Thermal Power Plant Introduction

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Presented by: Akbar Ahmad Bhupesh Kumar Pal

2011PE09 2011PE05

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INTRODUCTION TO ESSAR-MAHAN POWER PLANT 

1200-MW (2x600 MW) coal-fired pit-head power plant

Located in Singrauli district, Madhya Pradesh

CONSULTANTS

ESSAR ENGINEERING SERVICES LTD.

TCE CONSULTING ENGINEERS LTD.

SUPPLIER 

ESSAR CONSTRUCTION (I) LTD.

EBOP ( Electrical Balancing of Plant )

ALSTOM T&D INDIA LTD

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No. of Lines: 4

Line 1 & 2: VINDHYACHAL- KORBA LINE 

Line 3 & 4: MAHAN- SIPAT LINE 

Coal Source

Mahan Coal Block located at 4 Km distance from site allottedto Joint venture Company Mahan Coal Ltd formed between Essar Power &

Hindalco.

Water Source

Rihand water Reservoir 

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Step wise operations in a thermal

power plant are as follows:- Coal is used as a fuel to boil

the water.

Water is boiled to form

pressurized steam.

Pressurized steam is the forcethat cause the turbine to

rotate at a very high speed.

Low pressure steam after

pushing through the turbine

goes into the condenser.

Condenser – the place where

the steam is condensed back it

it’s liquid form .Then theprocess is repeated.

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Operations In Thermal PowerStation

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BASIC OPERATION :

A thermal power plant basicallyworks on Rankine cycle.

. 

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A thermal power station isa power plant in which the primemover is steam driven.

Water is heated, turns into steamand spins a steam turbine whichdrives an electrical generator .

After it passes through theturbine, the steam iscondensed in a condenser andrecycled to where it was heated;

this is known as a Rankine cycle. The greatest variation in the

design of thermal power stationsis due to the different fuelsources.

Some prefer to use theterm energy center because suchfacilities convert forms of heatenergy into electrical energy.

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Definition Of Thermal Power Station 

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1. Cooling tower

2. Cooling water pump

3. Transmission line (3-phase)

4. Unit transformer (3-phase)5. Electric generator (3-phase)

6. Low pressure turbine

7. Boiler feed pump

8. Condenser

9. Intermediate pressure turbine

10. Steam governor valve

11. High pressure turbine

12. Deaerator

13. Feed heater

14. Coal conveyor

15. Coal hopper

16. Pulverised fuel mill

17. Boiler drum

18. Ash hopper

19. Superheater

20. Forced draught fan

21. Reheater

22. Air intake

23. Economiser

24. Air preheater

25. Precipitator

26. Induced draught fan27. Chimney Stack

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COAL FEEDING SYSTEM

Coal is conveyed through rail wagon from out side of 

plant and through conveyor system collected in

hopper

and grinded to a very fine powder by large metalspheres in the pulverized fuel mill.

Conveyor Coal Hopper

Pulverized Mill

Wagon Tippler

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Pulverized coal is put in boiler furnace in which water is heated and circulateduntil the water is turned in to steam at the required pressure

The steam then rises up and gets collected inside the boiler drum. The boiler ismade up of carbon steel. Boiler drum is cylindrical drum like structure containsmixture of water and steam.

The steam that comes out of the boiler with increased temperature andpressure.

Types of boilers are natural circulation, dry bottom, and tangential fired,radiant heat type

Boiler in this plant is four corners tangential-firing type

SUPERHEATER: Super heater is a component of a steam-generating unit in whichsteam, after it has left the boiler drum, is heated above its saturationtemperature

REHEATER : Reheater is also steam boiler component in which heat is added tothis intermediate-pressure steam, which has given up some of its energy inexpansion through the high-pressure turbine.

DEARATOR: A deaerator is a device that is widely used for the removal of oxygen

and other dissolved gases from the feedwater to steam-generating boiler.

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Manufacturer  Harbin Boiler Group Co. Ltd (HBC) 

Operational Parameters 

BMCR  TMCR 

Superheater Outlet Steam Flow rate Tph  2060  1875.12 Steam Pressure  Mpa (g)  17.5  17.34 Steam Temp  oC  541  541 

Reheater Inlet Steam Flow rate Tph  1725.78  1579.6 Steam Pressure  Mpa (g)  4.006  3.662 Steam Temp  oC  335.1  325.3 

Reheater Outlet Steam Pressure  Mpa (g)  3.816  3.477 Steam Temp  oC  541  541 

Feed Water  Temp  oC  281.2  275.1 Flue Gas at Air Preheater Outlet Efficiency  %  87.25 Heating Surface Area  m2 

66970 

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A steam turbine is a device that extracts thermal energy frompressurized steam and uses it to do mechanical work on a rotating

output shaft

The turbine is used to drive an electrical generator

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CONDENSER :

Steam after rotating steam turbine comes to condenser. Thesecondensers are heat exchangers which convert steam from itsgaseous to its liquid state. In so doing, the latent heat of steamis given out inside the condenser.

COOLING TOWERS :

The condensate water after condensation is initially at hightemperature. This hot water is passed to cooling towers. It isa tower in which atmospheric air circulates in direct or indirectcontact with warm water and the water is thereby cooled. Water,acting as the heat-transfer fluid, gives up heat to atmospheric

air, and thus cooled.

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ECONOMISER :

Flue gases coming out of the boiler carry lot of heat.

Function of economiser is to recover some of the heatfrom the heat carried away in the flue gases up thechimney and utilize for heating the feed water to theboiler. It is placed in the passage of flue gases in betweenthe exit from the boiler and the entry to the chimney.

AIR PREHEATER :

The remaining heat of flue gases is utilised by airpreheater. It is a device used in steam boilers to transferheat from the flue gases to the combustion air before theair enters the furnace

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ELECTROSTATIC PRECIPITATOR :

It is a device which removes dust or other finely dividedparticles from flue gases by charging the particlesinductively with an electric field, then attracting them tohighly charged collector plates.

SMOKE STACK (CHIMNEY) :

A chimney is a system for venting hot fluegases or smoke from a boiler, stove, furnace or fireplace tothe outside atmosphere. They are typically almost verticalto ensure that the hot gases flow smoothly, drawing air into

the combustion through the chimney effect

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The transformation of mechanical energy into electrical

energy is carried out by the generator. When the rotor is energised the flux lines emitted by it are

cut by the stator windings which induces an emf in them

given by

E = 4.44 f Φ N 

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Manufacturer  Harbin Generator Co. Ltd. Rated Output  600 MW  705.88 MVA Phase  3 Frequency  Hz  50 Speed  rpm  3000 Stator Winding Type  YY Stator Current  A  20377 Stator Voltage  KV  20 Power Factor  0.85 (lag) 

Cooling mode Stator winding  Water Rotor winding  Hydrogen 

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Generator Frame volume(including rotor)  m³  110 Generator Rotor Weight  t  66.5 Generator Stator Weight  t  300 Generator Total Weight  t  465 Excitation type  static excitation 

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The transformer is a device that transfers electrical energy from

one electrical circuit to another through the medium of magneticfield and without the change of frequency.

The two windings are not connected electrically but coupled

magnetically. Its efficiency is in the range of 97 to 98 %.

Main Transformers

Generator Transformer (GT):-

-This is a step up transformer.

- This supply gets its primary supply from generator and its

secondary

supplies the switchyard from where it is transmitted to grid.

- primary is in STAR and secondary is in DELTA

- GT 1 & GT 2 - 3x1PH, 250MVA & there are two GT in this plant

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GENERATOR TRANSFORMER  Make  AREVA Type  Double Wound Service  Outdoor  

 No. of Windings Per Phase 

02 

 No. of Phases  01 Rated Power (HV)  250 MVA Rated Power (LV)  250 MVA

Rated Voltage at No Load(HV)  420/ √ 3 Kv Rated Voltage at No Load

(LV)  20 Kv Rated Line Current (HV)  1029.8 A Rated Line Current (LV)

 12500 A

 Rated Frequency  50 Hz Station Transformer (ST):-- It is a step down transformer 

-same rating as the generator transformer

- primary is connected in delta and secondary in star

-These are 2 in number each of 70 MVA.

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STATION TRANSFORMER  Make  AREVA Type  Double Wound Service  Outdoor  

 No. of Windings Per Phase  02  No. of Phases  03 Rated Power (PRI)  70 MVA Rated Power (SEC 1)  25 MVA Rated Power (SEC 2)  45 MVA Rated Voltage at No Load (HV)  20 kV Rated Voltage at No Load (SEC 1)  34.5 kV Rated Voltage at No Load (SEC 2)  11.5 kV Rated Line Current (PRI)  2023.12 A Rated Line Current (SEC 1)  418.87 A Rated Line Current (SEC 2)  2261.87 A Rated Frequency  50 Hz Unit Auxiliary Transformer (UT): 

-This is a step down transformer.

-The primary receives from generator and secondary supplies a 6.6 KV bus

-This is oil cooled

-These are 4 in number

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UNIT TRANSFORMER  Make  AREVA Type  Double Wound 

 No. of Windings Per Phase  02  No. of Phases  03 Rating Rated Power (HV)  36/ 45 MVA Rated Power (LV)  36/ 45 MVA Rated Voltage at No Load (HV)  20 kV Rated Voltage at No Load (LV)  11.5 kV Rated Line Current (HV)  1040.46/ 1300.58 A Rated Line Current (LV)  1809.49/ 2261.87 A Rated Frequency  50 Hz 

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Raw Water Pump HouseRaw Water Reservoir

Chemical

House

Pipe Rack PR-32

CascadeAerator

Sludge Pit

HRSCC -1B

Back WashPit

HRSCC – 1A

Rapid Gravity SandFilter

Filter Water Tank & PumpHouse

Overview of Under construction BOP- Raw Water System

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DM Plant

DM Tanks

Neutralization Pit

DM RegenerationArea

Overview of Under construction BOP- De-mineralization System

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Wagon Tippler 1 &2

Wagon Tippler 3 &4Sloping ConveyorTunnel

TP-3

Conveyor 3A/3B

CHP Retaining Wall

Overview of Under construction BOP- Coal Feeding System

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Crusher House

TP-4

TP-5

Conveyor4A/4B Conveyor 5A/5B

Stacker Reclaimer

Coal Stock Yard

Overview of Under construction BOP- Coal Feeding System

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Overview of Under construction Boiler System

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Three breakers for two buses.

High reliability and operational flexibility

Capability of isolating any circuit breaker or

either main bus for maintenance without serviceinterruption.

A bus fault does not interrupt service.

Double feed to each circuit.

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Bus Ducts Circuit Breaker

Capacitive Voltage Transformer (CVT)

Electro Magnetic Voltage Transformer(EMVT)

Isolators/Disconnectors Earth Switches

Current Transformers

Wave trap

Surge/Lightning Arrestors

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Originally developed in the 1960s, Isolated phase bus duct (IPB or

IPBD), is a method of construction for circuits carrying very largecurrents, typically between a generator and Generator Step-Up

Transformer

Conductors are rolled hollow aluminum tubes, supported within the

enclosure on porcelain or polymer insulators

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Also of two types-

(a) segregated phase bus duct

(b) non-segregated phase bus duct

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These are the automatically operated electrical switch designedto protect an electrical circuit from damage caused by overload

or short circuit. These fault current levels can be 20 or 30 timeslarger than the current under normal operating conditions.

They are used to immediately discontinue electrical flow in caseany fault is detected.

When a fault condition is detected by the pilot devices/relays,

some mechanically stored energy (using something such assprings or compressed air) contained within the breaker is usedto separate the contacts.

When a current is interrupted, an electric arc is generated

Since we are operating on a very high voltage of transmission,

this arc can be extremely dangerous and hence, it must becontained, cooled and extinguished in a controlled way, so thatthe gap between the contacts can again withstand the voltage inthe circuit.

Circuit breakers normally interrupt all three phasessimultaneously.

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The insulating fluids commonly used in circuit breakers are:

Compressed air

Oil which produces hydrogen for arc excitation.

Vacuum

Sulphur hexafluorides (SF6 )

Circuit Breaker used at ESSAR-MAHAN switchyard :

SF6 Circuit Breaker – manufactured by ALSTOM

SPECIFICATION 

Rated Voltage: 420 kV Rated Normal Current: 3000 A

Frequency: 50 Hz

Short Time Withstand Current: 40 kA

Short Circuit Breaking Current: 40 kA

Short Circuit Making Current: 100 kAp

SF6 Gas Pressure at 20oC: 0.85 MPa (abs)

Total Mass of SF6 Gas: 70.8 kg

Rated Opening Time: 30 ms (max)

Rated Closing Time: 110 ms

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The capacitor voltage transformer is used as a means of delivering afiltered, low-voltage signal to the protected relay portions of theattached electrical circuitry

These transformers are mostly used within the high-voltage circuitry asmeasurement devices and as a means of protecting specific parts of the

circuitry.

It systematically step the amount of signal it receives upon input,within the parameters set by the smaller components of the circuit.

These components are usually meters or other measurement devices

that are used to record the amount of signal received by and outputthrough the circuit in its entirety.

The CVT is a capacitor divider with top connected to the line (400kV)and bottom earthed.

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A tap of the capacitor at 22 kV is connected to a transformer inside

the tank. The transformer will have 3 secondary windings to give 110

V each.

2 cores are for protection, 1 for metering.

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In this type of vts the voltage step down takes place by

means of electro magnetic circuit.

It is specially dedicated for line metering purposes.

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These are the electrical switches to completely de-energized anelectrical circuit for service or maintenance

Isolators are disconnecting switches it is used for open the circuitunder no load condition

Opened or closed only when circuit breaker is open.

Accompanied with Earth Switches to earth the residual/magnetizing currents when isolator opens.

Two types

Horizontal Upright

Pantograph Isolator

Center breakIsolator Specifications

Rated Voltage: 420 kV

Rated Current: 2500 A

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Earth Switch is connected between the line conductor and Earth.

Normally it is open when the line is disconnected, the earth switch isclosed so as to discharge the voltage trapped on the line capacitanceto the earth.

When isolator is in open condition, earth switch is closed and viceversa. Normally the Earth switch is mounted on the frame of theisolator

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It is used for measurement of current as well as protectionpurposes.

Much higher values of line currents will be stepped down tosome standard low values, thus can be measured easily.

CT is always connected in series with the power line with theprimary being the line itself.

The secondary winding is having taps to have different CTratios such as 2000/1, 1000/1, 500/1.

There are 5 secondary windings.

Core I - Metering or measurement

Core II – Open Circuit, Earth fault, Back UpProtection

Core III - Main Protection(Differential Protection for

Transformer, DistanceProtection for lines)

Core IV & V – Bus Bar protection

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CT Type Purpose Accuracy Burden

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CT Type Purpose Accuracy Burden

2 CORE Metering 0.2 S 5 VA

4 CORE Metering 0.2 S 5 VA

5 CORE CoreI,II,IV,V

Protection PS 20 VA

Core III Metering 0.2 S 20 VA

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key component in PLC (Power Line Carrier) systems

Used for remote control signals, voice communication, remotemetering and control between substations in the electrical T&D

network.

High voltage transmission lines are also used for transmitting

carrier signals between 30 kHz and 500 kHz Line traps prevent transmission of these high frequency signals to

unwanted directions without loss of energy at power frequency.

Line traps are series-connected

to the transmission lines.

Continuous Current Rating: 2400 A

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Main coil carries the rated current of the transmission line and is designed to withstand the

maximum short-circuit current. Its low self-capacitance provides a high self-resonance

frequency 

Extremely reliable tuning devices This key sub-component of a line trap is mounted

inside the main coil on the central tie rod.

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It is a protective device which diverts the transient over voltagesurges to earth & protect the substation equipment from lightning& switching over voltage surges.

Acts as open circuit during normal conditions and provides a shortcircuit path during lightning surges and over voltages.

The connection made in LA is, one terminal is plugged in to highvoltage terminal & other terminal is earthed.

They are generally connected in parallel with the equipment to beprotected and function to divert the surge current safely to ground.

They present high impedance at power frequency but low

impedance to surge currents. SPECIFICATIONS 

Zinc Oxide, Gapless Type

Rated Voltage: 360 kV

Nominal Discharge Current: 10 kA

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One and a half breaker scheme makes it reliable.

 Almost Zero Emission Plant.

Full Utilization of Steam is ensured.

Coal Waste is proposed to be managed to make

Bricks.

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We have come to know what all processes are neededto generate and run the plant on a 24x7 basis.

This plant is an example in terms of working efficiency

and management of resources to all other thermalplants in our country.

The training gave us an opportunity to clear our 

concepts from practical point of view with the availability

of machinery.

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