Air-insulated switchgear (AIS) and gas-insulated switchgear (GIS) are two types of equipment employed in the electrical power distribution and transmission industry. While AIS is commonly used in low and medium-voltage systems, GIS is used in high-voltage systems.
In this article, we discuss their benefits, applications and differences to provide a thorough understanding of AIS and GIS.
Air-insulated switchgear is a secondary power distribution device and medium voltage switchgear that helps redistribute the power of a primary power distributor powered by a high voltage distribution transformer.
AIS controls, protects and isolates electrical equipment in power transmission and distribution systems. The equipment is designed to be operated in the air at atmospheric pressure, which is why the name “air-insulated.”
A gas-insulated switchgear is a composite device enclosed in a solid metal frame comprising electrical devices like transformers, circuit breakers, bus cars, surge arrestors, etc. These components are housed in shielded chambers with barrier devices and submerged in sulfur hexafluoride gas (SF6).
The main uses of a GIS substation are switching, separating, converting, monitoring, and distributing electrical energy in power systems. SF6, an inert gas with high insulating qualities, chemical stability, and thermal stability, is used as the primary component of a GIS device.
AIS (air-insulated switchgear)
GIS (gas-insulated switchgear)
It has a metal-clad system that employs air insulation.
It uses the gas sulfur hexafluoride for insulation. Sulfur hexafluoride is much heavier than air and offers great extinction behavior.
Three-position draw-out circuit breakers are used in the metal-clad AIS.
GIS systems use fixed-mounted circuit breakers.
More economical for low/medium voltage systems.
It is expensive as compared to AIS.
More maintenance cost over a lifetime
Less maintenance cost
The AIS breaker is removable for maintenance & troubleshoot
The breakers here are ‘sealed-for-life.’
AIS systems cover more space
GIS systems cover less space
More installation time
Less installation time
Visual inspections of AIS systems should be done every year to every two years.
GIS switchyards require significantly less maintenance
Gas-insulated switchgear is mainly used in industries with high power demand and limited space to install equipment. However, it can be more expensive in the long term, requiring more specialized tools and skilled professionals to install and maintain.
On the other hand, air-insulated switchgear is a more common and economical alternative for low and medium-voltage systems.