Summary of Merits of SF6 GIS
Disadvantages of GIS:
1- High cost compared to conventional outdoor substation.
2 - Excessive damage in case of internal fault. Long
outage periods as
3 - Requirement of cleanliness is very stringent. Dust or
moisture can cause
4 - Such substations are generally in door. They need a
5 - Procurement of gas and supply of gas to site is
6 - Project needs almost total imports including SF6 Gas.
Configuration of GIS:
The GIS installations are assembled from a variety of standard modules.
Which are joined together by flange connections and plug contacts on the
Conductors. So as to easily permit subsequent disassembly of individual components. Gas-tight barrier insulators in the Switchgear sections prevent neighboring Switchgear parts from being affected by overhauls.
Any maintenance and overhaul work on Switch contacts can be done without removing the enclosure.
With GIS installations, all basic substation Bus-Bar schemes used, in
conventional plant constructions can be realized. Installations with single or
multiple Bus-Bar-also alternatively with a bypass bus-can be made with the
standard modules, including Bus-Bar sectionalizing with disconnects and
Breakers, and Bus-Bar coupling. The two-breaker. One and-a-half circuit
breaker and ring-bus systems can also be realized economically.
The essential parts of a GIS are: -
1 - Conductors which conduct
the main circuit current and transfer power
2 - Conductors need insulation
above grounded enclosures. Conductors also
3 - Gas filled modules have
nonmagnetic enclosures. Enclosures are of aluminum
4 - Various
circuit components in main circuit are: CB, Isolator, Earthing Switches
5 - Gas filling, monitoring system.
6 - Auxiliary LV DC and LV AC supply system, control,
protection and Monitoring
Bus-Bars are conducting bars to which various incoming
The bays are connected to Bus-Bars cross-wise. Bus-Bars are either
with a three-phase enclosure or single phase enclosure.