Views: 0 Author: Zhejiang Shengxian Electric Power Technology Co., Ltd. Publish Time: 2026-05-11 Origin: Site
Medium‑voltage distribution networks face growing demands for reliability, compactness, and low lifecycle costs. Traditional air‑insulated switchgear is vulnerable to humidity, salt fog, dust, and small animals. In contrast, gas‑insulated ring main units (RMUs) use SF6’s superior dielectric properties to shrink footprint while eliminating external environmental risks.
Zhejiang Shengxian Electric Power Technology Co., Ltd., with decades of design and manufacturing experience, developed the RM6‑12 series – a modern, fully sealed SF6‑insulated RMU for 12kV, 50Hz three‑phase systems. It serves ring main or terminal feeder applications in industrial parks, residential communities, schools, parks, and compact substations. Both indoor and outdoor versions are available, and the unit can be integrated into distribution automation (DA) systems.
SF6 (sulfur hexafluoride) is a synthetic, inert, non‑toxic (under normal conditions) and non‑flammable gas. Its molecule is about 146 g/mol (air ~29 g/mol), making it 5 times denser than air. Key electrical properties:
Dielectric strength at atmospheric pressure ≈ 3× that of air.
At equal pressure, withstand voltage is 2.5× that of nitrogen.
Arc‑quenching capability ≈ 100× better than air.
These properties allow the HSM6‑12 to achieve a compact tank size while meeting 12kV insulation requirements.
SF6 is a potent greenhouse gas with a GWP 24,000 times that of CO₂ and an atmospheric lifetime >3,200 years. Decomposition under electrical arcing can produce toxic byproducts if moisture is present. However, the HSM6‑12’s fully sealed stainless steel tank (leak‑tight design and robotic welding) keeps SF6 inside for the product’s entire lifespan, preventing emissions under normal operation. Proper handling during decommissioning is still required – a standard industry practice.
The RMU is available in three functional modules. All modules share the same basic ratings unless noted.
Parameter | Unit | Module C (Load Switch) | Module F (Switch‑Fuse) | Module V (Breaker) |
|---|---|---|---|---|
Rated voltage | kV | 12 | 12 | 12 |
Rated frequency | Hz | 50 | 50 | 50 |
Rated current | A | 630 | 630 | 630 |
Power frequency withstand – phase/earth & across open contact | kV | 42/48 | 42/48 | 42/48 |
Lightning impulse withstand – phase/earth & across open contact | kV | 75/95 | 75/95 | 75/95 |
Rated active load breaking current | A | 630 | – | – |
Rated closed loop breaking current | A | 630 | – | – |
5% rated active load breaking current | A | 31.5 | – | – |
Rated cable charging breaking current | A | 31.5 | – | – |
Rated transfer current | A | – | 1700 | – |
Rated short‑circuit breaking current | kA | – | – | 31.5 |
Additional notes:
Module C (load switch) is used for frequent on‑load switching of feeders.
Module F (switch‑fuse combination) adds a fuse for transformer protection; the switch handles up to 1700A transfer current.
Module V (vacuum circuit breaker) provides full short‑circuit protection up to 31.5 kA.
Uneven electric fields can cause partial discharge and reduce insulation life. The HSM6‑12 addresses this with three deliberate measures:
Main busbar shape – Rectangular copper bar (40×8 mm) with R5 rounded corners instead of sharp edges.
Switch‑fuse combo busbar – Uses a Φ10 solid copper rod, minimizing corona.
Metallic shielding covers – Installed at all busbar connections and fixing points. These shields equalize the electric field and eliminate local overstressing.
Such optimization is typically validated by computer simulation (e.g., finite element method), which Shengxian Electric Power Technology employs during design.
The stainless steel gas tank must remain perfectly sealed for decades. Any leak would degrade insulation and release SF6. Zhejiang Shengxian Electric Power Technology Co., Ltd. uses robotic welding workstations with a proven process:
Step 1: Precision laser‑cut stainless steel sheets.
Step 2: Robotic MIG/TIG welding of tank panels under controlled atmosphere.
Step 3: Automated weld seam inspection (e.g., dye penetrant or helium leak test).
Step 4: Pressure and leak testing before SF6 filling.
Robotic welding ensures consistent penetration, minimal heat‑affected zones, and no human error. The factory also houses dedicated production lines for gas‑insulated switchgear (充气柜) and assembly workshops.
Use: Cable feeder switching, ring loop splitting, and making/breaking load current up to 630A.
Advantage: 100% maintenance‑free, visible break not required for sealed units (optional earth switch integrated).
Use: Transformer protection (e.g., 630kVA to 1250kVA transformers). The fuse clears short‑circuit currents while the switch handles load and transfer currents.
Transfer current 1700A – the maximum current the switch can transfer when the fuse operates in one phase without damaging the switch.
Use: For feeders that require full fault breaking capability, e.g., long cable circuits or where reclosing is needed.
Built‑in vacuum interrupter combined with SF6 insulation ensures high breaking capacity (31.5 kA).
All modules are factory assembled inside the same SF6 tank. Configurations up to 6 ways are typical.
The HSM6‑12 series can be equipped with:
Motor‑operated mechanisms for remote control.
Voltage and current sensors (optional).
Communication interfaces (e.g., RS485, IEC 60870‑5‑104, Modbus).
Feeder terminals for SCADA integration.
This allows the RMU to operate in an automated distribution network – fault detection, isolation, and service restoration without truck rolls.
Aspect | RM6‑12 Solution |
|---|---|
External influences | Sealed tank: no ingress of water, dust, salt, or insects. Works from -25°C to +40°C. |
Personal safety | All live parts enclosed; cannot be touched even if the tank is accidently opened (interlocks). |
SF6 leakage | Robotic welding + helium leak test → leakage rate <0.1% per year (typical industry standard). |
End‑of‑life | Gas can be recovered and recycled; the stainless steel tank is fully recyclable. |
While SF6 has climate impact, the HSM6‑12’s leak‑tight design minimizes lifetime emissions – a responsible approach consistent with EU F‑gas regulations.
The HSM6‑12 SF6 gas‑insulated RMU delivers reliable, maintenance‑free switching for utility and industrial networks. Its robust stainless steel tank, optimized internal electric field, flexible modular options, and robotic‑welded quality make it a long‑term asset. For applications requiring compact size, high immunity to the environment, and low ownership cost, the HSM6‑12 series is a proven solution from Zhejiang Shengxian Electric Power Technology Co., Ltd.
For more technical data, customized configurations, or a quotation, please contact Zhejiang Shengxian Electric Power Technology Co., Ltd.
WhatsApp: +86 19518189808 – Rachel
Website: www.chsxdl.com | yqsxdl.en.made-in-china.com
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