A substation is defined as an assembly of equipment installed to control the transmission and distribution of electric power. A gas insulated substation (GIS) is an electrical substation in a sealed environment with sulfur hexafluoride (SF6) gas as the insulating medium. These substations were developed in Japan since the country is located in a high seismic zone and there was a need for substations, which could be installed in small confined spaces. Gas insulated substations are much more reliable and more efficient than their counterparts air insulated substations. Increasing need for compact and low maintenance power systems led to the emergence of gas insulated substations. Basic components used in assembly of GIS substations are bus bars, circuit breakers, disconnectors, earthing switches, current transformers, voltage transformers, feeder disconnector and control panels. GIS has many advantages over conventional substations. GIS occupies very less space (1/10th) as compared to conventional air insulated substations. Sulfur hexafluoride (SF6) gas used in GIS has high dielectric property, which acts as insulating medium for the high voltage or extra-high voltage substation equipment. Maintenance and operational costs associated with SF6 gas used in GIS are low as it neither ages nor depletes. Electro-negative property of SF6 is the primary reason for its use as an insulation medium in circuit breakers. Hence, gas insulted substations are preferred over air insulated substations.