GAS INSULATED SUBSTATIONS

1. 7th Sem. Seminar Presentation
2013, EEE Dept.
ROLAND INSTITUTE OOFF TTEECCHHNNOOLLOOGGYY
Gas Insulated
Substations
Under the guidance of
Mr. Preeti Ranjan Sahu
Presented by

2. INTRODUCTION :
Definition :
Usage :
Components :
(SF6) gas :
Safety :
GIS Assembly
GIS advantages and disadvantages :
GIS Requirements :
CONCLUSION :

3. Gas Insulated
Substations
(G.I.S)
INTRODUCTION :
INTRODUCTION Conventional substations requires, small
installation size, protection against atmospheric pollution
and moisture, noiseless operation, nonexplosive and flame
resistant, reduced maintenance, minimal radio interference,
but totally enclosed substations using SF6 gas as insulation
that are also known as GIS is now in widespread use in the
electrical power industry .

4. Gas Insulated Substations
(G.I.S)
• Definition :
• A gas insulated substation (GIS) is a substation that uses a superior
dielectric gas, sulfur hexafluoride (SF6), high-voltage.
• The basic principle of gas-insulated equipment :
• Is that the high-voltage current- carrying parts are within a metal
enclosure and are held in a concentric configuration by cast epoxy
spacer insulators.
• The space between the conductor and the enclosure is filled with
sulfur hexafluoride gas under moderate pressure.

5. Gas Insulated Substations
(G.I.S)
• Usage :
• Gas insulated substation mainly
used for a power transmission
system or a substation system,
of which outgoing bus-bar is
shortened to reduce
consumption of the outgoing
bus-bar.
• The equipment can be designed
for any bus scheme.

6. Gas Insulated Substations
(G.I.S)
• Components :
• 1 → Circuit breaker.
• 2 → Disconnector (Isolator).
• 3 → Ground switches.
• 4 → Bus-bar.
• 5 → Transformer.
• 8 → Outgoing bus-bar for electr-ically
connecting the gas insul-ated
substation with bus-bar.
• 9 → Outgoing portion of the tra-nsformer
being arranged in accor-dance
with extendingdirection of
outgoing bus-bar.

7. Gas Insulated Substations
(G.I.S)
• (SF6) gas :
• The dielectric medium is the sulfur hexafluoride (SF6) gas,
• SF6 has been used as an insulating medium inelectronic devices, power
apparatus, and HVDC converter stations.
• Its excellent properties make it ideally suited both as an insulating and as
an arc-quenching agent.
• SF6 gas is colorless, odorless, chemically inert, nontoxic, nonflammable,
and non-corrosive.
• Its dielectric strength is greatly superior to that of air, and it is close to 100
• times as effective as air in quenching an electric arc.

8. Gas Insulated Substations
(G.I.S)
• Safety :
• The live parts and supported on at resin insulators. Some of the
insulators are designed as barriers between neighboring modules such
that the gas does not pass through them.
• The GIS has gas-monitoring system. The gas density in
eachcompartment is monitored.
• If pressure drops slightly, the gas is automatically tapped up with further
gas leakage, the low-pressure alarm is sounded or automatic trippingor
lock-out occurs.

9. Gas Insulated Substations
(G.I.S)
GIS Assembly:
ESSENTIAL PART OF GIS
1.Bus bar
2.Circuit breaker
3.disconnector(line or bus)
4.Earthing switch(line or bus)
5.Current transformer(feeder/bus)
6.Voktage transformer(feeder/bus)
7.Feeder disconnector
8.Feeder earthing switch

10. Gas Insulated Substations
(G.I.S)
• GIS advantages and disadvantages :
• GIS Disadvantages :
• 1. Excessive damage in case of internal fault. Long outage periods as the
repair of damaged part at site may be difficult.
• 2. Requirement of cleanliness is very stringent. Dust or moisture can
cause internal flashovers.
• 3. Such substations are generally indoor, so they need a separate
building. This is generally not required for conventional outdoor
substations.

11. Gas Insulated Substations
(G.I.S)
• GIS advantages and disadvantages :
• GIS Disadvantages :
• 4. Procurement of gas and supply of gas to site is problematic, adequate
stock of gas must be maintained.
• 5. Project needs almost total imports including SF6 Gas. Spares
conventional substation is totally indigenous up to 400 kV.

12. Gas Insulated Substations
(G.I.S)
• GIS advantages and disadvantages :
• GIS Advantages :
• 1. Reduced required space: The space occupied by SF6 installation is
only about 8% to 10 % of that a conventional outdoor substation. High
cost is partly compensated by saving in cost of space. A typical
(420/525) kV SF6 GIS requires only 920m2 site area against 30000
m2 for a conventional air insulated substation.
• 2. Reliable: The complete enclosure of all live parts guards against any
impairment of the insulation system.

13. Gas Insulated Substations
(G.I.S)
• GIS advantages and disadvantages :
• GIS Advantages :
• 3. Reduced maintenance and consequently, lower costs.
• 4. The safety is increased: As the enclosures are at earth potential
there is no possibility of accidental contact by service personnel to live
parts.
• 5. From 30 kV to 500 kV they might result cheaper than conventional
units. High flexibility and application versatility provide unique, and
economic overall concepts.

14. Gas Insulated Substations
(G.I.S)
• Hence, to solve this problem, smaller installations are needed, which
should also comply the following requirements:
• 1. They shall be insensible to climatic influences.
• 2. They can be raised outdoors, inside a building or underground.
• 3. They require reduced maintenance.
• 4. They are silent.
• 5. They should not generate radio-electric disturbances.
• 6. They shall not imply danger for the nearby populated.

15. Gas Insulated Substations
(G.I.S)
• GIS Requirements :
• The following requirement are important to satisfy, the
requirement of GIS can be summarized as :
• 1. Conductors which conduct the main circuit current and transfer power
these are of copper or aluminum tubes.
• 2. Conductors need insulation above grounded enclosures, conductors
also need phase to phase insulation, in SF6 requirements are met by
cast resin insulators and SF6 gas insulation. GIS these insulation
• 3. Gas filled modules have nonmagnetic enclosures, enclosures are of
aluminum alloy or stainless steel, aadjacent modules are joined
bymeans of multi-bolts tightened on flanges.

16. Gas Insulated Substations
(G.I.S)
• GIS Requirements :
• 4. Various circuit components in main circuit are: CB, Isolator,
Earthingswitches for conductors, CTs, VTs, cable-ends, Bushing-ends and
Bus-Bars, each of these main components has its own gas -filled metal
enclosed module.
• 5. Gas filling, monitoring system.
• 6. Auxiliary low voltage DC and low voltage AC supply system, control,
protection and Monitoring systems.
• 7. The bus-bars are conducting bars to which various incoming
andoutgoing bays are connected. In SF6 GIS the bus-bars are
laidlongitudinally in GIS hall. The bays are connected to bus-bars cross-wise,
bus-bars are either with a three-phase enclosure or single phase
enclosure.

17. Gas Insulated
Substat(iGo.In.Ss)
CONCLUSION :
CONCLUSION GIS are some important areas to be studied include more
conservative designs better particle control&improved gas
handling&decomposition product management techniques
Achieving&maintaining high levels of availability requires a more
integrated approach to quality control by both users and manufactures

18. ANY
QUERIES…