NTPC
National Thermal Power Corporation
Project: Study the Working Principles and Functioning of
the Power plant
SAILENT FEATURES OF RAMAGUNDAM SUPER THERMAL POWER
STATION(RSTPS)
Installed Capacity
Stage 1 - 3*200MW
Stage 2 - 3*500MW
Stage 3 - 1*500MW
Total = 2600MW
Location
Ramagundam, Andhra Pradesh, India
Coal Source
South Godavari Coal Fields of Singareni Collieries
for Stage 1&2
Kobra Coal Fields of SECL for Stage 3
Coal Consumption
10 million tones per annum
Coal Transportation
Merry go round system of 21 km
Water Source
Sri Ram Sagar Dam on Godavari River from
Pochampad Reservoir
Transmission System
2457km of 400kv line
-Salient Features Continued
-Salient Features Continued
Total land allotted for RSTPS
~10000 acres
Total Investment
20592.2 million rupees for Stage 1&2
18184.6 million rupees for Stage 3
Length of Earthed Dam
8.5km
Height of Chimney
Stage 1 – 225m
Stage 2 – 229m
Stage 3 – 275m
Beneficiary States
Andhra Pradesh
Kerala
Karnataka
Goa
Pondicherry
Tamil Nadu
PGCIL(for HVDC)
UNITS COMMISSIONING SCHEDULE
Stage
Unit
Generation in
MW
Date of Installation
1
I
II
III
200
200
200
November 1983
May 1984
December 1984
2
IV
V
VI
500
500
500
June 1988
March 1989
October 1989
3
VII
500
August 2004
DISTRIBUTION OF ELECTRICITY
Percentage
Andhra Pradesh
Distribution
(MW)
754
Tamilnadu
598
23%
Karnataka
442
17%
Kerala
312
12%
Goa
130
05%
Pondicherry
65
2.5%
State
29%
Topics studied
Out of the many departments in the

power plant we have studied a few of

them in detail.

We have learnt about the following in the 
Electrical field:

 The Switch Yard

 The Generator
 Transformers
 The HT(High Tension) motors
 The LT(Low Tension) motors
 The ESP(Electro Static Precipitators)
The topics learnt related to Mechanical
and Civil fields ate as follows:
 Boiler ( Operation and Maintenance)
 Coal conveyer belts
Coals mills
Furnaces
Feeders
Boiler drum
Condensers
Super heaters
The Switch yard
SWITCHYARD EQUIPMENT:
 Circuit Breakers
 Isolators
 Earth switch
 Bus Bar
 Surge/Lightning Arresters
 Current Transformer
 Capacitive Voltage Transformer
 Wave trap
 One And Half Breaker Scheme
To perform switchyard operation
activities perfectly, operation staff
should have good knowledge about
the equipment provided in
switchyard as well as in control room.
They should be familiar with the
control system adopted here and a
good understanding about the
procedures to be followed during the
emergencies, outage requirements
and charging. Brief description about
switchyard equipment is given
below.
CIRCUIT BREAKER:
It is an automatic device capable of making and breaking an Electrical Circuit under normal and
abnormal conditions such as short circuits. SF6 is the arc quenching media for all the 400 KV and
220 KV breakers installed in the switchyard. Pneumatic operating system is provided in AEG,
ABB and NGEF make breakers and Hydraulic operating system is provided in BHEL make
breakers. 132KV breakers provided in 132 KV lines are of Minimum oil type operating on spring
charge mechanism.
ISOLATORS:
Isolator is an off load device provided in conjunction with circuit breaker to disconnect the
equipment or the section, which is to be isolated from all other live parts. The isolators provided
in the switchyard are of central break type. The operation of Isolators can be done from control
room (remote) or local. Motorized operation for opening & closing of Isolator is provided,
however Isolators can also be opened & closed manually in the even of non-availability of
motorized operation.
EARTH SWITCH:
Earth switch is mounted on the isolator base on the line side or breaker side depending upon the
position of the isolator. The earth switch usually comprises of a vertical break switch arm with
the contact, which engages with the isolator contact on the line side. Earth switch is required to
discharge the trapped charges on the line or equipment (under shut down) to earth for
maintaining safety. Earth switch can be operated only from local either by electrical operation
or manually.
BUSBAR:
Busbar is an Aluminum tube of 4” IPS having wall thickness of 0.4”, where all incoming and
outgoing feeders are connected in a schematic way to enable smooth operation and
Maintenance of equipment without any interruption to the system. At RSTPS one and half
breaker scheme is provided for 200 MW generator feeders and 400 KV outgoing lines, Twobreaker scheme is provided for 500 MW generator feeders.
SURGE / LIGHTING ARRESTERS:
Surge Arresters are provided to ground the over voltage surges caused by switching
and lighting surges. Surge Arresters provide leakage path to the ground whenever
the system voltage rises above the specified value. They are equipped with surge
monitors, which measures the leakage currents and a counter to record the number
of surges taken place.
CURRENT TRANSFORMER (CT):
Current Transformers are provided to step down the current to low values suitable
for measuring protection and control instruments. Current Transformers also
isolate measuring and protective devices from high system voltage. CTs in the
switchyard consist of five secondary cores. Core 1&2 are used for bus bar protection,
4 & 5 are for main 1&2 protection and core 3 is for measuring instruments.
CAPACITIVE VOLTAGE TRANSFORMER (CVT):
CVTs step-down the system voltage to sufficiently low value (110V) for measuring,
protection and synchronizing circuits. CVT has a H.F. terminal point for receiving &
transmitting the high frequency signals for carrier protection and communication.
WAVE TRAP:
Wave Trap is a parallel resonant circuit tuned to the carrier frequency connected in
series with the line conductor at each end of the protected transmission line
section. Wave trap offers high impedance path for high frequency signals and low
impedance path for power frequency current. This keeps carrier signal confined to
the protected line section and does not allow the carrier signals to flow into the
neighboring sections.
One and half breaker scheme :
In Ramagundam we use one and half Breaker scheme with 3 current transformer
method.
RSTPS 400KV SWITCHYARD
To interconnect generating station to the load centers different
voltage transformations and power switching operations are
necessary. The place where the voltage transformations and power
switching operations takes place for evacuating power is called
switchyard.
 400KV Switchyard at Ramagundam super thermal power station
is the most vital switching station in the southern grid. A total of
2600MW of bulk power generated by three 200MW units and
four 500MW units of NTPC Ramagundam is evacuated for
supplying to the southern states.

Switchyard consist of two 400kv bus bar system fed by 7
numbers of generator feeders, 9 numbers of 400kv feeders, 3
numbers of 220kv feeders and two numbers of 132kv feeders as
shown in the single line diagram of 400kv switchyard.

In addition to the above, three Tie Transformers, five
Auto Transformers and two shunt reactors are provided as
shown in the single line diagram of 400kv switchyard.
TRANSFORMER
Transformer is a static piece of apparatus by means of which
electric power in one circuit is transformed to electric power of
the same frequency of another circuit.
Types of Transformers in a Power Plant
 Generator Transformer (GT)
 Unit Auxiliary Transformer (UAT)
 Station Transformer (ST)
 Tie Transformer
 Auto Transformer
Transformer Properties and Purpose
The use of transformers has become inevitable in any thermal power plant rather in
any industry today:
 For example: In 500MW generation at RSTPS stage-II, stage-III the electricity is
generated at 21KVand current is approximately 16000A. If we transmit the same
electrical energy to the grid then to transmit a current of 16000A, we need very
very heavy conductors, very strong transmission towers. Moreover, the lines loss
shall be extremely high because current is very-very high and loss is proportional
to the square of the current.
 So, by using generator transformers (G.Ts) the voltage level is raised to the level
of 400KV, hence the current level comes to 16000A to 800A. By doing so, the
current is reduced approx. by 1/20 times.
 Hence the losses are reduced by 1/400 times. The high voltage levels (i.e., 400kv)
can be easily tackled by making high towers. The cost of such towers is quite
low, comparatively and conductor size also will be very low for 800A current.
Properties: The efficiency of the transformer is very high, as there are no moving
parts there are no mechanical losses.
GENERATOR
TRANSFORMER
The importance of Generator Transformer is
that it is the prime component required for
the transmission of energy(electricity
produced) from the plant to the grid at a
specific voltage. The GT’s are usually step-up
transformers with where the Low-Voltage
Delta windings energized by the generator
voltage and the High-Voltage Star windings
are connected to the transmission lines. The
Generator is connected to this transformer
by the bus duct. This transformer is used to
step up the generating voltage of 18 & 21KV
to grid voltage (400kV).
This transformer is generally provided with
OFAF cooling. It is also provided with off
circuit/on load taps on the high voltage side.
This transformer has elaborate cooling
system consisting of number of oil pumps
and cooling fans apart from various
accessories.
 SPECIFICATIONS OF THE TRANSFORMER:
Manufacturer
Mitsubishi
No. of units
3
Rating HV&LV {MVA}
200MVA
Rated voltage, HV
420/3KV
Rated voltage, HV
21HV
Rated current, HV
825amps
Rated current, LV
9520amps
No. Of phases
1
Frequency
50Hz
Type of cooling
OFAF(Oil Forced Air Fan)
UNIT AUXILIARY TRANSFORMER
 The UAT draws its input
from the main bus-duct 
connecting generator to the
Generator Transformer.
 The total KVA capacity of
unit auxiliary transformer
required can be determined
by assuming 0.85 power
factors and 0.9 efficiency
for total auxiliary motor
load.
It is safe and desirable to
provide about 20% excess
capacity than circulate so as
to provide for
miscellaneous auxiliaries
and possible increase in
auxiliary load.
STATION TRANSFORMERS
 The station transformer is
required to feed power to
the auxiliaries during start
ups.
 This transformer is normally
rated for the initial auxiliary
load requirements of unit.
In typical cases, this load is 
of the order of 60% of the
load at full generating
capacity.
 But in large stations where
more than one units are
operating, the station
transformers should have
sufficient capacity to start
two units at a time in
addition to feeding the
common auxiliaries.
It is also provided with on
load tap changer to cater to
the fluctuating voltage of
the grid.
TIE TRANSFORMERS
 The TIE Transformers are  The capacity of TIE
installed to tie (connect)
Transformer should be at
between the GRID and the
least the sum of connecting
Station Auxiliaries through
station Transformers plus
Station Transformers.
miscellaneous
requirements.
 Generally it is used for two
purposes one for it takes  The no of TIE Transformers
400KV voltage from 400KV more than one improves
bus bar and step down to
reliability.
33KV and it is used for

station supply system
having 33KV switch gear.
AUTO TRANSFORMER
 It is a single winding
transformer this is used to
increase or reduce the voltage
at required level. Both primary
and secondary are connected
electrically, magnetically and
mechanically. The portion of
the winding works as primary
and other as secondary.
 The main purpose of
autotransformer is to step
down the high voltage to feed
the load near by generating
station. The transformer used
in NTPC {RAMAGUNDAM}
having a tertiary, which is
having a voltage of 33kv, but is
not in use. To ensure security
of supply, autotransformers
are installed in two, three or
four such that in case of one
transformer being unavailable,
the load is carried by
remaining transformer.
Generator
A Generator is an A.C/D.C machine that converts mechanical energy
into electrical energy based on the principle faraday’s laws of
electromagnetic induction. In an A.C generator, armature is
stationary and field is rotatory. Whereas in a D.C generator the field
system is stationary and armature is rotatory.
Operating principle:
The magnetic poles are excited or magnetized from D.C supply by
a D.C source i.e., D.C shunt generator, which is belted or mounted
on the same shaft of alternator. Because the field magnet(s) is
rotating this current is supplied through slip rings. When the rotor
rotates the stator conductors are cut by the magnetic flux inducing
EMF in them , because the magnetic poles are alternatively north
and south . Due to the induced EMF, current is developed in
armature conductors.
 The Importance of Generator
protection
 The Generator is very complex and elaborative.
 Generator(s) is a large machine and is connected to
the bus bars. Unit transformer, Auxiliary transformer
and bus system accompany it
 It is also accompanied by excitation system, prime
mover, voltage regulation system and cooling system
etc., Hence it is not single equipment the protection
of generators should be coordinated with the
associated equipment.
 It is a costly and an important equipment and
therefore shut off would result in emergency power
shortages.
 Methods of protection







The Generator should be protected from
several faults The present practice and other
alternative protection from several other abnormal
conditions are done using alarms and indications. A
power plant whose installed capacity is >100MW
should be properly protected from the faults below,
Excessive temperature in stator
Differential protection
Earth fault protection
Stator inter turn protection
Loss of field protection
Uneven temperatures at bearings.
CRUSHERHOUSE:
 The coal from the track hopper is transferred to the
crusher house through conveyor belts. In this crusher
house the coal is made into 20mm by crushing. The
crushed coal is sent to the bunkers and some of the coal is
sent to reserve called coal handling plant or stack yard.
BUNKERS:
Bunkers are the coal storage tanks which will be near the
boilers. The coal from the bunkers is sent to the mills. If the
bunkers are filled up then the coal is sent to the coal handling
plant to keep stock. In case of any interruption in the supply
of coal, the coal is taken from the stack yard or coal handling
plant and sent to the bunkers .we are using the special
equipment called Reclaimers which consists of buckets so
that the coal kept in the yard is taken through buckets and
place on the conveyor belts.
 MILLS
The most efficient way of utilizing coal for steam generation is to burn it into
pulverized form. Coal can be pulverized in any of the following:
 Slow speed mills(15 to 25rpm)
 Medium speed mills(50 to 100rpm)
 High speed mills(750 to 1000rpm)
Selection of the type of the mill depends on many factors but mainly on capital,
operation, maintenance, cost and quality of end-product required. The milling
system is considered as the heart of a power plant as it decides the overall
performance of the power plant.
 The coal to be ground is fed into the center of the mill through a vertical
pipe connecting coal feeder & mill from the end of the center pipe the coal
is dropped onto a revolving bowl. Centrifugal force causes the coal to travel
it towards the perimeter of the bowl. During its travel the coal passes
between the bull ring segments the grinding rolls. The springs which load
the rolls impart the pressure necessary for grinding. The partially pulverized
coal continues to flow outwards and over the edge of the bowl. Hot primary
air enters the mill side housing below the bowl and is directed upwards
through the annulus formed by separator body and bowl. This upward
movement is through a fixed or rotating vane wheel. The pulverized coal is
directly sent to boiler and heavier particles lose their momentum and return
back to mills.
 PA FANS:
Primary air fan is used to discharge air to carry the fuel(Coal) from
the mills to the boiler furnace. It is an axial type fan. These are
present before the air preheaters where the ambient air gets
heated up in the air heaters and then is passed to the pulverized.
The pulverized coal in smooth powder form is lifted off by primary
air discharged from the PA fan, then pass through the classifier to
the coal nozzles at the burner section. There are two PA fans for
each unit.
 FD FANS:
The main purpose of this fan is to supply adequate amount of air to
the furnace for complete combustion. It is an axial type fan. The air
supplied by the PAF is not sufficient for combustion process. The
additional air required is supplied using FD fans (2 per unit -50%
capacities each). This sucks air from atmosphere pressurizes it and
sends it into the furnace. Prior to sending pressurized air is heated
in secondary air pre heater (SAPH). The source of heating in SAPH
is the hot steam from low pressure turbine. FD fan maintains the
pressure inside the furnace.
ID FANS:
 The main purpose of this fan is to suck the flue gases from the
furnace and send it to the atmosphere through chimney and
maintain furnace draft. The ash particles in the flue gases are
precipitated in the ESP (Electro Static Precipitator) before
entering the ID fan. It is an axial entry and radial discharge type.
It also maintains the pressure inside the furnace.

The flue gases pass through the ID fans enters the bus duct
and then to the chimney. The provision of the bus ducts avoids
the problem of air to be accumulated when one of the
equipment fails. Example: If one of the ID fans does not work,
another ID fan sucks the inlet air of the other ID fan through the
common bus duct.
 These fans have a lower speed and are less susceptible to wear
and tear due to the abrasive flue gases. The control of the I.D.
fans is achieved through a variable speed Hydraulic coupling and
motorized inlet damper. By introducing variable speed control
through a hydraulic coupling the losses in the fan at various load
has been minimized and efficiency of the fan has remained high
at all operating conditions.
BOILERS
 Fire-Tube Boilers:
Fire-tube boilers rely on hot gases circulating through the boiler inside
tubes that are submerged in water. These gases usually make several
passes through the tubes, thereby transferring their heat through the
tube walls and causing the water to boil on the other side. Fire-tube
boilers are generally available in the range of 20 through 800 boiler
horsepower and in pressures up to 150 psi.
 Electric Boilers:
Electric boilers are very efficient sources of hot water or steam, which
are available in ratings from 5 to over 50,000 kW. They can provide
sufficient heat for any HVAC requirement in applications ranging from
humidification to primary heat sources.
 Water Tube Boiler:
Here the heat source is outside the tubes and the water to be heated is
inside. Most high-pressure and large boilers are of this type. In the
water-tube boiler, gases flow over water-filled tubes. These waterfilled tubes are in turn connected to large containers called drums.
Steaming Capacity:
Large boiler capacities are often given in ton’s of steam
evaporated per hour under specified steam conditions
Combustion of coal:
 Carbon, hydrogen, sulphur
are sources of heat on
combustion.
 Surface moisture removed
on heating during
pulverization.
 Inherent moisture and
volatiles are released at
higher temperature, making
coal porous and leading to
char/ coke formation.
(Thermal preparation stage)
A STEAM GENERATOR IS
A COMPLEX INTEGRATION
OF THE FOLLOWING
ACCESSORIES:
* ECONOMISER
* LTSH
* BOILER DRUM
* DIV PANEL
* DOWN COMERS
* PLATEN SH
* CCW PUMPS
* REHEATER
* BOTTOM RING HEADER
* BURNERS
* WATER WALLS
* APHs
Steam Flows from Boiler to turbine
Steam turbines are one of the oldest prime mover technologies still in use.
Steam turbines extract heat from and transform it into mechanical work by
expanding the steam from high pressure to low pressures
TURBINES
Turbine is a shaft coupled to the generator and is divided in
to three categories having same shaft coupling.
 1. High Pressure Turbine (HPT)
 2. Intermediate Pressure Turbine (IPT)
 3. Low Pressure Turbine (LPT)
Some quantity of steam is tapped from IPT, LPT and used to
heat feed water in Low Pressure and High Pressure Heaters.
Characteristics
 Run from <1MW to >1300MW
 High pressure steam flows through the turbine blades and
turns the turbines shaft
 Steam turbine shaft is connected to and electric generator
for producing electricity.
 Power output is proportional to the steam pressure drop
of the steam - the larger the steam, the larger the output
capacity of the turbine generator.
 No emissions from a steam turbine
Classification of Turbines:
Impulse and reaction Turbine
Thus the steam is generated and further action to struck the turbine
then the turbines are two types i.e. impulse and reaction turbine. The
diagrams are shown below
Impulse Turbines
An impulse turbine uses the impact force of the steam jet on the
blades to turn the shaft. Steam expands as it passes through the
nozzles, where its pressure drops and its velocity increases. As the
steam flows through the moving blades, its pressure remains the
same, but its velocity decreases. The steam does not expand as it
flows through the moving blades.
Reaction Turbines
In the reaction turbine, the rotor blades themselves are arranged to
form convergent nozzles. This type of turbine makes use of the
reaction force produced as the steam accelerates through the
nozzles formed by the rotor.
 CONDENSER
After expansion steam enters the condenser. The use of
condenser improves the efficiency of the power plant by
decreasing the exhaust steam pressure below atmosphere.
Condensed steam can be recovered and provides a source of
good and pure feed water to the boiler. Non-condensable
gases are removed from the steam in the condenser.
 CONDENSATE EXTRACTION PUMP (CEP)
It is used to pressurize the water and to lift the water to deaerator level.
 LOW PRESSURE HEATER (LPH)
It is a three stage heater to increase the feed water
temperature to 130degrees. It is placed in between the CEP
and de-aerator. The steam tapped from IPT and LPT is used
to heat the coils in the LPH chamber containing pressurized
water from CEP.
 DEAERATOR:
It is used to separate atmospheric air which may get
mixed with steam as there is vacuum in the condenser
and can damage the turbine blades. Water is sprinkled
from the top to separate the dissolved gases and
atmospheric air and pure feed water is collected.
 BOILER FEED PUMP (BFP):
It pressurizes the feed water from De-aerator to about
200kg/cm2 and sends it to the boiler through the High
Pressure Heater (HPH).
 HIGH PRESSURE HEATER:
It is a two stage pressure heater to heat the feed water
in HPH coils by using the tapped steam from turbine. In
the coils, steam and feed water are sent in opposite
directions for heat exchange. Feed Water Regulating
System (FRS) regulates the quality of water to be fed in
to the boiler.
Condensation Process
The surface condenser is a shell and tube heat exchanger in which
cooling water is circulated through the tubes. The exhaust steam from
the low pressure turbine enters the shell where it is cooled and
converted to condensate (water) by flowing over the tubes as shown
in the adjacent diagram. Such condensers use steam ejectors or rotary
motor-driven exhausters for continuous removal of air and gases from
the steam side to maintain vacuum.
For best efficiency, the temperature in the condenser must be kept as
low as practical in order to achieve the lowest possible pressure in the
condensing steam. Since the condenser temperature can almost
always be kept significantly below 100oC where the vapor pressure of
water is much less than atmospheric pressure, the condenser generally
works under vacuum. Thus leaks of non-condensable air into the
closed loop must be prevented. Plants operating in hot climates may
have to reduce output if their source of condenser cooling water
becomes warmer; unfortunately this usually coincides with periods of
high electrical demand for air conditioning. The condenser generally
uses either circulating cooling water from a cooling tower to reject
waste heat to the atmosphere, or once-through water from a river,
lake or ocean.
ELECTROSTATIC PRECIPITATOR
 Ionization - Charging of particles
It is a device which captures the
dust particles from the flue gas

thereby reducing the chimney
emission
Precipitators function by
electrostatically charging the dust 
particles in the gas stream. The
charged particles are then
attracted to and deposited on
plates or other collection devices.

When enough dust has
accumulated, the collectors are
shaken to dislodge the dust,
causing it to fall with the force of
gravity to hoppers below. The dust
is then removed by a conveyor

system for disposal or recycling
Electrostatic precipitation removes
particles from the exhaust gas
stream of Boiler combustion

process.
Six activities typically take place
Migration - Transporting the
charged particles to the
collecting surfaces
Collection - Precipitation of the
charged particles onto the
collecting surfaces
Charge Dissipation Neutralizing the charged
particles on the collecting
surfaces
Particle Dislodging - Removing
the particles from the collecting
surface to the hopper
Particle Removal - Conveying
the particles from the hopper to
a disposal point
ASH HANDLING PLANT
 Fly Ash Collection
Fly ash is captured and removed from the flue gas by electrostatic
precipitators or fabric bag filters (or sometimes both) located at
the outlet of the furnace and before the induced draft fan. The fly
ash is periodically removed from the collection hoppers below the
precipitators or bag filters. Generally, the fly ash is pneumatically
transported to storage silos for subsequent transport by trucks or
railroad cars.
 Bottom Ash Collection and Disposal
At the bottom of every boiler, a hopper has been provided for
collection of the bottom ash from the bottom of the furnace. This
hopper is always filled with water to quench the ash and clinkers
falling down from the furnace. Some arrangement is included to
crush the clinkers and for conveying the crushed clinkers and
bottom ash to a storage site.
Familiarization of the Power Plant


Submitted by
Anurag Reddy Manda
Ankitha Miryala
Department of Electrical Engineering
The Pennsylvania State University
University Park, PA 16802
May 31st, 2013
Thank You
-Ankitha Miryala
-Anurag Reddy Manda