Air vs Solid SF₆-Free 12kV Ring Main Unit – Which One Fits Your Project?

For decades, sulfur hexafluoride (SF₆) has been the go‑to insulation gas for medium‑voltage switchgear. Its dielectric strength and arc‑quenching ability are outstanding. But there is a catch:SF₆ is the most potent greenhouse gas known, with a global warming potential (GWP) 23,500 times that of CO₂ over a 100‑year horizon.

For projects that cannot afford SF₆ leakage risk, Taili Electric offers two compact, zero-SF₆, maintenance-friendly SF6-free ring main unit solutions: the TLH-12 eco air cabinet and the TLG-12 solid-insulated cabinet. Both rely on vacuum interrupters for arc extinction and eliminate SF₆ entirely, but they differ in structure and best-fit applications.

TLH‑12: The Dry‑Air / Nitrogen Insulated Ring Main Unit

What it is

Key advantages

• Zero greenhouse impact – if the tank is accidentally punctured or develops a microscopic leak, the escaping gas is simply clean air or nitrogen. No environmental penalty, no special recovery equipment.
• Maintenance‑free gas compartment – the welded tank is designed for life‑time sealing, so routine pressure checks and refills are not required.
• Compact footprint – smaller than traditional air‑insulated switchgear, making it suitable for pad‑mounted transformers and compact secondary substations.
• Cost‑effective – among the two SF₆‑free options, the TLH‑12 offers a lower entry price, especially for volume orders.

Things to keep in mind

• Dry air / nitrogen has a lower dielectric strength than SF₆. The tank welding quality and internal shielding must be strictly controlled.
• For high‑altitude installations (above 1,000 m), the insulation distances must be re‑verified.

TLG‑12: The Solid‑Insulated Ring Main Unit

What it is

Key advantages

• Zero leakage risk – there is no gas compartment, so there is simply nothing to leak. This is the ultimate choice when the project must guarantee SF₆‑free operation over the entire life cycle.
• Immune to humidity and condensation – the solid encapsulation protects internal parts from moist air, salt fog, and heavy dust. No internal dew formation, no surface tracking.
• Minimal maintenance – no gas handling, no pressure gauges, no filling valves. Routine attention is limited to external shielding and connection points.
• Extremely compact – the solid‑insulated module allows for smaller cabinet dimensions, which is a decisive advantage in cramped underground chambers or containerised substations.

Things to keep in mind

• The epoxy casting process demands high manufacturing precision – any void or interface defect can affect long‑term reliability.
• Under continuous high‑temperature operation, the semiconductive shielding layer should be periodically inspected.
• Initial cost is higher than the TLH‑12, but this is often offset by lower site‑support expenses.

Comparison Table: TLH‑12 vs. TLG‑12 at a Glance

Which SF₆‑Free Ring Main Unit Should You Choose?

Both the TLH‑12 and TLG‑12 are fully compliant with IEC 62271 series standards and can be OEM‑configured to suit specific project voltage, protection, and metering requirements.

Choose the TLH‑12 if:

• You are procuring large quantities for standard distribution networks or containerised substations.
• The site is not extreme – regular indoor / outdoor temperature and humidity.
• You want a cost‑effective entry into SF₆‑free technology without sacrificing performance.
• You can accept a minor sealing inspection during annual maintenance, and there is no absolute need to eliminate gas containment.

Choose the TLG‑12 if:

• The installation is in a high‑risk environment – underground basements, coastal salt‑fog zones, or persistently condensing conditions.
• The load is critical (hospitals, data centres, key industrial processes) and unplanned outages are unacceptable.
• You want complete peace of mind regarding gas leakage – no gas, no leaks, no exceptions.
• The space budget is extremely tight – every centimetre of cabinet width matters.

Real‑World Perspective: What Project Teams Say

A recent overseas solar project in the Philippines compared both options. The engineering team selected TLH‑12 for the 64 distribution points around the solar farm because the site was open, well‑ventilated, and the local utility accepted dry‑air insulation. For the indoor switching station inside the coastal administration building, they chose TLG‑12 – because salt mist and high humidity had previously caused tracking failures on conventional air‑insulated gear.

This mixed approach is becoming more common: use each ring main unit where it brings the most value.

TAILI Electric: Your Partner for SF₆‑Free Distribution

TAILI Electric offers both the TLH‑12 dry‑air / nitrogen unit and the TLG‑12 solid‑insulated unit as standard products, with flexible customization for export projects. All units are factory‑assembled and fully tested before delivery. Our engineering team can help you:

• Evaluate site conditions and select the most suitable ring main unit
• Adapt voltage, protection, and auxiliary power to local grid codes
• Provide bilingual documentation and remote technical support

Contact TAILI Electric today to discuss which SF₆‑free ring main unit best fits your next project.