The Basic Difference
Air-insulated switchgear (AIS) uses air as the insulating medium between live parts, so clearances must be large enough to hold off the system voltage. Gas-insulated switchgear (GIS) encloses live parts in a sealed compartment filled with an insulating gas, most commonly SF6, which allows much smaller clearances.
Comparison
- Space - GIS is far more compact, which is valuable in cities and indoor substations.
- Environment - GIS is sealed against dust, moisture, and pollution, while AIS depends on a clean, controlled environment.
- Access and repair - AIS components are directly accessible, and GIS repair often needs specialist handling of the gas compartments.
- Cost - GIS generally costs more up front, offset by the space it saves.
- Environmental note - SF6 is a potent greenhouse gas, so handling and end-of-life recovery are regulated. See SF6 vs vacuum breakers.
Where Each Fits
AIS remains common in industrial plants and where space is not tight, and GIS suits dense urban or harsh-environment sites. Many air-insulated panels use vacuum circuit breakers.
For breaker and mechanism spares, browse VCB spares or request a quote.