What gas does GIS switchgear use?
Dec 26, 2025
What gas does GIS switchgear use?The primary gas used in GIS (Gas-Insulated Switchgear) is Sulfur Hexafluoride (SF₆).
Here’s a detailed breakdown of its role and the current context:
Primary Gas: SF₆ (Sulfur Hexafluoride)
- Why SF₆? It is an excellent electrical insulator and has outstanding arc-quenching properties. This allows GIS to be extremely compact, reliable, and safe, as it prevents electrical discharges and quickly extinguishes arcs caused during circuit breaking.
- Key Properties:
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- High Dielectric Strength: About 3 times better than air at the same pressure. This allows for much smaller equipment dimensions.
- Thermal Stability & Inertness: Non-flammable and chemically stable under normal conditions.
- Arc Quenching: Effectively cools and de-ionizes the arc plasma, making it ideal for circuit breakers.
The Environmental Challenge
- Major Drawback: SF₆ is a potent greenhouse gas. According to the IPCC, it has a Global Warming Potential (GWP) 23,500 times greater than CO₂ over a 100-year period, and it remains in the atmosphere for over 3,000 years.
- Regulations: Due to this, its use is heavily regulated under international treaties like the Kyoto Protocol and the EU F-gas Regulation, which mandate strict handling, reporting, and efforts to reduce leaks and recover/recycle the gas at equipment end-of-life.
Alternatives and Future Trends
Due to the environmental impact, the industry is actively developing and deploying SF₆-free alternatives. The main solutions are:
- SF₆-Based Mixtures: Blending SF₆ with other gases (like N₂, CO₂, or O₂) to reduce the total amount of SF₆ and the overall GWP of the mixture. These are often used in Gas-Insulated Lines (GIL).
- Fluorinated Gas Alternatives (g³, AirPlus, etc.): New synthetic gases with >99% lower GWP. The most commercially advanced is g³ (green gas for grid) by GE (now Hitachi Energy), which uses a fluoronitrile-based mixture. Others include AirPlus™ (a fluoroketone-based mixture) from ABB.
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- These gases offer similar performance in existing GIS designs with minimal modifications.
- “Clean Air” or Natural Gases: Using technically pure nitrogen (N₂), carbon dioxide (CO₂), or dry air as the insulating medium. These have GWP = 0 or 1.
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- Trade-off: Their dielectric strength is lower than SF₆, so equipment must be designed with higher gas pressure or larger dimensions. They are increasingly used in medium-voltage (MV) GIS and some high-voltage (HV) applications where space is less constrained.
Vacuum as the Interrupter
It’s important to note that in most modern GIS, the circuit-breaking function is performed in a vacuum interrupter chamber. The surrounding SF₆ or alternative gas provides the insulation between the live parts and the grounded enclosure. So, the gas’s main role is insulation, not primarily arc interruption in this part of the system.
Conclusion:
| Gas Type | Example | Key Feature | Common Use |
| Traditional Standard | Pure SF₆ | Excellent insulation, high GWP | Legacy and many current HV/EHV GIS |
| SF₆ Blends / Mixtures | SF₆/N₂, SF₆/CO₂ | Reduced SF₆ content, lower GWP | Transitional solutions, some GIL |
| Fluorinated Alternatives | g³, AirPlus™ | Very low GWP (~99% less), drop-in solution | New HV/EHV GIS from major manufacturers |
| Natural Gases (“Clean Air”) | N₂, CO₂, Dry Air | Zero or near-zero GWP, environmentally benign | MV GIS, some HV where size is not critical |
In summary, SF₆ remains the most common gas in existing high-pressure GIS due to its unparalleled technical performance.
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