India‟s largest power company, NTPC was set up in 1975 to accelerate power
development in India. NTPC is emerging as a diversified power major with presence in
the entire value chain of the power generation business. Apart from power generation,
which is the mainstay of the company, NTPC has already ventured into consultancy,
power trading, ash utilization and coal mining. NTPC ranked 341st
in the „2010, Forbes
Global 2000‟ ranking of the World‟s biggest companies. NTPC became a Maharatna
company in May, 2010, one of the only four companies to be awarded this status.
The total installed capacity of the company is 39,174 MW (including JVs) with 16 coal
based and 7 gas based stations, located across the country. In addition under JVs, 7
stations are coal based & another station uses naptha/LNG as fuel. The company has set
a target to have an installed power generating capacity of 1,28,000 MW by the year 2032.
The capacity will have a diversified fuel mix comprising 56% coal, 16% Gas, 11%
Nuclear and 17% Renewable Energy Sources(RES) including hydro. By 2032, non-fossil
fuel based generation capacity shall make up nearly 28% of NTPC‟s portfolio.
NTPC has been operating its plants at high efficiency levels. Although the company has
17.75% of the total national capacity, it contributes 27.40% of total power generation due
to its focus on high efficiency.
In October 2004, NTPC launched its Initial Public Offering (IPO) consisting of 5.25% as
fresh issue and 5.25% as offer for sale by Government of India. NTPC thus became a
listed company in November 2004 with the Government holding 89.5% of the equity
share capital. In February 2010, the Shareholding of Government of India was reduced
from 89.5% to 84.5% through Further Public Offer. The rest is held by Institutional
Investors and the Public.
Strategies of NTPC
Introduction of steam generators (boilers) of the size of 800 MW.
Integrated Gasification Combined Cycle (IGCC) Technology.
Launch of Energy Technology Centre -A new initiative for development
of technologies with focus on fundamental R&D.
The company sets aside up to 0.5% of the profits for R&D.
Roadmap developed for adopting µClean Development.
Mechanism to help get / earn µCertified Emission Reduction.
Corporate Social Responsibility
As a responsible corporate citizen NTPC has taken up number of CSR initiatives.
NTPC Foundation formed to address Social issues at national level
NTPC has framed Corporate Social Responsibility Guidelines committing up
to0.5% of net profit annually for Community Welfare.
The welfare of project affected persons and the local population around
NTPC projects are taken care of through well drawn Rehabilitation and
Partnering government in various initiatives
Disseminate technologies to other players in the sector.
Consultant role ³Partnership in Excellence´ Programme for improvement of
PLF of 15 Power Stations of SEBs.
Rural Electrification work under Rajiv Gandhi Garmin Vidyutikaran.
Centre for Power Efficiency & Environment Protection.
NTPC is the second largest owner of trees in the country after the
“To be the world‟s largest and best power producer, powering India‟s growth.”
“Develop and provide reliable power, related products and services at competitive
prices, integrating multiple energy sources with innovative and eco-friendly
technologies and contribute to society.”
Core Values – BE COMMITTED
B Business Ethics
E Environmentally & Economically Sustainable
C Customer Focus
O Organizational & Professional Pride
M Mutual Respect & Trust
M Motivating Self & others
I Innovation & Speed
T Total Quality for Excellence
T Transparent & Respected Organization
NTPC Environment Policy
NTPC is committed to the environment, generating power at minimal environmental cost
and preserving the ecology in the vicinity of the plants. NTPC has undertaken massive a
forestation in the vicinity of its plants. Plantations have increased forest area and reduced
barren land. The massive a forestation by NTPC in and around its Ramagundam Power
station (2600 MW) have contributed reducing the temperature in the areas by about 3°c.
NTPC has also taken proactive steps for ash utilization. In 1991, it set up Ash Utilization
"Centre for Power Efficiency and Environment Protection- CENPEE" has been
established in NTPC with the assistance of United States Agency for International
Development- USAID. CENPEEP is efficiency oriented, eco-friendly and eco-nurturing
initiative - a symbol of NTPC's concern towards environmental protection and continued
commitment to sustainable power development in India. As a responsible corporate
citizen, NTPC is making constant efforts to improve the socio-economic status of
the people affected by its projects. Through its Rehabilitation and Resettlement
programmes, the company endeavors to improve the overall socio economic status
Project Affected Persons. NTPC was among the first Public Sector Enterprises to enter
into a Memorandum of Understanding-MOU with the Government in 1987-88. NTPC
has been placed under the 'Excellent category' (the best category) every year since the
MOU system became operative. Harmony between man and environment is the essence
of healthy life and growth. Therefore, maintenance of ecological balance and a pristine
environment has been of utmost importance to NTPC. It has been taking
various measures discussed below for mitigation of environment pollution due to power
As early as in November 1995, NTPC brought out a comprehensive document entitled
"NTPC Environment Policy and Environment Management System". Amongst the
guiding principles adopted in the document is company‟s proactive approach to
environment, optimum utilization of equipment, adoption of latest technologies and
continual environment improvement. The policy also envisages efficient utilization of
resources, thereby minimizing waste, maximizing ash utilization and providing green belt
all around the plant for maintaining ecological balance.
Environment Management, Occupational Health and Safety Systems:
NTPC has actively gone for adoption of best international practices on environment,
occupational health and safety areas. The organization has pursued the Environmental
Management System (EMS) ISO 14001 and the Occupational Health and Safety
Assessment System OHSAS 18001 at its different establishments. As a result of pursuing
these practices, all NTPC power stations have been certified for ISO 14001 & OHSAS
18001 by reputed national and international Certifying Agencies.
Pollution Control systems:
While deciding the appropriate technology for its projects, NTPC integrates many
environmental provisions into the plant design. In order to ensure that NTPC complies
with all the stipulated environment norms, various state-of-the-art pollution control
systems / devices as discussed below have been installed to control air and water
The ash left behind after combustion of coal is arrested in high efficiency Electrostatic
Precipitators (ESPs) and particulate emission is controlled well within the stipulated
norms. The ash collected in the ESPs is disposed to Ash Ponds in slurry form.
Flue Gas Stacks:
Tall Flue Gas Stacks have been provided for wide dispersion of the gaseous emissions
(SOX, NOX etc.) into the atmosphere.
In gas based NTPC power stations, NOX emissions are controlled by provision of Low-
NOX Burners (Dry or wet type) and in coal fired stations, by adopting best combustion
Neutralization pits have been provided in the Water Treatment Plant (WTP) for pH
correction of the Effluents before discharge into Effluent Treatment Plant (ETP) for
further treatment and use.
Coal Settling Pits / Oil Settling Pits:
In these Pits, coal dust and oil are removed from the effluents emanating from the Coal
Handling Plant (CHP), coal yard and Fuel Oil Handling areas before discharge into ETP.
DE & DS Systems:
Dust Extraction (DE) and Dust Suppression (DS) systems have been installed in all coal
fired power stations in NTPC to contain and extract the fugitive dust released in the Coal
Handling Plant (CHP).
Cooling Towers have been provided for cooling the hot Condenser cooling water in
closed cycle, Condenser Cooling Water (CCW) Systems. This helps in reduction in
thermal pollution and conservation of fresh water.
Ash Dykes & Ash Disposal systems:
Ash ponds have been provided at all coal based stations except Dadri where Dry Ash
Disposal System has been provided. Ash Ponds have been divided into lagoons and
provided with garlanding arrangement for changeover of the ash slurry feed points for
even filling of the pond and for effective settlement of the ash particles.
Ash in slurry form is discharged into the lagoons where ash particles get settled from the
slurry and clear effluent water is discharged from the ash pond. The discharged effluents
conform to standards specified by CPCB and the same is regularly monitored.
At its Dadri Power Station, NTPC has set up a unique system for dry ash collection and
disposal facility with Ash Mound formation. This has been envisaged for the first time in
Asia which has resulted in progressive development of green belt besides far less
requirement of land and less water requirement as compared to the wet ash disposal
Ash Water Recycling System:
Further, in a number of NTPC stations, as a proactive measure, Ash Water Recycling
System (AWRS) has been provided. In the AWRS, the effluent from ash pond is
circulated back to the station for further ash sluicing to the ash pond. This helps in
savings of fresh water requirements for transportation of ash from the plant.
The ash water recycling system has already been installed and is in operation at
Ramagundam, Simhadri, Rihand, Talcher Kaniha, Talcher Thermal, Kahalgaon, Korba
and Vindhyachal. The scheme has helped stations to save huge quantity of fresh water
required as make-up water for disposal of ash.
Dry Ash Extraction System (DAES):
Dry ash has much higher utilization potential in ash-based products (such as bricks,
aerated autoclaved concrete blocks, concrete, Portland pozzolana cement, etc.). DAES
has been installed at Unchahar, Dadri, Simhadri, Ramagundam, Singrauli, Kahalgaon,
Farakka, Talcher Thermal, Korba, Vindhyachal, Talcher Kaniha and BTPS.
Liquid Waste Treatment Plants & Management System:
The objective of industrial liquid effluent treatment plant (ETP) is to discharge lesser and
cleaner effluent from the power plants to meet environmental regulations. After primary
treatment at the source of their generation, the effluents are sent to the ETP for further
treatment. The composite liquid effluent treatment plant has been designed to treat all
liquid effluents which originate within the power station e.g. Water Treatment Plant
(WTP), Condensate Polishing Unit (CPU) effluent, Coal Handling Plant (CHP) effluent,
floor washings, service water drains etc. The scheme involves collection of various
effluents and their appropriate treatment centrally and re-circulation of the treated
effluent for various plant uses.
NTPC has implemented such systems in a number of its power stations such as
Ramagundam, Simhadri, Kayamkulam, Singrauli, Rihand, Vindhyachal, Korba, Jhanor
Gandhar, Faridabad, Farakka, Kahalgaon and Talcher Kaniha. These plants have helped
to control quality and quantity of the effluents discharged from the stations.
Sewage Treatment Plants & Facilities:
Sewage Treatment Plants (STPs) sewage treatment facilities have been provided at all
NTPC stations to take care of Sewage Effluent from Plant and township areas. In a
number of NTPC projects modern type STPs with Clarifloculators, Mechanical Agitators,
sludge drying beds, Gas Collection Chambers etc. have been provided to improve the
effluent quality. The effluent quality is monitored regularly and treated effluent
conforming to the prescribed limit is discharged from the station. At several stations
treated effluents of STPs are being used for horticulture purpose.
BADARPUR THERMAL POWER STATION was established on 1973 and it was the
part of Central Government. On 01/04/1978 is was given as No Loss No Profit Plant of
NTPC. Since then operating performance of NTPC has been considerably above the
national average. The availability factor for coal stations has increased from 85.03 % in
1997-98 to 90.09 % in 2006-07, which compares favorably with international standards.
The PLF has increased from 75.2% in1997-98 to 89.4% during the year 2006-07 which is
the highest since the inception of NTPC.
Badarpur thermal power station started with a single 95 mw unit. There were2moreunits
(95MWeach) installedinnext2 consecutiveyears.Nowithastotalfiveunitswithtotalcapacityof
720MW.OwnershipofBTPS wastransferredtoNTPC witheffect from 01.06.2006 through
GOIs Gazette Notification .
The power is supplied to a 220 KV network that is a part of the northern grid. The ten
circuits through which the power is evacuated from the plant are:
5. UP (Noida)
Given below are the details of unit with the year they’re installed.
Highway(Delhi-MathuraRoad)anditcomprisesof430hectares(678acres) borderedby the Agra
Canal from East and by Mathura-Delhi Road from West. However, the area for ash
I.P.stationandBallabgarhCoolingWaterisobtainedfromAgraCanal for the cooling
system. Additional 60 cusecs channel has also been constructed parallel to the Agra
Canal so as to obtain uninterrupted water supply during the slit removing operation in
OPERATION OF A POWER PLANT
As per FARADAY‟s Law-“Whenever the amount of magnetic flux linked with a circuit
changes, an EMF is produced in the circuit. Generator works on the principle of
producing electricity. To change the flux in the generator turbine is moved in a great
speed with steam.” To produce steam, water is heated in the boilers by burning the coal.
In a Badarpur Thermal PowerStation, steam is produced and used to spin a turbine that
operates a generator. Water is heated, turns into steam and spins a steam turbine which
drives an electrical generator. After it passes through the turbine, the steam is condensed
in a condenser; this is known as a Rankine cycle.
The electricity generated at the plant is sent to consumers through high-voltage power
lines The Badarpur Thermal Power Plant has Steam Turbine-Driven Generators which
has a collective capacity of 705MW. The fuel being used is Coal which is supplied from
the Jharia Coal Field in Jharkhand. Water supply is given from the Agra Canal.
Basic Steps of Electricity Generation
Coal to steam
Steam to mechanical power
Mechanical power to electrical power
PARTS OF A POWER PLANT
The various parts are listed below:-
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. Condensate extraction pump
9. Intermediate pressure turbine
10. Steam governor valve
11. High pressure turbine
13. Feed heater
14. Coal conveyor
15. Coal hopper
16. Pulverised fuel mill
17. Boiler drum
18. Ash hopper
19. Super heater
20. Forced draught fan
22. Air intake
24. Air preheater
26. Induced draught fan
27. Flue Gas
1. Cooling Tower
Cooling towers are heat removal devices used to transfer process waste heat to the
atmosphere. Cooling towers may either use the evaporation of water to remove process
heat and cool the working fluid to near the wet-bulb air temperature or in the case of
closed circuit dry cooling towers rely solely on air to cool the working fluid to near the
dry-bulb air temperature. Common applications include cooling the circulating water
used in oil refineries, chemical plants, power stations and building cooling.
The towers vary in size from small roof-top units to very large hyperboloid structures that
can be up to 200 meters tall and 100 meters in diameter, or rectangular structures that can
be over 40 meters tall and 80 meters long. Smaller towers are normally factory-built,
while larger ones are constructed on site. The absorbed heat is rejected to the atmosphere
by the evaporation of some of the cooling water in mechanical forced-draft or induced
Draft towers or in natural draft hyperbolic shaped cooling towers as seen at most nuclear
2. Cooling Water Pump
it pumps the water from the cooling tower which goes to the condenser.
3. Three phase transmission line
Three phase electric power is a common method of electric power transmission. It is a
type of polyphase system mainly used to power motors and many other devices. A three
phase system uses less conductive material to transmit electric power than equivalent
single phase, two phase, or direct current system at the same voltage. In a three phase
system, three circuits reach their instantaneous peak values at different times.
Taking current in one conductor as the reference, the currents in the other two are delayed
in time by one-third and two-third of one cycle .This delay between “phases” has the
effect of giving constant power transfer over each cycle of the current and also makes it
possible to produce a rotating magnetic field in an electric motor. At the power station, an
electric generator converts mechanical power into a set of electric currents, one from each
electromagnetic coil or winding of the generator.
The current are sinusoidal functions of time, all at the same frequency but offset in time
to give different phases. In a three phase system the phases are spaced equally, giving a
phase separation of one-third of one cycle. Generators output at a voltage that ranges
from hundreds of volts to 30,000 volts.
4. Unit transformer (3-phase)
At the power station, transformers step-up this voltage to one more suitable for
transmission. After numerous further conversions in the transmission and distribution
network the power is finally transformed to the standard mains voltage (i.e. the
“household” voltage). The power may already have been split into single phase at this
point or it may still be three phase. Where the step-down is 3 phase, the output of this
transformer is usually star connected with the standard mains voltage being the phase-
neutral voltage. Another system commonly seen in North America is to have a delta
connected secondary with a center tap on one of the windings supplying the ground and
This allows for 240 V three phase as well as three different single phase voltages( 120 V
between two of the phases and neutral , 208 V between the third phase ( or wild leg) and
neutral and 240 V between any two phase) to be available from the same supply.
5. Electrical generator
An Electrical generator is a device that converts kinetic energy to electrical energy,
generally using electromagnetic induction. The task of converting the electrical energy
into mechanical energy is accomplished by using a motor. The source of mechanical
energy maybe water falling through the turbine or steam turning a turbine (as is the case
with thermal power plants). There are several classifications for modern steam turbines.
Steam turbines are used in our entire major coal fired power stations to drive the
generators or alternators, which produce electricity. The turbines themselves are driven
by steam generated in "boilers “or "steam generators" as they are sometimes called.
Electrical power stations use large steam turbines driving electric generators to produce
most (about 86%) of the world‟s electricity. These centralized stations are of two types:
fossil fuel power plants and nuclear power plants. The turbines used for electric power
generation are most often directly coupled to their-generators .As the generators must
rotate at constant synchronous speeds according to the frequency of the electric power
system, the most common speeds are 3000 r/min for 50 Hz systems, and 3600 r/min for
60 Hz systems. Most large nuclear sets rotate at half those speeds, and have a 4-pole
generator rather than the more common 2-pole one.
6. Low Pressure Turbine
Energy in the steam after it leaves the boiler is converted into rotational energy as it
passes through the turbine. The turbine normally consists of several stages with each
stages consisting of a stationary blade (or nozzle) and a rotating blade. Stationary blades
convert the potential energy of the steam into kinetic energy and direct the flow onto the
rotating blades. The rotating blades convert the kinetic energy into impulse and reaction
forces, caused by pressure drop, which results in the rotation of the turbine shaft. The
turbine shaft is connected to a generator, which produces the electrical energy.
Low Pressure Turbine (LPT) consists of 4x2 stages. After passing through Intermediate
Pressure Turbine steam is passed through LPT which is made up of two parts- LPC
REAR & LPC FRONT. As water gets cooler here it gathers into a HOTWELL placed in
lower parts of turbine.
7. Condensation Extraction Pump
A Boiler feed water pump is a specific type of pump used to pump water into a steam
boiler. The water may be freshly supplied or returning condensation of the steam
produced by the boiler. These pumps are normally high pressure units that use suction
from a condensate return system and can be of the centrifugal pump type or positive
Construction and operation:
Feed water pumps range in size up to many horsepower and the electric motor is usually
separated from the pump body by some form of mechanical coupling. Large industrial
condensate pumps may also serve as the feed water pump. In either case, to force the
water into the boiler, the pump must generate sufficient pressure to overcome the steam
pressure developed by the boiler. This is usually accomplished through the use of a
centrifugal pump. Feed water pumps usually run intermittently and are controlled by a
float switch or other similar level-sensing device energizing the pump when it detects a
lowered liquid level in the boiler. Some pumps contain 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, its supply has been cut off or exhausted, or
its discharge is blocked) the second stage will be triggered. This stage may switch off the
boiler equipment (preventing the boiler from running dry and overheating), trigger an
alarm, or both.
The steam coming out from the Low Pressure Turbine (a little above its boiling pump) is
brought into thermal contact with cold water (pumped in from the cooling tower) in the
condenser, where it condenses rapidly back into water, creating near Vacuum-like
conditions inside the condenser chest.
9. Intermediate Pressure Turbine
Intermediate Pressure Turbine (IPT) consists of 11 stages. When the steam has been
passed through HPT it enters into IPT. IPT has two ends named as FRONT & REAR.
Steam enters through front end and leaves from Rear end.
10. Steam Governor Valve
Steam locomotives and the steam engines used on ships and stationary applications such
as power plants also required feed water pumps. In this situation, though, the pump was
often powered using a small steam engine that ran using the steam produced by the boiler
a means had to be provided, of course, to put the initial charge of water into the boiler
(before steam power was available to operate the steam-powered feed water pump).The
pump was often a positive displacement pump that had steam valves and cylinders at one
end and feed water cylinders at the other end; no crankshaft was required. In thermal
plants, the primary purpose of surface condenser is to condense the exhaust steam from a
steam turbine to obtain maximum efficiency and also to convert the turbine exhaust
steam into pure water so that it may be reused in the steam generator or boiler as boiler
feed water. By condensing the exhaust steam of a turbine at a pressure below atmospheric
pressure, the steam pressure drop between the inlet and exhaust of the turbine is
increased, which increases the amount heat available for conversion to mechanical
power. Most of the heat liberated due to condensation of the exhaust steam is carried
away by the cooling medium (water or air) used by the surface condenser. Control valves
are valves used within industrial plants and elsewhere to control operating conditions
such as temperature, pressure, flow and liquid level by fully or partially opening or
closing in response to signals received from controllers that compares a “set point” to a
“process variable” whose value is provided by sensors that monitor changes in such
conditions. The opening or closing of control valves is done by means of electrical,
hydraulic or pneumatic systems.
11.High Pressure Turbine
Steam coming from Boiler directly feeds into HPT at a temperature of 540°C and at a
pressure of 136 kg/cm2. Here it passes through 12 different stages due to which its
temperature goes down to 329°C and pressure as 27 kg/cm2. This line is also called as
CRH – COLD REHEAT LINE. It is now passed to a REHEATER where its temperature
rises to 540°C and called as HRH-HOT REHEATED LINE.
A Deaerator is a device for air removal and used to remove dissolved gases (an alternate
would be the use of water treatment chemicals) from boiler feed water to make it non-
corrosive. A dearator typically includes a vertical domed deaeration section as the
deaeration boiler feed 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 gases will give rise to corrosion of
the metal. The solids will deposit on the heating surfaces giving rise to localized heating
and tube ruptures due to overheating. Under some conditions it may give rise to stress
corrosion cracking. Deaerator level and pressure must be controlled by adjusting control
valves the level by regulating condensate flow and the pressure by regulating steam flow.
If operated properly, most deaerator vendors will guarantee that oxygen in the deaerated
water will not exceed 7 ppb by weight (0.005 cm3/L)
13. Feed water heater
A Feed water heater is a power plant component used to pre-heat water delivered to a
steam generating boiler. Preheating the feed water reduces the irreversibility involved in
steam generation and therefore improves the thermodynamic efficiency of the system.
This reduces plant operating costs and also helps to avoid thermal shock to the boiler
metal when the feed water is introduced back into the steam cycle. In a steam power
(usually modelled as a modified Rankine cycle), feed water heaters allow the feed water
to be brought up to the saturation temperature very gradually. This minimizes the
inevitable irreversibility associated with heat transfer to the working fluid (water).
14. Coal conveyor
Coal conveyors are belts which are used to transfer coal from its storage place to Coal
Hopper. A belt conveyor consists of two pulleys, with a continuous loop of material- the
conveyor Belt – that rotates about them. The pulleys are powered, moving the belt and
the material on the belt forward.
Conveyor belts are extensively used to transport industrial and agricultural material, such
as grain, coal, ores etc.
15. Coal Hopper
Coal Hoppers are the places which are used to feed coal to Fuel Mill. It also has the
arrangement of entering Hot Air at 200°C inside it which solves our two purposes:-
1. If our Coal has moisture content then it dries it so that a proper combustion takes place.
2. It raises the temperature of coal so that its temperature is more near to its Ignite
Temperature so that combustion is easy.
16. Pulverized Fuel Mill
A pulveriser is a device for grinding coal for combustion in a furnace in a fossil fuel
17. Boiler drum
Steam Drums are a regular feature of water tube boilers. It is reservoir of water/steam at
the top end of the water tubes in the water-tube boiler. They store the steam generated in
the water tubes and act as a phase separator for the steam/water mixture. The difference
in densities between hot and cold water helps in the accumulation of the “hotter”-
water/and saturated –steam into steam drum. Made from high-grade steel (probably
stainless) and its working involve temperature of 390°C and pressure well above 350psi
(2.4MPa). The separated steam is drawn out from the top section of the drum.
Saturated steam is drawn off the top of the drum. The steam will re-enter the furnace in
through a super heater, while the saturated water at the bottom of steam drum flows down
to the mud-drum /feed water drum by down comer tubes accessories include a safety
valve, water level indicator and fuse plug.
18. Ash Hopper
A steam drum is used in the company of a mud-drum/feed water drum which is located at
a lower level.
So that it acts as a sump for the sludge or sediments which have a tendency to accumulate
at the bottom.
19. 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. Super heaters increase the efficiency of the steam
engine, and were widely adopted. Steam which has been superheated is logically known
as superheated steam; non- superheated steam is called saturated steam or wet steam.
Super heaters were applied to steam locomotives in quantity from the early 20th century,
to most steam vehicles, and also stationary steam engines including power stations.
20. Force Draught Fan
External fans are provided to give sufficient air for combustion. The forced draught fan
takes air from the atmosphere and, warms it in the air preheater for better combustion,
injects it via the air nozzles on the furnace wall.
Reheater is a heater which is used to raise the temperature of steam which has fallen from
the intermediate pressure turbine.
22. Air Intake
Air is taken from the environment by an air intake tower which is fed to the fuel.
Economizer, or in the UK economizer, are mechanical devices intended to reduce energy
consumption, or to perform another useful function like preheating a fluid. The term
economizer is used for other purposes as well-Boiler, power plant, heating, ventilating
and air-conditioning. In boilers, economizer are heat exchange devices that heat fluids ,
usually water, up to but not normally beyond the boiling point of the fluid. Economizers
are so named because they can make use of the enthalpy and improving the boiler‟s
efficiency. They are devices fitted to a boiler which save energy by using the exhaust
gases from the boiler to preheat the cold water used to fill it (the feed water). Modern day
boilers, such as those in cold fired power stations, are still fitted with economizer which
is decedents of Green‟s original design. In this context there are turbines before it is
pumped to the boilers. A common application of economizer in steam power plants is to
capture the waste heat from boiler stack gases (flue gas) and transfer thus it to the boiler
feed water thus lowering the needed energy input , in turn reducing the firing rates to
accomplish the rated boiler output . Economizer lower stack temperatures which may
cause condensation of acidic combustion gases and serious equipment corrosion damage
if care is not taken in their design and material selection.
24. Air Preheater
Air preheater is a general term to describe any device designed to heat air before another
process (for example, combustion in a boiler). The purpose of the air preheater is to
recover the heat from the boiler flue gas which increases the thermal efficiency of the
boiler by reducing the useful heat lost in the flue gas. As a consequence, the flue gases
are also sent to the flue gas stack (or chimney) at a lower temperature allowing simplified
design of the ducting and the flue gas stack. It also allows control over the temperature of
gases leaving the stack.
An Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate device that
removes particles from a flowing gas (such as air) using the force of an induced
electrostatic charge. Electrostatic precipitators are highly efficient filtration devices, and
can easily remove fine particulate matter such as dust and smoke from the air steam.
ESPs continue to be excellent devices for control of many industrial particulate
emissions, including smoke from electricity-generating utilities (coal and oil fired), salt
cake collection from black liquor boilers in pump mills, and catalyst collection from
fluidized bed catalytic crackers from several hundred thousand ACFM in the largest coal-
fired boiler applications. The original parallel plate-Weighted wire design (described
above) has evolved as more efficient (and robust) discharge electrode designs, today
focus is on rigid discharge electrodes 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 controls minimize sparking
and prevent arcing, avoiding damage to the components. Automatic rapping systems and
hopper evacuation systems remove the collected particulate matter while on line allowing
ESPs to stay in operation for years at a time.
26. Induced Draught Fan
The induced draft fan assists the FD fan by drawing out combustible gases from the
furnace, maintaining a slightly negative pressure in the furnace to avoid backfiring
through any opening. At the furnace outlet and before the furnace gases are handled by
the ID fan, fine dust carried by the outlet gases is removed to avoid atmospheric
pollution. This is an environmental limitation prescribed by law, which additionally
minimizes erosion of the ID fan.
27. Flue gas stack
A Flue gas stack is a type of chimney, a vertical pipe, channel or similar structure through
which combustion product gases called flue gases are exhausted to the outside air. Flue
gases are produced when coal, oil, natural gas, wood or any other large combustion
device. Flue gas is usually composed of carbon dioxide (CO2) and water vapour as well
as nitrogen and excess oxygen remaining from the intake combustion air. It also contains
a small percentage of pollutants such as particulates matter, carbon mono oxide, nitrogen
oxides and sulphur oxides. The flue gas stacks are often quite tall, up to 400 meters (1300
feet) or more, so as to disperse the exhaust pollutants over a greater area and thereby
reduce the concentration of the pollutants to the levels required by government's
environmental policies and regulations. The flue gases are exhausted from stoves, ovens,
fireplaces or other small sources within residential abodes, restaurants, hotels through
other stacks which are referred to as chimneys.
VARIOUS CYCLES AT POWER STATION
PRIMARY AIR CYCLE
SECONDARY AIR CYCLE
FLUE GAS CYCLE
FEED WATER CYCLE
PRIMARY AIR CYCLE
P A FAN
COLD AIR DUCT
SEAL AIR FAN
HOT AIR DUCT
SECONDARY AIR CYCLE
SCANNER AIR FAN
GLAND STEAM COOLER WITH EJECTOR
LP HEATER 2
LP HEATER 3
LP HEATER 4
BOILER FEED PUMP
FEED WATER CYCLE
BOILER FEED PUMP
HP HEATOR 5
HP HEATOR 6
HP HEATOR 7
FEED REGULATING STN
H P TURBINE
I P TURBINE
L P TURBINE
ELECTRICAL MAINTENANCE DEPARTMENT – I (EMD-I)
Electrical maintenance division 1
High Tension/Low Tension Switchgear
Coal handling plant
I was assigned to do training in this division from 11th
In modern thermal power plant three phase squirrel cage induction motors are used but
sometimedouble woundmotor isusedwhenweneedhighstartingtorquee.g.inballmill.
Stator canhandleconcentrated singlelayer winding, witheachcoiloccupyingonestator slot
This type of winding is distributed over a number of slots.
Squirrel cage and wound cage have same mode of operation. Rotor conductors cut the
rotating stator magnetic field. an emf is induced across the rotor winding, current flows,
a rotor magnetic field is produced which interacts with the stator field causing a turning
motion. The rotor does not rotate at synchronous speed, its speed varies with applied
load. The slip speed beingjustenoughtoenablesufficientinducedrotor currenttoproducethepower
dissipatedby the motor load and motor losses.
Agoodbearingisneededfor troublefreeoperationof motor.Sinceitisverycostlypartofthe motor,
due care has to be taken by checking it at regular intervals. So lubricating plays an
important role. Two types of lubricating are widely used
1. Oil lubrication
2. Grease lubrication
CLASS TEMP UPTO WHICH THEY ARE EFFECTIVE
C more than 180
MAIN MOTOR USED INBOILERAND OFFSIDE AREA
1. IDFAN(2PER UNIT)
2. PAFAN(2 PER UNIT)
It is used for handling atmospheric air up to temperature 50 degree centigrade
3. FDFAN(2 PER UNIT)
Itisusedfor handlingsecondaryair for theboiler.
4. SCANNER FAN(2 PER UNIT)
Itisrequiredforrequisiteair for scanner cooling.
Itsuppliesair for coolingofigniters.
Thisinstrumentisusedfor measuringinsideaswellasoutsidediameter ofbearing.
Switchgear isonethatmakesor breakstheelectricalcircuit.Itisa switchingdevicethatopens& closes a
circuit that defined as apparatus used for switching, Lon rolling & protecting the electrical
currentseither under normalorabnormaloperatingconditions.Thetubular switch with ordinary
fuse is simplest form of switchgear & is used to control & protect&other equipmentsin
homes,officesetc.For circuitsofhigherratings,aHighRupturingCapacity (H.R.C) fuse in
condition with a switch may serve the purpose of controlling &protectingthecircuit.However
suchswitchgearcannotbeusedprofitablyonhighvoltagesystem(3.3 KV) for2reasons.Firstly,whena
fuseblows,ittakessometimetoreplaceit&consequently there is interruption of service to
customer. Secondly, the fuse cannot successfully interrupt large currents that result from
the High Voltage System. In order to interrupt heavy fault currents, automatic circuit
breakers are used. There are very fewtypesofcircuitbreakersinB.P.T.StheyareVCB,OCB,and
SF6gascircuitbreaker.Themostexpensive circuit breaker is the SF6 type due to gas. There
are various companies which manufacturethesecircuitbreakers: VOLTAS,JYOTI,and
These are used in various circuits for isolating the certain portion when required for
solenoidoperatedpneumaticthreephasemotoror DC motor transmittingthrough a spur gear to
the torsion shaft of the isolator. Certain interlocks are also provided with theisolator
1. Isolator cannotoperateunlessbreaker isopen
2. Bus 1 and bus 2 isolators cannot be closed simultaneously
3. Theinterlockcanbebypassintheeventofclosingofbuscoupler breaker.
4. Noisolator canoperatewhenthecorrespondingearthswitchison
Switching isolator is capable of:
2. Interrupting transformer magnetizing current
3. Load transformer switching. Its main application is in connection with the
transformer feeder as the unit makes it possible to switchgearonetransformer
One whichcanmakeor breakthecircuitonloadandevenonfaultsisreferredtoascircuit
protection of various circuits and operations on load. Normallycircuitbreakers
4. LOADBREAK SWITCHES
Thesearethoseinterruptingdeviceswhichcanmakeor break circuits.Thesearenormallyon same
5. EARTH SWITCHES
Devices which are used normally to earth a particular system, to avoid any accident
anyappreciable current at all. Apart from this equipment there are a number of relays
etc. which areusedinswitchgear.
In LT switchgear there is no interlocking. It is classified in following ways:-
Main switch is control equipment which controls or disconnects the main supply. The
main switch for 3 phase supply is available for the range 32A, 63A, 100A, 200Q,
300A at 500V grade.
With Avery high generating capacity of the modern power stations extremely heavy
carnets would flow in the fault and the fuse clearing the fault would be required to
withstand extremely heavy stress in process. It is used for supplying power to
auxiliaries with backup fuse protection. With fuses, quick break, quick make and
double break switch fuses for 63A and 100A, switch fuses for 200A,400A, 600A,
800A and 1000A are used.
AC Contractors are 3 poles suitable for D.O.L Starting of motors and protecting the
4. OVERLOAD RELAY
For overload protection, thermal overload relay are best suited for this purpose. They
operate due to the action of heat generated by passage of current through relay element.
5. AIRCIRCUIT BREAKERS
It is seen that use of oil in circuit breaker may cause a fire. So in all circuits breakers
at large capacity air at high pressure is used which is maximum at the time of quick
tripping of contacts. This reduces the possibility of sparking. The pressure may vary from
50-60kg/cm^2 for high and medium capacity circuit breakers.
These use oil as quenching medium. It comprises of simple dead tank row pursuing
projection from it. The moving contracts are carried on an iron arm lifted by a long
insulating tension rod and are closed simultaneously pneumatic operating mechanism by
means of tensions but throw off spring to be provided at mouth of the control the main
current within the controlled device.
Rated Voltage-66 KV
Breaking Capacity-3.4+KA Symmetrical
360 MVA Symmetrical
Motor Voltage-220 V/DC
2. AIRCIRCUIT BREAKER
In this the compressed air pressure around 15 kg per cm^2 is used for extinction of arc
caused by flow of air around the moving circuit . The breaker is closed by applying
pressure at lower opening and opened by applying pressure at upper opening. When
contacts operate, the cold air rushes around the movable contacts and blown the arc:
It has the following advantages over OCB:-
i. Fire hazard due to oil are eliminated.
ii. Operation takes place quickly.
iii. There is less burning of contacts since the duration is short and consistent.
iv. Facility for frequent operation since the cooling medium is replaced
Rated Voltage-6.6 KV
Auxiliary current-220 V/DC
This type of circuit breaker is of construction to dead tank bulk oil to circuit breaker but
the principle of current interruption is similar to that of air blast circuit breaker. It simply
employs the arc extinguishing medium namely SF6. When it is broken down under an
electrical stress, it will quickly reconstitute itself.
Standard-1 EC 56
Rated Voltage-12 KV
Insulation Level-28/75 KV
Rated Frequency-50 Hz
Breaking Current-40 KA
Rated Current-1600 A
Making Capacity-110 KA
It works on the principle that vacuum is used to save the purpose of insulation and. In
regards of insulation and strength, vacuum is superior dielectric medium and is better
that all other medium except air and sulphur which are generally used at high pressure.
Rated frequency-50 Hz·
Rated making Current-10 Peak KA
Rated Voltage-12 KV
Supply Voltage Closing-220 V/DC
The coal handling plant consists of two plants:
Old Coal Handling Plant (OCHP)
New Coal Handling Plant (NCHP)
The OCHP supplies coal to Unit- I, II, III &
NCHP supplies coal to Unit- IV and V.
Coal is supplied to BTPS by Jharia coal mines. It is non-cooking coal and has following
Moisture- less than 8%
Ash- 35% - 40%
Calorific Value- 4500 to5300 Kcal/kg
Coal is received in railway box racks containing 20 - 42 wagons in each rack.
Capacity of each box wagon is about 55 ton.
These wagons are placed on 2 wagon tippler in OCHP & one wagon tippler in
NCHP, in total 3, capacity 80 toneach.
The main constituents of OCHP plant are:-
Wagon from coal yard come to the tippler and emptied here. There are 2 wagon tipplers
in the OCHP. The tippler is tilted to about 137°- 141° so that coal from the wagon is
emptied into the hopper. Elliptics feeder is used in OCHP. Total 8 feeders are used, 4 in
Slip Ring Induction Motor is used to operate a wagon tippler. This type of IM is used in
the tippler because of its high resistance, low speed & high torque characteristics. The
rating of the motor used is:
o Power 55 Kw
o Voltage 415V
o Current 102A
o Speed 1480rpm
o Phase 3
o Frequency 50Hz
Three types of wagon tipplers are used:-
a) ROTASIDE: - It is used for open type wagons in which each wagon carries around 50-
56 tons of coal. The wagon is tilted by 150° to put the coal in the unloading hopper.
b) ROTARY: - In this case the unloading hopper is placed directly under the tippler table.
This is also used to tilt the wagon tippler to 180°.
c) ROCKING TYPE: - It is used for close type wagons. In this hoppers is placed by the
side of end rocking is provided to facilitate unloading of coal at corners of the wagon.
Conveyer belts are used in the OCHP to transfer coal from one place to other as required
in a convenient&safe way.Allthebeltsarenumberedaccordingly sothattheir functioncanbeeasily
demarcated. These belts are made of rubber & move with a speed of 250-300 m/min.
Motor employedfortheconveyer hasa capacityof150HP.Theseconveyershavea capacityof
carrying the coal at the rate of 400 ton/hr.
It is used as a safety device for the motor i.e. if the belt is not moving & the motor is ON,
then itburnstosavethemotor.Thisswitchchecksthespeedofthebelt&switchesoffthemotor when
As the conveyer belt take coal from wagon to crusher house, no metal piece should go
along with coal. To achieve this objective, metal detectors & separators are used. In the
OCHP, these MD‟s are installed in the conveyer belts 2A & 2B.
Both the plants i.e. OCHP & NCHP use TATA crusher powered by BHEL motor.
Crusher is of ring typeandthemotorisaHT motor ofrating400HP&6.6 KV.Crusherisdesignedto
crushthepieces to 20 mm size i.e. practically considered as the optimum size for transfer
It is used for stacking & reclaiming the coal from the stockyard in case of unavailability
of wagons from coal mines.
Theseplough feedersaregenerallyinstalledunder slotbunkersor hoppers.Theseareusedtop lough the
coal to the belt from the coal fed from stockyard. These feeders used in this power station
are generally of rotary type.
Trippersareprovidedintheconveyer tocollectthematerialatdesiredlocationoneither sideoralongthe
conveyer withthehelpofchute/ductsfittedwithtripper itself.Themotor inthetrippercanmakeit move
Thesearetheswitcheswhichareinstalledatevery10mgapina conveyer belttoensurethesafety of
motors running the conveyer belts. If at any time some accident happens or coal jumps
from belt and starts collecting at a place, this switch can be moved to NO(normally open)
position from NC (normally closed) position to stop conveyor belt from moving. At this
position for normal working again.
The CHP is normally spread over a wide area with centralized control room. Elaborate
scheme is thereforeprovided.Ifduetoanyemergencyeither theconveyor beltorthemotor hastobe
stopped, due to this interlocking all the other motors connected to it will automatically
stop &will not work till signal is given from the control room.
The control & protection scheme normally includes: -
A hooter system to warn that the plant is going to be started. The plant can be
started only after a definite time after the hooter is energized.
Sequential starting of conveyor system and tripping of all proceeding system if
Tripping of conveyor from speed switch for protection against belt slippage.
II. Crushing & storage.
III. Conveyingtoboiler bunkers.
a) Coal arrives to plant via road, rail, sea, and river or canal route from collieries.
Most of it arrivesbyrailrouteonlyinrailwaywagons.Coalrequirementbythisplantis
approximately 10,500 metric ton/day.
b) This coal is tippled into hoppers. If the coal is oversized (400 mm sq), then it is
broken manuallysothatitpassesthehopper meshwherethroughelliptic feeder itisputinto
vibrators&thentoconveyor belt1A &1B.
c) The coal through conveyor belts 1A & 1B goes to the crusher house. Also the
extra coal is sent to stockyard through these belts.
d) Inthecrusher housethe smallsizecoalpiecesgoesdirectlytothebelt2A &2B whereasthe
e) Thecrushedcoalistakentothebunker housevia theconveyor belts3A&3B whereitcanbe
usedfor further operations.
The main constituents of NCHP plant are:-
Most of the constituents of the NCHP are the same as that of OCHP.
InNCHPthereisonlyone wagontippler.Inthisittakes52sectoraisea wagon,10secto emptythe
wagoncompletely&thenagain52sectobringthetippler down.AsemicircularhugeWTgear is used
to run the tippler. Protocol cameras have been installed for safety to ensure that nomoving
Vibro feedersareinstalledbelowthehopper whichhelpsinputtingthecoaltotheconveyor belts. There
are 2 conveyor belts & 3 vibro feeder per plant, so in total there are 6 vibrofeeders.
Given below are the feeder motor specifications:
CONVEYOR TURNINGPOINT-6BREAKER HOUSE
This house is required to render the coal size to 100mm sq. A 415W LT motor is used
in the breaker house.
Thecoalcomestobreakerhousevia conveyor belts12A&12B.Nowinthebreakerhousethehuge
stones & metal impurities are separated & sent to reject bin house through belts 18A
It is the stockyard in which coal is stored for emergency purposes. Around 3 lakh ton of
coal can bestoredinit
To ensure that the coal is of uniform size it is passed through crusher. The crusher is of ring
type. Has a motor rating of 400HP,606KV.It is designed to crush the pieces to 20mm size
a) Coal arrives in wagons and tipples into hoppers.
b) if the coal is oversized (400mm sq), then it is broken manually so that it passes through
the hopper mesh.
c) From hopper it is taken to TP-6 12A & 12B.
d) Conveyors12A&12Btakethecoaltothebreakerhousewhichrendersthecoalsizetobe 100 mm
e) Metalseparator &metaldetectorareinstalledinconveyor belts14A/B &15A/Brespectivelyto
.f) Stones which are not able to pass through the 100mm sq mesh of hammer are rejected
via 18A & 18B to the rejection house.
g) Extra coal is sent to the reclaim hopper via conveyor 16A & 16B.
h)From TP-7, coal is taken by conveyor 14A & 14B to the crusher house whose function
is to render size of the coal to 20mm sq.
I. Crusher: - BHEL ILAT/12B HD/02, 736rpm, 550Kw, 6600V.
II. WagonTippler:-5D315l,98Kw slipringmotor.
III. Conveyors: -
1)11A/B, 12A/B: - 125Kw, 315m, 1485rpm.
2)13A/B: - 55Kw, 250m, 1480rpm.
3)14A/B, 15A/B: - 150Kw, 355m, 1485rpm.
4)16A/B, 17A/B: - 110Kw, 315m, 1485rpm.
5)18A/B: - 37Kw, 225m, 1470rpm.
IV. Rotary Breaker: - 110Kw, 315m, 1485rpm
V. Belt Feeder: - 15Kw, 180L, 1445rpm
VI. Reversible Belt Feeder: - 18.7Kw, 200L, 1485rp
VII. VF 1-6: - 7.5Kw, 160m, 1485rpm
VIII. VF 7-8: - 15Kw, 180L, 1485rpm
IX. VF 9-12: - 11Kw,160L, 1485rpm
X. WSP Crusher House: - 15Kw, 160m, 4000rpm
XI. WSP Breaker House: - 7.5Kw, 132m, 1865rpm
XII. Metal Separator: - 5KV, 132m, 1410rpm
XIII. Spray Precipitator: - 18.5Kw, 200L, 3000rpm
Sometimes the belt is wet due to any reason, so it may not run due to reduced friction. A
switch senses this and prevents the belt from choking.
Sometime any accident may occur which requires the belt to stop, the pull cords are
pulled to stop the conveyor. This system starts again only when the pull cords are rest.
There is a push button in the control room from where the belt can be stopped in case
of emergency stoppage. Other equipments are pulley. Pulleys are made of mild steel,
rubber logging is provided to increase the friction factor between the pulley and belt.
Raw coal is fed directly to these bunkers. These are 3 in no. per boiler. 4 & ½ tons of coal
are fed in 1 hr. the depth of bunkers is 10m.
It transports pre-crust coal from raw coal bunker to mill. The quantity of raw coal
fed in mill can be controlled by speed control of aviator drive controlling damper
and aviator change
The ball mill crushes the raw coal to a certain height and then allows it to fall
down. Due to impact of ball on coal and attraction as per the particles move over
each other as well as over the Armor lines, the coal gets crushed. Large particles
are broken by impact and full grinding is done by attraction. The Drying and
grinding option takes place simultaneously inside the mill. In ball mill coal is
converted to powdered form and due to pneumatic action the powdered form of
coal is transferred upwards.
It is equipment which serves separation of fine pulverized coal particles medium from
coarse medium. The pulverized coal along with the carrying medium strikes the
impact plate through the lower part. Large particles are then transferred to the ball mill.
From ball mill the powdered coal is sucked through mill fan.
It separates the pulverized coal from carrying medium. The mixture of pulverized coal
vapour caters the cyclone separators tangentially in the upper part of the separator. Due
to decrease in the velocity the centrifugal action, the pulverized coal separated from the
vapour &fallsdowntothelower epicalpart.
It serves to transport pulverized coal from cyclone separators to pulverized coal bunker or
to worm conveyors. There are 4 turnigates per boiler.
It is equipment used to distribute the pulverized coal from bunker of one system to
bunker of other system. It can be operated in both directions
ELECTRICAL MAINTENANCE DEPARTMENT –II (EMD-II)
Electrical maintenance division 2
I was assigned to do training in this division from 2nd
The generator works on the principle of electromagnetic induction. There are two
components stator and rotor. The rotor is the moving part and the stator is the stationary
part. The rotor, which has a field winding, is given a excitation through a set of 3000rpm
to give therequiredfrequencyofHZ.TherotoriscooledbyHydrogengas,whichislocally
manufactured by the plant and has high heat carrying capacity of low density. If oxygen
and hydrogengetmixedthentheywillformveryhighexplosiveandtopreventtheir combininginany
waythereissealoilsystem.Thestator coolingisdonebyde-mineralized(DM) waterthroughhollow
conductors.WaterisfedbyoneendbyTeflontube.Aboilerandaturbineare coupled to electric
generators. Steam from the boiler is fed to the turbine through the connecting pipe. Steam
drives the turbine rotor. The turbine rotor drives the generator rotor which turns the
electromagnet within the coil of wire conductors.
Carbon dioxide is provided from the top and oil is provided from bottom to the generator.
Hydrogen gas is used to cool down the rotor.
Lube oil is used to cool the bearings.
DM water is used to cool the stator.
Seal oil is used to prevent hydrogen leakage
Seal oil coolers are present to cool the seal oil
Hydrogen dryer are used which removes the moisture from hydrogen gas and then
is supplied to the generator.
Clarified water in cooling tower is used to cool down the hydrogen gas.
Turbo generator 100MW
The 100 MW generator generates 10.75 KV and 210 MW generates 15.75 KV. The
voltage is steppedupto220KVwiththehelpofgenerator transformerandisconnectedtothegrid.
Thevoltageissteppeddownto6.6 KVwiththehelpofUNIT AUXILLARY TRANSFORMER
(UAT)and this voltage is used to drive the HT motors. The voltage is further stepped
down to 415 V and then to 220 V and this voltage is used to drive Lt Motors.
MAKE BHEL, Haridwar
CAPACITY 117,500 KVA
POWER 100,000 KW
STATOR VOLTAGE 10,500 V
STATOR CURRENT 6475 A
POWER FACTOR 0.85
FREQUENCY 50 HZ
EXCITATION 280 V
MAKE BHEL, Haridwar
CAPACITY 247,000 KVA
POWER 210,000 KW
STATOR VOLTAGE 15,750 V
STATOR CURRENT 9050 A
SPEED 5000 rpm
POWER FACTOR 0.85
FREQUENCY 50 HZ
EXCITATION 310 V
GAS PRESSURE 3.5 kg/cm
It is a static machine which increases or decreases the AC voltage without changing the
frequency of the supply.
It is a device that:
Transfer electric power from one circuit to another.
It accomplishes this by electromagnetic induction.
In this the two electric circuits are in mutual inductive influence of each other.
It works on FARADAY‟S LAW OF ELECTROMAGNETIC INDUCTION (self
or mutual induction depending on the type of transformer).
It is used generally to conserve the insulating property of the oil from deterioration&
protect the transformer against failure on account of bad quality of oil.
It is used to prevent entry of moisture inside the transformer tank. The breather
consists of silica gel.
It is a gas actuated relay used for protecting oil immersed transformer against all
types of faults. It indicates presence of gases in case of some minor fault & take
out the transformer out of circuit in case of serious fault.
It is made from highly insulating material to insulate & to bring out the terminals
of the transformer from the container. The bushings are of 3 types:
a. Porcelain bushings used for low voltage transformer
b. Oil filled bushings used for voltage up to 33KV.
c. Condensed type bushings used for voltage above 33KV.
Every transformer with an oil guage to indicate the oil level. The oil guage may be
provided with the alarm contacts which gave an alarm the oil level has dropped
beyond permissible height due to oil leak etc.
The transformer are usually provided with few tappings on secondary side so
that output voltage can be varied for constant input voltage.
It increases the surface area of the tank & more heat is thus radiated in less time.
Device which indicates the temperature of winding of transformer & possible damage
to the transformer due too overload can be prevented.
3 phase transformer is constructed in the core type construction
For reducing losses a smaller thickness of lamination is used.
For the above reason it is also called cold-rolled steel instead hot-rolled steel is
High flux densities (1.4 to 1.7 Wb/sq m) are used in the core of power transformer
which carry load throughout.
For high voltage winding, disc type coils are used.
a) Core type transformer
b) shell type transformer
c) Berry type transformer
a) 1phase transformer
b) 3phase transformer
a) Distribution transformer
b) Transmission transformer
c) Generator transformer
d) Station transformer
e) Unit Auxiliary transformer (UAT)
COOLING OFTRANSFORMERSOF LARGEMVA:
As size of transformer becomes large, the rate of the oil circulating becomes insufficient
to dissipate all the heat produced & artificial means of increasing the circulation by
electric pumps. In very large transformers, special coolers with water circulation may
have to be employed.
1. Air Natural (AN)
2. Air Forced (AF)
Oil immersed cooling
1. Oil Natural Air Natural (ONAN)
2. Oil Natural Air Forced (ONAF)
3. Oil Forced Air Natural (OFAN)
4. Oil Forced Air Forced (OFAF)
Oil immersed Water cooling
1. Oil Natural Water Forced (ONWF)
2. Oil Forced Water Forced (OFWF)
i. Secondary Winding
ii. Primary Winding.
iii. Oil Level
vi. Drain Cock
vii. Cooling Tubes.
viii. Transformer Oil.
ix. Earth Point
x. Explosion Vent
xi. Temperature Gauge.
xii. Buchholz Relay
xiii. Secondary Terminal
xiv. Primary Terminal
TYPE OF COOLING OFB
TEMP OF OIL 45^C
TEMP WINDING 60^C
KV (no load) HV-233 KVA
LINE AMPERES HV-310 A
FREQUENCY 50 HZ
IMPEDANCE VOLTAGE 15%
VECTOR GROUP Y DELTA
INSULATION LEVEL HV-900 KV
CORE AND WINDING WEIGHT 110500 Kg
WEIGHT OF OIL 37200 Kg
TOTAL WEIGHT 188500 Kg
OIL QUANTITY 43900 lit
GENERATORTRANSFORMER (166MVA UNIT-IV)
TYPE OF COOLING ON/OB/OFB
TEMP OF OIL
VOLTS AT NO LOAD HV-236000
LINE AMPERES HV-587 A
FREQUENCY 50 HZ
IMPEDANCE VOLTAGE 15.55%
VECTOR GROUP Y DELTA
CORE AND WINDING WEIGHT 138800 Kg
WEIGHT OF OIL 37850 Kg
TOTAL WEIGHT 234000 Kg
OIL QUANTITY 42500 lit
GUARANTEED MAX TEMP
UNIT AUXILIARY TRANSFORMER(UAT)
Unit I & V- 12.5 MVA
The UAT draws its input from the main bus-ducts. The total KVA capacity of UAT
required can be determined by assuming 0.85 power factor & 90% efficiency for total
auxiliary motor load. It is safe & desirable to provide about 20% excess capacity then
circulated to provide for miscellaneous auxiliaries & possible increase in auxiliary.
It is required to feed power to the auxiliaries during startups. This transformer is normally
rated for initial auxiliary load requirements of the unit in typical cases; this load is of the
order of 60% of the load at full generating capacity. It is provided with on load tap
change to cater to the fluctuating voltage of the grid.
This transformer is connected with supply coming out of UAT in stage-2. This is used to
As we know that electrical energy can‟t be stored like cells, so what we generate should
toneedi.e.thegenerationdependsuponload.Theyardistheplacesfromwheretheelectricity is send
outside. It has both outdoor and indoor equipments.
Bus bars generally are of high conductive aluminum conforming to IS-5082 or
copper of adequatecrosssection.Busbarlocatedinair insulatedenclosures&segregated
fromallother components.Busbar ispreferablycover withpolyurethane.
Thisbusisabackupbuswhichcomeshandy whenanyofthebusesbecome faulty.Whenany
It saves the transformer and reactor from over voltage and over currents. It
grounds the overload ifthereisfaultonthelineanditpreventsthegenerator transformer.The
lightningarrester bothinprimaryandsecondaryoftransformerandinreactors.A meter is
Power line carrier communication (PLCC) is mainly used for telecommunication,
tele-protection and tele-monitoring between electrical substations through power
lines at high voltages, such as 110 kV, 220 kV, and 400 kV. PLCC integrates the
transmission of communication signal and 50/60 Hz power signal through the
same electric power cable. The major benefit is the union of two important
applications in a single system. WAVETRAP is connected in series with
the power (transmission) line. It blocks the high frequency carrier waves (24 KHz
to 500 KHz) and let power waves (50 Hz - 60 Hz) to pass-through.
breaker instationservesthesamepurposeasswitchbutithas manyaddedandcomplex
features. The basic construction of any circuit breaker requires the separation of
contact in an insulating fluid that servers two functions:
i. extinguishesthearcdrawnbetweenthecontactswhencircuitbreaker opens.
A capacitor voltage transformer (CVT) is a transformer used in power systems to
step-down extra high voltage signals andprovidelow voltage signals either for
measurement or to operatea protectiverelay.Itislocatedinthelastintheswitchyardasit
increasestheground resistance. Finally the voltage from CVT in the switchyard is
sent out from the station through transmissionlines.
provided to earth the lightening arrestor whereas the other equipments are earthed
by connectingtheir earthleadstotherid/ser ofthegroundmar.
It is essentially a step up transformer which step down the current to a known
ratio. It is a type of instrument transformer designed to provide a current in
its secondary winding proportional to the alternating current flowing in its
Relay is a sensing device that makes your circuit ON or OFF. They detect the
detectedthefaulttherelayoperatestocompletethetripcircuit, whichresultsintheopening of
the circuit breakers and disconnect the faulty circuit.
maintenance purpose. This help to neutralize the system from induced voltage
from extra high voltage. This induced power is up to 2KV in case of 400 KV
An electrostatic precipitator ( ESP) or electrostatic air cleaner
is a particulate collection device that removes particles from a flowing gas (such
as air) using the force of an induced electrostatic charge. Electrostatic
precipitators are highly efficient filtration devices that minimally impede the flow
of gases through the device, and can easily remove fine particulate matter such as
dust and smoke from the air stream.
In contrast to wet scrubbers which apply energy directly to the flowing fluid
medium, an ESP applies energy only to the particulate matter being collected and
therefore is very efficient in its consumption of energy (in the form of
electricity).The most basic precipitator contains a row of thin vertical wires, and
followed by a stack of large flat metal plates oriented vertically, with the plates
typically spaced about 1 cm to18 cm apart, depending on the application. The air
or gas stream flows horizontally through the spaces between the wires, and then
passes through the stack of plates. A negative voltage of several thousand volts is
applied between wire and plate. If the applied voltage is high enough an electric
(corona) discharge ionizes the gas around the electrodes. Negative ions flow to
the plates and charge the gas-flow particles.
The ionized particles, following the negative electric field created by the power
supply, move to the grounded plates. Particles build up on the collection plates
and form a layer. The layer does not collapse, thanks to electrostatic pressure
(given from layer resistivity, electric field, and current flowing in the collected
CONTROL & INSTRUMENTATION
This division basically calibrates various instruments and takes care of any faults occur in
any of the auxiliaries in the plant.
“Instrumentation can be well defined as a technology of using instruments to
measure and control the physical and chemical properties of a material.”
Control and Instrumentation Department has following labs:
Protection and Interlocks Lab.
Water Treatment Plant.
Furnaces Safety Supervisory System Lab
OPERATION AND MAINTAINANCE
Control and Instrumentation Department has following Control Units:
1. Unit Control Board2.
2. Main Control Board3.
3. Analog & Digital Signal Control4.
4. Current Signal Control
A View of Control Room at BTPS
1. MANOMETRY LAB
It 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.
It‟s 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
It‟s 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 2 types :
(a) Spiral type: for Low pressure measurement.
(b) Helical Type: for High pressure measurement. While selecting Pressure Gauge these
parameters should keep in mind-
Higher Accuracy implies Larger Dial Size for accuracy of small and readable pressure
While selecting Pressure Gauge it should consider that Gauge Construction Material
should be chemically compatible with the environment either inside or outside it.
It should keep it mind that range of the Gauge should be according to our need else
Overpressure Failure may occur resulting in damage of Gauge.
Lager the Gauge‟s Dial size larger would be our price. Better Gauge‟s Construction
material also increases the cost. So they must be chosen according to our need.
2. PROTECTION AND INTERLOCKING
It is basically interconnecting two or more equipments so that if one equipment 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 provided for all the equipments.
Tripping can be considered as the series of instructions connected through OR GATE,
which trips the circuit. The main equipments of this lab are relay and circuit breakers.
Some of the instrument uses for protection are:
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
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 trips.
I. MANUAL TRIP
II. THERMAL TRIP
III. SHORT CIRCUIT TRIP
Protection and Interlock System-
1) HIGH TENSION CONTROL CIRCUIT for high tension system the control
system is 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, 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° C which limits the range of temperature
that can be measured. It is L shaped thermometer which is designed to reach all
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.
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 measuring devices 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°C and its heights 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
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 no circumstances should anyone 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
They are used to keep any parameter like temperature etc. within limits. It gets a signal
if parameter goes beyond limit. It has a switching transistor connected to relay that helps
in alerting the UCB.
CONTROL & MONITORING MECHANISMS
There are basically two types of Problems faced in a Power Plant
Mechanical Problem can be related to Turbines that is the max speed permissible for a
turbine is3000 rpm so speed should be monitored and maintained at that level.
Metallurgical Problem can be view as the max Inlet Temperature for Turbine is 1060°
C so temperature should be below the limit. Monitoring of all the parameters is necessary
for the safety of both:
So the Parameters to be monitored are:
7. Flow of Gases
8. Vacuum Pressure
Pressure can be monitored by three types of basic mechanisms
3. Transmitter type
For gauges we use Bourdon tubes. The Bourdon Tube is a non-liquid pressure
measurement device. It is widely used in applications where inexpensive static pressure
measurements are needed. 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 shows schematically below.
Typical Bourdon Tube Pressure Gages
For Switches pressure switches are used and they can be used for digital means of
monitoring as switch 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 –20milli-Amperes
We use 4mA as the lower value so as to check for disturbances and wire breaks.
Accuracy of such systems is very high.
Programmable Logic Circuits (PLCs) are used in the process as they are the heart
We can use Thermocouples or RTDs for temperature monitoring. Normally RTDs are
used for low temperatures.
Thermocouple selection depends upon two factors:
2. Accuracy Required
Normally used Thermocouple is KTypeThermocouple:
In this we use Chromel (Nickel-Chromium Alloy) / Alumel (Nickel-Aluminium Alloy) as
two metals. 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 μV/°C.
RTDs are also used but not in protection systems due to vibrational errors.
We pass a constant current through the RTD. So that if R changes then the Voltage also
RTDs used in Industries are Pt100 And Pt1000
Pt100: 0°C – 100 Ω ( 1 Ω = 2.5 0C )
Pt1000: 0°C - 1000Ω
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 does not signify much and is measured just for metering purposes and
for monitoring the processes
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 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 :
1. Flow meters
2. Venturimeters / Orifice meters
4. Massflowmeters(oil level)
6. Magnetic Flow meter (water level )
Selection of flow meter depends upon the purpose, accuracy and liquid to be measured so
different types of meters used.
They are 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.
Referring to the diagram, using Bernoulli's equation in the special case of incompressible
fluids (such as the approximation of a water jet), and the theoretical pressure drop at the
constriction would be given by (ρ/2)(v2
And we know that rate of flow is given by:
Where DP is Differential Pressure or the Pressure Drop.
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
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, or hydraulic 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
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 facilities
required 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.
That‟s why it‟s 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 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. There is a 5 minute delay cycle before igniting, this is to evacuate or burn
the HSD. This method is known as PURGING.
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
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