3. About NTPC
NTPC is India’s largest energy conglomerate with roots planted way back in 1975 to
accelerate power development in India.
NTPC became a Maharatna company in May 2010, one of the only four companies to
be awarded this status.
NTPC was ranked 431st
in the ‘2015, Forbes Global 2000’ ranking of the World’s
biggest companies.
The total installed capacity of the company is 51,653 MW (including JVs) with 20 coal
based and 7 gas based stations. 7 Joint Venture stations are coal based and 12(11- solar,
1 - wind) renewable energy projects and 1 hydro project.
Although the company has 17.73% of the total national capacity, it contributes 25.91%
of total power generation due to its focus on high efficiency.
5. NTPC - Dadri
TOTAL CAPACITY OF DADRI POWER PLANT :-
(A) THERMAL (B) GAS
I:- 04X210 MW = 840 MW I:- 04X130.19
II:- 02X490 MW = 980 MW II:- 02X154.51
TOTAL = 1820 MW TOTAL = 817 MW
(C) SOLAR = 05MW
GRAND TOTAL = 2642 MW
6. SOURCES
Coal source
- Piparwara mine , Jharkhand
- Requirement = 13000 MT/day
Water source
- Upper Ganga Canal
Gas source
- HBJ Pipeline (a major gas pipeline of GAIL)
Hazira-Bijaipur-Jagdishpur
10. Working of a Thermal Power Plant
The coal is brought and crushed to powder. This is feed to boiler for producing heat .
In Boiler the water is converted to steam.
In Superheater the moisture content is removed from the steam and that steam is called super heated
steam.
The superheated steam rotates the shaft of the High Pressure(HP) turbine.
The exhausted steam is sent to Reheater and the steam then rotates the Intermediate Pressure (IP)
turbine.
The steam from the IP Turbine is then feed to Low Pressure(LP) turbine.
The turbine shaft is connected to the Generator, which produces electric power.
The steam expanded in turbine is condensed in a Condenser to be feed into the boiler again.
13. Stack & Reclaimer – It is
used to store the powdered
coal for emergency purpose.
Atmospheric air
–Through FD
fan
14. BOILER
A Boiler is a closed vessel in which water is heated to produce steam by utilizing the
heat generated by coal combustion.
Boilers are classified into two types based on relative position of water and hot gases
:-
Water tube boilers
Fire tube boilers
In Water tube boiler, water flows through tubes
and hot gases of combustion flow over these tubes.
This is high pressure boilers.
15. In Fire tube boiler, the hot products of combustion
passes through tubes surrounded by water . This is low pressure boiler.
In Dadri power plant, Water tube boiler is used.
Saturated steam is generated at a pressure of around 2000-2200 KPa.
It is then heated in Superheater.
16. Auxilliary Components Of a Boiler
Superheater
Economizer
Air-preheater
Reheater
Deaerator
17. Superheater
Superheaters are used to raise the steam temperature above the saturation temperature by absorbing
heat from flue gases to increase plant efficiency.
It removes last traces of moisture and therefore prevents turbine blades from corrosion.
Outlet temperature and pressure of steam coming out from the superheater is 540 °C & 157 kg/cm²
18. Economizer, Air-preheater & Reheater
An Economizer is a heat transfer device used for heating
the feed water with the help of hot flue gases.
It improves the efficiency of the power plant.
Air-preheater is a device which utilizes the waste heat
of the flue gases leaving the Economizer for heating
the air required for combustion.
Reheater is used to increase the temperature of exhaust
steam from HP turbine by utilizing the heat of the hot
flue gases leaving the chimney.
19. Deaerator
A steam generating boiler requires that the boiler feed water should be devoid of air and other
dissolved gases, particularly corrosive ones.
In order to avoid corrosion of the metal, power
station uses a Deaerator, for the removal of air
and other dissolved gases from the boiler
feed water.
A Deaerator has a vertical, domed deaeration section
mounted on top of a horizontal cylindrical vessel
which serves as a deaerated boiler feed water storage
tank.
20. PRIME MOVER(TURBINE)
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and
converts it into mechanical energy.
About 86% of all electric generation in the world is by use of steam turbines.
In a thermal power plant generally 3 turbines are used to increase the efficiency.
High Pressure Turbine(HPT): The superheated steam is directly fed to this turbine to rotate it.
Intermediate Pressure Turbine (IPT) : The output from the HPT is reheated in a reheater and used to
rotate IPT.
Low Pressure Turbine (LPT):The Exhausted steam from the IPT is directly fed to rotate the shaft of
LPT.
21.
22.
23. CONDENSER
It condenses the steam at the exhaust of the turbine
with the help of cooling water.
It creates a very low pressure at the exhaust of turbine,
this helps in converting heat energy of the steam into
mechanical energy in the prime mover.
Condensed steam can be used as feed water to the
boiler.
24. COOLING TOWER
Removes heat from the water discharged from the
condenser so that the water can be discharged into the
river or recirculated or reused.
Air can be circulated in the cooling tower through
natural draft and mechanical draft.
25.
26. ELECTROSTATIC PRECIPITATOR (ESP)
Top view Side View
It is a device which removes dust or other finely divided particles from flue gases by charging the
particles inductively with an electric field, then attracting them to highly charged collector plates. Also
known as precipitator. The process depends on two steps. In the first step the suspension passes
through an electric discharge (corona discharge) area where ionization of the gas occurs. The ions
produced collide with the suspended particles and confer on them an electric charge. The charged
particles drift toward an electrode of opposite sign and are deposited on the electrode where their
electric charge is neutralized.
It has an efficiency of 99.8 % and it is a very high power consuming device of about 1 kwh for 10
thousand m³ of flue gas.
27. PRIMARY AIR FAN (PAF)
Air to blow the coal from the mill to the boiler, called the
primary air, is supplied by a large fan driven by a variable
speed motor.
When mixed with a stream of air the powdered coal
behaves more like a gas than a solid.
Primary air does two jobs – heating the coal powder and
secondly lifting it into the furnace through pipelines.
28. INDUCED DRAUGHT (ID) FAN
It is draws out hot flue gases from the boiler.
The gas has already passed out from Air-
preheater and Electrostatic precipitator
before it reaches ID fan.
The heat from the flue gases or smoke is used
in the air heaters to heat up the primary and
secondary air.
29. CHIMNEY
The chimney is 275 meters' high and
50,000 tonnes of reinforced concrete
were used to make it.
It consists of flues each of which serve
typically two or three boilers.
It is used to discharge flue gases at high
altitude.
30. ELECTRICAL EQUIPMENTS
Alternator
An alternator is coupled to a steam turbine and converts mechanical energy of turbine into electrical energy.
It may be Hydrogen or Air cooled.
The necessary excitation is provided by main and pilot exciters directly coupled to the alternator shaft.
Transformer
Main step- transformer : steps up generated voltage transmission of power.
Station transformer : general purpose
Auxilliary transformers : which supply to individual unit auxiliaries.
Control Room and Switch yard
The control room monitors the overall operation of the plant. It is provided with safety relays and switch gears.
31. ASH HANDLING PLANT
The percentage of ash in coal is 5% in good quality
coal & about 40% in poor quality coal.
Power plants generally use poor quality of coal , thus
amount of ash produced by it is quite large.
A modern 1000MW plant produces about 4800 tons
of ash daily.
The stations use some conveyor arrangement to
carry ash to dump sites.
32. COAL ASH CAN BE USED IN
Fly Ash Bricks / Blocks
Cement Concrete
Road construction
Embankment / Back fills / Land development
Use in agriculture
Mine filling
33. 2. SWITCHYARD STATION
Switchyard means collection of
electrical equipment, where high
voltage electricity is switched using of
various component.
Electrical switchyards are usually part
of a substation where electricity is
transformed from one voltage to
another for the transmission,
distribution.
36. Cont..
A static electrical machine used for transforming power from one circuit
to another circuit without changing frequency is termed as Power
transformer .
The transformers are generally used to step down or step up the voltage
levels of a system for transmission and generation purpose.
These transformers are classified into different types based on their
design, utilization purpose, installation methods.
38. Current transformer
Current transformers are basically used to take the readings of the currents entering the
substation.
This transformer steps down the current from 800 amps to 1 amp.
This is done because we have no instrument for measuring of such a large current
39. Potential transformer
Potential transformer is quite similar to the current transformer, but it is used for taking
samples of high voltages of a system for providing low-voltage to the relays of protection
system and also to the low-rating meters for voltage measurement.
Using this low-voltage measurement, the actual system’s high voltage can be calculated
without measuring high voltages directly to avoid the cost of the measurement system.
40. Conductor
The material or object that obeys the electrical property conductance (mostly made of metals such as
aluminum and copper) and that allows the flow of electric charge is called conductor.
Conductors permit free movement of the flow of electrons through them. These are used for the
transmission of power or electrical energy from one place (generating station) to another place.
Conductors are of different types and mostly aluminum conductors are preferred in practical power
systems.
42. Cont..
The metal which does not allow free movement of electrons or electric charge is
called as an insulator.
Hence, insulators resist electricity with their high resisting property.
There are different types of insulators such as suspension type, strain type, stray
type, shackle, pin type and so on.
A few types of insulators are shown in the above figure. Insulators are used for
insulation purpose while erecting electric poles with conductors to avoid short
circuit and for other insulation requirements.
44. Cont..
Isolator is a manually operated mechanical switch that isolates the faulty section
or the section of a conductor or a part of a circuit of substation meant for repair
from a healthy section in order to avoid occurrence of more severe faults.
Hence, it is also called as a disconnector or disconnecting switch. There are
different types of isolators used for different applications such as single-break
isolator, double-break isolator, bus isolator, line isolator, etc.
46. Cont..
The conductor carrying current and having multiple numbers of incoming and
outgoing line connections can be called as bus bar, which is commonly used in
substations.
These are classified into different types
Single bus
Double bus
Ring bus.
48. Cont..
The substation equipments such as conductors, transformers, etc., are always
erected outdoor.
Whenever light surges occur then, a high-voltage pass through these electrical
components causing damage to them (either temporary or permanent damage
based on the amount of voltage surge).
Therefore, to avoid this difficulty, lightening arresters are placed to pass the
entire lightening surges to earth.
There are other arresters which are used to ground the switching surges called as
surge arresters.
50. Cont..
A circuit breaker is an automatically-operated electrical switch designed to protect an
electrical circuit from damage caused by overload or short circuit.
Its basic function is to detect a fault condition and, by interrupting continuity, to
immediately discontinue electrical flow.
It can make or break a circuit either manually or by remote under normal or fault
conditions.
Actuator lever - used to manually trip and reset the circuit breaker.
Actuator mechanism - forces the contacts together or apart,
Contacts - Allow current when touching and break the current when moved apart
Terminals Bimetallic strip.
51. Cont..
Circuit breaker are used for all type of voltage.
It is using in high power laboratories.
It is using outdoor as well as indoor.
Mostly used circuit breakers are Oil circuit breaker, Air circuit breaker, SF6 circuit
breaker, Vacuum Circuit Breaker, and so on.
53. Cont..
Relays are used for disconnecting the circuits by manual or automatic operation
using circuit breakers.
Relay consists of the coil which is excited or energized and such that making the
contacts of relay closed activates the relay to break or make the circuit
connection.
There are different types of relays such as over current relays, definite time over
current relays, voltage relays, auxiliary relays, reclosing relays, solid state
relays, directional relays, inverse time over current relays, microcontroller
relays, etc. The above figure shows some basic relays and their operation.
55. Cont..
A Capacitor bank is a set of many identical capacitors connected in
series or parallel within a enclosure and is used for the power factor
correction and basic protection of substation.
These capacitor banks are acts as a source of reactive power, and thus,
the phase difference between voltage and current can be reduced by the
capacitor banks. They will increase the ripple current capacity of the
supply.
It avoids undesirable characteristics in the power system. It is the most
economical method for maintaining power factor and of correction of
the power lag problems
56. Miscellaneous equipment
Emerging trends in technological development have created advancement in the
substation installation and maintenance. For example, SCADA (supervisory control and
data acquisition) technique made it possible to control a substation automatically from a
remote location.
