The document provides a summary of a vocational training report at the Mejia Thermal Power Station of the Damodar Valley Corporation. It discusses the key components and processes involved in thermal power generation including: 1) The basic process of converting heat energy from coal combustion into mechanical energy via steam turbines, and then into electrical energy using generators. 2) Important parts of the power station like the coal handling plant, steam generation systems, water handling plant, switchyard and transmission systems. 3) Details on the working of key equipment like generators, switchyards and the processes of synchronization, voltage control and protection systems. 4) The role of auxiliary systems in thermal power generation and distribution of power within

1. DAMODAR VALLEY CORPORATION
MEJIA THERMAL POWER STATION

2. VOCATIONAL TRAINING REPORT
AT
DAMODER VALLEY CORPORATION
MEJIA THERMAL POWER STATION
DURATION:
8th June 2016 to 28th June 2016
UNDER THE GUIDANCE OF
MR. P. K. DUBEY
SUBMITTED BY
SUDIPTA GANGOPADHYAY
DEPARTMENT OF ELECTRICAL ENGINEERING
From
KIIT UNIVERSITY
BHUBANESWAR

3. WHY SUMMER TRAINING??
The training at MTPS was very much useful and helpful. In college, we
have
just gained the theoretical knowledge of various equipments, devices and
machines, but the working of these are not clear.
During the training session at MTPS, I got the understanding of basic
concept of their working. This training have been productive for me as I
came to know the inside working of generator, transformer, switch yard,
coal
handling plant, electrostatic precipitator , cooling tower and their related
accessories. I have realized the role of different engineering streams in a
power station and their correlation.
I am very thankful to the guidance and support of engineers, technicians
and workers of MTPS who have provided their precious time to train me.

4. INTRODUCTION

5. What actually happens…
• In a Thermal Power generating unit, combustion of fossil
fuel (coal, oil or natural gas) occurs in Boiler.
• This heat energy transforms water into steam at high
pressure and temperature.
• This steam is utilised to generate mechanical energy in a
Turbine.
• This mechanical energy, in turn is converted into
electrical energy with the help of an Alternator coupled
with the Turbine.
• The production of electric energy utilising heat energy is
known as thermal power generation.

6. •The heat energy changes into mechanical energy following the
principle of Rankine reheat-regenerative cycle .
•This mechanical energy transforms into electrical energy
based on Faraday’s laws of electromagnetic induction.
• The generated output of Alternator is electrical power of
three-phase alternating current (A.C.).
•A.C. supply has several advantages over direct current (D.C.)
system and hence, it is preferred in modern days.
• The voltage generated is of low magnitude (14 to 21 KV for
different generator rating) and is stepped up suitably with the
help of transformer for efficient and economical transmission
of electric power from generating stations to different load
centres at distant locations.

7. THE INDISPENSABLE WATER…
•The water used in a power plant is generally sea water or river water.
• This water undergoes several chemical treatment processes to attain
suitability of using in Boiler.
•Plant water chemistry for maintaining the quality of water is an area of utmost
importance since it determines the condition of Boiler tube material to sustain
high pressure and temperature.
•Improved water quality gives better life of Boiler tube material, besides its
failure due to external effect like erosion, flame impingement etc. This reduces
the outage of Boiler and thus, saves generation.
•The waste water from different system, as for example: Boiler blow down,
Cooling Tower basin blow down, acidic / alkaline waste water out of De-
Mineralization plant (DM plant), water mixed with oil etc., is discharged into sea
or river maintaining the concentration of harmful ingredients within specified
limits through waste water treatment to keep Ecological balance.

8. Don’t forget the waste…
•Fuel, especially coal, after combustion generates huge quantity of Ash.
•A small part of it gets deposited at the bottom of the Boiler in fused clinker form
(Bottom Ash) while the major part is carried with Boiler exhaust gases as fine ash
particles (Fly Ash).
• The waste of Nuclear Reactor is highly radioactive in nature and as such, its disposal
requires special attention.
•The ash particles present in Boiler exhaust are separated to the extent possible to
keep its concentration within specified limits before releasing Boiler exhaust gases
into atmosphere.
•It is always necessary to keep the harmful Green House Gases (CO2, SOX, NOX),
generated during combustion of fossil fuel, within prescribed limit to maintain the
environment ecologically friendly.
• Boiler bottom ash and separated fly ash are dumped in slurry form at a location
away from the locality (Ash ponds), from where it is disposed off periodically.
•In dry Fly Ash Collection System, it is collected in silos for use in the manufacturing of
cement, brick, tiles etc.

9. What we have seen…
In Damodar Valley Corporation, there are Thermal as well as
HydroElectric power generating units, although thermal capacity
is predominant.
Coal is used as principal fuel in all thermal power
generating units.

10. Damodar Valley Corporation-A brief
Background
Water
Management-
Dams, Barrage ,
Canals & Mining,
Soil
Conservation-
Afforestation..
Social Development-Health ,
Education,Agriculture,social
forestry
Power Generation-Thermal
,Hydel & Gas
Transmission & Distribution-
220kv,132kv & 33kv.
Rural Electrification under
RGGVY
DVC was set up in 1948 by an Act of the Parliament.

11. GENERATING CAPACITY…
Name Location Existing
Capacity
Commissioning
HYDEL
Tilaiya River- Barakar
Dist.-Hazaribagh
State- Jharkhand
4 MW
(2X2 MW)
U-I Feb 53
U-II July 53
Maithon River- Barakar
Dist.- Burdhaman
State- West
Bengal
63.2 MW
(2X20+1X23.2
MW)
U-I Oct 57
U-II Mar 58
U-II Dec 58
Panchet River- Damodar
Dist.- Dhanbad
State -Jhankhand
80 MW
(2X40 MW)
U-I Dec 59
U-II Mar 91
Total Hydel . 147.2 MW

12. Important parts of the station
GENERATOR AND
SWITCHYARD
WATER HANDLING
PLANT(BIPH)
AUXILLIARIES
STEAM (BOILER
AND TURBINE)
COAL HANDLING
PLANT(CHP)

13. * Basic principle,
* Construction & Nameplate
rating ,
* Cooling System,
* Generator Shaft Sealing,
* Generator protection,
* Generator metering &
instrumentation,
* Gen operation.
GENERATOR..

14. (Induced voltage) E = 4.44 fTФ Volt
Ns (synchronous speed) = 120f/p rpm
* Based on Faradays law of
electromagnetic induction,
* Converts mechanical power to
electrical power.
* Basic equations:
BASIC PRINCIPLES
Generator Components:
1.Stator,
2.Rotor,
3.Bearing & lubrication,
4.Cooling system,
5.Terminal Bushing & Bus duct,
6.Slip ring & Brush gear assembly,
7.Sealing system.

15. oStator : The core, stator winding, hydrogen coolers and provides gas tight
enclosure for H2 gas.
oRotor : Rotating magnetic pole, (made of cast Chromium, Nickel, Molybdenum
and Vanadium steel ), radial ventilation holes in slot wedges, Retaining rings for
end turns protects against high centrifugal forces.
oSlip ring & brush gear assembly: provides path for excitation voltage & current
from excitation system.
oBearing & lubrication : Provides support to the rotor shaft, Lubricating oil at a
pressure is provided for cooling of the bearings.
oTerminal bushings & Bust duct: three phase and six neutral terminals of
generator for external connection. Porcelain Bushings provided to insulate the
terminal from stator body. Bus ducts: connects the generator phase terminals to
the LV bushings of generator transformer and HV bushings of unit auxiliary
transformers.
oGenerator cooling system: Copper loss (I2R) in stator & rotor windings ,iron-
losses in core results in heat.
oStator & rotor windings –Hydrogen; Stator wdg –Distilled water

16. STATOR WATER COOLING SYSTEM
MAGNETIC FLTERS
MESH TYPE FILTERS
WATER COOLER
EXPANSION
TANK Gen
DM
MAKEUP
STATOR WATER P/P

17. GENERATOR SHAFT SEALING SYSTEM
To prevent leakage of H2 from gen.(H2 in air is highly
explosive)
Oil (seal oil) is used for sealing hydrogen from generator casing
of both ends
Generator
Main oil Tank
Oil coolers Seal oil
Tank
SOP
Oil injector
hydrogen
From governing and
lubrication system
Differential
pressure
regulator

18. Excitation System
Static Excitation Brushless Excitation
* Field Flashing unit
* Thyristors unit,
* AVR unit,
* Field Breaker ,
* Slip ring & carbon brush
assembly
* Pilot Exciter,
* Main Exciter,
* Thyristors unit,
* DVR unit,
* Field Breaker ,
* Rotating Diodes,

19. Generator
Operations
Synchronization,
 Loading,
 Voltage maintenance,
 Stability and
 Safe tripping/shutting
down
Synchronization
Criteria:
 Voltage,
 Frequency,
 Phase Sequence.
C
B
G
G
synchroscope
Grid
Incoming
Machine
G
T
 Connecting a gen to Bus OR
connecting a running generator
with another in parallel

20. Armature reaction:
Change in the Magnetic flux distribution in the air
gap due to flux created by the armature winding
Effective flux per pole thereby terminal voltage
changes with type of load on the gen (change in
power factor)
Unity P.F load –results in terminal voltage is lower
than the generated voltage
Lagging P.F load— Vt < Ea
Leading P.F load – Vt > Ea
Synchronous reactance- Xs= Xa + Xm
Zs = Ra + jXs

21. Power Angle
characteristics
 δ is power angle or torque
angle
 Real power is maximum
when δ = 90 ⁰

22. Different operating AC Voltage levels in plant,
• 220kv (switchyard & Grid voltage)
• 15.75kv (generation voltage),
• 33kv,
• 11kv ,
• 6.6kv,
• 415 V ,
• 240 V.
• Different operating DC Voltage levels in plant.
• 220V ,(back up/emergency power supply),
• 24V or 26V.
Voltage levels in MTPS (Unit # 1 to 6)

23. SWITCHYARD DISTRIBUTION

24. EQUIPMENTS IN SWITCHYARD…
• * Power Transformers
* CT , PT & CVT,
* Breakers & Isolators,
* Main bus, transfer bus & Feeders
Switchyard
220kv 33kv 11kv

25. Single line diagram (220kv Switchyard)

26. Switchyard operations
Isolator operation ,
Connecting a line or transformer to main bus through its own
circuit breaker,
Use of Bus Couplers,
During Generator synchronization,
Changeover of a running unit from own bkr to B/C bkr & vice
versa,
Live bus changeover in swyd.

27. Switchyard operation contd…
CB
Iso- 2
G
Iso- 3
Iso- 1
Iso- 4
Iso- 3
Iso- 2Iso- 1
Iso- 4
Main Bus -1
Main Bus -2
Transfer Bus
220kv
CB

28. Switchyard protection
 Overcurrent & earth fault protection for
feeders,
 Bus Bar Differential protection,
 LBB protection,
 Distance protection.

29. DC distribution system
Acts as a back up power to most vital equipments in case of failure
of grid supply in plant
a) Control, indication, instrumentation and
annunciation
b) Relay and protection
c) Emergency lub oil pump of the turbine
d) Generator seal oil pump
e) Flame Scanner air fan
f) Fire protection and annunciation system
g) Emergency lighting etc
h) Supply for important valve solenoids, motors (DC)
etc.
DC voltage levels
 220 V DC
 24 V DC

30. ASH HANDLING PLANT
• ESP- Electro static precipitator

31. ESP-Electrostatic precipitator
Electrostatic precipitation is a physical process by which particles
suspended in gas stream are charged electrically, and under the influence
of electric field are separated from the gas stream
Emission control unit,
To trap and remove ash particles from the exhaust
gas,
Efficiency 99.9 %,

32. ESP ( Electrostatic Precipitator)
 Major components of ESP:
 High voltage discharge Electrodes--Emitter electrodes (Plates) -
- Negative charged,
 Grounded collecting Electrodes-- Collector electrodes
(Plates)—Positively charged
 Rapping Systems..(collector & emitter plates rapping)
 Power supplies and control components..(HVR Tfr)
 Hoppers

33. A small part of fly ash gets deposited in Economizer hoppers,
Air pre-heater
ash hoppers and duct hoppers before it takes entry to the
Electrostatic
Precipitator, where majority of fly ash is separated out.
In Electrostatic Precipitator, there are two sets of electrodes
viz.
Collecting electrodes and Emitting (discharge) electrodes. The
Collecting
electrode is made up of steel sheets pressed or rolled to a
special profile. The
Emitting electrode is a thin wire, in helical (or spiral) form.
These two
electrodes are arranged in alternate rows.
ESP

34. A unidirectional high voltage from a rectifier is applied between
these two electrodes connecting its negative polarity to the
emitting electrodes and positive polarity to the collecting
electrodes which are earthed.
Because of the physical configuration, the electric field in the
neighbourhood of the emitting electrode is very high. The dust
laden flue gas from boiler passes between rows of collecting and
discharge electrodes. The gas molecules, which are normally
neutral, are ionized in presence of high electric field. The ionized
positive charges travel towards the discharge electrodes and the
negative charges (ions and electrons) towards the collecting
electrodes.

35. BOILER AND AUXILLIARIES
Working principle of Boiler (Steam Generator):
In Boiler, steam is generated from de-mineralized water by the addition
of heat. The heat generated has two parts:-
Sensible heat Latent heat
It raises the
temparature and
pressure of the water
It converts water
into steam

36. •The steam, thus formed is dry & saturated.
•Further, addition of heat raises the temperature and
pressure of steam, which is known as superheated steam.
• The differential specific weight between steam and water
provides the driving force for natural circulation during the
steam generation process. driving force for natural
circulation during the steam generation process.
• This driving force considerably reduces at pressure
around 175 Kg/cm^2 and is not able to overcome the
frictional resistance of its flow path.
• For this, forced or assisted circulation is employed at
higher sub-critical pressure range due to the reason of
economy.
•At supercritical pressures and above, circulation is forced
one.

37. •In boiler drum, steam is separated out from steam-water
mixture, completely eliminating water particles and also
the detrimental salts.
•The increased concentration of contaminants of drum
water is removed by blow down of water.
•The blow down water is passed to waste channel through
a flash tank.
• The Steam is also contaminated due to ‘priming’ &
‘foaming’ phenomenon.
•The carrying over of water droplets with steam during
higher drum water level, i.e. when the separators or
scrubbers (drum internals) get ineffective, is called
priming.

38. •Sudden release of steam pressure due to
swelling of water level and abrupt change in
firing rate may lead to this phenomenon.
• Foaming is caused due to concentration of
oil, soap, organic matter, suspended
particles or other foreign matter in drum
Water.
•Excessive foaming may result in carrying
over of foam with the steam.

39. Boiler Trip
condition
 All ID fans off,
All FD fans off,
Emg trip optd,
Loss of ALL fuel,
 Furnace Pressure Very
High/low,
 MFT operated,
 Drum Level very High/
Low,
Loss of 220V DC supply>
2sec,
 Turbine trip to boiler trip
logic.
Reheater prot. Trip,
Low air flow <30 %,
Unit flame failure,
< FB & loss of AC,

40. Superheater:
Superheaters (SH) are meant for elevating the steam
temperature above the saturation temperature in phases;
so that maximum work can be extracted from high energy
(enthalpy) steam and after expansion in Turbine, the
dryness fraction does not reach below 80%, for avoiding
Turbine blade erosion/damage and attaining maximum
Turbine internal efficiency. Steam from Boiler Drum passes
through primary superheater placed in the convective zone
of the furnace, then through platen superheater placed in
the radiant zone of furnace and thereafter, through final
superheater placed in the convective zone. The
superheated steam at requisite pressure and temperature
is taken out of boiler to rotate turbo-generator.

41. Air pre-heater:
The air pre-heater absorbs waste heat from flue gas and then
transfers this heat to incoming cold air by means of continuously
rotating heat transfer elements of specially formed metal plates
known as Basket (rotary re-generative air pre-heater) or through
stationery tubes (recuperative or tubular air pre-heater). In re-
generative type, thousands of high efficiency elements are
spaced and compactly arranged with sectors shaped
compartments of a radially divided cylindrical shell called the
rotor. The housing surrounding the rotor is provided with duct
connections at both ends and is adequately sealed by radial and
circumferential sealing members forming an air passage through
one or two sectors of the pre-heater and a gas passage through
the other sector. As the rotor slowly revolves the mass of
elements through the gas and air passages, heat is absorbed by

42. The element surfaces passing through the hot gas stream; then
as these same surfaces are carried through the air stream they
release the stored up heat – thus greatly increasing the
temperature of the incoming air.

43. Coal Handling Plant
COAL HANDLING PLANT(CHP)

48. BIBLIOGRAPHY
• ELECTRICAL MACHINERY Dr. P.S. Bhimbhra
• Damodar Valley Corporation Factoids
• The Internet