Yogesh 8th sem project report

Rayat Institute of Engineering and Information TechnologyRailmajra, INDIA

GENERATION OF ELECTRICITY THROUGH HYDRO POWER AND MAINTENANCE OF POWER HOUSE

REPORT  

 SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FORSix Month Industrial Training

at  

SJVNL, Jakhri( 19-01-2016 to 19-04-2016 )

 SUBMITTED BY 

Yogesh Thakur Mechanical Engineering

1248936

Mechanical Engineering Department

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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

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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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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 ThakurDate:

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Contents

Sr. No.

Title Page No.

123

4567891011121314151617

Introduction to SJVNLNathpa Jakhri Project , Salient FeaturesOther 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

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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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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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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 betweenSJVN 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).

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.

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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 CommissionedUnit-I 18 May ,2004Unit-II 06 May, 2004Unit-III 31 March , 2004

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Unit-IV 30 March , 2004Unit-V 06 Oct. , 2003Unit-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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PROJECT STATISTICS

DESCRIPTION AS PER REVISED COST EXTIMATE

Location:State:District:Vicinity

Diversion Dam:TypeMax. height above foundation levelFull reservoir levelMax. water levelMin. draw down levelDisilting Arrangement :TypeNumber & size

Flow through velocityParticle size to be removedHead Race Tunnel:Shape & typeDiameterSurge Shaft:TypeDiameter

Total heightPressure Shafts:Type

NumberMain tunnels

Power House:TypeSizeType of turbineGross headDesign headNumber and capacity of generating units

Himachal PradeshKinnaur/ShimlaDam down stream of wangtoo bridge at Nathpa & power house near Jhakri village on left bank of river sutlej.

Concrete gravity62.5m

1495.50m1497.50m1474.00m

UndergroundFour parallel chambers each 525m x 16.31m x 27.5m33.0 cm/sec.Particle greater than 0.2 mm

Circular, concrete lined10.15m

Restricted office21.6m 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 units4.9m & approx. 572m to 622m & 623m length.

Underground222m x 2om x49mVertical axis Francis turbine486m428m

6 x 250 MW

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Tail Race Tunnel:SizeLengthPower Potential:Energy generation in a mean yearEnergy generation in a dependable year

10.15m, circular982m

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.

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.

Fig1: Block diagram for power station

TURBINE:

The Turbine used here is the “ VERTICAL FRANCIS TURBINE ” means therotating 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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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.

o Runner:

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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 theturbine 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 oilscraper 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 astrong 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 thecylinder section and cover the vertical with a layer of oil. The thickness of this layerwill 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 film of oil follow with the shaft in the wedge shaped entrance on the bearing shell and builds up the guiding oil layer.

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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. Itserves 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 servomotorand 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 towards the guide apparatus with the least possible loss. The spairal casing has been fitted with outlets for index measurements and a

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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 witha 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 theupper 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 sealduring 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 strainer particles above 200 micron is removed. The system will automatically be put into operation during start and stop of the unit.

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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

MIV fully Open

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Guide Apparatus :

The Governors action on the two main servomotors is transferred via rodconnections to the regulating ring . The actual guide apparatus consists of23 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 linksare 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.

% open

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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.

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

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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 generatorhousing 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 , nonaging 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, condensationon 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

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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 andThrust 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 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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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 mRated output 250 MW Rated Output (Generator) 278 MVAPower Factor 0.9 Terminal Voltage 15.75 KVManufactured 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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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 brakeassembly 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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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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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.

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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 waterlevel 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 toreduce 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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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 oilFrom deterioration and protect the transformer against failure on account of badQuality of oil.

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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 secondaryside 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 forthe 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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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 duringmaintenance 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 ofgeological features were adopted for the support system. A complete analysis of various stages of excavation was carried out through numerical modeling and

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

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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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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.

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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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