Benefits of GIS Substation over AIS substation

Gas Insulated Substations (GIS) is a compact, multi component assembly enclosed in a ground metallic housing in

which the primary insulating medium is compressed sulphur hexafluoride (SF6) Gas. SF6 gas act as insulating

medium between the conductor and earth metallic part. The introduction of SF6 gas has revolutionized not only

the technology of circuit breakers but also the layout of substations. The dielectric strength of SF6 gas at

atmospheric pressure is approximately three times that of air. It is incombustible, non toxic, colorless and

chemically inert. It has arc-quenching properties 3 to 4 times better than air at equal pressure. Due to above

quality of SF6 Gas the Space requirement of GIS Substation is only 10 to 25 percent of what is required in a

conventional Air Insulated Substation and GIS requires only the 5% volume as compare to the AIS. Gas insulated

substation requires least space in comparison the other option available (Air Insulated Substation and Hybrid

Substation). Bay width required for 400 KV and 220 KV GIS is 3.6 Mtr & 2.0 Mtr. as compare to bay width required

26.0 mtr and 16 Mtr. in case of AIS.

Gas insulated substation are easy for the any extension in future and space requirement is only inside the GIS

room whereas Air Insulated Substation required additional land for Expansion.

GIS has less exposed parts at ground potential due to this reason it is also safe for operation and maintenance

staff. Gas insulated Substation are maintenance free, maintenance is required only on movable parts after 15

years of service.

GIS substation increases the availability and reliability of power system as all parts of GIS are inside the close

metallic enclosure and not affected for environment.

In GIS substation automation system can be easily installed due to its modular design. This type of substation can

be operated from remote end and reduces the operation and maintenance cost.

Comparison between AIS and GIS in terms of Cost

Air Insulated Substation Gas Insulated Substation

Planning and Engineering 100 80

Real Estate 100 25

Primary Equipment 100 120

Secondary Equipment 100 100

Earthwork,Civil work,structures 100 60

Electrical assembly and erection

100 70

Maintenance 100 50

Outage 100 50

Total 800 570

100 69.4