The document summarizes a seminar presentation on gas insulated substations. It begins with an introduction to gas insulated substations, noting they are compact assemblies enclosed in a ground metallic housing with sulfur hexafluoride gas as the primary insulating medium. It then discusses the properties of SF6 gas and its advantages over air as an insulator. The document outlines the typical equipment in a gas insulated substation, including circuit breakers, current and voltage transformers, and busbars. It concludes by listing some advantages of gas insulated substations such as their compact size and reliability compared to conventional air insulated substations.

1. SEMINAR
ON
GAS INSULATED SUBSTATION
PRESENTED BY:
NAME-SUJIT KUMAR MANDAL
BRANCH-ELECTRICAL ENGINEERING,7TH SEM.
REG.NO-1721105030,
ROLL NO.-35342

2. CONTENTS:
•Introduction
•Conventional substations (AIS)
•Limitations of AIS
•The need for GIS
•Introduction to GIS
•Properties of SF6
•GIS Equipment's
•GIS assembly
•Advantages of GIS
•Demerits of GIS
•Conclusion
•References

3. INTRODUCTION:
•Gas Insulated Substation (GIS) is a compact, multicomponent assembly
enclosed in a ground metallic housing in which the primary insulating
medium is compressed SF6 gas.
•The compactness is with the use of SF6 gas, which has high dielectric
strength.
•Gas Insulated Substations (GIS) can be used for longer times without
any periodical inspections.

4. AIS-AIR INSULATED SUBSTATION
•Air used as a dielectric.
•Normally used for outdoor substations.
•In very few cases used for indoor substations.
•Easy to expand (in case that space is not an issue.
• Excellent overview, simple handling and easy access
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5. 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.
•Life of steel structures degrades.
•Seismic instability.
•Large planning & execution time.
•Regular maintenance of the substation required.

6. THE NEED FOR G.I.S
•Non availability of sufficient space.
•Difficult climatic and seismic conditions at site.
•Urban site (high rise building).
•High altitudes.
•Limitations of AIS.

7. GAS INSULATED SUBSTATION
•QIntroduction:
•Compact, multi-component assembly.
•Enclosed in a ground metallic housing.
•Sulphur Hexafluoride (SF6) gas the primary insulating medium.
•(SF6) gas is superior dielectric properties used at moderate pressure for phase to phase
and phase to ground insulation.
• for voltage ratings of 72.5 kV, 145 kV, 300 kV and 420 kV and above.
•Various equipment's like Circuit Breakers, Bus-Bars, Isolators, Load Break Switches,
Current Transformers, Voltage Transformers, Earthing Switches, etc. housed in metal enclosed
modules filled with SF6 gas.

8. PROPERTIES OF SF6:
•QCharacteristics
•SF6 is colourlessly, odourless and a chemical neutral (inert) gas.
•SF6 is 5x heavier than air, is not toxic and has no dangerous components
inside.
•SF6 is no hazardous material.
•SF6 has no eco-toxic potential.
•SF6 has no impact for the ozonosphere.
•qAdvantages for use in GIS
•The dielectric strength of SF6 gas at atmospheric pressure is approximately
three times that of air.
•It is incombustible, non toxic, colourless and chemically inert. It has arc-
quenching properties 3 to 4 times better than air at equal pressure.

9. GIS EQUIPMENT'S:
•Circuit Breaker
•Current transformer
•Voltage transformer
•Feeder Disconnector and Earthing switch
•Bus bar
•Gas density Monitor

10. 72.5 KV GIS ASSEMBLY

11. BUS BAR
•To connect GIS modules that are not directly connected to each other,
an SF6 bus consisting of an inner conductor and outer enclosure is used.
The conductors made of alluminum or copper, depending on the current
rating, are supported by gas tight insulator (for standard bay bus) or
individual supporting insulators (for extended bus).
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12. CURRENT TRANSFORMER
The secondary windings are designed for metering or protection purposes.
One terminal of each used secondary winding and one terminal of unused
winding have to be earthed during the transformer operation (unused
shortcircuited also).

13. POTENTIAL TRANSFORMER
•It is used for protection and measuring.
•They are based on the electromagnetic transformer principle, where primary
and secondary winding galvanically separated from one another.
•Primary winding is wound on the top of the core and the secondary winding.
The letter are connected to the terminals in the external terminal box through a
gas-tight multiple bushing.
•Utilization of Sf6 gas as insulating medium, together with plastic foil in the
winding.
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14. TRANSFORMER
• Gas insulated transformers, using incombustible SF6 gas as a insulation and
cooling medium, enable to remove a fire fighting equipment from
transformer room.
• Since gas insulated transformer does not need the conservator, the height of
transformer room can be reduced.
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15. CIRCUIT BREAKER
•A circuit breaker is an automatically operated electrical switch designed to
protect an electrical circuit from damage caused by excess current from an overload
or short circuit.
•Circuit breaker is of the single pressure type ,during interruption a
compression piston in the chamber generates the gas pressure required to extinguish
the arc between the contacts.
 Maintenance free up to 2000 times load breaking. Mechanically type tested for
10000 operations.

16. GAS DENSITY MONITOR
•Directly mounted on the enclosure.
•In case of gas leakage a micro-switch is actuated.
• Thresholds for refilling (first stage).
• lock-out alarm(second stage).

17. •ADVANTA GES
•Occupies very less space (1/10th)
compared to ordinary substations.
•Hence, most preferred where area
for substation is small (e.g. Cities)
Most 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.
•DISADVANTAGES
•High cost compared to
conventional outdoor sub-station.
 Care should be taken that no dust
particles enter into the live
compartments which results in flash
overs.
 When fault occurs internally,
diagnosis of the fault and rectifying
this takes very long time .

18. CONCLUSION:
•GIS – necessary for Extra HV & Ultra HV.
•Some important areas to be studied include:
•More conservative design.
•Improved gas handling.
•Achieving & maintaining high levels of availability require – more
integrated approach to quality control by both users and manufacturers

19. REFERENCES:
 www.wileyindia.com
 www.ijareeie.com
www.gegridsolutions.com
 www.electrical4u.com
 www.betaengineering.coms

20. THANK YOU