2. About the company
2.1. NTPC group
2.2. Evolution of NTPC
2.3. Electricity from Coal
3. Definition of Automation
4. Benefits of Automation
5. Control Mechanisms
6. Control & Instrumentation
6.1. Manometry Lab
6.2. Protection & Interlock Lab
6.3. Automation Lab
6.4. Pyrometry Lab
6.5.Furnace Safety & Supervisory Lab
7. Ecological Monitoring Programme
8. Ash Utilization
9. Environment Management & safety System
List of Figures
Fig. 1 Installed Capacity & its Growth
Fig. 2 Fortin Barometer
Fig. 3 Typical Arrangement of Bourdon Gauge
Fig. 4 Dewrance Critical Pressure Gauge
Fig. 5 Air Purge Level Measurement
Fig. 6 Rod Type Thermostat
Fig. 7 Helical Bi-Metal Strip
Fig. 8 Liquid Expansion Thermometer with “C” Bourden
Fig. 9 Bulb Forms
ABOUT THE COMPANY
“A world class integrated power major, powering India’s growth, with increasing
O-Organizational & Professional pride
M-Mutual Respect and Trust
I- Innovation & Speed
T-Total quality for Excellence
NTPC Limited is the largest thermal power generating company of India. A public
sector company, it was incorporated in the year 1975 to accelerate power
development in the country as a wholly owned company of the Government of India.
At present, Government of India holds 89.5% of the total equity shares of the
company and the balance 10.5% is held by FIIs, Domestic Banks, Public and others.
Within a span of 31 years, NTPC has emerged as a truly national power company,
with power generating facilities in all the major regions of the country.
EVOLUTION OF NTPC
NTPC was set up in 1975 with 100% ownership by the
1975 Government of India. In the last 30 years, NTPC has
grown into the largest power utility in India.
In 1997, Government of India granted NTPC status of
1997 “Navratna’ being one of the nine jewels of India, enhancing
the powers to the Board of Directors.
NTPC became a listed company with majority Government
ownership of 89.5%.
NTPC becomes third largest by Market Capitalisation of
The company rechristened as NTPC Limited in line with its
2005 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 India’s
NTPC Vidyut Vyapar NTPC Electric Supply Pipavav Power NTPC Hydro
Nigam Limited Co. Limited Development Co. Ltd Limited
100% 100% 100% 100%
NTPC-SAIL Power Bhilai Electric Supply NTPC Alstom Power Utility Powertech
Company Pvt. Limited Co. Pvt. Limited Services Pvt. Limited Limited
50% 50% 50% 50%
Company Pvt. Limited
NTPC Tamilnadu PTC India Limited Ratnagiri Gas &
Energy Co. Limited 8% Power Private Ltd
GENERATION OF ELECTRICITY FROM COAL
Coal from the coal wagons is unloaded with the help of wagon tipplers in the C.H.P.
this coal is taken to the raw coal bunkers with the help of conveyor belts. Coal is
then transported to bowl mills by coal feeders where it is pulverized and ground in
the powered form. This crushed coal is taken away to the furnace through coal pipes
with the help of hot and cold mixture P.A fan. This fan takes atmospheric air, a part
of which is sent to pre heaters while a part goes to the mill for temperature control.
Atmospheric air from F.D fan in the air heaters and sent to the furnace as
combustion air. Water from boiler feed pump passes through economizer and
reaches the boiler drum . Water from the drum passes through the down comers
and goes to the bottom ring header. Water from the bottom ring header is divided
to all the four sides of the furnace. Due to heat density difference the water rises up
in the water wall tubes. This steam and water mixture is again taken to the boiler
drum where the steam is sent to super heaters for super heating. The super heaters
are located inside the furnace and the steam is super heated (540 degree Celsius)
and finally it goes to the turbine. Fuel gases from the furnace are extracted from the
induced draft fan, which maintains balance draft in the furnace with F.D fan. These
fuel gases heat energy to the various super heaters and finally through air pre
heaters and goes to electrostatic precipitators where the ash particles are extracted.
This ash is mixed with the water to from slurry is pumped to ash period. The steam
from boiler is conveyed to turbine through the steam pipes and through stop valve
and control valve that automatically regulate the supply of steam to the turbine.
Stop valves and controls valves are located in steam chest and governor driven from
main turbine shaft operates the control valves the amount used. Steam from
controlled valves enter high pressure cylinder of turbines, where it passes through
the ring of blades fixed to the cylinder wall. These act as nozzles and direct the steam
into a second ring of moving blades mounted on the disc secured in the turbine
shaft. The second ring turns the shaft as a result of force of steam. The stationary
and moving blades together.
AUTOMATION : THE DEFINITION
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 features
summarized as follows:
1. Optimisation of house load consumption during plant start- up,
shut-down and operation, via:
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
Co-ordination of house load to the generated power output.
2. Ensure and maintain plant operation, even in case of
disturbances in the control system, 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.
3. Reduce plant / process shutdown time for repair and
maintenance as well as repair 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
CONTROL AND MONITORING MECHANISMS
There are basically two types of Problems faced in a Power Plant
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
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 :
Flow of Gases
CONTROL AND INSTRUMENTATION
This division basically calibrates various instruments and takes care of any faults
occur in any of the auxiliaries in the plant. It has following labs:
1. MANOMETRY LAB
2. PROTECTION AND INTERLOCK LAB
3. AUTOMATION LAB
4. WATER TREATEMENT LAB
5. FURNACE SAFETY SUPERVISORY SYSTEM(FSSS)
6. ELECTRONICS TEST LAB
This department is the brain of the plant because from the relays to transmitters
followed by the electronic computation chipsets and recorders and lastly the
controlling circuitry, all fall under this.
TRANSMITTERS: 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.
MANOMETER: 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.
The U-Tube or Manometer: Liquid contained in a tube bend in the form of a U will
respond to a difference in pressure across the two limbs. A glass tube of uniform
cross-sectional-area is bent to form a U and partly filed with a liquid of known density
Measurement of Atmospheric Pressure: Atmospheric pressure will support calcium
of Mercury approximately 30 inches in a U-tube provided a good vacuum is
maintained in one limb. Ifa U-tube is replaced with a straight limb about 35 inches
long, one end closed, then being filed with clean, dry mercury and then inverted in a
container of mercury open to the atmosphere, the mercury would fall in the tube
forming a good vacuum above it.
Single Tube Manometer This is used for measuring low pressure and for testing and
recalibration low-pressure instruments of al types. If the ratio of the area of one tube
is considerably greater than other, then practically al the movement takes place in the
smal manometer tube and for al practical purposes only the one limb need be read.
Kenotometer The low pressures produced in steam condensers are usually measured
in inches of mercury, marking downwards from atmospheric pressure. A high
working vacuum of 29.5 inches of mercury is the same as an absolute pressure of 0.5
inch of mercury, or approximately 0.25 p.s.i (absolute). One device for measuring the
absolute pressure in a condenser is the Kenotometer.
Bourdon Pressure Gauge: This is the most commonly used of al pressure measuring
devices. (Range 10- 80,000 p.s.i). Here, a tube of oval section is bent into a circular
arc. One end is sealed and the other end fixed to a solid block into which the applied
pressure is fed. The tube will "uncurl" as the pressure (operating Force) increases, or
will 'Curl up' as the vacuum increases; so giving a movement of the free end which is
proportional to the change in pressure. The Controlling Force will depend upon the
thickness of the tube and the material from which it is made.
Fig.3 Typical Arrangement of Bourden Gauge
SpecialTypes Of Pressure Gauges
Spiral Tube: This type is used for low-pressure indication and recording when a C-
shaped Bourden tube is not suitable and where power is required. By making the oval
tube in the form of a spiral an enlarged movement of the free end is achieved and thus
the tube becomes more sensitive over pressure ranges below 10 p.s.i.
Helical Tube: For higher pressures the tube is wound in the form of a helix and is
often used in pressure recorders. Range 0-80,000 p.s.i.
Critical Type: This is used in boiler houses to enable distant reading of the steam
pressure to be made to the nearest 1 p.s.i over a range of say ± 15 p.s.i. The movement
of a pressure sensitive element is transmitted to a pointer and scale via linkages,
which only allow the pointer to operate over a selected range of pressure to either side
of the normal steam pressure.
Fig.4 Dewrance Critical Pressure Gauge
Measurement of Level
'Sight Glass' is used for local indication on closed or open vessels. A sight glass is a
tube of toughened glass connected at both ends through packed unions and vessel.
The liquid level will be the same as that in the vessel. Valves are provided for
isolation and blow down.
"Float with Gauge Post" is normally used tor local indication on closed or open
"Float Operated Dial" are used for small tanks and congested areas. The float arm is
connected to a quadrant and pinion which rotates the pointer over a scale.
Pressure operated types Since the pressure acting on any area at the bottom of a tank
depends only upon the depth and density of the contained liquid, a measure of this
pressure is proportional to the liquid level.
Bourden Pressure Gauge A Bourdon pressure gauge calibrated in any fact head is
often connected to a tank at or near the datum level. "Mercury Manometer" is used
for remote indication of liquid level. The working principle is the same as that of a
manometer one limp of a U-tube is connected to the tank, the other being open to
atmosphere. The manometer liquid must not mix with the liquid in the vessel, and
where the manometer is at a different level to the vessel, the static head must be
allowed in the design of the manometer.
'Diaphragm Type' is used for remote level indication in open tanks or docks etc. A
pressure change created by the movement of a diaphragm is proportional to a change
in liquid level above the diaphragm. This consists of a cylindrical box with a rubber or
plastic diaphragm across its open end as the level increases .the liquid pressure on the
diaphragm increases and the air inside is compressed. This pressure is transmitted via
a capillary tube to an indicator or recorder incorporating a pressure measuring
Sealed Capsule Type The application and principle is the same as for the diaphragm
box. In this type, a capsule filed with an inert gas under a slight pressure is exposed to
the pressure due to the head of liquid and is connected by a capillary to an indicator.
In some cases the capsule is fitted external to the tank and is so arranged that it can be
removed whilst the tank is still full, a spring loaded valve automatically shutting of
the tapping point.
Air Purge System This system provides the simplest means of obtaining an
indication of level, or volume, at a reasonable distance and above or below, the liquid
being measured. The pressure exerted inside an open ended tube below the surface of
a liquid is proportional to the depth of the liquid.
Fig.5 Air Purge Level Measurement
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
provided for all the equipments. Tripping can be considered as the series of
instructions connected through OR GATE. When a fault occurs and any one of the
tripping is satisfied a signal is sent to the relay, which trips the circuit. 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
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
3. 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
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. Once the
measured is common i.e. pressure the control circuits can easily be designed with
single chips having multiple applications. Another point is the universality of the
supply, the laws of electronic state that it can be any where between 12V and 35V in
the plant. All the control instruments are excited by 24V supply (4-20mA) because
voltage can be mathematically handled with ease therefore all control systems use
voltage system for computation. The latest technology is the use of ‘ETHERNET’ for
The most important parameter in thermal power plant is temperature and its
measurement plays a vital role in safe operation of the plant. Rise of temperature in a
substance is due to the resultant increase in molecular activity of the substance on
application of heat; which increases the internal energy of the material
. The change may be observed with substance itself or in a subsidiary system in
Fig.6 Rod Type Thermostat
Solid Rod Thermometers: A temperature sensing - Controlling device may be
designed incorporating in its construction the principle that some metals expand more
than others for the same temperature range.
Bi-Metalic Strip : These are composed of two metals, as the name implies, whose
coeficients of linear expansion are dissimilar. These two metal plates are welded
together as a sandwich. When heated, both metals expand, but the metal with greatest
coeficient of linear expansion wil expand more causing the sandwich to curl up or
down depending on the position of this metal.
Fig.7 Helical Bi-Metallic Strip
Liquid in Glass Thermometers : The coeficient of cubical expansion of
mercury is about eight time greater that of glass. Therefore, a glass container holding
mercury, when heated, wil expand far less than the mercury it contains. At a high
temperature the mercury will occupy a greater fraction of the volume of the container
than it will at a low temperature.
Under normal atmospheric conditions mercury normally boils at a temperature of
(347°C). To extend the range of a mercury in glass thermometer beyond this point the
top end of a thermometer bore opens into a bulb which is many times larger in
capacity than the bore. This bulb plus the bore above the mercury, is then filed with
nitrogen or carbon dioxide gas at a sufficiently high pressure to prevent boiling at the
highest temperature to which the thermometer may be used.
Mercury in Steel: The range of liquid in glass thermometers although quite large,
does not lend itself to al industrial practices. This fact is obvious by the delicate nature
of glass also the position of the measuring element is not always the best position to
read the result. Types of Hg in Steel Thermometers are:
Bourdon Tube : Most common and simplest type
Spiral type : More sensitive and used where compactness is necessary
Helical Type : Most sensitive and compact.Pointer may be mounted direct on
end of helix which rotates, thus eliminating backlash and lost motion.
Fig.8 Liquid Expansion Thermometer with “C” Bourden
(1) 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.
Fig.9 Bulb Forms
A. PLAIN BULB B. UNION BULB; C. POCKET BULB D. WALL MOUNTING
E. SHORT COtL. F. LONG COIL; G. FINNED STRAIGHT H.WATCH CAPSULE
2) ULTRA VIOLET SENSOR : 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.
(3) 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.
(4) 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).
Gas Thermometers : In Efect of Heat, the volume of a gas. at constant pressure,
wil change with relation to temperature change, and that at constant volume the
pressure changes in relation to temperature. Therefore, if a bulb, capillary and
bourdon tube enclose a certain volume of gas and the both of that’ assembly is
subjected to heat, or change of the same, the changes of pressure, effected by the heat,
within the system, can be directly related to temperature. The later will, of course be
shown though the movement of the free end of the bourdon tube.
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 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
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.
ANNUNCIATION CARDS : 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.
ECOLOGICAL MONITORING PROGRAMME
NTPC has undertaken a comprehensive Ecological Monitoring Programme through
Satellite Imagery Studies covering an area of about 25 Kms radius around some of its
major plants. The studies have been conducted through National Remote Sensing
Agency (NRSA), Hyderabad at its power stations at Ramagundam, Farakka, Korba,
Vindhyachal, Rihand and Singrauli. These studies have revealed significant
environmental gains in the vicinity areas of the project as a result of pursuing sound
environment management practices. Some of these important gains which have been
noticed are increase in dense forest area, increase in agriculture area, increase in
average rainfall, decrease in waste land etc. In general, the studies, as such, have
revealed that there is no significant adverse impact on the ecology due to the project
activities in any of these stations. Such studies conducted from time to time around a
power project have established comprehensive environment status at various post
operational stages of the project.
USE OF WASTE PRODUCTS & SERVICES -ASH UTILIZATION
Ash is the main solid waste which is put into use for various products and services.
NTPC has adopted user friendly policy guidelines on ash utilisation.
In order to motivate entrepreneurs to come forward with ash utilisation schemes,
NTPC offers several facilities and incentives. These include free issue of all types of
ash viz. Dry Fly Ash / Pond Ash / Bottom Ash and infrastructure facilities, wherever
feasible. Necessary help and assistance is also offered to facilitate procurement of
land, supply of electricity etc from Government Authorities. Necessary techno-
managerial assistance is given wherever considered necessary. Besides, NTPC uses
only ash based bricks and Fly Ash portland pozzolana cement (FAPPC) in most of its
construction activities. Demonstration projects are taken up in areas of Agriculture,
Building materials, Mine filling etc. The utilisation of ash and ash based products is
progressively increasing as a result of the concrete efforts of these groups.
Environment Management, Occupational Health and
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.
While deciding the appropriate technology for its projects, NTPC integrates many
environmental provisions into the plant design. In order to ensure that NTPC comply
with all the stipulated environment norms, various state-of-the-art pollution control
systems / devices as mentioned below have been installed to control air and water
Flue Gas Stacks
Coal Settling Pits / Oil Settling Pits
DE & DS System
Ash Dykes & Ash Disposal systems
Ash Water Recycling System
Dry Ash Extraction System (DAES)
Liquid Waste Treatment Plants & Management System
Sewage Treatment Plants & Facilities
Environmental Institutional Set-up
Up gradation & retrofitting of Pollution Control Systems