1. GAS INSULATED
SUBSTATION
POWER STATION PRACTICE
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PRESENTED BY :
AMAN NAFEES
ATIB ALI
MOHD. FAIZAN

2. CONTENTS
 Substation
 Classifications of Substation
 Air Insulated Substations
 Gas insulated substations
 Properties of G.I.S
 Components of G.I.S
 Comparison between A.I.S and G.I.S
 Service conditions of G.I.S
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3. A practical view of a gas insulated substation
MANUFACTURED BY SIEMENS
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4. A SUBSTATION
 An assembly of apparatus installed to control transmission
and distribution of electric power.
 A substation is a place where high-voltage electricity from
power plants is converted to lower-voltage electricity
for homes or factories .
 The voltage is stepped down to distribution levels and the
power is fed into the distribution grid and sent to the final
consumers.
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5. Descriptive diagram of several parts of a substation
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6. Classification of Substations
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7. Classification based on Voltage Levels
 A.C. substations
1. EHV
2. HV
3. MV
4. LV
 HVDC
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8. Classification based on Outdoor or
Indoor
 Outdoor substation : Under open sky
 Indoor substation : Inside a building
Classification based on configuration
 Conventional air insulated outdoor substation
 SF6 Gas Insulated Substation (GIS)
 Composite substations having combination of the above
two
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9. AIR INSULATED SUBSTATION(AIS):
 Air used as a dielectric medium
 Normally used for outdoor substations.
 Easy to expand (in case that space is not an issue)
 Excellent overview, simple handling and easy access.
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10. Air insulated Substation
Open air structure
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11. Major limitations of AIS:
 Large dimensions due to statutory clearances and poor
dielectric strength of air
 Insulation deterioration with ambient conditions and
susceptibility to pollutants
 Wastage of space takes place
 Life of steel structures degrades
 Seismic instability
 Large planning & execution time
 Regular maintenance of the substation required
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12. The need of Gas Insulated Substation
 Non availability of sufficient space
 Difficult climatic and seismic conditions at site
 Urban site (high rise building)
 High altitudes
 Limitations of AIS
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13. THE GAS INSULATED SUBSTATION
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14. A gas insulated substation manufactured by ABB
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15. Introduction
 GIS was first developed between 1968 and 1972.
 Sulphur Hexafluoride (SF6) gas – the primary insulating
medium
 Enclosed in a ground metallic housing.
 Compact, multi-component assembly
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16.  (SF6) gas- superior dielectric properties used at moderate
pressure for phase to phase and phase to ground
insulation
 Preferred for voltage ratings of 72.5 kV, 145 kV, 300 kV
and 420 kV and above.
 Various components include Circuit Breakers, Bus-Bars,
Isolators, etc. housed in metal enclosed modules filled
with SF6 gas.
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17. Properties of SF6
 SF6 is colour-less, odour-less and chemically inert gas
 SF6 is 5 times heavier than air and non-toxic
 Almost water insoluble
 Lifetime – Very long (800 to 3200 years!)
 The dielectric strength of SF6 is approximately 3 times
that of air.
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18. Labelled diagram showing the components of a G.I.S
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19. Components of G.I.S.
 Circuit breaker
 Disconnector (Isolator)
 Ground switches
 Bus-bar
 Gas Density Monitor
 Current Transformer
 Voltage Transformer
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20. Advantages of G.I.S
 Occupies very less space (1/10th) compared to ordinary
substations.
 Most preferred where available area for substation is
small (e.g.: cities, hilly areas).
 More reliable compared to Air Insulated Substations.
 Number of outages due to the fault is less
 Maintenance Free.
 Can be assembled at workshop and modules can be
commissioned in the plant easily.
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21. Growth of G.I.S market
 According to a recent report on the GIS market, the global
gas insulated substation market is expected to grow from
an estimated $14.75 billion to $35.83 billion by 2024
 Rising population, growth in infrastructure &
transportation are a few driving factors
 In several countries, upgrades to the aging transmission
network are also driving the GIS market
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22. Comparison between A.I.S and G.I.S
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23. Comparison between A.I.S and G.I.S
Visual Comparison
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24. On the basis of Construction
Gas insulated
 Uses SF6 for insulation
 use fixed, mounted circuit
breakers
 Can be indoor as well as
outdoor, compact
Air insulated
 Uses air for insulation
 uses three-position draw-out
circuit breakers
 Mostly outdoors, covers
large area
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25. On the basis of Maintenance
Gas insulated
 visually inspected every four
years or more
 GIS units being sealed, are
protected from
environmental damage
Air insulated
 visually inspected every year
to two years
 Inspections include having a
technician torque, draw-out,
clean, lubricate and vacuum
the unit
 checked for visual signs of
copper corrosion
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26. On the basis of Total Cost
Gas insulated
 units tend to cost between
10% to 40% more than
 their sealed technology
means lower installation and
maintenance costs AIS
Air insulated
 offer upfront cost savings
 lifelong
maintenance required
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27. Operating conditions of a GIS
As per IEEE 122,IEEE123 and IEC 62271
 Indoor or outdoor : As per customer
 Elevation above sea level : As per site location
 Design ambient temperature : 40 degree Celsius
 Maximum ambient temperature : 105 degree Celsius
 Maximum Allowable Total Temperature in Celsius
 Internal contacts/joints silver plated and 105
conductor in compact with epoxy insulator
 External surface-accessible 70
 External surface-inaccessible 110
 External surface-normally handled by 50
an operator
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29. References
 https://www.youtube.com/
 http://www.betaengineering.com/
 https://electrical-engineering-portal.com/
 https://www.slideshare.net/
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30. Thank you!!
Questions
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