tehri hydro development corporation india limited

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TEHRI HYDRO DEVELOPMENTCORPORATION INDIA LIMITED

TEHRI

A TRAINING REPORT

SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OFTHE DEGREE OF

BACHELOR OF TECHNOLOGY(Mechanical Engineering)

SUBMITTED TOLOVELY PROFESSIONAL UNIVERSITY, JALANDHAR

SUBMITTED BY Name of Student University Reg No.Kuldeep Semwal 11009475

01-06-13 to 12-07-13

Lovely Professional University, JalandharPUNJAB


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ACKNOWLEDGEMENT

I am very much grateful and obliged to Mr. A.L. Shah, General Manager (Project Head) for providing

me the facilities and opportunities he has extended to me.

I would like to place on record my deep sense of gratitude to Mr .Rakesh Bahuguna, Deputy Manager

in Hydro Mechanical Department of Tehri Dam for his generous guidance, help and useful suggestions.

I also wish to extend my thanks to Mr. Kamal Joshi and other workers for guiding and providing the

knowledge related to machinery and processes.

I am extremely thankful to Prof _________, HOD, Lovely Professional University Jallandhar, for

valuable suggestions and encouragement .

I am also thankful to Mr. Sushil Kumar, Training and placement officer, LPU, Jallandhar for providing

the opportunity to get the knowledge.

Signature of Student

Kuldeep Semwal

[11009475]


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ABOUT COMPANY

THDC India Limited is a Joint Venture of Govt. of India and Govt. of Uttar Pradesh. The Equity

is shared in the ratio of 3:1 between GoI and GoUP for the Power Component. The Company

was incorporated in July 88 with the initial mandate to develop, operate & maintain the 2400MW Tehri Hydro Power Complex (comprising of 1000 MW Tehri Dam & HPP, 1000 MW Tehri

Pumped Storage Plant & 400 MW Koteshwar HEP) and other hydro projects.

The Memorandum and Articles of Association of the company has been modified to reflect

the current business reality of projects outside Bhagirathi valley. The Company has been

converted to Public Limited Company and object clause has been amended to incorporate

development of Conventional/ Non-conventional/ Renewable sources of Energy and River

Valley Projects.

THDC is consistently profit making company since the commissioning of Tehri Dam & HPP in

the year 2006-07. THDC paid to GoI & GoUP a maiden dividend of ` 97.50 Cr. for the year

2007-08 and dividend of ` 98.00 Cr. for the year 2008-09. Further dividends of ` 145 Cr, ` 181

Cr and ` 212 Cr has been paid respectively for years 2009-10, 2010-11 and 2011-12.

THDCIL has been conferred with prestigious award International Milestone Project of

International Commission of Larg e Dam (ICOLD) for Tehri Dam Project in Oct.09 at China,

considering the uniqueness of its design and construction features.

THDCIL is aMiniratna Category I Schedule A company by the Govt. of India. The authorized

share Capital of the company is ` 4000 Cr. The Paid up capital as on March12 is ` 3297.58 Cr.

THDCIL also plans to diversify into non conventional and renewable sources of energy viz. solar

and wind power. THDCIL has taken initiatives to venture into the Wind Energy sector. THDCIL

is looking forward to install 50MW Capacity wind farm initially as an Investor. THDCIL has

taken initiative for establishing grid connected Solar Power Project in U.P. The State Nodal

Agencies have been requested to allot the required land for the Solar Power Project.

THDCIL has been conferred the Power Line Award in the category of 'Best Performing

Generation Company (in Hydro Sector) from the Hon'ble Union Minister of Power in May

2012. THDCIL has also been conferred SCOPE Meritorious Award for Corporate Social

Responsibility and Responsiveness in April 2012.


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TABLE OF CONTENTS Page No.

Acknowledgement iiAbout Company/industry/institute iii

List of Tables iv List of Figures v List of Abbreviations viChapter 1: INTRODUCTION

1.1 GENERAL 2

1.2 TEHRI DAM & HPP (1000 MW) 3

1.3 KOTESHWAR HEP (400 MW) 3

1.4 TEHRI PUMPED STORAGE PLANT (1000 MW) 4

1.5 SALIENT FEATURES 6

Chapter 2: Project Work2.1 SPILLWAYS 82.2 POWER HOUSE COMPLEX 132.3 GENERATOR 162.4 TURBINE 192.5 TRANSFORMER 212.6 GAS INSULATED SWITCHGEAR [GIS] 222.7 COMPUTERIZED CONTROL SYSTEM (CCS) 242.8 OPERATION AND MAINTENANCE 25

Chapter 3: RESULTS AND DISCUSSION 28

Chapter 4: CONCLUSION 29

References 30

Data Sheet 31-35


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List of Tables

Table 1. Details of generation from Tehri Power Station for the current F.Y. (2013-14) .......................... 3Table 2. Details of generation from Koteshwar HEP ................................................................. 4Table 3. Salient features of Tehri Dam ....................................................................................................... 6Table 4. Power output on different Heads .............................................................................................. 21


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List of Figures

Figure 1. Power Production from various projects of THDC ...................................................................... 2Figure 2. General Layout of Tehri HPP & PSP ............................................................................................. 5Figure 3. Main Dam cross section and detail of different zones of material ............................................ 5Figure 4. View of Dam Top ......................................................................................................................... 6Figure 5. A View of Chute Spillway ............................................................................................................. 8Figure 6. A view of Right Bank Shaft Spillway .......................................................................................... 10Figure 7. A view of Right Bank Shaft Spillway .......................................................................................... 11Figure 8. View of intake of HRT ................................................................................................................ 11Figure 9. A View of Generator [Machine Hall] ......................................................................................... 11Figure 10. View of Frances Turbine .......................................................................................................... 11Figure 11. A View of Gas Insulated Switch Gear ...................................................................................... 11Figure 12. A View of Computerized Control System ................................................................................ 11


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Abbreviations

FRL-Full Reservoir Level

MDDL-Minimum Draw Down Level

DC- Desilting Chamber

GIS-Gas Insulated Switchgear

TRT-Tail Race Tunnel

TWL-Tail Water Level


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CHAPTER 1

INTRODUCTION TEHRI DAM


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The Tehri Dam is the highest dam in India and one of the tallest in the world. It is a multi-

purpose rock and earth-fill embankment dam on the Bhagirathi River near Tehri in

Uttarakhand, India. It is the primary dam of the THDC India Ltd. and the Tehri hydroelectric

complex. Phase 1 was completed in 2006, the Tehri Dam withholds a reservoir for irrigation,municipal water supply and the generation of 1,000 MW of hydroelectricity. The dam's 1,000

MW pumped-storage scheme is currently under construction.

Tehri Hydro Power Complex (2400 MW), comprises the following components:

1. Tehri Dam & Hydro Power Plant (1000 MW)

2. Koteshwar Hydro Electric Project (400 MW)

3. Tehri Pumped Storage Plant (PSP) (1000 MW)

Govt. of India approved the implementation of Tehri Dam & HPP (1000 MW) in March, 1994

along with committed works of Koteshwar HEP and essential works of Tehri PSP, as Stage-I of

Tehri Hydro Power Complex. All the four units of Tehri Power Station were commissioned in

the year 2006-07. This project has become the landmark and pride of the Nation as a whole.

Two Units of Koteshwar HEP were commissioned in Mar, 2011 and 3 rd and 4 th unit were

commissioned in Jan, 2012 and Mar, 2012 respectively.

Figure 1. Power Production from various projects of THDC


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1.2 TEHRI DAM & HPP (1000 MW)

(UNDER OPERATION)

Tehri Dam & HPP (1000 MW) comprises a 260.5 M high Earth & Rockfill dam which is one ofthe highest dams of its type in the world, a Spillway System designed for PMF of 15540 cumecs

and a drop of 220m, having one Chute Spillway and four Shaft Spillways and an underground

Power House housing four Turbine/ Generator sets of 250 MW each, designed to operate with

a head variation of 90 m.

Project was commissioned in 2006-07 and all four machines of Tehri Power Station are under

commercial operation. Besides providing much needed power to the Northern Grid, the

command area is availing irrigation benefits from the Project and drinking water is being

supplied to Delhi and UP.

1.3 KOTESHWAR HEP (400 MW)

(UNDER OPERATION)

Koteshwar Hydro-Electric Project (400 MW), located 22 km downstream of Tehri, is an integral

part of Tehri Power Complex comprising of Tehri Dam & HPP (1000 MW), Tehri PSP (1000MW)

and Koteshwar HEP (400MW) to develop Hydro-electric potential of river Bhagirathi. It will

facilitate the functioning of Tehri Power Complex as a major peaking station in Northern grid

as reservoir created by Koteshwar Dam having a live storage capacity of 35.0 MCM will

S.No. Month Generation Target(MU)

Achievement(MU)

1 April-13 199.62 188.68

2 May-13 194.02 244.26

3 June-13 168.45 423.70 Total

(As ofJune-13)

562.09 856.64

Target Year(2013-14)

2797.00 856.64

Table 1.Details of generation from Tehri Power Station for the current F.Y. (2013-14)


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function as lower (balancing) reservoir for Tehri PSP. This project is also regulating water

releases from Tehri reservoir for irrigation purpose.

Generation

Generation

Target (MU) Achievement(MU)

( F.Y. 2011-12) 537.00 607.60

(F.Y 2012-13) 1145.00 1164.05

April-13 92.47 84.75

May-13 99.33 103.02

June-13 97.32 193.19 (F.Y.2013-14)

( As of June-13) 191.80 380.96

Target ( F.Y. 2013-14) 1155.00 380.96

Table 2.Details of generation from Koteshwar HEP

1.4 TEHRI PUMPED STORAGE PLANT (1000 MW)

Tehri PSP comprising of four reversible pump turbine units of 250 MW each involves

construction of an Underground Machine Hall on the left bank of river Bhagirathi. The main

feature of the Project is the large variation of about 90 m between the maximum and

minimum head, under which the reversible units shall operate. The operation of Tehri PSP isbased on the concept of recycling of water discharged between upper reservoir to lower

reservoir. The Tehri Dam reservoir shall function as the upper reservoir and Koteshwar

reservoir as the lower balancing reservoir.

On completion, additional generating capacity of 1000 MW, peaking power will be added to

the Northern Region (annual generation of 1268 million units). For pumping operation of

reversible units during off-peak hours, the energy requirement will be of the order of 1712

MU limited to maximum of 1000 MW during off-peak hours. With the construction of Tehri

PSP, Tehri Hydro Power Complex shall function as a major peaking station having an installed

capacity of 2400 MW.


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SHELLSHELL

RIP-RAP

MAIN DAM AXIS

INSPECTIONGALLERY

FINEFILTER

EL. 839.5 M

U/SD/S

COFFER DAM

RIP-RAP

FSL 830.0 M

COARSEFILTER

EL. 632.0 M

MAIN DAM CROSS SECTION

TEHRI HYDRO DEVELOPMENT CORPORATION LIMITED

SHELL : 201.6 LAC CUM

CLAY : 35.3 LAC CUM

FILTERS : 15.10 LAC CUM

RIP RAP : 27.8 LAC CUM

TOTAL QTY OF FILL PLACEMENT : 279.8 LAC CUM

Figure 3. Main Dam cross section and detail of different zones of material

Figure 2. General Layout of Tehri HPP & PSP


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SALIENT FEATURES:

Nature of Scheme: Storage scheme Hydrology Normal Annual Rainfall 1016 to 2630 mm. Maximum recorded flood discharge 3800 Cumecs

dopted maximum flood for diversion duringmonsoon period 8120 Cumecs

Probable maximum flood 15540 Cumecs Routed Flood 13248 Cumecs Reservoir Full Reservoir Level (FRL) EL 830 m. Maximum Level during design flood (MFL) EL 835 m Dead Storage Level EL 740 m.

Gross Storage 3540 MCM Dead Storage 925 MCM Live Storage 2615 MCM

ater Spread at full Supply Level EL.830 m. 42 Sq.km. ater Spread at dead Storage Level EL.740

m. 18 Sq.km.

Table 3. Salient features of Tehri Dam

Figure 4. View of Dam Top


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CHAPTER 2

TRAINING WORK IN HYDRO MECHANICALDEPARTMENT


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2.1 SPILLWAYS

Spillways are used to discharge the excess water from the reservoir. These are designed and

constructed for making it possible that there is no harm to the valuable structure of dam during

extreme flood condition. The total discharging capacity of all spillways is 13,000 cumecs (cubic-meter/sec). The spillway system has been designed for a probable maximum flood (PMF) of

15,540 cumecs. Probability of flood of this magnitude is considered as 0.01% (i.e. 1 in 10,000

years). The routed discharge corresponding to MWL of 835m through the spillway would be of

order of 1,340 cumecs. It would involve a drop of 220m which has been negotiated by

construction suitable energy dissipation arrangement of well designed stilling basin. The

maximum velocity of flow would be about 55m/s. There are basically three types of spillways

installed:

1. CHUTE SPILLWAY:

The Chute spillway has been provided to negotiate gross head of about 220m and

the velocities generated are of the order of 55m/s at the end of glacis. Aerators have

been conferred to provide an air cushion under the water flowing over the concrete

surface of chute so as to save the surface from cavitations damage.

Figure 5. A View of Chute Spillway


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The Stilling Basin (L=140m, W=50m) has been designed as monolithic concrete

structure in the upside portion under which lies a shear zone. The size of monolithic

concrete block being placed in Stilling Basin is (L=60m, W=80m). Placing such a large

Stilling Basin on a wide shear zone is unique. Baffle wall is provided for the dissipation of the energy. It dissipates about 26% of the

energy.

Specification:

Crest Level : EL 815m

Type : Radial Gated and Stop-log

Water Way : 3 baysSize : 10.515.5m

Length : 578m

No. of Aerators : 3

Stilling Basin : Floor Finish Level, EL 596m

Length of Stilling Basin : 218m

Type of hoist- Radial : Rope drum hoist

Stop-log : Gantry Crane Design Discharge : 5480 cumecs

2. SHAFT SPILLWAY:

Apart from the chute spillway four vertical shaft spillways have been provided.Negotiating a head of about 220m through vertical shaft spillway has been done forthe first time for such a big head.

The right bank vertical shaft spillway have been joined with existing diversion tunnelsT-3 and T-4 eccentrically through a narrow section including swirling motion to the

flow for energy dissipation in shaft to avoid extensive erosion damage from the waterfall.

In the left bank shaft spillway the junction of vertical shafts with the horizontaltunnel, the air accompanied the flow in vertical shaft, is forced to be located in acentral core by way of centrifugal force. This air core is the pressurised air zone fromwhere air is taken out to the atmosphere through de-aeration tunnel.


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Specifications:

1. Right bank shaft spillway

Crest Level : EL 830.2mType : Radial Ungated and Stop-logNo. of Shafts : 2Diameter of the Shaft : 12mHeight of Shaft : 225mType of hoist- Radial : Rope drum hoistStop-log : Electric Winch

Design Discharge : 1900 cumecs each

Figure 6. A view of Right Bank Shaft Spillway


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2. Left bank shaft spillway

Crest Level : EL 815mType : Radial Gated and Stop-logNo. of Shafts : 2Diameter of the Shaft : 12mHeight of Shaft : 203m Type of hoist- Radial : Rope drum hoistStop-log : Electric Winch Design Discharge : 1900 cumecs each

Remark: Out of 7 units, 6 units of stop log gate are common for both chute & shaftspillway. Bottom units for both chute & shaft spillway are separate

Figure 7. A view of Left Bank Shaft Spillway


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3. INTERMEDIATE LEVEL OUTLET(ILO):

ILO is at an elevation of 700m and is 276m long joining T-3 shaft spillway through a tangential

junction. Application of special coating of polyurea is applied for abrasion resistance in ILO.

The main function of ILO is that to regulate the water at the downstream when no unit is

operational.

Specification:

Crest Level : EL 700m

Type : Radial Gated and EmergencySize : 4.5m6mLength : 276mType of hoist- Radial : Hydraulic hoist

Emergency : Hydraulic hoistDesign Discharge : For regulation

REMARK: Common power pack for both radial & emergency gates

4. MAINTENANCE GATE SHAFT(MGS): MGS main function is to carry maintenance work in Tunnel and Penstock in between the HRT

and the butterfly valve.

Specification:

Crest Level : EL720 mType : Fixed Wheel GateNos./Set : 3Size : 5m11mWeight : 112 mtType of hoist : Gantry Crane with automatic lifting beamHoist Capacity :160 tonDesign Head : 110 mSealing arrangement :Side, Bottom and Top seal


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2.2 POWER HOUSE COMPLEX

The power house at Tehri project is an underground power house located on left bank. The

power house is housing 4 units of 250MW each and other appurtenant arrangements. The work

designated as power house works include intake structure, controlling of 4 Head Race Tunnels

(HRT), butterfly valve chamber, penstock, penstock assembly chamber, machine hall, bus duct

galleries, draft tubes, upper and lower expansion chambers, Tail Race Tunnels (TRT), lightings,

etc.

The work of power house has been carri ed out through various approach ADITS provided at

different levels.

The features of power house exertion are:

1. INTAKE STRUCTURE : The 4 HRT`s, finished diameter of 8.5 m., circular with total length

of approx. 3.66 Km., 2 for Tehri HPP and 2 for Tehri PSP is provided with a conventional

semi circular type intake structure with trash racks to avoid entry of trash into the

turbines. For smooth flow of water and to reduce hydraulic losses, Bell mouth 15

m.X15m. section which converts into 8.5 m dia circular section in a length of 26 m have

been provided at the entry of Tunnel.

For maintenance of the HRT's, 4 numbers, 11 m. dia gate shaft have been provided.

Fixed wheel gates of size 5 m.X11 m. shall be provided in each Tunnel at a distance of

about 115 m. from the Intake. These gates shall be operated by independent rope drum

hoists located at EL 840 m.

HRT-1 & 2 bifurcates into 4 numbers, pressure shafts each of dia 5.75 m. diameter. The

pressure shafts will have a vertical drop of nearly 120 m. and horizontal portion of 55 to

152 m. before entering the Power House. The entire portion of pressure shafts from

bifurcation to Power House is steel lined with ASTM-A 717 Gr-F steel with external

stiffness.


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2. Butterfly Valve House

Butterfly Valve Chamber 121 m. long, 10m. wide and 24 m. high has been constructed to house

4 numbers each 5 m. dia Butterfly Valves before entry to the pressure shaft. Butterfly ValveChamber involved underground excavation to the tune of 31 Th. cum. and concreting of 5.28

Th. cum. and the same stands completed.

3. Penstock Assembly Chamber

Penstock Assembly Chamber 117 m. long, 13 m. wide and 19 m. high has been completed. The

Penstock Assembly Chamber involving underground excavation of 30 Th. cum. and concreting

quantity of 5 Th. cum. has been completed.

4. Power House Cavern

The Power House Cavern, 197 m. long, 24 m. wide and 63 m. high, which includes Service Bay,

Control Room, Auxiliary rooms, housing 4 units of 250 MW each with vertical shaft Frances

Turbine completed to the Generators having rotational speed of around 214 rpm. The heaviest

single assembly of Generator Rotor having 700T weight has been erected by 2 numbers EOT

cranes each of 375 T capacity working in tandem with a lifting beam.

Figure 8. View of intake of HRT


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5. Tail Race Tunnels (TRTs):

There are two TRTs each of diameter 9m and each carrying discharge from two units. TRTs 1 &

2 discharge the water from HPP Units and TRTs 3 & 4 will discharges from PSP Units. Tunnels

are of length 703m and 770m respectively.

6. Diversion Tunnels:

There are four diversion tunnels each of 11m in diameter, horse-shoe shaped; have been

constructed for diversion of water during construction period. Finally these are used as shaft

spillways.

7. Access and other Miscellaneous Tunnels:

ADIT-3 provides access to the Power House and Transformer Caverns and ADIT-1 to Penstock

Assembly Chamber and Butterfly Valve Chamber. Separate ventilation and bus duct tunnels

have been constructed. Most of the tunnels have been constructed of D-shape. Number of

access tunnels has also been excavated to facilitate construction activities at different locations


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2.3 GENERATOR

In the generating power station there are four generating units, each of capacity of 250MW

producing a total power of 1000MW at Rated Head. These hydro-generators connected ingenerating stations are servo-generators installed by the Soviets in the year 1989 which are the

production of Uraelectrotiazchmach, at Yekaterinburg which was a Russian -Ukrainian

company.

Stator:

The stator winding of the hydro-generator consists of 696 rebel bars made of high quality

cooper (Cu) which are divided into 396 slots each and each of them are provided with

insulations between two bars with insulating primer, Bectol.

Rotor:

Rotor of hydro-generator consists of 14 arms fastened to rotor hub, thrust bearing hub and

shaft-extension with shrunk upper guide bearing hub, spider, stacked rim and 28 poles. The

baffles are fastened in upper and lower parts of the rotor arm. They provide cooling air inletinto rotor spider. Rotor rim is assembled of segments stamped of steel of 4mm thick and it

should be tightly wedged on rotor spider.

Poles:

There are 28 poles in a generator set, each of them are of 12 feet in height. Pole cores are

assembled of punched steel sheets of 2mm thick. The sheets have insulating coating in order to

decrease the losses. The core is pressed by steel pole end plates with pressing studs. The turn-

to-turn insulation is done by Glass Tape with Epoxy binding agents (F-Class).

Braking System:

When the hydro-generator is disconnected from the grid, turbine wicket gate is closed and

rotational speed is reduced down to 50% of rated value, short circuiting of main terminals of

stator winding and current supply into rotor winding from braking thyristor convertor occurs.

When rotational speed is reduced down to 5% of rated value, the mechanical braking is


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automatically switched on. In case of electric braking failure or electrical damage of generator,

the mechanical braking is automatically switched on when rotational speed 5% rated speed.

There are 24 pneumatic brake Pads provided to endow with mechanical braking installed under

rotor rim and operated by compressed air flow with 0.8MPa pressure.

Generation Process:

For generating the electricity, firstly the stator winding is formed with two opposed magnetic

poles and the first and second magnetic paths are juxtaposed to each other. An output coil and

a first exciting coil are wound on the first magnetic path in such a manner as to produce

respective electromagnetic forces in the same phase. A second exciting coil wound on second

magnetic path in such a manner as to produce an e.m.f produced by first exciting coil the first

and second coils supply exciting current to a field coil wound on a rotor arranged between the

opposed magnetic poles during rotation of the rotor. Hence, the rotor is provided with a D.C.

excitation drawn from the output to maintain the rotor field current corresponding to the

desired output power generated. For the rated output power of 250MW the rotor current

should be 1600A. Each generator produces 15.75kV which is fed to the Thyristor Control Cubicle

after stepping down to 420V to control the excitation current by varying the firing angle. The

generated voltage is fed to a Step-up transformer which converts the 15.75kV to 420kV which

is then sent to Gas Insulated Switchgear (GIS) for the protection of the live bus bars and then it

is directly distributed through distribution system.

Figure 9. A View of Generator [Machine Hall]


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Specification of the Generator:

Name of the Machine : Turboatom

Manufacturer : UraelectrotiazchmachManufactured at : Yekaterinburg

Type : CB870/300-28

No. of Poles : 28

Insulation : Glass Textolite (F Class)

Phases : 3-

Frequency : 50Hz

Rated Output : 278MVA / 250.2MW

Maximum Continuous Output : 305.8MVA / 275MW

Power Factor : 0.9

Rated Voltage : 15.75kV

Rated Current of Stator : 10190.7A

Rated Voltage of Rotor under Rated Load : 715A

Rated Current of Rotor under Rated Load : 1600ARotational Speed- Rated : 214.29rpm

Runaway : 410rpm

Direction of Rotation : Anti-Clockwise

Voltage rise after 100% load rejection with p.f. =0.9 : 28V

Efficiency under rated load with p.f. =0.9 : 98.18%

Maximum erection weight : 670T


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2.4 TURBINE

The Tehri HPP is equipped with four vertical Francis Turbine each of 255MW capacity. The

Turbine and its auxiliaries have been manufactured in Ukraine and are supplied by PowerMachines, Moscow. Each turbine can be operated in the head range of 122.6m-230.1m. The

unique feature of design of these Francis Turbine is that, a single runner capable of operation

under large head variation of over 100m.

Construction:

The spiral case is fabricated of high strength steel

plates. The stay ring is equipped with 19 profiled

stay vanes (including tooth). The stay vanes are

arranged uniformly on the circular stay ring in

18. These vanes form 3 groups of vanes having

various profiles and tooth. The arrangement

diameter of the stay vane inlet edges is 7100mm

and outlet is 5850mm. The stay rings and stay

vanes are made from high strength cast steel.

The draft tube is of elbow type which is made of

welded steel and embedded into the concrete. It

has a provision of pipe connection for depressing

water during condenser mode operation.

The distributor is of cylindrical type, equipped with 20 guide vanes of symmetric profile withheight H o= 656mm arranged on a circular diameter of 5100mm. Guide vane is carried by 3

bearings Upper, Medium and Lower which are made from composite material providing

operation without lubrication. The ring is made of polymeric material installed on Bearing

Housing and takes the axial force from weight of the vane and operation mechanism.

The double protection is provided for each Guide Vane. This protection limits its moving during

the pin shearing and prevents impact against the adjacent vane.

Figure 10. View of Frances Turbine


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1. Safety friction gear

2. Stop set on the lever and contacting the adjacent lever in case of the vane turn up to the

position exceeding the maximum distributor opening or when the vane tends to pass

through the position corresponding to the closed distributor.

Working:

Water enters through penstock through MIV then to wicket gates. Wicket gate reregulating

mechanism controls the flow of water with change in load. It consists of 20 wicket gates

connected to an operating ring with levers and links. We can regulate the flow of water through

wicket gates by governing system which controls the opening and closing of wicket gates. The

governing system is being operated by two Servomotors and Oil Pressure units which regulate

the opening by regulating the pressure. The opening of MIV is also regulated as wicket gates by

oil pressure unit and servo motor system. Water enters into the runner and runner rotates due

to which the rotor of generator starts rotating.

Specification of Turbine:

Manufacturer : Power Machines

Manufactured at : Ukraine

Runner Diameter : 4100

Net Head- Maximum : 230.1m

Rated : 188m

Minimum : 122.6m

Rated Output- Nominal : 255MW

Maximum at 205


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Head Height VS Power Output:

2.5 TRANSFORMER

In Tehri HPP, a 3- transformer is used which is installed in close proximity of machine hall.

The transformers are housed in Transformer Hall cavern which is parallel to the machine hall

which is parallel to the machine hall of underground power house. The transformers used

have been supplied and erected by the BHEL Bhopal. The type of transformer used is oil filled

3-, double winding.

Working:

The transformer is solidly grounded neutral. The high voltage Bushings are connected to the

420kV SF6 Bus ducts, while low voltage terminals are connected to 15.75kV isolated phase Bus

Duct. Transformer steps up the 15.75kV to 420kV and supplies to Bus duct. The transformer

employs OFWF cooling system consisting of two oil coolers (one main and one stand-by). In

order to safe guard the oil coolers from silt etc. in the cooling water, the double loop watercooling arrangement has been provided. The conservator is mounted above the tank cover.

The transformers are being provided with both protections from internal as well as external

faults. Buchholz relay protects the transformer from internal faults and all necessary relays

are provided to protect transformers against possible external faults.

Head Min. Power Max. Power

112.6m 82MW 115MW

188m 153MW 255MW

205m 153MW 280MW

230.1m 169MW 280MW

Table 4. Power output on different Heads


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Specification of the Transformer:

Manufacturer : BHEL

Manufactured at : BhopalType of Cooling : OFWF

Insulation : Glass Textolite (F Class)

Phases : 3-

Frequency : 50Hz

No Load Voltage- HV : 420kV

LV : 15.75kV

No Load Current- HV : 420.6A

LV : 11217.1A

Turns Ratio : 1: 26.67

Temperature rise of Oil : 40C

Temperature rise of Winding : 53C

2.6 GAS INSULATED SWITCHGEAR [GIS]

The HPP has an underground 420kV SF 6 Gas Insulated Switchgear (GIS) and Gas Insulated Bus

Ducts (GIB) due to non-availability of space for open switchyard, compact layout of

underground power house, safe operation and very low operating cost. The execution of

underground 420kV SF 6 GIS and GIB has been done on turnkey basis from SIEMENS AG,

Germany. There are 7 bays of 420kV gas insulated switchgear and associated equipment has

been installed at EL 618m. Two circuits of 420kV GIB have been extended to the port yard

from where two 420kV overhead lines of length 182 and 186Km each are taking off to Meerut

sub-station for evacuation of above power.


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Working:

420kV GIS and associated equipment located indoor is designed as GIS-I and GIS-II. Twocircuits of GIB have been laid in 800m long tunnel which is connected with GIS-I at one end at

GIS hall and other end with GIS-II at end of bus duct tunnel at Interface Facility Area. The GIS

consists of circuit breakers, current transformers, potential transformers, disconnecting

switches, grounding switches, lighting arrestors etc. Two circuits of GIB, installed in a naturally

ventilated tunnel are connecting the 420kV GIS-I located at EL 618m in the floor above

transformer hall and GIS-II located near the tunnel exit to the outside area.

Figure 11. A View of Gas Insulated Switch Gear


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2.8 OPERATION AND MAINTENANCE

Gates and Hoists:

Following is the list of important checks which should be carried out for trouble free operation

of gates:

1. Seal and Seal Seat inspection before operation for leakages.

2. Regular greasing of wire ropes with cardium compound.

3. Check functioning of brakes.

4. Check soundness of welds.

5. Check for all gears and pinions for uneven wear and tear. Adjust for proper contact.

6. Raise and lower the gate at a regular interval by hoist & check for smooth and trouble freeoperation of gate without excessive vibration.

7. Lubricate all bearings, bushings, pins, linkages etc.

8. Timely maintenance of Gates & Hoists and trash racks etc.

9. Check the healthiness of control & protection for isolation gates/valves & for cranes/hoists.

10. Check the Communication systems, availability of power supply for emergency operations,

approach roads etc., being maintained regularly.

Electromechanical Equipment Maintenance:

a) TURBINE AND ITS AUXILIARIES:

The Francis Turbine is always immersed in water but its inspection should be done as

recommended by manufacturer without any compromise. Due to Cavitations, there may be

huge damages to runner causing adverse effect on performance and efficiency. Periodical

maintenance of Governor along with all associated mechanical, electrical and electronic

components is to be carried out. The control circuit should be neatly dressed with proper

identification clear marks. The electronic components and cards should be carefully maintained

at appropriate temperature level to achieve desired performance. Periodical calibration and

testing of transducers, meters, etc. should be carried out. Desired purity level of hydraulic oil is

required to be maintained to give trouble free operations. Following activities broadly covers

the maintenance activities to be done in Turbine & Governor:


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Turbine:

1. Periodic NDT viz. Ultrasonic, etc.

2. Polishing of the turbines once in a year to minimize the white pitting.

3. Inspection and testing of the runners from experts to decide residual life so as initiateprocurement of runners for replacement.

4. Inspection of labyrinth seals in case of reaction turbines.

5. Internal runner housing painting with anti-corrosive/tar based paints.

6. Applying anti-erosive coatings to the runner.

Governor:

1. Purification of hydraulic oils by centrifugal as well as electrostatic liquid cleaner.

2. Periodic maintenance of the servo valves and motors. Inspection of the pistons and

housings of the servo valves and motors to check for worn-out.

b) GENERATOR AND ITS AUXILIARIES:

Stator and rotor winding, bearings and excitation system are main electrical parts of generating

plant. As regards stator and rotor winding, regular recording of its IR (Insulation Resistance)

values at fixed intervals are maintained. Tan Delta test of stator winding indicate the

status/condition of stator winding insulation.

Likewise impedance test (voltage drop test across each pole) indicates condition of the rotor

winding. Proper cooling system is maintained to limit rise in stator winding temperatures and

consequently increase the life of stator winding. Inspection of the stator winding to verify its

firmness in stator core slots and healthiness overhang portion with firm end winding caps. End

spacers, slot wedges are checked for healthiness. Windings are varnished to enhance its life.

Looseness of stator core or inter lamination, core insulation are factors directly affecting

winding heating due to eddy current loss. Thus recommended maintenance as per schedule is

done and its records are maintained and corrective actions are taken, if necessary.


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1. Periodic checking of the foundations and tightening of the bolts. Filling the foundations with

epoxy.

2. Checking the vibration periodically. History of the recorded readings gives guidelines for

realignment, looseness if any, unbalanced electrical components, increase in bearing gaps,coupling misalignment, uneven stator-rotor air gap, etc.

3. Periodic cleaning or replacement of the generator air coolers and bearing oil coolers to

improve performance of the generator.

4. Primary and secondary testing of the protection system for its healthiness and correct

operation.

5. Inspection of the CTs, PTs and bus bars for overheating, temperature rise etc.

6. Inspection of protection controls circuits and mock trials of the fire fighting system alongwith evacuation system. Checking of the CO 2 cylinders and replenish as per

recommendations of OEM.

c) TRANSFORMER AND SWITCHYARD:

Following works are required to be carried out foe proper up keeping of transformer and

switchyard:

1. Continuous monitoring of oil and winding temperatures.

2. Periodic oil filtration.

3. Oil testing for various tests and Dissolved Gas Analysis.

4. Tan Delta and Megger test as per schedule.

5. Oil cooling cleaning and replacement.

6. Testing protection system for healthiness.

7. Firefighting system, CO 2 and emulsifier checking, maintenance and inspection, mock trials.

8. Breaker time test.

9. Operating and testing of isolator opening and closing.

10. Control circuit checking and healthiness of operating system of the breaker.


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CHAPTER 3

RESULTS AND DISCUSSIONEven though there are many hydro power plants in India, the power generation from Tehri dam

plays an important role in power production. The dam situated on the river Bhagirathi has a

capacity of 2.6 km3 with surface area of 52km2. The dam is earth and rock fill dam. The height

of dam is 260m and has length of 595m. The constructional cost is US$ 1 billion. The project

was the initiative from the govt of Uttar Pradesh and was later on also supported and funded

by govt of India in collaboration with USSR. The Tehri Dam and the Tehri Pumped Storage

Hydroelectric Power Plant are part of the Tehri Hydropower Complex which also includes the

400 MW Koteshwar Dam downstream. The dam can withstand an earthquake of 8.4

magnitudes on Richter scale. The HPP has 4 turbines each of 250 MW capacity. The water from

the reservoir enters the HRTs and then through the butterfly valve it enters the Powerhouse

where turbines have been installed where power generation takes place. There after water

joins the mainstream with the help of TRTs.


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CHAPTER 4

CONCLUSIONThe Tehri Dam is a multi-purpose rock and earth-fill embankment dam on the Bhagirathi River

near Tehri in Uttarakhand, India. It is the primary dam of the Tehri Hydro Development

Corporation Ltd. and the Tehri hydroelectric complex. Phase 1 was completed in 2006, the Tehri

Dam withholds a reservoir for irrigation, municipal water supply and the generation of 1,000

MW of hydroelectricity. Two more phases with an additional 400 MW and 1,000MW pumped

storage hydroelectricity are under construction. This dam is Asias largest & world s 3rd largest

rockfill dam. The complex will afford irrigation to an area of 270,000 hectares (670,000 acres),

irrigation stabilization to an area of 600,000 hectares (1,500,000 acres), and a supply of 270

million gallons of drinking water per day to the industrialized areas of Delhi, Uttar Pradesh and

Uttarakhand.

The purpose of the report is analyzing the various aspects of the powerhouse. This includes

studying the process of power production in the powerhouse, familiarizing with the various

components of the powerhouse such as turbines, generators, transformers and control

systems.

For data collection personal observation of the powerhouse was done. Some data was collected

from the internet as well as from the engineers & managers currently working in the company.

Scope is limited to gathering the information and knowing the working of the various

components of the powerhouse.


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REFERENCES

1. www.thdc.com

2. Gangaavtaran Official Magazine THDCIL

3. BOOK- Towards Powering India-2007 , Author- R.V.Sahi
http://www.thdc.com/http://www.thdc.com/http://www.thdc.com/http://www.thdc.com/


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DATA SHEET

Technical specification for Draft tube Gate and Embedded Parts

Type of gate : Sliding type Size of gate : 6.7 8.5 M No. Of gate : 4 No. Of elements per gate : 3 Nos. Sill level : EL 577 M Sliding track centre to centre : 7.4 M Sill to top seal centre : 8.6 M Weight : 46 MT

Design Head : 35.5 M Sealing Arrangement : D/S (Side, Bottom & Top rubber

seal)

Technical specification for Draft tube Hoist

1. Hoist capacity : 35 T

2. No. Of rope drums : 2 Nos.3. Max lift of gate : 64 M4. Speed

Hoist : 1.5 M/MinLong travel : 8 M/Min

5. MotorHoist : 20 HP, 965 RPM, Squirrel cageLong travel : 1.7 HP, 700 RPM, S Cage

6. BrakeHoist : 300 mm dia, single phase 415 VLong travel :150 mm dia, single phase, braking

torque 6.5 kgm.


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Technical specification for TRT 1& 2 Gate and Embedded Parts

Type of gate : Sliding type Size of gate : 11 M 15.5 M

No. Of sets : 2 No. Of units per sets : 10 Nos. Sill level : EL 598 M Weight : 97 MT Design Head : 14.5 M Sealing Arrangement : D/S (Side, Bottom rubber seal)

Technical specification for TRT 1&2 Hoist

Type of hoist : Winch machineHoist Capacity :10 tonOperating speed :1m/min.Motor :15 HP, 720 rpm,3 phase, 400-440

V 50cycles/sec Squirrel cage motor

Brake :300 dia. EM brake, Single phase,torque capacity38kgM

Technical specification for T1&T 2 Gate and Embedded Parts

Type of gate : Sliding type Size of gate : 11 M 17.5 M No. Of sets : 1 No. Of units per sets : 11 Nos. Sill level : EL 5986M Weight : 110 MT Design Head : 16.5 M Sealing Arrangement : D/S (Side, Bottom rubber seal)


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Technical specification for T1&T2 Hoist

Type of hoist : Winch machine

Hoist Capacity :10 tonOperating speed :1m/min.Motor :15 HP, 720 rpm,3 phase, 400-440

V 50cycles/sec Squirrel cage motorBrake :300 dia. EM brake, Single phase,

torque capacity38kgM

Technical specification for T3&T4 Gate and Embedded Parts

Type of gate : Sliding type Size of gate : 11 M 14.6 M No. Of sets : 1 No. Of units per sets : 7 Nos. Sill level : EL 600 M Weight : 110 MT Design Head : 12.5 M Sealing Arrangement : D/S (Side, Bottom rubber seal)

Technical specification for T3&T4 Hoist

Type of hoist : Winch machineHoist Capacity :10 tonOperating speed :1m/min.

Motor :15 HP, 720 rpm,3 phase, 400-440V 50cycles/sec Squirrel cage motor

Brake :300 dia. EM brake, Single phase,torque capacity38kgM

tehri hydro development corporation india limited

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