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POWER GENERATION ANDDISTRIBUTION IN VIZAG

STEEL PLANT

N.SANTOSHSUSHMITA DAS

K.KIRAN KUMAR

J.SURESH KUMARV.UMA SOUJANYA

B.BHARATH KUMAR

P. V. JAGADEESH BABU

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VIZAG STEEL PLANT

Visakhapatnam Steel Plant (VSP), the firstcoast based Steel Plant of India is located,16 KM South West of city of Destiny i.e.Visakhapatnam.

VSP has an installed capacity of 3.3 millionTonnes per annum of liquid steel which willbe doubled by 2012.

VSP has become the first integrated SteelPlant in the country to be certified to all thethree international standards for quality(ISO-9001), for Environment Management

(ISO-14001) & for Occupational Health &

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INTRODUCTIONTO

THERMAL POWER PLANT Thermal power plant in VSP is a captive

power plant which is established in the year

1988.

It is established mainly to reduce the cost ofpower consumption.

TPP covers an approximate area of 20acres.

The fuel input of TPP is imported from

Bailadilla ores located in Chattisgarh and

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OBJECTIVES OF TPP

To Supply uninterrupted Cold Blast toBlast Furnaces as per Furnace

requirements .

To supply uninterrupted Essential

Power.

To supply 13 ata process steam for

other units of Steel Plant.

To supply quality De Mineralised water

to meet both internal and plant needs.

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POWER GENERATION &DISTRIBUTION

Constituent departments

Thermal Power Plant

Distribution Networks

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ENERGY CONSUMPTION

SPECIFIC POWER CONSUMPTION:

AVERAGE POWERDEMAND :

600-650 kwh/Ton of steel

227 MW

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POWER REQUIREMENT

Average Load : 227 MW

Peak Load : 260 MW

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SOURCES OF POWER

CAPTIVE POWER PLANT

STATE ELECTRICITY GRID

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CAPTIVE GENERATIONSOURCES

Thermal Power Plant

Back Pressure Turbine Station

Gas Expansion Turbine Station

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MAIN EQUIPMENTS OF TPP

Chemical Water Treatment Plant

Boilers

Turbo-Generators Turbo-Blowers

CDCP Boilers

Back Pressure Turbine Station Gas Expansion Turbine Station

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Chemical Water Treatment Plant(CWTP)

Water to the boilers and otherdepartments is fed from kanithi balancingreservoir.

Boilers require soft water failure of whichforms scales and sludges.

CWTP produces high purity de-mineralized water and soft water.

It has a total 6 De-mineralizing units of125cu m/hr each and 2 softening units of 125cu. m/hr each.

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BOILERSBoiler is an enclosed vessel in which

water is heated and circulated until the

water is turned in to steam at the required

pressure.

BOILERS 5(4 working +

1Standby)

CAPACITY 330 Tons/ Hr

PRESSURE 101ata

TEMPERATURE 540o

C

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All the boilers in VSP are of water tubetype and of BHEL make.

Boiler coal is imported from Bailadilla oresin Chattisgarrh and also from Orissa.

Coal is crushed and stored in RMHP.

Soft water is provided to the boilers whichis treated at chemical water treatmentplant and fed to the boilers through 7

boiler feed pumps each of 2.4MW. Boilers outlet flue gas is passed through

electro static precipitators to control air

pollution.

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TURBO GENERATORS

4 TGs : ( 3

60MW + 167.5MW )

Special features:

Electro Hydraulic Turbine GoverningSystem.

Controlled extraction at 13ata and 4atafor process steam needs. (Only in TG 1,2 &3)

Central admission of steam to reduceaxial thrust.

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Steam is admitted at 90 ata pressure and

500O C. Steam extracted at 13ata is used for valve

operations of the different equipments and

4ata is used for instrumentation purposes. Each turbo generator generates power at

11KV.

All the power generated from TG-1, 2 and3 is directly distributed at 11 KV foressential category loads of VSP.

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Excess power from TG- 1, 2 and 3 is

transferred to 220 KV plant grid throughthree 50/63MVA step up transformers atLBSS-5.

Turbo generators of VSP operate inparallel with state grid.

Excess generation over and above plant

load is exported to APTRANSCO. The short fall of power under certain

conditions is availed from APTRANSCO.

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TURBO BLOWERS

Turbo blowers are blowers which

produces compressed air with the help of

a steam based turbine.

BLOWERS 3( 2 Working + 1 Standby )

CAPACITY 6067 M3 /min each

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These blowers are of axial type and are

the largest blowers installed in India.

To meet the varying needs of Blast

Furnace, the blowers are provided with

adjustable stator guide blades.

Special Features :

-Constant Speed with EHTC- Inlet Guide Vane Control

- Axial type Largest blowers in India

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AUXILLIARY UNITS OF TPP

CDCP (COKE DRY COOLING PLANT)BOILERS - 16nos

Back Pressure Turbine Station -2 x 7.5

MW

Gas Expansion Turbine Station -2 x 12

MW

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COKE DRY COOLING PLANT(CDCP) BOILERS

Hot coke produced in the Coke Oven

Batteries is cooled by circulating Nitrogen.

Hot circulating nitrogen gas is passed

through Waste Heat Boilers in which steam

is produced at 40ata pressure and 440OC

temperature.

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BACK PRESSURE TURBINESTATION

The 40ata steam generated in CDCPBoilers is utilized for driving 2 Nos. of 7.5MW Back Pressure Turbines for

generation of Power.Steam is admitted at 40ata pressure and

440OC temperature and exhausted at

2.5ata pressure. It has a controlled extraction of 7ata

pressure.

The turbine and alternator are of BHEL

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2.5ata exhaust steam is utilised forproduction of chilled water in CWP-1.

7ata extraction steam for processrequirements of CO & CCP zone.

These alternators run in synchronouswith the main generators and areconnected to LBSS-5 through a

220KV 31.5/40/50MVA three windingstep up transformer.

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GAS EXPANSION TURBINESTATION (GETS)

Hot flue gases from the blast furnaces isutilised as input to drive turbines in

GETS. The gas is first cleaned and heated to

140 OC before using it.

Each BF is connected to a turbine of12MW capacity.

7.5MW of power is expected at full

production level.

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Special features

First of its kind in India.

Motor mode operation.At very low pressure or during

shutdown of blast furnaces, the

alternator takes input from the supplylines and acts as a synchronous motor(condenser) which helps in improving

the power factor of the grid. Water washing of stator & rotor blades. Variable stator vanes.

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POWER DISTRIBUTION IN VSP

Power distribution in VSP is categorized

as four types:

Extra High Voltage Distribution (220Kv)

High Voltage Distribution (33/11/6.6kv)

Medium Voltage Distribution (Below 650

V)

Low Voltage Distribution (250 V And

Below)

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EXTRA HIGH VOLTAGEDISTRIBUTION (220 KV)

Power from APTRANSCO is received atMain Receiving Station (MRS).

The entire plant is configured as five

electrical Load Blocks and Step downSub-Stations (LBSS 1-5) with 220 KVtransformers to step down for further

distribution. LBSS1 is connected to LBSS5 by two

radial lines.

LBSS 2,3&4 are connected to MRS by

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POWER NETWORKEASTERN BUS 400 Kv

DC BACK TO BACK

SOUTHERN BUS 400 Kv

TO JAIPUR

(ORISSA)

TO VIJAYAWADA(NUNNA)

315MVA400/220 KvAUTO XMER

220 Kv

TO BOMMURU TO PENDURTHITO

GAJUWAKA

MRS 220 KvBUS 1

BUS 2

BUS 1

BUS 2

TPP 220 Kv

LBSS 1

LBSS 3 LBSS 4 LBSS 2

12.5 MVA

220/33 Kv XMER

TO CPRS

AL1 AL2

ML1ML2 ML3

BC

BC

T150/63MVA

T2

50/63

MVA

T350/63MVA

T5

90

MVA

T4

31.5/40/50

MVA

11 Kv

TG 1

60 MW

TG 2

60 MW

TG 3

60 MWTG 4

67.5 MW BPTG 1

7.5 MW

GETG 1

12 MW

BPTG 2

7.5 MWGETG 2

12 MW

MRS

LBSS 5

GSB 1 GSB 2 GSB 3

POWER GRID

SUB STATION

APSEB SWITCHING STATION

VSP

- BREAKER

LOAD BLOCK AND

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LOAD BLOCK ANDSTEPDOWN SUB-STATIONS

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) Medium Merchant Structural Mill

LBSS4 (220/11/11 kV)LMMM, WRM, Aux. Shops, Adm. Building and

Kanithi reservoir pump house.

LBSS5(220/11&220/11/11kV)

TPP, Plant essential category loads, KBR &Township pump houses & hospital.

MRS (220/33 kV) Plant, Township and construction network.

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HIGH VOLTAGE DISTRIBUTION(33/11/6.6KV)

220KV Power is stepped down to 11/6.6KV at each LBSS station.

This power is distributed to smaller LoadBlock Distribution Station (LBDS) locatedin each unit.

Cross-linked Poly Ethylene (XLPE)

cables are used for 11 KV distribution.

6.6 KV supply is mostly used for motorsof rating 200 to 2000 KW.

Medium Voltage Distribution(Below

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Medium Voltage Distribution(Below650v)

For medium and low voltage loads of

11KV/415 V Load Centre Sub-Stations(LCSS) are formed.

Power is fed from LCSS to Motor Control

Centre, Power Distribution Boards, LightingDistribution Boards.

PVC cables are used for medium voltage

distribution generally.Low Voltage Distribution (250 v and

below)

Consists of power supply on single phase

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ESSENTIAL CATEGORY LOADS

Some of the technological process/equipment requires all time availability ofelectricity.

These include exhausters in BF, SMS,rolling mills, kanithi reservoir pump house,TPP auxiliaries, hospital etc. which accountsto a total of 70MW.

Disturbance of supply may involvedangerous situation to equipment/ heavylosses to the plant.

Power is supplied to them from TPPenerator 11kv switch board and also from

LOAD BLOCK STEP DOWN

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LOAD BLOCK STEP DOWNSUBSTATION 5

This 220 KV Sub station serves as outdoorswitch yard for TPP. This substation

consists of 5 in no. 220 KV/11 KV

transformers connected to the 11 KV

generated switch board of TPP.

MRS and LBSS-5 are interconnected with

three numbers of 220 KV tie lines.

The TPP is synchronized with APTRANSCO

grid, supply at 220 KV/11 KV and

Power is fed from LBSS-5 to LBSS-1 at 220

GENERATOR SWITCH BOARD

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GENERATOR SWITCH BOARD(GSB-1)

GSB-1 is a 11 kV, 4500 Amp, 3 section boardlocated in ECR. Each 60 MW generator is

connected to one section of the board.

GSB-1 is provided with a normal bus coupler

and also a reactor bus coupler of 4500 Amp

reactor between section 1 & 2 as well as between

Sections 2 & 3.

Reactor bus couplers are employed to opposesudden changes in current while coupling the

buses.

All essential category loads of plant are served

directl from GSB-1.

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GSB-2 & GSB-3 11kV SWITCHBOARD

GSB-2 is connected to BPTS and GETSgenerators-1 where as GSB-3 is

connected to the generators-2. No outgoing feeders are connected in

both these board.

These generators are connected tosystem through a three winding220/11/11KV 31.5/40/50MVA Transformer

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SWITCH GEAR IN LBSS-5

CIRCUIT BREAKERS:A circuit breaker is a piece of equipmentwhich can

make or break a circuit either manuallyor by remote control under normalconditionsbreak a circuit automatically under fault

conditionsAll the incoming feeders are provided with4500A SF6 gas type and outgoing feedersare provided with 2000A MOCB typecircuit breakers.

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INSTRUMENT TRANSFORMERS:The function of these instrument

transformers is to transform voltages orcurrents in the power lines to values which

are convenient for the operation of

measuring instruments and relays.There are two types of instrumenttransformers

Current transformer (C.T.) Potential transformer (P.T.)

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The use of instrument transformerspermits the following advantages:

They isolate the measuring instrumentsand relays from high-voltage powercircuits.

The leads in the secondary circuits carryrelatively small voltages and currents.This permits to use wires of smaller sizewith minimum insulation.

All the PTs and CTs of LBSS-5 are ofBHEL make.

LIGHTNING ARRESTER

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LIGHTNING ARRESTERA lightning arrester or a surge diverter is a

protective device which conducts the highvoltage surges on the power system to the

ground.

Under normal operation, the lightningarrester is off the line i.e. it conducts nocurrent to earth or the gap is non-conducting.

On the occurrence of overvoltage, the airinsulation across the gap breaks downand an arc is formed, providing a low

resistance path for the surge to ther n .

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In LBSS-5 lightning arrestors are ofMACHAS make. These are heavy duty

station class type. A total no. of 24lightning arresters are provided each hasrated voltage of 198KV and rated current

10KA.ISOLATOR

Isolator is a switch used to make sure that

an electrical circuit can be completely de-energized for service or maintenance.

Isolator is an off-load device intended to

be opened only after current has been

FREQUENCY BASED

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FREQUENCY BASEDISOLATION OF TPP

To isolate the plant from over/underfrequency conditions of the AP Transcogrid, three frequency relays are provided

in each section of GSB-1 Each relay has four frequency based

operation elements.

Rate of change of frequency(df/dt) with astarting under frequency of 47.7 Hz andsustained over frequency of 51.5 Hz for0.15 sec are the extremities for isolation

of load.

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Frequency based isolation scheme is

provided in three stages:

Stage-I Frequency isolates plant form Grid at 220

kV after a sustained under frequency of

47.5 Hz for 0.5 sec.

Stage-II

Frequency isolates the GSB from 220 kV

network by tripping the 63 MVA

transformers after a sustained under

frequency of 46.9 Hz for 1 sec.

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Stage-III

Frequency isolates some of the selected

loads from GSB-1 after a sustained under

frequency of 46.0 Hz for 0.15sec.

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POWER TARIFF The APTRANSCO Power tariff for VSP is a

two part tariff. Contracted Maximum Demand =135MVA

Energy charges are divided into

i. General industrial loadii. Lighting & fan load

Where lighting & fan load cannot be

segregated, 15 % of total energy accountedas lighting & fan load.

Power factor of VSP shall not be less than

0.95 lag.

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CONCLUSION

We had learnt about the process ofgeneration of power in a thermal powerplant and also using a gas expansion

turbine, which is a useful recovery ofwaste energy.

The applications of various electrical

equipments used in sub-stations for safetransmission of power are clearlyobserved.

The overall plant line diagram has helped

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THANK YOU