report electrical
TRANSCRIPT
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REPORT ON
SUMMER TRAINING
AT
NTPC FARIDABAD
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ACKNOWLEDGEMENT
I am thankful to NTPC for providing me an opportunity to get
an insight and practical experience in the operation, electrical
grid system, control and maintenance of power plant.
ACKNOWLEDGEMENT
I am extremely grateful to Mr. R.K. Niranjan (HRD-EDC)
under whose guidance this summer training was conducted
successfully. I feel highly indebted to all the senior NTPC
officials who extended me a constructive help in the technical
field.
I am thankful to
Mr K.K Sharma (Sr. Manager-Chemistry)Mrs. Prachi (Electrical maintenance)Mr N.N Mishra (AGM- O&M)Mr Manoj Agarwal (DGM- Mechanical maintenance)Mr Jimmy Joseph (S.S- C&I)Mr D.C Tiwari (S.S- Operation)
I gratefully acknowledge all the engineers/staff who gave us
their valuable time, encouragement, constructive criticism for
familiarizing us with all technical aspects of the power plant.
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Submitted To
Sandeep Tewatia
Mr. R.K Niranjan B-tech
3rd year
(HRD-EDE) Electricalengineering
Hinducollege of engineering
Sonepat-131001
Contents
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1. Overview of the Faridabad gas power station
2. Combined cycle power generation
3. Overview of the power plant
a) gas turbine system
b) Heat recovery steam generator
c) Steam turbine system
d) Condensate
e) Feed water system
4. Electrical systems
5. Mechanical systems
a) Gas turbine and auxillaries
b) Heat recovery steam generator
c) Steam turbine system and auxillaries
d) Condenser and auxillaries
e) Steam cycle charactersticks
f) Feed water system auxillaries
6. Control and Instrumentation
Overview of the Faridabad Gas PowerStation
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(i) Location : Faridabad GPP is located near village
Mujhedi & Neemka in Faridabad
district of Haryana State. The
Latitude & longitude of the site are
280 20 48 (N) & 770 2148 (E)
respectively.
(ii) Land Requirement : 321.45 acres of land has been
acquired (241.53 of Plant & 79.92 for
Township)
(iii) Plant Capacity : 431.586 MW
(GT: 2X137.758 MW + ST 1X156.07
MW)
(iv) Mode of operation : Base Load
(v) Fuel : Natural Gas (Main Fuel)
Naphtha (Alternate Fuel)
(vi) Gas requirement : Average 1.58 mcmd at 68.5% PLF2.30 mcmd at 100% PLF.
(vii) Gas transportation : To be piped from HBJ pipeline by
GAIL.
(viii) CW System : Closed cycle cooling water system
with Induced draft cooling towers
and make up water supply from high
level canal fed by tubewell operatedby Haryana State Minor Irrigation
Tubewell Corporation & Rampur
Distributory of Gurgaon canal.
(ix) Power Evacuation : Transmission System being built by
Power Grid.
(x) Beneficiary State : Haryana State
(xi) Project Cost (PowerPlant & Facilities)
: Rs. 1163.60 crore
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(xii) Cost of Generation : 205.82 paise / kwh
(xiii) Environmental
Aspects
:
Water Pollution : Liquid Effluents from plant and
township will be neutralized before
disposal.
Air Pollution : Emission of NOx will be limited
within 50 ppm during operation of
the plant with natural gas as
stipulated in the Environmental
clearance by MOEF.
(xiv) Project Financing : The project is being partly financed
by Govt. of India in the form of loanand equity. The fund from GOI is
being provided by JBIC, Japan to an
extent of 22171 million Yen. Balance
fund requirement will be met from
internal resources & Domestic
Commercial Borrowings (DCB).
(xvi) CommissioningSchedule
: Govt. App. Sch. Actual
GT#1 Jan 2000 June
1999
GT#2 Mar 2000 Oct. 1999
ST Jan 2001 July 2000
Combined cycle power generation
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COMBINED CYCLE
In combined/closed cycle, two combustion turbine-generators operate in conjunction
with two heat-recovery steam generators and a steam turbine-generator. In the first
cycle, fuel is burned and the resulting combustion gases power two turbine-
generators to produce electricity. Hot exhaust normally lost during this process is
captured and routed through the two heat-recovery steam generators. These unitsboil water to create steam, which spins an additional turbine-generator and
produces more electricity. Finally, the steam is discharged into a condenser, which
returns the steam to its liquid state for recycling.
At FGPS, the gas turbines installed are based on the Brayton Cycle while the steam
turbine is based on Rankine Cycle. These cycles are explained below.
BRAYTON CYCLE
Gas turbines operate on this cycle. In this cycle air is compressed in a compressor.
This compressed air is used for combustion and the combustion product is allowed to
expand in the turbine, which is coupled with the generator. In modern gas turbines
the temperature of the exhaust gases is in the range 500C to 580C.
RANKINE CYCLE
The conversion of heat energy to mechanical energy with the aid of
steam is carried out through this cycle, which involves:
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The initial state of the working fluid is water, which at certain
temperature is compressed by the pump and fed to the boiler.
In the boiler the compressed water is heated at constant
pressure.
Superheated steam is expanded in the turbine, which is coupled
with the generator.
COMBINING TWO CYCLES TO IMPROVE EFFICIENCY
We have seen in the above two cycles that the gas turbine exhaust is of 500C-580C
and in the Rankine cycle temperature required to generate is 500C-560C. So we
use the gas turbine exhaust to generate steam in the Rankine cycle and save fuel
required to heat the water.
ADVANTAGE OF THE COMBINED CYCLE PLANTS
Apart from the higher efficiency, the combined cycle power plants
have following advantages:
Low installation cost
Low gestation period
Better reliability
Low environmental pollution
If efficiency of gas turbine cycle (where natural gas is used as fuel)
is 31% (which is usually the case) and the efficiency of Rankine
cycle is 35%, then over all efficiency comes to 49%.
Overview of the power plant
Plant overview presents a broad picture on how the fuel is utilized to
generate power without going much in detail. It shows how the
different units of a power plant work in tandem to form a complex but
highly organized system, which is efficient and very reliable.
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Gas turbine system
The gas turbine is a common form of heat engine working with a
series of processes consisting of compression of air taken from
atmosphere, increase of working medium temperature by constant
pressure ignition of fuel in combustion chamber, expansion of SI and
Internal Combustion (IC) engines in working medium and combustion,but it is like steam turbine in its aspect of the steady flow of the
working medium.
For the gas turbine to produce any work, the hot gases must expand
from a high pressure to a low pressure. Therefore the gases must first
be compressed. If after the compression the fluid were expanded
through the turbine, the power produced would equal that used by the
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compressor, provided that both the turbine and compressor
functioned ideally.
If heat were added to the fluid before it reached turbine, raising its
temperature, then an increase in power output could be achieved. If
more and more thermal energy could be added to the fluid then more
and more power output could be produced. Unfortunately this cannot
occur as the turbine blades have metallurgical thermal limit. If the
gases continuously enter at a temperature higher than this, the
combined thermal and material stresses in the blades will cause them
to fail. Typically, inlet temperature of 1300K may be found in
industrial turbines and inlet temperatures in experimental models are
up to 1500K.
At P.P.C.L two gas turbines, Model 9E of make General Electric (GT1)
and Bharat Heavy Electrical Ltd. (GT2) are being used. The 9E is a
simple flow cycle, single shaft gas turbine with fourteen reverse-flow
combustion systems. The 9E assembly consists of six major section or
groups:
1. Air inlet.2. Compressor.
3. Combustion system.
4. Turbine.
5. Exhaust.
6. Support systems.
1. GAS PATH DESCRIPTIONWhen the turbine starting system is actuated and the clutch
is engaged, ambient air is drawn through air inlet plenum
assembly, which is then filtered & compressed in the 17-
stage, axial flow compressor. Then this compressed air from
compressor flow into the annular space surrounding the 14-
combustion chambers. From there, it flows into the
combustion liners for proper fuel combustion.
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Fuel for combustion is being supplied by Gail (Gas Authority of India
Ltd.) through HBJ (Hazirapur-Bijapur-Jagdishpur) gas line at a
pressure of 24Kg at 26oC.
This fuel is filtered for the removal of solid particles at the Gas
Conditioning Skid before being fed into 14 equal flow lines each
terminating at a fuel nozzle centered in the end plate of a separate
combustion chamber. Prior to being distributed to the nozzles the
fuel is accurately controlled to provide an equal flow into the 14
nozzle feed lines at a rate consistent with the speed and the load
requirements of the gas turbine. The nozzle introduces the fuel into
the combustion chamber where it is mixed with the combustion air.
This fuel air mixture is then ignited in one of the 14-chambers and
the flame thus produced is propagated to ignite other fuel
chambers through connecting cross-fire tubes. After the turbine
rotor approximates operating speed, combustion chamber pressure
causes the spark plugs to retract so as to remove their electrodes
from the hot flame zone.
The hot gasses from the combustion chambers expand into 14
separate transition pieces attached to the aft end of the
combustion chamber liners & flow from there to three-stageTurbine Section. Each stage consists of a row of fixed nozzles
followed by a row of routable turbine buckets. In each nozzle row,
the kinetic energy of the jet increases while the pressure drops &
each following row of moving buckets, a portion of kinetic energy of
jet turns the turbine rotor. Since the turbine is coupled to the
generator rotor, the resulting rotation of turbine is transferred to
generator, which generates the electrical power.
After passing the third stage buckets, the exhaust gasses (at about
570oC) are directed to the HRSG before being directed into exhaust
hood (at about 140oC). The exhaust hood contains a series of
turning vanes to turn the gasses from an axial direction to radial
direction to minimize the exhaust hood losses. The gasses are then
passed into the exhaust plenum & are expelled into atmosphere
through the exhaust stack.
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Heat recovery steam generator
The Heat Recovery Steam Generator (HRSG) is installed so as to
increase the overall efficiency of the plant. It works by using the
utilizing flue gases of the gas turbine instead of burning fuel to
produce steam which runs a steam turbine which has a generator
coupled with it to produce electric power. With HRSG, the efficiency of
the plant may be in excess of 48%.
The HRSG, installed at FGPS, is a horizontal, natural circulation, single
drum, dual pressure, unfired, water-tube boiler. It is designed to
generate steam quantities 190 T/hr for the HP drum and 40 T/hr for
the LP drum. The feed water temperature is approximately 275
degree Celsius for the HP drum while for the LP drum, it is, 150.1 C at
the designed point.
The gas turbine flue gases act as the heat source of the boiler. The
combustion products heat water in a boiler where it is converted to
steam. This steam drives the steam turbine, which is mechanically
coupled, to a generator.
The modern large sized boilers are of water-tube type design. In theseboilers, water flows inside the tubes and the hot flue gases flow
outside of them. The circulation of water through the tubes of the
boiler is forced circulation through the action of pumps.
Flue gas flow
Flue gases from the exhaust of the Gas turbine are at the temperature
of 540 degree Celsius and are generally at very high velocity.
Therefore the fluegases are passed through a diffuser where pressureincreases at the expanse of the velocity. Next the flue gases are
allowed to pass through diverter damper gates, which permit the flow
of gases out of the bypass chimney or towards the HRSG depending
upon the position of the gate. The flue gases then rise along the
height of the HRSG and are evenly distributed using mechanical
barriers like gas distribution screens for the horizontal flow of the flue
gases along the HRSG. The flue gases generally carry smoke, which
deposit on the water tube as soot and reduce the heat transfer and
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hence HRSG is provided with soot blowers namely FRSB full
retractable soot blowers and HRSBs as per requirements.
Salient Features and Operation
The boiler is divided into nine zones. In order of higher temperature,they are as follows:
1. HP Super heater-II
2. HP Super heater
3. HP Evaporator
4. HP Economizer II
5. LP Super heater
6. LP Evaporator7. HP Economizer I
8. LP economiser
9. Condensate preheater (CPH)
Feedwater at BFP discharge is then pumped separately via HP BFP and
LP BFP to the High Pressure (HP) and Low Pressure (LP) drums from
which HP and LP steam is derived respectively. The cycle for both the
HP and LP steam is basically the same. The water is first taken to therespective economizers to heat the water and then taken to the
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evaporator where the water is converted to steam. This steam is
further heated to produce superheated steam. This process takes
place in the respective super heaters. Now, there is a possibility that
the temperature of the HP steam becomes very high (more than the
specifications) as there are two super heaters. To prevent the steam
from attaining very high temperatures, a device called De-Super
heater is installed between the two super heaters. It works by
sprinkling water on the steam as the steam passes through it. This
lowers down the temperature but also wets the steam. The steam is
dried in the next superheated and hence the temperature of the
steam is controlled. De-superheated is used only when required and
the amount of water sprinkled is also controlled so as not to decrease
the temperature of the steam too low that the second superheated
cannot increase it to the optimum limit. This superheated steam is
then taken to the turbine where it is allowed to expand and cool and
do mechanical work on the turbine rotor. The expanded steam from
the HP steam still has sufficient amount of heat and is taken to the LP
turbine. The steam from the LP turbine is taken to the Condenser
where it is converted back to water, as we cannot pump steam. The
water is extracted from the condenser by the Condensate Extraction
Pump (CEP). The water is extracted from the condenser as there is low
pressure (vacuum, maintained by vacuum pumps) inside the
condenser which has to be maintained otherwise there is a risk of
back-flow of steam back to the turbine. So the difference in pressure
has to be maintained and water has to be forced out. A part of the
steam is also tapped to seal the turbine, which is cooled in the Gland
Steam Cooler (GSC). The sealing is very critical as the difference in
pressure is quite large between that inside the turbine and the
outside. The steam has the tendency to escape and to prevent that
we require the sealing. The water from the condenser and GSC is
pumped together back to the condensate pre-heater and the cycle
begins again.
Everything in the plant works on a closed cycle to increase efficiency
and maintain economical production. The de-mineralized water is
produced after a long process involving dozing, filtering, reverse
osmosis, ion exchangers, etc. which makes the water purification
expensive. So, this water is not wasted and re-used. Only a small
amount of make-up water is taken from the plant. The condensing
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water (from LSP) in the condenser is cooled again and re-used to
condense steam to water in the condenser.
Steam turbine system
The turbine is a tandem compound machine with High Pressure (HP)and Low Pressure (LP) sections. The HP section is a stage flow turbine
whereas the LP section is a double flow. Rigid couplings connect the
individual turbine rotors and generator rotor.
The HP turbine has been constructed for throttle control governing.
The initial steam is admitted before the blading by two combined main
steam stop and control valves.
The steam from HP turbine exhaust is led to the LP turbine throughcross-around pipes. Additional steam from LP stage of waste heat
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recovery steam generator is passed to the LP turbine via two-
combined LP stops and control valves.
HIGH PRESSURE (HP) TURBINE
The HP turbine is of single flow, double shell, construction with
horizontally split casing. Allowance is made for thermal movement of
the inner casing within the outer casing. The main steam enters the
inner casing from top and bottom. The provision of an inner casing
confines high steam inlet temperature and pressure conditions to the
admission section of this casing, while the joint flange of the outer
casing is subjected only to the lower pressure and temperature
effective at the exhaust from the inner casing.
LOW PRESSURE (LP) TURBINE
The casing of the double flow LP turbine is of three-shell design. The
shells are of horizontally split-welded construction. The inner casing,
which carries the first rows of stationary blades, is supported on the
inner-outer casing so as to allow for thermal expansion. The inner-
outer casing rests at four points on longitudinal girders, independent
of the outer casing. Three guide blade carriers, carrying the last guideblade rows are bolted to the inner-outer casing.
BLADING
The entire turbine is provided with reaction blading. The moving
blades of the HP turbine and the initial rows of the LP turbine with
inverted T-roots and integral shrouding are machined from solid
rectangular bars. The last stages of the LP turbine consist of twisted,drop forged moving blades with fir-tree roots inserted in
corresponding grooves of rotor.
Like the moving blades, the HP stationary blades of HP turbine and the
front rows of LP turbine are designed with integrally milled inverted T-
roots and shrouds. The last stages of LP turbine have guide blade rows
of fabricated construction.
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Condensate
Steam after the extraction of work in the hp and lp turbines goes to
condenser through flash box where the LP drain enters the condenser.
Cooling water is supplied by the CW tubes where the water is pumped
in by CW pumps. Water generally gets heated by 7-8 degree celcius.
Steam from the LP exhaust gets condensed via indirect heating and is
collected below in the HOTWELL. Very low pressure in the condenser
is maintained by vacuum pumps. To make up for the water losses
during the steam cycle, make up water is added to the condenser via
DM water line. This DM water can be taken directly from the DM water
line or through the Reserve Feed Tank. Water from the Hotwell is
extracted by condensate extraction pumps (CEP). In this module two
CEPs are provided while only one is operated while other is kept in
standby mode. Water from the CEP discharge enters the Gland steam
condenser (GSC) where it is heated by the gland steam via indirect
heating. Gland steam condenses and is discharged back into the
condenser. Heated water from the GSC is then taken to LPH and other
feedwater systems.
Condenser also receives the HP and LP bypass lanes from the
turbines. The power-plant chemistry is constantly monitored via the
specific conductivity and the PH level of the water in the condenser.
Hotwell level is also important and is constantly controlled.
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Cooling water system
The water in the coolant tubes of the condenser gets heated and is
then taken to the cooling towers. Here the water gets sprinkled fromthe top of the specially designed cooling tower where the rising air
from the bottom cools the water close to its wet bulb temperature.
Thus temperature is lowered by 7-8 degree celcius. Unsaturated air of
low relative humidity gets saturated in this process and leaves the
cooling tower from the top. The suction of the air is provided by the
induced draft fans provided at the tower top. Thus cooling tower is
based on the forced draft cooling. Hence the height of the tower is
quite low.
Cooled water is discharged into the sump where the make up
water is added as water loss occurs during the cooling through
evaporation. Cooling water pumps get the suction from the sump and
pump the water towards the condenser.
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Feed water system
LP heater
Feed water from the GSC enters the LPH where the bled steam heats
the feed water by indirect heating .LPH bypass lane is also provided
to bypass the LP heater .
CPH and CPH RCP
The water from the LP heater goes to condensate preheater kept at
the near exhaust of the HRSG. The flue gases before being discharged
to the atmosphere are used to heat the feedwater. In this process the
temperature of the flue gases falls down from 160 to 104 degree
celcius. Generally this is above the saturation temperature of the SOX
and the NOX gases in the chimney exhaust. When the natural gas is
used the temperature is quite high and saturation temperature llimitis not reached however if the naptha is used then the flue gas
temperature is lower by around 10 degree celcius hence the NOX
gases could condense and form acidic products leading to cold end
corrosion, if the CPH is used. Hence to overcome this recirculation
pumps(RCPs) are switched on which pump the hot water at CPH
discharge back to the CPH inlet thus considerably reducing the heat
transfer and hence the flue gas temperature doesnt reduce to the
saturation temperature limit.
Deaerator
Water from the CPH heater enters the the deaerator where the
dissolved gases are removed from it. The steam from the LP
superheater enters the deaerator from the bottom while the
feedwater is sprinkled fron the top. The rising steam comes in direct
contact of water thereby heating the water and the dissolved gases
which as a result escape from the top along with some of the steam.
The condence steam and the water are collected below in the storage
tank. The storage tank is provided with the heating rod which is kept
hot by the lp steam. The storage tank then separately discharges the
feedwater to HP and LP BFP.
The deaerator is generally kept at the height of 20 to 25 meters to
keep the pressure head above the net positive suction head (NPSH)
level of the water at thr BFP suction.
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ELECTRICAL SYSTEMSELECTRICAL SYSTEMS
The major electrical components used in the switchyard are:
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ISOLATORS
Isolators (disconnecting switches) are switches, which operate
under no load conditions. They are used in addition to circuit
breakers and are provided on each side of circuit breaker to provide
isolation and enable maintenance.
While opening a circuit, circuit breaker is opened first and then theisolator. While closing a circuit, the isolator is closed first and then
the circuit breaker. Isolators are necessary on supply side of circuit
breaker to ensure isolation of circuit breaker from live parts for the
purpose of maintenance.
EARTHING SWITCH
Earthing switch is connected between line conductor and earth.Normally, it is open. When the line is disconnected, the earthing
switch is closed so as to discharge voltage trapped on the line.
Generally, earthing switches are mounted on the frame of the
isolators.
INSULATORS
Provision of adequate insulation in a sub-station layout is of primary
importance from the point of view of reliability of supply and safety
of personnel. The following are the considerations to be made:
The dielectric strength of the insulating material should be
high
It should possess high mechanical strength
It should posses high resistance to temperature changes
The leakage current (to the earth) should be minimum to keep
the corona loss and radio interference within reasonable limits
The insulator material should not be porous and should be free
from impurity and cracks.
The following are the insulators normally used:
Bus support insulator
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Solid core typePoly-cone typeCap and pin typeStrain insulatorsDisc insulatorsLong rod porcelain insulators
Polymer insulators
CARRIER EQUIPMENT
The carrier equipment required for communication, relaying andtelemeter is connected to the line through high frequency cable,coupling capacitor and the wave trap. The wave trap is normallyinstalled at the line entrance.
LIGHTNING ARRESTORSA sub-station has to be shielded against direct lightning strokes byprovision of overhead shield wire/earth wire or spikes (masts).Besides direct strokes, the equipments should be protected againsttravelling waves due to lightning strokes on the lines entering thesub-station. This is done by lightning arrestor.
The most important and costly equipment in a sub-station is the
transformer and the normal practice is to install lightning arrestors as
near to the transformer as possible. Besides protecting the
transformer, the lightning arrestor also provides protection to the
equipment on the bus side located within certain distances
Transformer
Transformer is an ac machine that (i) transfer electrical energy
from one electric ckt to another (ii) does so without a change of
frequency (iii) does so by the principal of electro-magnetic induction
and electric ckt that are linked by a common magnetic ckt.
Operating principal
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The action of transformer is based on the principal
that energy may be efficiently transferred by induction from one set of
coil to another by means of varying magnetic flux
Emf equation
Rms value of emf induced = EMF induced per
turn* no of turn
=4.44*N*f*(flux)
Transformer construction
The transformer is very simple in construction and consists of
magnetic ckt linking with two winding .it consist of a suitable
container for assemble core and winding, such as a tank, a suitable
medium for insulation from it container such as transformer oil, a
suitable bushing for insulating and bringing out terminal of the
winding from the container .etc..
Following main part in the transformer construction;
1. Core construction ;
A transformer core is the steel system which
forms the magnetic with all part pertaining to its construction.
Those part of magnetic ckt which carry the transformer winding
are called the limbs or legs. The core material and construction
should be such that maximum flux is created with minimum
magnetizing current and minimum core loss. The magnetic frame of
the transformer is built up of laminated electro-technic steel. Its
called transformer grade steel consist of 3.5% silicon.
2. Insulation;
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Insulation used in transformer may be classified into two major group
viz major insulation and minor insulation. Major insulation between
winding usually consist of sheet of pressboard and oil ducts. And
minor insulation include the insulation provided between the element
of a given winding such as conductor insulation, insulation betweenthe turns, layers and coil.
3. Insulation oil;
The insulation oil has provides additional insulation ,
protect the insulation from and moisture and it carries heat away the
heat generated in core and coil .
4. Tank;
Small capacity tank are fabricated from welded sheet steel,
while larger one are assembled from plain boiler plates or cast
aluminium parts.
5. Temperature gauge;
Every transformer is provided with a temperature gauge
to indicate hot oil or hottest spot temperature it is a self contained
weatherproof unit made with alarm contact.
7. Oil gange;
Every transformer is provided with an oil gange to indicate
the oil level
8. Breather;
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When the transformer become warm, the oil and gas
expand. The gas at the top of the oil is expelled out .when the
transformer cools, air is drawn into the transformer. Unless preventive
measure are taken, moisture is drawn during the process and it call
breathing.
9. Gas operated relay Buchholz relay;
It is gas and oil actuated protective device and its
practically universally used on all oil immersed transformer having
rating more than 750 kva. The use of such relay is possible only
transformer having conservator.
10.Bushing;
Transformer are connected to hv lines and therefore it
care is to be taken to prevent flash-over from the high voltage
connection to earthed tank. Connection from cable are made in cable
boxes. But overhead connection are to be brought through bushingspecial designed for different classes of voltage.
Type of transformer
Depending upon the type of construction:
1. Core type
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2. Shell type
Depending upon the type of service, in the field of powersystem:
1. Power transformer
2. Distribution transformer
1. Power transformer;
The term is used to include all transformer of
large scale used in generating station and substation for transforming
the voltage at each end of a power transmission line.
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2. Distribution transformer;
The transformer f rating upto 200 kva, used
to step down the distribution voltage to a standard service voltage are
know as distribution transformer.
Generator
Generator is one of the important type of electric machines.
Large ac network operating at constant frequency of 50 hz its called
synchronous generator or alternator
Operation principal;
The operation principal of generator fundamentally same as the dc
machine. But in generator there is no need rectify the time varying
emf which induced in the armature windingit dont required a
commutator. Synchronous generator because of absence of
commutator are comparatively simple and possess several importantadvantage over the dc generator
Generator is a synchronous generator which receives mechanical
energy from a prime mover to which it is mechanical coupled and
drivers electrical energy. Its may be single, two or 3-phase
It classified as i)rotating armature type ii)rotating field type
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Mechanical systemsGas Turbine & Auxiliaries
The plant has two Gas Turbines of Siemens AG model type V94.2,
supplied by BHEL. One Gas Turbine was manufactured at Siemens AG,
Germany and the second Gas turbine has been manufactured by
BHEL. The Gas Turbine is a single shaft machine of single casing
design. Net Output of the Gas Turbine in Open cycle at guaranteed
conditions is 143.22 MW. Peak output is 150.51 MW. ISO output of the
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machine is 159.8 MW. Compression ratio and Turbine Inlet
temperature are 10.5 and 1060 C respectively.
Gas Turbine GUARANTED VALUES
Type V 94.2
Fuel NATURAL GAS
Lower Calorific Value KJ/KG Base Load Peak
load
Net Power Output MW 143.220 150.510
Nox Emissions PPM (V) 50
Reference
Speed RPM 3000
Ambient temperature 0C 27
Barometric pressure bar 1.013
Relative Humidity % 60
Generator power factory -------- Lagging 0.85
Generator Type TARI:108/41
Technical Data sheet-Gas Turbine V94.2
1. Gas Turbine
i. Type / Model V94.2
ii. Manufacture BHEL/SIEMENS
iii. Firing Fuels Natural Gas Main
(Naphtha Alternate HSD Start up/Shut down)
2. Compressor
Type Axial flow Heavy duty
No. of stage 16
Rated quantity of air flow 510 ISO (Kg/sec)
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Compressor ratio 11:1 (ISO Firing NG)
Type of fixing of rotor discs Hirth serration splined together by Tie
Rod
Protective coating for compressor blades Sermetal
No. of coated stationary blade rows 3+ Inlet Guide Vane
No. of coated moving blade rows 6
3. Combustion System
Type Silo Type
No. of combustion Chamber 2
No. of burner / combustion chamber 8
Type of burners Hybrid Burner
Fuel Pressure requirement NG17.5 to 22 bar, oil approx.
80bar at combustion Inlet
(Kg / cm2)
Nox level generator
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The gas turbines are equipped with water injection arrangement. DMwater shall be injected in the combustion chamber to reduce theflame temperature and thereby reduce the NOx emission level duringfuel oil operation. There are 2x100% water injection pumps for each ofthe two gas turbines. The maximum quantity of water injection is 48ton per hour for one gas turbine at maximum gas turbine out put
condition. The system is designed to achieve 65 ppm of NON, duringHSD or Naphtha operation.The NOX Water Injection System details are as given below:
De- NOX Water Injection PumpMake KSB PUMPS LTD.Capacity 50.4 CuM/hrHead 402 M
MotorMake SIEMENSVoltage 415 V, 50 Hz, 3 PHRating 90 KWCurrent 150 A
Heat Recovery Steam Generator (HRSG)
Two Heat Recovery Steam Generators (HRSG) are installeddownstream of two Gas Turbines. HRSGs are unfired water tube, dualpressure, natural circulation type with staggered tube pitcharrangement. These are BHELs Module Steam Generators (MSG)designed for extensivq shop fabrication in order to minimize fieldinstallation cost and schedule.
The system details of HRSG are as given below:
Type OF WHRB Horizontal/ Natural Circulation
HP LPRated Flow T/Hr 231.131 46.383Rated Press.Ksc 81 4.7Rated Temp.deg 530 200
OUT LINE DIMENSIONS
Length 56 M Up to Chimney Center LineHeight 27.4 M Drum Center Line
Width 19.5 M
HP SUPER HEATER AND COMPONENTS
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Design Pressure 106 KscDesign Temperature 569 degGas Flow path Area 76.8 Sq. mDepth of each bank Limited to 1800 mmIn the direction of gas flow
Max. metal temperature 541 deg
HP Main Steam Line
--Pipe Size mm x mm 406.4 x 65--Material SA 335 P 22
LP SUPER HEATER AND COMPONENTS
LP Main Steam Line
--Pipe Size mm x mm 406.4 x12.5--Material SA 106 Gr. B
HP EVAPORATOR AND COMPONENTS- CIRCULATION SYSTEM
Total Heating Surface Area(sqm)-- Gas Side 43929-- Water/ Steam Side 3427
Total No. of Tubes in the bank 1200
-- No. of rows with flow direction 20-- No. of tubes per row 60
Tube Arrangement Staggered
Tube outer diameter mm 51.0
LP EVAPORATOR AND COMPONENTS- CIRCULATION SYSTEM
Total Heating Surface Area (Sq. m)-- Gas Side 31211-- Water/ Steam Side 2399
Total No. of Tubes in the bank 840
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-- No. of rows with flow direction 14-- No. of tubes per row 60
Tube Arrangement StaggeredTube outer diameter mm 51.0Tube Thickness mm 3.0
HP ECONOMISER AND COMPONENTS
Total Heating Sq. mSurface Area-- Gas Side 28956-- Water Side 3096Total No. of tubes in the bank 1520-- No. of rows with flow direction 19-- No. of tubes per row 80
Tube Arrangement StaggeredTube Outer diameter mm 38.1Tube Thickness mm 3.6
LP ECONOMISER AND COMPONENTS
Total Heating Sq. m 368Tube Arrangement Staggered
Tube Outer diameter mm 51Tube Thickness mm 3.0
CONDENSATE PRE HEATER
Total Heating Sq. mSurface Area--Gas Side 24385--Water Side 2607
Total No. of tubes in the bank 1280-- No. of rows with flow direction 16-- No. of tubes per row 80
Tube Arrangement StaggeredTube Outer diameter mm 38.1Tube Thickness mm 3.0
Steam Turbine & Auxiliaries
There is one steam turbine generator set capable of accepting theentire steam generated by two heat recovery steam generators of the
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module. Gross output of Steam Turbine at Generator terminals atdesign operating conditions is 159.99 MW. The steam turbine is ofBHEL make, tandem-compound, condensing, double exhaust havingone single flow HP cylinder and one double flow LP cylinder withreaction type bladeing. HPT module is M-30-25 and LPT. module is N-30-2x HP turbine has 25 stages and LP turbine has 2X7 stages. The
turbine is throttle governed and is capable of accepting variationsfrom the rated conditions within the limits as recommended by IEC-45.The turbine can be operated continuously within the frequency rangeof 47.5 to 51.5 Hz.
The details of Steam Turbine are as given below:
SL. STEAM TURBINE DESCRIPTION
1. Make BHEL
2. Rated output 156 MW
3. Rated steam pressure 78 Kg/sq. cm
4. Rated steam temperature 528 oC
5. Overall length 134.4m (approx.)
6. Overall height 12.0 m (approx.)
7. Type of blading REACTION
8. Type of governing THROTTLE
9. Module No. & details
(i) HP M-30-25 (SINGLE FLOW)
(ii) LP N-30-2X5 (DOUBLE
FLOW)
Rated Condenser Vacuum(mm of Hg) 0.101 Bar
Rated CW Inlet Temp.0C 32
10. Type of cylinders
HP cylinder SINGLE FLOW/
HORIZONTAL SPLIT
LP cylinder DOUBLW FLOW/
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HORIZONTAL SPLIT
11.Operation Frequency
Range
Operation Regime
a) Continuous Operationb) Limited Operationrange continuous at astretch & total lifetime
c) Speed exclusion rangeat operation withoutload
d) Standard over speedtrip setting
Frequency Range
47.5 Hz to 51.5 Hz
Permissible for a
maximum 2 hrs during
the life of LP Blading
speed below 47.5 Hz
speed above 51.5 Hz.
11.7 to 47.5/s
55.5/s
12. Turbine rated speed
(RPM)
3000
13. (i) Critical speeds for
turbine (RPM) balded
rotors
HP 3812
(ii) Combined critical speeds
(RPM) of TG set
1527, 1814, 4187,
5017, 2120.
14. Type of turbine gear HYDRAULIC
15. Turbine speed 50-60 rpm
18. Turbine Governing system
(i) Type ELECTRO HYDRAULIC
(ii) Make BHEL
16. Mode of governing THROTTLE
17. Casing Details
HPT Casing
a) Typeb) No. of Casingsc) No. of No. of flowsd) Inlet parameters
Split
Two
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i) Pr. Kg/cm2
ii) Temperature 0C
e) Exhaust Parameteri) Pr. Kg/cm2
ii) Temperature0
C
Single
--
76.4
528.5
51
175
LPT Turbine
a) Type
b) No. of Casings
a) No. of No. of flowsb) Inlet parameters
Pr. Kg/cm2
ii) Temperature 0C
c) Exhaust ParameterPr. Kg/cm2
Temperature 0C
Split
Two
Single
--
48.3
200
0.105
46.1
Shaft Seal Assembly and Seal Steam System
The external shaft seals at the rotor ends of steam turbine prevent
the ingress of air through any of the shaft seals and discharge of
steam to atmosphere. They perform these functions in conjunction
with the shaft seal steam supply system. HP rear end and LP front
and rear shaft seals are See through type. The advantage of this
type of seal is that it is possible to optimize spacings between theseal strips regardless of relative expansions between rotor and
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housing. HP front end has labyrinth type seals. Seal steam from LP
steam lines of the HRSGs, is fed to seals through a self contained
hydraulic actuated pressure control valve during startup and low
load operation. At higher load leak-off from HP turbine glands
supplies sealing steam through a pressure control valve similar to
seal steam control valve. 2x100% seal steam exhauster fans extract
steam-air mixture from turbine glands to maintain slight vacuum
avoiding steam leakage to atmosphere.
Gland Steam Exhauster
i) Number of pumps in
service (No.)
ONE (1) + One (1)
Stand By
ii) Make & type SK Systems Pvt Ltd.
iii)Size 12.5 x C1
iv)Speed (RPM) 2840
v) Motor rating (kw) 2.2
Condenser
The condenser is box type construction with divided water box, twopass, spring supported, and welded with exhaust-hood of the LP
turbine. The condenser is designed for a heat load of 274.1135 X 106
Kcal/hr, and design circulating water quantity is 26800 m3 per hour.
Temperature rise of cooling water at design point is 10.220 C. The
condenser is provided with integral aircooling section where air and
non-condensable gases are drawn out with help air evacuation
equipment. The condenser is fitted with welded Stainless steel tubes
(grade SS TP 304). Water boxes are dome shaped removable typeand are provided with necessary hinged manholes for easy access to
the interior for inspection. 2x100% vacuum pumps are provided for
maintaining the vacuum in condenser. The vacuum pumps are of
liquid ring type with rotor eccentric to the casing. Pumps are
designed for hogging as well as holding operation. During hogging
operation, both pumps will work simultaneously for quick evacuation,
while during holding operation one pump will operate.
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Main Steam System
The steam generated by individual HRSG is discharged into separate
HP and LP headers. Both HP and LP steam lines are provided with
following features:
i) Motorised steam isolation valves in individual steam lines from
each HRSG near the common steam header going to the steamturbine.
ii) Motorised steam stop valves near each FIRSG to facilitate the
maintenance of individual HRSG and carryout the hydraulic test etc.
iii) Individual bypass lines from individual HPILP steam lines from
HRSG upstream of motorised steam isolation valve.
iv) Suitable warm up arrangement for HP steam lines.
The steam for deaerator pegging is tapped off from the individual
steam lines with two motorised isolation valves. These are joined
together and a common line is run up to the deaerator. Sealing
steam for steam turbine is also taken from this header.
STEAM PRESSURES
Rated Long-time
Operation
Shorttime
Operation
Initial steam 76.04 87.9 99.4 Bar
Ahead of Ist HP drum stage 74.9 86.1 86.1 Bar
At Ist cylinder exhaust 5.1 5.9 5.9 Bar
At inlet to induction stem
valve
5.6 6.4 12 Bar
At inlet to second cylinder 4.83 5.6 5.6 Bar
At second cylinder exhaust 0.101
5
0.3 0.3 Bar
Short time operation: Permissible momentary value. The aggregate
duration of such swings must not exceed 12 hours in any one year
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STEAM TEMPERATURES
Read value
Annual
mean
value
Long-time
value but
keeping
withinannual
mean value
400 h
per
annum
40 h per annum max.
15 min in individual
case
Initial
steam
528.2 531.6 542.2 556.1 0C
At inlet to
LP steam
valve
200.0 208.0 214.0 228.0 0C
At 1st
cylinder
exhaust
175.0 200.9 212.9 340 0C
At 2nd
cylinder
inlet
181.8 207.7 221.7 228.0 0C
At 2ndcylinder
exhaust
46.1 70 70
Condensate System
, 2100%
() .
700 3/ 225 .
().
.
,
.
,
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.
.
() . 350%
,
. .
.
.
,
. ,
2100% , .
Feed Water System
Water from deaerator feed storage tank is fed to HP Economiser and
LP Economiser circuits of the two HRSGs by means of HP and LP
feed water pumps (each 3x50%). Six separate outlet connections are
provided from the deaerator for suction of the pumps. Design rating
of each HP Feed Pump is 325 m3/hour and 1500 MLC. HP Feed water
pumps are high pressure, multistage, horizontal, barrel casing,
removable cartridge type rotating elements, centrifugal pumps.
Single stage Booster pump ensures that NPSH requirements of HP
Feed pumps are met in all operating conditions. A common motor
drives both booster pump and Feed pump through a constant speed
mechanical gearbox. Design rating of each LP Feed Pump is 67
m3/hour and 172 MLC. LP BFPs are also horizontal multistage type
centrifugal pumps, with Ring section design. Both HP and LP Feed
Pumps are provided with minimum re-circulation lines from the
discharge of each pump, for maintaining the minimum flow
requirement of each pump. The minimum recirculation lines are
connected back to feed storage tank.
HP BOILER FEED PUMP
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GENERALDesignation HP Boiler Feed PumpNo. of Pumps 3x 50%Type of Operation ContinuousType of pumps` FK 6D 30Type of Drive Motor
DESIGN PARAMETERSLiquid handled Feed waterTemp of feed water, 0C 155.7Specific weight of feed 911.2Water kg/m3
Suction flow, m3 /hr 325Dynamic Head, mlc 1404Speed, rpm 4200Power input to pump, KW 1400Efficiency of pump,% 81
LP BOILER FEED PUMP
Make Kirloskar EBARA Pumps LtdType 100 x 80 MSS4MCapacity 66.4 CuM/ HrHead 180 M
MOTOR
Make Kirloskar Electric Co.
Control and instrumentation
In the FGPS, application of instrumentation and control systems arefor centralized, automated and safe plant control of equipments likegas turbines, heat recovery steam generators (HRSG), steam turbine
generator and their auxiliaries to achieve maximum efficiency,reliability, safety and availability. There is optimum plant control dueto these controlled instrumentation and control system. In the plant,C&I systems are microprocessor based with functionally distributedpanels i.e. for different signals there are different microprocessorsbased input output cards.
Instrumentation and control panels are provided for each gas turbine
generator and steam generator.
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THE MAJOR COMPONENTS IN THE SYSTEM INCLUDE THE
FOLLOWING
The analog control system
The binary logic control system
The data acquisition and processing system
The power supply system
The operation of the power plant is controlled from the central control
room in which the control panels are located. Provision is made for
local starting and testing of the important equipments, pumps and
motors.
The control panels accommodate keyboards for CRTs, Auto-Manualsstations, set-point stations, sequential control modules, push button modules,
selector switches, emergency shutdown devices, etc.
Protection
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Chemical analysis/water treatment analysis
A large quantity of water is used in boiler for generation the steam.The water used in boiler is called boiler feed water. Hard watercreates a number of problems like corrosion, scale and sludgeformation etc. Natural water is not directly used in boiler because itcontains hardness producing salts. Hence water should be properlysoftened and pure before feeding into boiler.
To softened and pure water following methods:
*By removal of dissolved oxygen& CO2
---- by mechanical deaeration method
*By adding of alkali
Mechanical deaeration method used in NTPC for purification water
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