Anpara Thermal Power Plant Report

A PROJECT REPORT ON

UTTAR PRADESH RAJYA UTPADAN NIGAM LIMITED (U.P.R.V.U.N.L.)

ANPARA THERMAL POWER PLANT ELECTRICAL MAINTENANCE DIVISION (E.M.D.) –‘B’ TPS

SUBMITTED TO:

SUBMITTED BY:

NIKHIL CHATURVEDI

AAYUSH SRIVASTAVA

EXECUTIVE ENGINEER

12/EE/89

HR & TRAINING DEPARTMENT

B.TECH. (EE), IIIrd year

ATP, Anpara

N.I.T. DURGAPUR

CERTIFICATE

This is to certify that Mr. AAYUSH SRIVASTAVA doing B.Tech in Electrical Engineering, 3RD year from NATIONAL INSTITUTE OF TECHNOLOGY DURGAPUR, has completed his vocational training from Anpara Thermal Power Station, Anpara, Sonbhadra (U.P.) from 11.05.2015 to 10.06.2015. His area of training is EMD – I, ‘B’TPS, Anpara Thermal Power Station. During this period he has been punctual, sincere in his job & has undergone the learning process with responsibility and sense of purpose. He also bears a very good character. We wish him 'All the Best' for his bright future.

Executive Engineer EMD – I, ‘B’TPS ATP, ANPARA

Executive Engineer H.R. and Training Department ATP, ANPARA

CONTENTS •

Acknowledgement

•

Introduction to Anpara Power Project

•

Unit Overview

•

Thermal Power Plant Layout and Operation

•

Coal Handling Plant

•

Generators

•

Transformers

•

Switchgear

•

Switchyard

•

Electrostatic Precipitator

ACKNOWLEDGEMENT A summer project is a golden opportunity for learning and selfdevelopment. I consider myself very lucky honoured to have so many wonderful people lead me through in completion of this project.

My grateful thanks to Er. Akash Singh, Executive Engineer and Mr Anil Kumar, Assistant Engineer of EMD-I, ‘B’TPS, Anpara who in spite of being extraordinarily busy with his duties, took time out to hear, guide and keep me on the correct path. I do not know where I would have been without him. A humble ‘Thank you sir’.

Last but not the least there were so many who shared valuable information that helped in the successful completion of this project.

Aayush Srivastava Electrical Engineering, 3rd year, National Institute of Technology Durgapur

ANPARA THERMAL POWER STATION

PLANT LOCATION The Anpara Power Plant is located near village Anpara on the bank of Rihand reservoir in the district of Sonebhadra (Uttar Pradesh). It is about 34 km from Rihand Dam on Pipri-Singrauli road and about 200 km from Varanasi. Varanasi is connected by air/rail and road route from other major cities.

OPERATIONS There are in total seven operational units, all of which are coal-fired thermal power stations. The machinery for the Anpara A (3 units) are from Bharat Heavy Electricals Limited. Anpara B (two units) from Toshiba Corporation, Japan. Machinery for Anpara C were sourced by Lanco power from Dongfang Electric Company (China). Machinery for Anpara D is sourced from BHEL. The coal to all these units is fed from Kharia, Kakri and Beena open coal mines of NCL by company owned freight trains, a merry go round system maintained by UPRVUNL and previously on roads by Dumpers.

STAGES

STAGE

UNIT NO.

INNSTALLED CAPACITY

DATE OF COMMISSIONING

STATUS

REMARKS

Anpara A

1

210MW

1987 January

Running owned by UPRVUNL

Anpara A

2

210MW

1987 August

Running owned by UPRVUNL

Anpara A

3

210MW

1989 March

Running owned by UPRVUNL

Anpara B

4

500MW

1994 March

Running owned by UPRVUNL

Anpara B

5

500MW

1994 October

Running owned by UPRVUNL

Anpara C

6

600MW

2011 December

Running owned by Lanco Infratech

Anpara C

7

600MW

2012 January

Running owned by Lanco Infratech

Anpara D

8

500MW

2015 March

Running owned by UPRVUNL

Anpara D

9

500MW

2015 April

Running owned by UPRVUNL

The coal to all these units is fed from Kharia, Kakri and Bina open coal mines of NCL, by means of a marry-go-round system, maintained by UPRVUNL.

UNIT OVERVIEW Following figure is the Unit Overview of ‘B’ Anpara Thermal Power Plant which is unit 4 and unit 5 generates 2 X 500 MW. It means these units two machine of 500 MW. Following figure is the Overview of one unit.

Figure of Unit Overview

IMPORTANT TERM AND THEIR FUNCTION 1). C.E.P.(Conensate Exaction Pump):- It is used to pump the condensate water from condenser to L.P.H.S. through C.P.P. 2). C.P.P.(Condensate Polishing Plant):-It is used to polish the condensate water by the process of ion exchange and filtration of corrosion product. 3). L.P.H.S.(Low Pressure Heater System):- It heat the water at low pressure. The water is in liquid form. 4). Deaerator:- It is used to remove oxygen from the water. 5). B.F.P.(Boiler Feed Pump):- Boiler feed pump is used to feed water to steam generator boiler drum to desired pressure and temperature. i). T.B.F.P.(Turbo Boiler Feed Pump):- It work with the steam from Intermediate Pressure (I.P.) turbine exhast. ii). M.B.F.P.(Motorised Boiler Feed Pump):-It work with the motor as name specifies. 6). H.P.H.S.(High Pressure Heating System):- It feed the heat water at very high pressure. This provide the good mechanical properities at high temperture. 7). Boiler:- It is with the large number of tube running feed water in it and heated with burner. 8). Turbine:- It is parts where steam is flow through blades of turbine and make shaft to move. i).H.P.:- It work with heat pressure steam. ii). I.P.:- It work with Intermediate pressure steam. iii). L.P.:- It work with low pressure steam. 9). Generator:- Moving shaft work as mechnical energy and convert it to electrical energy by generator 10). Condenser:- It than convert the steam to the water. 11). E.S.P.(Electrostatic percipitator):- It used to filter the ash coming from the economizer to the chimney where dust is stick to anode. 12). F.D. Fan (Force Draft Fan):- It is use to provide atmospheric air to furnance. 13). P.A. Fan (Primary Draft Fan):- It is used to transfort coal from the mill to the furnance. 14). I.D. Fan (Induced Draft Fan):- It is used to Push the Flue Gas out from the chimneys.

UNIT OVERVIEW (2*500mw)

Anpara TPS is worked on the modified rankine cycle. In ‘B’TPS there are 2 units namely 4 & 5.The capacity of each unit is 500 MW Here outlet steam of L.P.TBN goes condenser where this steam condense & becomes condensate. Also there is a provision of makeup DM water the level. Condensate is extract from the condenser by CEP. There are three CEP in which one is in reserve & other two are working in position. CEP force the condensate to CPP for improving the quality of the condensate. After that this condensate goes to the LP heaters for initially heat up. There are three LP heaters. The outlet of 3rd LP heater goes to boiler feed, initially to the M-BFP & in running to the T-BFP discharge of T-BFP goes to HP-HTRS. There are four HP heaters and discharge of HP HTR 6B & 5B goes to the economiser which is in the boiler furnace. After economiser, feed water goes to the boiler drum where steam is collect on the upper portion & water on the lower portion which is circulated by BCP (3:1 in reserve). From boiler drum, steam is goes to the super heater where steam becomes super heat & after that goes to the HP TBN which of 4 stages. After that goes it to the re-heater, where it reheat & goes to IP TBN which of 5 stage. From IP TBN, steam goes to the LP TBN inlet where it expands & TBN convert heat energy to mechanical energy which is further converted into electrical energy by generator. Power is generated at 21 KV and is stepped up to 400kV by the Generator Transformer. Output from GT is used to power the Auxiliaries via the Station Transformer and the generator field circuit via the Excitation Transformer. Rest of power is sent to the switchyard for distribution.

THERMAL PLANT LAYOUT AND OPERATION Thermal Power Plant Layout :

The above diagram is the layout of a simplified thermal power plant and the below is also diagram of a thermal power plant.

Main parts of the plant are 1. Coal conveyor

2. Stoker

3. Pulverizer

4. Boiler

5. Coal ash

6. Air preheater

7. Electrostatic precipitator

8. Smoke stack

9. Turbine

10. Condenser

11. Transformers

12. Cooling towers

13. Generator

14. High - votge power lines

Basic Operation: A thermal power plant basically works onRankine cycle. Coal conveyor: This is a belt type of arrangement.With this coal is transported from coal storage place in power plant to the place near by boiler.

Stoker: The coal which is brought near by boiler has to put in boiler furnance for combustion.This stoker is a mechanical device for feeding coal to a furnace.

Pulveriser: The coal is put in the boiler after pulverization.For this pulverizer is used.A pulverizer is a device for grinding coal for combustion in a furnace in a power plant. Types of Pulverisers •

Ball and Tube Mill

Ball mill is a pulverizer that consists of a horizontal rotating cylinder, up to three diameters in length, containing a charge of tumbling or cascading steel balls, pebbles, or rods. Tube mill is a revolving cylinder of up to five diameters in length used for fine pulverization of ore, rock, and other such materials; the material, mixed with water, is fed into the chamber from one end, and passes out the other end as slime. •

Ring and Ball

This type consists of two rings separated by a series of large balls. The lower ring rotates, while the upper ring presses down on the balls via a set of spring and adjuster assemblies. Coal is introduced into the center or side of the pulveriser (depending on the design) and is ground as the lower ring rotates causing the balls to orbit between the upper and lower rings. The coal is carried out of the mill by the flow of air moving through it. The size of the coal particles released from the grinding section of the mill is determined by a classifer separator. These mills are typically produced by B&W (Babcock and Wilcox).

Boiler: Now that pulverized coal is put in boiler furnace. Boiler is an enclosed vessel in which water is heated and circulated until the water is turned in to steam at the required pressure. Coal is burned inside the combustion chamber of boiler. The products of combustion are nothing but gases. These gases which are at high temperature vaporize the water inside the boiler to steam. Sometimes this steam is further heated in a super-heaters higher the steam pressure and temperature the greater efficiency the engine will have in converting the heat in steam in to mechanical work. This steam at high pressure and temperature is used directly as a heating medium, or as the working fluid in a prime mover to convert thermal energy to mechanical work, which in turn may be converted to electrical energy. Although other fluids are

sometimes used for these purposes, water is by far the most common because of its economy and suitable thermodynamic characteristics.

Classification of Boilers Bolilers are classified as •

Fire tube boilers : In fire tube boilers hot gases are passed through the tubes and water surrounds these tubes. These are simple,compact and rugged in construction.Depending on whether the tubes are vertical or horizontal these are further classified as vertical and horizontal tube boilers.In this since the water volume is more,circulation will be poor.So they can't meet quickly the changes in steam demand.High pressures of steam are not possible,maximum pressure that can be attained is about 17.5kg/sq cm.Due to large quantity of water in the drain it requires more time for steam raising.The steam attained is generally wet,economical for low pressures.The outut of the boiler is also limited.

•

Water tube boilers: In these boilers water is inside the tubes and hot gases are outside the tubes. They consists of drums and tubes.They may contain any number of drums (you can see 2 drums in fig).Feed water enters the boiler to one drum (here it is drum below the boiler).This water circulates through the tubes connected external to drums.Hot gases which surrounds these tubes wil convert the water in tubes in to steam.This steam is passed through tubes and collected at the top of the drum since it is of light weight.So the drums store steam and water (upper drum).The entire steam is collected in one drum and it is taken out from there (see in laout fig).As the movement of water in the water tubes is high, so rate of heat transfer also becomes high resulting in greater efficiency.They produce high pressure , easily accessible and can respond quickly to changes in steam demand.These are also classified as vertical,horizontal and inclined tube depending on the arrangement of the tubes.These are of less weight and less liable to explosion.Large heating surfaces can be obtained by use of large number of tubes.We can attain pressure as high as 125 kg/sq cm and temperatures from 315 to 575 centigrade.

Super-heater : Most of the modern boliers are having superheater and reheater arrangement. Superheater is a component of a steam-generating unit in which steam, after it has left the boiler drum, is heated above its saturation temperature. The amount of superheat added to the steam is influenced by the location, arrangement, and amount of superheater surface installed, as well as the rating of the boiler. The superheater may consist of one or more stages of tube banks arranged to effectively transfer heat from the products of combustion.Superheaters are classified as convection, radiant or combination of these.

Reheater : Some of the heat of superheated steam is used to rotate the turbine where it loses some of its energy.Reheater is also steam boiler component in which heat is added to this intermediate-pressure steam, which has given up some of its energy in expansion through the high-pressure turbine. The steam after reheating is used to rotate the second steam turbine (see Layout fig) where the heat is converted to mechanical energy.This mechanical energy is used to run the alternator, which is coupled to turbine, there by generating elecrical energy.

Condenser: Steam after rotating staem turbine comes to condenser.Condenser refers here to the shell and tube heat exchanger (or surface condenser) installed at the outlet of every steam turbine in Thermal power stations of utility companies generally. These condensers are heat exchangers which convert steam from its gaseous to its liquid state, also known as phase transition. In so doing, the latent heat of steam is given out inside the condenser. Where water is in short supply an air cooled condenser is often used. An air cooled condenser is however significantly more expensive and cannot achieve as low a steam turbine backpressure (and therefore less efficient) as a surface condenser.

The purpose is to condense the outlet (or exhaust) steam from steam turbine to obtain maximum efficiency and also to get the condensed steam in the form of pure water, otherwise known as condensate, back to steam generator or (boiler) as boiler feed water. Why it is required? The steam turbine itself is a device to convert the heat in steam to mechanical power. The difference between the heat of steam per unit weight at the inlet to turbine and the heat of steam per unit weight at the outlet to turbine represents the heat given out (or heat drop) in the steam turbine which is converted to mechanical power. The heat drop per unit weight of steam is also measured by the word enthalpy drop. Therefore the more the conversion of heat per pound (or kilogram) of steam to mechanical power in the turbine, the better is its performance or otherwise known as efficiency. By condensing the exhaust steam of turbine, the exhaust pressure is brought down below atmospheric pressure from above atmospheric pressure, increasing the steam pressure drop between inlet and exhaust of steam turbine. This further reduction in exhaust pressure gives out more heat per unit weight of steam input to the steam turbine, for conversion to mechanical power. Most of the heat liberated due to condensing, i.e., latent heat of steam, is carried away by the cooling medium. (Water inside tubes in a surface condenser, or droplets in a spray condenser (Heller system) or air around tubes in an air-cooled condenser).

Condensers are classified as (i) (ii)

Jet condensers or contact condensers Surface condensers.

In jet condensers the steam to be condensed mixes with the cooling water and the temperature of the condensate and the cooling water is same when leaving the condenser; and the condensate can't be recovered for use as feed water to the boiler; heat transfer is by direct conduction.

In surface condensers there is no direct contact between the steam to be condensed and the circulating cooling water. There is a wall interposed between them through heat must be convectively transferred. The temperature of the condensate may be higher than the temperature of the cooling water at outlet and the condensate is recovered as feed water to the boiler. Both the cooling water and the condensate are separately withdrawn .Because of this advantage surface condensers are used in thermal power plants. Final output of condenser is water at low temperature is passed to high pressure feed water heater, it is heated and again passed as feed water to the boiler. Since we are passing water at high temperature as feed water the temperature inside the boiler does not decrease and boiler efficiency also maintained.

Cooling Towers: The condensate (water) formed in the condenser after condensation is initially at high temperature. This hot water is passed to cooling towers. It is a tower- or building-like device in which atmospheric air (the heat receiver) circulates in direct or indirect contact with warmer water (the heat source) and the water is thereby cooled (see illustration). A cooling tower may serve as the heat sink in a conventional thermodynamic process, such as refrigeration or steam power generation, and when it is convenient or desirable to make final heat rejection to atmospheric air. Water, acting as the heat-transfer fluid, gives up heat to atmospheric air, and thus cooled, is recirculated through the system, affording economical operation of the process.

Two basic types of cooling towers are commonly used. One transfers the heat from warmer water to cooler air mainly by an evaporation heat-transfer process and is known as the evaporative or wet cooling tower.

Evaporative cooling towers are classified according to the means employed for producing air circulation through them: atmospheric, natural draft, and mechanical draft. The other transfers

the heat from warmer water to cooler air by a sensible heat-transfer process and is known as the non-evaporative or dry cooling tower.

Non-evaporative cooling towers are classified as air-cooled condensers and as air-cooled heat exchangers, and are further classified by the means used for producing air circulation through them. These two basic types are sometimes combined, with the two cooling processes generally used in parallel or separately, and are then known as wet-dry cooling towers. Evaluation of cooling tower performance is based on cooling of a specified quantity of water through a given range and to a specified temperature approach to the wet-bulb or dry-bulb temperature for which the tower is designed. Because exact design conditions are rarely experienced in operation, estimated performance curves are frequently prepared for a specific installation, and provide a means for comparing the measured performance with design conditions.

Economiser: Flue gases coming out of the boiler carry lot of heat. Function of economiser is to recover some of the heat from the heat carried away in the flue gases up the chimney and utilize for heating the feed water to the boiler. It is placed in the passage of flue gases in between the exit from the boiler and the entry to the chimney. The use of economiser results in saving in coal consumption, increase in steaming rate and high boiler efficiency but needs extra investment and increase in maintenance costs and floor area required for the plant. This is used in all modern plants. In this a large number of small diameter thin walled tubes are placed between two headers. Feed water enters the tube through one header and leaves through the other. The flue gases flow outside the tubes usually in counter flow.

Air preheater: The remaining heat of flue gases is utilised by air preheater. It is a device used in steam boilers to transfer heat from the flue gases to the combustion air before the air enters the furnace. Also known as air heater; air-heating system. It is not shown in the layout. But it is kept at a place nearby where the air enters in to the boiler. The purpose of the air preheater is to recover the heat from the flue gas from the boiler to improve boiler efficiency by burning warm air which increases combustion efficiency, and reducing useful heat lost from the flue. As a consequence, the gases are also sent to the chimney or stack at a lower temperature, allowing simplified design of the ducting and stack. It also allows control over the temperature of gases leaving the stack (to meet emissions regulations, for example).After extracting heat flue gases are passed to electrostatic precipitator.

Electrostatic precipitator: It is a device which removes dust or other finely divided particles from flue gases by charging the particles inductively with an electric field, then

attracting them to highly charged collector plates. Also known as precipitator. The process depends on two steps. In the first step the suspension passes through an electric discharge (corona discharge) area where ionization of the gas occurs. The ions produced collide with the suspended particles and confer on them an electric charge. The charged particles drift toward an electrode of opposite sign and are deposited on the electrode where their electric charge is neutralized. The phenomenon would be more correctly designated as electrodeposition from the gas phase. The use of electrostatic precipitators has become common in numerous industrial applications. Among the advantages of the electrostatic precipitator are its ability to handle large volumes of gas, at elevated temperatures if necessary, with a reasonably small pressure drop, and the removal of particles in the micrometer range. Some of the usual applications are: (1) removal of dirt from flue gases in steam plants; (2) cleaning of air to remove fungi and bacteria in establishments producing antibiotics and other drugs, and in operating rooms; (3) cleaning of air in ventilation and air conditioning systems; (4) removal of oil mists in machine shops and acid mists in chemical process plants; (5) cleaning of blast furnace gases; (6) recovery of valuable materials such as oxides of copper, lead, and tin; and (7) separation of rutile from zirconium sand.

Smoke stack: A chimney is a system for venting hot flue gaseous smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. They are typically almost vertical to ensure that the hot gases flow smoothly, drawing air into the combustion through the chimney effect (also known as the stack effect). The space inside a chimney is called a flue. Chimneys may be found in buildings, steam locomotives and ships. In the US, the term smoke stack (colloquially, stack) is also used when referring to locomotive chimneys. The term funnel is generally used for ship chimneys and sometimes used to refer to locomotive chimneys. Chimneys are tall to increase their draw of air for combustion and to disperse pollutants in the flue gases over a greater area so as to reduce the pollutant concentrations in compliance with regulatory or other limits.

Generator: An alternator is an electromechanical device that converts mechanical energy to alternating current electrical energy. Most alternators use a rotating magnetic field. Different geometries - such as a linear alternator for use with Stirling engines - are also occasionally used. In principle, any AC generator can be called an alternator, but usually the word refers to small rotating machines driven by automotive and other internal combustion engines.

Transformers: It is a device that transfers electric energy from one alternating-current circuit to one or more other circuits, either increasing (stepping up) or reducing (stepping down) the voltage. Uses for transformers include reducing the line voltage to operate low-voltage devices (doorbells or toy electric trains) and raising the voltage from electric generators so that electric power can be transmitted over long distances. Transformers act through electromagnetic induction; current in the primary coil induces current in the secondary coil. The secondary voltage is calculated by multiplying the primary voltage by the ratio of the number of turns in the secondary coil to that in the primary.

COAL HANDLING PLANT (CHP)

The coal handling plant consists of two plants:  Old Coal Handling Plant (OCHP)  New Coal Handling Plant (NCHP) The OCHP supplies coal to Unit- I, II, III & NCHP supplies coal to Unit- IV and V. COAL SUPPLIED AT ‘B’TPS Coal is supplied to BTPS by Kharia, Kakri and Bina coal mines. It is non-cooking coal and has following specifications: Moisture- less than 8%  Volatile matter-17% to 19%  Ash- 35% - 40%  Calorific Value- 4500 to 5300 Kcal/kg  Coal is received in railway box racks containing 20 - 42 wagons in each rack.  Capacity of each box wagon is about 55 ton.  These wagons are placed on 2 wagon tippler in OCHP & one wagon tippler in NCHP, in total 3, capacity 80 ton each.

COAL CYCLE

OLD COAL HANDLING PLANT (OCHP)

The main constituents of OCHP plant are:WAGON TIPPLER Wagon from coal yard come to the tippler and emptied here. There are 2 wagon tipplers in the OCHP. The tippler is tilted to about 137°- 141° so that coal from the wagon is emptied into the hopper. Elliptics feeder is used in OCHP. Total 8 feeders are used, 4 in each hopper. Slip Ring Induction Motor is used to operate a wagon tippler. This type of IM is used in the tippler because of its high resistance, low speed & high torque characteristics. The rating of the motor used is: o Power 55 Kw o Voltage 415V o Current 102A o Speed 1480rpm o Phase 3 o Frequency 50Hz Three types of wagon tipplers are used:- a) ROTASIDE: - It is used for open type wagons in which each wagon carries around 50- 56 tons of coal. The wagon is tilted by 150° to put the coal in the unloading hopper. b) ROTARY: - In this case the unloading hopper is placed directly under the tippler table. This is also used to tilt the wagon tippler to 180°. c) ROCKING TYPE: - It is used for close type

wagons. In this hoppers is placed by the side of end rocking is provided to facilitate unloading of coal at corners of the wagon. CONVEYER Conveyer belts are used in the OCHP to transfer coal from one place to other as required in a convenient & safe way. All the belts are numbered accordingly so that their function can be easily demarcated. These belts are made of rubber & move with a speed of 250-300 m/min. Motor employed for the conveyer has a capacity of 150 HP. These conveyers have a capacity of carrying the coal at the rate of 400 ton/hr. ZERO SPEED SWITCH It is used as a safety device for the motor i.e. if the belt is not moving & the motor is ON, then it burns to save the motor. This switch checks the speed of the belt & switches off the motor when speed is zero. METAL DETECTOR As the conveyer belt take coal from wagon to crusher house, no metal piece should go along with coal. To achieve this objective, metal detectors & separators are used. In the OCHP, these MD‟s are installed in the conveyer belts 2A & 2B. CRUSHER HOUSE Both the plants i.e. OCHP & NCHP use TATA crusher powered by BHEL motor. Crusher is of ring type and the motor is a HT motor of rating 400HP & 6.6 KV. Crusher is designed to crush the pieces to 20 mm size i.e. practically considered as the optimum size for transfer via conveyer. ROTARY BREAKER If any large piece of metal of any hard substances like metal impurities comes in the conveyer belt which cause load on the metal separator, then the rotary breaker rejects them reducing the load on the metal detector. STACKER-CUM-RECLAIMER It is used for stacking & reclaiming the coal from the stockyard in case of unavailability of wagons from coal mines. PLOUGH FEEDER These plough feeders are generally installed under slot bunkers or hoppers. These are used top lough the coal to the belt from the coal fed from stockyard. These feeders used in this power station are generally of rotary type. TRIPPERS Trippers are provided in the conveyer to collect the material at desired location on either side or along the conveyer with the help of chute/ducts fitted with tripper itself. The motor in the tripper can make it move both in forward and reverse direction. PULL GUARD SWITCH These are the switches which are installed at every 10m gap in a conveyer belt to ensure the safety of motors running the conveyer belts. If at any time some accident happens or coal jumps from belt and starts collecting at a place, this switch can be moved to NO(normally open) position from NC (normally closed) position to stop conveyor belt from moving. At this time the problem can be corrected & then again the switch can be moved to NC (normally closed) position for normal working again.

INTERLOCKS: - The CHP is normally spread over a wide area with centralized control room. Elaborate scheme is therefore provided. If due to any emergency either the conveyor belt or the motor has to be stopped, due to this interlocking all the other motors connected to it will automatically stop &will not work till signal is given from the control room. 59 The control & protection scheme normally includes:  A hooter system to warn that the plant is going to be started. The plant can be started only after a definite time after the hooter is energized.  Sequential starting of conveyor system and tripping of all proceeding system if any equipment in the chain is tripped.  Tripping of conveyor from speed switch for protection against belt slippage. SEQUENTIAL OPERATION OF OCHP: I. Unloading the coal II. Crushing & storage. III. Conveying to boiler bunkers. a) Coal arrives to plant via road, rail, sea, and river or canal route from collieries. Most of it arrives by rail route only in railway wagons. Coal requirement by this plant is approximately 10,500 metric ton/day. b) This coal is tippled into hoppers. If the coal is oversized (400 mm sq), then it is broken manually so that it passes the hopper mesh where through elliptic feeder it is put into vibrators & then to conveyor belt 1A & 1B. c) The coal through conveyor belts 1A & 1B goes to the crusher house. Also the extra coal is sent to stockyard through these belts. d) In the crusher house the small size coal pieces goes directly to the belt 2A & 2B whereas the big size coal pieces are crushed in the crusher & then given to the belts 2A & 2B. e) The crushed coal is taken to the bunker house via the conveyor belts 3A & 3B where it can be used for further operations.

NEW COAL HNDLING PLANT (NCHP)

KEY DIAGRAM

The main constituents of NCHP plant are:- Most of the constituents of the NCHP are the same as that of OCHP. WAGON TIPPLER In NCHP there is only one wagon tippler. In this it takes 52 sec to raise a wagon, 10 sec to empty the wagon completely & then again 52 sec to bring the tippler down. A semi-circular huge WT gear is used to run the tippler. Protocol cameras have been installed for safety to ensure that no moving creature or object is near the wagon which is on the tippler. 62 COAL FEEDER TO THE PLANT Vibro feeders are installed below the hopper which helps in putting the coal to the conveyor belts. There are 2 conveyor belts & 3 vibro feeder per plant, so in total there are 6 vibro feeders. Given below are the feeder motor specifications: 

Power 15HP



Voltage 415V



Speed 1450rpm CONVEYOR TURNING POINT-6

BREAKER HOUSE This house is required to render the coal size to 100mm sq. A 415W LT motor is used in the breaker house. REJECTION HOUSE The coal comes to breaker house via conveyor belts 12A & 12B. Now in the breaker house the huge stones & metal impurities are separated & sent to reject bin house through belts 18A &18B. RECLAIM HOPPER It is the stockyard in which coal is stored for emergency purposes. Around 3 lakh ton of coal can be stored in it TURNING POINT 7 CRUSHER HOUSE To ensure that the coal is of uniform size it is passed through crusher. The crusher is of ring type. Has a motor rating of 400HP, 606KV. It is designed to crush the pieces to 20mm size SEQUENTIAL OPERATION OF NCHP:a) Coal arrives in wagons and tipples into hoppers. b) if the coal is oversized (400mm sq), then it is broken manually so that it passes through the hopper mesh. c) From hopper it is taken to TP-6 12A & 12B. d) Conveyors 12A & 12B take the coal to the breaker house which renders the coal size to be 100 mm sq. e) Metal separator & metal detector are installed in conveyor belts 14A/B & 15A/B respectively to remove the metal impurities . f) Stones which are not able to pass through the 100mm sq mesh of hammer are rejected via 18A & 18B to the rejection house. g) Extra coal is sent to the reclaim hopper via conveyor 16A & 16B. h)From TP-7, coal is taken by conveyor 14A & 14B to the crusher house whose function is to render size of the coal to 20mm sq. SPECIFICATIONS OF MOTORS USED IN NCHP:I. II. III.

Crusher: - BHEL ILAT/12B HD/02, 736rpm, 550Kw, 6600V. Wagon Tippler: - 5D315l, 98Kw slip ring motor. Conveyors: - 1)11A/B, 12A/B: - 125Kw, 315m, 1485rpm. 2)13A/B: - 55Kw, 250m, 1480rpm. 3)14A/B, 15A/B: - 150Kw, 355m, 1485rpm. 4)16A/B, 17A/B: - 110Kw, 315m, 1485rpm.

5)18A/B: - 37Kw, 225m, 1470rpm. IV. Rotary Breaker: - 110Kw, 315m, 1485rpm IV. V. VI. VII.

Belt Feeder: - 15Kw, 180L, 1445rpm Reversible Belt Feeder: - 18.7Kw, 200L, 1485rp VF 1-6: - 7.5Kw, 160m, 1485rpm VF 7-8: - 15Kw, 180L, 1485rpm

IX. VF 9-12: - 11Kw,160L, 1485rpm X. WSP Crusher House: - 15Kw, 160m, 4000rpm XI. WSP Breaker House: - 7.5Kw, 132m, 1865rpm XII. Metal Separator: - 5KV, 132m, 1410rpm XIII. Spray Precipitator: - 18.5Kw, 200L, 3000rpm

SAFETY DEVICES FOR BELT CONVEYORS Sometimes the belt is wet due to any reason, so it may not run due to reduced friction. A switch senses this and prevents the belt from choking. Sometime any accident may occur which requires the belt to stop, the pull cords are pulled to stop the conveyor. This system starts again only when the pull cords are rest. There is a push button in the control room from where the belt can be stopped in case of emergency stoppage. Other equipments are pulley. Pulleys are made of mild steel, rubber logging is provided to increase the friction factor between the pulley and belt.

MILLING SYSTEM 1. RC BUNKER Raw coal is fed directly to these bunkers. These are 3 in no. per boiler. 4 & ½ tons of coal are fed in 1 hr. the depth of bunkers is 10m. 2. RC FEEDER It transports pre-crust coal from raw coal bunker to mill. The quantity of raw coal fed in mill can be controlled by speed control of aviator drive controlling damper and aviator change 3. BALL MILL : The ball mill crushes the raw coal to a certain height and then allows it to fall down. Due to impact of ball on coal and attraction as per the particles move over each other as well as over the Armor lines, the coal gets crushed. Large particles are broken by impact and full grinding is done by attraction. The Drying and grinding option takes place simultaneously inside the mill. In ball mill coal is converted to powdered form and due to pneumatic action the powdered form of coal is transferred upwards. 4. CLASSIFIER: It is equipment which serves separation of fine pulverized coal particles medium from coarse medium. The pulverized coal along with the carrying medium strikes the impact plate through the lower part. Large particles are then transferred to the ball mill.

5. MILL FAN From ball mill the powdered coal is sucked through mill fan. 6. CYCLONE SEPARATORS It separates the pulverized coal from carrying medium. The mixture of pulverized coal vapour caters the cyclone separators tangentially in the upper part of the separator. Due to decrease in the velocity the centrifugal action, the pulverized coal separated from the vapour &falls down to the lower epical part. 7. THE TURNIGATE It serves to transport pulverized coal from cyclone separators to pulverized coal bunker or to worm conveyors. There are 4 turn gates per boiler. 8. WORM CONVEYOR It is equipment used to distribute the pulverized coal from bunker of one system to bunker of other system. It can be operated in both directions

GENERATORS

The generator works on the principle of electromagnetic induction. There are two components stator and rotor. The rotor is the moving part and the stator is the stationary part. The rotor, which has a field winding, is given an excitation through a set of 3000rpm to give the required frequency of HZ. The rotor is cooled by Hydrogen gas, which is locally manufactured by the plant and has high heat carrying capacity of low density. If oxygen and hydrogen get mixed then they will form very high explosive and to prevent their combining in any way there is seal oil system. The stator cooling is done by de-mineralized (DM) water through hollow conductors. Water is fed by one end by Teflon tube. A boiler and a turbine are coupled to electric generators. Steam from the boiler is fed to the turbine through the connecting pipe. Steam drives the turbine rotor. The turbine rotor drives the generator rotor which turns the electromagnet within the coil of wire conductors. Carbon dioxide is provided from the top and oil is provided from bottom to the generator. With the help of carbon dioxide the oil is drained out to the oil tank.  Hydrogen gas is used to cool down the rotor.  Lube oil is used to cool the bearings. 

DM water is used to cool the stator.

 Seal oil is used to prevent hydrogen leakage 

Seal oil coolers are present to cool the seal oil

 Hydrogen dryer are used which removes the moisture from hydrogen gas and then is supplied to the generator. 

Clarified water in cooling tower is used to cool down the hydrogen gas.

RATINGS OF THE GENERATORS USED •

TURBO GENERATOR 500 MW (‘B’TPS)

•

TURBO GENERATOR 210 MW ( ‘A’TPS)

The 500 MW generator generates 21.75 KV and 210 MW generates 15.75 KV. The voltage is stepped up to 400 KV with the help of generator transformer and is connected to the grid. The voltage is stepped down to 6.6 KV with the help of UNIT AUXILLARY TRANSFORMER (UAT) and this voltage is used to drive the HT motors. The voltage is further stepped down to 415 V and then to 220 V and this voltage is used to drive Lt Motors.

TURBO GENERATOR 500MW MAKE

BHEL

POLES

2

FORM

LCH

CAPACITY

589,000 KVA

POWER

500,000 KW

STATOR VOLTAGE

21,000 V

STATOR CURRENT

16194 A

SPEED

3000 rpm

POWER FACTOR

0.85

FREQUENCY

50 HZ

EXCITATION

392 V

STATOR CURRENT GAS PRESSURE

4.2 kg/cm2

CONNECTION

YY

INSULATION CLASS COOLANT

4810 A

F

WATER AND HYDROGEN

INLET COOLANT TEMP.

48 C

STATOR TEMP. RISE

72 K

FIELD TEMP RISE

62 K

TURBO GENERATOR 210MW MAKE

BHEL, Haridwar

CAPACITY

247,000 KVA

POWER

210,000 KW

STATOR VOLTAGE

15,750 V

STATOR CURRENT

9050 A

SPEED POWER FACTOR

5000 rpm 0.85

FREQUENCY

50 HZ

EXCITATION

310 V

GAS PRESSURE COOLANT CONNECTION INSULATION CL

3.5 kg/cm WATER AND HYDROGEN YY B

TRANSFORMERS

INTRODUCTION It is a static machine which increases or decreases the AC voltage without changing the frequency of the supply. It is a device that: 

Transfer electric power from one circuit to another.



It accomplishes this by electromagnetic induction.



In this the two electric circuits are in mutual inductive influence of each other.

WORKING PRINCIPLE It works on FARADAY‟S LAW OF ELECTROMAGNETIC INDUCTION (self or mutual induction depending on the type of transformer).

MAIN PARTS  CONSERVATOR It is used generally to conserve the insulating property of the oil from deterioration& protect the transformer against failure on account of bad quality of oil.

 SILICAGEL DEHYDRATING BREATHER It is used to prevent entry of moisture inside the transformer tank. The breather consists of silica gel.  GAS OPERATED RELAY (BUCHHOLZ RELAY) It is a gas actuated relay used for protecting oil immersed transformer against all types of faults. It indicates presence of gases in case of some minor fault & take out the transformer out of circuit in case of serious fault.  BUSHINGS It is made from highly insulating material to insulate & to bring out the terminals of the transformer from the container. The bushings are of 3 types: a. Porcelain bushings used for low voltage transformer b. Oil filled bushings used for voltage up to 33KV. c. Condensed type bushings used for voltage above 33KV.  OIL GUAGE Every transformer with an oil guage to indicate the oil level. The oil guage may be provided with the alarm contacts which gave an alarm the oil level has dropped beyond permissible height due to oil leak etc.  TAPPINGS The transformer are usually provided with few tappings on secondary side so that output voltage can be varied for constant input voltage.  RADIATORS It increases the surface area of the tank & more heat is thus radiated in less time.  WINDINGS TEMPERATURE INDICATOR (OIL GUAGE) Device which indicates the temperature of winding of transformer & possible damage to the transformer due too overload can be prevented.

CONSTRUCTIONAL FEATURES: 

3 phase transformer is constructed in the core type construction



For reducing losses a smaller thickness of lamination is used.



For the above reason it is also called cold-rolled steel instead hot-rolled steel is used.

 High flux densities (1.4 to 1.7 Wb/sq m) are used in the core of power transformer which carry load throughout. 

For high voltage winding, disc type coils are used.

CLASSIFICATION: (I) ACCORDING TO THE CORE: a) Core type transformer b) shell type transformer

c) Berry type transformer (II) ACCORDING TO PHASES: a) 1phase transformer b) 3phase transformer (III) ACCORDING TO THE PURPOSE FOR WHICH USED : a) Distribution transformer b) Transmission transformer c) Generator transformer d) Station transformer e) Unit Auxiliary transformer (UAT)

COOLING OF TRANSFORMERS OF LARGE MVA TRANSFORMERS: As size of transformer becomes large, the rate of the oil circulating becomes insufficient to dissipate all the heat produced & artificial means of increasing the circulation by electric pumps. In very large transformers, special coolers with water circulation may have to be employed. TYPES OF COOLING: Air cooling 1. Air Natural (AN) 2. Air Forced (AF) Oil immersed cooling 1. Oil Natural Air Natural (ONAN) 2. Oil Natural Air Forced (ONAF) 3. Oil Forced Air Natural (OFAN) 4. Oil Forced Air Forced (OFAF) Oil immersed Water cooling 1. Oil Natural Water Forced (ONWF) 2. Oil Forced Water Forced (OFWF)

MAIN PARTS OF TRANSFORMER

i. Secondary Winding ii. Primary Winding. iii. Oil Level iv. Conservator v. Breather vi. Drain Cock vii. Cooling Tubes. viii. Transformer Oil. ix. Earth Point x. Explosion Vent xi. Temperature Gauge. xii. Buchholz Relay xiii. Secondary Terminal xiv. Primary Terminal

GENERATOR TRANSFORMER : 200MVA UNIT 4 & 5 A POOL OF 3 SINGLE PHASE TRANSFORMERS ARE USED FOR EACH 500MW UNIT

MAKE

CROMPTON GREAVES

RATING NO LOAD VOLTAGE

200MVA HV

NO LOAD VOLTAGE LV

242.487KV 21KV

CURRENT HV

824.8 A

CURRENT LV

9523.8 A

PHASES FREQUENCY

1 50HZ

YEAR OF MANUFACTURE

2014

TYPE OF COOLING

ODAF

OIL TEMP. RISE

35 K

WINDING TEMP. RISE

40 K

CONNECTION SYMBOL TOTAL MASS TOTAL OIL

YNd11 212200 KG 48400 KG/55314 L

STATION AUXILIARY TRANSFORMER (SAT) Unit I & V- 60/30 MVA The UAT draws its input from the main bus-ducts. The total KVA capacity of UAT required can be determined by assuming 0.85 power factor & 90% efficiency for total auxiliary motor load. It is safe & desirable to provide about 20% excess capacity then circulated to provide for miscellaneous auxiliaries & possible increase in auxiliary. MAKE RATING

TOSHIBA HV 36000/60000KVA LV1 18000/30000 KVA LV2 18000/30000 KVA

RATED VOLTAGE

RATED CURRENT

HV

132 KV

LV1

6900 V

LV2

6900V

HV

157/262 A

LV1 1506/2510 A LV2 1506/2510 A PHASES FREQUENCY TYPE OF COOLING OIL TEMP. RISE WINDING TEMP. RISE CONNECTION SYMBOL

3 50HZ ONAN/ONAF 50/55 K 40 K YNd11d11

EXCITATION TRANSFORMER This transformer is used to power the field circuit of the turbogenerator. MAKE RATED POWER RATED FREQUENCY NO. OF PHASES

TOSHIBA 30000KVA 50HZ 3

RATED VOLTAGE HV

21000 V

RATED VOLTAGE LV

6900 V

RATED CURRENT HV

825 A

RATED CURRENT LV

2510 A

CONNECTION SYMBOL

Yd1

COOLING

ONAN

IMPEDANCE VOLTAGE

17.1%

TEMPERATURE RISE WINDING

55 K

TEMP. RISE OIL

50K

HT SWITCHGEAR

1.

MINIMUM OIL CIRCUIT BREAKER These use oil as quenching medium. It comprises of simple dead tank row pursuing projection from it. The moving contracts are carried on an iron arm lifted by a long insulating tension rod and are closed simultaneously pneumatic operating mechanism by means of tensions but throw off spring to be provided at mouth of the control the main current within the controlled device.

Type

HKH 12/1000c

Rated Voltage

66 KV

Normal Current

1250A

Frequency Breaking Capacity

5Hz 3.4+ KA Symmetrical 3.4+KA Asymmetrical 360 MVA Symmetrical

Motor Voltage

220 V/DC

2.

AIR CIRCUIT BREAKER

In this the compressed air pressure around 15 kg per cm^2 is used for extinction of arc caused by flow of air around the moving circuit . The breaker is closed by applying pressure at lower opening and opened by applying pressure at upper opening. When contacts operate, the cold air rushes around the movable contacts and blown the arc: It has the following advantages over OCB:i. Fire hazard due to oil are eliminated. ii. Operation takes place quickly. iii. There is less burning of contacts since the duration is short and consistent. Facility for frequent operation since the cooling medium is replaced constantly. iv. Rated Voltage

6.6 KV

Current

630 A

Auxiliary current

3.

220 V/DC

SF6 CIRCUIT BREAKER This type of circuit breaker is of construction to dead tank bulk oil to circuit breaker but the principle of current interruption is similar to that of air blast circuit breaker. It simply

employs the arc extinguishing medium namely SF6. When it is broken down under an electrical stress, it will quickly reconstitute itself.

Circuit Breakers Standard-1

EC 56

Rated Voltage

12 KV

Insulation Level

4.

HPA

28/75 KV

Rated Frequency

50 Hz

Breaking Current

40 KA

Rated Current

1600 A

Making Capacity

110 KA

VACUUM CIRCUIT BREAKER It works on the principle that vacuum is used to save the purpose of insulation and. In regards of insulation and strength, vacuum is superior dielectric medium and is better that all other medium except air and sulphur which are generally used at high pressure. Rated frequency Rated making Current Rated Voltage Supply Voltage Closing

50 Hz· 10 Peak KA 12 KV 220 V/DC

SWITCH YARD

As we know that electrical energy can’t be stored like cells, so what we generate should be consumed instantaneously. But as the load is not constants therefore we generate electricity according to need i.e. the generation depends upon load. The yard is the places from where the electricity is send outside. It has both outdoor and indoor equipment. OUTDOOR EQUIPMENTS BUS BAR. LIGHTENING ARRESTER WAVE TRAP BREAKER CAPACITATIVE VOLTAGE TRANSFORMER EARTHING ROD CURRENT TRANSFORMER. POTENTIAL TRANSFORMER LIGHTENING MASK INDOOR EQUIPMENTS RELAYS CONTROL PANELS

CIRCUIT BREAKERS BUS BAR Bus bars generally are of high conductive aluminum conforming to IS-5082 or copper of adequate cross section .Bus bar located in air insulated enclosures & segregated from all other components .Bus bar is preferably cover with polyurethane. BY PASS BUS This bus is a backup bus which comes handy when any of the buses become faulty. When any operation bus has fault, this bus is brought into circuit and then faulty line is removed there by restoring healthy power line. LIGHTENING ARRESTOR It saves the transformer and reactor from over voltage and over currents. It grounds the overload if there is fault on the line and it prevents the generator transformer. The practice is to install lightening arrestor at the incoming terminal of the line. We have to use the lightning arrester both in primary and secondary of transformer and in reactors. A meter is provided which indicates the surface leakage and internal grading current of arrester. WAVE TRAP Power line carrier communication (PLCC) is mainly used for telecommunication, tele-protection and tele-monitoring between electrical substations through power lines at high voltages, such as 110 kV, 220 kV, and 400 kV. PLCC integrates the transmission of communication signal and 50/60 Hz power signal through the same electric power cable. The major benefit is the union of two important applications in a single system. WAVETRAP is connected in series with the power (transmission) line. It blocks the high frequency carrier waves (24 KHz to 500 KHz) and let power waves (50 Hz - 60 Hz) to pass-through. BREAKER Circuit breaker is an arrangement by which we can break the circuit or flow of current. A circuit breaker in station serves the same purpose as switch but it has many added and complex features. The basic construction of any circuit breaker requires the separation of contact in an insulating fluid that servers two functions: i. extinguishes the arc drawn between the contacts when circuit breaker opens. ii. It provides adequate insulation between the contacts and from each contact to earth. CAPACITATIVE VOLTAGE TRANSFORMER A capacitor voltage transformer (CVT) is a transformer used in power systems to step-down extra high voltage signals and provide low voltage signals either for measurement or to operate a protective relay. It is located in the last in the switchyard as it increases the ground resistance.

Finally the voltage from CVT in the switchyard is sent out from the station through transmission lines. EARTHING ROD Normally un-galvanized mild steel flats are used for earthling. Separate earthing electrodes are provided to earth the lightening arrestor whereas the other equipments are earthed by connecting their earth leads to the rid/ser of the ground mar. CURRENT TRANSFORMER It is essentially a step up transformer which step down the current to a known ratio. It is a type of instrument transformer designed to provide a current in its secondary winding proportional to the alternating current flowing in its primary. POTENTIAL TRANSFORMER It is essentially a step down transformer and it step downs the voltage to a known ratio. RELAYS Relay is a sensing device that makes your circuit ON or OFF. They detect the abnormal conditions in the electrical circuits by continuously measuring the electrical quantities, which are different under normal and faulty conditions, like current, voltage frequency. Having detected the fault the relay operates to complete the trip circuit, which results in the opening of the circuit breakers and disconnect the faulty circuit. There are different types of relays: i. ii. iii. iv.

Current relay Potential relay Electromagnetic relay Numerical relay etc.

AIR BREAK EARTHING SWITCH The work of this equipment comes into picture when we want to shut down the supply for maintenance purpose. This help to neutralize the system from induced voltage from extra high voltage. This induced power is up to 2KV in case of 400 KV lines.

ELECTROSTATIC PRECIPITATOR

An electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream. 82 In contrast to wet scrubbers which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in the form of electricity).The most basic precipitator contains a row of thin vertical wires, and followed by a stack of large flat metal plates oriented vertically, with the plates typically spaced about 1 cm to18 cm apart, depending on the application. The air or gas stream flows horizontally through the spaces between the wires, and then passes through the stack of plates. A negative voltage of several thousand volts is applied between wire and plate. If the applied voltage is high enough an electric (corona) discharge ionizes the gas around the electrodes. Negative ions flow to the plates and charge the gas-flow particles. The ionized particles, following the negative electric field created by the power supply, move to the grounded plates. Particles build up on the collection plates and form a layer. The layer does not collapse, thanks to electrostatic pressure (given from layer resistivity, electric field, and current flowing in the collected layer).