CONTENTS I) preface II) Acknowledgement 1) About the NHPC 2) About the project 3) Water ways 4) Turbine a) Description b) Use of material 5) Governor a) Principle b) Out lines of governor c) Construction d) Description 6) Station auxiliaries a) Compressed air system b) Drainage and Dewatering system c) Cooling water system d) Isolating oil handling system 7) Generator 8) Excitation system of generator 9) Compressor a) Construction b) Principle and working c) Salient features of screw compressor 10) Transformer 11) Specification of the equipments used a) Transformers b) Generator unit c) Hydro-electric governor d) Compressor e) Turbine f) Other equipments Page 1 of 42
Transcript
CONTENTSI) prefaceII) Acknowledgement1) About the NHPC2) About the project3) Water ways4) Turbinea) Description b) Use of material 5) Governora) Principleb) Out lines of governorc) Constructiond) Description6) Station auxiliariesa) Compressed air systemb) Drainage and Dewatering system c) Cooling water systemd) Isolating oil handling system7) Generator8) Excitation system of generator9) Compressora) Constructionb) Principle and workingc) Salient features of screw compressor10) Transformer11) Specification of the equipments useda) Transformersb) Generator unitc) Hydro-electric governord) Compressore) Turbinef) Other equipments
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ABOUT THE NHPC-
National Hydroelectric power corporation was set up in year 1975 as a private ltd. company with an authorized capital of Rs 2000millions. In year 1986 it becomes a public ltd. company. In its existence of over 25 years NHPC has become single largest organization for hydropower generation in India, with capabilities to undertake all the activities from conceptualization to commissioning in relation to setting up of hydroelectric project.
NHPC is an enterprise of Government of India with an authorized share capital of Rs 70,000 millions with an investment of Rs 1,35,000 millions and paid up capital of Rs 57,188 millions. NHPC is amongst top ten companies in the country in terms of investment. NHPC has been granted ISO-9001 certificate for its quality system.
ABOUT THE PROJECT This project was started by NHPC in year 1993. The proposed power generation for the project was 120MW, but due to some unavoidable reasons the project is generating only 31.4*3MW. Out of which 132KV electricity is supplied to NEPAL and remaining is supplied to CB Ganj (Bareilly). The power house of the project consists of three units for power generation.The salient features of the project are as follows-
A) LOCATION
a) State Uttaranchalb) Distt Champawatc) River Sardad) Barrage 2KM D/S of Tanakpur towne) Power house Right U/S of east Banbassa
barrage B) HYDROLOGY
a) Catchment area 15100sqKMb) Snow Catchment 1470sqKMc) Design flood 19900 Cumecsd) Mean annual rainfall 1500mm
C) BARRAGE
a) Length 475.3Mb) Spillway bays length 279.5Mc) No. of bays 22Nos.d) Thickness of piers 3.3Me) Max. discharge capacity 19900Cumecsf) Crest level of u/sluices 237.5Mg) Crest level of spillway bay 238.1Mh) Max. barrage pond level 246.7
i) Energy dissipation arrangement- Hydraulic jump in stilling basin with end sillsj) Afflux bund lengths Left 2.2KM Right 2.188KM
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D) SLIT EXCLUDER TUNNELS
a) Number 6Nos.b) Size 2.2 * 3.2M
E) HEAD REGULATOR
a) Location Right bank of riverb) No. of bays 6Nos.c) Length 78.45Md) Width of bays 11.2Me) Size of gates 11.2*5.5Mf) Discharge capacity 680 Cumecs
F) SLIT EJECTOR
a) Type Hopper Typeb) Size of desilting basin 90*120Mc) No. and size of hopper 48Nos. 15*15 Mtr each
d) No of flushing tunnels 4Nos.
G) POWER CHANNEL
a) Length 6.4 KM (from H/R to Forebay) b) Full supply depth 6.14 to 9.0M c) Shape Trapezoidal d) Side slope 175H:1V e) Max. discharge capacity 566 Cumecs f) Bed slope 1:8300 to 1:10500
H) FOR BAY a) Size of for bay 91.0 M*64.2M b) Full supply level 245.48 M c) Bed level 231.10 M
I) BYE PASS SPILL WAY
a) Length of spillway 59.5 M b) No and size of bay 5 nos of 9.5 M each c) Max discharge capacity 566 Cumecs d) Crest level 243.2 MPage 4 of 39
J) PENSTOCKS a) No 3 b) Diameter 6.5 M c) Length 68 M d) Size of intake gate 5.1*7.1 M e) Centre line of intake 234.933 m K) POWERHOUSE
a) Type surface b) Head 22 M c) Designed 24.25 M d) Dimensions 102.32*45.20*47.7 M
e) Installed capacity 120 MW(3 unit of 40 MW each) f) Design discharge per unit 188.67 Cumecs
L) TAIL RACE CHANNEL a) Length 1150 M b) Max water level 223.3 M c) Min water level 222.0 M d) Bed level at beginning 218.853 M e) Bed level at regulator 218.848 M f) Bed slope 1:8600 g) Bed width 96 M h) Side slope 1.5 H :1V
i) Full supply 4.45 M
M) TAIL RACE REGULATOR
a) Length 119.9 m b) No and width of bays 80 no* 12.8 M each c) Crest level 218.848 M d) D/S guide bunds left right Length 77.0 M 177.0M Type of carriage way restressed conc. Bridge Size of spill gates 18.3 M * 8.9 M Type of gates fixed wheel vertical lift
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N) LENGTH OF POWER CHANNEL
PACKAGE FROM RD TO RD I 1437.00 2637.00 II 2637.00 4032.00 III 4032.00 5200.00 IV 5200.00 6400.00
Main components of plant are-a) Storage reservoir b) Dam with its control workc) Waterways with its control workd) Power house with turbo and other machinerye) Tail racef) Generation and transmission of electric power.
WATERWAYS Waterway is a passage through which water is carried from storage reservoir to the power house. It consists of the following-
1) FOREBAY- It is an enlarged section of canal spread out to accommodate requirement width of the intake. Its function is to store temporarily the water rejected by the plant when its load is reduced and to meet the instantaneous increased demand of water due to sudden increase in load.
2) PENSTOCK- These are pipes of large diameter carrying water under pressure from storage reservoir to the turbine. Penstock are subjected to water hammer pressure due to fluctuating turbine load. Trashracks are provided at the inlet of penstock in order to obstruct the debris entering in it. Penstock gates are provided to store the supply of water when not required.
3) TAILRACE- It is a waterway used for discharge of water, which is coming out of the turbine. It is either connected to storage reservoir or to the river.TURBINE
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It is a device which converts the pressure energy into the kinetic energy which is used for the production of rotary motion of the shaft, which inturn is used for generation of electricity.
The turbines used here are vertical shaft Kaplan turbines. Kaplan turbine is named in honour of Dr. Victon Kaplan of Germany.It is an axial flow turbine.
Reaction turbine requires low head and high rate of flow. Reaction turbine operates with its wheel submersed in water. The water before entering the turbine has pressure as well as kinetic energy. All the pressure energy is not transformed into kinetic energy. The moment on the wheel is produced by both kinetic and pressure energies. The water leaving the turbine has some of the pressure as well as kinetic energy. The pressure at inlet of turbine is much higher then the pressure at the outlet. Main components of a Kaplan turbine are as follows-
a) PENSTOCK
b) RUNNER- Kaplan turbine is a propeller turbine in which runner blades are made adjustable. Number of blades used varies from 3 to 6 in number. This reduces the contact surface with water and hence the frictional losses. The blades are attached to the hub, dispensing with the bend, thus eliminates the frictional losses due to reduced contact surface. The blades can be adjusted by means of servomotor mechanism operating inside the hollow coupling of the turbine and the generator shaft. Servomotor mechanism consists of a cylinder with a piston working under oil pressure on the either side. The piston is connected to upper end of regulating rod or blade operating rod, the up and down movement of which turns the blades. Regulating rod passes through turbine mainshaft which is made hollow for this purpose. Movement of this rod is controlled by governor.c) SPIRAL CASING / SCROLL CASING- To avoid the loss of efficiency, the flow of water from the penstock to the runner should be such that it will not form eddies. In order to distribute the water around the guide rings equally, the spiral casing is designed with cross-sectional area reducing uniformly around the circumference, maximum at the entrance and nearly zero at the tip. This gives a spiral shape to the casing. This position of inlet to spiral casing depends on direction of water flowing out of penstock which may vary according to the site.
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d) GUIDE MECHANISM- Guide vanes or wicket gates are fixed between two rings in form of a wheel, known as guide wheel. Guide vanes have aerofoil cross-section. This cross-section allows water to pass over them smoothly and with minimum frictional losses. Each guide vane is rotated about its pivot Centre which is connected to the regulating rings by means of a link. The ring is connected to regulating shaft by means of regulating rods, generally two in number. By rotating the regulating shaft the guide vanes can be closed or opened thus allowing a variable quantity of water according to the need.The regulating shaft is operated by means of governor whose function is to keep the speed of turbine constant at varying loads. The guide vanes are made up of cast iron.
e) DRAFT TUBE- The water after striking the runner passes on to the tail race through a draft tube which is welded steel plate pipe or concrete tunnel. Its cross-section gradually increases towards the outlet. The draft tube is a conduit which connects the runner exit to the tailrace. The function of draft tube are as follows-
1) If the water is discharged freely from the turbine, then the turbine will work under a head equal to the height of head tail race water level above the runner outlet. If air tight draft tube connects the runner to the tail race, workable head will increase by an amount equal to the height of runner outlet above the tail race. The draft tube will thus permit a –ve head to be established at the runner outlet. Thus making it possible to install the turbine above the tail race without the loss of head.
2) The water leaving the runner still posses a high velocity and its kinetic energy would be lost if it is discharged freely. By employing a draft tube of increasing cross-section, the enclosed conduit is extended up to the outlet end of the tube and discharge takes place at a much reduced velocity and thus resulting in gain of pressure head. This increases a –ve pressure head at turbine runner exit with which net working head on turbine increases, which results in increase in output i.e efficiency of turbine.
MATERIAL USED- Cast iron is less resistant to cavitation. Therefore cast steel is better than cast iron. In case of cast steel parts the parts affected by cavitation can be repaired by welding. Stainless steel is the best material to avoid cavitation but, it is expensive. Therefore turbine Page 8 of 39
runner are made of cast steel and are coated with stainless steel. Bronze is also used and is more resistant then the cast steel.
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STATION AUXILIARIES1) COMPRESSED AIR SYSTEM
1.1) H.P AIR SYSTEM –
H.P air system consists of two H.P compressor motor sets (88MBA) and (88MBB). The H.P compressors are three stage compressors with air cooled intercoolers between the stages and after coolers integrated with the compressor.
Air from compressor passes through non return valve(202), isolating valve(203), air receiver isolating valve(228) and finally to H.P air receiver (207). The two compressors are air cooled. Condensate drains have been provided on after coolers and on H.P air receiver isolating valves(203) and (228).The air receiver has pressure gauge(211) and safety valve(210).
1.1.2) START STOP CONTROL-
Pressure switch (63A-1) starts the compressor(88MBA) when the pressure in air receiver drops to 37KG/sqCM and stops the compressor at 45KG/sqCM. Pressure switch963A-2) starts compressor(88MBB) at pressure 35KG/sqCM and stops at 45KG/sqCM. Pressure switch(63-A3) is set to give alarm at 32KG/sqCM. The safety valve operates at 50KG/sqCM.
MECHANICAL DEVICES-201- aircompressor motor operated 202- non return valve203- isolating valve204- air cooled after cooler integral with compressor205- isolating valve206- isolating valve for pressure switches207- high pressure air receiver208- isolating valve on 207 for moisture drainage210- safety valve on 207 211- pressure gauge with cock on 207212- isolating valve on 213213- pressure reducer
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214- low pressure in receiver215- isolating valve on 214 for drainage217- pressure gauge with cock218- safety valve219- isolating valve222- filter on H.P air line223- isolating line on air supply line to brakes225- filter on L.P air line 227- stop valve for comp. air pressure switches231- moisture trap 232- isolating valve for moisture trap240- isolating valve in L.P line for shaft seal & air admission at partial load
ELECTRICAL DEVICES-
63 A-1 pressure switch for main compressor start/stop63A-2 pressure switch for aux. Compressor start/stop63A-3 low pressure alarm switch88MBA- air compressor main motor88MBB- air compressor aux. motor
2) DRAINAGE AND DEWATERING SYSTEM
2.1) DEWATERING SYSTEM-
To drain various leakage and seepage in generating units as well as in power house, a drainage system has been provided for each unit.
The system consists of drainage pit located near unit no-3 on which two vertical turbine pumps (825) driven by motors (88MD-E) and (88MD-F), and one submersible pump motor set with strainer(825A) is provided in the pit.
The discharge from three pumps is connected to a 300M diameter header via non return valve(827) and isolating valve (828)
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and is led to tail race. Level switches (71W-4e,f,g)and (71W-5) and (71W-6) are operated manually by push buttons.
As the level rises to some preset value the level switch(71W-4e) operates to start the drainage pump motor(88MD-E) and level switch(71W-5) operates to stop the motor when the level falls to particular value. However if the level further rises, level switch (71W-4f) operates to start the standby pump motor(88MD-F). Level Switch(71W-5)is meant for stopping standby motor.
A level switch (71W-6) is provided for alarm in case the water level continues to rise and reaches a preset high value.
2.2) DEWATERING SYSTEM-
To remove water from turbine water passage via a dewatering header passing through a dry pit to the river through a header pipe a drainage system has been provided for each unit.
Dewatering pit is located near unit no-3 and has four oil lubricated vertical turbine pumps sets(801) with motors (88MDA), (88MDB), (88MDC), (88MDD). All the four vertical turbine pumps are directly mounted on 700mm dia header pipe through strainers(817).
The discharge from all the four pumps is connected to a 700mm dia header via non return valve(803) and isolating valve(804) and is led to tail race. Pressure switches 6W1, 63W2, 63W3, 63W4 have been provided for automatic stopping and starting of pump sets. Pumps can also be operated manually by push buttons. For dewatering of m/c the penstock is firstly closed. Then valve(641) on spiral drain is opened. After the water level in the spiral become equal to tail race, drop the D.T gates. Now open D.T drain valve(806) and according to the mode of pump operated speed selected, automatic dewatering of the machine starts.
As the water level rises in dewatering header the level pressure switches(63W1) and (63W3) automatically start the pump sets and pump out water to tail race. On completion of dewatering pressure switch(63W2) stops the pump automatically. High level alarm pressure switch(63W4) is provided on dewatering header.
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The valves(641) and (806) remain open through out the maintenance, inspection of the machine.MECHANNICAL DEVICES_
801- dewatering pump & motor(88MDA,B,C,D)802- foot strainer for 801803- non return valve on 801( discharge)804- gate valve on 801 (discharge)805- pressure gauge with cock817- isolating valve on 802825- drainage pump &motor(88MDE&F)825A- submersible pump &motor(88DG)826- foot strainer for 825827- non return valve on 825( discharge)828- gate valve on 825 (discharge)829- pressure gauge with cock831- non return valve drainage pit839- headstock valve 63W5- draft tube level gauge
ELECTRICAL DEVICES
71W6- high level alarm in drainage pit71W4 e,f,g- level switch to start drainage motor 88MDE/F/G71W5- level switch to stop drainage motor 88MDE/F/G88MDA/B/C/D- dewatering pump motor
A- referenceB- to start 10 HP pump(submersible pump)C- to stop main & send by pumpD- to start main pump E- to start stand by pumpF- high level alarm
3) COOLING WATER SYSTEM- Cooling water system has been provided for each unit for cooling of corresponding generator and transformer. Penstock of each unit is directly connected to isolating valve(701). The raw water line is further connected to strainer isolating valve(707), duplex strainer (703) and pressure switch with cock is provided for alarm at the time of strainer choking, which is are operated through main motor pumps (88MC-A,C,E). Inn case of failure of main motor pumps, the standby Page 13 of 39
motor pumps (88MC-B,D,F) operates. The water line is then divided into two parts, except in case of unit no-2. One line is passed to fire header of 150mm dia and the other is used for cooling of generator and transformer and remaining water is supplied to the turbine.
MECHANICL DEVICES-589- pressure gauge with cock on raw water line701- isolating valve for penstock702- pressure gauge with cock after strainer 703- duplex strainer704- isolating valve on clean water header706- isolating valve on unit cooling water line707- strainer isolating valve711- pressure gauge with cock on unit cooling water line719- isolating valve for transformer cooler 720- motorized valve on cooling water 723- non return valve for 724724- booster pump 730- isolating valve for generator cooling
ELECTRICAL DEVICES-63W5- pressure switch cock for starting stand by pump & alarm63W7- pressure switc with cock for strainer chocking alarm88MCA- motor for main pump unit-188MCB-motor for stand by pump unit-188MCC- motor for unit-2 main pump88MCD- motor for stand by pump unit-288MCE- motor for unit-3 main pump88MCF-motor for unit-3 stand by pump88MCVA- motor for motorised valve (720) unit-188MCVB- motor for motorised valve(720)unit-288MCVC- motor for motorised valve(720) unit-3
4) ISOLATING OIL HANDLING SYSTEM-
It consists of an isolation clean oil tank ICOT having capacity of 25000L, an isolation dirty oil tank IDOT having capacity of 25000L and having a breather with air dust filter moisture absorber, a vacuum dehydration oil purifier, which is used for removal of water and moisture from the oil and portable oil transfer pumps of100LPM capacity. Drain valves (s) is provided on both ICOT and IDOT.
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The clean oil is supplied to oil supply line which is pumped by oil transfer pump and is supplied through isolating oil valve boxes (ivb-1,2,3,4,5,6,7,8) to the station service transformers, generating transformers and unit auxiliary transformers.
1 IV B 1 to 8 8 50NB At EL 227.0 transformer deck to service main transformer, station service transformer & unit auxiliary transformer
2 IV B 9 & 10 2 50NB In oil room at EL 227.0 for fill & reject service
CODE DESCRIPTION
S sampling valve D drain valve IV insulating oil valve IV B insulating oil valve box
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PP portable oil transfer pump VDPR vacuum dehydration oil purifier IDOT insulation dirty oil tank ICOT insulation clean oil tank
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GENERATOR UNIT It is device a that converts mechanical energy into electrical energy. The hydroelectric generator is is of vertical shaft salient pole type. It has a combined thrust and guide bearing located below the rotor . The ventilating air is circulated by two axial fans fitted at each end of rotor. Excitation is provided by separate static excitation equipment.
1) FRAME OR YOKE- It serves as a protective cover for synchronous generators that protects it from ambient condition such as humidity ,rainwater etc. and also provides a mechanical support to stator ,bearing along with cable entry and has a hole for ventilation of air through generator. It is generally made up of hard iron having high resistance to corrosion .Generally it is manufactured in two to four parts so that easy assembly can be done and in case of a fault it can be removed easily.
2) STATOR AND ITS WINDING- The stator core and winding are housed in a fabricated steel frame made in four sections . The stator core is built of varnished segmental silicon steel laminations held in the frame by dovetailed key bars ,welded to the frame . The core is divided into pockets by narrow radial steel spacers ,thus forming ventilating ducts leading from the stator bore to the outside periphery . The core is clamped between the bottom frame plate and segment flanges on the top by means of through bolts.
The stator winding is of the double layer three turn diamond pulled coil type assembled in open slots . Each coil is made of number of copper strands, with semi Roebel transposition in the end winding portion to minimise losses. The slot insulation consists of a number of layers of low loss epoxy glass mica paper tape and flexible mica flake tapes in end winding.
Temperature sensors of resistance type are inserted between coil sides in all three phases to provide a continuous indication of winding temperature.
3) ROTOR AND ITS WINDING - The salient poles are attached to the rotor. The rotor rim is of the friction type and is built up of thin sheet steel lamination rigidly clamped between steel and plates by large number of fine clearance through bolts. The clamping force in the rim Page 17 of 39
is such that frictional forces between the laminations prevent them from slipping relative to one another at any speed up to and including runaway speed.
The spider which supports the rim of fabricated steel construction with arms radiating from a octagon shaped central hub . The upper flange of the hub is machined to supported the fabricated shaft of “PMG” and collector and the flange is machined with a spigot 5to fit into the corresponding recess on the top of the generator shaft. The driving torque is transmitted form the shaft to the spider by radial keys. This method of construction permits the lifting of rotor independent of shaft.
The field poles are built up sheet steel punching clamped between steel end plates and secured to the rim by one T-head projection on each punching and end plates . Axial flow (gives air flowing axially to the shaft) sheet metal type fans are mounted at each end of the rotor. In addition each pole is equipped with five damper bars of circular cross section made of high conducting copper embedded in semi closed slots in the pole face. A polished steel segmental brake track is bolted in underside of the spider hub.
4) SHAFT AND THRUST BLOCK- The generator shaft and thrust block is a one steel forging . The bottom surface of thrust block is fitted with a runner disc and form the rotating thrust bearing surface and is machined to be accurately perpendicular to the axes of the shaft. It is ground to an optical finish.5) THRUST AND GUIDE BEARING ASSEMBLY- The thrust bearing is of spring supported type in which the stationary part consists of white metalled segmental thrust pads supported on a mattress of helical springs (960 in number). The bearing operates immersed in oil.
The thrust pads are of stress relieved mild steel and are faced with a high quality white metal. Each pad rests on precompressed springs finished to a standard overall length. The thrust pads are prevented from rotation by means of pad stop keys secured to the spring plate. Radial movement of pads is prevented by dog clamps which also prevent them from rising with the thrust collar while jacking up the rotor .
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The guide bearing comprises white metal faced pads arranged inside a cylindrical support in the thrust bearing housing & bearing on a journal surface machined on the thrust collar. A pivot bar is secured to the back of each guide bearing pad to enable the pad to rock slightly to take up a suitable position & to facilitate the formation of oil film when running . the clearance between individual pads & the journal is set by adjusting the shims between the back of the pad & pivot bar . the lower part of the pad are permanently immersed in oil & by centrifugal action, the oil is pumped up between the pads & spills over the top of the support in to the reservoir.
The bearing is provided with self lubrication system. The hot coil coming out of the bearing is cooled by means of oil to water heatexchangers mounted inside the housing.There are eight oil coolers.
During starting when hydrodynamic oil film is not likely to be formed, provision is made to inject oil at high pressure through the thrust pads by means of a motor driven high pressure oil pump. The system is design to come into operation automatically on starting and also on stopping the machine.
6)THRUST AND GUIDE BEARING BRACKET-The thrust & guide bearing bracket below the rotor is of fabricated construction. It is designed to support the hydraulic thrust from the turbine in addition to the weight of rotating part of the generator and turbine. The bracket arms rest on sole plates ground in to concrete foundation. Shims are provided for leveling purpose. Sheet steel covers bolted to the underside of the bracket seal the machine enclosure from the turbine pit. The complete bracket is designed such that it can be lifted through the stator bore.
7) TOP BRACKET- It is also of fabricated steel construction and supports the stationary parts of the brush gear creep dector, PMC and over speed device. The bracket also supports the steel flooring on top of generator pit.
8) BRAKES AND JACKS- The generator is equipped with compiled brake and jack units on the low bearing brackets. They are designed to operate on air pressure as brakes and with the high pressure oil as jacks for rising the rotor. The brakes are applied and released by means of continuously rated air valves. The valves can be mutually operated or solenoid operated to supply or release the brakes . The Page 19 of 39
brakes are capable of bringing to the dead stop from 70 rpm in 90 seconds with turbine gate closed and without field excitation.FOR BRAKING- Valve E, F &G closed, valve D & I open. Brakes are normally applied and released automatically through solenoid valve A. For test purpose, brakes can be applied manually by pressing the manual control valve B. brakes are released by releasing valve B.
FOR JACKING(to raise)- valves D,G & H are closed. Valves E & F are opened. Connect flexible hose from hydraulic power unit to adopter S. start pump motor & pump oil until it is observed issuing in tundish K. Then close valve E. Continue pumping until generator rotor has lifted.
Stop pump motor & close valve F.
FOR JACKING (to lower)- Connect flexible hose (oil return to sump of hydraulic power plant unit) to adopter T. Open valve H, crack open valve F & allow time for oil to be expelled from the system. Crackopen valve D, operate the manual control lever D intermittently to force residual oil from pipe work & reset valves as for braking.
9)COLLECTOR RINGS AND BRUSHGEAR- The collector rings are attached to and are insulated from fabricated steel shaft mounted on the rotor spider. The brushgear for the collector is mounted on insulated stand on the top plate of PMG stator and is easily support accessible for inspection purpose. Pressurized air from top air guide chamber is directed into brushgear enclosure for cooling of collector and brushes.
10) CREEP DECTOR- A ferrostate transmission type creep dector is mounted on the top position of generator. This consists of a disc pole wheel bolted to the rotor and a ferrostate transmission fixed on a stationary frame. A control relay detects any rotation of the generator by measuring the variation of pulse signals from the rotation sensing device.
11) COLLECTOR RING AND BRUSH GEAR- The collector rings are attached to and insulated from the fabricated steel shaft mounted on the rotor spider. The lead from the collector to the field run along this shaft and spider and are joined at suitable point facilitate dismantling of the rotor . Page 20 of 39
The brush gear for the collector is mounted on insulated studs on the top plate of PMG stator and is easily support accessible for inspection purposes .Pressurized air from the top air guide chamber is directed into brush gear enclosure for cooling of collector and brush gear.
12) VENTILATION - The generator has a closed circuit system of ventilation .Eight air coolers are mounted on generators stator frame and the cooled air is discharge into the space between coolers and generator barrel from which part of this air will then return to the fan below the rotor through the ducts in the foundation below the air coolers and the remainder of the cooled air will return the fan below the rotor . The air is then circulated through the closed system by the combined action of rotor poles and of the fans .
The water supply to each of the air coolers is controlled by a separate valves so that any one cooler can be isolated if necessary.
13) AIR AND OIL COOLERS- a) AIR COOLER- Each of the eight air coolers consist of a nest of 90/10 copper-nickel alloy wound with copper wire fixed in a mild steel frame . The tube ends are roller expended into brass tube plates on which are mounted the inlet and return end water boxes fabricated from mild steel . the thickness of water box includes generous corrosion allowance and these are internally subdivided to provide for multiple water passes for requisite flow pattern . the inlet water box is fitted with vent valve and reverse end with drain valve. b) OIL COOLERS-Each of the eight plug-in-type oil coolers consist of a bank of ‘U’-shaped 90/10 copper-nickel alloy tubes wound with copper wire carried in a mild steel field with inlet and terminating in a rolled brass tube plate and the other ‘U’ and supported in a tube supported fixed to frame . The tubes are roller expended into the tube plate .The water which of mild steel fabrication is bolted to the tube plate and amply proportioned to reduce turbulence and pressure drop . The water box fitted with main inlet and out let connection, vent valve and drain connection which is plugged .
EXCITATION SYSTEM OF GENERATOR The excitation equipment is designed to draw its input power from the generator output itself.The initial generator voltage built up by field flashing from station auxiliary AC supply or station battery DC supply is employed for static excitation in Tanakpur Hydro Electric Page 21 of 39
Project.It takes its initial supply for field flashing from 415 AC supply provided by UPSEB or generator set installed in project area .
The field flashing equipment consist of field flashing contractor , a step down transformer and a diode bridge for AC field flashing, a voltage dropping resistor and blocking diode. After a voltage,70% of rated value is built up at the generator terminals,the flashing circuit is cut off.The control is taken over by the DIGITAL VOLTAGE REGULATOR in auto or manual channel along with the thyristor bridge depending upon the pre-selected mode of operation.
The generator voltage is step down by suitably rated excitation transformer, is fed to a set of three phase fully controlled thyristor bridges connected in parallel . The total no of thyristor are such that one bridge is redundant. Output of thyristor bridges is fed to the generator field through a field circuit breaker. A resistor through a discharge contact to the field breaker constitutes a field separation network. In other words we can say that the excitation system- 1) provides necessary dc power to generator rotor to produce
magnetic field .2) regulator generator terminal voltage and maintain it at desired level
.3) provides suitable controls to operate the generator with in its
capacity limits .4) provides protection to generator rotor winding in case of trip out .
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ELECTRO-HYDRAULIC GOVERNOR1) PRINCIPLE- The governor is basically speed sensing instrument , sensitive to speed deviation from a set of speed. The speed signal is derived from a permanent magnet generator directly coupled to the turbine generator shaft. Frequency of the PMG out put is directly proportional to the rotational speed of the turbine- generator set. The PMG frequency representing the machine speed is measured in a speed measuring unit which is so designed that at the nominal speed its out put is zero and varies by + 0.8 V/HZ depending on whether the speed is above or below nominal speed.
The SMU out put is fed to a control amplifier which comprise a phase advanced amplifier(for derivative control) & a multi input summing amplifier. The phase advanced amplifier has a resistive capacitive feed back and its gain varies with the rate of change of input signal. Thus it provides speed error signal. In the summing amplifier the modified speed error signal is summed up with speed setting signal, permanent droop signal & temporary droop signal. The signal levels and input resisters are so coordinated that under the steady state , out put of the summing amplifier is zero volt.
The droop signals are derived by comparing the gate setting command signal with the gate feed back signal. The resultant signals directly applied to the summing amplifier through a potentiometer is called permanent droop signal, whereas differentiation of resultant signal with the variable time constant RC network provides the temporary droop signal. The temporary droop signal also known as damping signal transiently opposes the gate movement and thus it provides main stabilization to the speed control loop, which is otherwise highly unstable because of large inertia of the hydraulic system. Both time constant and percentage of the temporary droop signal are adjustable.
The summing amplifier output is amplified in a booster amplifier and then applied top the electromagnetic transducer (EMT) located in the hydromechanical cabinet. It is the linking device between electrical and hydromechanical section. The EMT actuating on the hydraulic amplifier converts the electrical signal into the proportional mechanical movement of the pilot rod. The movement is then imparted to a lever drive of the main slide valve feeding oil to
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either chambers of the gate apparatus servomotor, which in turn controls the main servomotors controlling the gate position.
Under steady state conditions, the electronic cabinet provides balance current of 0milliampere to the EMT. In the event of frequency rising or a lower command, it provides proportional –ve current for closing of the gate and in the event of frequency falling or rise command , it provides proportional +ve current for opening of the gate. Once the gate4 acquires new steady position, the output current resets the 0milliamp (balance current) under action of permanent droop signal. Under the dynamic conditions, output current can vary in the range of –100 to +100 milliamps.
The relay control circuit enables the turbine to be started synchronized, loaded, unloaded, and stopped.
The optional features of governor are –1) Motor operated speed setting potentiometer.5) Motor operated gate setting potentiometer.6) Zero speed detector.
2) OUT LINES OF GOVERNOR-
It consists of the following main components-a) Servomotor b) Relay valvec) Actuator or pendulumd) Dash pot and pilot valvee) Pressure oil supplyf) Casing g) Governor driving mechanism.
3) CONSTRUCTION- The equipment is housed in a single cubicle in accordance with the general assembly diagram. It is provided with full height , front and rare swing doors. Both doors are provided with louvers.
The governor circuits make use of solid state electronic component. The electronic control and power supply circuits are contained within the rack. Potentiometers and indicators are fitted on front side of cubicle. Distribution of circuit in the racks are on
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functional basis. Distribution of component on various sub panels is on the functional basis.
The cubical doors have been provided with louvers for ventilation and they are complete with rubber sealing strips. The cubical is fitted with an anti condensation heater and illuminating lamps. Cable entries are through a removable plate at the bottom of cubical. Terminal blocks for external connection are accessible from the rear door. 4) DESCRIPTION- The regulating rack cotains circuits related with speed sensing, closed loop control, stabilisation and amplification of final speed control signal to a level compatible to the electromagnetic transducer.These are –
4.1) SPEED MEASURING UNIT-It produces the DC control signal such that it is zero at nominal speed and varies by + 0.8V/HZ to a maximum of +13V depending on weather the machine speed is higher or lower than the nominal.
4.2) CONTROL AMPLIFIER- In control amplifier , speed signal(SMU’s output) is modified as accelerometric signal(signal + its rate of change) and is compared with command and feed back signals to produce a resultant corrective signal. It isdivided into four parts-a) Phase advance amplifier- In this the speed signal is modified as accelerometric signal for improving the governor response and stability of speed control loop.b) Dead band unit- It prevents governor action over a small selected band of speed. In measuring system such as the turbine speed measurement in the governor, there is bound to be a certain level of noise/ pickup superimposed on the legitimate signal. This noise may be caused by main hum pickup, switching spikes, nonuniformity of cycles of PMG etc. It is desirable that governor only respond to legitimate signal changed and not to the noise signal. A dead band amplifier included in signal path achieves this if the dead band with is set wide enough to exclude the noise without putting an unacceptable off set error into the system. c) Summing amplifier- It mixes up modified speed error signal received from the phase advance amplifier with signals( speed setting signal, permanent droop signal, temporary droop (damping) signal, speed trim signal, no load gate limit signal, dead band signal) to produce final speed control signal applied to the out put amplifier.
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d) Inverter- Unity gain inverting amplifier A14 has been provided for signal inversion.
COMPRESSOR1) CONSTRUCTION-The screw type air compressor is positive displacement machine like the reciprocating type. A screw compressor has two rotors housed in a cast iron casing. One of the rotor is called male rotor and other is called female rotor. Male rotor has four asymmetric lobes that run helically along the rotor length and female rotor too has six similar helical flutes. These two rotors rotates in conjunction with each other inside the casing. Drive is provided to male rotor, through set of gears. Lubricating oil is into compressor unit (airend) which in large quantity mixes directly with air as the rotors turns compressing the air. The lubricating oil has four functions-
a) As a coolent it takes away the heat of compressor.b) Seals the leakage paths amongst the rotors and housing.C) Acts as lubricating film between the rotors allowing one rotor to
directly drive the other without a metal to metal contact.d) Lubricates the bearings and gears.
Following are the main components and systems of compressor-
a) Airend(compressor unit).b) Compressor air inlet system. c) Compressor air discharge system.d) Compressor cooling and lubrication system.e) Capacity control system.f) Electrical system.g) Safety and protection devices.h) Instrument panel.
2) PRINCIPLE AND WORKING- The air aspired through the air filter is compressed in screw compressor driven by an electric motor. The injected oil removes the compression heat generated. This internal cooling make low compression end temperature. Under normal conditions the compression end temperature is about 80 degree C. Oil and air are separated by the in-line 3-stage oil separator. The Page 26 of 39
separated oil is recooled in the oil cooler and is returned to the injection point via the micro filter. This oil circulation circuit operated solely by pressure differential, does not requires any oil pump. The compressed in oil separating cartridge, except for a very small amount of residual oil, is passed to the air after cooler via minimum pressure non return valve.
The combined minimum pressure non return valve downstream of oil separator maintains a minimum pressure for safe supply of oil to compressor. The temperature of compressed air at the discharge side is lowered to within a few degrees above the ambient temperature by the air after cooler which is fitted as a standard.
3) SALIENT FEATURES OF SCREW COMPRESSOR- The salient features of screw compressor are-
a) Less maintenance.b) Maximum reliability.c) Low discharge temperature.d) Small package.e) Vibration free and low noise.f) Long life.g) Pulsation free flow.h) Low operating cost.
SPECIFICATIONS OF THE EQUIPMENTS USED IN POWER PLANT
A. TRANSFORMERS- TRANSFORMER Transformer is a static device used to convert low voltage into high voltage and vise-versa.If it is used for converting low voltage to high voltage , then it is known as step up transformer. Whereas if it is used for converting high voltage to low voltage , it is known as step down transformer.
EMF equations for a transformer are-V1=4.44FN1 OV2=4.44FN2 O
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Where, V1=voltage at primary side V2=voltage at secondary side N1=number of turns at primary N2=number of turns at secondary O =magnetic flux F=frequency In this project 49500KVA,11KV/220KV transformers has been used. A three limbed, mitered type core construction using CRGO Silicon steel is used. Limbs are bounded by epoxy glass fiber taps.Clamping structures and core sheets are connected to the top of tank at one point. Cylindrical winding using copper wires is used. Internal body consisting of core and coil is supported inside the tank using guide pins at bottom and vibration preventer at the top. Oil is used for insulation of windings and leads, so special care must be taken to maintain oil conditions. Tank is made up of Mild Steel, which is capable of withstanding full vacuum and positive pressure of 0.35Kg/Cm3 over normal oil head.
Transformer is equipped with manually operating off circuit tap changer for voltage variation in range +7.5% to –2.5% located at HV neutral. 50KW oil to water heat exchanger with control cubical is provided for cooling. Double float Buchholz relay, temperature indicators, flow meters, pressure relief device, BCT are provided for various system protection. Buchholz relay is connected in between main tank and conservator. It has two float switches. If transformer is working properly, then the float switches are in off condition. One of the float switches is for alarm and other is for tripping.
In the power house three generator, three excitation, three unit auxiliary transformers, two station service transformers, three neutral grounding transformers has been provided. Generator transformer is used to convert 11KV generated by each unit into 220KV. In excitation transformer no oil is used for cooling. Unit auxiliary transformer takes some of the power generated by the unit and supplies it to the unit elements for their proper functioning.
1) GENERATOR TRANSFORMER- Page 28 of 39
a) Make Transformers and Electricals Kerala Ltd. b)Type WFOC c) Form 3NYCP d) KWA HV 49500 LV 49500 e) Volt (at no load) HV 220000 LV 11000 f) Ampere ( line value) HV 130 LV 2598 g) No. of phases 3 h) Frequency 50HZ i) type of cooling OFWF j) Impedance voltage 12.38% k) Connection symbol YndII l) Mass of core and wdg 44000KG m) Mass of oil 1500KG n) Total mass 71400KG o) Mass of heaviest pkg 50000KG p) Untanking mass 6000KG q) Volume of oil 16800L r) Oil circulation 1*1100L/min s) Water circulation 375L/min
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2) EXCITATION TRANSFORMER- a) Make BHEL, Jhansi b)Type Dry c) KVA 875 d) Primary Voltage 11 e) Secondary Voltage 340 f) No. of phases 3 g) Frequency 50HZ h) Basic impulse level 75
i) Connection DYNS
3) UNIT AUXILIARY TRANSFORMER-
a) KVA 800 b) Volt ( at no load ) HV 11KV LV 415KV c) Current HV 42amp LV 1113amp d) Guaranteed max temp rise in oil 50 degree C e) Type of cooling ONAN f) Frequency 50 HZ g) Impedance 4.888% h) Connection DyII i) Weight of oil 570KG j) Weight of core and wdg 12800KG k) Total weight 2900KG
l) Oil capacity 660L
STATION SERVICE TRANSFORMER-
a) KVA 1000b) Volts (at no load ) HV 11000 LV 415c) Current HV 52.2amp LV 1391ampd) Type of cooling ONANe) Frequency 50HZ
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f) Impedance 5.157%g) Connection DyIIh) Weight of core and wdg 1680KGi) Weight of oil 700KGj) Total weight 3600KGk) Oil capacity 805Ll) Guaranteed max temp rise in oil 50 degree C
5) NEUTRAL GROUNDING TRANSFORMER-
a) Voltage 11000/220 Vb) Current 1.454/72.72 ampc) Frequency 50HZd) Phase 1e) Rating 16KVAf) Withstanding capacity 75 KVA for one min
B) GENERATOR UNIT
1) GENERATOR-
a) 45000KVA, 40500KW, 11000+5%V, 3phase, 50HZ +3%amps, 0.90PF lagging, 44 poles, and 136.4 rpm, runaway speed 280 rpm on cam and 370 rpm off cam.
b) Air gap at pole Centre 14mmc) Stator resistance/phase
at 20 degree C 0.0082 ohms d) Stator connection Ye) Total field winding resistance at 20 degree C 0.1945 ohmsf) Flywheel effect of generator 6000TMsqg) Synchronous reactance 86%h) Trainsient reactance 28%i) Subtransient reactance 17%j) Short circuit ratio 1:1k) Excitation at no load, rated voltage 530Al) Excitation at rated load 900Am) Slipring brushes total 24(12/ring)n) Size 25.4*38.1mmo) Brush grade Morgan E.C.G.O.R
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2) BEARINGS-
a) Thrust bearing type spring mattressb) No. of pads 10c) Pad dimensions 1080mm I/D and 2230mm O/Dd) Total load 760000KGe) Guide bearing type pivoted padf) Pad dimensions 250*250mm 2050mm dia
g) Normal operating temp Of bearing pads 65 degree C
h) Max operating temp Of bearing pads 70 degree C
i) Grade of oil IOC servoprime-57j) Qty of oil for one filling 7400L
3) COOLING WATER SYSTEM-
a) Cooling requirement:Air coolers 3400L/minOil coolers 1120L/minNormal working pressure 7KG/sqCM
a) Number of units 8 off *235 mm dia b) Brake pad material ferrobestos grade MW-82c) Brake pad size 325*325mm d) Wearing depth of pad 19mme) Brake operating air pressure 5Kg/sqcm(recommended) 7Kg/sqcm(max)f) Jacking oil pressure 85 barg) Brake application speed 70rpm(max)
b) Controls- 220+ 10%V DC station battery 415+10%V AC,50 HZ,1 phase 3 phase station AC supplyc) Lighting & heating- 230 +10%V AC ,50HZ, 1 phased) Selsyns for gate position and gate limit position indication-50+
10%V AC ,50HZ,1 phase.3) OUTPUT TO EMT- a) Stesdy state – zero milliamp DC b) Maximum variation under dynamic conditions-+100 milliampc) Dither current- 0 to 50 milliamp AC (adjustable) 4) CONTROL RANGES- a) speed setting- 45 to 55 HZb) gate setting- 0 to100% 5) ADJUSTMENTS-A) ELECTRONIC CIRCUIT-1)CHARACTERISTIC ADJUSTMENTS- a) Permanent droop - 0 to 10%b) Of line temporary droop time constant - 0 to 25sec
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c) Off line temporary droop - 0 to100% d) On line temporary droop time constant -0 to 25 sece) On line temporary droop 0 to100%2)OTHER ADJUSTMENTS-a) Gate feedback signal range adjustments (upper range)- -13V (full load)c) Gate feedback signal range adjustment (lower range)- +1V (no load)d) Speed trim- 48 to 50 HZe) Closing damping limit- 0to 100%f) Opening damping limit- 0 to 100%g) No load gate limit- 0 to 100%h) Dead band- 0 to +0.5HZi) Phase advance- 0 to 11j) Dither current- 0.50 mA ACk) Sensitivity- 4 to 40 mA/HZ
B) RELAY CIRCUIT- Potentiometers are provided in series with speed relay coils for adjustment of pick-up/drop-off voltage.
D) TURBINE-a) Type- Vertical shaft Kaplan turbineb) HP- 19200HPc) Number of blades- 6d) Speed- 136.4rpm (clockwise)e) Shaft diameter- 750mmf) Bore diameter- 350mmg) Length of shaft- 4940mm
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h) Material used- Forged cast steel having integrated flanks at both ends having coupling holes and nuts for turbine runner end.
LOAD% 100
90 80 70 60 50 40
O/P(MW)
41.92
37.73 33.54 29.16 25.16 20.96 16.77
Eff% 92.0
92.75 93.2 93.15 93.0 92.40 91.4
Dis(cumces)
192.0
171.2 167.5 132.8 113.8 95.46 77.21
E) COMPRESSOR-
1) COMPRESSOR DETAILS-
a) Make- Elgi equipment Ltd.b) Model- THPC-2000Tc) Type- Reciprocating, air cooledd) Free air delivery- 60 cubic M/hre) Working pressure- 50KG/sqcmf) No. of cylinders- 3g) No. of stages- 3h) Cylinder bore/stroke- 1st stage- 127/85mm 2nd stage- 70/85 3rd stage- 50/85i) Compressor speed- 1250 rpmPage 35 of 39
j) Type of valves at suction & delivery- 1st stage- individual disc valve 2nd & 3rd stage- finger type valvek) No. of belts- 2l) Belt size- C98m) Type of filter- Dry typen) Overall dimension(L*W*H)- 2000*790*1030mm
o) Pressure switch cuts out at- 50KG/sqcm cuts in at- 45KG/sqcmp) Safety valve bursting pressure- fitted at first stage- 7KG/sqcm fitted at second stage- 18KG/sqcm fitted at after cooler- 55KG/sqcm
2) MOTOR DETAILS-a) Type- 3 phase, induction motorb) Voltage- 415 +10Vc) Current- ACd) Class of insulation- Be) Frequency- 50HZf) Power- 20HPg) Speed- NGEF- 1460rpm
Hbb- 1455rpm
F) OTHER EQUIPMENTS-
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1) CIRCUIT BREAKER-
a) Type- 200-SFM-40Ab) Rated voltage- 245KVc) Rated insulation level- 1050KVpd) Rated frequency- 50 HZe ) Rated normal current- 3150Af) Rated short circuit breaking current
1) RMS value of AC component- 40KA2) Percentage DC component- 50%
g) Rared short circuit making current-100KAh) Rated break time-60ms(3 cycles)i) Rated short time current-40 KA for 3secj) Operating sequence-0-0.35-co-3min-cok) Rated TRV-364 KVpl) Operating mechanism-spring closing, pneumatic trippingm) Operating pressure(air)-15 Kg/sqcmn) SF6 gas pressure-6Kg/sqcm at 20 degree Co) Applicable standard-IEC-56p) Opening time-30msq) Closing time-10msr) Pole discrpancy(between poles)-3.3ms
2) COOLING MOTOR PUMP-
a) Max. pressure Kg/sqcm-8b) Max. temperature degree C-40c) Hyd. Test at Kg/sqcm-10.5
3) AUTOMATIC GREASE LUBRICATION UNIT-
A)AUTOMATIC GREASE LUBRICATION –
a) Type- end typeb)Working pressure-125 Kg/sqcmc)Capacity cc/min-500d) Make-Prakash Lubriquipment(Pvt.) Ltd.
B) SOLENOID VALVE-
a) Connection –1/2 BSPTb) Working pressure-125 Kg/sqcmPage 37 of 39
h) Solenid coil-220V AC
C) CUTTRE HAMMER-a) Max. stroke –31.4mmb) Pull-0.75 Kgc) Duty cont.
Volt-220V HZ-50 Type-SLD
4)HIGH SPEED LUBRICATION OIL PUMP MOTOR STARTER-
a) Volt-415V b) Amperes-63Ac) Frequency-50HZd) Make-Telcon Industries
