19630746 ntpc summer training report

7/31/2019 19630746 Ntpc Summer Training Report

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SUMMER TRAINING REPORT15th June to 25th July

Submitted By:-Shivani Chhabra

7225ECE-2(5th sem)


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ABOUT THE COMPANY

CORPORATE VISION :A world class integrated power major, powering India's growth withincreasing global presence.

CORE VALUES :B- Business ethicsC-Customer focusO-Organisational & professional prideM-Mutual respect & trustI-Innovation & speedT-Total quality for excellence

NTPC Limited is the largest thermal power generating company of India,public sector company. It was incorporated in the year 1975 toaccelerate power development in the country as a wholly ownedcompany of the Government of India. At present, Government of Indiaholds 89.5% of the total equity shares of the company and the balance10.5% is held by FIIs, Domestic Banks, Public and others. Within a spanof 31 years, NTPC has emerged as a truly national power company, withpower generating facilities in all the major regions of the country.


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NTPC LimiteD

Type Public

Founded 1975

Headquart

ersDelhi, India

Key peopleR S Sharma, Chairman & Managing

Director

Industry Electricity generation

Products Electricity

RevenueINR 416.37 billion (2008) or USD

18.15 billion

Net

income

INR 70.47 billion (2008) or USD

1.89 billion

Employees 23867 (2006)

Website http://www.ntpc.co.in
http://en.wikipedia.org/wiki/Types_of_business_entityhttp://en.wikipedia.org/wiki/Public_companyhttp://en.wikipedia.org/wiki/Delhihttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Electricity_generationhttp://en.wikipedia.org/wiki/Product_(business)http://en.wikipedia.org/wiki/Revenuehttp://en.wikipedia.org/wiki/Rs.http://en.wikipedia.org/wiki/USDhttp://en.wikipedia.org/wiki/Net_incomehttp://en.wikipedia.org/wiki/Net_incomehttp://en.wikipedia.org/wiki/Rs.http://en.wikipedia.org/wiki/USDhttp://en.wikipedia.org/wiki/Employmenthttp://en.wikipedia.org/wiki/Websitehttp://www.ntpc.co.in/http://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/File:Ntpc.jpghttp://en.wikipedia.org/wiki/Types_of_business_entityhttp://en.wikipedia.org/wiki/Public_companyhttp://en.wikipedia.org/wiki/Delhihttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Electricity_generationhttp://en.wikipedia.org/wiki/Product_(business)http://en.wikipedia.org/wiki/Revenuehttp://en.wikipedia.org/wiki/Rs.http://en.wikipedia.org/wiki/USDhttp://en.wikipedia.org/wiki/Net_incomehttp://en.wikipedia.org/wiki/Net_incomehttp://en.wikipedia.org/wiki/Rs.http://en.wikipedia.org/wiki/USDhttp://en.wikipedia.org/wiki/Employmenthttp://en.wikipedia.org/wiki/Websitehttp://www.ntpc.co.in/


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EVOLUTION OF NTPC

NTPC was set up in 1975 with 100% ownership by the

Government of India. In the last 30 years, NTPC has growninto the largest power utility in India.

In 1997, Government of India granted NTPC status of Navratnabeing one of the nine jewels of India, enhancing the powers to the

Board of Directors.

NTPC became a listed company with majority Governmentownership of 89.5%.

NTPC becomes third largest by Market Capitalisation of listed

companies

The company rechristened as NTPC Limited in line with its

changing business portfolio and transform itself from a thermal

power utility to an integrated power utility.

NTPC is the largest power utility in India, accounting for about 20% of

Indias installed capacity.

1975

1997

2005

2004


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THERMAL POWER PLANT

A thermal power station consists of all the equipments and a subsystemrequired to produce electricity by using a steam generating boiler fired

with fossil fuels or befouls to drive an electric generator. Some prefer touse the term ENERGY CENTER because such facilities convert form ofenergy like nuclear energy, gravitational potential energy or heatenergy (derived from the combustion of fuel) into electrical energy.Typical diagram of a coal power thermal power station-

1. Cooling water pump2. Three phase transmission line3. Step up transformer4. Electrical generator5. Low pressure steam

6. Boiler feed water pump7. Surface condenser8. Intermediate pressure steam turbine9. Steam control valve10. High pressure steam turbine11. Deaerator feed water heater12. Coal conveyer13. Coal hopper14. Coal pulverizer15. Boiler steam drum16. Boiler ash hopper

17. Super heater18. Force draught (draft) fan19. Reheater20. Combustion air intake21. Economiser22. Airpreheater23. Precipitator24. Induced draught(draft) fan25. Fuel gas stack

The description of some of the components above is as follows:

1. Cooling towers-Cooling towers are eveporative coolers used for cooling water. Coolingtower use evaporation of water to reject heat from processes such ascooling the circulaing water used in oil refineries, chemical plants, powerplants, etc. The tower vary in size from small roof top units to verylarge hyperboloid structures that can be upto 200 meters tall and 100meters in diameter, or rectangular structure that can be over 40 meterstall and 80 meters long. Smaller towers are normally factory built while


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larger ones are constructed on site. The primary use of large, industrialcooling tower system is to remove the heat absorbed in the circulatingwater system used in power plants, petroleum refineries, petrochemicaland chemical plants, natural gas processing plants and other industrialfacilities.

The absorbed heat is rejected to the atmosphere by the evaporation ofsome of the cooling water in mechanical forced draft or induced drafttowers or in natural draft hyperbolic shaped cooling towers as seen atmost nuclear power plants.

2. Three phase transmission line-Three phase electric power is a common method of electric powertransmission. It is a type of polyphase system mainly used for powermotors and many other devices. In a three phase system, three circuitsreach their instantaneous peak values at different times. Taking oneconductor as reference, the other two conductor are delayed in time by

one-third and two-third of cycle of the electrical current. This delaybetween phases has the effect of giving constant power over each cycleof the current and also makes it impossible to produce a rotatingmagnetic field in an electric motor. At the power station, an electricgenerator converts mechanical power into a set of electric currents onefrom each electromagnetic coil or winding of the generator. The currentsare sinusoidal functions of time, all at the same frequency but offset intime to give different phases. In a three phase system, the phases arespaced equally giving a phase separation of one-third of one cycle.Generators output at a voltage that ranges from hundreds of volts to30,000 volts. At the power station. Transformers step-up this voltage for

suitable transmission. After numerous further conversions in thetransmission and distribution network, the power is finally transformedto standard mains voltage i.e. the household voltage. The power mayalready have been split into single phase at this point or it may be stillthree phase. Where the step-down is three phase. The output of thetransformer is usually star connected with the standard mains voltagebeing the phase neutral voltage.

3. Electrical generator-An electrical generator is a device that coverts mechanical energy toelectrical energy, using electromagnetic induction whereas electrical

energy is converted to mechanical energy with the help of electricmotor. The source of mechanical energy may be a reciprocating turbinesteam engine. Turbines are made in variety of sizes ranging from small1 hp(0.75 kW) used as mechanical drives for pumps, compressors andother shaft driven equipment to 2,000,000 hp(1,500,000 kW) turbinesused to generate electricity.

4. Boiler Feed Pump-


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A Boiler Feed Pump is a specific type of pump used to pump water intosteam boiler. The water may be freshly supplied or retuningcondensation of steam produced by the boiler. These pumps arenormally high pressure units that use suction from a condensate returnsystem and can be of centrifugal pump type or positive displacement

type. Construction and Operation feed water pumps range in size uptomany horsepower and the electric motor is usually separated from thepump body by some form of mechanical coupling. Large industrialcondensate pumps may also serve as the feed water pump. In eithercase, to force water into the boiler, the pump must generate sufficientpressure to overcome the steam pressure developed by the boiler. Thisis usually accomplished through the use of centrifugal pump. Feed waterpumps usually run intermittently and are controlled by a float switch orother similar level-sensing device energizing the pump when it detect alowered liquid level in the boiler substantially increased. Some pumpscontain a two stage switch. As liquid lowers to the trigger point of the

first stage, the pump is activated.If the liquid continues to drop (perhaps because the pump has failed, itssupply has been cut-off or exhausted, or its discharge is blocked),thesecond stage will be triggered. This stage may switch off the boilerequipment (preventing the boiler from running dry and overheating),trigger an alarm or both.

5. Control valves-Control Valves are the valves used within industrial plants andelsewhere to control operating conditions such as temperature,

pressure, flow and liquid level by fully or partially opening or closing inresponse to signals received from controllers that compares a setpoint to a process variable whose value is provided by sensors thatmonitor changes in such conditions. The opening or closing of controlvalves is done by means of electrical, hydraulic or pneumatic systems.

6. Deaerator-A Deaerator is a device for air removal and used to remove dissolvedgases from boiler feed water to make it non-corrosive. A deaeratortypically includes a vertical domed deaeration section as the deaerationfeed water tank. A steam generating boiler requires that the circulating

steam, condensate and feed water should be devoid of dissolved gases,particularly corrosive ones and dissolved or suspended solids. The gaseswill give rise to corrosion of the metal. The solids will deposit on heatingsurfaces giving rise to localized heating and tube ruptures due tooverheating. Deaerator level and pressure must be controlled byadjusting control valves-the level by regulating condensate flow andpressure by regulating steam flow. Most deaerators guarantee that if


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operated properly, oxygen in deaerated water will not exceed 7ppb byweight.

7. Feed Water Heater-A feed water heater is a power plant component used to pre heat water

delivered to a steam generating boiler. Feed water heater improves theefficiency of the system. This reduces plant operating costs and alsohelps to avoid thermal shock to boiler metal when the feed water isintroduced back into the steam cycle. Feed water heaters allow the feedwater to be brought upto the saturation temperature very gradually.This minimizes the inevitable irreversibility associated with heat transferto the working fluid(water). A belt conveyer consists of two pulleys, witha continuous loop of material- the conveyer belt that rotates aroundthem. The pulleys are powered, moving the belt and the material on thebelt forward. Conveyer belts are extensively used to transport industrialand agricultural material, such as grain, coal, ores, etc.

8. Pulverizer-A pulverizer is a device for grinding coal for combustion in a furnace in afossil fuel power plant.

9. Boiler Steam Drum-Steam Drums are a regular feature of water tube boilers. It is reservoirof water/steam at the top end of the water tubes in the water-tubeboiler. They store the steam generated in the water tubes and act as aphase separator for the steam/water mixture. The difference in densitiesbetween hot and cold water helps in the accumulation of the hotter-

water/and saturated steam into steam drum. Made from high-gradesteel (probably stainless) and its working involves temperatures 390Cand pressure well above 350psi (2.4MPa). The separated steam is drawnout from the top section of the drum. Saturated steam is drawn off thetop of the drum. The steam will re-enter the furnace in through a superheater, while the saturated water at the bottom of steam drum flowsdown to the mud-drum /feed water drum by down comer tubesaccessories include a safety valve, water level indicator and fuse plug. Asteam drum is used in the company of a mud-drum/feed water drumwhich is located at a lower level. So that it acts as a sump for the sludgeor sediments which have a tendency to the bottom.

10.Super Heater-A Super heater is a device in a steam engine that heats the steam

generated by the boiler again increasing its thermal energy anddecreasing the likelihood that it will condense inside the engine. Superheaters increase the efficiency of the steam engine, and were widelyadopted. Steam which has been superheated is logically known assuperheated steam; non-superheated steam is called saturated steam or


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wet steam; Super heaters were applied to steam locomotives in quantityfrom the early 20th century, to most steam vehicles, and so stationarysteam engines including power stations.

11.Economizers-

Economizer, or in the UK economizer, are mechanical devices intendedto reduce energy consumption, or to perform another useful functionlike preheating a fluid. The term economizer is used for other purposesas well. Boiler, power plant, and heating, ventilating and airconditioning. In boilers, economizer are heat exchange devices that heatfluids , usually water, up to but not normally beyond the boiling point ofthe fluid. Economizers are so named because they can make use of theenthalpy and improving the boilers efficiency. They are a device fittedto a boiler which saves energy by using the exhaust gases from theboiler to preheat the cold water used the fill it (the feed water). Modernday boilers, such as those in cold fired power stations, are still fitted with

economizer which is decedents of Greens original design. In this contextthey are turbines before it is pumped to the boilers. A commonapplication of economizer is steam power plants is to capture the wastehit from boiler stack gases (flue gas) and transfer thus it to the boilerfeed water thus lowering the needed energy input , in turn reducing thefiring rates to accomplish the rated boiler output . Economizer lowerstack temperatures which may cause condensation of acidic combustiongases and serious equipment corrosion damage if care is not taken intheir design and material selection.

12.Air Preheater-

Air preheater is a general term to describe any device designed to heatair before another process (for example, combustion in a boiler). Thepurpose of the air preheater is to recover the heat from the boiler fluegas which increases the thermal efficiency of the boiler by reducing theuseful heat lost in the fuel gas. As a consequence, the flue gases arealso sent to the flue gas stack (or chimney) at a lower temperatureallowing simplified design of the ducting and the flue gas stack. It alsoallows control over the temperature of gases leaving the stack.

13.Precipitator-An Electrostatic precipitator (ESP) or electrostatic air cleaner is a

particulate device that removes particles from a flowing gas (such Asair) using the force of an induced electrostatic charge. Electrostaticprecipitators are highly efficient filtration devices, and can easily removefine particulate matter such as dust and smoke from the air steam.ESPs continue to be excellent devices for control of many industrialparticulate emissions, including smoke from electricity-generatingutilities (coal and oil fired), salt cake collection from black liquor boilersin pump mills, and catalyst collection from fluidized bed catalytic


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crackers from several hundred thousand ACFM in the largest coal-firedboiler application. The original parallel plate-Weighted wire design(described above) has evolved as more efficient ( and robust) dischargeelectrode designs were developed, today focusing on rigid dischargeelectrodes to which many sharpened spikes are attached , maximizing

corona production. Transformer rectifier systems apply voltages of 50-100 Kilovolts at relatively high current densities. Modern controlsminimize sparking and prevent arcing, avoiding damage to thecomponents. Automatic rapping systems and hopper evacuationsystems remove the collected particulate matter while on line allowingESPs to stay in operation for years at a time.

14.Fuel gas stack-A Fuel gas stack is a type of chimney, a vertical pipe, channel or similarstructure through which combustion product gases called fuel gases areexhausted to the outside air. Fuel gases are produced when coal, oil,

natural gas, wood or any other large combustion device. Fuel gas isusually composed of carbon dioxide (CO2) and water vapor as well asnitrogen and excess oxygen remaining from the intake combustion air. Italso contains a small percentage of pollutants such as particulatesmatter, carbon mono oxide, nitrogen oxides and sulfur oxides. The fluegas stacks are often quite tall, up to 400 meters (1300 feet) or more, soas to disperse the exhaust pollutants over a greater aria and therebyreduce the concentration of the pollutants to the levels required bygovernmental environmental policies and regulations.

ELECTRICITY GENERATION PROCESS(A BASIC OVERVIEW)

At NTPC (Badarpur) the man two paths are the flue gas or air cycle and steam or

condensate paths.

CAPITAL OVERHAUL

NTPC has been in news due to extensive load sheds in many areas in delhi and the main

cause behind these load sheds was the capital overhaul of one of 210 MW units. Unit IV

was under an extensive check , which has caused shut down of the plant and the plant, wasdismantled completely to change the old parts and cleaning up the whole unit. But capital

overhaul has no meaning because such a deep checking of the plant happens once in five to

seven years.

HOW ELECTRICITY IS GENERATED?


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Thermal power station burns fuel and uses the resultant heat to raise steam which drives the

TURBO GENERATOR. The fuel may be fossil(coal,oil,natural gas) or it may be

fissionable, whichever fuel is used, the objective is same to convert the mechanical energyinto electricity by rotating a magnet inside a set of winding.

COAL TO STAEM

Its other raw materials are air and water. The coal brought to the station by trains or by

other means, travels handling plant by conveyer belts, travels from pulverizing mills, whichgrind it as fine as the face powder of size upto 20 microns. The finely produced coal mixed

with preheated air is then blown into the boiler by a fan called primary air fan where it

burns more like a gas than as a solid, in the conventional domestic or industrial grate, with

additional amount of air, called secondary air supply, by forced draft fan.

As coal is ground so finally the resultant ash is also a fine powder. Some of it binds

together to form pumps, which falls into ash pits at the bottom of the furnace. The water-

quenched ash from the bottom is conveyed to pits for subsequent disposal or sale. Most ofash, still in fine partical form is carried out of boilers to the precipitator as dust, where

electrodes charged with high voltage electricity trap it. The dust is then conveyed to water

to disposal area or to bunker for sale while the clean flue gases are passed on through IP

fans to be discharged through chimneys.

The heat released from the coal has been absorbed by the many kilometers tubing which

line the boiler walls. Inside the tubes the boiler feed water, which is transformed by heatinto staemat high temperature and pressure.. The steam superheated in further tubes

(superheaters) passes to turbine where it is discharged through the nozzle on the turbine

blades. Just as the energy of wind turns the sail of the windmill, the energy of steam

striking the blade makes the turbine rotate.

Coupled to the end of the turbine is the rotor of the generator. The rotor is housed inside

the stator having heavy coils of the bars in which electricity is produced through themovement of magnetic field created by the rotor. Electricity passes from stator windings to

step-up transformer which increases its voltage so that it can be transmited efficiently over

lines of grid.

The staem which has given up its heat energy is cahnged back into water in a condenser so

that it is ready for re-use. The condenser contains many kilometers of tubing through whichcold water is constantly pumped. The staem passing around the tubes looses heat.Thus it is

rapidly changed back into water.

But, the two lots of water, that is, the boiler feed and cooling water must never mix.

Cooling water is drawn from river- bed, but the boiler feed water must be absolutely pure,

far purer than the water we drink(de-mineralized water), otherwise it may damage theboiler tubes.


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TABLES OF CYCLES COAL CYCLE


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CONDENSATE CYCLE


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FEED WATER CYCLE


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STEAM CYCLE


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CONTROL AND INSTRUMENTATIONThis division basically calibrates various instruments and takes care ofany faults occur in any of the auxiliaries in the plant.


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This department is the brain of the plant because from the relays totransmitters followed by the electronic computation chipsets andrecorders and lastly the controlling circuitry, all fall under this.

Instrumentation can be well defined as a technology of using instruments to measure andcontrol the physical and chemical properties of a material.

Control and instrumentation has following labs:

1. Manometry lab

2. Protection and interlocks lab

3. Automation lab

4. Electronics lab

5. Water treatment plant

6. Furnaces Safety Supervisory System Lab

1. Manometry lab

Transmitters- Transmitter is used for pressure measurements of gases and liquids,

its working principle is that the input pressure is converted into electrostatic

capacitance and from there it is conditioned and amplified. It gives an output of 4-

20 ma DC. It can be mounted on a pipe or a wall. For liquid or steam measurement

transmitters is mounted below main process piping and for gas measurement

transmitter is placed above pipe.

Manometer- Its a tube which is bent, in U shape. It is filled with a liquid. This

device corresponds to a difference in pressure across the two limbs.

Bourden Pressure Gauge- Its an oval section tube. Its one end is fixed. It is

provided with a pointer to indicate the pressure on a calibrated scale. It is of two

types : (a) Spiral type : for low pressure measurement and (b) Helical type : for high

pressure measurement

2. Protection and Interlock Lab

Interlocking- It is basically interconnecting two or more equipments so that if one

equipments fails other one can perform the tasks. This type of interdependence is

also created so that equipments connected together are started and shut down in the

specific sequence to avoid damage. For protection of equipments tripping are


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provided for all the equipments. Tripping can be considered as the series of

instructions connected through OR GATE. When The main equipments of this lab

are relay and circuit breakers. Some of the instrument uses for protection are: 1.

RELAY It is a protective device. It can detect wrong condition in electrical circuits

by constantly measuring the electrical quantities flowing under normal and faulty

conditions. Some of the electrical quantities are voltage, current, phase angle and

velocity. 2. FUSES It is a short piece of metal inserted in the circuit, which melts

when heavy current flows through it and thus breaks the circuit. Usually silver is

used as a fuse material because: a) The coefficient of expansion of silver is very

small. As a result no critical fatigue occurs and thus the continuous full capacity

normal current ratings are assured for the long time. b) The conductivity of the

silver is unimpaired by the surges of the current that produces temperatures just

near the melting point. c) Silver fusible elements can be raised from normal

operating temperature to vaporization quicker than any other material because of its

comparatively low specific heat.

Miniature Circuit Breaker- They are used with combination of the control circuits

to. a) Enable the staring of plant and distributors. b) Protect the circuit in case of a

fault. In consists of current carrying contacts, one movable and other fixed. When a

fault occurs the contacts separate and are is stuck between them. There are three

types of -MANUAL TRIP - THERMAL TRIP - SHORT CIRCUIT TRIP.

Protection and Interlock System- 1. HIGH TENSION CONTROL CIRCUIT For

high tension system the control system are excited by separate D.C supply. For

starting the circuit conditions should be in series with the starting coil of the

equipment to energize it. Because if even a single condition is not true then system

will not start. 2. LOW TENSION CONTROL CIRCUIT For low tension system the

control circuits are directly excited from the 0.415 KV A.C supply. The same

circuit achieves both excitation and tripping. Hence the tripping coil is provided for

emergency tripping if the interconnection fails.

3. Automation Lab

This lab deals in automating the existing equipment and feeding routes. Earlier,


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the old technology dealt with only (DAS) Data Acquisition System and came to be known

as primary systems. The modern technology or the secondary systems are coupled with

(MIS) Management Information System. But this lab universally applies the pressure

measuring instruments as the controlling force. However, the relays are also provided but

they are used only for protection and interlocks.

4. Pyrometry Lab

Liquid in glass thermometer - Mercury in the glass thermometer boils at 340 degree

Celsius which limits the range of temperature that can be measured. It is L shaped

thermometer which is designed to reach all inaccessible places.

Ultra violet censor- This device is used in furnace and it measures the intensity of

ultra violet rays there and according to the wave generated which directly indicates

the temperature in the furnace.

Thermocouples - This device is based on SEEBACK and PELTIER effect. It

comprises of two junctions at different temperature. Then the emf is induced in the

circuit due to the flow of electrons. This is an important part in the plant.

RTD(Resistance temperature detector) - It performs the function of thermocouple

basically but the difference is of a resistance. In this due to the change in the

resistance the temperature difference is measured. In this lab, also the measuringdevices can be calibrated in the oil bath or just boiling water (for low range

devices) and in small furnace (for high range devices).

5. Furnace Safety and Supervisory System Lab

This lab has the responsibility of starting fire in the furnace to enable the burning of coal.

For first stage coal burners are in the front and rear of the furnace and for the second and

third stage corner firing is employed. Unburnt coal is removed using forced draft or

induced draft fan. The temperature inside the boiler is 1100 degree Celsius and its height is

18 to 40 m. It is made up of mild steel. An ultra violet sensor is employed in furnace to

measure the intensity of ultra violet rays inside the furnace and according to it a signal in

the same order of same mV is generated which directly indicates the temperature of the

furnace. For firing the furnace a 10 KV spark plug is operated for ten seconds over a spray

of diesel fuel and pre-heater air along each of the feeder-mills. The furnace has six feeder


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mills each separated by warm air pipes fed from forced draft fans. In first stage indirect

firing is employed that is feeder mills are not fed directly from coal but are fed from three

feeders but are fed from pulverized coalbunkers. The furnace can operate on the minimum

feed from three feeders but under not circumstances should any one be left out under

operation, to prevent creation of pressure different with in the furnace, which threatens to

blast it.

6. Electronics Lab

This lab undertakes the calibration and testing of various cards. It houses various types of

analytical instruments like oscilloscopes, integrated circuits, cards auto analyzers

etc.Various processes undertaken in this lab are: 1. Transmitter converts mV to mA. 2.

Auto analyzer purifies the sample before it is sent to electrodes. It extracts the magnetic

portion.

AUTOMATION AND CONTROL SYSTEM

AUTOMATION: THE DEFINITION


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The word automation is widely used today in relation to various types of applications, such

as office automation, plant or process automation.

This subsection presents the application of a control system for the automation of a process

/ plant, such as a power station. In this last application, the automation actively controls the

plant during the three main phases of operation: plant start-up, power generation in stable

or put During plant start-up and shut-down, sequence controllers as well as long range

modulating controllers in or out of operation every piece of the plant, at the correct time

and in coordinated modes, taking into account safety as well as overstressing limits.

During stable generation of power, the modulating portion of the automation system keeps

the actual generated power value within the limits of the desired load demand.

During major load changes, the automation system automatically redefines new set points

and switches ON or OFF process pieces, to automatically bring the individual processes in

an optimally coordinated way to the new desired load demand. This load transfer is

executed according to pre- programmed adaptively controlled load gradients and in a safe

way.

AUTOMATION: THE BENEFITS

The main benefits of plant automation are to increase overall plant availability and

efficiency. The increase of these two factors is achieved through a series of featuressummarized as follows:

Optimisation of house load consumption during plant start- up, shut-down andoperation, via:


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Faster plant start-up through elimination of control errors creating delays.

Faster sequence of control actions compared to manual ones. Figures 1 shows

the sequence of a rapid restart using automation for a typical coal-fired station.

Even a well- trained operator crew would probably not be able to bring the

plant to full load in the same time without considerable risks.

Co-ordination of house load to the generated power output.

Ensure and maintain plant operation, even in case of disturbances in the controlsystem, via:

Coordinated ON / OFF and modulating control switchover capability from a

sub process to a redundant one.

Prevent sub-process and process tripping chain reaction following a process

component trip.

Reduce plant / process shutdown time for repair and maintenance as well asrepair costs, via:

Protection of individual process components against overstress (in a stable or

unstable plant operation).

Bringing processes in a safe stage of operation, where process components are

protected against overstress

PROCESS STRUCTURE

Analysis of processes in Power Stations and Industry advocates the advisability of dividing

the complex overall process into individual sub-processes having distinctly defined


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functions. This division of the process in clearly defined groups, termed as FUNCTIONAL

GROUPS, results in a hierarchical process structure. While the hierarchical structure is

governed in the horizontal direction by the number of drives (motorised valves, fans,

dampers, pumps, etc.) in other words the size of the process; in the vertical direction, there

is a distinction made between three fundamental levels, these being the: -

Drive Level

Function Group Level

Unit Level.

To the Drive Level, the lowest level, belong the individual process equipment and

associated electrical drives.

The Function Group is that part of the process that fulfils a particular defined task e.g.,

Induced Draft Control, Feed Water Control, Blooming Mill Control, etc. Thus at the time

of planning it is necessary to identify each function group in a clear manner by assigning it

to a particular process activity. Each function group contains a combination of its

associated individual equipment drives. The drive levels are subordinate to this level. The

function groups are combined to obtain the overall process control function at the Unit

Level.

The above three levels are defined with regard to the process and not from the control point

of view.

CONTROL SYSTEM STRUCTURE

The primary requirement to be fulfilled by any control system architecture is that it be

capable of being organized and implemented on true process-oriented lines. In other words,

the control system structure should map on to the hierarchy process structure.


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BHELs PROCONTROL P, a microprocessor based intelligent remote multiplexing

system, meets this requirement completely.

SYSTEM OVERVIEW

The control and automation system used here is a micro based intelligent multiplexing

system This system, designed on a modular basis, allows to tighten the scope of control

hardware to the particular control strategy and operating requirements of the process

Regardless of the type and extent of process to control provides system uniformity and

integrity for:

Signal conditioning and transmission

Modulating controls

CONTROL AND MONITORING MECHANISMS

There are basically two types ofProblems faced in a Power Plant

Metallurgical

Mechanical

Mechanical Problemcan be related to Turbines that is the max speed permissible for a

turbine is 3000 rpm , so speed should be monitored and maintained at that level

Metallurgical Problem can be view as the max Inlet Temperature for Turbile is 1060 oC so

temperature should be below the limit.

Monitoring of all the parameters is necessary for the safety of both:

Employees


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Machines

So the Parameters to be monitored are :

Speed

Temperature

Current

Voltage

Pressure

Eccentricity

Flow of Gases Vaccum Pressure

Valves

Level

Vibration

PRESSURE MONITORING

Pressure can be monitored by three types of basic mechanisms

Switches

Gauges

Transmitter type

For gauges we use Bourden tubes : The Bourdon Tube is a non liquid pressure

measurement device. It is widely used in applications where inexpensive static pressure

measurements are needed.


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A typical Bourdon tube contains a curved tube that is open to external pressure input on

one end and is coupled mechanically to an indicating needle on the other end, as shown

schematically below.

Typical Bourdon Tube Pressure Gages

For Switches pressure swithes are used and they can be used for digital means of

monitoring as swith being ON is referred as high and being OFF is as low.

All the monitored data is converted to either Current or Voltage parameter.

The Plant standard for current and voltage are as under

Voltage : 0 10 Volts range

Current : 4 20 milliAmperes

We use 4mA as the lower value so as to check for disturbances and wire breaks.

Accuracy of such systems is very high .

ACCURACY : + - 0.1 %

The whole system used is SCADA baseD.Programmable Logic Circuits ( PLCs) are used in the process as they are the heardt of

Instrumentation .

Pressure

Electricity StartHL switch

LL switch

AND


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Level low Pressure in line

Level High

High level

pump

Electricity StopPressure

Electricity

BASIC PRESSURE CONTROL MECHANISM

TEMPERATURE MONITORING

We can use Thernocouples or RTDs for temperature monitoring

Normally RTDs are used for low temperatures.

Thermocoupkle selection depends upon two factors:

Temperature Range

Accuracy Required

Normally used Thermocouple is K Type Thermocouple:

Chromel (Nickel-Chromium Alloy) / Alumel (Nickel-Aluminium Alloy)

This is the most commonly used general purpose thermocouple. It is inexpensive and,

owing to its popularity, available in a wide variety of probes. They are available in the

200 C to +1200 C range. Sensitivity is approximately 41 V/C.

RTDs are also used but not in protection systems due to vibrational errors.

OR


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We pass a constant curre t through the RTD. So that if R changes then the Voltage also

changes

RTDs used in Industries are Pt100 and Pt1000

Pt100 : 0 0C 100 ( 1 = 2.5 0C )

Pt1000 : 0 0C - 1000

Pt1000 is used for higher accuracy

The gauges used for Temperature measurements are mercury filled Temperature gauges.

For Analog medium thermocouples are used

And for Digital medium Switches are used which are basically mercury switches.

FLOW MEASUREMENT

Flow measurement does not signify much and is measured just for metering purposes and

for monitoring the processes

ROTAMETERS:

A Rotameter is a device that measures the flow rate of liquid or gas in a closed tube. It is

occasionally misspelled as 'rotometer'.

It belongs to a class of meters called variable area meters, which measure flow rate by

allowing the cross sectional area the fluid travels through to vary, causing some measurable

effect.

A rotameter consists of a tapered tube, typically made of glass, with a float inside that is

pushed up by flow and pulled down by gravity. At a higher flow rate more area (between

the float and the tube) is needed to accommodate the flow, so the float rises. Floats are

made in many different shapes, with spheres and spherical ellipses being the most


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common. The float is shaped so that it rotates axially as the fluid passes. This allows you to

tell if the float is stuck since it will only rotate if it is not.

For Digital measurements Flap system is used.

For Analog measurements we can use the following methods :

Flowmeters

Venurimeters / Orifice meters

Turbines

Massflow meters ( oil level )

Ultrasonic Flow meters

Magnetic Flowmeter ( water level )

Selection of flow meter depends upon the purpose , accuracy and liquid to be measured so

different types of meters used.

Turbine type are the simplest of all.

They work on the principle that on each rotation of the turbine a pulse is generated and that

pulse is counted to get the flow rate.

VENTURIMETERS :


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Referring to the diagram, using Bernoulli's equation in the special case of incompressible

fluids (such as the approximation of a water jet), the theoretical pressure drop at the

constriction would be given by (/2)(v22 - v1

2).

And we know that rate of flow is given by:

Flow = k (D.P)

Where DP is Differential Presure or the Pressure Drop.

CONTROL VALVES

A valve is a device that regulates the flow of substances (either gases, fluidized solids,

slurries, or liquids) by opening, closing, or partially obstructing various passageways.

Valves are technically pipe fittings, but usually are discussed separately.

Valves are used in a variety of applications including industrial, military, commercial,

residential, transportation. Plumbing valves are the most obvious in everyday life, but

many more are used.


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Some valves are driven by pressure only, they are mainly used for safety purposes in steam

engines and domestic heating or cooking appliances. Others are used in a controlled way,

like in Otto cycle engines driven by a camshaft, where they play a major role in engine

cycle control.

Many valves are controlled manually with a handle attached to the valve stem. If the handle

is turned a quarter of a full turn (90) between operating positions, the valve is called a

quarter-turn valve. Butterfly valves, ball valves, and plug valves are often quarter-turn

valves. Valves can also be controlled by devices called actuators attached to the stem. They

can be electromechanical actuators such as an electric motor or solenoid, pneumatic

actuators which are controlled by air pressure, orhydraulic actuators which are

controlled by the pressure of a liquid such as oil or water.

So there are basically three types of valves that are used in power industries besides the

handle valves. They are :

Pneumatic Valves they are air or gas controlled which is compressed to turn

or move them

Hydraulic valves they utilize oil in place of Air as oil has better compression

Motorised valves these valves are controlled by electric motors

FURNACE SAFEGUARD SUPERVISORY SYSTEM

FSSS is also called as Burner Management System (BMS). It is a microprocessor based

programmable logic controller of proven design incorporating all protection facilitiesrequired for such system. Main objective of FSSS is to ensure safety of the boiler.

The 95 MW boilers are indirect type boilers. Fire takes place in front and in rear side.

Thats why its called front and rear type boiler.

The 210 MW boilers are direct type boilers (which means that HSD is in direct contact

with coal) firing takes place from the corner. Thus it is also known as corner type boiler.

IGNITER SYSTEM

Igniter system is an automatic system, it takes the charge from 110kv and this spark is

brought in front of the oil guns, which spray aerated HSD on the coal for coal combustion.


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There is a 5 minute delay cycle before igniting, this is to evacuate or burn the HSD. This

method is known as PURGING.

PRESSURE SWITCH

Pressure switches are the devices that make or break a circuit. When pressure is applied ,the switch under the switch gets pressed which is attached to a relay that makes or break

the circuit.

Time delay can also be included in sensing the pressure with the help of pressure valves.Examples of pressure valves:

1. Manual valves (tap)

2. Motorized valves (actuator) works on motor action

3. Pneumatic valve (actuator) _ works due to pressure of compressed air

4. Hydraulic valve

19630746 ntpc summer training report

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