VOCATIONAL TRAINING AT MEJIA THERMAL POWER

PLANT

Presented by-AritrA BiswAs(08)

Amit BerA(115)NipAk BANerjee(39)

sumANtA siNghA roy(61)

INTRODUCTION

• Thermal Power Station creates electrical energy by burning coal.

• Thermal Power plant constitutes more than 65% of the total electric power generated in INDIA out of 85% of them is coal based power plant.

• Power plants having capacity more than 1000 MW is known as super thermal power plant.

• Thermal power plants uses the coal, oil as the primary energy sources to generate electricity.

Details of Mejia Thermal Power Plant generating units

GENERAL LAYOUT OF THERMAL POWER PLANT

WORKING CLASSIFICATION

• 1.MECHANICAL OPERATION

• 2.ELECTRICAL OPERATION

• 3.OPERATION of SAFTEY EQUIPMENTS

EQIPMENTS UESD IN MECHANICAL OPERATION

Coal Handling PlantPulverizing PlantDraft FansBoilerAsh Handling PlantTurbine

CondenserCooling TowerFeed Water HeaterEconomizerSuper-heater

& Re-heaterAir Pre-heater

Coal Handling Plant

Pulverizing plant• Pulverizing is a process of

exposing a large surface area to the action of oxygen and consequently helping in combustion.

• Pulverized or powdered coal are highly inflammable.

• Pulverized Coal mixed with air and burned in the fluid gas flow.

• Bio-mass and other materials can also be added to the mixture.

• According to their working principle these mills are classified as

1.CONTACT MILLS 2. BOWL MILLS 3. IMPACT MILLS

Fig.-Horizontal coal Pulverizer.

Draft System

Circulation of air or gas is caused by difference in pressure known as Draft.

These fans are responsible for the flow of gasses through boiler.

Forced Draft Fans used in the inlet of the boiler system.

Induced Draft Fans used in the outlet of the boiler system.

Mechanical efficiency = (AHP/BHP)*100

Difference between AHP & BHP due to the Skin Friction,Turbulence, Mechanical Friction, Leakage.

1. Erosion 2. Corosion 3. Vibration

are the mechanisms which are responsible for the damage & need serious and costly maintenance.

Boiler

• In Boiler steam in generated from demineralized water by addition of heat.

• Added heat has two parts- a) sensible heat which rises temperature & b) latent heat for phase change.

• Boiler is an enclosed vessel in which the water is heated and circulated until the water turned into steam of required pressure and temperature.

Important parts of the boiler are---

◎ 1.Steam drum◎ 2.Superheater

& Re-heater◎ 3.

Attemperator

◎ 4.Air pre-heater

◎ 5. Drain & Vent

◎ 6. Economizer

Technical Data of the BOILER

Ash Handling Plant

• Ash is produced as the byproduct of Combustion. Ash generated in power plant is about 30-40% of total coal consumption and hence the system is required to handle Ash for its proper utilization or disposal.

• COMPOSITION of ASH SiO2, Al2O3, Fe2O3, CaO, MgO.

• Ash generated in the ESP which got carried out with the flue gas is generally called Fly ash. It also consists of Air pre heater ash & Economizer ash.

• Bottom ash formed slurry & transported through pipes for further utilization.

• Ash generated below furnace of the steam generator is called the bottom ash.

• Fly Ash collected from ESP hoppers & extracted by Vaccum pumps.

Turbine

• Turbine extracts thermal energy from pressurized steam to do mechanical work on rotating output shaft.

Turbine

Condenser

• Condenser used to condense the exhausted steam from turbine to obtain maximum efficiency.

• It’s a shell and tube type heat exchanger.

Cooling tower

• The hot water from condenser is cooled here.in MEJIA there are two type of cooling tower

Natural cooling tower Forced cooling tower

Electrical Operation

• The Electrical Operation of a power plant comprises of generation, transmission & distribution of electric energy.

• 2 pole cylindrical rotor type Turbo Generators are used Generation of Electric Power.

Turbo Generator

• Turbo Generator consists of mainly Stator and Rotor.

§ EXCITATION SYSTEM• Excitation system provides the appropriate amount of DC field

current to the field winding.• This system categorized into –a) DC excitation b) AC excitation

system.• In MEJIA thermal plant for unit # 5,6,7,8 the excitation is brushless

but for #1, 2, 3, 4 the excitation is brush excitation.• Functional componentsè excitation power source, semiconductor

rectifier, voltage controller, protective limiting & switching equipment.

Automatic Voltage Controller(AVR)

The digital AVR regulates the terminal voltage of the synchronous machine by direct control of main exciter field current using thyristor convertor.

Transformer

• Several types of transformers are used for various application in power plant like power sending, distribution within the plant etc. These are (with primary voltage --secondary voltage)

• 1.GT: 21 KV- 400 KV• 2.UT: 21 KV - 11KV• 3.UAT: 11 KV - 3.3 KV• 4.UST: 11 KV - 415 volt.• 5.ST : 400 KV -11 KV• 6.SAT : 11 KV- 3.3 KV• 7.SST: 11 KV - 415 volt.

DETAIL DESCRIPTION ABOUT THE TRANSFORMERS IN MEJIA THERMAL POWER

PLANT

Some of the transformer auxiliary are:-

• 1.Conservator tank

• 2.Buccholz relay

• 3.Lightning arrestor

• 4.Fans for cooling

• 5.Transformer bushing

• 6.Breather & Silica gel

Switchyard Section

• Switchyard is an essential hub to co-ordinate the exchange of power between the generators & the transmission lines.

• In the MTPS there is a big 220 KV switchyard for the unit 1 to 6.

• 400 KV switchyard for the unit #7 & 8.• It’s a junction point where the power coming & going out

to the external circuit.• Junction point as deals with the large amount of power,

high capacity of conductors spread throughout the section.

• It is necessary that it remains secure and serviceable to supply the outgoing transmission feeders.

BASIC COMPONENTS• BUS BAR: The conductor to which several incoming & outgoing lines are

connected.• Circuit Breaker: it breaks circuit either manually or automatically under all

condition.it receives its operating command from relay associated with it.• Isolator: Isolators isolates circuit at times. Pantograph & horizontal Centre

break type isolator used in 400 KV section.• Lightning Arrester: its disc filled with ZnO.At the time of high voltage

ZnO particles creates ions & provides a path to the ground.• Wave Trap: It filters the frequency between the line & communication

frequency.• CT & PT : these are used for monitoring the parameters regarding

electrical power.• Capacitive voltage transformer: it also used for the communication

purpose.• Battery Bank: this DC system being used in the protection and control

mechanism. DC power is supplied by the float charging.• Diesel Generator: to fed power supply 415 volt drives during total station

supply failure.

Protection/safety devicesRelay: it senses the fault to the system and send s command to the

circuit breaker. GENERATOR Protection Over load protection Over voltage protection V/f protection Unbalance loading protection Loss of prime mover protection etc. TRANNSFORMER Protection Over load protection Short circuit protection Ground fault protection etc. NEUTRAL GROUNDING TRANSFORMERS It’s used to detect earth faults where secondary winding is

connected to with a low resistance. Whenever earth fault occurs it the current goes to ground via that low resistance.

Other equipment used in the power plants

• Electric motors: maximum motors used in the power plant are 3-ph AC squirrel cage type like

• Service water pump• Primary air fan• Boiler feed pump• Slurry Disposal pump• Draft fans etc.• Synchroscope: before delivering power to the grid station

required to synchronize with the grid phase angles and with the other parameters.

• Control Panel: it’s a panel board from where the engineers monitor the parameters.

THANK YOU