summer industrial report , nathpa jakhri hydro project

1. Rayat Institute of Engineering and Information Technology
Railmajra, INDIA
GENERATION OF ELECTRICITY THROUGH HYDRO
POWER AND MAINTENANCE OF POWER HOUSE
REPORT
SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR
Six Month Industrial Training
at
SJVNL, Jakhri
( 19-01-2016 to 19-04-2016 )
SUBMITTED BY
Yogesh Thakur
Mechanical Engineering
1248936
Mechanical Engineering Department
Page 1 of 35

2. ACKNOWLEDGEMENT
The success of my project depends largely on the encouragement and
guidelines of my project manager. I take this opportunity to express my
gratitude to the people who have been instrumental would in the successful
completion of this project.
I like to show my great appreciation to my project in-charge, Mr Ghyan
Chand . I am very thankful to him for the tremendous and help. I feel
motivated and encouraged every time I support his meeting. Without his
suggestions and guidance this project work would not have been
materialized.
Yogesh Thakur
Page 2 of 35

3. PREFACE
The training at SJVN Limited involved the day to day working at Generation
of electricity at power house and maintenance department. This project
helped me to get the deeper understanding of the process of generation and
maintenance of electricity at power house.
For this study three years data have been taken for trend analysis and ratio
analysis. Main objective in undertaking this project is to supplement
academic knowledge with absolute practical exposure to day to day
functions of the business organization.
Maintenance analysis which is the topic of this project refers to an
assessment of the viability, stability and profitability of a business. This
important analysis is performed usually by finance professionals in order to
prepare financial or annual reports. These reports are made with using the
information taken from data files of the company and it is based on the
significant tool of Trend Analysis. These reports are usually presented to top
management as one of their basis in making crucial business decisions.
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4. DECLARATION
I Yogesh Thakur, student of Rayat Institute of Engineering and Information
Technology , Ropar hereby declare that I have completed the
project on “GENERATION OF ELECTRICITY AND
MAINTENANCE OF POWER HOUSE SJVN LTD and its
comparison With NHPC” in Partial Fulfillment of the
Requirements for the Degree in Mechanical Engineering Session
(2012-2016). The information submitted is true and original to the
best of my knowledge.
Place: Yogesh Thakur
Date:
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5. Contents
Sr.
No.
Title Page No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Introduction to SJVNL
Nathpa Jakhri Project , Salient Features
Other Main Features of Project – Human Resource
Management.
Project Commission Schedule.
Project Advantages.
Project Statistics.
Introduction to Turbine.
Turbine Functions.
Turbine Components.
Introduction to Generator.
Generator Components.
Main Electrical Equipment’s.
Dam.
Selection of Dam Site and its related terms.
Results and Discussions.
Conclusion and Future Scope.
Bibliography and References.
6
7
8
9
10
11-12
13
14
15-19
20
21-23
24-25
26
26-32
33
34
35
Page 5 of 35

6. Introduction to SJVNL
SJVN Ltd (formally Nathpa Jhakri power corporation limited - NJPC) was incorporated
on 24th
may 1988 as a joint venture of Govt. of India and Govt. of Himachal Pradesh
plan investigate , organize , execute , operate and maintain Hydro Electric Power
Project in the Satluj River . Nathpa Jhakri ( 6x 250MW ) is the largest hydro -
electric project in India. A comparison with other comparable projects ( single
power station of 500MW and above ) in India. Total capacity of this project is 1500
MW. It is having 6 units of 250 MW capacity of each. The 1500MW Nathpa Jhakri
Hydro Project is the largest underground hydro project in the country and is the first
project undertaken by SJVNL for execution. Different states to which the balance
power is allocated are Himachal Pradesh , Haryana , Jammu & Kashmir, Punjab,
Rajsthan,Utter Pradesh, Chandigarh and Delhi.
The approved cost of the project is Rs. 7666.31 crores with completion cost of 8058.34
crores. On completion the project is estimated to cot Rs. 9083 crores.
The main components of this project are:
• A 62.5 m high diversion dam on the Satluj River.
• An underground desilting complex.
• A 27.4 km long head race tunnel.
• A 301 m deep surge shaft.
• Steel lined pressure shaft.
• Underground power house and transformer hall.
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7. Nathpa jhakri project - a brief on silent features
 It has a 62.50 m high concrete gravity dam at Nathpa village of Kinnaur district of
Himachal Pradesh and it divert 405 cumecs of water through 4 Nos. power
Intakes
 Underground Desilting chamber 4 Nos. each of 525 m long , 16.31 m wide and
27.50 m deep which is the largest underground complex for desiltation of water in
the World.
 A head race tunnel of 10.15 m dia. And 27.39km long which is the longest power
tunnel in the world and terminates to 21.6m/ 10.2m diameter
 It has the deepest surge shaft which is 301m deep.
 There are three circular steel lined pressure shafts each of 4.9 m dia. And 571 m
to 622 m length which feed six generating units.
 The six generating units with Francis turbine of 250 MW and utilize design
discharge of 405 cumecs and a design head of 428 m.
 The discharge tubes to the collection gallery for discharging the water back into
the river through the 10.15 m dia and 982 m long tail race tunnel.
 The project has an underground Transformer hall and Power house. There is a
Surface Switch Yard for evacuation of power through two no. of transmission
lines.
 The project also has an interesting feature of Sholding Works Complex which
enable diverting the water of Sholding Stream into the HRT.
 Annual energy generation of 6750.85 million units in a 90% (MU) dependable
year.
This project has also provided direct and indirect employment by various national
and international contract agencies working on the project.
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8. Other main features of the project
Human resource development :
The company is having well established strategy for imparting training to the employees
and involves other professional people to motivate the employees for good working. The
training imparted is two dimensional i.e. in house training and through external
professional institutions as well.
SAFETY CONCERN :
SJVN Ltd. abides by its moral responsibility for maintaining a safer environment for all
its employee and also these of its contracting agencies .Due attention is given to health
and safety aspects in working areas. The safety measures adopted encompass the best
codes and practices, which are disseminated to all the employees for ensuringcompliance
at all levels.
FUTURE PROSPECT :
Agreement for the execution for the Rampur Hydro Electrical project between
SJVN L and govt. of Himachal Pradesh was signed on 20th
October 2004 of 439 MW
utilizing the tail race water of ongoing 1500MW Nathpa Jhakri Hydro Electric Project is
a run of the river scheme works for which nave already been commenced by SJVNL
and other project in the state H.P.viz. Khab and Luhari projects and in Uttranchal and
Sikkim shell be taken for execution.
OVER VIEW OF NATHPA JAKHRI HYDRO-ELEECTRIC PROJECT :
The 1500MW, Nathpa Jhakri Hydro-electric power projects (NJHPP) envisages to
harness the hydro power potential in the upper reaches of River Sutlej in the south west
of Himalayas in Himachal Pradesh. The Power house site is about 150 Kms from the
nearest rail head (narrow Gauge), Shimla. THE project stretched over a length of about
50 Kms From the Dam site to the power house, on the Hindustan Tibet road (NH-22).
PROJECT FEATURES :
The project consists of following specific components:
 A 62.5m high concrete Dam on Sutlej river at Nathpa to divert 405 cumecs of
water through four intakes.
 An underground Desilting complex, comprising four chambers, each 525m long,
16.31m wide & 27.5 m deep (one of the largest underground desilting complexes
for Hydro power in the world).
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9.  A 10.15 diameter & 27.395m long head race tunnel (One of the longest hydro
power tunnel in the world), terminating in 21.6/10.2 m diameter & 301m deep
surge shaft.
 Three circular steel-lined pressure shafts, each of 4.9 m diameter & 633 m long
bifurcating near the power house to feed six units.
 An underground power house with a dimension of 222m x 20m x 49m having six
Francis turbines of 250MW each to utilize a design discharge of 405 cumecs &
design head of 425m.
 A 10.15 m diameter & 982m long tail race tunnel to discharge the water back into
the river Sutlej.
UNIQUE FEATURE
Nathpa Jhakri power project has several unique features. The underground desalting
complex would be one of the largest underground complexes in the world to exclude
sediment particles above 0.2 mm so as to prevent these from entering into the head race
tunnel & in turn into the turbines.
The 10.15 diameter & 27.395 Km long head race tunnel will be one of the longest Power
tunnel in the world. Similarly, the 301m deep surge shaft would be one of the deepest
surge shafts in the world. Besides, this would be the largest underground power house in
the country to house six units of 250MW each with an aggregate capacity of 1500MW in
a single underground cavern.
PROJECT COST
The project is estimated to cost RS 7,666.31 crore at June ,1998 price level, which has
been approved by the Cabinet Committee on Economic Affairs (CCEA) in its meeting
held on April 28, 1999.
PROJECT COMISSIONING SCHEDULE
The commissioning schedule of NJHPP was as follows:
Unit Commissioned
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10. Unit-I 18 May ,2004
Unit-II 06 May, 2004
Unit-III 31 March , 2004
Unit-IV 30 March , 2004
Unit-V 06 Oct. , 2003
Unit-VI 02 Jan. , 2004
PROJECT ADVANTAGES
Besides the social & economic upliftment of the people in its vicinity, on commissioning,
the 1500MW NJHPP will generate 6700 MU of electrical energy in a 90% dependable
year. It would also provide 1500MW of valuable peaking power to the northern grid.
Out of the energy at the bus bar, 12% is to be supplied free of cost to the state of H.P.
From the remaining 88% energy generation, 25% is supplied to HP at bus bar rates &
balance to the other state of northern region.
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11. PROJECT STATISTICS
DESCRIPTION AS PER REVISED COST EXTIMATE
Location:
State:
District:
Vicinity
Diversion Dam:
Type
Max. height above foundation
level
Full reservoir level
Max. water level
Min. draw down level
Disilting Arrangement :
Type
Number & size
Flow through velocity
Particle size to be removed
Head Race Tunnel:
Shape & type
Diameter
Surge Shaft:
Type
Diameter
Total height
Pressure Shafts:
Type
Number
Main tunnels
Power House:
Type
Size
Type of turbine
Gross head
Design head
Number and capacity of
generating units
Himachal Pradesh
Kinnaur/Shimla
Dam down stream of wangtoo bridge at Nathpa &
power house near Jhakri village on left bank of river
sutlej.
Concrete gravity
62.5m
1495.50m
1497.50m
1474.00m
Underground
Four parallel chambers each 525m x 16.31m x
27.5m
33.0 cm/sec.
Particle greater than 0.2 mm
Circular, concrete lined
10.15m
Restricted office
21.6m circular for height of about 210.0m & a
connecting shaft of 8.8 m diameter. And about
90.0m high.
301.0m
circular, steel lined with high tensile steel
corresponding to ASTMA517 grade F of thickness
varying from 26mm to 38mm.
3, each bifurcating to feed 2 units
4.9m & approx. 572m to 622m & 623m length.
Underground
222m x 2om x49m
Vertical axis Francis turbine
486m
428m
6 x 250 MW
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12. Tail Race Tunnel:
Size
Length
Power Potential:
Energy generation in a mean year
Energy generation in a
dependable year
10.15m, circular
982m
7447MU
6612 MU in a 90% dependable year
Nathpa Jhakri project has an underground power house with internal dimensions
222 m* 20 m and 29 m high located at 200 m below the natural earth level . The
main access tunnel to the power house is 731.5 m long .The power house has an arched
roof with concrete lining. The main inlet valve has also been provided at an EL.
982.5The power house has four floor . The turbine floor is at an EL. 990 m . The main
auxiliaries in this floor are Governor , Oil cooler , Brake Dust Collector , Oil
Vapour Collector , Secondary water pump and the turbine pit . The turbine is
coupled with Generator with the help of the shaft.The generator floor is at an EL. Of 995
m here we also have Unit Auxiliary Board,Temperature measuring gauges, the
Excitation Transformer for providing the Starting torque to start the generator and the
220 V battery room.They have a Service Bay Floor at an EL.Of 1000.5m from here the
functioning of generating units is controlled with the help of operating system.There is
an underground Transformer Hall at an EL. Of 1044 m and is 270 m long and 7 m D-
shaped . There are 19 single phase Transformers.The construction cum downstream
Surge gallery is provided to reach the tail raceand to facilitate the excavation of the
machine hall , the tail race and pressure shaft.
Page 12 of 35

13. .
Fig1: Block diagram for power station
 TURBINE:
The Turbine used here is the “ VERTICAL FRANCIS TURBINE ” means the
rotating parts of the unit have a vertical axis of rotation. This turbine belongs to
the reaction turbine family. The water is under pressure as it enter the runner and
completely fills all its channel as it passes through . The head for the Francis
turbine is usually between that of Kaplan ( low head ) turbines and that of Pelton
(high head) turbines.
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14.  TURBINE FUNCTION:
The water from the penstock enter the spiral casing. In the spiral casing , the water is
spread around the whole circumference by stay vanes , and is lead in towards the
guide apparatus.The guide apparatus has movable vanes , which are controlled by the
governor and can be set independent of output. After this impact the water continues in
the Draft Tube and out the tail race tunnel. The torque is transferred from the Runner to
the Generator, which is directly connected to the Turbine Shaft. The turbine develops
the power partly due to the velocity of the water and due to difference in pressure
acting on the front and back of Runner buckets such a Turbine essentially consist of
guide apparatus consisting of outer ring of stationary stay vane fixed to the casing of
turbine and an inner ring consist of rotating blade forming a wheel or a Runner. As the
water passes over the rotating blades of the Runner both pressure and velocity of the
water reduced causing a reaction force on the turbine.The guide blades of the turbine
are pivoted about axis an parallel with turbine axis so that quantity of the water
entering in the turbine may be regulated by turning them simultaneously in one
direction or the other, their motion is automatically controlled by Governor. Francis
type turbines can be constructed in vertical or horizontally but horizontal construction
more accessible and have higher speed, but for large machine vertical construction is
preferred to effect higher speed. As compare to Pelton wheel a Francis turbine offer
advantage of high efficiency at full load and at 75% of full load . This turbine can be
designed fir higher specific speed than Pelton Wheel .The gross head of the turbine is
488m and design head is 425m.
 TURBINE COMPONENTS:
• Rotating parts.
• Turbine guide bearings.
• Turbine upper and lower cover.
• Guide vanes.
• Governor (Regulating mechanism).
• Spiral casing.
• Draft tube.
• Shaft seal.
• Dewatering system.
 Rotating parts : There are mainly three rotating parts:
• Runner.
• Turbine shaft.
• Oil slinger.
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15. o Runner:
The Runner has been welded up from crown and band of stainless cast steel to Vanes
from stainless steel plates. The vanes have been machine worked. The crown band
have “Roots” towards the vanes. Air for stabilizing purpose is allowed through the
Runner centre via the shaft seal and drilled holes in the turbine shaft flange. The
moment of force on the runner is transferred to the turbine shaft through the shear
pin connection.
o Turbine Shaft:
The turbine shaft is made of MS steel/Forged Steel with flanges hammered out at
both ends. The turbine shaft and generator shaft are connected by flanges. The
connection Primarily transfer the moment of force through the shear studs.
o Oil Slinger:
The Oil slinger is located below the turbine bearing and connected to the
turbine shaft. Its purpose is to collect the oil from turbine bearing and during operation
bring the oil into rotation inside the slinger cylinder from where it is catched by the oil
scraper and led to the oil cooler and the bearing oil reservoir.
 Turbine Bearing :
Bearing Design:
The turbine bearing is radial vertical slide / guide bearing. The bearing has a
strong construction and a simple manner of operation, which require a minimum of
maintenance. The bearing house is split and attached to the upper turbine cover. It has
two manhole hatches for access and inspection of shaft seal and pipe connections. The
bearing shell consist of two segments, which are bolted together and attached to the
upper side of the bearing house. The shell has four oil pockets and four babbit metal
Surfaces with machined wedge shaped entrances , which ensure a stable centering of
The turbine shaft. The bearing has been fitted with an inspection hatch ,dip stuck for oil
slinger,
Fluid level gauge for bearing house, thermometers and level switches for surveillance
The bearing has been fitted with external oil cooler. This is automatically put into
Operation when the cooling water system is started.
Bearing Function:
When the unit starts the oil slinger start rotating , oil is slung up into the
cylinder section and cover the vertical with a layer of oil. The thickness of this layer
will be determined by the position of the oil scraper. The amount of the oil in the oil
slinger is regulated by means of the oil scraper, which is attached to the bearing shell.
When there is a sufficient rotating speed , the damming up pressure become strong
enough to force the oil up through the ascending pipe through the oil cooler and out
into the bearing house. From there the oil flows down through the four windows in
the bearing house cover and is spread out to the four oil pockets in the bearing shell. A
Page 15 of 35

16. film of oil follow with the shaft in the wedge shaped entrance on the bearing shell and
builds up the guiding oil layer.
 Turbine cover:
The Turbine has two covers:
o Upper cover.
o Lower cover.
• Upper Cover: The upper cover is bolted to the spiral casing ring. It serves
as a bearing for the regulating ring and a support for the upper stationary
labyrinth seal turbine inner cover with shaft seal as well for the longest
trunnion of the vanes. The interchangeable upper stationary labyrinth seal is
made of forged steel and is bolted to the cover. The seal surface on the
labyrinth seal faces the equivalent seal surface on the upper rotating labyrinth
seal bolted to the Runner.
• Lower cover:
The lower turbine cover is bolted to the spiral casing stay ring. It
serves as a support for the short trunnion of the guide vanes, the lower stationary
labyrinth seal and the draft tube cover. Supporting sleeves of Aluminum Bronze for
guide vane bearing have been installed. Corrosion resistant austenite steel has been
welded into the wearing surface of the lower turbine cover between the wear ring and the
lower labyrinth seal.
 Governor:
The Turbine has two servomotors. The connection between the servomotor
and the regulating ring consist of an adjustable connecting rod and a spherical
bearing. It sense the speed of the turbine rotation and generate a signal
proportional to the difference between the turbine speed and the governor speed
reference and therefore develop a hydraulic control signal sufficient to control the
turbine. The adjustable rod is used for pre tensioning the guide apparatus. When pre
tensioning the guide apparatus the guide vanes are given a Moment which
produces a force toward closed position. This compensate for slackening and
deformation in the lever and link connection and provides a closing force greater
than or approximately equal to hydraulic opening force on the openings force on
the vanes with full pressure in the spiral casing.
 Spiral Casing:
The spiral casing the waterway between the penstock and the guide apparatus.
It has been constructed to ensure constant water speed around the whole
Circumference of the guide apparatus. The spiral casing is built from a stay ring and a
plate shell to an all welded construction of fine grained sheel steel .The spiral ring is
consisting of an upper and lower ring connected to each other by welded stay. The
stays has been shaped in a hydraulically favorable way in order to lead the water in
Page 16 of 35

17. towards the guide apparatus with the least possible loss. The spairal casing has been
fitted with outlets for index measurements and a
manhole for inspection. The outlets for pressure measurements , dewatering and air
escape are positioned on the expansion box at the inlet of the spiral casing . The main
part of the spiral casing has been concreted in a solid slab being supported against the
downstream rock wall. The hydraulic force acting on the spiral casing inlet is thereby
balanced against the rock.
 Draft Tube:
The outlet consist of a draft tube and a draft tube steel lining continuing with
a concrete lined tunnel and forms the water way from the runner to the race
Channel. The draft tube cone is welded and consist of two parts. The upper part is
bolted to the lower fixed labyrinth seal. It is made from stainless steel. The lower part
is attached to the draft tube steel lining with a flexible flange connection. It has one
manhole for access to the draft tube and it is fitted with four stub pipes with cover
for installation of an inspection platform. The draft tube steel liner is completely
set in concrete. It has been welded and fitted with a flange toward the draft tube
cone. The draft tube can be emptied into the dewatering pit by slight extension of the
cross section in the direction of the flow from the runner outlet to the end of the plate
covering. The draft tube have 10 segments with a plate thickness of 30 mm and total
wt.34000kg.
 Shaft Seal :
Shaft seal is attached to the inner cover , which again is attached to the
upper turbine cover. Due to the rotation of the water in the gap between the runner and
the upper turbine cover the gaps in the shaft seal will be water free when the turbine
is in operation. In order to prevent the contaminated water downstream of the turbine
to enter past the upper labyrinth seals and up through the shaft seal during start and
stop of the unit. When the shaft has come to a complete standstill the service seal will
be closed , valves in drainage and overflow pipes will be automatically closed and
flushing water pump stopped.At certain output the turbine may need air to the outlet
section of the runner. This ventilation take place through a separate air pipe, which is
connected to the shaft seal support ring. The air pipe is fitted with a check value
preventing the tail water from leaking out during standstill.
 Shaft seal flushing water :
In order to prevent the contaminated water from entering into the shaft seal
during start and stop sequence of the unit and when rotating speed is too low tokeep
the shaft seal dry , the shaft seal flushing water system will provide filtered water at
sufficient water. The intake is from the pressure equalizing piping between upper turbine
cover and draft tube. A centrifugal pump is increasing the pressure and flushing
Page 17 of 35

18. COUNTER
WEIGHT
SERVOMOTOR
OPENING LINE AT 100 BAR
OIL RETURN LINE
DISMANTLING
JOINT
PENSTOCK
BY PASS VALVES
strainer particles above 200 micron is removed. The system will automatically be
put into operation during start and stop of the unit.
 Penstock Dewatering System:
The dewatering system consists of one high pressure drainpipe for each unit.
The inlet is upstream the MIV and the system consist of a gate valve and a hand
manufactured needle valve. Dewatering is made from the penstock to the draft tube
down to the tail water level. After setting the draft tube gate the remaining water is
drained through the draft tube to the dewatering pit from where it is pumped to
discharge outside the draft tube gate by dewatering system.
The movement of MIV is shown in the fig. below:
MIV in Closed Position
Page 18 of 35

19. MIV fully Open
 Guide Apparatus :
The Governors action on the two main servomotors is transferred via rod
connections to the regulating ring . The actual guide apparatus consists of
23 guide vanes, check plates on upper and lower turbine cover as well as guide vane lever
and links.The guide vanes are made of forged stainless steel and had been shaped to
provide the best possible hydraulic conditions. The guide vanes have bearings on
upper and lower turbine covers . These are self lubricating slide bearings
withTeflon covering. The coupling between guide vane and guide vane lever is a pure
friction coupling, thus allowing the guide vane to slide away in case of foreign object
is preventing the guide vane from being closed. An alarm in that case will be
activated. The guide vane lever and regulating ring is connected by links. The links
are joined by self - lubricating bushing on stainless steel pins attached to the
regulating ring and the guide vane lever respectively.
The guide vane movement is shown in the fig.
Page 19 of 35
SERVOMOTOR
OPENING LINE AT 100 BAR
OIL RETURN LINE
DISMANTLING
JOINT
PENSTOCK
BY PASS VALVES

20. Guide
Vanes
Axis
Of Guide Vane
Links
Regulating
Ring
OPENING AND CLOSING OF GUIDE VANES
0o
15o
OPENING AND CLOSING OF GUIDE VANES
Water
0o
0 %
Guide
Vanes
Axis
Of Guide Vane
Links
Regulating
Ring
OPENING AND CLOSING OF GUIDE VANES
0o
15o
OPENING AND CLOSING OF GUIDE VANES
Water
100 %
% open
 GENERATOR:
The vertically mounted synchronous generator converts the hydraulic energy of water
into electrical energy. The generator will be vertical shaft type having salient poles with
closed air circuit ventilation and suitable for coupling to a machine turbine. It will have
static excitation system energizing the field coils. The slip rings, Permanent magnet
generator and mechanical over speed device will be located suitably on a fabricated
shaft, which in turn will be fitted to a rotor spider. The speed of the turbine wheel must
therefore match the synchronous speed of the generator. The generator will have a
combined thrust and guide bearing below the rotor. The generator will have the rating
and characteristic as the components will be designed to withstand seismic forces as
applicable.
Page 20 of 35

21.  Generator Components :
The generator consist of following components-
• Stator.
• Rotor.
• Air water cooling system.
• Slip ring and brush gear.
• Excitation.
• Bearings.
o Stator :
The rotor winding is excited by a direct current and induces a voltagein the stator
winding. This is taken by Bus bar to the main current lines. The stator consist of the
Frame , Laminated stator core and the stator winding embedded in theslots of the
laminated core.
o Rotor :
The rotor and rotor winding are excited with the direct current, and generate a
Constant magnetic field. The rotational movement at the specified synchronous speed
induces a sinusoidal alternating current voltage in all phases of the stator winding.
The rotor will be designed to safety withstand all mechanical stresses imposed by the
maximum runway speed. The static and dynamic balancing of the rotor will be
carried out , as a part of precommissioning test at site and values of rotor
vibrations will be kept with in allowable limits according to satnderds.
HOUSING –
Depending upon the operating condition of the machine, the generator
housing absorb the generated mechanical loading and transfer these to the
foundations.
STATOR FRAME –
The stator frame will be build up of weld able steel plates and will have adequate depth
to prevent distortion during transport or under any operating condition.
STATOR CORE –
The stator core will be built of stamping of high grade , non
aging cold rolled silicon alloy with varnished insulation on both sides. The segments will
be secured to the frame by dovetail notches engaging with correspondingdovetail
key bars welded to stator frame.
ANTI CONDENSATION HEATERS –
Low temperature to prevent, condensation
Page 21 of 35

22. on the winding during period of shut down will be mounted below the winding
located below lower air guide. They are of tubular or box type construction consisting of
a coiled resistant wire embedded in an electrically insulting and heat conducting
compound and protected with a metal sheath.
o Air-Water Cooling:
The mechanical and electrical losses arising in the course of operation of the and
the temperature rise of the components this cause must be reduced by cooling.
generator rotor and stator are air cooled , while the bearings are water cooled. The
generator has a closed cooling circuit and is therefore sealed off on all sides against
the surrounding surface. The foundation walls from the enclosure from the machine
house, and the outer cover separates the generator from the turbine room. The enclosure
at the circumference is provided by the generator pit. The cooling air enters tangentially
through the rotor and enters the stator through the gaps. The air water coolers arranged
after the stator removes the heat that the air has absorbed.
o Slip Ring And Brush Gear :
The collector will be of mild steel and mounted on the top of the generator
tube shaft. The brush gear for the collector will be mounted on insulated studs
supported on the top bracket and will be arranged to permit convenient access for
maintenance and inspection. The insulation for slip rings and their connections will be
non-hygroscopic and oil resistant. The slip ring system transfer the direct current
necessary for excitation of the rotor from the fixed brushes to the slip ring and thus to
the rotor poles.
o Bearings :
The two different bearings are attached to the rotor i.e. Guide bearing and
Thrust bearing. The thrust bearing must take up the entire weight of the rotating
components of the machine set (rotor and turbine) and axial thrust of the hydraulic
machine. Both journal bearing together with turbine journal bearing ensure a
centered machine run from the standstill up to the runway speed of the turbine.
Thrust Bearing : Thrust bearing is of pivoted segmental pad type in which the
stationary parts consist of a set of Babbit segmental pad supported on circular pad
supports made of alloy steel forgings. The bearing is self lubricated and immersed in oil
bath in which plugged n type of water cooled oil coolers are placed to remove the
bearing losses. Radial and circumferential movement of the pads is prevented by
means of stoppers.
Guide Bearing : The guide bearing will be of the pivoted pad type consists of arrow of
white metal pads arranged in a support ring to bear on a journal surface. A pivot bar
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23. will be bolted to the back of each guide pad to enable the pad to rock slightly to take
up a suitable position and facilitate formation of oil film when running. The air surface
above the oil surface will be vented to the atmosphere by vapor pipes and air pressurized
oil vapor seal will be fitted to prevent the escape of oil vapor into thegenerator air
circuit.
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24. o MAIN ELECTRICAL EQUIPMENTS :
 Synchronous Machine (Generator) :
It is a three phase double excited machine because its field winding is energized
form a dc source and its armature winding is connected to an ac source. Its working as
a generator delivers or exports ac power. A synchronous generator is universally
employed for the generation of three- phase power at all generating stations. Most of the
synchronous motors are of silent pole type as it is most suitable for the slow speed water
turbine generators and are called Hydrogenates. There are six generators in the power
house each having 250 MW capacity and driven by speed of 300 rpm. Each generator
is having 96 brushes in which 48 are positive and 48 are negative. There are two slip
rings one is positive and other is negative. The slip ring give excitation Current to
rotor through brushes according to load.
Generator specification:
Rated speed 300 rpm Turbine Rated Head 428 m
Rated output 250 MW Rated Output (Generator) 278 MVA
Power Factor 0.9 Terminal Voltage 15.75 KV
Manufactured By ALSTOM / GERMANY
 Excitation System :
In large synchronous machine the field winding is always provided on the rotor.
Some important excitation systems are :
DC Exciters : This is an old conventional method of exciting the field winding of
The synchronous generator. Here three machines pilot exciter, main exciter and three
phase alternator are mechanically coupled and therefore driven by the same shaft. The
pilot exciter feed the field winding of the main exciter. The dc output from the from
the main exciter is given to the field winding of the main alternator through brushes
and slip rings. The conventional method of excitation suffers from cooling and
maintenance problem as associated with the slip ring, brushes and commutators as the
alternator rating rise. This trend led to the development of the static excitation and
brushes excitation system.
Static Excitation : Here the excitation voltage for the main alternator field is drawn
from output terminal of the main 3- phase alternator. For this purpose a three phase
transformer TR step down the alternator voltage to the desired value. This three phase
voltage is fed to the 3-phase full converter bridge using thyristors. The power output
from the thyristor is delivered to the field winding of the main alternator through
brushes and slip rings. For initiating the process of static excitation first of all field
winding is switched on to the station battery bank to establish the field current in
alternator. The alternator aped is adjusted to the rated speed.
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25.  Braking and Jacking System :
The generator brakes will consist of a number of steel shoes mounted on a
vertical piston moving in cylinder and will operate against a polished circular steel
brake track located on underside of rotor. Brakes will be automatically applied when
the speed of the rotor reduce to a preset value and will remain applied continuously so
that the unit stops completely. The brakes will also serve as a convenient means for
jacking the rotor for maintenance purpose for this a complete hydraulic rotor jacking
unit will be provided. Limit switch is provided which shows the indication that the
rotor is raised to maximum permissible limit. The arrangement of piping will be such
that after jacking system has been in use air under pressure can be applied to the
system to clear the pipes of oil .
 Brake Dust Collector :
The brake dust collector consists of an extraction unit, hoppers around brake
assembly for trapping the brake dust and flexible hoses for connecting hoppers to the
extraction unit. The extraction unit will have a motor driven exhaust fan and will be
fitted with an easily removable sheet steel bin for collecting heavy dust. The lighter air
born particles will be collected by a suitable fabric based filter. The starter panel for
motor having provision for automatic start and stop of the motor will also be provided.
 Oil Vapor System:
The oil vapor extraction system sucks of the vapor of generator bearing. This oil
vapor is generated during operation and led to the filters outside the generator room.
The pollution of the machine is this way avoided.
General:
As soon as the generator starts running with the operating temperature , the oily fog Is
developed in the bearing oil container by very finally distributed oil drops .
Breathing” the oil in bearing or pressure differences inside and outside the bearing
cause the oil vapor, a mixture of air and oil that produces a different wetting of the
parts and surfaces at the outside. These damp places result in providing an ideal
background for dirt beginnings . During high speed of rotor or high load the
differential pressure increases also between the bearing chambers and the
environment. In this case the bearing seal and shaft oil separators cannot hold back the oil
mist any longer. To prevent this then generator was equipped with a special oil vapor
suction system.
Design And Function:
Two pipelines are attached parallel above at the upper and lower bearing
chamber. The two pipes are led outward to the two suction filters. The particles
separated by the filter run off on the inside of the separation pipe. The ventilator for the
production of suction flow is inserted above the separation pipe within the clean air
side. An activated Carbon filter is mounted behind the electrostatic unit to absorb smells
and gases. Cleaned air is blown by the activated carbon filter into the open air.
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26.  DAM:
The function of the dam is not only to raise the water surface to create artificial
head but also to provide the poundage. Storage and facility for diversion int conduit. The
dam is straight gravity type dam having the height 62.5 m on Satluj River at Nathpa
to divert 405 comecs of water through four intakes. The dam is most important
part of the hydro electric project. It is built of concrete or stone masonry on a rock
hill.The length of the dam at the top is 170.2 m consisting of 63 m as non over flow
structure and 88.2 m as sluice block section with each having the size 7 x 7.35 m With
crest 1458.0 m.
Catchment area of the dam 49820 sq.km.
Design Flood 5660 cumecs.
Maximun water level 1490.50 m.
Minimum water level 1474.00 m.
• Selection Of Dam:
Selection of dam to be constructed at a particular site depends upon topography,
Foundation survey , soil condition and other characteristic of the location . The
foundation of the dam must be sufficiently strong to withstand the weight of the
structure, water pressure etc. without crushing , sliding or permitting movement of the
structure .The foundation of the dam should be sufficient impervious so that there will be
no objectionable passage of water.
• Spill Way Gates:
There are two spill way gates on the dam situated at Nathpa on Satluj River. These act as
a safety valve. It discharges the overflow water to outside the dam when reservoir is
full . This condition arises during flood. These gates can be opened and shut
automatically when water overflows of the level and closes when water reaches in the
level.
• Radial Gates:
There are five radial gates in the dam located in the lowest point of the dam. Radial
gates are always closed. They can be opened only in condition when trees come in
dam or reservoir due to flood. All these things can be discharged through these gates. So
radial gates can be opened in these conditions.
• Intake Gates:
Intake structure comprises of four intakes of about 500 m long these inlets of river
has been designed to handle a discharge of 846 cumecs. Intake gates are trash racks
type. The suitable opening of 19.26 m * 15.7 m at the start of the base is reduced to
6m*5.2m through a suitable transition. A continuous skimmer wall with top at EL.
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27. 1468.73 m is made in front of all the four intake gates to restrict the entry of sediments
into the intakes. An opening provided in the skimmer at the downstream end through
which the bigger sediments are flushed out. Through four intake gates the water goes to
desilting chamber.
• Desilting Chambers:
An underground desilting arrangement comprising of four chambers is made on the left
bank of the river Satluj to exclude silt particles down to 0.2 mm size from water before
it enter head race tunnel. Four intakes has been made to feed four chambers through
each tunnel respectively. The flow to the chambers is regulated by the gates at the intake.
There are four Desilting chambers each have a three meter wide collection trench in the
centre running along its length. The sediments from the collection trench will fall down
to the flushing tunnel 5m in diameter horse sluice. The flushing gates will be provided
at the junction of flushing conduits and main flushing tunnel. Top of each chamber is
connected to the head race tunnel through link tunnel of diameter 5.02m. It reduces
the flow of water and also prevents the particle of 0.2 mm to the turbine. Here the
water flows with a velocity of 33.4 cm/sec.
• Silt Flushing Gates:
There are four silt flushing gates they create a pressure in the desilting chamber and
Suck out salt and particles at the edge of the desilting chamber.
• HRT Intake Gates:
After desilting chamber water goes through HRT intake gates. They are also four in
no. The water at the output of each HRT intake gates are combined to main head race
tunnel.
Head Race Tunnel:
The head race tunnel is 27.3 km long and have diameter 10.15m. it is one of the largest
Head Race Tunnels in he world. The tunnel diameter is based on the techno economic
studies for a discharge of 405 cumecs at a flow velocity 5m/sec.The rock cover of
head race tunnel vary from about 90 m to about 1480 m along its length the head
race tunnel is provided with steel lining where the rock support is not expected. There
are six audits in the head race tunnel :
o Nathpa Adit EL. 1450.89m.
o Sholding Adit EL. 876 m.
o Nugalsari Adit EL 647 m.
o Wadhal Adit EL. 842 m.
o Manglad Adit EL.691 m.
o Rattanpur Adit EL.1357 m.
Sholding Works: In order to augment the flow during the lean months of water
scarcity the water of the sholding khad one of the cribularies of Satluj river is having a
26m long tunnel that divert a discharge of 8 cumecs through a tunnel having a
diameter of 2m. from here the water will enter the hooper and desilting chamber.
Page 27 of 35

28. • Surge Shaft:
The main surge shaft is located at the intake of the penstock at 27.3 km form head
race tunnel. It is just like wall. Its function is to avoid the water hummer effect. Three
penstocks are taken from the surge shaft at the bottom , two from side of surge shaft
and one is taken from the centre of the surge shaft. A 12 m dia Horse shoe shaped
185m long lower gallery at EL 1370m has also been provided. The minimum water
level in the surge shaft is about 30 m. The surge shaft is concrete lined of adequate
thickness. It is the deepest surge shaft in the world. Three drainage galleries at different
elevations has been provided around the surge Shaft to relieve the external water
pressure on the lining.
Pressure Shaft:
Three shafts of diameter 4.9m and length varying from 619m to 660m take off from
the surge to an angle of 45 degree to the horizontal. These are lined with high tensile
steel of thickness varying from 32mm to 60mm. Each pressure shaft is bifurcated
into the branch tunnel of dia 3.45 m. Each pressure shaft is designed to carry a
discharge of 315 cumecs . Butterfly valve housed in valve chamber has been
constructed in the horizontal reach of pressure shaft for its repair and maintenance. A
spherical valve has been provided in each penstock branch tunnel inside the machine
hall cavern to enable closing of penstocks whenever required.
Other features of surge shaft :
 pressure relief valves has been provided in the top 80 m of the concrete lining to
reduce the external pressure as an additional margin.
• A 25 cm deep sill beam has been provided on the collar of the surge
shaft to prevent any trash lying on the pond floor.
• The slopes of the top pond are well drained. The drainage water is disposed
off very far away from the pond.
• Due to very high head and difficulty in maintaining verticality of guide rails,
stop logs could not be provided in the surge shaft.
• An inspection ladder has been provided in the connecting shaft forming
approach to the drainage galleries.
• Valve Assembly:
The valve assembly consists of a top and bottom valve body and a double lattice
valve disc assembly with all necessary seals, bearings and seats. A valve chamber
79.52 m long 9.5 m wide and 22.34 m high has been excavated 106 m downstream of the
surge shaft essentially in quartz mica schist.
Valve Body :
The valve body is manufactured in cast steel and are flanged on both sides. The top
and bottom sections are assembled with an ‘O’ ring seal and locilite 574 between
faces and located with stainless steel dowels. The valve incorporate support feed
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29. fabricated with the valve body to available the valve to secured to the foundation by the
use of soleplates.
Valve Seat:
Two valve seats are fitted within the valve body to form seal with each disc seal on
The lattice blade with valve in the closed position. During normal operation the
Downstream forms the water seal. The downstream stainless steel ring locates in a
recess machined with in valve body and is machined with the ‘O’ ring seal located
groove. A Nitrile rubber ’O’ ring seal is assembled in the groove and prevent leakage
b/w the valve ring and seat ring.
Maintenance Seal :
The purpose of the guard wall maintenance seal is to provide a double isolation when
used in conjunction the service seal. The principle of double isolation is essential
whenever personnel are required to enter the downstream – dewatered penstock. The
upstream and downstream chambers formed between the seat ring and the valve body are
connected by drilling to a penstock pressure water control system.
Air Release Valve:
Fitted on the top of the valve body is a orifice air release valve, operated by a float.
The valve release air to atmosphere during fitting of the valve body and when full of
water seals the orifice to prevent leakage. Most of the air trapped during penstock
filling will be released via the four anti vacuum valves. When all four anti vacuum
valves are closed all remaining trapped air is released via these valves operated by a
float.
Anti-Vacuum Valve Assembly:
Four Anti-Vacuum valves are fitted and two on each side of the downstream pipe
works. The 500mm nominal diameter float operated anti vacuum valves sense the
pressure drop downstream of the penstock guards valve and open and allow air into
the penstock preventing the formation of vacuum. When the chamber is filled with
water the float rises extending the springs and contacts the Nitrile rubber sealing ring.
• Transformer Description:
The Transformer is having different parts such as:
Conservator :
It is generally used to conserve the insulating property of the oil
From deterioration and protect the transformer against failure on
account of bad
Quality of oil.
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30. Silica Gel Dehydrating Breather:
The breather is used to prevent entry of moisture inside the transformer tank. The
breather consists of silica gel. When air is taken in or out of the transformer due to
contraction or expansion of oil in the tank, the silica gel absorbs the moisture and allow
the air free form moisture to enter the transformer.
Gas Operated Relay:
It is a gas actuated relay used for protecting oil immersed transformers against all
type of faults. It indicates presence of gases in case of some minor fault and takes out
the transformer out of circuit in case of serious fault.
Bushings:
Bushings are made from highly insulating material to insulate and to bring out
terminals of the transformer form the container.
Oil Gauge:
Every transformer is provided with an oil gauge to indicate the oil level.
The oil gauge may be provided with the alarm contacts which gives an alarm when the oil
level has dropped beyond permissible height due to oil leakage etc.
Tappings :
the transformers are usually provided with few tappings on the secondary
side so that output voltage can be varied for constant input voltage.
Radiator :
In large capacity transformer above 50 kva the increase in oil temperature is quite high.
On account of losses in the transformer the oil near the winding gets heated and
travels upward along the winding and return through side pipes (radiators).
Winding Temperature Indicator :
It is a device which indicate the temperature of winding of transformer and possible
damage to the transformer due to overload can be prevented. The sensing bulb of dial
thermometer is inserted inside the heating coil. The terminal of heating coil are
connected to temperature gauge.
• Some Planning And Design Aspect :
Cable Anchors:
It was found that a large number of cable anchors of 200 tones capacity shell be
needed in the dam complex. 285 cable anchor have been provided for
the excavation in the intake area. Another 185 have been installed in the left bank of
dam and road to the top of dam. 131 cable anchors are being installed for stabilization of
both the banks in the plunge pool area extending from 90 m downstream of dam axis
to 150 m downstream of dam axis.
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31. Reservoir Flushing :
Satluj river carries heavy sediment load during snowmelt and monsoon season.
Provision of low level sluices in the dam ensures outflow of sediments from the
reservoir whenever the water availability is more that the design discharge. Further
flushing of reservoir behind Nathpa dam is also envisaged once or twice every year
when the discharge in the river exceed 1500 cumecs.
Desilting Cavern:
The four desilting chambers are required to function under adverse conditions of
both external and internal water pressure. Complete analysis both for the rock
support during excavation and long term stability during
maintenance condition was carried out through numerical modeling which involved
through investigation based on field and laboratory testing of rock mass properties and
geological details of joints, major shear planes etc.
Head Race Tunnel
Tunnel Lining In Hot Water :
Hot water has been encountered in the HRT downstream of Wadhal Adit junction
for a length of about 3 km. the chemical test of water has revealed that it can be
aggressive to normal concrete. Special precaution in concrete mix design with use of
pozzolana were taken to counteract the aggressiveness.
Steel Liner In HRT :
Steel liner with length of 710 m and 375 m respectively have been provided at Manglad
and Daj creek of the head race tunnel where rock covers are inadequate against maximum
internal water pressure which ranges from 2.8 to 3.1 MPa. With a view to avoid stress
relieving and limit the plate thickness to 40 mm the diameter of the steel liner has
been reduced to 8.5 m with transition both upstream and downstream to 10.15 m
diameter. In the absence of information of water table in the hill full external pressure
up to the natural surface has been taken in the design of steel liner for the external water
pressure.
Maintenance Access :
Being a very long HRT it would be difficult to inspect the same in case of
emergency / shutdown. Keeping this point in view intermediate vehicular accesses
have been planned through Nathpa and Wadhal construction adits where steel doors in
an opening in the concrete plugs has been provided.
Power House Cavern :
Only rock bolting and shotcreting has been adopted for the excavation in the machine
hall cavern. An integrated design approach comprising empirical design through the
NGI’s “Q” system, numerical modeling and analysis of
geological features were adopted for the support system. A complete analysis of
various stages of excavation was carried out through numerical modeling and
Page 31 of 35

32. deformation was monitored through multi - point borehole extensometers . The
deformation observed was within the predicted limits.
Page 32 of 35

33. Results and Discusssion :
The company is having well established strategy for imparting training to the
employees and involves other professional people to motivate the employees for
good working. The training imparted is two dimensional i.e. in house training
and through external professional institutions as well.
The outcomes of the hydro – electric project is that it is not only providing the
electricity to the states of India ( Northern India ) but offering jobs to the
freshers which enhances stability to the nation . Moreover , besides job this
organization also gives the opportunity to students to have a vocational training /
summer training and apprentice training .
Other various kinds of programs is being held by the SJVNL every year at
state and national level . Incorporated in the year 1988, the Company is fast
emerging as a major power player in the country. SJVN is successfully operating the
country’s largest 1500 MW Nathpa Jhakri Hydropower Station and is setting new
benchmarks in generation and maintenance year after year, after having tackled the
silt erosion problems in under-water turbine parts .
Beginning from a single hydropower project company, SJVN today has a footprint
in a diversified set of power projects, which includes Hydroelectric Projects in
Himachal Pradesh, Uttrakhand, Aurnachal Pradesh and in the neighboring
countries of Nepal and Bhutan, a Thermal Power Project in Bihar, a Power
Transmission Project in Nepal, Wind Power project in Maharashtra and Solar
Power Projects in Gujarat & Rajasthan.
SJVN has expanded its horizons and has drawn up ambitious plans to develop into a
fully-diversified trans-national power sector company having presence in various
conventional and non-conventional forms of energy.
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34. Conclusion and Future Scope :
SJVNL is in far much better position in all spheres . It has a good profitability
ratio which keeps increasing year by year . The company is mainly focusing on
To drive socio-economic growth and optimize shareholders and stakeholders
interest by :
• Developing and operating projects in cost effective and socio-environment
friendly manner.
• Nurturing human resources talent with care.
• Adopting innovative practices for technological excellence.
• Focusing on continuous growth and diversification.
The company is aiming is to achieve the :
• Fulfilling social commitments to the society. Achieving constructive
cooperation and building personal relations with stakeholders, peers, and
other related organization.
• Striving clean and green project environment with minimal ecological and
social disturbances.
• To strive for acquiring Nav Ratna Status.
SJVN has signed an MoU to develop and operate the 4000 MW Ultra Mega Solar
Project in Sambhar area of Rajasthan with five other PSUs: BHEL, PGCIL, SSL,
REIL and SECI. SJVN has 16% equity in the country’s largest Solar Energy
project.
SJVN is committed to generating reliable and eco-friendly power by means of state-
of-art technology, excellence in engineering and continual improvement in quality
management. SJVN, as a technology-savvy corporation, has established and is
following sound business, financial and regulatory policies. SJVN believes that
employees are its most valuable assets and has evolved a growth oriented
development strategy for its Human Resources.
Page 34 of 35

35. Bibliography
JOURNALS
• Corporate booklet of SJVNL
• Satluj Vani-Bi- monthly house journal
• Annual Reports of SJVNL & NHPC
SITES
• http://www.sjvn.nic.in
• www.nhpc.co.in
• www.studymode.com
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