low gas interlock will trigger an alarm well before critical level, allowing planned maintenance.

Q3: Is the Low Gas Interlock System metal enclosed RMU suitable for smart grid automation?

A: Absolutely. Each unit provides auxiliary contacts for low gas alarm, lockout status, and switch position---compatible with IEC 61850 via RTU.

Production Details

Manufacturing Process

●Lugao Power Co., Ltd. produces each Low Gas Interlock System metal enclosed RMU in a Class 100,000 cleanroom for gas filling. Key production steps:

1. Tank laser cutting & robotic welding---helium leak test (<1×10⁻⁶ mbar·L/s).

2. Vacuum drying & degassing---moisture content ≤10ppm.

3. Mechanical interlock assembly---5000-cycle endurance test.

4. Low gas interlock calibration---using precision pressure switches and cam mechanisms.

5. Final electrical test---power frequency withstand (42kV/1min for 12kV units).

6. Unique serial number---traceable to raw material certificates.

Quality Control

Every RMU undergoes 100% factory acceptance test (FAT) per IEC.

●ow gas interlock function verified at three pressure points: normal, alarm, lockout.

Partial discharge measurement <5pC at 1.2Ur.

Certifications & Quality Assurance

Why Choose Lugao Power Co., Ltd.?

● 15+ years in medium voltage switchgear.

● Lifecycle support – spare parts guaranteed for 10 years.

● Custom engineering – add remote low gas monitoring, heater, or CTs.

“When you purchase a Low Gas Interlock System metal enclosed RMU from Lugao, you get not just a product, but a partner in network safety.”

Packaging & Delivery

Packaging

1. Individual RMU: Sealed in anti-static PE bag + desiccant.

2. Cushioning: 30mm EPE foam inside wooden crate.

3. Outer crate: Heat-treated plywood (ISPM-15 compliant for export).

4. Marking: Fragile, center of gravity, gas-filled label, interlock warning.

Delivery

1. Port: Shanghai / Ningbo.

2. Lead time: 25 working days for standard 630A units (sample order 15 days).

3. Shipping documents: Packing list, commercial invoice, bill of lading, test reports, interlock calibration certificate.

Gas transportation note

SF6 or eco-gas filled units are shipped as “non-dangerous goods” under UN 3166 (machinery with gas). All valves sealed and protected.

FAQ

Q1: What is the warranty period for the Low Gas Interlock System metal enclosed RMU?

A: Lugao Power provides 12 months from commissioning date or 18 months from shipment (whichever earlier). The low gas interlock mechanism is covered for 5 years.

Q2: Can the low gas interlock be bypassed in an emergency?

A: No-by design. Bypass would defeat safety. Instead, we provide a temporary gas refill kit to restore pressure within 30 minutes. Always follow lockout-tagout.

Q3: Do you provide installation training?

A: Yes. We offer remote video guidance free of charge, and on-site training for orders above 10 units.

Q4: How do I verify low gas interlock function before installation?

A: Use the test port on the gas density monitor. Slowly release gas – at alarm threshold (0.03MPa) you’ll hear an alarm relay; at lockout threshold (0.02MPa) the switch operation shaft mechanically blocks. This is demonstrated in our factory video.

Q5: Is this RMU compatible with SF6-free gas?

A: Yes. Lugao Power offers a Low Gas Interlock System metal enclosed RMU with N2/SF6 mix (70%/30%) or C4-FN based gas. （The gas medium and interlock thresholds are configured according to the selected insulation system.）The interlock pressure thresholds are recalculated for each gas type.