Gas Insulated Substation (GIS)

A Gas Insulated Substation (GIS) is a type of electrical substation where the major components such as circuit breakers, disconnectors, voltage transformers, and busbars are enclosed in metal enclosures filled with Sulphur Hexafluoride (SF6) gas or other suitable insulating gases. This design contrasts with the conventional Air Insulated Substation (AIS) where the components are exposed to the surrounding atmosphere.

1.)   Enclosures: GIS enclosures are typically made of metal and are sealed tightly to prevent the escape of SF6 gas and to ensure the safety of personnel. These enclosures provide protection against external environmental factors such as weather, pollution, and wildlife.

2.)   SF6 Gas: SF6 gas is a colourless, odourless, non-toxic, and chemically stable compound. It has excellent insulating properties, allowing for compact designs of GIS. SF6 gas serves as both an insulating medium and an arc-extinguishing agent. When a fault occurs, SF6 gas extinguishes the arc by cooling and de-ionizing the medium between the electrical contacts.

3.)   Circuit Breakers: Circuit breakers in a GIS are used to interrupt or break the flow of electrical current in case of a fault or overload condition. These circuit breakers are enclosed in SF6-filled enclosures and operate in a pressurized SF6 environment. They can be of various types such as gas-blast, puffer type, or spring-operated mechanisms.

4.)   Disconnectors (Isolators): Disconnectors, also known as isolators, are used to isolate equipment from the electrical system for maintenance or repair purposes. They are typically installed in series with circuit breakers and are designed to provide electrical isolation when open. Disconnectors in GIS are also enclosed in SF6-filled enclosures to ensure safety and reliability.

5.)   Voltage Transformers (VT): Voltage transformers, or potential transformers, are used to step down high voltage levels to safer levels for metering and protection purposes. In GIS, these transformers are also enclosed in SF6-filled enclosures to provide insulation and protection against environmental factors.

6.)   Busbars: Busbars are conductive bars used to connect various electrical components within the substation. In GIS, busbars are typically arranged in a three-phase configuration and enclosed in SF6-filled enclosures to maintain insulation and safety.

 

Advantage of GIS:

·       Space saving: GIS occupies significantly less space compared to AIS due to its compact design.

·       Safety: The enclosed design of GIS and the use of SF6 gas make it safer for personnel and equipment.

·       Reliability: GIS Systems are less susceptible to environmental factors, leading to higher reliability and lower maintenance requirements.

·       Environmental Impact: While SF6 gas has a high global warming potential, efforts are being made to minimize its use and develop alternative insulating gases with lower environmental impact.

Overall, GIS offers several advantages over traditional AIS, making it preferred choice for high-voltage substations, particularly in urban areas or locations with limited space.

Top of Form