DADRI GAS POWER PLANT REPORT gas power plant

1. B. Tech., Electrical Engineering NTPC Dadri
A
REPORT ON INDUSTRIAL TRAINING
Taken At
NTPC Dadri
(From 20/05/2019 to 18/06/2019)
Submitted in partial fulfillment of the requirements for the award of the Degree of
Bachelor of Technology
Poornima College of engineering, Jaipur
Session: 2019-20
Submitted By: Submitted To:
Banti Saini Prof.(Dr.) Babita Jain
(Faculty Coordinators- Practical Training
Seminar)
PCE16EE038
IV Year, EE
DEPARTMENT OF ELECTRICAL ENGINEERING POORNIMA
COLLEGE OF ENGINEERING, JAIPUR RAJASTHAN
TECHNICAL UNIVERSITY, KOTA
20-05-2019to18-06-19

2. P a g e | 0
DECLARATION
I hereby declare that the work which is being presented in the Practical Training & Industrial visit
report title Electrical Maintenace Department in partial fulfillment for the award of the Degree of
Bachelor of Engineering in Electrical Engineering and submitted to the Department of Electrical
Engineering, Poornima College ofEngineering, Jaipur, is an authentic record of my own work carried
out at NTPC DADRI , Vidyut Nagar, Dist. Gautambudhnagar, Uncha Amirpur, Uttar Pradesh
201008. during the session 2019-20 (Even Semester).
I have not submitted the matter presented in this report any where for the award of any other Degree.
Banti Saini
PCE16EE038
Place: Jaipur
Date:_________

3. 1
DEPARTMENT OF ELECTRICAL ENGINEERING
Date:
CERTIFICATE
This is to certify that Practical Training & Industrial visit report titled Electrical Maintance
Department has been submitted by Banti Saini reg. no PCE16EE038 in partial fulfillment for
the award of the Degree of Bachelor of Engineering in Electrical Engineering during the
session 2019-20, Even Semester. The Practical Training & Industrial visit work is found
satisfactory and approved for submission.
Dr. Babita Jain.
Assistant Professor/Associate Professor/Professor,
(Faculty Incharge - Industrial Training)
Date: ________
Place: Jaipur
Dr. Amit Shrivastava
Professor-EE
Coordinator-Industrial Training
Dr. Virendra Sangtani
HoD, EE

4. 2

5. 3

6. 4
ACKNOWLEDGEMENT
I have undergone an Industrial Training which was meticulously planned and
guided at every stage so that it became a life time experience for me. This could
not be realized without the help from numerous sources and people in the
Poornima college of engineering and Ntpc Dadri.
I am thankful to Ms. Dipti Lodha, T.P.O, Poornima college of engineering for
providing us a platform to carry out this activity successfully.I am also very
grateful to Dr. Virendra Sangtani(HOD), Electrical Engineering) for his kind
supportand guidance.
I would like to take this opportunity to show our gratitude towards Dr. Babita
jain. who helped me in successfulcompletion of my Industrial Training. She has
been a guide, motivator & source of inspiration for us to carry out the necessary
proceedings for completing this training and related activities successfully.
I am also privileged to have Mr.Gaurav Shrivastava (T.P.O Department OfElectrical)
Who have flourished us with their valuable facilities without which this work
cannot be completed.
I would also like to express my heart felt appreciation to all of my friends whom
direct or indirect suggestions help me to develop this project and to entire team
members for their valuable suggestions.
Lastly, thanks to all faculty members of Department of Electrical engineering for
their moral supportand guidance.
Banti Saini

7. 5
INDUSTRIAL TRAINING
REPORT
ON
‘ NTPC DADRI’
GAS POWER PLANT
National Thermal Power Corporation Limited
National Capital Power Station - Dadri
P.O. Vidyut Nagar, District Gautam Budh Nagar - 201 008
(UP)
“NTPC was set up in the central sector in the 1975.Only
PSU to achieve excellent rating in respect of MOU targets
signed with Govt. of India each year. NTPC Dadri station
has also bagged ISO 14001 certification.
Today NTPC contributes more than 3 / 5th of the total
power generation in India.”

8. 6
CONTENTS
S.NO. DESCRIPTION PAGE NO.
(1) OVERVIEW OF NTPC 7
(2) SATION AT A GLANCE 8
(3) INTRODUCTION TO GAS
POWER PLANT
9
(4) GAS TURBINE STARTING
SYSTEM
20
(5) FUEL SYSTEM 23
(6) SALIENT FEATURES OF NTPC
DADRI
28
(7) GAS PLANT OPERATION 29
(8) HOW DOES A COMBINED-
CYCLE POWER PLANT WORK?
33
(9) AUTOMATION AND CONTROL 48

9. 7
(i) Overview of NTPC
NTPC was set up in the central sector in the 1975 in response to
widening demand & supply gap with the main objective of
planning, promoting & organizing an integrated development to
thermal power in India. Ever since its inception, NTPC has never
looked back and the corporation is treading steps of success one
after the other. The only PSU to have achieved excellent rating in

10. 8
respect of MOU targets signed with Govt. of India each year.
NTPC is poised to become a 40,000 MW gint corporation by the
end of XI plan i.e. 2012 AD. Lighting up one fourth of the nation,
NTPC has an installed capacity of 19,291 MW from its
commitment to provide quality power; all the operating stations of
NTPC located in the National Capital Region & western have
acquired ISO 9002 certification. The service groups like
Engineering, Contracts, materials and operation Services have
also bagged the ISO 9001 certification. NTPC Dadri,
Ramagundam, Vindhyachal and Korba station have also bagged
ISO 14001 certification.
Today NTPC contributes more than 3 / 5th
of the total power
generation in India.
(ii) Station At Glance
NTPC dadri is model project of NTPC . also it tit the best project
of NTPC also known as NCPS ( National capital power station ).
Situated 60 kms away from Delhi in the District of gautam budh
Nagar, Uttar Pradesh. The station has an installed capacity of
1669 MW of power – 840 MW from Coal based units and 829
MW Gas Based Station . the station is excelling in performance
ever since it’s commercial operation . consistently in receipts of

11. 9
meritorious projectivity awards, the coal based units of the station
stood first in the country in terms of PLF for the financial year
1999 – 2000 by generating an all time national high PLF of 96.12
% with the most modern O & M Practices. NTPC – Dadri is
committed to generated clean and green Power. The Station also
houses the first HVDC station of the country (GEP project) in
association with centre for power efficiency and Environment
protection (CENEEP) – NTPC & USAUID. The station has
bagged ISO 14001 & ISO 9002 certification during the financial
year 1999 – 2000, certified by Agency of International repute M/s
DNV Netherlands M/s DNV Germany respectively
1.Introduction To Gas Power
Plants
Introduction
The development of the sector in the country, since
independence has been predominantly through the State
Electricity Boards. In order to supplement the
effects of the states in accelerating power development and to
promote power development on a regional basis to enable the
optimum utilisation of energy resources, the Government of

12. 10
India decided to take up a programme of establishment of
large hydro and thermal power stations in the central sec tor
on a regional basis. With this in view, the Government set up
the National Thermal Power Corporation Ltd., in November
1975 with the objective of planning, construction,
commissioning, operation and maintenance of Super Thermal
and Gas Based Power projects in the country.
The availability of gas in a large quantity in western offshore
region has opened an opportunity to use the gas for power
generation, which is an economical way and quicker method
of augmenting power generating capacity by natural gas as
fuel in combined cycle power plant in a power deficit country
like ours. With this intention in mind the Government asked
NTPC to take up the construction of Kawas, Auraiya, Anta,
Dadri and Gandhar Gas Power Project along the HBJ Gas
pipe line.
The power plant consists of gas turbine generating units
waste heat recovery boilers, steam turbo generator, ancillary
electrical and mechanical equipments. The power generated
at this power station is fed over 220 KV AC transmission
system associated with this project to distribute the power in
the various Regions.
In the Power Sector, gas turbine drive generators are used.
Gas turbines range in size from less than 100 KW up to about
140.000 KW. The gas turbine has found increasing application
due to the following potential advantages over competive

13. 11
equipment.
• Small size and weight per horsepower
• Rapid loading capability
• Self-contained packaged unit
• Moderate first cost
• No cooling water required
• Easy maintenance
• High reliability
• Waste heat available for combined cycle application.
• Low Gestation Period
• Low Pollution Hazards
The function of a gas turbine in a combined cycle power plant is
to drive a generator which produce electricity and to provide
input heat for the steam cycle. Power for driving the compressor
is also derived from gas turbine.
Combined Cycle
Combined Cycle power plant integrates two power conversion
cycles namely. Brayton Cycle (Gas Turbines) and Rankin
Cycle (Conventional steam power plant) with the principal
objective of increasing overall plant efficiency.
Brayton Cycle

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Gas Turbine plant-operate on Brayton Cycle in which air is
compressed this compressed air is heated in the combustor by
burning fuel combustion produced is allowed to expand In the
Turbine and the turbine is coupled with the generator.
Without losses the theoretical cycle process is represented by 1’
2’ 3’ 4’
In the actual process losses do occur. Deviation from the
theoretical process, results from the fact that compression and
expansion are not performed
isentropically but polytropically which is conditioned by heat
dissipation (expansion) and heat supply (Compression) caused
by various flow and fraction by losses.
In the combined cycle mode, the Brayton Cycle is chosen as the
topping cycle due to the high temperature of the exhaust of the
gas turbine (point 4 in the P.V diagram). In modern gas turbines
the temperature of the exhaust gas is in the
range of 500 to 550 0
C.
Reference to the T.S. diagram may indicate the amount of heat
that is produced, converted into mechanical energy and extracted
from this process. For the evaluation of the cyclic process, two
parameters are of greatest importance;
1) Thermal efficiency 2) Process working capacity
Thermal efficiency is obtained from chemical binding energy of
the fuel and mechanical energy available at the shaft of the gas
turbine.

15. 13
Thermal efficiency ( th ) as follows:
th = Energy at GT shaft
Chemical Energy of fuel
= (Q Input. Q output )/ Q Input
= 1 — Q Output/ Q Input
Working capacity is also obtained from the difference between
the amounts of heat supplied and removed. This is achieved by
increasing P2 that is increasing gas inlet temperature T3.

16. 14
Fig.1
Rankine Cycle
The conversion of heat energy to mechanical energy with the aid
of steam is carried out through this cycle. In its simplest form the
cycle works as follows (fig.2).
The initial state of the working fluid is water (point-3) which, at
a certain
temperature is compressed by a pump (process 3-4) and fed to
the boiler. In the boiler the compressed water is heated at
constant pressure (process 4-5-6-1). Modern steam power plants
have steam temperature in the range of 500 0
C to 550 0
C at the
inlet of the turbine.

17. 15
Fig.2
Combining two Cycles to Improve
Efficiency
We have seen in the above two cycles that gas turbine exhaust is
at a
temperature of 500–550 0
C and in Rankine Cycle heat is
required to generate steam at the temperature of 500-550 0
C. so,
why not use the gas-turbine exhaust to generate steam in the

18. 16
Rankine cycle and save the fuel required to heat the water ?
Combined Cycle does just the same.
The efficiency of Gas Turbine cycle alone is 30% and the
efficiency of Rankine Cycle is 35%. The overall efficiency of
combined cycle comes to 48%.
Types of Combined Cycles
It is basically of two types, namely Unfired Combined cycle and
Fully Fired combined cycle.
Unfired combined Cycle
The basic system is shown in figure- 3. in this system the
exhaust gas is used only for raising steam to be fed to the steam
turbine for power generation.
The conventional fossil fuel fired boiler of the steam power plant
is replaced with a ‘Heat Recovery Steam Generator’ (HRSG).
Exhaust gas from the gas turbine is led to the HRSG where heat
of exhaust gas is utilised to produce steam at desired parameters
as required by the steam turbine.
However, non-reheat steam turbine is the preferred choice for
adopting this type of system as usually the live steam
temperature for HRSG will be solely controlled by the gas
turbine exhaust temperature which is usually around 500 0
C.

19. 17
UNFIRED COMBINED CYCLE
FIG-3
In recent development, with the introduction of Dual Pressure
Cycles more heat is recovered in the HRSG and steam with
higher pressure and temperature can be generated. But higher
capital investment and sometimes necessity of supplemental
firing system makes the system complex and costly.
Fully Fired Combined Cycle
Fig – 4 shows the basic schematic of this cycle. In this system
the heat of
exhaust gas from gas turbine is used for two purposes as
described below:
Heat contained in exhaust gas is used to heat feed water to a
desire

20. 18
BOILER REPOWERING SYSTEM EXHAUST HEAT
EXCHANGER
Fig. 4
temperature at the inlet to the boiler. This leads to the reduction
or elimination of the extraction steam requirement from the
steam turbine. In case, the steam turbine has a larger steam
swallowing capacity to generate more power the amount of
steam which is being extracted from steam turbine for
regenerative feed heating could be made to expand in the turbine
to increase its base load capacity and improve the overall
efficiency. In case the steam turbine does not have the capacity
to swallow extra steam available due to cutting down of
extraction, the fuel being fired in the boiler can be cut down to
generate less steam by an amount equivalent to steam required

21. 19
for extractions and thus improving the overall efficiency due to
less consumption of fuel.
Gas turbine exhaust contains about 14 to 16 % oxygen (by
weight) and can be used as hot secondary air in the conventional
fossil fired furnaces. So the heat required to heat the secondary
air will be saved and can be used for other purposes. FD fan
power consumption will also be reduced to a great extent.
Fuels
Gas turbines are capable of burning a range of fuels including
naptha, distillates, crude oils and natural gas. Selection of fuel (s)
depends on several factors including fuel availability, fuel cost
and cleanliness of fuel.
Natural gas is an ideal fuel because it provides high thermal
efficiency and reliability with a low operation and maintenance
cost. Liquid fuels, particularly heavy oils, usually contain
contaminants, which cause corrosion and fouling in the gas
turbine. Contaminants, which cannot be removed from the fuel,
may leave deposits in the gas turbine, which reduce performance
and add maintenance costs.
Dual fuel systems are commonly used, enabling the gas turbine
to burn back-up fuels when the primary fuel source is not
available. Dual fuel systems can also be designed to fire both

22. 20
fuels simultaneously.
Advantages of Combined Cycle Plants
Apart from the higher overall efficiency, the combined cycle
power plants have following advantages:
Low installation Cost: power from a combined cycle power plant
is approximately 70% of a conventional coal based power plant
of same capacity.
Low Gestation Period: Power from a combined cycle power
plant can be
obtained in two phases, i.e. two third power, obtainable from gas
turbines, is available within 16-18 months and the balance in
next 1 month. This is much lower than the gestation period for
conventional thermal power plants, which is around 48-60
months.
Better Reliability: Combined cycle power plants are considered
to be highly reliable with the reliability factor of 85-90% as
compared to 60-65% for conventional coal Fired Power Plants.

23. 21
2. Gas Turbine Starting System
The function of the starting system is to crank the gas turbine
upto the required speed until : it becomes self sustaining.
One method of starting large gas turbine is by using a motor
driven hydraulic starting system. Alternatively, the GTG can be
started by using a frequency converter to rotate the generator
which drives the turbine for starting.
A typical hydraulic starting system for each gas turbine consist
of the following:
• Starting motor, electric AC induction motor
• Hydraulic torque converter
• Auxiliary Gear
• Couplings
The electric starting motor drives the hydraulic torque generator
through a coupling. The hydraulic torque converter consists of an
impeller, which forces the fluid against hydraulic starting motor.
The hydraulic torque converter is coupled to the accessory gear,
which is connected to the gas turbine shaft. The torque converter
receives hy draulic fluid from hydraulic and lube oil reservoir
during
operation. When gas turbine reaches self-sustaining speed the

24. 22
starting device is disconnected and shut down. To break the
inertia of the starting motor and reduce the starting current a
pony motor is provided. Gas turbines of GE and WH designs are
provided with starting motor system for cranking purpose.
The static frequency converter serves the same function of
starting, accelerating running at preset speed by starting the
generator as a synchronous motor by feeding variable frequency
current drawn from the connected grid. Gas turbines of ABB and
SIEMENS make are provided with frequency converter s for the
GT cranking and normally 2 * 100% static converters are
provided for the power station.
Black Start System
To start a gas turbine in the event of AC-power failure an
emergency black start system is provided. It also helps in safe
coasting down of the gas turbine and its auxiliaries following a
‘trip’ in the event of grid collapse. The black start system consist
of a separate diesel engine or a gas turbine driven synchronous
generator connected to station switch gear bus. It can be
operated manually from local or remote and also it
automatically comes into operation following a black out
condition. Capacity of the black start unit should be such that it
can supply the total auxiliary power required to start a gas
turbine from standstill condition.
The NTPC’s Auraiya project gas turbine is provided for

25. 23
emergency black-start purpose and all other projects are
provided with diesel generator set for the same duty.
3. Fuel System
Fuel System of Gas Turbine
The function of the fuel system is to deliver fuel to the
combustion chamber(s) of a gas turbine at quantity and pressure
as required by the control system
Liquid fuel system
The liquid fuel system consists of the liquid fuel storage and
handling system. The liquid fuel storage and handling system
provides means for unloading , storage and distribution of the
fuel oil within the plant and typically composed of the following
major components:
• Fuel oil unloading pumps
• Fuel oil transfer pumps
• Fuel oil storage tanks
• Flow meter
• Strainers
• Pressure and Level control stations.
• Distribution piping

26. 24
The number and size of equipments is site dependant. The
storage facility is dependant on such factors as the location of the
site, proximity of the oil supply and the reliability of the oil
supply. Fuel oil may be supplied to the plant by a pipeline, oil
barriages, oil tankers, rail/road or high way trucks. Fuel oil
unloading pumps may not be required if the oil arrives by a
pipeline, an oil barge, or an oil tanker since they have their own
pumps.
Naphtha Pressurising System
By the forwarding pumps,Naptha is pumped upto the GTs and
kept under recirculation. For firing the naphtha is the
GT,separate pressurising system with high pressure pump, allied
filters and m easurements and recirculation system is used. This
pressurising is required because in the naphtha burner this fuel is
mechanically atomised. There is no other medium like air, etc
are used for atomisation.
Naphtha drain system
Since the flash/fire point of this fuel is very low it is designed to
drain the oil from the piping burner etc when the system is
stopped. Separate drain tanks are kept at pumping stations,
which will collect these naphtha and pump back to the main
storage tanks.
Mode of firing

27. 25
It is provided to fire natural gas or naphtha or in mixed mode of
the fuel in the GT Combustion Chamber.
FUEL GAS SYSTEM
The purpose of the fuel gas system is to take gas fuel from the
custody transfer point, process it to the quality and pressure
conditions required by the gas turbine and to distribute it and
monitor its use. Fuel gas system consists of the off base system
and the on base system.
Off base fuel gas System
The off-base fuel gas system is typically composed of the
following major components:
• An emergency stop valve at the gas inlet to the plant knock
out drum
• Filters
• Pressure-control station
• Distribution piping
Optional Components are
• Gas metering station
• Gas Heaters
The need for any of the optional components is dictated by the
conditions

28. 26
specific to each individual application. The final supply pressure
required at gas turbine is a function of the gas turbine
compression ratio and the control valve and nozzle pressure
drops. Large gas turbines typically require a gas supply pressure
of about Kg/cm2 with pressure regulated with in +10 percent
off-set point.
The emergency stop valve at the in let to the station is provided
to completely shut off the gas supply in an emergency. The gas
fuel then goes through a knockout drum. A knock out drum will
remove the free liquid and some solids from the gas stream.
However, it will not separate out much of the entrained liquids.
The liquids separation from gas stream takes place by decreasing
the gas veloc ity in its transit through the drum. Impurities
collect at the drum bottom and are periodically automatically
purged A level controller opens a drain valve which allows the
waste to Adrian tank vented to the atmosphere. The filter
separators must have minimum of two stages of separation. The
initial stage being utilised removal of large liquid droplets
and the final stage for mist separation. Any solid particles
carried with the gas stream are separated in the first stage . The
first stage elements consist of hollow tubes of glass fibers
through which gas flows radially from outside. The separation
of carried solids and liquid particles is by interception, diffusion
and/or inertial impaction of the droplets on the fibers. The liquid
droplets coalesced on the surface drain on to the shell and from
there to the drain pot. The second stage mist separator is
preferably of the vans type in which liquid separation takes place
by subjecting the gas path to multiple changes of direction.
The gas analysis is carefully checked from the stand point these

29. 27
point of hydrate formation or icing at the pressure reducing
station under the worst ambient temperatures prevalent at each
site. If there is any tendency for the above, a suitably, rated gas
fired indirect heater is provided ahead of the pressure reducing
station. The gas heater ensures a gas temperature sufficiently
high such that the after pressure reduction the gas temperature is
at least 20” C higher than hydrate forming temperature or the gas
dew point whichever is higher. The heater normally utilises
natural gas for firing. Heat from the fire tube
be utilised to heat a water bath in which the U tubes for carrying
the gases to be heated are immersed. The control system ensures
constant temperature of the outlet gas for gas flows ranging from
zero to full gas flow. A full capacity bypass is provided so as to
enable operation of the fuel gas system is designed to deliver gas
fuel to the gas turbine combustion chamber(s) at the proper
pressure and flow rates to meet all the starting, acceleration and
loading requirements of
gas turbine operation.
Naphtha forwarding system
The forwarding system is mainly remote controlled from the GT
LCR and CCR. Although there is a possibility to control the
main devices locally by a switching the selector switch on local
position in the local panel.
By means of three way valves a tank selection is possible. To
ensure the standby position of the lines keep the value open. The
pumps are protected by the automatic recirculating valves. The

30. 28
condition of the strainers as well as of the filters is monitored by
the differential pressure indicators and switches. The safety
valves protect the line against the line against over pressure.
4. Salient Features Of NTPC DADRI
Gas Project
DADRI GBCCPP-STAGE I (817MW)
General Layout Plan
In the main plant block two modules, each consisting of
two GTGs placed on each side of 2 STGs. The central
control room is located towards west of the ST hall. The
transformer yard Is on the wester side of the turbine hall,
with switchyard further down west.
Induced draft cooling towers have been located
considering the proper flow of cooling water. Nearer to
main power house & convenient routing of open return
channel to CW pump house. The 220/400 KV
switchyard has been located in front of the power station.

31. 29
The 220 KV switchyard control room is accommodated
in the central control room itself. Space has been kept
for liquid oil installation and oil unloading facilities.
The GAIL terminal for receiving gas is located within
boundary of plant site.
5. Gas Plant Operation
Gas Turbine, WHRB, Steam Turbine
Starting Modes
Basic conditions for plant operation are as follows:-
• Start up or shut down of G/T, WHRB and S/T of each
module is performed separately from the other module
(except for S/T gland steam back-up and heating steam
back up systems).
• Start up/shut down mode is selected freely form among
those mentioned.
The start up/shut down procedure for WHRB and S/T
here mainly describes operating procedure for G/T by-

32. 30
pass damper, WHRB inlet damper and remote operated
valve necessary for start up and shut down from G/T
exhaust gas admission to WHR till rated load operation
of S/T. For detail operating procedure for G/T WHRB,
S/T auxiliaries and remote operated valve following
procedures are followed.
Start up Mode
The start up mode of G/T, S/T and WHRB shall be
selected from among the following as a rule through
various other start up modes are conceivable according
to power demand and operating principle.
Outline of each start up
• Normal start up mode
This mode is two unit (2G/T’s + 2WHRB’s +1 S/T)
combined cycle start up mode which, after starting up
one each of G/T and WHRB, starts up the other G/T
and WHRB and brings the output of G/T and S/T the
target output of the module. In this mode, S/T is
loaded with one each of G/T and WHRB in operation,

33. 31
and after the initial load is achieved, the pressure
control of HP/LP by-pass valves of both WHRB’S is
changed to common pressure control and then S/T is
loaded up.
The timing of starting up the other G/T and WHRB is
left to the discretion of the operator, and S/T is kept
stand by at the initial load until the pressure control of
both WHRB’S is changed to the common pressure
control.
• Rapid start up mode
This is a mode of starting up both G/T’s and WHRB’S
at the same time, changing the pressure control of
HP/LP by-pass valves of both WHRB’S to the
common pressure control, then loading up and brining
G/T the output of and S/T to the target output of the
module is achieved.
This mode is used only for start up after right stop or
hot start up (with vacuum).
In other start up modes; in which the time from G/T
start up to S/T loading is long, simultaneous startup is
not made to reduce heat lose at start up.

34. 32
• G/T/WHRB additionally start up mode
This is a mode of starting up the other G/T and WHRB
one until combined cycle of G/T, WHRB and S/T is in
operation. In this mode, the HP Steam pressure and
temperature of the other G/T and WHRB are raised up
those of G/T and WHRB in operation, and then the
pressure control of HP/LP by-pass valves is changed to
the common pressure control, and S/T is loaded up.
• Single G/T/WHRB start up mode
This is a combined cycle start up mode of starting up S/T
with only one each of G/T and WHRB in operation. The
other G/T and WHRB remain stopped.
• Individual pressure control
Individual pressure control means pressure control made
automatically by using HP/LP by-pass valves of both
WHRB’s and detecting pressure before HP/LPCV so
that HP/LP steam pressure of both WHRB’S will be the
same and constant respectively.

35. 33
• Loading of S/T
S/T loading rate after HP/LP by-pass are fully closed and
HP/LPCV are fully opened is determined by the load
change rate of G/T, namely S/T load change rate
increases as G/T load change rate increase. (Except for
G/T/WHRB additionally start up mode). S/T unloading
rate too is determined by G/T load change rate under
HP/LP by-pass valves are fully closed and HP/LPCV are
fully opened.
6.How Does A Combined-Cycle
Power Plant Work?
Power Generation:
Air Inlet
 The amount of air needed for combustion is
800,000 cubic feet per minute. This air is drawn

36. 34
though the large air inlet section where it is
cleaned, cooled and controlled, in order to
reduce noise.
Turbine-Generators:
 The air then enters the gas turbine where it is
compressed, mixed with natural gas and ignited,
which causes it to expand. The pressure created
from the expansion spins the turbine blades,
which are attached to a shaft and a generator,
creating electricity.
 Each gas turbine produces 185 megawatts (MW)
of electricity.
 The blades are attached to a rotor, which spins
the generator, and makes electricity. Think of a

37. 35
generator as a huge spinning magnet inside a
coil of wire. As the magnet spins, electricity is
created in the wire loops.
Heat Recovery Steam Generator (HRSG)

38. 36
 The hot exhaust gas exits the turbine at about
1100 degrees Fahrenheit and then passes
through the Nooter Erickson, Heat Recovery
Steam Generator (HRSG).
 In the HRSG, there are 18 layers of 100-foot tall
tube bundles, filled with high purity water. The
hot exhaust gas coming from the turbines passes
through these tube bundles, which act like a
radiator, boiling the water inside the tubes, and
turning that water into steam. The gas then exits
the power plant through the exhaust stack at a
much cooler 180 degrees, after having given up
most of its heat to the steam process.
 About 1 million pounds of steam per hour is
generated in this way and sent over to the steam
turbine through overhead piping.

39. 37
Steam Turbine
 The steam turbine is a Siemens Westinghouse
KN Turbine Generator, capable of producing up
to 240 MW. It is located on top of the
condenser, across from the cooling tower.
 Steam enters the turbine with temperatures as
high as 1000 degrees Fahrenheit and pressure as
strong as 2,200 pounds per square inch. The
pressure of the steam is used to spin turbine
blades that are attached to a rotor and a
generator, producing additional electricity, about
100 megawatts per HRSG unit.
 After the steam is spent in the turbine process,
the residual steam leaves the turbine at low
pressure and low heat, about 100 degrees. This

40. 38
exhaust steam passes into a condenser, to be
turned back into water.
 By using this “combined-cycle” process, two gas
turbines and one steam turbine, we can produce
a total of about 600 megawatts of electricity.
Emissions Control
Selective Catalytic Reduction (SCR)
 To control the emissions in the exhaust gas so
that it remains within permitted levels as it
enters the atmosphere, the exhaust gas passes
though two catalysts located in the HRSG.
 One catalyst controls Carbon Monoxide (CO)
emissions and the other catalyst controls Oxides
of Nitrogen, (NOx) emissions.

41. 39
Aqueous Ammonia
 In addition to the SCR, Aqueous Ammonia (a
mixture of 22% ammonia and 78% water) is
injected into system to even further reduce levels
of NOx.
Best Available Control Technology (BACT)
 Our annual average concentration of NOx is only
2 parts per million, which is considered the “best
available control technology” or BACT by the
Air Board.
 As exhaust gas passes out of the exhaust stack, it
is continuously sampled and analyzed, assuring
that permit limits are being met.
 With this kind of clean, modern technology, the
exhaust stack is only 145 feet high, compared to
500 feet, the height required by older power

42. 40
plants that use less efficient emission
technology.
 Environmental and health organizations
recognize this technology as a benefit to the
community. The local chapters of the American
Lung Association and Sierra Club both support
the Metcalf Energy Center.
Transmission of Generated Power Onto the
Grid
Transformers
 The Gas Turbine and Steam Turbine generators
produce power at 13,000 volts.
 The transformers take the generated 13,000 volts
and “transform” them to 230,000 volts, which is

43. 41
the required voltage needed for transmission to
the nearby tower that sends power to the
substation.
 A small amount of generation is directed to
“Auxiliary transformers” which “transform” the
generated voltage to a lower voltage, so it may
be used by the plant to power our own pumps,
fans, and motors. The Metcalf Energy Center
requires 12 – 15 megawatts to operate.
Switchyard
 From each transformer, the power passes
underground into our switchyard. The power
from all of the generators comes together there,
where it is measured, metered and directed onto
the grid.
 The proximity of the site to a large, existing
PG&E substation makes it a good place to build

44. 42
a power plant and the nearest transmission tower
is only about 200 feet away.
Condenser and Cooling Tower
 The purpose of the condenser is to turn low
energy steam back into pure water for use in the
Heat Recovery Steam Generator.
 The purpose of the cooling tower is to cool the
circulating water that passes through the
condenser. It consists of ten cells with large fans
on top, inside the cone-like stacks, and a basin of
water underneath.
 We process and treat the Title 22 recycled water
after receiving it from the City, before using it in
our cooling tower. The cool basin water absorbs
all of the heat from the residual steam after

45. 43
being exhausted from the steam turbine and it is
then piped back to the top of the cooling tower.
 As the cool water drops into the basin, hot wet
air goes out of the stacks. Normally, hot moist
air mixes with cooler dry air, and typically a
water vapor plume can be formed, one that may
travel hundreds of feet in the air and be seen
from miles away. The California Energy
Commission considered this visually undesirable
in this community so we added a “Plume-
Abatement” feature, louvers along the topsides
of the tower that control the air flow.
 The cooling tower evaporates about three-fourth
of the processed, recycled water, then we send
about one-fourth of it back through the sewer
lines for re-treatment by the City.

46. 44
 The Metcalf Energy Center purchases 3 to 4
million gallons per day of recycled water from
the City of San Jose. Evaporation of this water
assists the City in adhering to their flow cap
limits and helps to protect the sensitive saltwater
marsh habitat of the San Francisco Bay
environment from receiving too much fresh,
recycled water.
Water Tanks, Natural Gas Pipeline, Control
Room
Water Tanks
 The largest tank is the Service Water tank. It
contains 470,000 gallons of water to be used for
drinking, fire fighting and for the high purity

47. 45
water train. The water from the service water
tank is pumped to the water treatment building
where it then passes through a reverse osmosis
unit, a membrane decarbonater, and mixed resin
bed demineralizers to produce up to 400 gallons
per minute of ultra pure water.
 The pure water is then stored in the smaller
365,000-gallon tank until it is turned into steam
for making electricity.
Natural Gas
 Natural gas fuels the combustion turbines. Each
turbine can consume up to 2,000 MMBTU per
hour.
 The fuel comes from the major high pressure
natural gas pipeline that runs along the east side

48. 46
of Highway 101, less than 1 mile to the east of
our site.
 During construction, “Horizontal Directional
Drilling” was utilized with careful coordination
with many local authorities. The pipeline was
built 60 feet underground and passed under
highways, creek, train tracks, and
environmentally sensitive areas.
 The pipeline enters the site just behind the water
tanks, where equipment regulates and measures
the natural gas composition, flow and pressure.
 Gas compressors pump the natural gas though
the facilities’ fuel gas system where it is
delivered to the gas turbine and the HRSG duct
burners at the proper temperature, pressure and
purity.

49. 47
Control Room
 From the control room, the plant operators
monitor and operate the facility, via the plant’s
“Distributed Control System”, with the click of a
mouse, viewing graphic representations of all
MEC systems on various screens.
 The system gives operators both audible and
visual signals to keep them informed of plant
conditions at all times and to determine when
preventative maintenance is required.

50. 48
7.AUTOMATION AND CONTROL
SYSTEM
AUTOMATION: THE DEFINITION
The word automation is widely used today in
relation to various types of applications, such as
office automation, plant or process automation.
This subsection presents the application of a control
system for the automation of a process / plant, such
as a power station. In this last application, the
automation actively controls the plant during the
three main phases of operation: plant start-up, power
generation in stable or put During plant start-up and
shut-down, sequence controllers as well as long

51. 49
range modulating controllers in or out of operation
every piece of the plant, at the correct time and in
coordinated modes, taking into account safety as
well as overstressing limits.
During stable generation of power, the modulating
portion of the automation system keeps the actual
generated power value within the limits of the
desired load demand.
During major load changes, the automation system
automatically redefines new set points and switches
ON or OFF process pieces, to automatically bring
the individual processes in an optimally coordinated
way to the new desired load demand. This load
transfer is executed according to pre- programmed

52. 50
adaptively controlled load gradients and in a safe
way.
AUTOMATION: THE BENEFITS
The main benefits of plant automation are to
increase overall plant availability and efficiency.
The increase of these two factors is achieved through
a series of features summarized as follows:
Optimisation of house load consumption
during plant start- up, shut-down and operation,
via:
 Faster plant start-up through elimination of
control errors creating delays.
 Faster sequence of control actions compared
to manual ones. Figures 1 shows the sequence

53. 51
of a rapid restart using automation for a
typical coal-fired station. Even a well- trained
operator crew would probably not be able to
bring the plant to full load in the same time
without considerable risks.
 Co-ordination of house load to the generated
power output.
Ensure and maintain plant operation, even in
case of disturbances in the control system, via:
 Coordinated ON / OFF and modulating
control switchover capability from a sub
process to a redundant one.
 Prevent sub-process and process tripping chain
reaction following a process component trip.
Reduce plant / process shutdown time for
repair and maintenance as well as repair costs,
via:

54. 52
 Protection of individual process components
against overstress (in a stable or unstable plant
operation).
 Bringing processes in a safe stage of
operation, where process components are
protected against overstress
PROCESS STRUCTURE
Analysis of processes in Power Stations and Industry
advocates the advisability of dividing the complex
overall process into individual sub-processes having
distinctly defined functions. This division of the
process in clearly defined groups, termed as
FUNCTIONAL GROUPS, results in a hierarchical
process structure. While the hierarchical structure is

55. 53
governed in the horizontal direction by the number
of drives (motorised valves, fans, dampers, pumps,
etc.) in other words the size of the process; in the
vertical direction, there is a distinction made
between three fundamental levels, these being the: -
Drive Level
Function Group Level
Unit Level.
To the Drive Level, the lowest level, belong the
individual process equipment and associated
electrical drives.
The Function Group is that part of the process that
fulfils a particular defined task e.g., Induced Draft
Control, Feed Water Control, Blooming Mill

56. 54
Control, etc. Thus at the time of planning it is
necessary to identify each function group in a clear
manner by assigning it to a particular process
activity. Each function group contains a combination
of its associated individual equipment drives. The
drive levels are subordinate to this level. The
function groups are combined to obtain the overall
process control function at the Unit Level.
The above three levels are defined with regard to the
process and not from the control point of view.
CONTROL SYSTEM STRUCTURE

57. 55
The primary requirement to be fulfilled by any
control system architecture is that it be capable of
being organized and implemented on true process-
oriented lines. In other words, the control system
structure should map on to the hierarchy process
structure.
BHEL’s PROCONTROL P®
, a microprocessor
based intelligent remote multiplexing system, meets
this requirement completely.
SYSTEM OVERVIEW

58. 56
The control and automation system used here is a
micro based intelligent multiplexing system This
system, designed on a modular basis, allows to
tighten the scope of control hardware to the
particular control strategy and operating
requirements of the process
Regardless of the type and extent of process to
control provides system uniformity and integrity for:
Signal conditioning and transmission
Modulating controls
CONTROL AND MONITORING MECHANISMS

59. 57
There are basically two types of Problems faced in
a Power Plant
 Metallurgical
 Mechanical
Mechanical Problemcan be related to Turbines that
is the max speed permissible for a turbine is 3000
rpm , so speed should be monitored and maintained
at that level
Metallurgical Problem can be view as the max Inlet
Temperature for Turbile is 1060 o
C so temperature
should be below the limit.
Monitoring of all the parameters is necessary for the
safety of both:
 Employees
 Machines

60. 58
So the Parameters to be monitored are :
 Speed
 Temperature
 Current
 Voltage
 Pressure
 Eccentricity
 Flow of Gases
 Vaccum Pressure
 Valves
 Level
 Vibration
PRESSURE MONITORING

61. 59
Pressure can be monitored by three types of basic
mechanisms
 Switches
 Gauges
 Transmitter type
For gauges we use Bourden tubes : The Bourdon
Tube is a non liquid pressure measurement device.
It is widely used in applications where inexpensive
static pressure measurements are needed.
A typical Bourdon tube contains a curved tube that
is open to external pressure input on one end and is
coupled mechanically to an indicating needle on the
other end, as shown schematically below.

62. 60
Typical Bourdon Tube Pressure Gages
Transmitter types use transducers (electrical to
electrical normally) they are used where continuous
monitoring is required
Normally capacitive transducers are used

63. 61
For Switches pressure swithes are used and they
can be used for digital means of monitoring as swith
being ON is referred as high and being OFF is as
low.
All the monitored data is converted to either Current
or Voltage parameter.
The Plant standard for current and voltage are as
under

64. 62
 Voltage : 0 – 10 Volts range
 Current : 4 – 20 milliAmperes
We use 4mA as the lower value so as to check for
disturbances and wire breaks.
Accuracy of such systems is very high .
ACCURACY : + - 0.1 %
The whole system used is SCADA based
INPUT 4-20 mA
ALARM
ANALOG INPUT
MODULE
MICRO
PROCESSOR

65. 63
We use DDCMIC control for this process.
Programmable Logic Circuits ( PLCs) are used in
the process as they are the heardt of Instrumentation.
Pressure
Electricity
Start Level low
Pressure in line Level High
High level
pump Electricity
Stop Pressure
Electricity
BASIC PRESSURE CONTROL MECHANISM
Hence PLC selection depends upon the Criticality of
the Process
TEMPERATURE MONITORING
HL switch
LL switch
AND
OR

66. 64
We can use Thernocouples or RTDs for temperature
monitoring
Normally RTDs are used for low temperatures.
Thermocoupkle selection depends upon two factors:
 Temperature Range
 Accuracy Required
Normally used Thermocouple is K Type
Thermocouple:
Chromel (Nickel-Chromium Alloy) / Alumel
(Nickel-Aluminium Alloy)
This is the most commonly used general purpose
thermocouple. It is inexpensive and, owing to its

67. 65
popularity, available in a wide variety of probes.
They are available in the −200 °C to +1200 °C
range. Sensitivity is approximately 41 µV/°C.
RTDs are also used but not in protection systems
due to vibrational errors.
We pass a constant curre t through the RTD. So that
if R changes then the Voltage also changes
RTDs used in Industries are Pt100 and Pt1000
Pt100 : 0 0
C – 100 Ω ( 1 Ω = 2.5 0
C )
Pt1000 : 0 0
C - 1000Ω
Pt1000 is used for higher accuracy
The gauges used for Temperature measurements are
mercury filled Temperature gauges.

68. 66
For Analog medium thermocouples are used
And for Digital medium Switches are used which are
basically mercury switches.
FLOW MEASUREMENT
Flow measurement does not signify much and is
measured just for metering purposes and for
monitoring the processes
ROTAMETERS:
A Rotameter is a device that measures the flow rate
of liquid or gas in a closed tube. It is occasionally
misspelled as 'rotometer'.
It belongs to a class of meters called variable area
meters, which measure flow rate by allowing the

69. 67
cross sectional area the fluid travels through to vary,
causing some measurable effect.
A rotameter consists of a tapered tube, typically
made of glass, with a float inside that is pushed up
by flow and pulled down by gravity. At a higher
flow rate more area (between the float and the tube)
is needed to accommodate the flow, so the float
rises. Floats are made in many different shapes, with
spheres and spherical ellipses being the most
common. The float is shaped so that it rotates axially
as the fluid passes. This allows you to tell if the float
is stuck since it will only rotate if it is not.
For Digital measurements Flap system is used.

70. 68
For Analog measurements we can use the following
methods :
 Flowmeters
 Venurimeters / Orifice meters
 Turbines
 Massflow meters ( oil level )
 Ultrasonic Flow meters
 Magnetic Flowmeter ( water level )
Selection of flow meter depends upon the purpose ,
accuracy and liquid to be measured so different
types of meters used.
Turbine type are the simplest of all.
They work on the principle that on each rotation of
the turbine a pulse is generated and that pulse is
counted to get the flow rate.

71. 69
VENTURIMETERS :
Referring to the diagram, using Bernoulli's equation
in the special case of incompressible fluids (such as
the approximation of a water jet), the theoretical
pressure drop at the constriction would be given by
(ρ/2)(v2
2
- v1
2
).
And we know that rate of flow is given by:
Flow = k √ (D.P)

72. 70
Where DP is Differential Presure or the Pressure
Drop.
CONTROL VALVES
A valve is a device that regulates the flow of
substances (either gases, fluidized solids, slurries, or
liquids) by opening, closing, or partially obstructing
various passageways. Valves are technically pipe
fittings, but usually are discussed separately.
Valves are used in a variety of applications including
industrial, military, commercial, residential,
transportation. Plumbing valves are the most
obvious in everyday life, but many more are used.

73. 71
Some valves are driven by pressure only, they are
mainly used for safety purposes in steam engines
and domestic heating or cooking appliances. Others
are used in a controlled way, like in Otto cycle
engines driven by a camshaft, where they play a
major role in engine cycle control.
Many valves are controlled manually with a handle
attached to the valve stem. If the handle is turned a
quarter of a full turn (90°) between operating
positions, the valve is called a quarter-turn valve.
Butterfly valves, ball valves, and plug valves are
often quarter-turn valves. Valves can also be
controlled by devices called actuators attached to the
stem. They can be electromechanical actuators such
as an electric motor or solenoid, pneumatic
actuators which are controlled by air pressure, or

74. 72
hydraulic actuators which are controlled by the
pressure of a liquid such as oil or water.
So there are basically three types of valves that are
used in power industries besides the handle valves.
They are :
 Pneumatic Valves – they are air or gas
controlled which is compressed to turn or move
them
 Hydraulic valves – they utilize oil in place of
Air as oil has better compression
 Motorised valves – these valves are controlled
by electric motors