Power Plant Questions

1.About Purging Conditions of Power Plant operations , Rankine Cycle,Boiler Efficiency,Turbine efficiency –

What are the main circuits in the Thermal Power Plant?Answer:Thermal Power plant consists of four main circuits, they are:

Feed water and steam flow circuit Coal and ash circuit Air and gas circuit Cooling water circuit

Steam power plant works on which cycle?Answer: Steam power plant works on the principle of Rankine CycleWhat is the Thermal efficiency of steam power plant?Answer: Thermal efficiency of steam power plant is defined as the ratio of heat equivalent of mechanical energy transmitted to the turbine shaft to the heat of combustion. Generally Thermal efficiency of the steam power plant will be in the range of 30-35%

What is the overall efficiency of the Thermal Power Plant or Steam Power Plant?Answer: Overall efficiency of the system is defined as the ratio of heat equivalent of electrical output to the heat of combustion. Generally Overall efficiency of the steam plant will always be less than the thermal efficiency of the steam plant, it will be of the order of 29-33%Overall efficiency of steam plant is determined by multiplying the thermal efficiency of the plant with efficiency of the generator (electrical efficiency)

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Why the Thermal efficiency of the steam power plant is quite low?Answer: In Steam power station, more than 50% of the total heat of combustion is lost as heat rejected to the condenser and the loss is unavoidable as the heat energy cannot be converted in to mechanical energy with out a drop in temperature. Steam in the condenser is at lowest temperature. This is the reason that the thermal efficiency of the power plant is quite low.On what factors efficiency (thermal) of the steam plant depends?Answer: Efficiency of the thermal plant depends on three factors, they are

1. pressure of steam entering the turbine2. temperature of the steam entering the turbine3. pressure in the condenser

Thermal efficiency increases with increase in temperature and pressure of the steam entering the turbine. For this reason high temperature and pressure are used. Thermal

efficiency is effectively increased by decreasing the pressure in the condenser, so pressure in the condenser is kept as low as possible.Thermal efficiency also increases by reheating the steam between turbine stages

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Why Thermal Power Plants are always situated by the side of rivers or lakes?Answer: Thermal Power Plants are situated close to the rivers or lakes because to meet the large quantity of the water requirement. Water is required in the steam power plants

steam in the boiler for cooling purposes such as in condensers as carrying medium such as in disposal of ash for drinking purpose

What is the purpose of deaerator in steam power plant?Answer: The presence of dissolved gases like oxygen and carbon dioxide in water makes the water corrosive, as they react with metal and forms iron oxide. The solubility of the gases in the water decreases with increase in the temperature and becomes zero at boiling point or saturation point.The purpose of the deaerator is to reduce the dissolved oxygen content in the condensate ( feed water) by increasing its temperature. These gases are removed in the deaerator by heating the feed water to saturation temperature through the bled steam from the turbine.

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Why cooling towers require in the Steam power plant ?Answer: Cooling towers cool the warm water discharged from the condenser and feed the cooled water back to the condenser. There are two types of cooling methods provided in the cooling towers, they can be either wet type or dry typeWet type Cooling towers: In wet cooling towers warm water from the condenser are made to spray on slats or horizontal bars and air is passed from bottom, as the water splashes down from one slat to other due to gravity air and water mixes and heat is rejected in to the air Dry type Cooling tower: Dry type towers are employed where the cooling water is not available in plenty. In dry type warm water from condensate is made to flow through the finned tubes over which cooling air is passed. Heat is rejected to air as water is cooledWhy are feed water heaters are used?Answer:Regenerative Feedwater heaters are employed in steam power plants to improve the cycle efficiency. Also it increases the steam flow rate and reduces the steam flow to the condenser. They raise the temperature of the feed water before it enters the economizer

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What are the major electric systems in Thermal Power Plant?Answer: Major electrical equipment in thermal power plant are

Turbine Generator Exciter System Generator Protection System Generator Transformer HT/LT switch gear Electrical Switch-yard

What are the different Generator Protections employed in Thermal Power Plants?Answer: Faults in the windings, Over load protection, Over heating of windings or bearings, Over speed protection, Loss of Excitation protection, Motoring operation protection, Inadvertent energisation, single phase or unbalanced current protection, out of step operation protection, sub-synchronous oscillations protection and earth fault protectionHow Generator Transformer is cooled in Thermal Power Plant?

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Answer: MVA power rating of the Generator Transformer will be equal to the alternator. Hence lot of heat will be generated while generator transformer is under operation. Oil Forced Air Forced (OFAF) type of cooling is employed for generator transformerWhat are different types of circuit breakers employed in thermal power plant?Answer: For low voltage operation 415/220V vacuum circuit breakers or air break circuit breakers are employed. For voltage ratings about 6.6kV and beyond SF6 circuit breakers are employed.What type of cooling is provided for Generator in power plant?Answer: Hydrogen gas cooling is employed for large size generators because of better heat carrying ability of the hydrogen. Hydrogen cooling is provided for rotors and core of the generator. Water cooling is provided for the stator of the alternator.

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What are the different auxiliary systems in thermal power plant?Answer: Coal handling and storage, coal pulverizes water treatment plant, steam boiler, Drought systems, Ash Handling systems, Steam turbine, Circulation water system, Electrical Systems, Control and Instrumentation, Pollution Control equipment, and Fire Protection System

What is the purpose of Pulverizes?Answer: Pulverizers serve two purposes, to dry the coal and to grind the coal. They crush the coal to size of 74microns

What are different types of Pulverizes?

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Answer: Different types of Pulverizers are:

Ball tube mill Ring roll mill Hammer mill Attrition type mill

What are different types of Steam boilers used in Thermal Power Plants?Answer: Different type of boiler used in thermal power plants are:

Fire tube boiler Water tube boiler Natural Circulation boiler Forced Circulation boiler Once through boiler

What is the largest pump in the thermal power plant?

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nswer: In thermal power plant Boiler Feed Pump (BFP) is the largest pump, it delivers the water to the boiler.

What is Cavitation and disadvantages of Cavitation?Answer: The formation of air bubbles and water vapour on the water surface due to the reduction in the pressure is called "Cavitation". When the pressure on the water reduces below the saturation pressure corresponding to the temperature of the water, the rapid formation of the water vapour and air bubbles starts. The bubbles suddenly collapse with the violent action and this collapsing pressure will be very high. The rapid formation and collapsing of bubbles causes the pitting of the metal surface. Cavitation also reduces the efficiency of the hydraulic prime mover causing the honey-combing of runner and blade contours which reduces the power

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output.

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Question what is actual CAL MODE & cal means? RankAnswer Posted

By

Question Submitted By :: Powerkaushik

This Interview Question Asked @ GIPCL

I also faced this Question!! © ALL Interview .com

Answer CAL MODE, normally during transmitter calibration ormaintenance, we used to put it in CAL mode which give itslast value as a reference value for the controller. So thatwe can calibrate or do maintenance for our transmitterwithout any disturbance to the process controller

0 Vinoth.s

Answer CAL Mode used in instrument/sensor/transmitter maintenance/repair/calibration time.In that time we can give some reference value which is for normal control operation.

Calibration means sensor/transmitter response calibration for required range.

0 Bala Murali/ramesh

[GIPCL]

QuestionIn a thermal power plant ID Fans running with full load butboiler load is only 80 % give reason ?

RankAnswer Posted

By

Question Submitted By :: [email protected]

This Interview Question Asked @ Essar , Tata Power, Definition Octane Number?, ESSAR


Answer There will be soot deposits on outer surface of boiler tube

0 Randhir Singh Yadav

http://electricalquestionsguide.blogspot.com/2011/11/thermal-power-plant-interview-questions_22.html#ixzz2ZbVSnf8S

http://electricalquestionsguide.blogspot.com/2011/11/thermal-power-plant-interview-questions_22.html#ixzz2ZbVSnf8S

Answer Coal feeding may not be as per the required load.

0 A K Handa [Tata Power]

Answer there are many reason for that.1. furnace or any duct of flue gas leakage.2.deposition on super heater which clog the passage of flue gas3.density of fuel below required density of boiler fuel

0 Lalitshukla [Tata Power]

Answer it is due to the air preheater being clogged increasing theload of the ID fans due to the bad suction and this cloggingis mostly due to the baskets being melted due to theformation of the ACIDS from the exhaust gases and the dewpoint effect .

this is the only logical reason for why the ID fan is 100%loaded while the boiler is not .

0 Mohamed Elnakib

[Tata Power]

Answer May be...1.APH tube leakage2.Boiler ducting leakage


[Tata Power]

Question

In a coal fired boiler furnace temp. is high but superheater out let temp. low what reason for this?

RankAnswer Posted

By

Question Submitted By :: [email protected]

This Interview Question Asked @ Essar , Gayatri, Abb


Answer Two reason1. Scale deposit inside the boiler & superheater tube,2. Soot deposits outer surface of boiler & superheater tube,


Answer high cal value of coal is also the reason if we use highamount of petcoke then furnace temp high but boiler outletsteam temp not high

0 Lalit Shukla [Tata Power]

Answer 1.super heated coil have any leak or puntcure.2.continousely opened condition of attemperator valve.3.opened all turbine draine valves in trip condition.4.forced draught fan tamper open value high.5.operating problem having in super heater outlet valve to main sream line.

0 K.p.selvakumar [Tata Power]

Answer because we designed boiler like that, what temperature we require.

0 Pradeip [Tata Power]

Questionexplain why direct on line starting toque and current maynot be acceptable

RankAnswer Posted

By

Question Submitted By :: Victor

This Interview Question Asked @ Avon-Organics


Answer decrese the life time of the system

0 Anusha.choppara

Question

What should be the neutral and body grounding sysytem for grid (132 KV) parallel generators (440 volts)?

RankAnswer Posted

By

Question Submitted By :: Shahriar Kabir

This Interview Question Asked @ Rahimafrooz


Answer Grounding means its a path for returning current, due to imbalance of phase currents there will be a return current after balancing phase sequence in the Generator.

0 G Ravikanth

QuestionHow to decide Heating surface area of boiler on their steamgenerating capacity?

RankAnswer Posted

By

Question Submitted By :: Swapil.gaju


Answer Heating surface area of a boiler depends on gas velocity, size of tube, tube pitch, arrangement, configuration of tube. For the same duty or heat transefer one can develop different designs with significant difference in surface area

0 Randhir Singh

Questionwhy IBD Vent is kept at higher elevation than CBD ? Rank

Answer Posted By

Question Submitted By :: Swapil.gaju


Answer when water is converted into steam, huge quantity ofdissolved salts are residues of this conversion. Theynormally settle down in the bottom of the Boiler drum. In

3 Vinoth

CBD, we continuously remove this dissolved salts otherwiseit will get carry over with steam and damage the blades ofturbine. Where as IBD is to remove Excess feed water whichcrosses the Seperator level inside the boiler drum.so IBD isto prevent carry over water with steam where CBD is toprevent carry over of scales with steam. with above description, we can easily predict why IBD isin higher elevated than CBD.

Answer CBD uses to remove floating impurites which collectes on top of water and IBD uses to remove TDS which collects in bottom (mud drum). So CBD vent kept at higher elevation than IBD vent.

0 Randhir Singh

Question

what is significance of canister vent in condensate extraction pump & difference between vacuume balancinf line & canister vent

RankAnswer Posted

By

Question Submitted By :: Harshavardhan.game

This Interview Question Asked @ Ntpc


Answer Canister vent is used to return back, non condense gas/ steam to condenser


Questionwhy drum level falls when one of the running coal elevations tripped?

RankAnswer Posted

By

Question Submitted By :: Krishnachaitanya.yedubati

This Interview Question Asked @ APGenco


Answer Tripping of Coal Elevator does not get the 0 Abhay

drum level to fall down

Answer tripping coal elevator, Reduces the temperature inside theboiler which incase makes shrinking effect in the boiler drum.

0 Vinoth

Question why HT motor star not grounded? RankAnswer Posted

By

Question Submitted By :: Guest

This Interview Question Asked @ Apollo


Answer transformer and generators are passive equipments motor isnot a passive equipment

0 Vinothkumark

Question

We have 132KV/11KV Grid connected power transformer forgetting power from Grid. Can we use this transformer forsending generated power as well. I mean step up from 11KV to132KV and transmit.

RankAnswer Posted

By

Question Submitted By :: Engineerguide


Answer yes. because transformer is a bi directional divice

0 Vinothkumark

Answer yes, we can transmitt....because transformer working by the mutual induction principle and we can use the transformer upto required voltage and use step-up and step-down....

0 Parthi

Answer yes we can use the said transformer to step up the power. i.e if we used a 132Kv/11KV 5Mva transformer thus we can received the power cap. 5Mva at 11Kv level, but in case of step up i.e 11Kv/132Kv the generation point is 11Kv in this case the firs generation point i.e 132Kv generation capacity should be less than the capacity generated by the 11Kv generator. but over all capacity should not be more than the capacity of transformer.

0 Avnish Kumar

Answer yes exactly we can use same transformer for step up & step down applications,,

Question

In a thermal power plant : Why the Deaerator is placed at height and mostly at 15.5mtr?

Question Submitted By :: Bmohanta34

I also faced this Question!! Rank

Answer Posted By

Re: In a thermal power plant : Why the Deaerator is placed at height and mostly at 15.5mtr?

Answer# 1

so as to net positive suction head( NPSH) for the boiler feed pump(BFP) in conjucture with booster pump

Is This Answer Correct ? 69 Yes 7 No

4 Him295 [ESSAR]


Answer# 2

for net positive suction head for feed pump


2 Dineshsingh


Answer# 3

for creating pressure difference


0 Arun


Answer# 4

It is use to increase pressure of water from dearator, n if we will not use it then due to temperature above 100 degree, if pressure falls then there will be phase change.

Booster Pumps are used in applications where the normal system pressure is low and needs to be increased...


0 Hasan Ahtesham


Answer# 5

By putting the dearator at heigt we guarantee vapor doesn't form at the suction area of feed water pumps so cavetation phenomenun in the impellers can be prevented.


QuestioBoiler capacity is 5ton, what will be the feed water tank

Rank Answer Posted By

n capacity?

Question Submitted By :: Anbarasan

This Interview Question Asked @ Krest , Dscl, India Bull, TCS Chennai Near Vellacherei, Chartrons Engineerin


Answer 5000litres of water

0 Arun Deepan

Answer 5000 litter

0 Nelson Mathew

Answer 5000 litres of water

0 Bicky Prsad

Answer 1000Gallons of water

0 Pradeepkumar

Answer capacity of tank depend upon site to site but it must be atleast 2 to 3 times of boiler capacityit is beacause if nay problem is your water tratment plantthen does not effect your operation

0 Lalitshukla

QuestionWhat is difference between Actual Drum Level and Compensated Drum Level?


Question Submitted By :: Manomallik11

This Interview Question Asked @ Dvc


Answer The drum level varies due to cause of change in drumpressure & drum level will be compensate by the 3 elementcontrol system,so the drum level which is rise or fallbefore acting 3 element control system is generally calledactual drum level. & when it is compensate after the actionof 3 element control system is called compensated drum level

0 Gajanan Kuhite

Answer drum level not compensated by 3 element , 3 element controlthe drum level.drum level compensated by drum pressure & temp.

0 Lalit Shukla

Question What is Droop Control in Woodward? Rank Answer Posted By

Question Submitted By :: Manomallik11


Answer Principal of droop is to povide stable operation,Speed droop is a governer function which reduces governer reference speed as load increase.


Answer WHEN TWO TURBINES ARE RUNNING IN APLANT IN ISALND MODE THAN ONE IS IN DROOP MODE ANDONE IS MASTER MODE.

AS THEIR ARE GOVERNERS FOR EACH TURBINE. SO WE MAKE ONE GOVERNNER FUNCTIONING AS MASTER EHICH OPERATES AND MAINTAIN ONE TURBINE FUNCTIONING AT A DEFINE DPARAMETER ,BUT THE SECOUND DRROP MODE TURBINE WILL FOLLOW THE MASTER AND WILL FOLLOW LOAD

0 Sharanjit

Question

What happen when the AVR of the generator fails? Will it cause power instability and total failure of the alternator?


Question Submitted By :: Danny915


Answer AVR is the Automatic Voltage Regulator which is used to keepthe alternator terminal voltage to be constant whenevervoltage drop occurs....by varying the excitation and thepower supplied to the alternator with turbine...If AVR failsthen the voltage level of the alternator fails to beconstant.so the machine will comes out of synchronism.....

Some protection systems are there...to trip the machine whenthe AVR fails so dont think like intelligents....

0 Sundar M

Answer AVR is Automatic voltage regulator. AVR is a vital part of Alternator if Avr has become failed than alternator should gone at shutdown on undervoltage or No volltage safety. its make clear that whenever your enginator reduce the Rpm by any other fault than alternator also going on undervoltage safety that time AVR cannot balanced the determined voltage or Set point voltage.

0 Sheikh

Answer Total failure of the Alternator

0 Guest

Question what are all the pre commissioning activities in WTP in power plant


Question Submitted By :: Guest


Answer Raw water pump should be ready by which we can takewater to creator.proper cleaning of aerator,clariflocculator And storage tank.Dosing system like alugm Dosing,lime dosing,chlorine dosing should be commissioned.ReadyNess of flocculator.fitting scrapperFitting .isolation gate operations should be cheated

0 Rajan Pandey

Question

what is the difference between flow and force ,draught and vaccum ,tube and pipe?


Question Submitted By :: Palani


Answer Tube inner dia vary for different pressure ratings. Pipe outer dia vary for different pressure ratings

0 Manomallik11

Answer Pipe: mass transfer( ex: only flow)Tube: mass & heat transfer (ex: heat exchange as well as f

0 Vinoth S

Answer Draught represents flow,Vaccum represents intensity


QuestionIn turbine. why they not use 320 oil? Rank Answer Posted By

Question Submitted By :: Palani


Answer In modern Steam turbine(say 600 MW) we use lube oil which having a ISO VG 32 grade,That means oil's kinematic viscosity is 32 centistoke,which have the ability to form hydrodynamic layer or wedge or film which acts as lubricating layer between shaft and journal bearing Babbitt material.As we know viscosity X Film velocity/Unit load= C(Bearing Characteristics number) which indicates whether there will be hydrodynamic lubrication or not.So for this reason generally grade-32 or 46 grade oils used not 320.

0 K R Kumar Ranjan

Question What is indipendant power plant Rank Answer Posted By

Question Submitted By :: Mahendran281985

This Interview Question Asked @ Tvs


Answer If the power produced by many source (coal,bio mass,wind) that is called indipendant power plant.

0 Mahendran281985

Answer IPP MEANS INEPENDENT POWER PLANT.THIS PLANT ONLY USE FOREXPORT PURPOSE.

0 Hitan Kumar Pradhan

[Cvl]

Answer that power plant which is owned by a private firm not bygovernments authorities. the private owner sells power tothe govt.

0 Najeeb [Cvl]

Answer Independant power plant means (IPP) Independant power producerany private firms who generates electricity themselves and sold to any government or non government companies called independent power producer or independant poer plant

0 Sheikh [Cvl]

Question What is indipendant power plant Rank Answer Posted By

Question Submitted By :: S.mahendran


Answer If the power produced by many source (coal,bio mass,wind) that is called indipendant power plant.

0 S.mahendran

QuestionDIFFERENT BETWEEN ELECTRICAL AND ELECTRONIC? Rank Answer Posted By

Question Submitted By :: VIJAY.NPALLY


Answer electrical just produces electricity.that is the flow offree electrons,whereas electronics uses the free electronsin a controlled way that is why the abbreviation ofelectronics is electron mechanics

0 Raja

Answer electrical deals with metal devices where as electronics deals with semi conductor devices

0 Soubi

Answer Electrical is a subject which deals with 0 Loki

simple mechanical machines which uses power as the source with a simple controllable source to be exact.. Electronics can be said it is a similar way of mechanism i.e., source I mean, but with a difference that the controlling thing is purely dependent on the memory of semiconductors... (or) electronics is everything which has semiconductor boards

Answer In electrical engineering we deal wit the High Voltages butLow Frequencies whereas in Electronics Engineering we dealwith Low Voltages but High Frequencies, Foe Example in a Power Generation unit we produce voltageratings reaching thousands but the frequency remains50-60Hz. On the other hand in electronics we have deal withlow voltages like 5V 10V etc. but the frequency oftenreaches KKZ, MHz and even THz (Tera Hz).

5 Nauman Asghar

Answer Electrical having all components called active components and electronics a combination of active and passive components.

why is negative range given to measure the steam drum level Why we use 0-24VdC in Electronic Circuits and Instrumentation Transmitters? why is the sleeve of the cable used for? why pneumatic control signal output is use 0.2 to 1 kg/cm2 what is the difference between scaler and vector drive what is the diffrence between mmwc and kg/cm2 for pressure measurment when we are using mmwc and

when kg/cm2 and why? what is the reason

Electrical:-

what is oti and wti Why transfomer reting in KVA and Motor in HP why the no.of slots in stator in not equal to the no. of stator in rotor in induction motor? what is d meaning of inrush current of a trafo ? how u can calculate this ?

IF we want to replace I/C bay at our 220 kv substation which is of 140 mw load capacity bay to be replaced by 400 mw capacity bay.other than CT(1200/1) what are the other equipment i have to replace.

what is two wattmeter test What is Difference Between Induction Motor & Servo Motor In AC Drives How can change & control its output Frequency? What is mean by PID controller? And what is its Long form? Why HT cable have only 3 core ? what is the highest transmission voltage in india??? How to calculate the transmission losses incase of overhead transmission lines? Why is the size of Hole of the Earth point in the Plug Point Bigger than phase and Neutral

Mechanical:-

what is BHP? what is the relationship between psi,cfm & bar in the air compressor? what is manufacturing cost of an aeroplane? which is heavier 1kg. of iron or 1kg. of cotton?and why? Pls send me the 10 years technical question paper of Jindal steel power to my email id In a thermal power plant : Why the Deaerator is placed at height and mostly at 15.5mtr? How much stack emmission through your chimney and what is the state govt norms ?

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