2. 2
Introduction
A thermal power station is a powerplant in which the prime moveris
steam driven. Water is heated, turns into steam and spins a steam turbine
which either drives an electrical generator or does some other works, like
ship propulsion. After it passes through theturbine, the steam is condensed
in a condenser and recycled to where it was heated. , this is known as a
Rankinecycle. The greatest variation in the design of thermal power
stations is due to the different fuel sources. Someprefer to use the term
energy center because such facilities convert forms of heat energy into
electrical energy.
Commercial electric utility power stations are m9ost usually constructed
on a very large scale and designed for continuousoperation. Electric power
plants typically use three phaseor individualphaseelectrical generators
to producealternating current (AC) electric power at a frequency of 50Hz
or 60Hz depending on its location on the world. Other large companiesor
institutions may havetheir own usually smaller power plantsto supply
heating or electricity to their facilities especially if heat or stem is created
anywayfor other purposes.
3. 3
Table of contents
1 Introduction 7
2 TPS MuzffarGarh 8
2.1 Installed capacity 8
2.2 Introduction to phase#1 8
2.3 Introduction to phase#2 9
3 Boiler 11
3.1 Water tube boiler 11
3.2 Boiler parameter 11
3.3 Main part of boiler 12
3.4 Boiler protection 16
4 Steam turbine 17
4.1 HP (High pressure) turbine 18
4.2 IP (Intermediate pressure) turbine 18
4.3 LP (Low pressure) turbine 18
4.4 Steam turbine specification 18
4.5 Turbine protection 19
5 FSSS 19
5.1 Decanting area 20
5.2 Fuel oil tanks 20
5.3 First lift pump 20
5.4 Main heaters 21
5.5 Second lift pump 21
6 The generator 22
6.1 Working principle 22
6.2 Main generator parameters 23
6.3 Cooling system of turbo-generator 24
6.4 Protections of generator 27
7 Cycles 29
7.1 Steam cycle 29
7.2 Fuel oil cycle 30
7.3 Air flow cycle 31
7.4 Condensatecycle 32
7.5 Feed water cycle 33
4. 4
1. T.P.S Muzaffar Garh
1.1 Installedcapacity
This power station is a vital and majorthermal power generating
installation connected with nationalgrid system in Pakistan. This
power station was constructed in different phases having total
capacity of 1370MW. It consists of:
Three Russian units of 210MW each
Two Chinese units of 210MW
One Chinese unit of 320MW
Fuel
Dualfuel combustion provision gas& furnace oil hasbeen madefor all
the machines. Furnaceoil is transported through railway wagonsand
tank Lorries.
Unit# Installed
capacity
Working
capacity
Constru
cted By
Construct
-ion Date
Fuel
Type
ST-1 210MW 170MW Russian Sep.1993 P. Gas,
F. oil
ST-2 210MW 175MW Russian Mar.1994 P. Gas,
F. oil
ST-3 210MW Shutdown Russian Feb.1995 P. Gas,
F. oil
ST-4 320MW 280MW China Dec.1996 P. Gas,
F. oil
ST-5 210MW Shutdown China Dec.1995 P. Gas,
F. oil
ST-6 210MW Shortage
of fuel oil
China Dec.1995 P. Gas,
F. oil
Tota
l
1370MW 625MW
Table 1.1 brief views of TPS units
5. 5
2.2 Phase#1 (Unit 1, 2 & 3)
This phaseconsist of three steam units each capable of generating
210MW electricity. The supplier started delivery of equipment to site
in January, 1989and after pre-assembly of equipmentat site,
erection started in July, 1990. Unit#1 wascommissioned in
September, 1993 and unit#2 in March, 1994.
Main Building:
It containsthe turbine hallhaving a span of 45m and dearatorbay,
12m wide. Thestem turbines which drive generators are of three
stage condensing typearranged transversely to the axis of turbine
hall. Theoperationalplatform is at elevation 12.6m and a
maintenancebay at ground flournear unit#1. Thepower plantis
designed block principle: boiler-turbine-generator-unit transformer.
The flue gasexhaustsection of two units is connected with a 200m
high stack, outer section of which is a 195m high concrete shell.
Combined Auxiliary Building:
The building is connected with the main building and it houses
water treatment plantto produce100t/h dematerialized water for
the replenishment of station losses. Hydrogen plantto provide
hydrogen forcooling of generator's r rotor, maintenanceshops,
laboratories, and central control room.
Fuel & Oil Facilities:
Fuel oil facilities are constructed for decanting, oil storage,
preparation and supply offuel to boiler nozzles. It also includes
HSD storage as well as oil facilities for reception, storage,
purification and centralized delivery of turbine oil and insulating oil
to power plant.
Hydraulic Structures:
The cooling water used in condensers is re-circulated in closed cycle
with indicated draft cooling towers, the water is being cooled for
each unit in two cooling towers each consisting of eight fans, two
6. 6
cooling towers carry 27,500Cum/h circulating water for condensers
of one unit.
Startup Boiler:
One startup boiler using diesel oil as fuel with steam outputof 50t/h
is provided to meet steam requirement for initial start of unit as
well as a backup of power plantauxiliaries. A separate stack of 30m
high has been constructed for it.
Electrical Part:
The electricity generated at 15.75 KV is broughtoutfrom unit
transformer at 220 KV and feed to the nationalgrid via a switch
yard. Powerplant auxiliaries are fed at 6.6 KV.
2.3 Phase#2(Units#5 & 6):
It consist of two units of 210MW each having equipmentsimilar to
phase#1. Turbinesare placed longitudinally in main building
outdoorboiler exhaustof two units is connected to onestack.
Overview:
There are many different types of power plantsincluding thermal
power plantsand hydelpower plants. Thermalpower plants use fuel
such as gas, HSD, furnaceoil or nuclear fuel to produceheat energy
that is converted to electrical energy through a series of intermediate
process. Hydelpower plantsconvert the potentialenergy of water to
electrical power as it follows from higherto lower elevations.
The "traditional" thermalpowerplantis the Rankin cycle plant
named after the man who invented the cycle. A power plantcycle is
a series of processes in which a fluid generally water/steam, is used
to convert heat energy to mechanicalenergy. TheRankin cycle in its
simplest form consists of a boiler, a turbine, a condenserand a boiler
feed pump. Early plantshad thermal efficiencies of approximately
25% to 30%. Only 25% to 30% of the heat energy in the fuel burned
in these plants was converted to electrical energy. Therest was lost
in variousways. The Rankin cycle has been refined considerably
over the years and mademore efficient by the addition of
7. 7
componentslike economizer, feed water heaters, super heaters and
re-heaters. The efficiency of Rankin cycle has also been improved by
increasing the pressure and temperature of the cycle. The laws of
thermodynamicsand considerationssuch as material limitation
haveprevented any significantimprovementsense then. Power
plants commonly useheat rate of measure efficiency.
Fuel
Energy
Boiler Heat
Energy
Turbine Mechanica
l energy
Generat
or
Electrical
energy
8. 8
3.Boiler
The boiler is the main part of any thermal power plant. It converts the
fuel energy into steam energy. The fuel may be furnace oil, diesel oil,
naturalgas or coal. Theboiler may be fire from the multiple fuels. The
types of boiler use in the T.P.S phase#2 is "watertube type"
3.1 Water Tube Boilers:
In water tube boilers, boiler water passes through thetubes while the
exhaustgasses remain in the shell side, passing over the tube surface,
since tubes can typically withstand higher internal pressure then the
large chamber shell in a fire tube, water tube boilers are used where
high steam pressure (as high as 3,000Psi)are required.
Water tube boilers are also capable of high efficiencies and can generate
saturated or superheated steam. The ability of water tube boilers to
generate superheated steam makes these boilers particularly attractive
in applicationsthat require dry, high-pressure, high-energy steam,
including steam turbine power generation.
3.2 Boiler Parameter:
Rated evaporating amount 680t/h
Reheat steam amount 575.8t/h
Main steam pressure 140Kg/𝒄𝒎 𝟐
g
Temperature 541°C
Outlet pressure of reheat system 23.8 Kg/𝒄𝒎 𝟐
g
Outlet temperature of reheat system 541°C
Inlet pressure of reheat system 25.8 Kg/𝒄𝒎 𝟐
g
Inlet temperature of reheat system 310°C
Feed water temperature 251°C
Boiler efficiency (Burn oil) 90.26%
Boiler efficiency (Burn gas) 85%
Exit gas temperature (Burn oil) 153°C
Exit gas temperature (Burn gas) 136°C
Consumptionofcrude oil 48.2t/h
Consumptionofnaturalgas 59650 N𝒎 𝟐
/h
9. 9
3.3 Main Parts of Boiler:
The boiler consists of following main parts:
1. Force Draft Fan (FDF)
2. Burners
3. Furnace
4. Up Rise Tube
5. Down ComerTube
6. Water Tube
7. SuperHeater
8. Gas Recirculation Fan (GRCF)
9. Re-Heater
10. Induced Draft Fan (IDF)
11. Air Pre-Heater
12. Chimney
13. Boiler Drum
14. Economizer
3.3.1 Force Draft Fan (FDF)
The force draft fan sucks the air from atmospherewhich is used in
the furnace for burning. Theair from the atmosphere is passed
through the filter to remove the dust and other particles from the air.
The air from the FDF is then fed to the regenerative heaters.
The motorof FDF hasfollowing specification:
Type KK 800 11-8
Rated voltage 6.6KV
Rated current 114/121.3A
Rated speed 747rpm
Output 1000KW
Connection of stator/rotor Y
Insulation class F
10. 10
Permissible rise 80K
Ambient temperature 40°C
No. of phases 3
Rated frequency 50Hz
Power factor 0.81
Degree of protection IP54
Momentof inertia 310 𝑲𝒈𝒎 𝟐
Weight 12020/13250Kg
3.3.2 Induced Draft Fan (IDF):
ID fan sucks the flue gases from the boiler and exhaustthrough
chimney.
The motorof ID fan hasfollowing specifications:
Type KK 800 11-6
Rated voltage 6.6KV
Rated current 20A
Rated speed 991rpm
Rated power 2000KW
Connection of stator winding 2Y
Insulation class F
Permissible rise 80K
Ambient temperature 40°C
No. of phases 3
Rated frequency 50Hz
Degree of protection IP54
Momentof inertia 410 𝑲𝒈𝒎 𝟐
Weight 15970 Kg
3.3.3 Gas recirculation fan (GRCF):
The motorof GRCF hasfollowing specification.
11. 11
Type KK 400 11-4
Rated voltage 6.6KV
Rated current 34A
Rated speed 1491rpm
Rated power 315KW
Connection of stator winding Y
Insulation class F
Permissible rise 70K
Ambient temperature 50°C
No. of phases 3
Rated frequency 50Hz
Degree of protection IP54
Momentof inertia 11.7 𝑲𝒈𝒎 𝟐
Weight 3200Kg
3.3.4 Cooling Towers:
Cooling towers are heat removaldevices used to transform process
waste heat to the atmosphere. Cooling tower may either use the
evaporation ofwater to remove process heat and cool the working
fluid to near the wet-bulb air temperature or relay solely on air to
cool the working fluid to dry –bulb air temperature. Common
application includescooling the circulating water used in oil refiner,
chemical plants and powerstation.
3.3.5 Circulating water pump motor:
The motorof the CWP has following specification:
Type Y1600-12/2150
Stator voltage 6.6KV
Rated current 182A
Rated speed 372rpm
Rated power 1600KW
Connection of stator winding 2Y
12. 12
Insulation class B
Ambient temperature 50°C
No. of phases 3
Rated frequency 50Hz
Weight 17500Kg
3.3.6 CW Pump:
Typeis single stage doublesuction centrifugal pump.
Type 1400S25-1
Capacity 16000𝒎 𝟑
/h
Speed 370rpm
Power 1600KW
Weight 35000Kg
Head 25m
NP SHR 8.5m
3.3.7 Air Pre-Heater:
The purposeof the air pre-heater is to recover heat from the boiler
flue gaswhich increases the thermal efficiency of the boiler by
reducing the useful heat lost in the flue gas. As a consequence the fuel
gases are also sent to the fuel gas stack (or chimney)at a lower
temperature, allowing simplified design of the ducting and the flue
gas stack. It also allows controlover the temperature of gases
leaving the stack.
3.3.8 Economizer:
Flue gases from large boilers are typically 450-650°F. Stack
economizerrecover some of this heat for pre-heating water. The
water is most often used for boiler make-up waterare some other
need that coincides with boiler operation. Stack economizersshould
13. 13
be considered as an efficiency measure when large amountsofmake-
up water are used (i.e. not all condensateis return to the boiler or
large amountoflive steam are used in the process so there is no
condensateto return) or there is a simultaneousneed for large
quantity of hot water for some other use. Thesavingspotential is
based on existing stack temperature, the volumeof make-up water
needed and the hours of operation.
3.4 Boiler Protection:
Fuel protection
Gas pressure protection
Diesel oil protection
Furnaceoil protection
FD fan trip
ID fan trip
Regenerative air pre-heating trip
Drum level high
Drum level low
Re-Heat steam pressure drop
Furnacepressure low
Furnaceflame out
Naturalgas pressure high
14. 14
4. Steam Turbine
Turbineis used to convert the heat energy into mechanicalenergy.
Turbine used in T.P.S MuzaffarGarh is impulse-reaction steam turbine.
The load requirement is controlled by the steam flow through a
governing valve. Maximum steam at full load is 670t/h. When the load
at generator is suddenly decreased then the rpm (frequency) of the
generator is increased and to decrease the frequency we lower down the
steam flow which decreases the speed and maintainsthe frequency.
If load is suddenly increased rotor speed becomes slower, to increase
the speed, steam flow is increased.
Steam turbine has three parts.
1. HP turbine
2. IP turbine
3. LP turbine
(To re-heater) (From HP Super-heater) (From re-heater)
Generator
Condenser
15. 15
4.1 HP (High Pressure) Turbine:
First of all steam from boiler comes into the HP turbine. Steam in the
HP turbine is called live steam or main steam. Rotorblades diameter of
this part of turbine is smallest of the other parts of the turbine .Inlet
steam temperature of the HP turbine is 540 °C and pressure is 130bar.
Outlet steam temperature of the HP turbine is 290°C and pressure is
15bar. HP turbine has total of 12 stages including oneis governing
stage.
4.2 IP (Intermediate Pressure) Turbine:
Steam comes into IP turbine from HP turbine via re-heaters. The steam
pressure in this section of turbine is 14barand temperature is 540°C.
This part has total of 10 pressure stages.
4.3 LP (Low Pressure) Turbine:
The outgoing steam of the IP turbine entered into the LP turbine.
Steam from the LP turbine goes into the condenser.
4.4 Steam Turbine Specification:
Maximum load 210MW
Live steam pressure 132bar
Live steam temperature 538°C
Rated speed 3000rpm
HP cycle exhausttemperature 310°C
HP cycle exhaustpressure 24bar
Re-Heat steam temperature 538°C
Re-Heat steam pressure 14bar
16. 16
4.5 Turbine Protection:
Lube oil pressure (low & high)
Vacuum drop
Live steam temperature drop
Axialshift displacement
Gas cooling pump tripping
HP heater level high
All FWP trip high vibration tripping
Trip unit by switch/emergency
5. Furnace Safeguard
Supervisory System (FSSS):
The FSSS station consists of the following parts:
Decanting area
Fuel oil tank
First lift pump
Main heater
Second lift pump
Diesel pumps
Recirculation pumps
Recirculation heater
Filters
Controlroom
5.1 Decanting Area:
The furnace oil that is used as a fuel in the burners of the boiler furnace
to producethe steam is transported to the TPS through two ways:
17. 17
o Oil tankers
o Train
Forunloadingofthe fuel from oil tankers and train there is separate
unloadingorde-canting station for each. The unload fueloil is initially
stored in the undergroundreservoir; from there it is filled in the main
storage tanks.
02 pumpsare used to fill the main storage tanks from the oil tankers
decanting area. One of them is active (on load)and other is standby.
5.2 Fuel Oil Tanks:
From the decanting area the furnace oil is filled in the storage tanks. From
there it is supplied to the burners of the boiler furnace after proper heating.
Usually one storage tank is called service tank, from there furnace oil is
supplied to the units. The furnace oil is filled in the other tanksfirst and
then filled in the service tank through recirculation pumps(RCP). Theoil
in the tanksis kept heated at the temperature 75-80°C. Thereare total 06
storage tanksfor furnace oil each having a volumeof 20,000𝒎 𝟑
henceeach
can store 2,00,00,000 litter. There are two diesel oil storage tankseach
having capacity of1000ton.
5.3 First Lift Pump:
First lift pump takesthe furnace oil from the service tank and supplied to
the main heaters. There are total 04 first lift pumpswhich are operated
according to unit load conditions. Thespecification of first lift pump
motor is as follows:
3 phase50Hz induction motor:
Connection Star
Power 55KW
Power factor 0.9
18. 18
Efficiency 90%
Voltage 230/400V
Speed 2950rpm
Current 177/102A
5.4 Main Heaters:
There are 04 main heaters each is connected to the respective first lift
pump. Themain heaters heat the furnace oil through the steam which
comes from the boiler. Steam is used to heat the oil in recirculation
heaters. Thesteam follows through thepipes which heats the oil outside
the tube. The temperature and pressure of the steam in the main heater is;
Temperature 270°C
Pressure 11-13bar
5.5 Second lift Pump:
Second lift pumpstake the furnace oil from the main heater and supply to
boiler of the units. There are 04 second lift pumpswhich are operated
according to the unitload conditions.
The temperature of oil that is supplied to the boiler is 105-120°C.
The specification of second lift pump motoris as:
3 phase50Hz induction motor:
Power 250KW
Voltage 6.6KV
Speed 2950rpm
Current 252A
19. 19
6. The Generator
The generatoris a device which converts the mechanicalenergy into
electrical energy.
6.1 Working Principle:
The working principleof generatoris based on the Faraday's law of
electromagnetic induction, which states that:
"Theelectromotive force is alwaysproduced in conductorwhich is placed
in the magneticfield when there is a relative motion between conductor
and the magnetic field".
If the outputelectrical energy is AC, it is called alternator. If the output
electrical energy is DC, it is called DC generator. In fact there is no
difference between alternator and Dc generator except the way the output
is obtained from the generator. In alternator the AC supply is produced in
the armatureand supply is obtained through slip rings where as in the DC
generator are generated AC supply is obtained from the armature through
the spilt rings or commutatorwhich converts the AC into DC. The
following three thingsare necessary for generation of electrical energy.
Magneticfield
Conductor
Relative motion between conductorand magneticfield
In the small generator the magnetic field is being produced in the stator
and the electromotive force is produced in the rotor through Faraday'slaw
of electromagnetic induction. Theelectromagnetic are used in the generator
to producethe magneticfield. In the large generator the magnetic field is
produced by the electromagnetic in the rotor and the electromagnetic force
is produced in the stator .the outputis taken from the rotor, the rotor must
20. 20
Havehigh insulation due to high voltageinduction and it must haveheavy
insulation which may increase the size of rotor, and require more power
for the prime moverto rotate to this heavy rotor
6.2 Main Generator Parameter:
6.2.1 Pilot Exciter:
Type Tfy-46-500
Rated voltage 93/161V
Rated current 286/165A
Rated speed 3000rpm
Rated power factor 0.875
Phase 3
Rated frequency 50Hz
Armature connection ∆/𝒀
Specification OEA.513.039
Manufacturing date 1993-3-1
Rated capacity 46KVA
6.2.2 Alternating Exciter:
Type T1-1165-4
Rated voltage 431V
Rated current 1562A
Rated speed 3000rpm
Rated power factor 0.91
Phase 3
Rated frequency 100Hz
Armature connection 𝒀
Specification OEA.513.039
Manufacturing date 1993-8-24
Rated capacity 1165KVA
21. 21
6.2.3 Turbine Generator Water Hydrogen Cooled:
Type QFSN-210-2
Rated capacity 246MVA
Rated output 210MW
Rated voltage 15.75KV
Rated current 9056A
Rated speed 3000rpm
Rated frequency 50Hz
Phase 3
Connection of stator winding 2-Y
Insulation class F
Power factor 0.85
Excitation voltage 289V
Excitation current 18.67A
Maximum inlet water temperature for stator winding 50°C
Maximum inlet cooling hydrogen 50°C
Water flow for stator winding 35m2/h
Rate H2 pressure 0.3MPa
Specification OEA.512.137
Manufacturing date 1993-2
6.3 Cooling System of Turbo Generator:
The first question arises here is that why we need cooling of the generator?
As the current flows in the stator and rotor of the generatoris very high so
it increases the temperature of the stator and rotor winding. Asthe result
the resistance of the stator and rotor windingsincreases which increase the
power losses and may cause the insulation breakdown.
Two types of cooling are used in the turbo generator of TPS phasesecond.
Stator cooling
Rotorcooling
22. 22
6.3.1 Stator Cooling:
The stator of the turbo generator is cooled by distillated or demineralized
water. For this purposea special plantis installed which prepares the
demineralized water for the stator cooling. This demi water is also used
for cooling system of the thirstier converts the water is passed through the
hollow conductorof stator winding for its cooling.
The demi water is necessary for the cooling of the stator winding because
raw water is not a pure insulator which may cause the flow of leakage
current when passed through statorwinding.
The demi water plant removes the impurities and minerals of the raw
water and make it good insulatorwhoseresistivity is taken at a minimum
level of 200K𝛀.cm. Thedemi water that process through the stator winding
absorbs the heat of stator winding makesit cool and becomes hot itself.
The demi water then passes through heatexchanger(coolers) where its
temperature is decreased by the circulating water coming from the cooling
towers. This demi water is also passed through themechanical and
magneticfilters before passing through stator winding and thirstier
converts.
6.3.2 Water Parameters in Heat Exchangers:
Rated temperature of cooled water at inlet 32°C
Minimum temperature of cold water 15°C
Number of gas heat exchangers 02
Rated water flow in on heat exchanger 150m3/h
6.3.3 Rotor Cooling:
The rotor cooling is doneby H2 gas. Hydrogen is used for the following
purposes:
Its heat exchangecapability is much better than other gases.
It is very lighter than other gases so do not overload the rotor.
Its preparation is very easy and cheap.
23. 23
Hydrogen gasis filled in the generatorand maintained ata pressure of
4Kg/cm2. It takes all the heat of the rotor and cools the rotor winding and
gets warmed it. For the cooling of the gas there are four gas cooler inside
the generatoron each corner. Circulating water of the cooling tower is used
in the gas cooler for hydrogencooling.
Hydrogen gasis explosive if it is combined with oxygen underpressure so
too avoid any leakageofgas and entrance of air inside the generatorthe
rotor assembly is sealed by the seal oil whose pressure is at least
0.7Kg/cm2 morethan hydrogen gasinsidethe generator.
When the generator is turned off for a long time for maintenancepurpose
hydrogen is released from the generator in the air using special method.
Method involvesthat firstly fill the generatorwith CO2 which release the
hydrogen in the air and then in the end air is filled in the generator and
CO2 is released in the air. This method is adopted because if hydrogen is
released using air instead of CO2 then it can cause explosion due to oxygen
in the air which will meet hydrogen underpressure in the generator. After
maintenancehydrogengasis refilled in the generatorusing the reverse
process as described above.
6.3.4 Water Parameters in Gas Cooler:
Rated temperature of cold water at inlet 32°C
Minimum temperature of cold water 15°C
Maximum waterpressure 3Kg/cm2
Number of gas cooler 04
Rated water flow in on gascooler 76.5m3/h
6.4 Protections of Generator:
The following protectionsare installed for the protection of the generator
in TPS.
a. Longitudinal Differential Current Protection:
24. 24
This system is intended to protect againstmultiphaseshort circuit in
generator stator winding and its leads including againstdoubleearth
fault, one of which being the generator.
b. Lateral Differential Current Protection:
This system is intended to protect againstturn-to-turn short circuit of one
phasein the generator stator winding.
c. Earth Fault Protection of Stator Winding:
This system is intended to reveal and disconnect onephase earth fault of
generator stator winding.
d. Differential Protection of the Unit:
This system is intended to backup longitudinaldifferential protection of
generator.
e. Negative Sequence Current Protection:
This system is intended to preventdamageof generatorincrease of
overloading by negativesequence current caused by asymmetric load or
external asymmetric short circuit and abnormaloperating condition of
power grid.
f. Over Current Protection Against Overloading of
Generator:
This system is intended for signaling atsymmetric overloading of
generator stator.
g. External Symmetrical Short Circuit Protection:
This system is intended to protect the generatoragainstexternal
symmetric short circuit.
h. Protection Against Asynchronous mode, when excitation
loss:
25. 25
This system is intended to protect againstasynchronousmode. Oneof the
elements of resistance block relay for protection of the unit against
external symmetrical short circuit used.
i. Protection of Generator Rotor Against Overloading:
This system is intended to protect againstoverloading underemergency
condition as well as increase of failure of generatorexcitation system
which cause long term flow of current of abnormalvaluealong the rotor
winding.
j. Earth Fault Protection In One Point of excitation Circuit:
This system is intended to protect the generatorincase of earth fault at one
pointof excitation circuit.
k. Protection Against Voltage Increase At Generator At Ideal
Operation:
This system is intended to preventin admissible increase in voltageat
turbo-generatorand transformer of unitduring ideal operation of the unit
incase of failure of excitation system.
l. Zero Sequence Current Protection:
This system is intended to backup protection at one phaseshort circuit in
220KV network. It is also used to backup unit protection when short
circuit at the 220KV sideof the unit.
m. Differential Protection of the Exciter:
This system is intended to protect againstall kind of short circuit in the
exciter winding and on its leads.
n. Over Current Protection of ExciterAgainst External Short
Circuit:
This system is intended to protect againstover current in the external
system of the exciter.
