1. STUDY & DESIGN OF 66/33/25KV
GIS SUBSTATION
DMRC NEW DELHI
PROJECT REPORT
BACHELOR OF ENGINEERING
IN
ELECTRICAL ENGINEERING
UNDER THE SUPERVISION OF
SHEERAZ KIRMANI
ASST. PROFFESOR
FACULTY OF ENGG.&TECHNOLOGY
JAMIA MILLIA ISLAMIA PRESENTED BY
NEW DELHI-110025 DEEPAK KUMAR(11BE108)
GANESH KUMAR (11BE116)

2. INTRODUCTION
GAS INSULATED SUBSTATIONS
• GAS INSULATED USES SULFUR HEXAFLUORIDE (SF6)
• WHICH HAS A SUPERIOR DIELECTRIC PROPERTIES USED AT
MODERATE PRESSURE.
• IN GAS INSULATED SUBSTATION THE HIGH VOLTAGE
CONDUCTORS, CIRCUIT BREAKER
INTERRUPTERS,SWITCHES,CURRENT TRANSFORMER ,VOLTAGE
TRANFORMER AND LIGHTINING ARRESTERS ARE
ENCAPSULATED IN SF6 GAS INSIDE GROUNDED METAL
ENCLOSURES.
• THE GAS INSULATED SUBSTATION IS PREFERRED FOR
LOCATIONS SUCH AS LARGE CITIES AND TOWNS,
• UNDER GROUND STATIONS,AND MOUNTAINS AND VALLEY
REGIONS

3. It consist of
• Bus Bars
• Circuit Breakers
• Disconnecting Switches
• Earthing Switches
• Current Transformers
• Voltage Transformers
• Cable and Boxes
• Gas Supply and Gas Monitoring Equipment
• Local Control

4. 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.

5. Disconnectors
•Disconnectors or isolators
are used for electrical
isolation of circuit parts
•They are slow acting and
operating at off load
•Disconnectors must be
carefully designed and tested
to be able to break small
charging current without
generating too-high over
voltage,

6. Earthing Switch
Earthing switch is used to earth the
live parts during maintenance and
during testing.
During maintenance although
circuit is open still there are some
voltages on line , due to
which capacitance between line
and earth is charged.
Before proceeding to maintenance
work the voltage is discharged to
earth, by closing the earth switch.

7. Voltage Transformer
Voltage transformer is connected to
switchgear with the connecting flanges
with a barrier insulator.
 primary winding is insulated with
SF6 gas & connected to high voltage
terminal.
The primary winding is wounded
on the top of the core & secondary
windings.
secondary winding is connected to the
terminals in the external terminal box
through a gas tight multiple bushing.

8. 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 bushings for
secondary connections.

9. Cables Compartment
1. Optimized solution for
plug-in type power
cable connection.
2. Adjustable support
structures for minimum
requirements for the
GIS floor.
3. Fixation to the GIS
floor by cemented
anchor bolts, no need
for special foundation
(steel beams….etc)

10. TECHNICAL SPECIFICATION
ENCLOSURE TYPE : THREE PHASE ENCLOSURE
RATED VOLTAGE : 72.5 KV RMS
RATED FREQUENCY : 50HZ
RATED CURRENT OF 2500 A RMS
BUS BAR
RATED SHORT TIME : 40 KA RMS,3 SEC
CURRENT
GUARANTED SF6 GAS : LESS THAN 1%
LOSSES PER YEAR

11. SINGLE LINE DIAGRAM OF 66/33/25 KV GIS SUBSTATION

12. AUXILIARY MAIN TRANSFORMER(66/33
KV,30/45 MVA)
DESCRIP
TION
UNIT ONAN ONAF
RATING MVA 30 45
RATED
PRIMARY
VOLTAGE
KV 66 66
RATED
SECONDARY
VOLTAGE
KV 33 33
RATED
PRIMARY
CURRENT AT
66 KV
A 262.43 393.65
RATED
SECONDARY
CURRENT AT
33 KV
A 524.86 787.30

13. TRACTION TRANSFORMER(66/25 KV,40/50 MVA)
DESCRIPTION UNIT ONAN ONAF
RATING MVA 40 50
RATED PRIMARY VOLTAGE KV 66 66
RATED SECONDARY VOLTAGE KV 25 25
RATED PRIMARY CURRENT
AT 66 KV
A 606.06 757.58
RATED SECONDARY CURRENT
AT 33 KV
A 1600.00 2000.00

14. 66 KV LINE CKT BREAKER
DESCRIPTION UNIT CALCULATED SELECTED
RATED VOLTAGE KV 66 66
RATED PRIMARY
CURRENT AT 66
KV
A 1151.22 2000

15. 66 KV LINE ISOLATOR
DESCRIPTION UNIT CALCULATED SELECTED
RATED
VOLTAGE
KV 66 66
RATED PRIMARY
CURRENT AT 66
KV
A 1151.22 2000

16. PROPERTIES OF SF6
•SF6 does not harm to
the ozone layer.
•Sf6 gas is chemically stable
•Non poisonous
•Colourless & heavier than air
•Almost water insoluble
•Non inflammable

17. Comparison bw Gis & Ais

18. ADVANTAGES
• Main advantage of GIS over AIS is its phase to phase
spacing decreases significantly. This is more effective
in urban environment where land and its size is at a
premium
• Gis have no risks for fire & explosion.
• They generate no noise & have no radio interference
• It offer solutions including
-In industrial areas where space & pollution problems
-Mountain areas where ice & snow are major problems

19. DISADVANTAGES
 GIS installations tend to be much more
expensive that air-insulated installations
with the same rating.
 VFTO during switching operations or earth
faults and transient enclosure voltages
and particle contamination
 The Damage Effect Will Also Be Severe
Whenever Internal Fault occurs.

20. APPLICATIONS
• High voltage installations.
• Urban installations
• Indoor installations

21. FUTURE TRENDS IN GAS INSULATED
SUBSTATIONS
 Compact design of switch gear.
 Use of SF6 circuit breaker cells in the medium
high voltage GIS and fewer brakes per pole in
high voltage circuit breakers
 Optimization of GIS design to allow easier
maintenance

22. CONCLUSION
• GIS are necessary for EHV & UHV
• some important areas to be studied
include.
• more conservative designs.
• improved gas handling .
• Achieving & maintaining high levels of
availability requires a more integrated
approach to quality control by both
users and manufactures