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What is the difference between GIS and AIS?
Nov 24, 2017

"GIS"  is just an abbreviation of  "gas-insulated substation",  uses a superior dielectric gas, SF6, at moderate pressure for phase-tophase and phase-to-ground insulation. The high voltage conductors, circuit breaker interrupters, switches, current transformers, and voltage transformers are in SF6 gas inside grounded metal enclosures.

"AIS"--- it's called  atmospheric air insulation,and used in a conventional. AIS requires meters of air insulation to do what SF6 can do in centimeters.

GIS can therefore be smaller than AIS by up to a factor of 10. A GIS is mostly used where space is expensive or not available. In a GIS the active parts are protected from the deterioration from exposure to atmospheric air, moisture, contamination, etc.

As a result, GIS is more reliable and requires less maintenance than AIS.