The document is a thank you letter from an intern acknowledging the training opportunity they received with NHPC LTD. It expresses gratitude to several managers and professionals who provided guidance during the training period. The intern considers the training a valuable career development experience and hopes to apply the new skills and knowledge gained.

1. ACKNOWLEDGMENT
The training opportunity I had with NHPC LTD. was a great chance for learning and
professional development. Therefore, I consider myself as a very lucky individual as I was
provided with an opportunity to be a part of it. I am also grateful for having a chance to meet so
many wonderful people and professionals who led me though this training period.
Bearing in mind previous I am using this opportunity to express my deepest gratitude and special
thanks toMr. Altaf Hussain who in spite of being extraordinarily busy with his duties, took time
out to hear, guide and keep me on the correct path and allowing me to carry out my project at
their esteemed organization and extending during the training.
It is my radiant sentiment to place on record my best regards, deepest sense of gratitude to Mr.
Pingal Kispotta (Sr. Manager),Mr. S.C Behera (Dy. Manager) for his careful and precious
guidance which were extremely valuable for my study both theoretically and practically.
I perceive as this opportunity as a big milestone in my career development. I will strive to use
gained skills and knowledge in the best possible way, and I will continue to work on their
improvement, in order to attain desired career objectives.
Sincerely,
NEERAJ PRASAD
DARJEELING POLYTECHNIC INSTITUTE
3RD YEAR ELECTRICAL ENGINEERING

2. TABLE OF CONTENT
1. Company Profile
2. Introduction to hydroelectric power plant
3. Two main parts of TLDP-3
 Barrage
 Control Room
4. Primary cooling Floor
5. Secondary Cooling Floor
6. Turbine Floor
7. Generator Floor
8. Machine Hall
9. Control Room
10. Transformer Gallery
11. GIS(Gas Insulation Substation)
12. Transmission

3. 13. Conclusion
COMPANY PROFILE
Teesta Low Dam project-3 was entrusted to NHPC on 15 Nov. 2000. It stands at 27.00280,
488.44098 on river Teesta in Darjeeling district of West Bengal located at 42KM from Siliguri
via NH-31. Called the run of the river project as this dam function is only to generate electricity
ad not store water in the reservoir.
Location On river Teesta in Darjeeling dist.
Approach Nearest Rail Head- New Jalpaiguri &
Nearest Airport- Bagdogra
Capacity (4*33)MW or 132 MW
Annual Generation 594.07 MU (90% dependable year)
Project Cost Rs. 768.92 crores
Teesta Low Dam Project-3 was constructed by the infrastructure company “HINDUSTAN
CONSTRUCTION COMPANY LIMITED” and cost 768crores under NHPC. It has a 32.5 m
high, 140 m long concrete barrage and has the capacity to generate 600 MW of power annually.
It comprises of four units of 33 MW each. Unit 1 & 2 got commissioned in January 2013, Unit 3
started commercial operations in April 2013 while Unit 4 in May 2013.

4. The project received the environment ministry nod in July 2003. Due to geological conditions
and contractual problems, NHPC has missed the target of commissioning the power plant within
the 11th plan.
INTRODUCTION TO HYDROELECTRIC POWER PLANT
 IN Hydroelectricpowerplantsthe potential energyof waterstoredata heightisconvertedinto
electrical energy
 The Hydroelectricpowerdependson:-
1. Head of water
2. Discharge of water
 Total powerthatcan be generatedis:-
P=(0.736*W*H*Q*n/75) kW

5.  BasinName
 Hydroelectricbasin
 MDDL for powerhouse
 Water Level Variationbetween
FRL and MDDL of Powerplant(m)
 Annual Designenergy(MU)
 FirmPower(MW)
 No.of Turbines/Units(MW)
 Capacityperturbine (MW)
 Total InstalledCapacity(MW)
Sumof IC of all turbines
 Type of Turbines

 RatedHead (NetRTD) (m)
 SpecificSpeed(MKu)
 Numberof Penstocks
 Lengthof Penstock(m)
 Size of Penstocks
 Designdischarge through
 Brahmaputra
 Brahmaputrabasin
 203m
 5
 594.07

 24.2
 4
 33
 132
 Kaplan
 21.34
 548.2
 4
 45
 7
 173.4
TWO MAIN PARTS OF TLDP-3
1. BARRAGE
 In TLDP-3 140m long Barrage has seen constructed across river Teesta at 27 Miles from
Rambi
 The height of the Barrage is 32.5 m and having 7 gates

6. Barrage
Intake Gate
Arm
Radial Gate
Penstock

7. FISH LADDER GATE
 Capacity  10 MT
 Lifting And Lowering Speed  0.5 M/Max
 Lift of Gate  7.5 M
TRASH SCREEN BULK HEAD GATE
 Capacity  2 MT
 Lifting And Lowering Speed  0.25-0.35 M/Max
 Lift of Gate  7.5 M
There are basically four types of power plants: -
 Pelton turbines - It is impulse turbine which is normally used for more than 250 m of water
head.
 Francis - This is a reaction turbine which is used for head varying between 2.5m to 450m
 Kaplan – It is propeller type of plant with adjustable blades which are used for heads varying
between 1.5 m to 70 m
 Propeller – It is used for head between 1.5 to 30 m
 Tubular – This is used for low and medium height projects. Normally for head less than 15 m
FishLadder
GateStopLog

8. 2. POWER HOUSE
TLDP-3 consists of a underground and surface power house
POWER HOUSE OF TLDP-3 CONSISTS OF:-
 PRIMARY COOLING FLOOR
 SECONDARY COOLING FLOOR
 TURBINE FLOOR
 GENERATOR FLOOR
 MACHINE HALL
 CONTROL ROOM
 TRANSFORMER GALLERY
 GIS(GAS INSULATION SUBSTATION)
How energy is generated in Hydroelectric Power Plant?
A hydroelectric power plant consists of a high dam that is built across a large river to create a
reservoir, and a station where the process of energy conversion to electricity takes place.
The first step in the generation of energy in a hydropower plant is the collection of run-off of
seasonal rain and snow in lakes, streams and rivers, during the hydrological cycle. The run-off
flows to dams downstream. The water falls through a dam, into the hydropower plant and turns a
large wheel called a turbine. The turbine converts the energy of falling water into mechanical
energy to drive the generator After this process has taken place electricity is transferred to the
communities through transmission lines and the water is released back into the lakes, streams or
rivers. This is entirely not harmful, because no pollutants are added to the water while it flows
through the hydropower plant.

9. PRIMARY COOLING FLOOR
 Located at an elevation of 176.5 M
 It is open circulating System
 The primary cooling floor is associated with the cooling of generator coolant. This floor
employs motors which brings in raw water and pumps it to the secondary cooling floor
where the generator coolant is cooled through heat exchangers
 The pumps shall be centrifugal type directly driven by 3 phase 415v AC squirrel cage
induction motor. The pump motor shall be mounted on common base plate. The impeller
of pumps will be made in stainless steel, pump casing in steel casting and shaft in
stainless steel. The discharge capacity of each pump shall meet the total requirement of
cooling water of one unit.
 It is open loop system
 TOTAL NO OF PUMP IS 6
1. 4 SEPARATE PUMP FOR 4 DIFFERENT UNIT
2. 2 COMMON PUMP in case of any motor failure
 RATING OF THE MOTOR  55KW(75HP)
 NO OF DUPLEX STRAINER  6
 SPEED OF THE MOTOR  1475
 EFF  93 F
 AMB  51
 LENGTH OF RAW WATER
HEADER
 76.5M
 LENGTH OF DELIVERY WATER
HEADER
 70 M
 WHEN WE NEED MAINTANCE OF FILTER WITHOUT OPENING IT THEN WE
USE MOTORIZING WHICH IS CONNECTED TO VALVE
 WE GIVE SUPPLY WATER THROUGH DRILL LINE
 FLOW METER :- 600 1/MIN
 FLOW METER IS USING TO CHECK WHETHER THE WATER IS FLOWING OR
NOT
 3KG OR 4 KG PRESSURE OF WATER IN PRIMARY

10. AUXILARY SWITCH RATING
  AC  DC
 230V  10A  0.25A
 125V  10A  0.5A
 THERE ARE 2 FILTER IS GIVEN
 FIRST WATER IS FLOSHING TO TAKE WATER FROM RIVER THEN WATER IS
FED TO FILTER WHATEVER DUST PARTICLE IS IN WATER ALL JUST
FILTERISED BY FILTER THEN WATER IS FED TO MOTOR. AFTER MOTOR IT
SUPPIES WATER TO SECONDARY COOLING SYSTEM.

MOTOR FILTER FLOW METER
DRILL
LINE

11. SECONDARY COOLING SYSTEM
 It is closed circulating system.
 The floor is located at an elevation of 180.25 m
 Due to the presence of large no of conductors and high currents flowing through
windings, a large amount of heat is generating. So cooling of generators is very
important.
 The secondary cooling floor generally involves the cooling of the generator. In TLDP-3
the generators are cooled by water in a closed pipe. This water is further cooled
continuously at the primary cooling floor. From here the cold water is pumped to the
various parts of the plant.
 The secondary cooling floor employs the following components:
Two 3ph 415v AC motors
Heat exchanger
Differential pressure switch
 Motors:
The motors usedinthe floorare simplyusedforpumpingwaterinorout.One motor bringsin
the raw waterand anothermotor pumpsoutthe usedraw water
 SPECIFICATION OF SECONDARY COOLING MOTORS ARE:
 NO OF PUMP MOTOR SET  8
 RATING OF MOTOR  45KW(60HP)
 NO OF SIMPLEX STRAINER  4
 NO OF CYCLONE SEPERATOR  1
 NO OF HEAT EXCHANGER  5
 VOLTAGE  415V
 CURRENT  80 A
 SPEED  1475
 EFF  93%
 AMBIENT TEMPERATURE  50 C
 IP  55
 CONNECTION DIAGRAM  302
 HEAT EXCHANGER:
The heat exchangerisusedforcoolingthe generatorcoolantusingthe raw water.Pressure and
temperature metersare attachedtothe inletand outletpipesof the exchangerswithmeasure
the temperature andpressure of the inletandoutletwater.

12. THE SPECIFICATION OFAIRTOWATER HEAT EXCHANGERS:
 HEAT LOAD  39KW
 VOLUME OFAIR CIRCULATED  1.7M3/S
 VOLUME OFWATER CIRCULATED  112 LPM
 WEIGHT  375KG
DIFFERENTILAL PRESSURE SWITCH:
The differential pressure switch is used check the functioning of the heat exchanger
It uses the pressure reading of the meters to determine whether the heat exchanger is
working properly or not.
If the inlet and outlet pressures are different that means the heat exchanger is working
properly and if there is no pressure difference it indicates some clogging within the heat
exchanger. Then the exchanger is cleaned.
THE SPECIFICATION OF THE DIFFERNTIAL PRESSURE SWITCH IS:
 ELECTRICAL RATING  15A , 250VA
 RANGE  0.4-4 KG/CM3
 DEAD BAND  0.5KG/CM2
 PROOF  140KG/CM2
 MATERIAL  TEFLON
 SV.PR.  33KG/CM2

13. TURBINE FLOOR
 THIS FLOOR IS LOCATED AT AN ELEVATION OF 184.5 M
 THE TURBINE EMPLOYED AT TLDP-3 IS KAPLAN TURBINE (VERTICAL
CONFIGURATION)
 The turbine floor includes the turbine, the runner blades and various other components.
 No of guide vane :- 24
Guide vane
Outer head
cover
Regulating ring
Liver
Inner head cover
Overspeed
dripping
device
Bearing
For Cooling
Additional Cooling
Cooling
Pump
Hydraulic
Leaking
Device
Turbine Shaft
Lowerguide
bearing
Oil leakage Unit

14. The Kaplan Turbine is a propeller type water turbine which is adjustable blades. It is combined
automatically adjusted propeller blades with automatically adjusted wicket gates to achieve
efficiency over a wide range of flow and water level.
The Kaplan turbine was an evolution of the Francis turbine. Its invention allowed efficient power
production in low head application that was not possible with Francis turbines.
The head ranges from 10-70 metre and the output from to 120 mw
Runner diameters are between 2 and 8 meters.
The range of the turbine is from 79 to 429 rpm.
SERVO MOTOR
OIL LEAKAGE UNIT
When servomotor start some leakage came out then oil is transferred to the oil leakage unit, then
if the leakage unit is full then oil float switch sense give back to the OPU system.
BRAKING AND LIFTING PLANT:
Braking: - Air System
Lifting: - Rotor Lifting
This plant is associated with the braking of the alternator and also lifting the alternator with help
of oil pressure.

15. The weight of our alternator is 350 tons, so it would be difficult to move such an alternator using
water pressure. So the entire alternator along with the shaft is lifted so that the water through the
gates could easily move the turbine which is connected with the alternator.
OIL AIR
 CAPACITY  1.5 LPM  1500 LPM
 WORK PRESSURE  240 BAR  7 BAR
 TEST PRESSURE  320 BAR  11 BAR
HIGH PRESSURE OIL PLANT
 It is used for both AC and DC
 When the system is off then the runner, turbine settle down to the thresh bearing.
 When we have to start then oil is filled in the thresh bearing through a hole and then
slowly it lubricate and start the machine.
 If the pressure is not high then we can use DC thresh bearing.
 At a time only one is operated
 HPOS is used to create an oil film in between thrust pad and thrust collar
 Rotor is rotating on this oil film
 CAPACITY  14.2 LPM
 WORKING PR.  300 BAR
 TEST PR.  350 BAR
OIL
AIR

16. OIL VAPOUR EXCITATION UNIT
 CAPACITY  250 M3/Hr
 MAXIMUM OP. PR.  200 MM
HEAT EXCHANGER
A heat exchanger is a device that allows heat from a fluid (a liquid or a gas) to pass to a second
fluid (another liquid or gas) without the two fluids having to mix together or come into direct
contact.
For cooling purpose oil is used. First oil comes from generator which is hot so by using water
pressure unit we cool the oil and exchange of that heat water goes out of the system.
 PLATE PACK LENGTH  376 MM
 TEST PRESSURE  6 KG/M2
 OPERATING PRESSURE  9 KG/M2
 OPERATING TEMP.  90 C
 CAPACITY  394 LPM
Thresh Bearing
for AC
Thresh Bearing
for DC

17. M. VALVE
HP AND LP COMPRESSOR
Working pressure:-
HP compressor: - 62-64 Bar
LP compressor: - 7-8 Bar
COOLER
FILTER

18. Role of HP compressor: -
 Provides air pressure to oil pressure unit(OPU)
 Air is provided to LP compressor from HP compressor
Role of LP compressor:-
 Provides air for service
 Provides pressure to the maintenance seal.
 For braking pressure.
EXCITATION TRANSFORMER:
Excitation transformer is nothing but the source or minimum energy given to generator to
generate voltage.
We know that the principle of generator is to convert mechanical energy into electrical energy.
For this conversation it needs magnetic flux lines which get cut by generator coil and produce
EMF. To produce this magnetic flux excitation transformer is used.
The secondary is rotating, which is connected to a rectifier bridge comprising of SCRs (thyristor)
and freewheeling diodes which regulate the delivered current. In excitation with the brush, the
whole arrangement is separate and the dc output is fed through brush to the rotor circuit for DC
field
LP
compressor
HP compressor

19.  KVA  415
 VOLT AT HV  11000
 NO LOAD AT LV  225
 CURRENT HV  21.7
 CURRENTLV  1064.92
 VECTOR GROUP  Dy5
 HIGHEST SYSTEM VOLTAGE  12KV
 MAX. AMBIENT TEMP.  50 DEG.
 MAX. TEMP. RISE  20 DEG
 IMPEDANCE VOLTAGE  5.44
 CORE AND WINDING  1900 KG
 TOTAL WEIGHT  2500 KG
UNIT AUXILARY TRANSFORMERS (UAT):-
The unit auxiliary transformer is the power transformer that provide to the auxiliary equipment
of a power generating station during its normal operation. This transformer is connected directly
to the generator out-put by a tap-off of the isolated phase bus duct and thus becomes cheapest
source of power to the generating station.

20. It is generally a three-winding transformer i.e. one primary and two separate secondary windings.
Primary winding of UAT is equal to the main generator voltage rating. The secondary windings
can have same or different voltages i.e. generally 11kv and or 6.9kv per plant layout.
 KVA  500
 VOLT AT HV  10000V
 NO LOAD AT LV  415V
 CURRENT HV  26.24 A
 CURRENT LV  695.6
 VECTOR GROUP  DYN11
 MAX. AMBIENT TEMP.  50 DEG.
 MAX TEMP. RISE  90 DEG.
 IMPEDANCE VOLTAGE  3.95%
 CORE AND WINDING  1500 KG
 TOTAL WEIGTH  2250 KG

21. LAVT (LIGHTNING ARRESTER VOLTAGE TRANSFORMER):-
LAVT cubicles are enclosure for housing
1. Lightning arrester(LA)
2. Surge capacitor (SC)
3. voltage transformer (VT)
1. To protect the generator from high voltage surge due to lightning stroke or electrical fault. LA
& SC provide minimum resistance path to the short duration high voltage & high current because
of lightning of fault and the complete current flows to ground earth point through the earthed bus
bar
2. for measurement of voltage of a generating unit with the help of VT (a) For measurement of
power (B) protection circuit (C) synchronization of the unit
VT of various accuracies step down the generator voltage of 6.6 KV to 15.7 KV to 110 Volt for
the purpose of metering, protection and synchronizing purpose.
The design of LAVT cubicle depends on:-
1. voltage level of the generator
2. Type of bus duct system between generator and step up transformer of the power plant.
NEUTRAL GROUNDING CUBICE (NGC): -
NGC is an enclosure for installation of neutral grounding transformer (NGT) and Neutral
grounding Resistance (NGR) for grounding /earthing of neutral current during unbalanced three
phase load of a generator. This is essentially required for protection of the generator.
The neutral grounding transformer (NGT) steps down the voltage of neutral bus from 6.
KV/11KV/15.75 KV level to 110 volt or 220 volt level. this stepped down voltage is connected
to a neutral grounding resistance and a ground earth terminal for bringing the voltage level
ofneutral bus a close as possible to zero voltage level.

22. GENERATOR FLOOR
This floor is located at an elevation of 187.25m. An alternator is an electromechanical device
that converts mechanical energy to electrical energy in the form of alternating current.
Most alternators use a rotating magnetic field with a stationary armature but occasionally, a
rotating armature is used with a stationary magnetic field, or a linear alternator is used.
In principle any AC electrical generator can be called an alternator, but usually the term refers to
small rotating machines driven by automotive and other internal combustion engines. An
alternator that uses a permanent magnet for its magnetic field is called a magneto.
From excitation it produces AC then it converts AC to DC then it fed to the rotor , the cooling
water goes inside the rotor , rotor rotates then hot water goes out with outlet pressure
RTD: - Resistance temperature detector
DTTD:- Dial type thermometer detector
If we need to stop of generator for maintenance then first we have to give pressure for braking
so if we get minimum speed then slowly we apply brakes and finally stop.
GENERATOR SPECIFICATION
 INSULATION CLASS  F
 TEMPERATURE RISE  BP
 RATED SPEED  136.36 RPM
 RATED FREQUENCY  50 HZ
 PERMISSIBLE OVERSPEED  377 RPM
 MAX. AMBIENT AIR
TEMPERATURE
 40 C
 MAX. WATER COOLANT
TEMPERATUER
 30 C
 TOTAL MASS  346000 KG
 DEGREE OF PROTECTION  IP54
 TYPE OF CONSTRUCTION  IM8205(W8)
 CONNECTION  STAR,2 FOLD PARALLEL
 DUTY TYPE  S1
 RATED OUTPUT  36670 KVA
 RATED VOLTAGE  11000+_10%V
 RATED CURRENT  1924.7 A
 RATED POWER FACTOR  0.9
 RATED FIELD VOLTAGE  118

23. MACHINE HALL
This floor is located at an elevation of 190.5m. The machine hall consists of the OPU set,
rectifiers, unit heads and simulation display screens.
OPU SET: -
It stands for oil pumping unit. The oil pumping unit set is used to pump oil to move the runner
blades. The entire set consists of an accumulator and two motors. The oil is pumped through two
big pipes which run from the unit head to the runner blades through the hollow shaft.
The main components of oil pressure system: -
 Accumulator tank containing required volume of oil under compressed air.
 Oil pumping unit maintaining effective volume and pressure in accumulation tank.
 Controls of the oil pressure unit.
The oil pressure systems are rated from 4Mpa and 6.3Mpa pressure.
There are 4 oil pressure machine each having 33 MW power.
Guide vane: - Control the water pressure insert into the turbine.
Oil pressure is maintained to 60 kg/m2
Governor: - It varies the water flow through the turbine to control the speed or power output.
Generating units sped and system frequency may be adjusted by the governer.
There is 1/3rd hydraulic oil and 2/3rd is air.
Used to control the runner blades and guide van.
The specification of OPU set:-
 CHANGEOVER SWITCH  315A
 VOLTS  415V
 CURRENT  320A
 INCOMR -1 SUPPLY FROM UAB 2  320 A
 INCOMER-2 SUPPLY FROM UAB1  320 A
 OPU PUMP-1  110 KW
 OPU PUMP-2  110 KW
 OIL LEAKAGE PUMP GUIDE VANE  1.1 KW
 OFFLINE FILTRAION PLANT  75 KW

24. ACCUMULATOR TANK: -
An accumulator tank is a water chamber which has a pressurized internal air bladder. They are
designed to be installed downstream of your pump and dampen water pressure spikes, reduce
pump cycling, help increase the pumps life and battery power.

25. WHY WE USE FIELD BREAKER?
Field breaker is used to isolate / change the field excitation supply to the main excitation
irrespective to the power plant.
It is also connected with discharge resistor for discharging the field winding while de-excitation
of the generator set.
EXCITATION EQUIPMENT
 Static
 36.67 MVA/1KV/1924.6 A /50 HZ/0.9cos()
Rotor
 Voltage: - 118 v
 Current: - 899 A
 Resistance :- 0.133
 75 C
 AVR type :- Thyne 5
 Channel : - 2
 Bridge :- 2
 Configuration :- n:1
 DC supply : - 220V
 AC supply :- 415 V
CONTROL ROOM
 The elevation of control room is 190.5 M
 The whole plant is controlled through SCADA (Supervisory Control And Data
Acquisition)
 In TLDP-3 there are two server namely server A & server B
 Control room has two more room, they like:-
1. Battery Room
2. LTAC Room

26. TRANSFORMER GALLEY
A Transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductors the transformers coils. A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic
field through these secondary winding. This varying magnetic field induces a varying
electromagnetic force(EMF), in the secondary winding. This effect is inductive coupling.
TRANSFORMER OIL PUMP
 HP  4.3
 SIZE  100*100
 DISCHARGE  1100
 LPM. AMPS.  7
 INSULATION CLASS  F
 HEAD  11
 RPM  2850
 WINDING CONNECTION  DELTA
o KVA (HV)  41000
 KVA (LV)  41000
 VOLT AT NO LOAD HV  220000
 VOLT AT NO LOAD LV  11000
 AMPERE HV  108
 AMPERE LV  2152
 NO OF PHASES  3
 FREQUENCY  50HZ
 DIAGRAM DRG. NO.  TK106832
 TYPE OF COOLING  OFAF
 IMPEDANCE VOLTAGE  12.14%
 CONNECTION SYMBOL  YND11
 MASS OF CORE AND WINDING  50000 KG
 MASS OF OIL  22500 KG
 TOTAL MASS  87000 KG
 MASS OF HEAVIEST PKG.  57500 KG
 UNTANKING MASS  50000 KG
 UNTANKING HEIGHT  7660 KG
 VOLUME OF OIL  25000 L
 AIR CIRCULATION  677 M3/MIN
 OIL CIRCULATYION  1000L/MIN
 MAXIMUM TEMP RISE OF OIL  50 C

27.  Bucholz Relay: - It is for internal fault oil vaporises to gas then by force of gas it supply
next
 Centre tap changer: -If the voltage is coming less then we have to fix the voltage by 220v
 In main conservator Silica Gel is used
 RXCT: - Temp. Range : - 30-150 c
Bucholz
Relay
Cable
Box
Conservator
Cooler
Control Box
CenteredTap
Changer
Cable

28. CONNECTION DIAGRAM
OFAF READING
 Design pressure  35 kg/cm2
 Test pressure  5
 Heat Dissipation  200 kw
 Weight  1800 kg

29. SST
It stands for station service transformer. These are fed through the incomers from external
sources. These transformers are utilized in the absence of self generation.

30. GAS INSULATION SUBSTATION
A gas insulated substation is an electrical substation in which the major structures are contained
in a sealed environment with sulphur hexafluoride gas as the insulating medium.
The main application for gas insulated substation today is:
High voltage installation (usually 115 kV and above although some manufactures offer
equipment with voltage ratings down to 20 KV). The higher the voltage, the more favourable gas
insulated technology becomes. The footprint of 764 KV conventional substations is enormous
and GIS technology allows a significant size reduction.
Urban installation, usually but not always, GIS technology is used for installation in areas where
the cost of real estate is a significant consideration.
Indoor installation: - It is generally not practical to build an air insulated substation inside a
building, but GIS can easily go inside buildings.
In most cases, the circuit breakers in gas insulated substation employ SF6 as the interrupting
medium as well as the insulating medium, but there is hybrid installation in which breakers use
vacuum interruption. The gas pressure required for SF6 to serve as an interruption medium is
much greater than the pressure required for it to be insulation medium.
CircuitBreaker
Isolators

31. Circuit Breaker
 It is automatically operated electrical switch design to protect an electric circuit from
damaged caused by over current or overload or short-circuit
Isolators
 Isolators is manually operated mechanical switch that isolates the faulty section or repair
from a healthy section in order to avoid occurrence of more severe fault.
Extension Valve
 For increasing temp, the valve will short and for normal temp. valve will become normal.
Why we use GIS?
 For cooling the bus bar
 Like if here generate 220 kV then at least 2m distance has to be done the effect will not
come. So the gap between the bus bar and pipe should be 180 mm
 If we don’t give sf6 gas then the system will burst out
Unit
Extensionvalve
3
Phases

32. VOLTAGE TRANSFORMER
Rated insulation level: - 245/460/1050 kV
HZ: - 50
Rated voltage factor: - 1, 9/30s
Total therm. Burden: - 1200 VA
Nominal/minimum pressure at 20 C = 0.65/0.58 Mpa
Mass: - 210 kg
CURRENT TRANSFORMER
Idyn: -125 KA
HZ: - 50
Insulation level: - 245/460/1050 KV
Ith =50/1 KA/s
 Whatever machine is not working or supply to customers N2 gas is given so that the parts
will not damage due to moisture in parts, we supply N2 gas before supply to the supplier.
 In running condition, a metal name Aluminia is fitted inside so that Aluminia trap the
moisture inside the running machines not give to the sf6 gas Captures and not mix with
SF6 gas. If he moisture becomes high so that moisture have to taken out while
maintenance.
 In1 unit there are 3 earthing switch, 3 isolators, 3 High speed Earthing Switch
HIGH SPEED EARTHING SWITCH
 Ur  235 KV
 Up  1050KV
 Lk/tk  50KA, 1S
 Pre  0.65 Mpa
 Er  E1

33. ISOLATOR
 Ur  245 Kv
 Up  1050 Kv
 Lr  400A
 Lk/tk  50KA, 1S
 Pre  0.65Mpa
EARTHING SWITCH
 Ur  245Kv
 Up  1050Kv
 Lr/tk  50KA, 1S
 Pre  0.65 Mpa
CIRCUIT BREAKER
 Ur  245 kV
 Up  1050 Kv
 Ir  4000 A
 Tk  1S
 Isc  50A
 Kpp  1.5
 Il  125 A
 Pre  0.7 Mpa
 Uop  220 Kv
 Us AC  220Kv
 Us DC  240 Kv
 M  2100 kg
 m  51kg

34. TRANSMISSION
The power generated at generating station is in low voltage level as low voltage power
generation has some economical values. Low voltage power generation is more economical than
high voltage power generation. At low voltage level, both weight and wide of insulation is less in
the alternator, this directly reduces the cost and side of alternator. But this low voltage level
power cannot be transmitted directly to the consumer end as because this low voltage power
transmission is not at all economical. Hence although low voltage power generation is
economical but low voltage electrical power transmission is not economical. Electrical power is
directly proportional to the product of electrical current and voltage of system. So for
transmitting certain electrical power from one place to another, if the voltage of the power is
increased then associated electric current of this power is reduced. Reduced current means less
I2R loss in the system, less cross sectional area of the conductor means less capital involvement
ad decreased current cause’s improvement in voltage regulation of the system and improved
voltage regulation indicates quality power. Because of these three reasons electrical power
mainly transmitted at high voltage level.
Lightning
Arrester
Wave trap
CVT (Capacitor
Voltage
Transformer)
Bushing

35. Lightning Arrester: -
A lightning arrester is a device used on systems to protect the insulation and conductors of the
system from the damaging effects of lightning. The typical lightning arrester has a high voltage
terminal and a ground terminal. When a lightning surge(or switching surge, which is very
similar) travels along the power line to the arrester, the current from the surge is diverted through
the arrester, in most cases to earth.
Wave Trap: -
A wave trap (high frequency stopper) is a maintenance free parallel resonant circuit, mounted
inline or high voltage AC transmission power lines to prevent the transmission of high
frequency(40 KHz to 1000KHz) carrier signals of power line communication to unwanted
destinations.
CVT (Capacitor Voltage Transformer): -
CVT is a transformer used in power systems to step down extra high voltage signals and provide
a low voltage signal, for metering or operating a protective relay.

36. PROTECTION SCHEME
PROTECTION FAULT
Internal faults are those which occur within the circuit due so some special causes like short
circuit, overheating, etc. to protect the circuit with these fault a typical circuitry of relay and
metering devices is used. The various relays used here are:
Generator protection:
(1) Overvoltage type relays
(2) Overall differential relay
(3) Back impedance relay
(4) Negative phase sequence relay
(5) Loss of excitation
(6) Pole slipping relay
(7) Under voltage relay
(8) Auxiliary relay
(9) Earth fault relay
Line protection:
(1) Distance relay
(2) Overvoltage relay
(3) Definite earth fault relay
(4) Carrier aided relay
(5) Power swing protection
(6) Auto enclosure relay
(7) Over current relay

37. CONCLUSION
I would like to say that this training is an excellent opportunity for me.
The main objectives of this industrial training are to observe and practice how the basic machine
knowledge and Engineering is applicable in the real industries.
It is not only to get technical experience but also to observe management practice and how to
interact with fellow workers.