Training Report DCCPP, Dholpur

PT&IV at DCCPP, DHOLPUR GCT DEE
SESSION 2014-2018 Page | 1
Chapter 1
INTRODUCTION
DCCPP is situated in the outskirts of Dholpur which is about 55Km. South West of Agra.
Dholpur was considered an ideal location for setting up of a gas power plant having
regards to the availability of land, water, transmission network, proximity to broad gauge
railway , also well connected by roads (G.T. road passes through this city) and being an
important load center for eastern Rajasthan. The total estimated cost of the plant is Rs.
1155 Crore.
The main equipments were supplied by M/s BHEL and it was also the main contractor for
erection, testing and commissioning of the plant. The BOP (Balance of plant) was given to
M/s GEA Energy System. The main fuel used for this plant is R-LNG (liquefied natural
gas) which will be supplied by M/s GAIL. The gas required per day for both units is
1.3MM SCM at 9000Kcal.
The unique feature of this plant is that waste heat from the gas turbine is recovered by a
heat recovery steam generator to power a conventional steam turbine in a combined cycle
configuration. And also a MARK- 6 control system has been introduced for the first time
in the northern region in INDIA.
1.1 Electricity from Natural Gas
Power plant uses several methods to convert gas into electricity. One method is to burn the
gas in a boiler to produce steam, which is then used by a steam turbine to generate
electricity. A more common approach is to burn the gas in a combustion turbine to
generate electricity. Another technology that is growing in a combustion turbine and used
the heat combustion turbine exhaust to make steam to drive a steam turbine. This
technology is called combined cycle and achieves a higher efficiency by using the same
fuel source twice.

Fig 1.1 DCCPP Dholpur
1.2 Method for transforming other power into electrical power
Power plants are classified in the following categories according to the fuel used:
a.) Coal based thermal power plant
b.) Nuclear power plant
c.) Hydroelectric power plant
d.) Solar power plant
e.) Wind power
f.) Gas power plant

Rotating turbines attached to electrical generators produce most commercially available
electricity. Turbines may be driven by using steam. Water, wind or other fluids as an
intermediate energy carrier. The most common usage is by steam in fossil fuel power
plants or nuclear power plants and by water in hydroelectric dams. Alternately turbines
can be driven directly by the combustion of natural gas.

Chapter 2
COMBINED CYCLE POWER GENERATION
2.1 Combined cycle electricity generation
Growth in gas fueled combined cycle system will take place, Because of the attractive
economic environmental and operating characteristics of this natural gas system.
Combined cycle gas turbine plants generate electricity more. Efficiently than conventional
fossil to percent compares with 30 to 50 percent for typical now biological units.
Advantage and disadvantage of Combined cycle electricity generation
a.) Advantage of Combined Cycle Gas Power Plant
High Thermal Efficiency
Low water Requirement
Environmental friendliness
Fast start-up
Low Gestation period
Low Installation Cost
b.) Disadvantage of Combined Cycle Gas Power Plant
Low thermal Efficiency in Open cycle
Higher Cost of Generation
Higher Maintenance Cost

Fig. 2.1 Combined Cycle Gas Power Plant
2.2 Classification of Combined Cycle Gas Power Plant
Table 2.1 Classification of Combined Cycle Gas Power Plant
Size
Plant Capacity
(MW)
GT Capacity
(MW)
Small UP-TO 100 MW 30-40 MW
Medium 150-400 MW 60-120 MW
Large > 400 M > 120 MW
2.3 Environmental effects of combined cycle electricity generation
a.) Natural Gas Fueled
combined cycle units are environmentally performable to conventional coal system the gas
combined cycle unit produces none of the solid waste associated with coal units less than 1
percent of the sulfur dioxide and particulate matter and about 85 percent less nitrogen
oxide produces by a similarity sized new coal unit equipped with pollution control
equipments.

b.) Cogeneration System
Cogeneration is use of a primary energy like natural gas to sequentially produce heat and
electricity. The concept is based on the recovery and use of waste heat produced daring the
generation of electricity. In most electric utility power plants, this waste heat is lost
resulting in substantially lower operating efficiencies than with co-generation.
A variety of natural gas co-generation technologies are currently being used. Including
small pre-packaged units that incorporate all the necessary components for a co-generation
system as well as high efficiency industrial gas turbines. These natural gas co-generation
system are available in sizes ranging from as small as 202 KW to as large as several
hundred megawatts.
c.) Air Emissions
The average emissions rates in the united states from natural gas fired generation are 1135
ibd/meh of carbon dioxide 0.1 ibs/mwh of sulfur dioxide and 1.7 ibs/mwh of nitrogen
oxide compared to the average air emissions from coal fired generation natural gas
produces as much carbon dioxide less than a third as much nitrogen dioxide at the power
plant in addition the process of extraction treatment and transport of the natural gas to the
power plant generators additional emissions.
d.) Design Principle
In a gas turbine, set composed primarily of a compressor burner and the gas turbine
proper. The input temperature to the gas turbine is relatively high but the output temp of
the fuel gas temperature is sufficient for production of steam in the second steam cycle
with live steam temperature in the range of steam cycle depends on the ambient
temperature .The methods of waste heat disposal either by direct cooling by lake river or
sea water or using cooling towers.
e.) Efficiency of CCGT plants
The thermal efficiency of a combined cycle power plant is normally in terms of the net
power output of the plant as a percentage of the lower heating value or net calorific value
of the fuel. In the case of generating only etc. creativity power plant efficiencies of up to
59% can be achieved in the case of combined heat and power generation the efficiency can
increase to about 85%.

2.4 Plant Design Inputs
Ambient temperature range
Ambient air quality
Fuel specifications
Environmental requirements
Peaking capability
Operational flexibility
Plant water quality
Black start facility
2.5 Fuel Specifications
Natural gas/ lng vs naphtha
Natural gas supply pressure
Bridge fuel - naphtha/ hsd
Sulphur content - low preferred
2.6 Working of the Combined Cycle Power Plant
DCCPP located at Dholpur has an unique feature that the same energy source (i.e. natural
gas) is used to rotate both gas and steam turbine without wasting much of energy. As the
name implies it is a combined cycle i.e. waste heat from the gas turbine is recovered by a
heat recovery steam generator to power a conventional steam turbine in a combined cycle
configuration. Hence, the working of both gas and steam turbine is discussed here.

Fig. 2.2 Working of the Combined Cycle Power Plant

Chapter 3
STAGES IN THERMAL POWER PLANT
3.1 Stages in Thermal Power Plant
Fuel handling and ash handling
Boiler stage
Turbine stage
Generation stage
3.2 Fuel handling system
1. Coal handling system
2. Oil handling system
3.2.1 Lignite and Bituminous Coal Handling
The coal for the power plant here is received from Rajnagar (MP) by train. The type of
coal being received are of grades C& D, i.e. Lignite and bituminous. A single wagon
tripper is here for unloading the coal. In that wagon tripper two vibrating feeders are
provided so that coal can be stored in open yard with help of conveyors. Stones and
materials are separated manually and magnet separates iron. After that coal is crushed for
better combustion.
Processed coal is then transmitted to power station through conveyors. Here in this plant
daily consumption of coal is about 3000 to 3200 tonnes per daily use. Different size of
coal is required for different boilers. Here for 30MW and 10MW boilers which are flushed
bed boilers, 6MM size of coal is fed and for 35MW boilers which are pulverized bed
boiler 15MM size of coal is fed.

Table3.1 Specifications of Hammer Mill
Title Specifications
Size RHM-1410
Speed 650 RPM
Machine No. HM-15
Power 150MW
3.2.2 Oil Handling System
This system is implemented only under two conditions:-
During initial system
To maintain the boiler temperature
The oil from the tank is pre-heated through heaters, which is then pumped and fed to the
injection so as to spread up in vapour form.
3.3 Ash Handling System
Coal is burnt out and this heat is used to generate steam and the ashes are separate from
flue gasses through electrostatic precipitator and disposed through ash disposable pump
house.
There are two methods to separate dust particles from flue gasses:
1. Mechanical precipitation having efficiency of 68% to 70%.
2. Electrostatic precipitation having efficiency of 98%.
3.3.1 ESP (Electro Static Precipitator)
a.) Introduction
Flue gasses coming out contains dust/ash of various sizes which creates air pollution so to
separate these the particles from flue gas it is sent to ESP where the ash gets separated and
smoke passes through the chimney .
When the dust practices passes through high electric field the natural dust particles get
collected by the collection electrode, and for this purpose 1 phase high voltage.

b.) Theory
ESP is a high efficient device for extraction of suspended particles and fly ash from the
industrial flue gasses.
c.) Working Principle
ESP can handle large volume of gasses from which solid particles are to be removed.
Advantage of ESP
1. High collection efficiency.
2. Treatment of large volume and at high temperature.
3. Ability of coping with corrosive atmosphere.

Chapter 4
GAS TURBINE
4.1 Working of Gas Turbine
This machine has a single-stage centrifugal compressor and turbine, a recuperator, and foil
bearings. A gas turbine extracts energy from a flow of hot gas produced by combustion of
gas or fuel oil in a stream of compressed air. It has an upstream air compressor (radial or
axial flow) mechanically coupled to a downstream turbine and a combustion chamber in
between. Gas turbine may also refer to just the turbine element.
Energy is released when compressed air is mixed with fuel and ignited in the combustor.
The resulting gases are directed over the turbine's blades, spinning the turbine, and,
mechanically, powering the compressor. Finally, the gases are passed through a nozzle,
generating additional thrust by accelerating the hot exhaust gases by expansion back to
atmospheric pressure. Energy is extracted in the form of shaft power, compressed air and
thrust, in any combination, and used to power aircraft, trains, ships, electrical generators,
and even tanks.
Fig. 4.1 Gas Turbine

A Gas Turbine, also called a combustion turbine, is a rotary engine that extracts energy
from a flow of hot gas produced by combustion of gas in a stream of compressed air. It has
an upstream air compressor radial or axial flow mechanically coupled to a downstream
turbine and a combustion chamber in between. Gas turbine may also refer to just the
turbine element.
Fig 4.2 Gas Pipe Line
The Energy is released when compressed air is mix with fuel and ignited in the combustor.
The resulting gases are directed over the turbine's blades, spinning the turbine and
mechanically, powering the compressor. Finally, the gases are passed through a nozzle,
generating additional thrust by accelerating the hot exhaust gases by expansion back to
atmospheric pressure. Energy is extracted in the form of shaft power, compressed air and
thrust, in any combination, and used to power electrical generators.

4.2 Theory of Operation
Gas turbines are described thermodynamically by the Bray ton cycle, in which air is
compressed isentropic ally, combustion occurs at constant pressure, and expansion over
the turbine occurs isentropic ally back to the starting pressure.
In practice, friction and turbulence cause
a.) Non-Isentropic Compression: For a given overall pressure ratio, the compressor
delivery temperature is higher than ideal.
b.) Non-Isentropic Expansion: Although the turbine temperature drop necessary to
drive the compressor is unaffected, the associated pressure ratio is greater, which
decreases the expansion available to provide useful work.
c.) Pressure losses in the air intake, combustor and exhaust: reduces the expansion
available to provide useful work.
Fig.4.3 Idealized Brayton Cycle

4.3 Gas Power Cycle
Although any cycle may in principle be used as a heat engine or as a refrigerator and heat
pump by just reversing the direction of the process in practice there are big difference and
the study is split between power cycle and refrigeration cycle.
Many gas cycles have been proposed and several are currently used to model real heat.
4.3.1 Bray Ton Cycle
The bray ton cycle named after the American Engineer George Bray ton, is a good model
for the operation of a gas turbines engine. Now a day’s used by practically all aircraft
except the smallest once by fast boast and increasingly been used for stationary power
generation. Particularly when both power and heat are of interest the ideal bray ton cycle
in the T-S and P-V diagram and the regenerative cycle. As with all cyclic heat engines,
higher combustion temperature means greater efficiency.
The limiting factor is the ability of the steel, nickel, ceramic, or other materials that make
up the engine to withstand heat and pressure. Considerable engineering goes into keeping
the turbine parts cool. Most turbines also try to recover exhaust heat, which otherwise is
wasted energy.
The heat released from the exhaust gas has been absorbed by many kms of tubing which
line the boiler. Inside these tubes is water, which takes the heat and is converted into steam
at high temperature and pressure. The type of boiler is called heat recovery steam
generation (HRSG) This steam at high temperature and pressure is sent to the turbine
where it is discharged through the nozzles on to the turbine blades.
The energy of the steam striking on the blades makes the turbine to rotate. Coupled to the
turbine is the rotor of the generator. So when the turbine rotates the rotor of the generator
turns. The rotor is housed inside a stator having heavy coils of copper bars in which
electricity is produced through the movement of magnetic field produced by the rotor.
Electricity passes from stator winding to the transformer, which increases its voltage level
so that it can be transmitted over the lines to far off places. The steam, which has given
away its energy, is changed back into water in the condenser. Condenser contains many
kms of tubing through which cold water is continuously pumped. The steam passing over
the tubes continuously loses heat and is rapidly changed back into water.

Boiler water must be absolutely pure otherwise the tubing of the boiler may get damaged
due to the formation of salts inside the tubes due to the presence of different impurities in
water. To condense large quantities of steam huge and continuous volume of water is
required. In some power stations same water has to be used again and again because there
is not enough water. So the hot water tracts are passed through the cooling towers.
The cooling towers are simply concrete shells acting as a huge chimney creating a draught
of air. The design of cooling towers is such that a draught of air is created in the upward
direction. The water is sprayed at the top of the tower. As it falls down the air flowing in
the upward direction cools it.
The water is collected in a pond from where the water is re-circulated by the pumps to the
condenser. Inevitably, however some of the water is taken away by the draught of water in
the form of vapour and it is this water with familiar white clouds emerging from the
cooling towers.
4.4 HRGS (heat recovery steam generator)
Fig 4.4 HRGS (Heat Recovery Steam Generator)

4.4.1 Salient Features of HRSG
Horizontal Natural Circulation Design.
Steam generation at multiple pressure levels with or without re heaters.
Modular construction with spiral finned tubes for compactness.
Fully drainable heat transfer section
Short installation time.
Ease of operation.
Supplementary Fuel firing system to meet specific customer requirements.
o -In duct firing/Furnace firing.
o Multiple Fuels firing (Oil/Gas).
Low NOx and CO emission.
o Stand by fresh air firing with FD fan for uninterrupted steam supply (FD
Fan mode).
Unfired boiler.
Exhaust gases are used to generate steam.
500 c lower portion.
High pressure circuits two.
6H bar upper porting economizer.
Low temperature portion.
6 bar 202 c (ragging)
Discharge pressure 1H bar steam
Water tube boiler.
Forced circulation boiler.
Vertical boiler.
At 100 c leaver boiler.
Deareater feed storage tank
Circuit feed regulating
Economizer
Evaporator
Super heater
H.P. turbine and L.P. turbine
Twin cylinder turbine.

4.5 Parameters for HRSG
a.) HP Steam
b.) LP Steam
4.5.1 HP Steam (Rated Parameters)
Pressure: 78.2 Kg/Cm2.
Temperature : 514+/- 5 Deg. C
Flow: 187.1 Tph.
4.5.2 LP Steam (Rated Parameters)
Pressure: 5.0 Kg/Cm2.
Temperature : 200 Deg. C
Flow: 39.8 Tph.
Fig 4.5 Arrangement of HRSG DCCPP, Dholpur
ARRANGEMENT OF HRSG DHOLPUR CCPP
HP
SH-II
GT
Exhaust
HP Steam
Drum
LP Steam
Drum
HP
EVP-II
HP
ECO-II
LP
EVP-II
CP
H
LP
SH
HP
ECO-I
HP
SH-I
HP
EVP-I
LP
EVP-II
Spray line
HP Main
Steam Line
LP Main Steam
Line
H
P
Fe
ed
W
at
er
LP
Fe
ed
W
at
er
Co
nd
.
In
/
O
ut
DESHDD GD

Chapter 5
STEAM TURBINE
A Steam Turbine is a device that extracts thermal energy from pressurized steam and uses
it to do mechanical work on a rotating output shaft. Because the turbine generates rotary
motion, it is particularly suited to be used to drive an electrical generator about 90% of all
electricity generation is by use of steam turbines.
The steam turbine is a form of heat engine that derives much of its improvement
in thermodynamic efficiency from the use of multiple stages in the expansion of the steam,
which results in a closer approach to the ideal reversible expansion process.
Fig 5.1 Steam Turbine

5.1 Steam Turbine Auxiliary (STA)
1. Shaft Turning System
2. Feed Water System
3. Air Extraction Water Side
4. CW make up and raw water system
5. Hub Oil System
6. Tacking Oil System
7. Hydraulic Oil System
8. Glained Steam System
(1) Two Glained Steam
(a) Fan
(b) Cooler
(2) Pressure Valve
9. Cooling water system to create low back pressure
10. Two pumps for cooling water are one is service & second is stained
11. In cooling tower fans is use for cooling.
12. Three pumps in Tube water one is service of two is stained.
13. H.P. & L.P. by pass system
14. Air extraction system is used for Steam side removes non condensable from
steam turbine.
15. Feed Water Duration
(A) Hot Water Line
(B) L.P. Steam Line
(C.) H.P. Steam Line
16. Auxiliary raw cooling water com water
Three pump 2.1
Intermediate heat exchanger

Chapter 6
TURBO-GENERATOR AND EXCITATION SYSTEM
6.1 Turbo-Generator
A Turbo generator is an electromechanical device that converts mechanical energy to
electrical energy, using a rotating magnetic field
Fig 6.1 Turbo Generator of Steam Power Plant
6.1.1 Theory behind the Working of a Turbo-Generator
A Turbo generator generally includes a rotor that rotates within a stator core to
convert mechanical energy into electrical energy.
A frame-supported stator core provides a high permeability path for magnetic flux
and a rotor assembly positioned to rotate continuously within the stator core so as
to induce electrical current.
The resulting current is carried by high-current conductors through and out from
the power generator, to connectors that provide the current to a plant bus for power
distribution.

6.1.2 Main Components of Generator
a.) Stator
– Stator Frame (Fabrication & Machining)
b.) Core Assembly
– Stator Core, Core Suspension Arrangement
c.) End Shield
d.) Stator Winding Assembly
– Stator Winding , Winding Assembly, Connecting Bus bar, Terminal
Bushing
e.) Rotor
– Rotor Shaft, Rotor Wedges, Rotor Coils, Wound Rotor, Rotor Assembly
f.) Completing Assembly
– Bearing Assembly, Shaft Seal Assembly, Oil Catchers, Insert Cover etc.
g.) Exciter
h.) Auxiliary Systems
6.2 Functions Of Excitation System
Generation of air gap flux to get electrical output.
To generate synchronizing torque to keep the machine in synchronism.
To generate reactive power (MVAR)
Fast response to system disturbances.
Capability to generate field forcing condition for prompt clearance of pressure.
Fig 6.2 Excitation System of Power Plant

6.3 Brushless Excitation System
Contact less system
Eliminates all problem related to transfer of power between
Stationary and rotating elements
Completely eliminates brushgear,
Slip rings, field breaker.
Eliminates the hazard of changing
Brushes on load
Brush losses are eliminated
reliability is better
Fig 6.3 Brushless Excitation System

6.4 Parameters of Generators
Table 6.1 Rating of Generators
PARAMETERS GTG STG
Type Tari 1080 Tari 1080
Active Power (MW) 112.46 126.2
MVA 132.3 148.47
Speed/Frequency (rpm/Hz) 3000/50 3000/50
Stator Voltage (KV) 10.5 10.5
Stator Current (Amp.) 7275 8164
Cont. Unbalance Current
(%)
10 10
Rated Power Factor (pf) 0.85 (Lagging) 0.8 (Lagging)
Inter Connection of Stator
Winding
Y-Y Y-Y
Rated Field Current (Amp.) 756 825
Rated Field Voltage (V) 319 368
Internal Cooling Air Air
External Cooling Air Water

Chapter 7
220 KV SWITCHYARD AND TRANSFORMERS
7.1 220 KV Switchyard and Different Equipments
7.1.1 Bus Scheme
Main Function Of The Stations Is To Receive The Energy And Transmit It At The
Required Voltage Level With The Facility Of Switching.
At DCCPP Following Are the Bays
1. GTG-1
2. Bus coupler
3. Line-1
4. GTG-2
5. Line-2
6. Line-3
7. STG
7.1.2 Bus System
There Are Mainly Two Buses
1. Main Bus-1
2. Main Bus-2
7.1.3 Isolators
Isolators are used to make or break the circuit on no load. They should never be operated
on load. The isolators installed in the substation have a capacity of 1250 amperes. They
are double end break type; motor operated and can be operated from local as well as
remote.

7.1.4 SF6 Gas Circuit Breakers
In this type of breaker quenching of arc is done by SF6 gas. The opening and closing of
the circuit breaker is done by air.
Fig 7.1 SF6 Circuit Breaker
A) Type Designation
E : SF6 Gas Insulation
L : Generation
F : Out Door Design
SL : Breaker Construction
4 : Code BIL Rated Voltage 4 - 245 / 460 / 1050 KV
1 : No. of chamber
The high voltage circuit breaker type ELF SL 4-1 comprises 3 breaker poles, a common
control cubicle and a pneumatic unit (compressed air plant) a breaker pole consists of :-
SUPPORT (FRAME) - 40000
POLE COLUMN - 41309 N
PNEUMATIC ACTUATOR (PKA) - 90200

A pneumatic unit (97200), an air receiver and a unit compressor is installed to supply the
compressed air. The compressed air stored in the air receiver is distributor to the three
actuator via pipe line.
The common control cubicle (96000), which is installed separately, contains all control
devices and most of the monitoring instrumentation with the exception of the density
monitors 98005 mounted on the middle breaker pole. The pressure switches are installed
in the control cubicle. All three poles columns are filled with insulating gas and
interconnected by means of pipe lines. The gas is monitored by a density monitor 98005
(temp. compensated pressure monitor).
If all the poles of the circuit breaker do not close simultaneously then the pole discrepancy
relay will operate and trip the breaker. Also at the time of tripping, if all the breakers do
not trip simultaneously, then again the tripping command through the pole discrepancy
relay will initiate to trip the breaker and annunciation will appear in the substation control
room and the UCB.
7.2 Maintenance Jobs to be done on 220 KV Switch Yard
7.2.1 Daily Job
a.) Visual checking for any hot spot.
b.) Checking of air leakage from the breaker.
c.) Checking for any gas leakage from the breaker
d.) Checking of air pressure of breaker
e.) Checking of gas pressure of breaker
f.) Checking of oil leakage form CT and CVT
g.) Checking of oil level from CT and CVT
h.) Checking of lubricating oil level in compressors
i.) Checking healthiness of trip circuit for all breakers.
7.2.2 Monthly Job
a.) Thermo vision scanning of conductor joints and attending to the hot spot on available.
b.) Breaker operation checking from local and remote
c.) Isolators operation from remote and local.
d.) Measurement of specific gravity and voltage of 220 V D. C> Battery cells.

7.2.3 Quarterly Job
a.) Breakers
1. Tightening of breaker clamps
2. Cleaning of breaker cubicles
3. Checking of oil level of compressors of SF6 breakers.
4. Lubrication of rollers, mechanism shafts, anti-pumping pin and c clips.
5. Checking operation of breakers through trip coil pumping operation and pole.
6. Checking of pressure of gas and air pressure of breakers.
b.) Isolators
1. Tightening of the jumper clamps.
2. Tightening of electrical connections
3. Cleaning of male female connections
4. Checking of fuses and replacement there F
5. Checking of operation of isolators.
Fig 7.2 Isolator in Switch Yard

c.) Current Transformer (CT)
1. Checking of oil level.
2. Checking of oil and leakage
3. Tightening of jumper clamps
4. Tightening of electrical terminal secondary connection.
d.) Lightning Arrestors (LT)
1. Tightening of jumper connections
2. Tightening of earthing connections
3. Checking of counter reading
4. Checking of porcelain part
5. Checking of grading current
Fig 7.3 Isolator

e.) Capacitive Voltage Transformer (CVT)
1. Checking of oil level and leakage
2. Tightening of HT jumper clamps.
3. Tightening of secondary terminal connections
Fig 7.4 Transformer (high rating capacity)
f.) Battery 220 V D. C.
1. Cleaning of battery terminals
2. Tightening of battery terminal connections
3. Recording of specific gravity and voltage of each cell.

7.3 During Annual Shut Down Of Units
a.) Breakers
1. Checking and cleaning of porcelain part of the breaker.
2. Tightening of breaker clamps.
3. Cleaning of breaker cubical
4. Tightening of all the terminal connection
5. Lubrication
(I) C and D Roller
(II) Locking pins
(III) Anti pumping pins
(IV) Mechanism Shafts
6. Recording of closing and tripping of each phase
7. Recording of insulation resistance value of breaker
8. Checking of annunciator and inter locks.
(I) Air pressure low
(II) Air pressure very low trip circuit cut off
(III) Gas pressure low
(IV)Gas pressure trip circuit off and other ann. of breaker
9. Checking of tripping through
(I) Trip Coil I
(II) Trip Coil II
(III) Through both the trip coils
(IV) Anti-Pumping operation
(V)Pole Discrepancy operation
10. Measurement of resistance of trip cells and closing coils
11. Checking of air leakage and its stoppage
12. Checking the gas leakage
13. Replacing the oil of compressors
14. Checking of auto operation of compressors
15. Complete maintenance of compressors
16. Checking of closing/tripping of breaker from local remote

b.) Isolators
1. Cleaning of male female connections
2. Tightening of all the jumper clamps
3. Lubrication of control rotary post insulator with grease
4. Checking of proper operation of the isolator
5. Tightening of all the nuts and bolts
6. Cleaning the motor cubical
7. Tightening of all the terminal connections
8. Greasing the gear box of motor
9. Checking of all the fuses
10. Checking of operation of isolator from local/remote.
c.) Current Transformers (CT)
1. Checking / cleaning of porcelain part of CT
2. Checking of oil and level and stopping it if low
3. Checking of oil leakage and its stoppage
4. Checking of N2 pressure and maintaining it at 0.2 kg/cm2
5. Tightening of Earthing connection
6. Checking of BDV value of CT oil
7. Tightening of all the secondary terminal connections
8. Cleaning of marshaling box and tightening of terminal connections
9. Recording of IR values of primary and secondary side of CT
10. Tightening of bushing clamps.
d.) Capacitive Voltage Transformers (CVT)
1. Checking of oil level and topping thereof
2. Checking of N2 pressure and maintaining it at 0.2 kg/cm2
3. Tightening of jumper clamps.
4. Tightening of secondary connection
5. Recording of IR values of primary and secondary side
6. BD value of oil

e.) Lightning Arrestor
1. Tightening of jumper connection
2. Recording of IR values
3. Checking of counter readings
4. Checking of grading current
5. Cleaning of porcelain part
6. Checking Tightening of earthling connection
f.) Earth Shielding
It is a mesh of wire upon the tower. Its main purpose is to protect the substation equipment
from direct lightning strokes. Metallic body of each equipment is properly earthed. The
earthling resistance of any switch yard is about 0.2 ohm. Before the building up of the
substation earthing material of G.I. wire is buried in the ground whose depth depends upon
the moisture content of ground. Earthing electrodes are provided at various points. This
increases the number of parallel provided at various points. This increases the number of
parallel paths and hence resistance of earth decreases.
7.4 Power Line Carrier Communication
This is a technique in which power lines are used as communication lines by which we can
make contact with other substation.
The range of frequency used for communication is 300 KHz to 500 kHz.
7.4.1 Working
The voice frequency if converted into electrical signal. These signals are super imposed on
a carrier frequency and transmitted on the line through a coupling capacitor. At the
receiving end wave trap does not allow the modulated signal to enter the power circuit
whereas the coupling capacitor provides a low resistance path to this signal. This signal is
then given to the line matching unit. In the LMU this frequency is matched and after wards
filtration of signal is done. The signal is demodulated and again converted into the voice.

7.5 Different Transformers Installed In Transformer Yard
Transformer is a static device which is used to change the voltage level keeping the power
and frequency same. In the plant transformer is one of the most important equipment. In
the whole plant, there are about 83 transformer installed at various places to operate the
auxiliaries.
Main transformers which are necessary:
1. To step up the generated voltage.
2. To supply power to the auxiliaries from the generator.
3. To start the plant by taking the supply from the grid.
The main transformers installed in the transformer yard are:
a.) Generator Transformer (GT - 1)
It steps up the voltage from 10.5 KV to 220 KV. It connects the plant with the 220 KV
switch yard.
b.) Generator Transformer (GT-2)
switch yard.
c.) Generator Transformer (GT -3)
switch yard.
d.) Unit Auxiliary Transformer (UAT-1)
It is a step down transformer with 12/15 MVA capacity. It steps down the voltage from
11.5 KV to 6.9 KV.
e.) Unit Auxiliary Transformer (UAT-2)
It is a step down transformer with 12/15 MVA capacity. It steps down the voltage.
f.) Unit Service Transformer (UST)
It is a step down transformer with 2 MVA capacity. It is used to step down from 6.6 kV to
0.4333 KV. There are 6 No’s of UST.

7.6 Transformer
There are 3 generator transformers in the plant, one for each unit. The output from the
generator is fed to the generator transformer which steps up the voltage from 10.5 KV to
230 KV and supplies power to grid. Generator transformer winding connected in stardelta
with a phase displacement of 30 degrees. Three - phase supply from the generator is
connected to the low voltage side bushings and the output is taken from the opposite side.
Neutral point on the H.V. side is provided at the side of the tank. Neutral is solidly
grounded. In case neutral is solidly connected to the earth a very small current flowing
through the neutral causes the tripling of the transformer. So in this case more care is to be
taken.
Fig 7.5 Transformer Yard

7.7 The Main Parts of a Transformer
A.) Bushings
Porcelain bushings are provided on both sides of the tank from which L.V. and H. V.
winding is connected to the external circuit. These bushings insulate the winding terminals
from the body. Bushings are also filed with transformer oil, which helps in cooling as well
as insulation.
B.) Steel Tank
Whole of the transformer winding is immersed in the oil in the tank. The tank is airtight.
The tank should be strong enough to bear the pressure generated inside the tank without
bursting. To avoid bursting of the tank two pressure relief valves are provided on both
sides of the tank. In case pressure inside the tank exceeds 0.39 kg/cm2 these valves
operate. The diaphragm inside bursts and oil spills out thus tripling the generator.
C.) Cooling System
During the operation of the transformer, which raises the temperature of both the oil and
the winding? For proper operation the temperature should be kept within limits. To cool
the oil separate cooling system is provided. It consists of radiator, cooling fans and motor
pump. Hot oil number of radiating fins from the top. There are a large enters the radiating
fins from the top. There are a large number of radiating fins provided. When oil flows
through this radiator fins it cools down and again enters the main tank from the bottom.
The large number of fins increases the surface area thus increasing rate of heat dissipation.
In transformer there are three types of cooling systems:
i.) Oil Natural Air Natural (ONAN)
In this type cooling of oil is done by the natural flow of the oil. It is done when the load on
the transformer is below 160 MVA.
ii.) Oil Natural Air Forced (ONAF)
When the load on the transformer is between 160 MVA to 240 MVA, natural air striking
the fins is not able to cool down the oil properly due to increase in the heat generation. So
air is forced on the radiating fins. This is done by using the fans installed.

iii.) Oil Forced Air Forced (OFAF)
With further increase in load, more heat is generated which necessary forced cooling of oil
also. This is done by energizing the pumps placed in the bottom pump near the main tank.
These force the oil to flow which results in the cooling of the oil. G. T. is provided.
D.) Conservator Tank and Breather
The constant heating of oil there is a loss of oil due to evaporation and there is expansion
of oil, if some space is provided above the oil level in tank. As the tank is completely
sealed, so stresses will develop on the tank due to the expansion of oil. So a ventilating
system is provided which avoids stresses in the tank and helps in the proper expansion of
the oil. A conservator tank with a breather is provided on the top of the tank. Conservator
contains oil to some level and air cell.
During expansion of the oil level inside the conservator tank increases. Due to this air cell
contracts and air inside is pushed out. When the oil cools down, oil level decreases. Air
cell expands and sucks air inside. The atmospheric air contains moisture and if oil comes
in contact with this moist air its properties degrade. This is avoided by placing a drying
agent in the breather. Calcium chloride or silica gel in the breather absorbs the moisture
from air. Thus moisture less air enters the tank. In normal conditions the color of silica gel
is blue. When its color changes to pale pink, it should be replaced immediately.
E.) Buccholz Relay
It is the most important protective device for internal faults. It is a gas-activated relay.
During any fault inside the winding light gases like hydrogen are generated. The Buccholz
relay is connected on the pipe between the conservator and the main tank. These gases get
struck in the Buccholz relay and cause the level of oil in the relay to go down.
Due to this a mercury switch is operated which makes the contact and given a signal. In
the beginning only an alarm is there. But if the fault persists and becomes serious there is a
second mercury switch, which gets operated and trips the transformer. The various
readings for the alarm and trip signal are:
Alarm signal - 220 mm Hg
Trip signal - 500 mm Hg

F.) Tap Changer
Tap changers are provided in the transformer to get the desired output voltage by changing
the number of turns.
The tap changers are of two types
1. On load tap changer
2. Off load tap changer
1. On load tap changer
In this we can change the tapping of the transformer on load. The tap changer is generally
provided on the H.V. side as current on this side is very less. These are installed on S.T.
2. Off load tap changer
These are installed on GT. The tap is changed mechanically after disconnecting the
transformer from the circuit. To monitor the temperature of oil as well as winding two
temperature gauges are provided. In the gauge two capillary tubes are provided. One is
dipped in oil to measure its temperature and the second one is dipped near the winding.
7.8 Unit Auxiliary Transformer (UAT)
Each unit has two unit auxiliary transformers. When the unit starts generating electricity
these transformers are energized and then supplies power to the auxiliaries. Before starting
of the unit, UAT bus is connected to the station bus. Auxiliaries of all three units take
about 7 mw of power. UAT is connected between the generator and the GT. A tapping is
taken from the power coming from the generator to the GT. UAT relieves GT from extra
load of about 7 MW which is to be supplied to the auxiliaries via GT and ST thus
increasing the efficiency. It is a step down transformer, which steps down the voltage from
10.5 kV to 6.9kV. The rating of UAT is 12/15 MVA. UAT bus supplies only those
auxiliaries, which are not necessary to be energized in case of sudden tripping of
generator.
The H.V. side is provided at the side of the tank. Neutral is solidly grounded. In case
neutral is solidly connected to the earth a very small. Due to this air cell contracts and air
inside is pushed out. When the oil cools down, oil level decreases. Air cell expands and
sucks air inside. The atmospheric air contains moisture and if oil comes in contact with
this moist air its properties degrade.

Unit Auxiliary Transformer
Power 12/15 MVA
HV Voltage 10.5 KV
LV Voltage 6.9 KV
Transformer Percentage Imp 10 %
Transformer Vector Group Dyn11
Generator Transformer
Power: 90/120/160 MVA
HV Voltage 230 KV
LV Voltage 10.5KV
Transformer Percentage Imp 12.5 %
Transformer Vector Group Ynd11
Details of 220 KV C.B.
Voltage 245 KV
Normal Current 2000 Amp
Lightning Impulse Withstand Voltage 1050 KV
Short Circuit Breaking Current 40 KAmp
Short Time Withstand Current And Duration 40 Kamp, 3 Sec
Operating Sequence 0-0.3 Sec - Co-3, Min.-Co
Gas Pressure (SF6) 7.0 Bar
Closing and Opening Supply Voltage 220 V DC
Auxiliary Circuit Supply Voltage Iph.240 V AC, 415 V AC
Air Pressure 21.5 Bar
Frequency 50 Hz
Mass (Approx) 3800kg

Chapter 8
DC SYSTEM
8.1 Batteries
A.) Main Building
• Wet cell battery bank
125 V Battery Bank – 1
• Dry cell battery
Battery Bank
B.) Switchyard Building Battery Bank
8.2 Battery Room
Battery room should be well ventilated, clean, dry and temperature moderate
(Damping is dangerous due to possibility of earth leakage from the battery)
Smoking is prohibited
Battery get best result at the room temperature between 20 – 35o C

8.3 Electrolyte
It is a mixture of Acid and Pure Water (Distilled) with proper portion.
General value of proportion is 85 % water and 15 % acid.
Gravity to be maintained 1.200 + 0.005 in all the cells.
8.4 Caution
Batteries and Battery Room should be clean, dry and well ventilated.
Never allow a flame, cigarette near the batteries.
Wear old clothes or terylene when working with acid or electrolyte (Terylene is
resistant to dilute acid).
Never add water to acid. It will spurt dangerously
8.5 Temperature Correction
The specific gravity of the electrolyte works with temperature. Any reading
observed on the hydrometer should therefore be corrected to 270o C as all the
specific gravity values indicated by use are at 27o C.
For every 1o C above 27o C add 0.007 to the specific gravity as read on
hydrometer
8.6 Normal Operation of Batteries
Keep the battery on trickle charge continuously (25 hrs. each day) except
where it is on discharge or on Boost charge.
The trickle charge current shown on mili ammeter should be so adjusted that
the battery be kept fully charges without being over charged.
The trickle charging current should be so appropriate that it should neither be
too much trickle charge not too little trickle charge.
The value above 2.3 and below 2.25 volts per cell during routine checking it
found means adjustment of trickle charging current is required.

Chapter 9
TYPICAL DIAGRAM OF A COAL-FIRED IN THERMAL
POWER STATION
Fig 9.1 Typical diagram of thermal power plant

9.1 Typical Diagram of a Coal-Fired Thermal Power Station
1. Cooling tower
2. Transmission line (3- phase)
3. Step-up transformer (3-phase)
4. Electrical generator (3-phase)
5. Low pressure steam turbine
6. Condensate pump
7. Surface condenser
8. Intermediate pressure steam turbine
9. Steam control valve
10. High pressure steam turbine
11. Deaerator
12. Feed water heater
13. Coal conveyor
14. Coal hopper
15. Coal pulverizer
16. Boiler steam drum
17. Bottom ash hopper
18. Super heater
19. Forced draught
20. Re-heater
21. Combustion air intake
22. Economizer
23. Air pre-heater
24. Precipitator
25. Induced draught fan
26. Flue gas stack
27. Cooling water pump

9.1.1 Cooling Towers
Cooling tower is heat removal device used to transfer process waste heat to the
atmosphere. Cooling tower may either use the evaporation of water to remove process heat
and cool the working fluid to near the wet-bulb air temperature or rely solely on air to cool
the working fluid to near the dry-bulb air temperature.
9.1.2 Transmission Lines
Electric power transmission or high voltage electric transmission is the bulk transfer of
electric energy, from generating power plant to substation located near to population
centre. This is distinct from the local wiring b/w high voltage substation and customers,
which is typically referred to as electricity distribution.
9.1.3 Condensate Pump
A condensate pump is a specific type of pump used to pump the condensate produced in
an HVAC (heating or cooling), refrigeration, condensing boiler furnace or steam system.
They may be used to pump the condensate produced from latent vapour.
9.1.4 Surface Condensers
Surface condenser is the commonly used term for a water-cooled shell and tube heat
exchanger installed on the exhaust stream from a steam turbine in thermal power stations.
These condensers are heat exchangers which convert steam from its gaseous to its liquid
state at a pressure below atmospheric pressure. Where cooling water is in short supply, an
air-cooled condenser is often used. An air-cooled condenser is however significantly more
expensive and cannot achieve as low a steam turbine exhaust pressure as a surface.
9.1.5 Steam Turbine
A steam turbine is a mechanical device that extract from thermal energy from pressurized
steam, and converts it into rotary motion.
The turbine generate rotary motion, it is particularly suited to be used to drive an electrical
generator , about 80% of all electricity generation in the world is buy use of steam turbine.
The steam turbine is a form of heat engine that derives much of its improvement in
thermodynamic efficiency through the use of multiple stages in the expansion of the
steam, which result in a closer approach to the ideal reversible process.

Fig 9.2:- Steam turbine
9.1.6 Control Valve
Control valves are valve used to control condition such as flow, pressure, temperature, and
liquid level by fully or partially opening or closing in response to signals received from
controllers that compare a “set point” to a :process variable” whose value is provided by
sensors that monitor changes in such condition. The opening and closing of control valve
is done by means of electrical, hydraulic or pneumatic systems.
9.1.7 Deaerator
A Deaerator is a device that is widely used for the removal of air and other dissolved
gasses from the feed water to steam-generating boilers. In particular, dissolved oxygen in
boiler feed water will cause serious corrosion damage in steam system by attaching to the
wall of metal piping and other metallic equipment and forming oxides(rust). Water also
combines with any dissolved carbon dioxide to form carbonic acid that causes further
corrosion. Most deaerators are designed to remove oxygen down to levels of 7ppb by
weight (0.0005cm3/L) or less.
There are two basic types of deaerators, the tray-type and the spray-type:
The tray type includes a vertical domed deaeration section mounted on top of a
horizontal cylindrical vessel which serves as the deaerator boiler feed water storage
tank.
The spray type consists only of a horizontal (or vertical) cylindrical vessel which
serves as both the deaeration section and the boiler feed water storage tank.

9.1.8 Feed Water Heater
A feed water heater is a power plant component used to pre-heater water delivered to a
steam generating boiler. Preheating the feed water reduced the irreversibility’s involved in
steam generation and therefore improves the thermodynamic efficiency of the system.
This reduced 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.
Fig 9.3:- Feed water system
9.1.9 Coal Pulverizer
A pulveriser is a mechanical device for the grinding of many different types of materials.
For example, they are used to pulverize coal for combustion in the steam generating
furnaces of fossil fuel power plant.

9.1.10 Boiler Stream Drum
A steam drum is a standard feature of a water-tube boiler. It is a reservoir of water/steam
at the top hand of water tubes. The drum stores the steam generated in the water tubes and
acts as a phase separator for steam/water mixture. The difference in densities b/w hot and
cold water helps in the accumulation of the hotter water/and saturated steam into the
steam-drum.
9.1.11 Bottom Ash
Bottom ash refers to the non-combustible constituents of coal with traces of combustible
embedded in forming clinkers and sticking to hot side walls of a coal-burning furnace
during its operation. The portion of the ash that escapes up the chimney or stack are,
however referred to as fly ash .the clinkers fall by themselves into the water or something
by poking manually, and get cooled.
9.1.12 Super Heater
A super heater is a device used to convert saturated steam or wet steam into dry steam
used for power generation or process stream which has been super heated is logically
known as superheated steam, non-superheated steam is called saturated steam or wet
steam.
9.1.13 Economizer
Economizers are mechanical device 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. In simple term, an economizer is a heat exchanger.
9.1.14 Air Preheator
An air pre-heater (APH) is a general term to describe any device designed to heat air
before another process (for example, combustion in a boiler) with the primary objective of
increasing the thermal efficiency of the process. They may be alone or to replace a
recuperative heat system or to replace a steam coil.
In particular, this article describes the combustion air preheated used in large boiler found
in thermal power station.

9.1 15 ID and FD Fans
a.) Forced Draft Fan
A centrifugal fan is a mechanical device for moving air or gasses. It has a fan wheel
composed of a number of fan blades, or ribs, mounted around a hub. The hub turns on a
driveshaft that passes through the fan housing. The gas enters from the side of the fan
wheel, turns 90 degrees and accelerates due to centrifugal force as it flows over the fan
blades and exits the housing. FD fan is used to suck the air from atmosphere.
b.) Induced Draft Fan
This fan has the same working principle but is working is a little different from FD fan. It
is used to through the air/gas to the atmosphere.

CONCLUSION
The practical training has provided to be quite faithful. It provides an opportunity for
encounter with such huge components like turbine, generator, and DM plant system etc.
Hence we have analyzed how to power generate and are the basic building blocks of the
power generation project such as a compressor, combustion Chamber, Gas Turbine, Steam
Turbine and Turbo-Generator etc.
The architecture of the DHOLPUR CONBIND CYCLE POWER PLANT (DCCPP),
DHOLPUR the way various units are linked and the way of working of whole plant is
controlled make the student realizes that Engineering is not just the structured description
and working of various machine ,but the greater part is planning, proper management.
The training helped to get knowledge about various systems of power plant and their
working. Training gave us the practical knowledge which makes a solid foundation in our
mind. It enhances our technical skills.
How power is supplied to the transmission line. We have observed construction of Gas
Turbine, Steam Turbine and Turbo-Generator etc. Power generation are very efficient,
reliable, highly performance and give tremendous result. Power generation plants are very
economical.
There are the 8 plats working under THE RAJASTHAN RAJYA VIDYUT UTPADAN
NIGAM LTD. And present total installed capacity of THE RAJASTHAN RAJYA
VIDYUT UTPADAN NIGAM LTD. Is 4097.35 MW and the present capacity of
DHOLPUR CONBIND CYCLE POWER PLANT (DCCPP), DHOLPUR is 330 MW.
Some other power stations are given below-
1. SURAGARH THERMAL POWER PLANT
2. KOTA THERMAL POWER PLANT
3. CHHABRA SUPER THERMAL POWER STATION
4. RAMGARH GAS POWER PLANT
5. MAHI HYDEL
6. MMH SCHEMES GIRAL LIGNITE THERMAL POWER PLANT
7. NTPC ANTA (BARAN).

REFERANCE
Manual provided by DCCPP DHOLPUR contains brief description about the control
system, maintenance, technical data, protection device, fault tracing etc.
Other references are given below-
1. Some data analysis provided by DCCPP DHOLPUR.
2. Control system by I.G. NAGRATH.
3. Principles of Power System by V.K.MEHTA.
4. Electrical Machine by ASHFAQ HUSSAIN.
5. Power Electronics by P.S. BHIMBRA
6. Some topic arrange from Wikipedia, Google
a.) http://wikipedia.com
b.)http://www.google.com/m/search.
c.)http://www.koncarinem.hr.
d.)www.powermag.com.
e.)www.smartpowergeneration.com.
f.) http://www.analyrics.com.

Training Report DCCPP, Dholpur

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