The document summarizes a seminar presentation on gas insulated substations (GIS). It defines GIS as substations that use sulfur hexafluoride gas (SF6) as an insulating medium to allow for a compact design. The document outlines the key internal equipment of GIS, including circuit breakers, disconnectors, buses, transformers, and more. It discusses the advantages of GIS such as reduced space requirements and reliability. GIS are well-suited for applications requiring a small footprint, such as urban or indoor installations.

1. SEMINAR PRESENTATION TOPIC:
GAS INSULATED SUBSTATIONS
SESSION:2014-2015
PRESENTED BY:
NAME:MOHAMMAD SAIF
BRANCH:ELECTRICAL AND ELECTRONICS ENGG.
1

2. Contents
 Introduction of GIS
 Gas Insulated Substation
 Internal equipments of GIS.
 Definitions of equipments.
 Internal equipments of GIS.
 Need of GIS
 Service condition of GIS
 Services offered by GIS to supplier.
 Drawback of GIS.
 Advantages of GIS.
 Application of GIS .
 Conclusion.
 References

3. Introduction to GIS
 GIS was first developed in various countries between 1968
and 1972.
 After about 5 years of experience, the use rate increased to
about 20% of new substations in countries where space is
limited.
 Conventional substations requires, small installations size,
protection against atmosphere pollution and moisture,
noiseless operation, on explosive and flame resistant,
reduced maintenance, minimal radio interference, but totally
enclosed substations using SF6 gas as insulation that are
also known as GIS which is stand for GAS INSULATED
SUBSTATIONS.
 GIS is now in widespread use in the electrical power industry.

5. GAS INSULATED SUBSTATIONS
Definition:
 A gas insulated substation(GIS) is a substation that uses a
superior dielectric gas, sulfur hexafluoride (SF6),high voltage.
 The basic principle of GIS 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 SF6 gas under moderate pressure.

6. GAS INSULATED SUBSTATIONS
 Components:
 1- Circuit breaker.
 2-Disconnector(Isolator).
 3-Ground switches.
 4-Bus-bar.
 5-Transformer.
 8-Outgoing bus-bar for electrically
connecting the gas insulated substation
with bus-bar.
 9-Outgoing portion of the transformer
being arranged in accordance with
extending direction of outgoing bus-bar.

8. INTERNAL EQUIPMENTS OF GIS

10. Definition's of equipment's
BUS-BAR:
 An electrical conductor that carries a large current,
especially one that is part of a power distribution
system; typically a thick strip, or a tube, of copper or
aluminum.
CIRCUIT BREAKER:
 Under short circuit conditions,however,the current
may reach tens of thousands of amperes at a power
factor as low as 0.1.
 It is duty of a circuit breaker to interrupt such currents
as soon as possible to avoid equipment damage.

11. CURRENT TRANSFORMER:
In the single phase enclosed core of CT is
located outside the enclosure inside for three
phase.
Gas compartment to reduce access of
moisture and to suppress gas-tight bushing for
secondary connections.
CT current rating is 120% of rated primary
current.

12. VOLTAGE TRANSFORMER:
Variable location on feeder and busbars.
Integrated disconnecting facility for GIS and
power cable testing without dismantling and
gas handling.
DISCONNECTOR:
Disconnectors or isolators are used for
electrical isolation of circuit parts.
Disconnect switches can be three pole,group-
operated,or single pole operated.
They are slow acting and operating at off load.

13. EARTHING SWITCH:
Slow operating earthing switch are used for
protection purpose.
 When work is being done in the substation,
but are operated only when it is certain that
the high-voltage system is not energized.
The fast closing earthing switch can close
against full voltage and short circuit power.
The high speed earthing switch is achieved by
means of a spring-closing device.

14. CABLES COMPARTMENT:
 Optimized solution for plug-in type power cable
connection.
 Adjustable support structure for minimum
requirements for the GIS floor.
 Fixation to the GIS floor by cemented anchor
bolts, no need for special foundation (steel
beams….etc.)

15. LOCAL CONTROL CUBICLE:
 LCC is the interface cubicles to all secondary system of a substation which
are represent a station control and protection.
 LCC includes control and alarm functions as well as the correct distribution
of auxiliary power supply for the relevant GIS .
 In general, each cabinet should contain the following equipment for
control, indication and protection of switches, circuit breaker, and
associated components:
 1. One control switch for each three phase circuit breaker.
 2. One remote local switch for each three phase circuit breaker.
 3. One open close control switch for each motor operated grounding switch.
 4. One or two red light-emitting diodes and one green for each circuit breaker, each
disconnect and grounding switch, or contact position indication .
 5. Control switches for ac and dc supply to each compartment.

16. Need for GIS
 Non availability of sufficient space.
 Reduction in length of feeders.
 Improvement of the quality of voltage regulation due to short length feeder.
 Total space required for GIS is 10% of the needed for a conventional substation.
 GIS technology can be used for installations in areas where the cost of real estates
is appreciable.
 Overcome or decrease the magnitude of limitation of AIS site selection.

17. Service condition of 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 as per IEC 62271
 Maximum ambient temperature : 105 degree Celsius as per IEC 62271
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.

18. Service offered by GIS user and GIS
supplier
Unless otherwise specified or agreed upon,the user should receive,install,and
field test the apparatus specified herein,installation and field testing of the
GIS should be completed under the supervision of the supplier to ensure
correct installation.Unless otherwise specified,the following equipment and
services should also be furnished by the user:
 Concrete foundation.
 Power transformer or reactor including bushings.
 Surge arrester,outsidee the GIS
 The station ground grid,below ground,and vertical connection risers of
adequate length.
 Ac and dc auxilary power to furnished equipment.

19. Drawbacks of GIS substation
 High cost.
 Waves get reflected and refracted.
 Excessive damage incase of internal faults.
 Diagnosis of internal takes very long time.
 SF6 gas pressure must be monitered in each compartment.
 SF6 cause ozone layer depletion and global warming.

20. Advantages of GIS
Occupies very less space.
Most reliable.
Number of outages due to the fault is less.
Maintenance free.

21. Applications of GIS
High voltage installations
The higher the voltage, the more favorable gas insulated technology becomes. The
footprint of 765kV conventional substation is enormous, and GIS technology allows a
significant size reduction.
Urban Installations
GIS technology can be used for installations in areas where the cost of real estate or aesthetic
appeal is a significant consideration.
Indoor Installations
Building an air insulated substation indoors is usually impractical, but a GIS can easily go inside
buildings.
Environmentally Sensitive Installations
GIS technology is popular in desert and arctic areas because it can be enclosed in a building with
environmental control.

22. Conclusion
GIS generate no noise and have no idea no
radio interference.
GIS is necessary for extra HV and Ultra HV
substations.
More conservative.

23. Reference
• www.google.com/gasinsulatedsubstation
• www.yahoo.com/gasinsulatedsubstation
• www.slideshare.com/gasinsulatedsubstation

24. Thanking you