Internship Report on thermal power station in vizag steel plant

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ADITYA INSTITUE OF TECHNOLOGY AND
MANAGEMENT, TEKKALI
(AN AUTONOMOUS INSTITUTION)
(Affiliated to JNTU, Kakinada, NBA Accredited, Approved by A.I.C.T.E)
STUDY OF GENERATION AND DISTRIBUTION
AT THERMAL POWER PLANT
A project report submitted in partial fulfilment of
Requirements of the award of the degree
BACHELOR OF TECHNOLOGY
IN
ELECTRICAL AND ELECTRONICS ENGINEERING
Submitted by
ABHISHEK KUMAR Y.DILEEP KUMAR
(13A51A02E9) (14A55A0229)
Under the esteemed guidance of
Sri SURESH KUMAR
Asst. General Manager (Elect)
Thermal Power Plant
Visakhapatnam Steel Plant
Visakhapatnam
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
AITAM, TEKKALI

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ACKNOWLEDGEMENT
We express our profound gratitude to our external guide Sri SURESH KUMAR,
Asst. GeneralManager(Electrical), Thermal Power Plant of Visakhapatnam steel
plant for his valuable guidance rendered by his throughout the project.

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ABSTRACT
This project titled “Study of Generationand distribution of electricalpowerin
thermal power at Visakhapatnam steel plant” covers the complete operation of
the Thermal Power Plant and power distribution in Visakhapatnam Steel plant. The
main objective of the project is to study the various equipment’s provided for power and
the process underneath it. Also some essential electrical ideas and facts which were learnt
in due course are added at the end of this project report.
A generating station which converts heat energy obtained by the
combustion of coal into electrical energy is known as Thermal Power Station. A Thermal
power plant basically works on the principle as seenin Rankin cycle. Steam is produced
in the boiler by utilizing the heat obtained by combustion of coal. This steam is used to
run the prime mover where it gets expanded. This expanded steam is then condensed in
a condenser to be fed into the boiler again. The prime mover (here the steam turbine)
drives the alternator which converts the mechanical energy of the turbine into electrical
energy. Such types of power stations are generally commissioned where its main source
coal and water are available in abundance.

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INDEX
1. THERMAL POWER PLANT 4-19
2. BOILERS 19-25
3. TURBO GENERATORS &BLOWERS
4. LOAD MANAGEMENT 26-29
5. POWER SYSTEM IN VSP 30-32
6. CONCLUSION 33

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1. THERMAL POWER PLANT
Introduction:
The fact that thermal energy is the major source of power generation itselfshows
Thermal power plants importance in India. More than 60% of electrical power is produced
by Thermal powered steam plants in India. The steep rise in the demand for power demands
a larger unit setup which requires the use of more fuel. These plants are trying to keep the
overall cost of power generation low using modern technique and devices.
In steam power plants the heat obtained by the combustion of fossil fuels (coal,
oil or gas) is utilized by the boilers to raise the steam to a high pressure and temperature.
The steam so produced is used in driving the steam turbines and sometimes steam engines
coupled to generators and thus in the generation of electrical energy. The steam turbines or
steam engines thus used not only act as prime movers but also as drives for auxiliary
equipment’s such as pumps, fans etc.
The steam power plants may be installed either only to generate electrical energy
or electrical energy generation along with steam generation for industrial purposes such as
paper mills, sugar mills, chemical works, plastic manufacture, and food manufacture etc.
Generally Thermal power plants are categorized as:
 Utility Power Plant- Power is produced solely for purpose of generation and supplied to the
various kinds of customers through grid.
 Captive Power Plants- Power is produced for supplying quality power for the effective
functioningof the actual plant (say a case of a Thermal power plant present in a steel plant).
Import and export of power takes place in accordance with the load.
The Thermal power plant seen inVisakhapatnam Steel Plant isa captivepower
plant. The power requirement of VSP is met through captive generation as well as supply
from APSEB grid.
Captive capacity of TPP in VSP : 286.5 MW

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 3 units of 60 MW generation capacity.
 2 unit of 67.5 MW generation capacity.
 2 units of 7.5 MW capacity at Back Pressure Turbine Station (BPTS).
 2 units of 12 MW capacity at Gas Expansion Turbine Station (GETS).
The specialty of this power plant is that the energy from the flue gas is not wasted .It is used
in BPTS and GETS power is generated.
~~ ~ ~
4 Ata Process Steam
13 Ata Process Steam
TG 1 TG 2 TG 3 TG 4TB 2 TB 1TB 3
Blast Air to BF
Raw Water
PH 4
CEPLPH
H
P
H
BFP
DM Plant
Gen. Transformers63 MVA 90
M
VATie LinesMRS LBSS 5
TRANSCO S/Stun
Air
He
ate
r
Tub
.
Air
Hea
ter
Ec
on
om
ize
r
B
oil
er
5
101 Ata Main Steam Header
GS
B-1 C
o
n
de
ns
er
De-
aera
Ash
Pond
Chimney
Ash
Slurry
Pump
Hse
Ash
Water
Pump
Hse
ID Fan
FD FanPA Fan
E
S
P
PROCESS FLOW
CHART OF TPP &
BH
RM
HS
ISB
s

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2.BOILERS:
INTRODUCTION
Boiler is a major component in a steam power plant. Combustion of fuel takes place inside
the boiler and water by taking up the heat of combustion turns into steam.
A simple boiler is a closed vessel strongly constructed of steel in which steam is generated
from water by the application of heat. The function of steam boiler is to convert chemical
energy of fuel into heat by combustion and thus to produce steam which is then available
for different purposes.
The boiler with accessories is called as steam generator.
Steam generation is done by evaporating water at constant pressure. The heat required for
vaporizing may be obtained from any source-solid, liquid or gaseous fuels.
Heat obtainable from electricity, atomic reactors and exhaust of engines may also be used.
The generated steam may be employed for the following purposes:
1. Power Generation: Electrical power or mechanical work may be obtained by expanding
Steam in steam engines or steam turbines.
2. Process Work: At low pressures, steam is used in many industries for different purposes.
For drying paper in paper industry, bleaching, sizing etc. in Textile, sugar and chemical
industries.
3. Heating: Steam is also used for heating residential and industrial buildings in winter
and for producing hot water.
 BOILERS : 5 (4 working + 1 Standby)
 TYPE : Water Tube Boiler
 CAPACITY : 330 Tons/ Hr.
 PRESSURE : 101 Atm.
 TEMPERATURE : 540o C
 FUEL : Pulverized coal, BF Gas,
CO Gas, Furnace oil/LSHS
Coal for the plant is obtained from Talcher, Orissa. Lignite coal is obtained.
Lignite is porous, has 30-50% moisture, light weight. It is stored in coal bunkers (Immediate
stock bins) and then ground in coal mills i.e. pulverized to increase the surface area of
combustion. Then Primary Air (PA) fan sweeps the pulverized coal for combustion to occur.
The heat resulting due to this combustion is used to raise the steam in boiler to the required
temperature and pressure.

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The water input given to the boiler is desecrated and demineralized before
sending into the boiler, to prevent the corrosion and damage of boiler tubes and turbine
blades.
A boiler channel on the whole is divided into 2 passes:
 Combustion pass
 Non-combustion pass
The boiler drum consists of steam at different temperatures. The one with higher
temperatures is at top. On an average, the temperature of the boiler is 318°c. The boiler seen
in VSP undergoes natural circulation i.e. due to density difference the circulation occurs.
The heat is transferred by means of radiation.
Fig (3.2.3

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3.3 Fuel comparison:
Fuel Calorific value
 Coal 3200-4500 Kcal/KG
 Coke-oven gas 4425 Kcal/NM³
 Blast Furnace gas 800 Kcal/NM³
 Fuel oil 10000Kcal/KG
To maintain a constant level in the boiler drum, a Feed Regulation System (FRS) is used.
Steam or water from FRS is sent to the boiler drum via economizer and platen water
tubes.Ignition is done with the help of spark plugs. There are some igniter fans for cooling
the igniterguns if necessary. Also there are Flame Scanners toknow if flames have occurred
or not. And for cooling the above, Scanner air fans are present.
Below the boiler, a Bottom Ash Hopper is present. About 15%of the ash is collected by
gravitational force. This is removed every 8 hours. Rest gets passed as flue gas, precipitated
in ESP (Electro Static Precipitator).
An Induced Draft Fan is present at the far end of this system, to suck the gas thus obtained
and leave it out through the chimney high up in the atmosphere.
4. LOAD MANAGEMENT:
Integrated Steel Plants are major consumers of electricity, with specific
consumption of power at around 600-650 KWh/Ton of liquid steel. The estimated annual
power requirement of Visakhapatnam Steel Plant, at full level of production in each shop
(corresponding to 3.0 MT of liquid steel), is 1932 million KWh. This corresponds to an
average demand of 221 MW. The demand is found to be 227 MW on an average and 260
5. TURBO GENRATOR
46.8%
30%
23% 0.07%
Typical Fuel Mix in Boilers
COAL
COG
BFG
OIL

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3. TURBO GENERATORS
5 TGs : ( 3 × 60MW + 2 × 67.5MW ).
3.4.1 Special features:
 Electro Hydraulic Turbine Governing System.
 Controlled extraction at 13 ata and 4 ata for process steam needs. (Only in TG 1,2&3)
 Central admission of steam to reduce axial thrust.
 Air cooled Generators.
3.4.2 Operational limits:
For analysing the operational problems and takingnecessary steps, operational
limits of the generator should be known to be operator. If the operates within the limits, the
system will work without any disturbance. These are the possible occurrences of disturbance
due to some fault seen in generator.
Problems are studied to occur at the following conditions:
a. Generator field failure trip.
b. Generator negative phase sequence trip.
c. Overvoltage and overcurrent trips.
d. Fault in static extension equipment and pole slipping trips.
e. Fault in Automatic Voltage Regulator.
f. Stator or rotor temperature high.
3.4.3 Variation of terminal voltage:
Generator can develop rated power factor when terminal voltage changes
within +/-5% of the rated value i.e. 10.45 to 11.55 KV. The stator current should accordingly
be changed within corresponding values of the MVA outputs and stator currents are also to
be carefully observed. During operation of generator at 110% of the rated value of
continuous operation, stator current should not exceed 4130A corresponding to 105% of the
rated value.

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3.4.4 Variation in frequency:
The generator can be operated continuously at output with a frequency
variation of +3 to -5% over the rated value i.e. 47.5 to 51.5 Hz. However the performance of
the generator with frequency variation is limited by the turbine capacity. The variation in
frequency depends on the load and generation.
 Generation>demand: high frequency
 Demand>generation: low frequency
3.4.5 Overloading:
Under abnormal condition, generator can be overloaded for a short
duration. Permissible value of short time-overloads in terms of stator and rotor currents and
corresponding durationat rated power factor and rated voltage and rated parameters of cold
air and stator and rotor temperatures can be applied.
3.4.6 Operation under unbalanced load:
The turbo generator is capable of operating continuously. When
unbalanced system loading is provided, a continuous negative sequence current during this
period shall not exceed 5% of the rated stator current. If unbalance exceeds permissible
levels, measures are to be taken immediately to eliminate or reduce the extent of unbalance
within 3 to 5 minutes. If not, the machine trips.
3.4.7 Synchronization:
A generator requires to be synchronized if it to be run in parallel with
others. Before it is connected electrically to energize bulbar, the following conditions must
be satisfied.
a. Equality of voltage
b. Equality of frequency
c. Synchronization of phases
With these requirements fulfilled, there will be no voltage difference between any
corresponding pairs of terminals of machines and bus bars, so that points can be electrically
connected without disturbance.

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3.4.8 Synchronization procedures:
1. Ensure that the machine has attained the rated speed of 3000 rpm.
2. Obtain clearance from MCR to synchronize the machine.
3. Put the common “SYN SELECTOR” switch to “Manual with check” position.
4. Put the generator “Synch” switch to “Synch’ position.
5. See that bus voltage and frequency appears in “SYNCH TROLLEY”.
6. Give a closing command for the field breaker to close. Observe the “Red lamp” glows on the
control desk indicating the closing of field breaker.
7. Voltage will start building up due to field flashing and it builds up to 6 to 7KV is the
regulation is in manual mode. Then check the voltage of all 3 phases of voltages are not
equal then check the PT fuses and replace the blown one if any. If every aspect is normal,
then start increasing the voltage by giving ‘raise’ command through ‘Regulation manual’
switch in TG control desk. Raise the voltage till it matches with the bus voltage.
8. If the regulation is in auto, voltage will automatically go to 11KV while raising the voltage
in auto, please observe carefully so that it should not go high abruptly. I if that happens then
immediately change the regulation to manual and adjust the voltage manually.
9. Once the voltage is adjusted, see that frequency of TG is approximately equal to bus
frequency. If difference is there then give impulse to the speed controller by pressing the
speed raise and lower button desk accordingly to bring the frequency approximately equal
to bus frequency.
10. Switch on the “SYNCHROSCOPE” of the frequency of TG is higher than the system
frequency, synchroscope pointer will move in clockwise direction and if the frequency is
lower, it will move in the anti-clockwise direction speed of rotation of pointer will depend
upon the difference in frequencies.

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11. When the voltage and frequency match, the synchroscope will move very slowly in the
clockwise direction. This positions shown that:
 Phase sequences of generated voltage and system voltage are same.
 Effective values of both the voltage are same.
 Frequencies of both are same.
12. Give closing impulse to generator breaker the instance when the synchroscope pointer is
in between 11 &12 0’clock position and the red lamp on “Synchronal Trolley” glows
indicating synchronized condition between TG and system.
13. Once TG breaker is closed load the machine from ECR by pressing “Speed raise” button
up to 10-15 MW.
14. Inform MCR and MRS regarding the synchronization of the set.
15. Put synchroscope switch to ‘OFF’ position. Remove the trolley and put back in proper
place. Put TG synchronizing switch to ‘OFF’ position.
16. Observe the voltage of generator and see that the generator delivers lagging MVAR. If
the generator is delivering leading MVAR then make the TG deliver lagging MVAR by
adjusting the excitation.
17. If the AVR is normal mode then adjust the ‘auto’ position till the ‘Null voltmeter’ for
A/M changeover reads ‘Zero’. Then change the regulation to auto
3.4.9 Asynchroscope operation:
Asynchroscope operation of the generation on field failure is allowed
depending upon the permissible degree of the voltage dip and acceptability of the system
from the stability point of view. During field failure there are important points to be noted.
 Field failure with under-voltage

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 Field failure without under-voltage.
Field failure with under voltage will be sensed and the machine will get tripped without any
delay.
During field failure without under voltage, active load on the generator shall be decreased
to 40% of rated load immediately. The generator can operate at 40% of the rated load
asynchronously for a total period of 15 minutes from the instant of failure of excitation.
Within this period, steps should be taken to establish the reasons of field failure to restore
normally. If it cannot be restored then the set has to be switched off. Then the set should
switched over to the reserve excitation.
3.4.10 Shutdown of generator:
Slowlybringdown mechanical input to a minimum level.Then themachine
is tripped using breakers from the grid. Load is also reduced to avoid abnormality i.e.to
prevent it from affecting other systems.

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Turbo blowers:
BLOWER - 3(2 working + 1 standby)
CAPACITY - 6067 m³/min
3.5.1 Special features:
 Constant speed with EHTC (Electro Hydraulic Turbine Governing System)
 Inlet Guide Vane Control
 Axial type largest blowers in India.
VSP has 2 blast furnaces. To meet the blast air requirement, 3 turbo blowers, each of 6067
nm³/min capacity, are installed at TPP. These blowers are of axial type and are the largest
blowers installed in India. These blowers are provided with suction filters, pre-coolers and
inter-coolers.
3.6 Auxiliaries of TPP:
These include coal conveyors, cooling towers and pump no.4 for cooling
water system, pump house for ash water, ash slurry, fire water and fuel oil and emergency
diesel generators, electricswitchgear for power distribution,ventilationandairconditioning
equipment etc. The entire power generated at Back Pressure Turbine Station (BPTS) and
Gas Expansion Turbine Station (GETS) is transmitted over 11 KV cables to power plant,
stepped up through a 220 KV transformer at LBSS5 and transferred to plant grid.

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Transformer:
TRANSFORMERS CONNECTED TO 60MW GENERATORS
Make : May & Christ W.G.
Type : Dry type air cooled
Connection symbol : DYN5
Class of insulation : F
Power rating : 650 KVA
Primary voltage : 11 KV
Secondary voltage : 480Volts
TRANSFORMERS CONNECTED TO 67.5MW GENERATORS
Make : BHEL, JHANSI
Type : Dry type air cooled
Connection symbol : DYN5
Class of insulation : F
Power rating : 500 KVA
Primary voltage : 11 KV
Secondary voltage : 380 Volts
There are 2 main types of transformers present in a Thermal Power Plant
 Generator transformer

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 Auxiliary transformer
A Generator Transformer is one which steps up the voltage to the grid for the purpose of
distribution.
An Auxiliary Transformer is one which steps down the voltage for the plant purposes.
The transformer consists of a conservator tank, breather, backhauls relay, and transformer
oil mainly. It also has on-load tap changers.
Conservator tank is used for conserving the transformer oil when it expands or contracts
due to change in temperature in insulation.
For the contract of air from inside to outside and vice-versa, a breather is present. It consists
of silica gel to trap moisture. When it changes from blue to pink, it has to be replaced.
The transformer is generally surrounded by gravel, to avoid the growth of grass, and to
prevent insects, snakes and to isolate, restrict the area.
There is a Bocholt Relay which is used to show if there is any internal fault. When the above
occurs, bubbles get generated and float up, thus tripping the relay. There are 2 balls in this
relay. The top one is for alarm and the bottom ball completely trips the transformer.
The reading in the transformer is seen to be 50/63 MVA, which means it can withstand a
maximum of 50MVA during natural cooling and 63MVA during forced cooling

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4.LOAD MANAGEMENT
SHOP AVERAGE DEMAND(MW)
RMPH 4.0
CO&CCP 19.5
SINTER PLANT 29.0
BLAST FURANCE 24.0
SMS&CCM 14.5
LMMM 11.5
WRM 13.5
MMSM 11.5
CRMP 4.0
TPP 35.0
WATER SUPPLY 2.0

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ASP 29.5
TOTAL 221.0
3.2 Sources of power for vsp:
 CAPTIVE POWER PLANT
 STATE ELECTRICITY GRID
 DIESEL GENERATORS
3.2.1 There are three Captive Generation Sources:
 The main source is the Thermal Power Plant (TPP) with 5 boilers, 4 generators ( 3
of 60MW capacity and 1 67MW capacity) and 2 turbo blowers
 A Back Pressure Turbine Station with 2 alternators, each of 7.5MW capacity.
 A Gas Expansion Turbine Station with 2 alternators, each of 12 MW capacity. These
are gas powered alternators unlike alternators in other units which are steam
powered.
Fig (3.2.1)

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5. INTRODUCTION OF POWER SYSTEM IN
VSP
Distribution networks:-
Distribution networks (D.N.W) department is a service sector in Vishakhapatnam
steel plant. It plays a vital role as it supplies power to all the sections in the plant. The major
sections of this department include
Main receiving station (M.R.S)
Load block step-down substations (L.B.S.S)
Relays Testing Laboratory
The brief introduction of these sections is mentioned below,
Main Receiving Station (M.R.S):-
This is a place where power (220kv ac) from A.P.TRANSCO and from Thermal
Power Plant are received. From here the power is distributedtovarious loadblock step down
substations such as L.B.S.S-2, L.B.S.S-3, and L.B.S.S-4.
This is a 220kv substation receives power from VSPSS of APTRANSCO through a
double circuit transmission line and capacitive power plant TPP through 220kv lines.
The following are the loads connected to the BUS BARS:
S. No
1.
2.
BUS
BUS-1
BUS-2
LOADS CONNECTED
TIE-1
TIE-3
LBSS-3
LBSS-4
TOWNSHIP
TIE-2
LBSS-2

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This substation supplies power at 220kv through double circuit transmission line to
LBSS-2, LBSS-3, and LBSS-4. MRS also supplies power to LBSS-2, LBSS-3, and LBSS-4.
MRS also suppliespower totownshipthrough CPRS(ConstructionPowerReceivingStation)
by stepping down from 220kv to 33kv and then 33kv to 11kv and further distributed and step
down to working voltage. The scope includes operation and maintenance of equipment at
MRS and coordination with TPP for import and export of power.
220 kV TRANSMISSION LINES IN VSP
Fig (6.1)
MRS
LBSS
3 LBSS 4
LBSS 2
LBSS 1
LBSS
5
8.3
KM
1.6
KM
2.1KM
3.4KM
1.1 KM
70 MW
50 MW
10 MW
50 MW
70
MW

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Fig (6.1)

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APTRANSCO SUPPLY NETWORK:
The Power Grid Corporation’s Sub-station adjacent to Ukkunagaram is connected
to Vijayawada by a 400 kV line. It is also being connected to Jaipur, Orissa (Eastern Grid)
through DC back to back arrangement of 500 MW capacityand by 400 kV ACdouble circuit
line.
Power is stepped down through a 315 MVA, 400/220 kV auto transformer at Power
Grid Corporation Sub-station and is fed to the adjacent APTRANSCO switching station.
This switching station is also connected to Bommuru and Gajuwaka sub-stations by 220 kV
double circuit lines. Bommuru sub-station is connected to generating stations at
Vijayawada, Lower Sileru, Vijjeswaram, Kakinada and Jegurupadu. Gajuwaka sub-station
is connected to Upper Sileru. Two 1000 MW Thermal Power Stations are expected to come
up in the next few years at Visakhapatnam and close to steel plant.
Power is supplied to VSP from APSEB switching station over two 220 kV lines
on double circuit towers. Power is received at the Main Receiving Station (MRS) located
near Main gate and further distributed to various units within the plant.
Extra high voltage distribution (220kv):
Power from APSEB is received at Main Receiving Station (MRS). The
entire plant is configured as five electrical Load Blocks and Steps down sub-stations are
provided in each block (designated as LBSS 1 to 5) with 220KV transformers to step down
power to 33/11/6.6 KV and for further distribution as indicated below
:

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STATION DESIGNATION AREAS COVERED
LBSS1 (220 / 11 / 6.6 KV) RMHP, CO & CCP, Sinter plant, BF
LBSS2 (220 / 11 / 6.6 KV)
(220 / 33 KV)
BF, SMS, ASP, CRMP, Comp. House-1
Ladle furnace in SMS
LBSS3 (220 / 11 / 11 KV) MMSM
LBSS4 (220 / 11 / 11 KV)
LMMM, WRM, Aux. Shops, Adm. Building
and Kanithi reservoir pump house.
LBSS5 (220 / 11&220 /11 / 11 KV) TPP, Plant essential category loads, KBR &
Township pump houses & hospital.
MRS (220 / 33 KV) Plant, Township and construction network.
Power is distributed within VSP, between above major blocks and MRS
OVER 220 KV lines on double circuit towers. MRS and LBSS5 at TPP are inter connected
by three tie lines for bi-directional power flow. LBSS1 is connected to LBSS5 by two radial
lines. LBSS2, LBSS3 and LBSS4 are connected to MRS by two radial lines each. To ensure
continuity of supply and also facilitate maintenance, the stations are connected by double
circuit line. MRS and LBSS5 are designed with double bus (Main Bus-1, Main Bus-2) and
transfer bus arrangement. At LBSS1, 2, 3 and 4 provisions are made so that with only one
220 KV lines and two transformer in service, all the loads can be catered to.
.

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CONCLUSION
VSP is having its own captive power plant through which the power is
distributed to all the units in VSP. In addition to its own captive power plant, AP TANSCO
grid is also kept synchronized with its power system. In recent stage latest technology and
equipment’s are also being introduced.
This project is the result of our study on the generation and distribution of
Electrical power in Visakhapatnam Steel Plant. The whole generation and distribution
process is thoroughly studied and the report is presented.