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Wednesday, 27 August 2014


Last up-dated 16 January 2017

" The Gas Insulated Substation Technology was introduced for the first time in 1968 and is widely used today because of its significant advantages."
Today's power system insists for a more efficient and reliable solution to handle the new challenges. Power Transmission and Distribution in densely populated urban area is a great challenge because of land availability, and low noise and electromagnetic limitations. With the development in technology and enough improvement in substation and switch-gear design, Gas Insulated Lines (GIL) and Gas Insulated Substations (GIS) are finding increasing use under these conditions. These sub-stations are more safe and reliable, requires less maintenance, and have a longer life. They are highly adaptable to individual requirements.  

How they are different from Conventional Sub-stations?

In a GIS, major equipment such as circuit breakers, CTs, PTs, isolators, bus-bars etc are enclosed in a sealed environment of Sulphur Hexafluoride (SF6) gas. Due to the excellent dielectric properties of SF6 gas, the clearance required between phase to phase and phase to earth is much smaller and hence the design is compact. The enclosure is made up of Aluminium which is light in weight and is non-corrosive. Reduced weight of enclosure leads to reduced load on foundations/ floors and thereby reduces the cost also.

Relative merits of Gas insulated substations:

Gas insulated substations have an estimated lifespan of more than 50 years. They have high mechanical stability and resistance to arcing, and hence offers a high degree of personal safety. As these sub-stations are very compact, even larger units of relatively higher voltages are easy to handle during transportation and installation. They can be shipped as completely assembled units, pre-filled with SF6 gas. The control interfaces of these sub-stations enable the connection to any analog or digital control, protection and monitoring system.  

Scope of Gas insulated substations in India

The scope and future of Gas insulated substations in India is quite promising considering the rapid growth in power sector. Bulk power is transmitted at 400/765 kV and still higher voltage to come, the scope and opportunity for GIS is quite substantial. 

GIS, which are available in voltage range of 72.5 kV to 765 kV, is preferred for hydro-power plants and coastal area substations because of its compact and enclosed design and low maintenance requirements. In these substations, additional protection against thunderstorm, lightning, static discharge etc is not required. The footprint of a typical GIS is about 10 times less than the conventional air insulated sub-station. Because of the ever increasing land cost, GIS has now become a commercially viable solution in India. 

Prominent Gas insulated substations Projects in the Country

Recently Alstom T&D India (globally known as Alstom Grid) has been awarded to supply two 400/220/66 kV Gas insulated substations at Wangtoo and Gumma in Himachal Pradesh. The scope of the project covers the design, manufacturing, testing and commissioning of the GIS. The same company has been awarded a contract by Power Grid Corporation of India to design, manufacture, install and commission two Gas insulated sub-stations at Betul in M.P. and Navsari in Gujarat. These 400/220 kV substations will help to evacuate the power generated at Mouda STPP and Kakrapar Atomic PP. Alstom T&D India is manufacturing Gas insulated substations in India since 2009.

Similarly another Energy Sector industry L&T construction, in collaboration with Korean company, has successfully commissioned India's first 765 kV gas insulated sub-station in Pune, Maharashtra in 2015. This particular sub-station will enhance the grid connectivity and power transmission in Western India.