Training Reports (updated)
Seminar Reports (updated
Placement Papers (updated)
Power Station Comprising
For the power generation with 2x110 MW and 3x210 MW of K.T.P.S. authorities are required to be operative to active full operation. The auxiliaries are basically operation either on L.T. System i.e. 415 V 3 Ø power supply is made available to the system after providing the station transformer of 3x50 MVA capacity with voltage 220 KV/ 7.2/7.2 KV & different service transformers of capacity 1.0 MVA , 1.5 MVA , 2.0 MVA , which are located near the load centre as the transformer having the voltage of 6.6 KV /415 V. The 6.6 KV power is distributed through 6.6 KV interconnected Bus System for all the five units with a control through DC of 220 V.
The 415 V power supply is done through a L.T. SWGR (Switchgear) which are located nearby the distribution transformer as well as the load centers. The all in -comers, which are breaker controlled , are having the control the L.T. SWGR are having the control system on 110/ 220 V AC. The 6.6 KV power supply which are either MOCB (Minimum Oil Circuit Breaker) of JYOTI MAKE or Air Circuit Breakers.
The 6.6 KV power supply to various draining equipment’s i.e. more is made through breakers which are either MOCB of Jyoti make air circuit breaker which are either of voltage makers as well as SF 6 of NGEF make. The LT supply is also controlled through air break circuit breaker which are either L&T make or English Electric Company of India. The various H.T. motors are switched on / started through on direct ON line (DOL) in order to inverse the availability of equipment at full efficiency without time gap.
Further , the 6.6 KV system which is normally in delta configuration and terms as an unearthed system so also to keep the running motor complete in operating condition in case of any one .phase of motor winding is earthed due to any one reason. Earthling is detected by an protection system with alarm facility to take remedial measures immediately and at the same time to maintain the generation level in the same condition, prior to occurring the earth fault the single phase earth fault is detected in due course till the motor is not earthed to other or another phase.
“ PUBLIC ADDRESS SYSTEM” is available through in area of each unit which helps in fast communication for prompt remedial measure.
Soot Blowers are there in the boiler area on the furnace side or Zone which helps in blowing the soot / ash deposition regularly of the furnace wall / economizer tubes to keep heat transfer at the required parameter.
In April 1973, Central Electricity Authority prepared a Project Report for power station comprising of the two units of each of capacity 110 MW for RSEB subsequently in September., 1975 this was revised by the Consultant Thermal Design Organization , Central Electricity Authority for invention of 2x110 MW units being manufactured by BHEL, Hyderabad in 1st Stage.
The planning commission cleared the project report in Sept., 1976 for installation of two units each of 110 MW in first estimated cost of Rs. 143 Crores.
K.T.P.S. IS DESISIGNED IN FOUR STAGES
v STAGE I - 2x110 MW
v STAGE II - 2X210 MW
v STAGE III - 1X210 MW
v STAGE IV - 1X195 MW *
Total Power Generation - 1045 MW
* To be commissioned shortly in August, 2003.
The Kota Thermal Power Station is ideally on the left bank of Chambal River at Up Stream of Kota Barrage . The large expanse of water reached by the barrage provides an efficient direct circulation of cooling system for the power station. The 220 KV GSS is within ½ Kms. from the power station.
Land measuring approx. 250 hectares was required for the project in 1976, For disposal of ash tank very near to power station is acquired which the ash in slurry form is disposed off through ash and slurry disposal plants.
Coal India limited owns and operates all the major coal fields in India through its coal producing subsidiary companies viz. Eastern Coal Fields Limited, Western Coal Fields Limited/
Coal India limited is supply coal from its coal mines of coal producing subsidiaries BCCL, SECL & ECL to Kota Thermal Power Station through railway wagons. The average distances of SECL, ECL & BCCL are 800, 950 and 1350 Kms. respectively.
The source of water for power station is reservoir formed by Kota Barrage on the Chambal River. In case of large capacity plants huge quantities of coal and water is required. The cost of transporting coal and water is particularly high. Therefore, as far as possible, the plant must be located near the pit rather than at load centre for load above 200 MW and 375 MW . The transportation of electrical energy is more economical as compared to the transportation of coal.
The satisfactory design consists of the flowing steps.
Estimation of cost.
Selection of site.
Capacity of Power Station.
Selection of Boiler & Turbine.
Selection of Condensing Unit.
Selection of Electrical Generator.
Selection of Cooling System.
Design of Control and instrumentation system.
The design of steam power station requires wide experience as the subsequent operation and maintenance are greatly affected by its design. The most efficient design consist of properly sized component designed to operate safely and conveniently along with its auxiliaries and installation.
General Layout & Basic Idea
A control system of station basically works on Rankin Cycle. Steam is produced in Boiler is exported in prime mover and is condensed in condenser to be fed into the boiler again. In practice of good number of modifications are affected so as to have heat economy and to increase the thermal efficiency of plant.
The Kota Thermal Power Station is divided into four main circuits :
v Fuel and Ash Circuit.
v Air and Gas Circuit.
v Feed water and Steam Circuit.
v Cooling Water Circuit.
Fuel & Ash Circuit
Fuel from the storage is fed to the boiler through fuel handling device . The fuel used in KTPS is coal , which on combustion in the boiler produced the ash. The quantity of ash produced is approximately 35-40% of coal used. This ash is collected at the back of the boiler and removed to ash storage tank through ash disposal equipment.
Air and Gas Circuit
Air from the atmosphere is supplied to the combustion chamber of Boiler through the action of forced draft fan and induced draft fan. The flue gas gases are first pass around the boiler tubes and super heated tubes in the furnace, next through dust collector (ESP) & then economizer. Finally, they are exhausted to the atmosphere through fans.
Feed Water and Steam Circuit
The condensate leaving the condenser is first heated in low pressure (LP) heaters through extracted steam from the lower pressure extraction of the turbine. Then its goes to dearator where extra air and non-condensable gases are removed from the hot water to avoid pitting / oxidation. From deaerator it goes to boiler feed pump which increases the pressure of the water. From the BFP it passes through the high pressure heaters. A small part of water and steam is lost while passing through different components therefore water is added in hot well. This water is called the make up water. Thereafter, feed water enters into the boiler drum through economizer. In boiler tubes water circulates because of density difference in lower and higher temperature section of the boiler. The wet steam passes through superheated. From superheated it goes into the HP turbine after expanding in the HP turbine. The low pressure steam called the cold reheat steam (CRH) goes to the reheater( boiler). From reheater it goes to IP turbine and then to the LP turbine and then exhausted through the condenser into hotwell.
Cooling Water Circuit
A large quantity of cooling water is required to condense the steam in condenser and marinating low pressure in it. The water is drawn from reservoir and after use it is drained into the river.
GENERATOR AT K.T.P.S.
Thermal power station burns the fuel and use the resultant heat to raise the steam which drives the turbo-generator. The fuel may be “Fossil” ( Coal , Oil and Natural Gas) whichever fuel is used the object is same to convert the heat into mechanical energy to electrical energy by rotating a magnet inside the set of winding. In a coal fired thermal power station other raw materials are air and water. The coal is brought to station by train or other means travels from the coal handling system.
i) By conveyer belts to coal bunkers from where it is fed to pulverizing mills.
ii) Mills grind it fine as face powder.
iii) Then this powdered coal mixed with preheated air is blow into boiler by a fan known as primary air fan (PA fan).
iv) When it burns more like a gas as solid in conventional domestic or industrial grate with additional amount of air called secondary air supplied by “Forced Draft Fan”.
As the coal has been grinded so resultant ash is also as fine as powder. Some of its fine particles blinds together to form lumps which falls into the ash pit at the bottom of furnace.
v) The water quenched ash from the bottom of furnace is carried out boiler to pit for subsequent disposal.
vi) Most of ash still in fine particles form is carried out to electrostatic precipitators where it is trapped by electrode charged with high voltage electricity. The dust is then conveyed to the disposal area or to bunkers for sale.
vii) Now after passing through ESP few gases are discharged upto chimney by “Induced Draft Fan”.
Meanwhile the heat reloaded from the coal has been absorbed by kilometers long tubes which lies in boiler walls inside the tubes “ Boiler Feed Water” which is transferred into turbine blades and makes them rotate.
To the end of the turbine rotor of generator is coupled, so that when turbine rotates the rotor turns with it. The rotor is housed inside the stator having coil of copper bars in which electric is produced through the movement of magnetic field created by rotor.
The electricity passes from the stator winding to the transformer which steps up the voltage so that it can be transmitted effectively over the power line of grid.
The steam which has given up its heat energy in changed back into a condenser so that it is ready for reuse. The cold water continuously pumped in condenser. The steam passing around the tubes looses heat and rapidly change into water. But these two types of water ( boiler feed water and cooling water ) must never mix together. The cooling water is drawn from the river but the Boiler Feed Water must be pure than potable water ( DM Water).
Now the question arises why do we bother to change steam from turbine to water when it is to be heated up again immediately ?
Laws of Physics gives the answer which states that the boiling point of water is related to pressure. The lower the pressure lower the boiling point temperature. Turbine designer wants boiling point temperature as low as possible because it can only utilize the energy from steam when change back to water, he can get no more work out at it. So there is a condenser which by rapidly changing the steam into water a vacuum. The vacuum results in a must power at lower boiling points which in turn mean it can continue getting out of steam will below 1000C at which it would change into water.
To condense volume of cooling water is huge and continuous volume of cooling water is essential. In most of the power stations , the same water is to be used over and over again, so the heat which the water extract from the steam in the condenser is removed by pumping water out of cooling tower. The cooling tower is simple concrete shell acting of air. The water is sprayed out at top of tower and as it falls into pond beneath it cooled by the upward draft of air. The cold water in the pond is then re-circulated by pumps to condensers. Invariably however some of the water drawn upwards as vapor by the draft .
220 KV System
Two 220 KV bus bars have been provided in switch yard and are inter-connected through a bus coupler. Each of the two 110 MW generator is connected to this system through a step up of 125 MVA 240/ 11 KV yard generator transformer. There are two step down transformer each feeding 6.6 KV system ( Station Switchyard ) viz. BS-IS & SB-IB. Each station transformer has two windings one secondary side and is rated for 50/25/25 mva , 270/7/7.2 kva four feeder take off from 220 switch yard, two to SKATPURA ,GSS and other to HEERAPURA , Jaipur GSS. Each of four feeder are provided with bypass isolators which is connected across line breaker and breaker isolator. By closing bus coupler between 220 KV buses and putting line feeders whose breaker required maintenance of any one bus through by pass isolators and all other line feeders whose breaker is by passed is then transformed to bus coupler breaker. A brief description of equipments of 220 KV system is as follows.
Each of generator transformer, station transformer, line feeder and bus coupler is provided with minimum oil circuit breaker of BHEL make. It is rated for 245 KW, 2500 A and 13400 MVA circuit breaker is used to break the circuit either in load condition or in no load condition.
All the isolators are provided in 220KV switchyard and are motor operated. Triple pole double breaker type and power switch yard L&T make these and are rates for 245 KV and 1250 A. The four isolators are provided with earth switch.
All the 220 KV current transformers are provided for measuring and protection. They are BHEL make, single phase, oil filled nitrogen sealed outdoor type. All the E.T.S. are multi-cored with each core having specification upon duty it is to perform. Feeder circuit have 5 cores.
1) Bus bar protection core I 1250/250/IA.
2) Distance protection core II 600-300/IA.
3) O/C and E/F protection core 600-300 /IA.
4) For metering and measuring 600-300/ IA.
Each of 220 KV buses is provided with three P.T.’S are core for each phase of BHEL make. There are single phase , oil filled outdoor. N2 sealed , elicitor magnetic type P.T. has two secondary windings on secondary side and selected for 220/53 KV, 10/53 KV.
One secondary winding has O/P of 500 mva accuracy class .5 and is used for metering other secondary winding has O/) of 200 mva accuracy class 3 and used for protection.
For protection against lightening each of line feeder, generator transformer , station transformer has been provided with three L.A. (one for each phase). All the L.A. are 2 Ø outdoor type and are rated for 198 KV these are manufactured by W.S. insulator. The L.A. of generator transformer and station transformer are located near them.
It has larger value of capacitance and will change upto line voltage. If we have to do some work on line, first earth line through earthing isolator for discharging the line capacitance and then work.
220 KV MOCB
Manufacturer : BHEL, Hyderabad.
Total Nos. : 9
Type : HLR 245/2503 B-I.
Rated Frequency. : 50 Hz.
Nominal Current. : 2240 Amp.
Type of operating mechanism. : Motor charging Spring
220 KV ISOLATORS
Manufacturer : A&S Power SWGR LTD
Number : 36
Type : Double break operated.
Rated Current. : 1250 Amp.
No. of Phase. : 3 Ø
Rated Voltage. : 245 KV.
220 KV Current Transformer
Manufacturer. : BHEL, Trichy.
Type : Outdoor, Oil filled.
Rated Voltage. : 220 KV.
Nominal : 220 KV.
Max. : 245 KV.
Rated Frequency. : 50 Hz.
No. of Phase. : 1-Ø
Class of Insulation : A.
Rated Primary Voltage. : 2220/ 53 V.
Secondary Voltage Wdg.I : 110/53 V.
Wdg.II. : 110/53 V.
MAIN BUS BAR
Material : Electrolyte Aluminium.
Type of Insulation. : Air.
Maximum clearance B/W Phase.: 19.3 mm.
Minimum clearance B/W Phase.: 15.3 mm.
Make : L&T Circuit Breaker Ltd.
Type : Air Circuit Breaker.
Maximum Continuous Voltage : 500 V.
for circuit breaker operation.
No. of Phase. : 3-Ø
Rated Voltage. : 415 V.
Make : L&T Limited.
Type. : ML1 ML2 ML3 ML4 ML8 ML12.
No. of Poles. : 3.
Rated Voltage for main Contacts. : 500 V.
220 KV LIGNTENING ARRESTOR
Manufacturer. : W-S Isolators India Ltd. Chennai.
Type : Heavy Duty CPL II.
No. of Phases. : 3-Ø
Rated Voltage. : 198 KV.
Nominal Discharge Current. : 10 KA.
High Current Impulse. : 100 KA.
Long Duration Rating. : 500 KA.
D.C. system play important role in all the major industries. We can call it as ‘back bone’ of industries. It can be utilized and stored during specific duration. Charging the battery initially to keep the batteries trickily charged and to mention the and load in normal time, a separate equipment called ‘charger’ is a must.
A.C. supply is converted to D.C. by this component only. It has two major classification. The basic components which are use now a days are diodes and SCRs.
Rectifiers are classified as follows :
1) Half wave rectifier.
2) Full wave rectifier.
b) Half controlled.
c) Fully controlled.
Filters are used for smoothing the D.C. output voltage from rectifier unit. Chock input filter, and capacitor input filter is two type of filter in chock, input filters, the chock blocks A C ripples if any ripples get through chock, passes through capacitor ( very low xc) which appears to open for D C signals.
In capacitor input filter the capacitor following output wave and get charge to peak voltage Vp when rectifier conducts. One output voltage stands to reduce from peak voltage, the capacitor stands discharging and keep voltage almost constant.
To get block the back feed from batteries to chargers, blockers diodes are connected in series with filter output.
Based on charges application, we call the chargers as float charges and boost charger. Float charger, keeps the battery in trickle charging condition and meant the load in normal condition. If there is any small interruption in A.C. supply batteries will meet the load. On resumption of supply, batteries will get charged. Boost charger is normally used to charge during initial charging and in the case of heavy discharging. It can also meet the loss but not directly. By making special tapping provision from batteries.
There are a number of methods to vary the charger output voltage to certain extent by making modification circuit. In the controlled rectifer bridge by having feed back system we can get the desired voltage by presenting the reference voltage in the un-controlled rectifier bridge, by varying the A.C. input voltage we can get desired output voltage.
In high rating charges , main transformer secondary is connected in series with another transformer secondary booster transformer primary can be varied by connecting the dim merstal. In this variation will be smooth. In low rating chargers , it is achieved by taking required number of tapping from secondary for A.C. voltage variation.
MODE OF OPERATIONS
Charger can be operated in two modes depending upon its design.
1) Constant Voltage Mode :
Here the charger output voltage is always maintained at constant voltage equal to reference voltage irrespective of charger output current. So some current limitation has to be provided in this mode. This mode will be ideal for keeping the batteries in floating condition and to meet the loads.
2) Constant Current Mode :
In this charger put current will be maintained at reference current sitting. It do not take care of voltage condition. This mode will be useful for calculating all rating of batteries charged.
In A C side charges may be provided with overload protection to avoid overload, fuses and single phasing and phase fail protection. Sometime provided with AC under voltage and AC abnormal voltage protection.
In DC side , Diodes and SCRs will be provided with semiconductor fuses for fast action on short cut faults. Output will be provided with HRC fuses converted output will be continuously monitored in each link to find the failure.
1. THEORY : TURBO GENERATOR manufactured by B.H.E.L. and incorporated with most modern design concepts and constructional features , which ensures reliability, with constructional & operational economy.
The generator stator is a tight construction, supporting & enclosing the stator windings , core and hydrogen coolers. Cooling medium hydrogen is contained within frame & circulated by fans mounted at either ends of rotor. The generator is driven by directly coupled steam turbine at a speed of 3000 r.p.m. the Generator is designed for continuous operation at the rated output . Temperature detectors and other devices installed or connected within then machine, permit the windings, teeth core & hydrogen temperature, pressure & purity in machine under the conditions. The source of excitation of rotor windings is thyrister controlled D.C. supply. The auxiliary equipment’s supplied with the machine suppresses and enables the control of hydrogen pressure and purity, shaft sealing lubricating oils. There is a provision for cooling water in order to maintain a constant temperature of coolant (hydrogen) which controls the temperature of windings.
2. STATOR FRAME : The stator frame of welded steel frame construction, which gives sufficient & necessary rigidity to minimize the vibrations and to withstand the thermal gas pressure. Heavy end shields enclose the ends of frame and form mounting of generator bearings and radial shaft seals. Ribs subdivide the frame and axial members to form duct from which the cooling gas to & fro radial ducts in the core and is re-circulated through internally mounted coolers. All the gas ducts are designed so as to secure the balanced flow of hydrogen to all parts of the core. The stator constructed in a single piece houses the core and windings. The horizontally mounted water cooled gas coolers being so arranged that it may be cleaned on the water side without opening the machine to atmosphere. All welded joints exposed to hydrogen are specially made to prevent leakage. The complete frame is subjected to hydraulic test at a pressure of 7 ATA.
3. STATOR CORE : - It is built up of special sheet laminations and whose assembly is supported by a special guide bass. The method of construction ensures that the core is firmly supported at a large number of points on its periphery. The laminations of high quality silicon steel which combines high permeability with low hystersis and eddy current losses. After stamping each lamination is varnished on both sides with two coats. The segment of insulating material is inserted at frequent intervals to provide additional insulation. The laminations are stamped out with accurately fine combination of ties. Laminations are assembled on guide bass of group separated by radial ducts to provide ventilation passage. The ventilation ducts are disposed so as to distribute the gas evenly over the core & in particularly to give adequate supports to the teeth. At frequent intervals during stacking the assembled laminations are passed together in powerful hydraulic press to ensure tight core which is finally kept between heavy clamping plates which are non-magnetic steel. Use of non-magnetic steel reduces considerably by heating of end iron clamping. The footed region of the core is provided by pressing figures of non-magnetic steel, which are welded to the inner periphery of the clamping plates. In order to reduce the losses in the ends packets special dampers are provided at either ends of core. Mostly dampers are provided to prevent hunting in ac machines.
4. STATOR BARS : Stator bars are manufactured as half bars. Each stator half coil is composed of double glass cover and bars of copper transposed in straight portion of “ Robill Method” so that each strip occupies every radial portion in the bar. For an equal length along the bar. They are made in strips to reduce skin effect. The winding overhead is in volute shape. The overhung portion of the bar is divided into four quadrants & insulated . The arrangement reduces additional losses due to damping currents which otherwise be present due to self-induced non-uniform flux distribution in the coil slots. The main distribution for the bar consists of resin rich mica loosed thermosetting epoxy. This has excellent mechanical and electrical properties & does not require any impregnation. Its moisture absorbing tendency is very low and behavior of mica is for superior than any other conventional tape insulation system. Semi-conductor coating is also applied to a part of overhung with a straight overlap of conductive coil in the sides to reduce eddy currents to minimum. Conductor material is electrolytic copper connections brazed with free coating silver alloy to obtain joints , which are both electrically & mechanically sound.
5. STATOR WINDINGS : Stator windings are double star layers , lap wound, three phase, short pitch type. The top & bottom are brazed and insulated at either end to form turns. Several such turns form a phase . Phases are connected to form a double star winding. The end of winding form involute shape ends, inclined towards machine axis by 20o, thus form a basket winding with total induced conical angle of 400 . Due to this stray load losses in the stator ends to zero. The arrangement of complete stator winding electrical circuit is viewed from turbine end of generator & rotor windings. Slot numbering is clockwise from turbine end. A thick line identifies the top bar in slot No.1 . End windings will be sealed against movement of short circuit by both axial & peripheral bracing. The later consists of hardened glass laminated blocks inserted between adjacent coil sides in coil overhangs, so that with the coils , they form a continuous rigid ring. Glass cord or top is used lashing the packing of blocks. The complete assembly is secured b y high tensile brass blots. The winding is designed to withstand short circuit stresses. The exposed portion of windings are finally coated. Insulation of individual bars & stator windings at various stress is tested with applied high voltages of AC of Hz.
6. TERMINAL BUSHINGS : Six output leads (3 long,3 short) have been brought out of the coming on the exciter side. External connections are to be made to the three shorter terminals, which are phase terminals. The large terminals are of neutral & current transformer is inserted. The conductor of Generator terminal bushing having hollow copper tubes with Copper brazed at the ends to avoid leakage of hydrogen. Hollow portions enables bushings to be hydrogen cooled. Ends of bushings are Silver-plated : middle portion of the bushing is adequately insulated & has a circular flange for bolting the stator casing. Gaskets are provided between the Flange of terminal bushings and castings to make it absolutely gas tight.
7. BEARINGS : Generator bearings have electrical seats of consists of steel bodies with removable steel pads. The bearings are formed for forced lubrication of oil at a pressure of 2-3 ATM/ From the same pump that supplies oils to the turbine , bearings & governing gears. There is a provision to ensure & measure the rotor bearing temperature by inserting a resistance thermometer in the oil pockets.
8. VENTILATION SYSTEM : The machine is designed with ventilation system having 2 ATM rated hydrogen pressure. Two axial fans mounted on either side of the rotor to ensure circulation of hydrogen. The stator is designed for radial ventilation by stem. The end stator core packets & core clamping & plates are intensively cooled by Hydrogen through special ventilation system. Design of special ventilation is so as to ensure almost uniform temperature of rotor windings and stator core. Rated load operating temperature is well within the limits corresponding to the Class B operation. Embedded Resistance Temperature Detectors do continuous monitoring of Hydrogen temperature at active parts of Generator.
RESISTANCE TEMPERATURE DETECTORS (R.T.D.) : An R.T.D. is a point resistance element. Operation of R.T.D. depends on the principal that electrical resistance of metallic conductor varies linearly with temperature.
Ø APPLICATIONS : RTD & its associated equipments are designed for use with Generator to determine temperature at various parts & places. The equipment’s consists of two
1. Switch Board Equipment : is usually includes a temperature indicating meter, test resistor transfer switch & leads.
2. Machine Equipment : is usually includes temperature R.T.D. leads and terminal blocks with grounding connections.
Leads from RTD are brought out to the terminal board by cables through conduits to protect them from physical damage and from contact with high voltage coils. Some RTDs are in stator teeth with 7 spacers , 7 RTDs between the coil sides in stator slots with 7 spacers and 3 RTDs are there in the stator core with spacers. The location of RTDs is in three phases i.e. in the centre of machine , in each region of machine and midway between them. The detectors in the stator slots are distributed uniformly in all three phases. Measurement of temperature of Hydrogen cooling water for Hydrogen coolers & metals is as :
Six RTDs are provided at the inlets of each of six individual Hydrogen cooler elements for measurement of temperature of Hydrogen, similarly Six RTDs are provided at the outlets also. One RTD along-with one spacer is provided in the lower part of stator frame for measurement & signalization of hot Hydrogen. Six RTDs are provided at outlets of each of six individual Hydrogen Cooler elements for measurement of temperature of cooling water at the outlet.
MEASUREMENT OF BEARING TEMPERATURE
Two RTDs are provided in the shelves of Turbo-Generator for measurement of signalization of the bearing metal cap. All the terminals of RTDs are brought out to a common terminal board located on the stator frame.
Three Hydrogen Coolers each comprising of two individual units are mounted inside the stator frame. The inlet and outlet of cooling water from both of machine i.e. from non-driving side as well as turbine side. The Clearing of the individual cooler element can be carried out from both ends of the Generator even during operation. The assembly of individual cooler elements in stator frame is however carried out only from the non-driving side.
Rotor shaft consists of single piece alloy steel forging of high mechanical and magnetic properties performance test includes :-
1. Tensile test on specimen piece.
2. Surface examination.
3. Sulfur prist tests.
4. Magnetic crack detection .
5. Visual examination of bore.
6. Ultrasonic examination.
Slots are milled on the rotor gorging to receive the rotor winding. Transverse slots machined in the pole faces of the rotor to equalize the moment of inertia in direct and quadrilateral axis of rotor with a view minimizing the double frequency.
VIBRATION OF ROTOR : The fully brazed rotor is dynamically balanced and subject to 120 % over speed test at the work balancing tunnel so as to ensure reliable operation.
ROTOR WINDINGS : rotor winding is of direct coil type and consists of parallel strips of very high conductivity Silver Bearing Copper, bent on edge to form coil. The coils are placed in impregnated glass, laminated short shells; using glass strips inter turn insulation and will be brazed at the end to form continuous winding. The complete winging will be packed at high temperature and pressed to size by heavy steel damping rings. When the windings have cooled, heavy dove tail wedges of non-magnetic materials will seal the insulation at the top of slot portion. The cooling medium hydrogen gas will be brought in direct contact with copper by means of radial slots in embedded portion. Treated glass spacers inserted between the coils and solid ring prevent lateral movement of coil overhang. The formation and description of glass spacer is such as to leave ample space for ventilation.
The bearings are self-aligned & consist of slip steel shells linked with special bearing metal having very low coefficient of friction. The bore is machined on an elliptical shape so as to increase the mechanical stability of the rotor. The bearing are pressure lubricated from the turbine oil supply. Special precautions are taken to prevent oil & oil vapor from shaft seals and bearing along the shaft. The circulation of shaft current is liable to damage. The bearing surface is protected by insulation so placed that the bearings, seals & necessary pipes are inclined from the frame.
The slip rings are made of forged steel. They are located at either side of Generator Shaft. The slip ring towards the exciter side is given +ve polarity initially. They have helical grooves and skewed holes in the body for cooling purpose by air. Calibrated mica is first built up to required thickness on the shaft where slip rings are located. The slip rings are insulated from the rotor shaft. Excitation current is supplied to the rotor winding. Through the slip rings, which are connected to the winding. On one end and to the slip ring on the other end with insulated ( terminal) studs passing ‘though’ the radial holes in the rotor shaft. The terminal studs at both the ends of excitation leads are fitted gas cat seals to prevent leakage.
BUSH GEAR ASEMBLY
Generator bushes are made from the various compositions of natural graphite and binding material. They have a low coefficient of friction and are self lubricating. The brushes are provided with a double flexible copper or pigtails. A helical spring is mounted rapidly over each bush so that pressure is applied on the centerline of bush. A metal cap is riveted to the brass bead and is provided with a hole to maintain the position of the spring plug. Several brush holder, each carrying on brush in radial position are fixed to a silver plated copper studs mounted on the collecting arm concentric with each slip rings. The collecting arm is made out of a copper strip.
DRYING OF WINDING
Generator stator bars are insulated with mica insulation , which is homogeneous in nature and practically impervious to moisture, and reduce time required to draught. The insulation resistance of the stator phase winging against earth and with reference to other phases under hot condition shall not be less than the value obtained automatically.
Rin = µ/(s/100+1000) m 52
U = rated winding Voltage under test.
Rin = insulation resistance under hot conditions
Rated o/p of turbo generator.
The insulation resistance of entire excitation system circuit. In hot condition must not fall below 0.5 m 52. The insulation resistance in calculated as per the formula :
Rin = Rv (U1 +U2) /( U-1)
Rin = Insulation resistance of exciter ()
Rv = Internal resistance of voltmeter ()
U1 = Voltage measured btw. Slip ring & shaft/ earth(volts).
When starting the drying process, the winding insulation resistance will usually decrease when the drying process becomes effective; the insulation will gradually increase.
COOLING SYSTEM :
a) GENERAL: In KTPS hydrogen cooling system is employed for generator cooling. Hydrogen is used for cooling medium primarily because of its superior cooling properties & low density. Thermal conductivity of hydrogen 7.3 times of air. It also has higher transfer co-efficient . Its ability to transfer heat through forced convection is about 75% better than air. Density of hydrogen is approx. 7/14 of the air at a given temperature and pressure. This reduces the windage losses in high speed machine like turbo-generator. Increasing the hydrogen pressure the machine improve its capacity to absorb & remote heat. Relative cooling properties of air and hydrogen are given below :-
1) Elimination of fire risk because hydrogen will not support combustion.
2) Corona discharge is not harmful to insula ? since oxidation is not possible.
3) Smooth operation of machine in view of vertical elimination of wind age noise & the use of heavy gas light enclosure and dirty proby casing.
At pressure 0.035 atm. of hydrogen heat carrying capacity is 1. But at 2.0atm. of hydrogen heat carrying capacity is 1.95 to overcome the serious possibility of hydrogen explosion with in the machine and to ensure the safety of operation purity of hydrogen on the generator. Casing must be maintained as high as possible. The purity of hydrogen should be 98% above but should not be less than 98% . In case of hydrogen purity drops below 98% an alarm is provided.
b) HYDROGEN DRYERS : Two nos. of dryers are provided to absorb the hydrogen in the Generator. Moisture in this gas is absorbed by silica gel in the dryer as the absorbed gas passes through it. The satural of silica gel is indicated by change in its color from blue to pink. The silica gel is reactivated by heating. By suitable change over from drier to the other on un-interrupted drying is achieved.
c) HYDROGEN FILLING SYSTEM : The filling operation is carried out in two steps.
1) Scavenging the air by CO2 with hydrogen.
Before filling the hydrogen at a pressure of 2 atm. In the machine it is necessary to store : - at least 18 cylinders of 20 Kg. CO2 & 48 cylinders of hydrogen.
The electric power Generators require direct current excited magnets for its field system. The excitation system must be reliable, stable in operation and must response quickly to excitation current requirements. When excitation system response is controlled by fast acting regulators, it is chiefly dependent on exciter. Exciter supply is given from transformer and then rectified.
(A) Function of excitation system : The main function of excitation system is to supply required excitation current at rated load condition of turbo Generator. It should be able to adjust the field current of the Generator, either by normal controller automatic control so that for all operation & between no load and rated load. The terminal voltage of the system machine is maintained at its value. The excitation system makes contribution improving power system stability steady state condition. The excitation system that are commonly termed quick response system and have following principal feature :- Exciter of quick response & high voltage of not less than 1.4 times the rated filed voltage and nominal exciter response of minimum 0.5.
(B) Type of excitation system : There have been many developments in excitation system design. There has been continue reach among the design and the use alike from improving the excitation system performance. The ultimate is to achieve stability; accuracy etc. the modern excitation system adopted presently on BHEL make turbo-generator. I. Conventional DC excitation system . Brushes excitation system.
STATIC EXCITATION SYSTEM
In KTPS static excitation system is provided it mainly consists of the following :-
1) Rectifier transformer.
2) Nos. of thyristor converters.
3) An automatic voltage regulator(AVR).
4) Field suppression equipment.
5) Field flashing equipment.
GENERAL ARRANGEMENT : In the excitation system the power required for excitation of Generation are tapped from 11 KV bus ducts through a step down rectifier transformer. After rectification in thermistor, converter, the DC power is fed to the Generator field winding through a field breaker. The AVR control the o/p from thyristor converter by adjusting the firing angle depending upon Generator voltages. The field flashing system facilitates initial built up of the Generator voltage from the static AC or DC supply.
(I) RECTIFIER TRANSFORMER : This transformer steps down the bus voltage 11 KV to 640 V and has a rating of 1360 KVA. It is dry type, it is however provided with current relays and two temperature sensors.
(II) A THYRISTOR CONVERTOR : The thyristor panel and are intended for controlled rectification of AC Input power. 6. Thyristor converter are connected in parallel each rates for continuous current o/p of 20 % of the rated capacity i.e. 20 % reserve. Each thyristor converter consists of 6 thyristor connected in 3-3 , full wave, 6-pulse bridge from and they are cooled by fans provided with a fuse for protection against short circuit.
(III) AUTOMATIC VOLTAGE CONTROLS : The AVR is a transistorized thyristor controlled equipment with very fast response. The AVR is also having provision of stator and rotor currents limits and load angle limits for optimum utilization of lagging and leading reactive capacities of generator.
(IV) FIELD SUPRESSION EQUIPMENT : The field equipment consists of a field breaker with discharge resistors. The field breakers have 4 main breaking contacts and two discharge contacts, which close before main contact break.
(a) A very fast response.
(b) Extremely reliable in view of static components.
(c) Low maintenance cost.
(d) High efficiency.
(e) Fast field suppression through field and discharge resistance as well as through thyristor bridge, feeding the Generator field.
After bringing the speed to operation speed say 3000 r.p.m. , the voltage is slowly built up with the help of excitation system. This action is taken for synchronizing the Generator.
(A) SYNCHRONIZING : For synchronizing the Generator to the grid system 5 condition of equality have to be satisfied. These are (I)_Voltage (II) Frequency (III) Phase displacement (IV) Phase sequence (V) Wave form. Wave form and phase sequence of the Generator are determined at the design of each connection SYNCHRONIZING of the generator.
(B) MACHINE CONNECTED TO INFINITE BUS : While separating a machine in parallel with grid we will have two condition:- (a) Any increase in the power input of the Generator increase its share of electrical loads (b) any excitation in the excitation of Generator increases its of relative load.
(A) Generator ( 110 MW) : Type t.g.p. 234602 h rating : continuous apparent o/p : 137,500 kva active o/p 710,000 kw power factor a ; 0.8 (lagging) rated voltage 1000V +5% rated:
current 7220 A , critical speed : 3000 r.p.m.frequency 50 Hz. Phase connection : double star , No. of terminals : 6 . Main dia. of slip ring : 420 . Max. O/p with H2 cooler including DC component : 9.2 (peak) inherent voltage regulation : 39% efficiency of turbo-Generator including 0.5.
Loads 100 75 80 25
% Loads 100 75 80 25
At 0.8 pf lag 98.32 % , 98.29% 98% 97.84%
At unity pf 98.8% 98.76% 98.52% 97.56%
Reactance : Informative.
HYDROGEN COOLER :
Nos. of elements : 6
Cooling medium : Water, H2 at 2 ATM.
Discharge losses : 1500 KW.
Quantity of H2 : 30 M3/ sec.
Quantity of water Temp : 34oC,
Cooling cold H2 Temp. : 400C
How resistance(H2 side) : 12 mm. of peak.
Inherent voltage regulation : 39%
Short circuit ratio : 0.5%.
Type : HC-WLL-BS/C46.
(C)Generator Brushes :-
Number : 42
Size : 25x32 mm.
Grade : HM 6R.
Turbine is a machine in which a shaft is rotated steadily by impact or reaction of current or stream of working substance ( steam , air , water, gases etc) upon blades of a wheel. It converts the potential or kinetic energy of the working substance into mechanical power by virtue of dynamic action of working substance. When the working substance is steam it is called the steam turbine.
PRINCIPAL OF OPERATION OF STEAM TURBINE
Working of the steam turbine depends wholly upon the dynamic action of Steam. The steam is caused to fall in pressure in a passage of nozzle: doe to this fall in pressure a certain amount of heat energy is converted into mechanical kinetic energy and the steam is set moving with a greater velocity. The rapidly moving particles of steam, enter the moving part of the turbine and here suffer a change in direction of motion which gives rose to change of momentum and therefore to a force. This constitutes the driving force of the machine. The processor of expansion and direction changing may occur once or a number of times in succession and may be carried out with difference of detail. The passage of steam through moving part of the commonly called the blade, may take place in such a manner that the pressure at the outlet side of the blade is equal to that at the inlet inside. Such a turbine is broadly termed as impulse turbine. On the other hand the pressure of the steam at outlet from the moving blade may be less than that at the inlet side of the blades; the drop in pressure suffered by the steam during its flow through the moving causes a further generation of kinetic energy within the blades and adds to the propelling force which is applied to the turbine rotor. Such a turbine is broadly termed as impulse reaction turbine.
The majority of the steam turbine have, therefore two important elements, or Sets of such elements . These are (1) the nozzle in which the system expands from high pressure end a state of comparative rest to a lower pressure end a status of comparatively rapid motion.
(2) The blade or deflector , in which the steam particles changes its directions and hence its momentum changes . The blades are attach to the rotating elements are attached to the stationary part of the turbine which is usually termed
The stator, casing or cylinder.
Although the fundamental principles on which all steam turbine operate the same , yet the methods where by these principles carried into effect very end as a result, certain types of turbine have come into existence.
1. Simple impulse steam turbine.
2. The pressure compounded impulse turbine.
3. Simple velocity compounded impulse turbine.
4. Pressure-velocity compounded turbine.
5. Pure reaction turbine.
6. Impulse reaction turbine.
TECHNICAL DATA OF 110 MW TURBINE
The main technical data of 110 MW turbine is given below:
1. Rated output : 110 MW.
2. Economic output : 95 MW.
3. Rated speed : 3000 rpm
4. Direction of rotation viewing from : Clockwise
the front bearing pedestal.
5. Rated steam pressure before : 130 ata
6. Maximum steam pressure before : 146 ata
7. Rated temperature of steam before : 535oC
the stop valve.
8. Maximum temperature of steam before : 545oC
the stop valve.
9. Rated pressure of steam : 31.6 ata
10.Rated pressure of steam before : 35 ata
11.Rated Temp. of steam before : 535oC.
12.Maximum Temp. of steam before : 545oC.
13.Informative heat flow at the economic: 2135 K cal/Kwh
14.Informative heat rate at the rated :2152.5 K Cal/Kwh.
15.HP Cylinder :2 row carts wheel +8 moving wheels
16.MP Cylinder :12 moving wheels.
17.LP cylinder :4 moving wheels of double row design.
18.Quantity of oil for first filling :1800 liters.
for the turbine.
TECHNICAL DATA OF 210 MW TURBINE
Rated Output : 210 MW.
Rated Speed. : 3000 rpm.
Main steam pressure. : 150 Kg./Cm2
Main steam temperature. : 535oC.
Reheat steam temperature. : 535oC.
Weight of turbine. : 475 T approx.
Overall length. : 16.975 Mtrs.approx.
Single flow HP turbine with 25 reaction stages.
Double flow IP turbine with 20 reaction stages per flow.
Double flow LP turbine with 8 reaction stages per flow.
2 main stop & control valves. 2 steam check valve in CRH.
2 reheat stop & control valves,. 2 bypass stop & control valve.
At KTPS there are 2x110 MW turbines installed for unit 1 & 2 and 3 210 MW turbines installed for units 3, 4 & 5, one 195 MW turbine installed for unit 6( Under final stage of construction & generation of power is expected in August, 2003).
Description of 210 MW Steam Turbine :
1)Steam flow :
210 MW steam turbine is a tandem compound machine with HP, IP & LP parts. The HP part is single flow cylinder and HP & LP parts are double flow cylinders. The individual turbine rotors and generator rotor are rigidly coupled. The HP cylinder has a throttle control. Main steam is admitted before blending by two combined main stop and control valves. The HP turbine exhaust (CRH) leading to reheated have tow swing check valves that prevent back flow of hot steam from reheated, into HP turbine. The steam coming from reheated called HRH is passed to turbine via two combined stop and control valves. The IP turbine exhausts directly goes to LP turbine by cross ground pipes.
2) HP Turbine :
The HP casing is a barrel type casing without axial joint. Because of its rotation symmetry the barrel type casing remain constant in shape and leak proof during quick change in temperature. The inner casing too is cylinder in shape as horizontal joint flange are relieved by higher pressure arising outside and this can kept small. Due to this reason barrel type casing are especially suitable for quick start up and loading.
The HP turbine consists of 25 reaction stages. The moving and stationary blades are inserted into appropriately shapes into inner casing and the shaft to reduce leakage losses at blade tips.
3) IP Turbine :
The IP part of turbine is of double flow construction. The casing of IP turbine is split horizontally and is of double shell construction. The double flow inner casing is supported kinematically in the outer casing. The steam from HP turbine after reheating enters the inner casing from above and below through two inlet nozzles. The centre flow compensate the axial thrust and prevent steam inlet temperature affecting brackets, bearing etc. The arrangements of inner casing confines high steam inlet condition to admission branch of casing, while the joints of outer casing is subjected only to lower pressure and temperature at the exhaust of inner casing. The pressure in outer casing relieves the joint of inner casing so that this joint is to be sealed only against resulting differential pressure.
The IP turbine consists of 20 reaction stages per flow. The moving and stationary blades are inserted in appropriately shaped grooves in shaft and inner casing.
4) LP Turbine :
The casing of double flow type LP turbine is of three shell design. The shells are axially split and have rigidly welded construction. The outer casing consist of the front and rear walls , the lateral longitudinal support bearing and upper part.
The outer casing is supported by the ends of longitudinal beams on the base plates of foundation. The double flow inner casing consist of outer shell and inner shell. The inner shell is attached to outer shell with provision of free thermal movement.
Steam admitted to LP turbine from IP turbine flows into the inner casing from both sides through steam inlet nozzles.
The utility boilers are large capacity steam generators used purely for the electrical power generation. In boiler heat energy is released from the combustion of fossils fuel and heat is transferred to different fluids in the system and a part of its is lost or left out as unutilized. It is therefore essential to study. The general principal of heat transfer for understanding the design as well as the behavior of boiler during different condition of operation.
Heat transfer modes
There are three modes of heat transfer viz. conduction, convection and radiation, one or more of these modes for which heat source should be at higher temperature than the receiver transfers heat energy hot surface to a heat recover.
Conduction is the heat transfer from one part of body to another part of the same body or from one body to another in physical contact without appreciable displacement of the particles of the body.
Convection is the transfer of heat from one point to another within a fluid by mixing of one part with another due to the movement of the fluid. When the movement of fluid is caused solely by the differences in density resulting from temperature differences in density resulting from temperature differences within fluid.
Radiation is the transfer of heat energy from one body to another by electromagnetic waves which can travel even through vacuum when radiation impinges on a body, some of the radian energy will re-radiated, some of it will be transmitted through the body and remainder will be absorbed.
Heat transfer surface arrangement :
There are three general kinds of arrangements of heat transfer surfaces as the Relative flow of fluid in concern. They are paralleled flow, counter flow and cross flow. In parallel flow both the fluids enter at the same relative physical location with respect to heat transfer surface. Resulting rapid rise in temperature. In counter flow , the two fluids enter at opposite ends of the heat transfer surface and flow in opposite direction over the surface resulting sudden rise in temperature. In cross flow the flow paths of the two fluids are perpendicular to each other resulting gradual rise in temperature.
Heat transfer sections :
The various heat transfer section of a boiler can be grouped as follows :-
The furnace design influenced by the fuel, surface , plain area
(13.86 x 10.59) volumetric ( 5470 m3) and burner clearance. The major fuels used in the steam generation are coal , oil and gas.
Super heater and reheated :
The location of super heater and reheat is almost standard based on the past xperience. Typical arrangement of super heater and re-heater is indicated in the elevation drawing.
This is also convection heat transfer section located in a relatively cooler gas temperature zone and preheats the water entering the drum. The inlet temperature should not be less than 140oC from the low temperature corrosion point of view. The outlet temperature should be 35-45oC lower than the saturation point to avoid the streaming tendency in the economizers.
d) Air Heaters :
The technical developments of the air pre-heater provide regenerative type air heaters. The air temperature required for drying in the case of coal fired boiler decided the size of the air heaters.
Material selection for heat transfer surfaces
The selections of the heat transfer surfaces are being done on the basis of the temperature of the mid metal temperature as well as the outer surface temperature complete water wall system is provided with only carbon steel where as super heater and re-heater are provided with whereas grades of ASTM specification.
In natural circular system, water delivered to steam generator from feed header which are at a temperature well below the saturation value corresponding to that pressure. Entering the economizer, it heated to much greater the saturation temperature from economizer the water enter the drum and thus joins the circulation system through down covering water wall tubes. In water wall tubes a part of the water is converted to steam due to boiler and the mixture flows back to the drum on the basis of the thermo siphon principal. In the drum, the steam is separated out through the steam separators and passed to the super heater. After the super heater when the steam temperature becomes high and pressure upto 150 Kg. steam is allowed to enter the turbine to convert potential energy to kinetic energy.
TECHNICAL SPECIFICATION OF BOILER (2x110MW UNITS)
1.Type : Direct fired, natural circulation balance draft water tube boiler.
2. No. of Units. : Two.
3.Make : BHEL.
4.Capacity. : 375 tonnes per hour.
5.Steam Pressure. : 139 Kg./Cm2
6.Efficiency : 86.6 %.
7.No. of fans in service.
a) ID fans. : 2 Nos.
b) FD fans. : 2 Nos.
c) PA fans. : 2 Nos.
d) Seal Air fan. : 1 No.
e) Scanner Air fan. : 1 No.
f) Igniter fan. : 1 No.
8. Steam Temperature : 540oC.
9. No. of coal mills in : 3 Nos.
10.No. of soot blowers : 70 Nos.
Type, : Slack Coal.
Quantity consumed : 3074 tonnes per day.
Type of handing. : Conveyor.
Ash disposal : Wet system.
Type. : HSD and fuel oil.
Quantity. : a) HSD – 5520 KL per year. *
b) Furnace Oil : 28800 KL per year. *
No. of chimney / stack.: 1 / 2.
Height of Chimney. : 180 Meters.
Volume of flue Gas/ : 198 M3/ Sec.
Temp. of flue gas. : 140oC.
ESP : One for each unit.
Boilers are tangentially fired, balance draft, natural circulation , radiant type, dry bottom with direct fired pulverized coal from bowl mills. They are designed for burning low grade coal with high ash content. Oil burners are located between coal burners for flame stabilization. Pulverized coal is directly fed from the coal mills to the burners at the four corners of the furnace through coal pipes. The pulverized fuel pipes from the mills to the bunkers are provided with basalt lined bends to reduce erosion and to improve the life of these pipes owing to poor grade of coal there is a high percentage of mill rejects. The mill rejects are conveyed in a sluice way to an under-ground tank. From this tank the mixture is taken to an overhead hydro-bin where water is decanted and the mill reject are disposed off by trucking. ESP with collection efficiency of 99.8% have been provided to reduce environmental pollution and to minimize induce draft fan wear. A multi-flue reinforced concrete stack with two internal flues has been provided.
Two boiler feed pumps each of 100 % capacity are driven by AC motor through hyd. coupling with scoop tube arrangement for regulating feed water pressure for each unit.
The air required for combustion is supplied by two forced draft fans.
For ensuring safe operation of boilers, furnace safe guard supervisory system (FSSS) of combustion engineering USA designed has been installed. This equipment systematically feed fuel to furnace as per load requirement.
The UV flame scanners installed at two elevation in each of the four corners of the furnace, scan the flame conditions and in case of unsafe working conditions but out fuel and trip the boiler and consequently the turbine. Turbine – boiler interlocks safe guarding the boiler against possibility furnace explosion owing to flame failure.
Facilities have been provided to simultaneously unload and transfer 10 light oil and 40 heavy oil tankers to the designated tanks. Oil preheating arrangement is provided on the tanks floors for the heavy oil tanks.
Superheated steam temperature is controlled by attemperation.
Re-heater steam temperature is primarily by tilting fuel burners through + 30o and further control if necessary is done by attemperation.
COAL HANDLING PLANT
It cam be called the heart of thermal power plant because it provided the fuel for combustion in boiler. The coal is brought to the KTPS through rails there are fourteen tracks in all for transportation of coal through rails. The main coal sources for KTPS are SECL (South Eastern Coalfields Limited), ECL (Eastern Coalfield Limited) and BCCL (Bharat Coking Coal Limited). Everyday 3 to 4 trains of coal are unloaded at KTPS. Each train consists of 58 wagons and each wagons consists of 50 tonnes of coal. The approximate per day consumption at KTPS is about 1400 metric tones. It costs approximate 2 crores of rupees per day including transportation expenses. The coal is firstly unloaded from wagon by wagon triplers then crushed by crushers and magnetic pulley and pulverized to be transformed to the boiler. The whole transportation of coal is through conveyor belt operated by 3-Ø Induction motor.
The coal handling plant can broadly be divided into three sections :-
1) Wagon Unloading System.
2) Crushing System.
3) Conveying System.
WAGON UNLOADING SYSTEM
Wagon Tripler :
It unloads the coal from wagon to hopper. The hopper, which is made of Iron , is in the form of net so that coal pieces of only equal to and less than 200 mm. size pass through it. The bigger ones are broken by the workers with the help of hammers. From the hopper coal pieces fall on the vibrator.
It is a mechanical system having two rollers each at its ends. The rollers roll with the help of a rope moving on pulley operated by a slip ring induction motor with specification:
Rated Output. : 71 KW.
Rated Voltage. : 415 V.
Rated Current. : 14.22 Amp.
Rated Speed. : 975 rpm.
No. of phases. : 3
Frequency. : 50 Hz.
The four rollers place themselves respectively behind the first and the last pair of wheels of the wagon. When the motor operates the rollers roll in forward direction moving the wagon towards the “Wagon Table”. On the Wagon table a limit is specified in which wagon has to be kept otherwise the triple would not be achieved.
Crusher House :
It consists of crushers which are used to crush the coal to 20 mm. size. There are mainly two type of crushers working in KTPS:-
Primary Crushers i.e. i) Rail crushers or ii) Rotary breaker.
Secondary Crushers. i.e. Ring granulators.
Primary Crushers :
Primary crushers are provided in only CHP stage 3 system , which breaking of coal in CHO Stage 1 & Stage 2 system is done at wagon tripler hopper jail upto the size (-) 250 mm.
Roll Crusher :
Type : 80” 5 A breaker.
Capacity : 1350 TPH Rates/ 1500 TPH Design.
Feed material : Rom Coal.
Feed size. ; (-) 1200 mm. (approx.)
End Product size : (-) 500 mm.
Motor rating. : 2 Nos. 125 KW , 100 rpm.
Crushers. : 225.
Rotary Breaker :
Type : 12’ x 21o Rotary Breaker.
Capacity : 800 TPH Rated/ 1000 TPH Design.
Feed Material. : Coal with rejects.
Feed size. : (-) 0-500 mm.
End product size : (-) 0-200 mm.
Motor rating. : 125 HP, 1500 rpm.
Breaker rpm. : 12
Secondary Crusher :
Basically there are four ways to reduce material size : impact attrition , Shearing and Compression. Most of the crushers employ a combination of three crushing methods. Ring granulators crush by compressing accompanied by impact and shearing.
The unique feature of this granulator is the minimum power required for tone for this type of material to be crushed compared to that of other type of crushers.
Construction & Operation :
Secondary crushers are ring type granulators crushing at the rate of 550 TPH / 750 TPH for input size of 250 mm. and output size of 20 mm. The crusher is coupled with motor and gearbox by fluid coupling.
Main parts of granulator like break plates, cages , crushing rings and other internal parts are made of tough manganese (Mn) steel.
The rotor consists of four rows of crushing rings each set having 20 Nos. of toothed rings and 18 Nos. of plain rings. In CHP Stage 1 & 2 having 64 Nos. of ring hammers. These rows are hung on a pair of suspension shaft mounted on rotor discs.
Crushers of this type employ the centrifugal force of swinging rings stroking the coal to produce the crushing action. The coal is admitted at the top and the rings strokes the coal downward. The coal discharges through grating at the bottom. The spacing of the bar determines the maximum size of the finished product.
Stacker Reclaimer :
The stacker re-claimer unit can stack the material on to the pipe or reclaim the stack filed material and fed on to the main line conveyor. While stacking material is being fed from the main line conveyor via tripler unit and vibrating feeder on the intermediate conveyor which feds the boom conveyor of the stacker cum reclaimer. During reclaiming the material dis discharged on to the boom conveyor by the bucket fitted to the bucket wheel body and boom conveyor feeds the material on the main line conveyor running in the reverse direction.
Conveyor belt Specification of Stacker / Reclaimer :
Belt width. : 1400 mm.
Speed. : 2.2 m/second.
Schedule of motor: All 3-Ø induction motors.
Bucket wheel motor : 90 KW.
Boom Conveyor motor : 70 KW.
Intermediate Conveyor 90 KW.
Boom Housing Motor : 22 KW.
Slewing assembly. 10 KW.
Travel Motor. 7.5 KW.
Vibrating Feeder. 2x6 KW.
Total installed power. 360 KW.
Conveyor Specification :
Capacity. 1) 1350 tonne per hour.
2) 750 tonne per hour.
No. of conveyor. : 38
Horizontal length.: 28 meters.
Angle of induction. As per conveyor profile drg.
Lift(M) (approx.) : Variable to suit the system.
Belt width. : 1400 mm.
specification of conveyor motor.
Plow feeders :
This structure is erected to serve the purpose of storage. Under ground machines are installed known as plow feeder machines.
These machines collect the coal from conveyor and drop it to the other from one conveyor with the help of jaws and this coal is taken to huge erected structure from where the coal falls to the ground. Jali chutes are used to prevent dust.
ASH HANDLING PLANT
This plant can be divided into 3 sub plants as follows :-
1) Fuel and Ash Plant.
2) Air and Gas Plant.
3) Ash Disposal and & Dust Collection Plant.
Fuel and ash plant
Coal is used as combustion material in KTPS, In order to get an efficient utilization of coal mills. The Pulverization also increases the overall efficiency and flexibility of boilers. However for light up and with stand static load , oil burners are also used. Ash produced as the result of combustion of coal is connected and removed by ash handling plant. Ash Handling Plant at KTPS consists of specially designed bottom ash and fly ash in electro static precipitator economizer and air pre-heaters hoppers.
Air & Gas Plant
Air from atmosphere is supplied to combustion chamber of boiler through the action of forced draft fan. In KTPS there are two FD fans and three ID fans available for draft system per unit. The air before being supplied to the boiler passes through pre-heater where the flue gases heat it. The pre heating of primary air causes improved and intensified combustion of coal.
The flue gases formed due to combustion of coal first passes round the boiler tubes and then it passes through the super heater and then through economizer . In re-heater the temperature of the steam (CRH) coming from the HP turbines heated with increasing the number of steps of re-heater the efficiency of cycle also increases. In economizer the heat of flue gases raises the temperature of feed water. Finally the flue gases after passing through the Electro-Static Precipitator is exhausted through chimney.
Ash Disposal & Dust Collection Plant
KTPS has dry bottom furnace. Ash Handling Plant consists of especially designed bottom and fly ash system for two path boiler. The system for both units is identical and following description is applied to both the units the water compounded bottom ash hopper receives the bottom ash from the furnace from where it is stores and discharged through the clinker grinder. Two slurry pumps are provided which is common to both units & used to make slurry and further transportation to ash dyke through pipe line.
Dry free fly ash is collected in two number of 31 fly ash hoppers which are handled by two independent fly ash system. The ash is removed from fly ash hoppers in dry state is carried to the collecting equipment where it is mixed with water and resulting slurry sump is discharged.
Scope & Principle of Operation
For general mankind , today an Eco friendly industry is must. As far as air pollution is concerned now a days various flue gases filter are there in service. The choice depends on the size of suspended particle matter. These filters are E.S.P. Fabric filter high efficiency cyclone separations and sitelling room. Fop fly ash , where the particle size vary from 0.75 microns to 100 micron use gradually use E.S.P. to purify the flue gases due to its higher efficiency & low running cost etc. In an ESP the dust lidder gas is passed through an intense electric field, which causes ionization of the gases & they changed into ion while traveling towards opposite charged electrode get deposited as particles and thus dust is electric deposited an electrode creating the field. It is continuous process.
Now a days micro-processor based intelligent controllers are used to regulate the power fed to the HVR. The controls the firing / ignition angle of the thrysters connected in parallel mode. Input out waves of the controller and HVR are also shown above, which clearly indicates that average power fed to ESP field can be controlled by variation of the firing angle of thyristers.
The output of controller with respect to time is also controlled by microprocessor, so that ESP operation is smooth and efficient . The chars is as shown :
As can be seen in the event of spark between electrode the output of controller is reduced to zero for few millisecond for quenching the spark. Controller also takes place care of fault in KVR and gives a trapping and non-trapping alarm as per the nature of fault.
HIGH VOLTAGE RECTIFIER TRANSFORMER
HVR receives the regulated supply from controller. It steps upto high voltage rectifier. The D.C. supply is fed to E.S.P. field through its negative bushing. The positive bushing so connected to earth through small resistance which forms a current feed back circuit. A very high resistance column is also connected with negative bushing . It forms the voltage feed back circuit. These two feedback are used in the controller for indication and control purpose.
The field consists of emitting and collecting electrodes structure which are totally isolated from each other and hanging with the top roof of field. The emitting is also isolated from the roof through the support insulators which are supporting the emitting electrode frame works and also the supply to these electrodes is fed through support insulators. The collecting electrodes are of the shape of flat plates. By several similar plates which the emitting electrodes are of the shape of spring. Strong on the emitting frame work with the help of hooks in both the ends.
The ash depositing on these electrode is rapped down by separate wrapping mechanism happens at the bottom of the field. From these hoppers ash is evacuated by ash handling system and dispose to the disposal area. The wrapping system is automatically controlled with the help of the programmable metal controller, located in the ESP auxiliaries control panels. The bottom of the hopper is heated up by two avoid any formation to wet mass of fly ash specially during rainy season.
The heating effect help the dry ash to flow freely during evacuation. Heaters are controlled with the help of thermostat.
WATER TREATMENT PLANT
The principle problem in high pressure boiler is to control corrosion and steam quality. Internal corrosion costs power station crores of rupees in repair without strict control impurities in steam also form deposit over turbine blades and nozzles. The impurities present in water are as follows :-
1) Un-dissolved and suspended solid materials.
2) Dissolved slats and minerals.
3) Dissolved gases/
4) Other minerals ( oil, acid etc.).
2. a) Turbidity & Sediment.
c) Micro Biological.
d) Sodium & Potassium Salt.
e) Dissolved Sales Minerals.
3. a) O2gas.
b) CO2 gas.
In this plant process water is fed from all these dissolved salts. Equipment for demineralization cum softening plant is supplied and erected by M/s. Wanson (India) Ld., Pune. This plant consists of two streams each stream with activated carbon filter, weak acid , cation exchanger and mixed bed exchanger. The filter water to DM plant through 250 dia. header from where a heater top off has been taken to softening plant. Two filtered water booster pumps are provided on filtered water line for meeting the pressure requirement in DM Plant.
Sodium Sulphate solution of required strength is dosed into different filtered water by mean of dosing pump to neutralize chlorine prior to activated carbon filter. When water passed an activated carbon filter will remove residual chlorine from water. Provision is made for back washing the activated carbon filter. When pressure drop across filter exceeds a prescribed limit from the activated carbon filter the works acid cation unit. The deception water the weak base anion exchanger unit water then enters de-gasified unit where free CO2 is scrubbed out of water by upward counter flow of low pr. air flow through degasified lower and degassed water is pumped to strong base exchanger ( anion exchanger).
Arrangement for dosing ammonia solution into de-mineralized water after mixed bed unit has been provided p+1 correction before water is taken in de-condensate transfer pump the DM water to unit condensor as make up.
The softening plant is plant designed to produce 100M3 of the softened water per stream. It is used for bearing cooling.
Circulating water pump house has pumps for condensing the steam for condensor. Five pumps are used for condensing Unit No.1 & 2 and after condensing this water is discharged back into the river.
Each pump has capacity of 8275 M3/Hr, and develop pressure about 1.94 Kg./Cm2.
Three seal water pump are used for sealing circulating water pump shaft at pr. 4.5 kg./cm2.
Two pump for unit 1 & 2 with one stand by is used for supplying raw water to chlrofied chemical dosing is tone between and chlorified water is taken through main line. From main line water passes through filter bed to filter the water. Chlorified water is pumped to 42 m elevation by two pumps of capacity 270 M3/Inch at discharge pressure of 6.9 Kg./Cm2. At 42 M elevation the water is stored in tank and used for cooling the oil coolers and returned back to river. Oil coolers are situated on ground and there are no. of tress for each unit.
B.C.W. PUMP HOUSE
Filter water after demineralization is used for bearing cooling from BCW pump house after passing through strainer and heat exchanger it enters at 30-32oC and leave exchanger at 38oC. The raw water used in ash handling plant and remaining quantity is stored in sumps of BCW Pump House. From here the water is pumped to CW Pump by TWS (Traveling water screens) pumps are run by motors of 90 KW and has a capacity of 240 Cum/hr/pump at pressure of 5 kg/cm2.
BCW here stand for water used for cooling oil used for cooling the bearing. In CW pump house water is discharged from nozzle and impinged for traveling water screens for cleaning it.
MAIN CONTROL ROOM
In control room various controls are provided simultaneously various measurement are made various relays are provided here. Instrumentation Limited Kota is major supplier of apparatus.
There is one unit control from which two adjacent unit of 110 MW each can be controlled. In addition are local panels at the boilers, turbo sets and boiler feed pumps. The operation of unit is basically controlled from unit control room.
The operation of various rents and chain are done locally as per requirement. The unit control room has a set of parameters panel for indicating or recording parameter of boilers or turbo sets.
The parameters recorded in control room included per pr. and temp. of line steam, reheat steam , feed water, fuel oil flow, mill outlet temp. ,mill differential , turbine speed, control valve operation, turbine shaft , axial shaft , back pressure in condenser , metal temperature etc. There is a data logger to ensure accurate lagging of essential data.
The VCB also control panel for one generator and contains exciter synchronizing arrangement. The unit control room also houses most of electronic regulator , relay, recorders and other devices in near side of room.
The scheme of control and instruction is provided to control the parameters and safe operation of equipment. Automatic control is provided for combustion for feed water regulation and reheat temp. The combustion control is designed to inlet maintain the desired steam pressure at turbine only variation thereof utilized to very fuel input to the boiler w.r.t. steam pressure. Ratio steam flow maintained automatically.
The feed water regulation is based on impulses from drum level, feed water flow to boiler and steam flow for the boiler.
Super heater temp. counted with feed water spray. The furnace draft control of draft fan. The boiler oil system is provided with itself control for ignition control and also provided with safety interlock to prevent operation under low oil pressure and temperature.
1. FAN CONTROL DESK :
i) Induced draft fan ( 3 Nos.) at full load and 2 Induce Draft Fans
ii) Forced draft fan ( 2 Nos.).
iii Primary Air Fan (3 Nos.) at full load.
i) Furnace Pressure (- 5 to 10 wcl).
ii) Primary Air Header Pressure (750-800 mm. level wcl.)
Wind box pressure or wind box differential pressure.
Fuel Control Desk :
1) Coal, oil flow.
2) Oil pressure.
3) Temp. of mill (inlet & outlet).
4) Flow of air.
5) Differential Pressure of mill.
STEAM & WATER DESK:
1) Drum Level Control
2) Flow of steam & water.
3) Pressure of Steam & Water.
4) Temp. of steam and water.
TURBINE DESK :
1) Pressure Control.
2) Load Control.
3) Speed Control.
4) Effectors, Control Values, Stop Values, Deaerators.
GENRATOR CONTROL PANEL :
1) Voltage Current MVAR.
2) Stator Rotor Temp.
3) For Stator Cooling (a) H2 pressure. b) H2O pressure.
1. Field Protection.
2. Pole Slipping.
3. Plane Overload Protection.
4. Inter-turn Fault
5. Negative Phase Sequence Protection.
6. Reverse Power Protection.
7. Forward Power Protection.
8. Under Frequency & Over Frequency Protection.
9. Generator Voltage Protection.
10. Rotor Earth Fault Protection.
It is most important electrical equipment of many generating station. Tripping of even a generating unit may cause overloading of associated machines and even to system un-stability . The basis function of protection applied to generator is to reduce voltage to minimum by rapid discrimination clearance of faults. Unlike other apparatus the opening of C.B. to isolate faulty generator is not sufficient to prevent future damage. Since generator would continue to supply power to stator winding fault , until its excitation is suppressed. It is, therefore, necessary to open field stop fuel supply to prime mover & in some case breaking also.
SALIENT FEATURE OF K.T.P.S.
1. LOCATION Sakatpura, Kota.
A) 1ST Stage. 2x110 MW.
B) 2nd Stage. 2x210 MW.
C) 3rd Stage. 1x210 MW.
D) 4th Stage. 1x195 MW.(to be commissioned in August 2003).
3. SOURCE OF WATER. Chambal River.
a) type. tangentially fired natural circulation, balance draft , direct fired radiant reheat, water tube boiler.
b)No. of units. 6
c) Max. efficiency. BHEL (86.6 + 1) %
d) Capacity. 375 tonnes 1 Hr.
e) Steam Pressure 139 Kg./cm2
f) Steam Temp. 540oC,
g) No. of draft fans in i) FD fans 2 Unit ( Each boiler)
Service. ii) ID fan 2 Unit ( Each boiler ).
h) No. of Air fans in Service.
i) Primary 2 Unit.
ii)Seal Air fan. 1 Unit.
iii) Scanner. 1 Unit.
i) No. of coal mills in service. 3 Unit.
j) No. of Soot blower in 68
k) No. of oil burners. 8
5. Fuels :
i) Type. Stack Coal.
ii) Calorific Value. 4450 K.Cal./Kg.
iii) Qty. Used. 3074 tonnes per day.
iv) Ash contents. 40%
v) Sulphur contents. 0.5%.
vi)Type of Handling. Belt Conveyor.
vii) Type of disposal of Ash.
a) Fly ash. Wet
b) Bottom Ash. Wet .
i) Type. HSD & Furnace Oil.
ii) Qty. used. As per requirement & draft conditions.
The first phase of practical training has proved to be quiet fruitful. It provided an opportunity for encounter with such huge machines like wagon tippler .110 MW & 210 MW turbines and generators.
The architecture of the power plant the way various units are linked and the way working of whole plant is controlled make the student realize that engineering is not just learning the structured description and working of various machines, but the greater part is of planning proper management.
It also provides an opportunities to lean low technology used at proper place and time can cave a lot of labour e.g wagon tippler(CHP).
But there are few factors that require special mention. Training is not carried out into its tree sprit. It is recommended that there should be some project specially meant for students where presence of authorities should be ensured. There should be strict monitoring of the performance of students and system of grading be improved on the basis of work done.
However training has proved to be quite fruitful. It has allowed an opportunity to get an exposure of the practical implementation to theoretical fundamentals.