project report by manish yadav

7/31/2019 Project Report by manish yadav

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UTTAR PRADESH RAJYA VIDYUT UTPADAN NIGAM LIMITED.

PARICHHA THERMEL POWER PLANT

JHANSI(U.P.)

Duration-: From 6 June to 17 July

SUBMITTED TO-: SUBMITTED BY-:

ExNiraj Kumar Tiwari Manish YadavEr.Akhileshkumar B.Tech 4

thyear

ElectricalEngg.

Roll No. 09ee25I.E.T M.J.P.R.U BAREILLY(U.P.)

ACKNOWLEDGEMENTI am extremely thankful & indebted to the numerous UPVUNL Engineers, who

provided vital information about the functioning of their respective department

thus helping me to gain an overall idea about the working of organization. I am

highly thankful for the support& guidance of each of them.

I am highly indebted to my project guide, Mr. AKHILESH KUMAR (AE), Mr.

ASHUTOSH PATHAK (JE) for giving me his valuable time and helping me to grasp

the variousconcepts of switchyard equipments and their control instruments and

their testing.

Last but not the least I would like to thank my parents & all my fellow trainees

who have been a constant source of encouragement & inspiration during my

studies & have always provided me support in every walk of my life.


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MANISH YADAV

B.TECH FINAL YEAR

ELECTRICAL ENGINEERINGI.E.T. M.J.P.R.U. BAREILLY (UP)

PREFACEA thermal power plant uses energy liberated from the combustion of coal and

uses it to water into steam. This steam is used to convert the mechanical energyinto electrical energy. The steam is used to rotate the turbine which is connected

to generator which produced uniform electric field, the flux linked with it

changes, thereby producing e.m.f of varying voltage. Thus an ac power is

generated.

In a thermal power plant an electronic control is required for controlling the

plant. In practical situation we have to check whether ignition of coal taking place

properly or not, because at a particular time, only fixed amount of coal needs to

be present in the boiler. Suppose the ignition of coal taking place properly, then

the amount of coal that accumulates goes on increasing and at particular instant

can use a blast. Hence electronic control in required.

Similarly in pressure sensors are required to measure the pressure on the wall

boiler due to steam and the amount of pressure handling capacity. Thus if the

temperature of steam increase or amount of pressure steam increase, then the

pressure exerted on the wall may exceed safety level.So again electronic control is

required.


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INTRODUCTIONAlmost all coal,nuclear, geothermal, solar thermal electric, and waste incineration

plants, as well as many natural gas plant are thermal. Natural gas is frequently

combusted in gas turbine as boilers. The waste heat from a gas turbine can be

raise steam, in a combined cycle plant that improves overall efficiency. Powerplant burning coal, oil, or natural gas are often referred to collectively as fossil-

fuel power plants. Some bio mass fueled thermal power plant, which do not use

co- generation are sometimes referred to as conventional power plants.

Commercial electric utility power station are most usually constructed on a very

large scale and designed for continuous operation. Electric power plant typically

three phase or individual-phase electrical generators to produce alternating

current (ac) electric power at a frequency 50 hz to 60 hz, (which is an ac sine wave

per second ) depending on its location of world. Other large companies or

institutions may have only there own usually smaller power plant to supplyheating or electricity to their facilities, especially if heat or steam is created

anyway for other purpose. Such shipboard power plants are general lower plant

capacity than full-size electric company plants , but otherwise have many

similarities except that typically the main steam turbines mechanically turn the

propulsion propellers, either through reduction gears or directly by same shaft.

The steam power plant in such ships also providesteam to separate smaller

turbines driving electric generators to supply electricity in the ship.

In some industrial, large institutional facilities, or other populated areas, there are

combined heat and power (CHP) plants, often called co-generation plant, which

produce both power and heat for facility or districe9 heating or industrial

applications. AC electrical power can be stepped up to very high voltage for long

distance transmission with minimum power loss of power. Steam and hot power

loss energy when pipe over substantial distance, so carrying heat energy by steam

or hot water is often only worthwhile within a local area of facility., such as steam

distribution for a ship or industrial facility or hot water in a local municipality.

HISTORY OF INDUSRTYThe name of power plant is PARICHHA THERMAL POWER PLANT, its foundationwas laid in 1979 and it started producing electricity in 1983. It is a state owed,

semi-government project. It has six units which are generating electricity. Two of

110 MW, two of 210 MW and two of 250 MW.So total installed capacity is 1140

MW. Presently it is 3rd

ranking project of U.P.


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This project is thermal based power project, in which combustion of coal is used

to convert water to steam and then steam is used to rotate the turbine. The

rotation drives a AC generator, thereby producing AC power.

All thermal power project need continuous supply of water thus they are built

near the river. A dam has been constructed for this purpose of collection of water,by the name of PARICHHA DAM. It is situated on bank of BENTWA river. Coal is

also required for the project and it is supplied from mines of Bihar.

The plant is spread in an area of 500 acres of land. The turbine, boiler and their

associated auxiliaries have been manufactured and supplied by M/s BHEL. All

protecting instruments have been supplied by M/s KOTA COMPANY. The steel is

supplied by SAIL & TISCO.

GENERAL LAYOUT OF THERMAL POWER PLANT


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Following equipment are used in power plant-:

1)Cooling tower 8)Surface condensor

2)Cooling water pump 9) Intermediate pressure turbine

3)Transmission line 10)Steam control valve

4)Step-up transformer 11)High pressure turbine

5)Electrical generator 12)Deaerater

6)Low pressure steam turbine 13)Feed water heater

7)Condensate pump 14)Coal conveyer

16)Coalpulverizer 23)Economizer

17)Boiler steam drum24)Air preheater

18)Bottom ash hooper25)Precipitator

19)Superheater26) Induced draft fan

20)Forced draft fan27)Flue gas stack

21)Reheater

22)Combustion air intake

STEAM GENERATOR AND AUXILIARY SYSTEM


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Steam generator is a device which convert water into steam. It is not just like

heating device which we used for domestic purpose. The steam generator of unit

producesuper heated steam at almost constant temperature of 810 k (kelvine). To

get such a high temperature water and air heated in multistage process and more

ever for an efficient steam generator design is little bit more complex in order toget high thermal efficiency. Basically it require three thing, and they are air, water

and fuel. The basic auxiliary are as follow-:

PRIMARY AIR FAN-:They are used to insert the fresh air (primary air) from the environment into the

air pre-heater. The pressure at the out let is less than the pressure at the inlet to

maximize the flow of fresh air. As during peak hours more steam is required than

the average, so with the help of these we get the desired flow rate.

No. of PD fan 2 Supplier: BHEL

AIR PREHEATER-:The air pre heater warm the incoming air from primary air by fan by transferring

the heat from the out going flue gas which increase the efficiency of the boiler by

reducing the usefull heat loss in the flue gas. Even in the winter the temperature

of the top of the boiler house around 30*C , so in this way we make good use of

hot air that would otherwise wasted.

DRAFT SYSTEM-:The air is used for combustion in boiler and the product produce in the boiler is

released in atmosphere by draft system.These are two type:

1) Forced draft system

2) Induced draft system

FORCED DRAFT SYSTEM-:These fans are used to draw air from the air pre-heater into the boiler. The

pressure at the outlet is less than the pressure at the inlet to maximize the flow of

air. The motor is used in the fan is 3 phase induction motor which rotate at very

high speed approximately 1440 rpm.

No. of FD fan:2 Supplier:BHEL

INDUCED DRAFT FAN-:To maintain the flow of waste gas at appropriate rate we installed induced draft

fan in between electro precipitator and the chimney. It act as the suction fan

which suck the waste gas from the electrostatic precipitator. It is designed with


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the ductwork, economizer, air preheater and air pollution control equipment

under all operating conditions.

No. of ID fan-: 3 Supplier: BHEL

BUNKER-:

They are the large drum shaped structure body used to collect crshed coal fromthe conveyer belt. They have cone shaped structure at there bottom used to

transformer the coal under the effect of gravity into feeder. In bunkers any

unwanted material such as stone are removed from the coal before being transfer

to feeder.

FEEDER-:

They are used to feed the mills. They are just bellow the bunkers and received thecrushed coal from them and transfer it to mills at desired rate. They decide that,

how much quantity of coal should be delivered to mills.

MILLS-:Ball mill, a type of grinder, is a cylindrical devise used in grinding of crushed coal

received from feeders. In the mills coal is grinded to a fine powder from which we

called as pulverized coal. We pulverized the coal to increase the efficiency of coal,

because efficiency of coal in finely powdered is higher than its crushed from.

Power plants mills can operate continuously, fed at one end and discharged at

other end

ECONOMISER-:It is nothing but a heat exchanger. In boiler economizers are the heat exchange

device that heat fluids, usually water, up to but not normally beyond the boiling

point of that fluid. Economizer are so named because they can make use of

enthalpy in fluid stream that are hot, therefore increasing the boiler efficiency.

They are a device fitted to the boiler which save energy by using the exhaust gas

from the boiler to preheat the cold water used to fill it.

DEAERATOR-:It is a device that is used for the removal of air and other dissolved gas from the

feed water to steam-generating boiler. In particular, dissolved oxygen in boiler

feed water will cause serious corrosion damage in steam system attaching to the

wall of the metal piping and other metallic equipment and from oxide(rust).

Water also combine with the dissolved carbonic acid that cause further corrosion.


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In unit the deaerator is designed to remove oxygen down to level 6ppb by weight.

Unit havesprey type deaerator which serve as both deaeration section as wll as

boiler feed water storage tank.

No. of deaerator :1 type: sprey type Supplier:BHEL

FURNACE-:It is large rectangular shaped structure used as the place to burn pulverized coal.

It transfer energy to the water by chemical reaction of burning pulverized coal.

The water enters the boiler through a section in the convection process pass

called the economizer. From the economizer it passes to the steam drum. Once

the water enters the steam drum it goes down the down comers to the lower

inlet water wall headers. From the inlet headers the water rises through the

water walls and is eventually turned into steam due to the heat being generatedby the burners located on the front and rear water walls. As the water is turned

into steam/ vapor is passed through a series of steam and water separators and

then dryers inside the steam drum. The steam separator and dryers removes

water droplet from the steam and the cycle through the water walls is repeated.

This process is known as natural convection.

STEAM DRUM-:It is a standard feature of water tube boiler. It is a reservoir of water/ steam at the

top end of the water tubes. The drum store the steam generated in the water

tubes and act as the phase separator for the steam mixture. The difference in thedensities between hot and cold water helps in the accumulation of the hotter

water and saturated steam into the steam drum. It is generally made from high

carbon steel with high tensile strength and its working temperature around 400*C

and pressure well above 350 psi(2.4 MPa). The separated steam is taken out from

the top section of the drum for the upper heating purpose. The watyer which


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sseparated out from the steam is collected at the bottom of the steam drum flow

down through the down comer pipes to header and water drum.

SUPER HEATER-:The unit have super heater section in the steam generating furnace (boiler). It is a

device used to covert saturated steam into dry steam of temperature around537*C and pressure of around 600 psi. super heated increases the efficiency of

steam turbine.

Type : Radiant type super heater

REHEATER :As its name indicate, it is a equipment that is used to reheat the steam. After

losing some temperature and pressure in the high pressure turbine steam is

return back to re-heater section of the boiler where it regain some temperature

and pressure. Reheater increase the efficiency of the steam turbine.

ELECTROSTATIC PRECIPITATOR-:Due to burning of pulverized coal we get bottom ash and fly ash as the by

product. Bottom ash as its name indicate at the bottom of the boil and removed

time to time. But flue ash come along with the waste gases we use electrostatic

precipitator. It remove particle from a flowing gas using the force of induced

electrostatic charge. ESP are highly efficient device that minimally impede the

flow of gases through the device, and can easily remove fine particle matter. It

remove up to 99.5% flue ashes from the waste gases.FLUE GAS STACK-:It is tall vertical, almost cylindrical structure used to deliver waste gases at such

height so that they can not create pollution.

No. of chiney:1 height:150 m

SOOT BLOWER:Continuous or frequent on line cleaning of furnace, boiler, air preheater,

economizer heating surface is necessary to maintain the performance and

efficiency. Here soot blower is steam operated.

TURBINE AND AUXILLIARY SYSTEMThe steam turbine haveauxilliary systems enabling them to work satisfactorily and

safely. The steam turbine generator being rotating equipment generally has a

heavy, large diameter shaft. The shaft therefore requires not only supports but

also has to be kept in the position while running. To minimize the frictional

resistance to the rotation, the shaft rotates , are lined with a low friction material


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like Babbit metal. Oil lubrication is provide to further reduce the friction between

shaft and bearing surface and to limit the heat generated.

STEAM TURBINE-:It is mechanical device that extract thermal energy from the pressurized steam,and convert it into rotary motion. The steam turbine is a form of heat engine that

drives much of its improvement in thermodynamic efficiency through the use of

multi stage in the expansion of the steam, which result in a closer approach to the

ideal reversible process. There are three turbines used in power plant-:

Steam turbine

1) High pressure steam turbine (impulse type)

2) Intermediate pressure steam turbine (impulse type)

3) Low pressure turbine (reaction type)


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Systematic flow of fluid impulse and reaction turbine

In extract type steam turbine, we extract some amount of steam at particular

temperature to perform some other work. In this unit we extract some steam

from low, intermediate and high pressure turbine to heat the condensate which

again feed to the boiler.

No. of low pressure heater:3

No. of high pressure heater:4

Some steam is also extract from high pressure turbine to run boiler feed pump

known as turbine drive boiler pump.

RATING-:MW-210

RPM-3000

Main steam pressure - 150 kg/cm2

No. of low pressure turbine - 1

No. of high pressure turbine - 1

No of intermediate pressure turbine-1

Main steam temperature - 537*c

Insulation class - F

Gas pressure - 4 bar(G)Type - THR1108/44

Spec. -IEC:34

THREE PHAES GENERATOR(TURBO GENERATOR)-:


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An electric generator is a device that convert mechanical energy (rotational

energy of shaft) into electrical energy. It work on the principle of electromagnetic

induction and generate electricity according to the fairadeys law. The shaft of the

generator is rigidly coupled with the shaft of the steam turbine. When the shaft of

steam turbine rotate, the shaft of the generator is also rotate, since this shaft isplaced in magnetic field created by three phase winding at the stator, hence three

phase electricity is generated.

RATING-:

KW - 250000

P.F. - .85 LAG

KVA - 294100

VOLTS - 16500

STATOR

AMPS - 10291VOLTS - 299

ROTER

AMPS - 2497

RPM - 3000

FREQUENCY (hz) - 50

PHASE - 3

CONNECTION - YY

COOLANT - HYDROGEN

EXCITER-:An electric generator that uses field coils rather than permanent magnets will

require a current flow to be present in the field for the device to be able to work.

If the field coils are not powered, the rotor in a generator can spin without

producing any usable electric energy. To excite the coil of stator winding we have

a separate arrangement known as exciter. It provide current to the stator winding

which create magnetic field inside the generator.

CONDENSER-:the primary purpose of a condenser and circulating water is to remove the latent

heat from the stem exhausted from the exhaust end of the turbine and to

transfer the latent heat so removed to the circulating water which is the medium

for dissipating this heat to the atmosphere. A secondary purpose is to recover the

condensate resulting from the phase change in the exhaust steam and recirculate


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it as the working fluid in the cycle. This purpose is accomplished in to steps. In the

first step, the condenser is supplied with circulating water which serves as a

medium for absorbing the latent heat in the condensing exhaust steam. Here the

source of this circulating water is pochampad dam. In the second step, the heated

circulating water is rejected to the natural body of water or recirculatedsourcewhich .in turn, transfer the heat to the atmosphere, principally by evaporative

cooling effect.

COOLING TOWER-:These tower is used to extract heat from the circulating water by the phenomena

of evaporation. Hot circulating water from the tubes of the condenser istransferred to the cooling tower with the help of pipes and tunnels. Cooling tower

pump are erected nearer to the cooling tower to uplift the hot circulating water

to the top of the tower.

In an induced draft mechanical cooling tower, atmospheric air enters the louvers

at the bottom perimeter of the tower, flows up throws the fill, usually counter

flow to the falling water droplets. And is ejected to the atmosphere in saturated

condition thus carrying off the operating load of heat picked up in the condenser.

In convectional tower about 75% of the cooling takes place be evaporation and

the remainder by heat conduction; the ratio depends on the humidity of theentering air and various factor.

COOLING WATER MAKE UP:Make must be continuously added to the tower collecting basin to replace water

lost by evaporation and drift. Here the makeup water must be softened to

prevent scaling of heat transfer surfaces; this will be accomplished by means of


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cold lime softening. Also the circulating water is treated with bi-oxides and

inhibitors while in use to kill algae, preserve the fill , and prevent metal corrosion

and fouling. Algae control is accomplished by means of chlorine injection acid and

phosphate feeds are used for pH control and to keep that surfaces clean.

ASH HANDLING SYSTEMThere are two types of ash are produced in the combustion of fuel-:

1) Bottom ash

2) Fly ash

BOTTOM ASH-:Bottom ash refers to the non-combustible constitution of coal with traces of

combustible embedded in forming clinkers and sticking to hot side walls of a coal-

burning furnace during its operation. The clinker lumps get crushed to small sizes

by clinker grinders mounted under water and fall down into through from where

a water ejector takes them out to a sump. From there it is pumped out by suitable

rotary pumps to dumping yard for away.

FLY ASH-:Fly ash is one of the residues generated in the combustion of the coal. Fly ash is

generally captured from the chimney of coal fired power plant, and is one of two

types of ash that jointly are known as coal ash the other bottom ash is removed

from the bottom of the coal furnace. Depending upon the source and makeup of

coal being burned, the components of fly ash vary considerably, but all fly ash

includes substantial of silicon oxide (SiO2) and calcium oxide (CaO), both beingendemic ingredients in many coal bearing rock strata.

FLY ASH CLLECTION AND DISPOSAL-:Fly ash is captured and removed from the flue gas by electronic precipitator or

fabric bag filters located at the outlet of the furnace and before the induced draft

fan. The fly ash is periodically removed from the collection hoppers below the

precipitators or bag filters. Generally, the fly ash us pneumatically transported to

storage silos for subsequent transport by trucks or railroad cars.

BOTTOM ASH COLLECTION AND DISPOSAL-:At the bottom of the furnace, there is a hopper for collection of bottom ash. This

hopper is always filled with water to quench the ash and clinkers falling down

from the furnace. Some arrangements is included to crush the clinkers and

bottom ash to a storage site.

OTHER SYSTEMS


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1.MONITERING, CONTROL AND ALRM SYSTEM:Most of the power plant operational control are automatic. However, at times,

manual intervention may be required. Thus the plant is provided with monitors

and alarm systems that alert the plant operators when certain operating

parameters are seriously deviating from their normal range. In unit we have acontrol unit at the floor where turbine- generator is located. That control unit

have connection from all over the plant. In that control unit we have technician as

well as supervisor to supervise the smooth running of the plant. If any thing is

going wrong, or not working, they get information about that fault in their

system. And then some person will go that section or to replace tat section.

2. BATTERY SUPPLIED, EMERGENCY LIGHT AND

COMMUNICATION-:

A central battery system consisting of lead acid cell units is provided to supplyemergency electric power, when needed to essential items such as the power

plants control systems, communication systems, damage free shut down of the

units in an emergency situation.

3.BUS DUCT-:At the turbo generator, the electricity which produced is of very high current. To

carry this high current electricity to step-up transformer we used bus duct.

Bus duct are special type of transmission equipment capable to handle very high

value of current (bus duct transmit electricity of 16200 amps).


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PROJECT REPORT

ON

SWITCH YARD


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1.INTRODUCTION-:A switchyard is essentially a hub for electrical power sources. For instance a

switchyard will exist at a generating station to coordinate the exchange of power

between the generators and the transmission lines in the area. A switchyard will

also exist when high voltage lines need to be converted to lower voltage for

to consumers.From switch yard power is distributed to the variousdepartment of

power plant and supplied to grid.Switchyard consists of the airinsulated

aluminium bus type and of highvoltage SF6insulated dead tank circuitbreakers

arranged in a ring bus configuration.Each circuit breaker are equipped with a no-

load breaker, air insulated switch on eachside.An isolating disconnect switchare

installed in eachgenerator transformerconnection to the bus.Inswitchyard, a

power transformer is used to step up or step down the voltage.Current voltage

transformers are located at points within the switch yard to provide for metering

and relaying. Control,protection and monitoring for the switch yard will be

located in the switch yard relay room of electrical building. Interface with SCADA

system are provided. The communication between the facility switch yard and the

control building facilitated.


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ONE LINE DIAGRAM OF 400KV SWITCH YARD


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ABOUT-:

Switchyard is located 30 meters east of the main power house building.400 kV

switchyard is having two numbers of double main and one transfer bus system. It

consist of 8 bay which contains two interconnecting transformer (ICT), isolator,

circuit breaker, earth switches, wave trap, current transformer, capacitor voltage

transformer etc. 400 kV is designed to limit the switching surge over voltage to

2.5 p.u. and sustain surge over voltage to 1.5 p.u.

The symmetrical fault current is 40 kA (rms). The basic insulation level (BIL) is

1425 kV. The switching surge is 1050 kV. Each bus comprise of three phase strung

buses with two sub conductors per phase. ACSR MOOSE conductors are used for

stringing on the gentries of the switchyard. It is tied up with double tension string

assembly in twin bundles with 100mm sub conductor spacing. For connecting the

breaker with isolator 4 IPS aluminum tubular buses in each bay are used. Twoconnect the main bus 1 to main bus 2 with bus coupler which is stable on bay 5.

But there are no 400 kV line so the power is transmitted to 220 kV line to various

area.

1)The three line of 220 kV is transmitted to BANDA.

2)The two line of 132 kV is transmitted to MAINPURI.

SWITCHYARD TYPE-:(i)Conventional Air Insulated Type

(ii)Gas Insulated Type

(iii)Hybrid Type

(I)Conventional Air Insulated Type-:

In Air Insulated Switchyard busbars and connectors are visible. In this

switchyardCircuit Breakers and Isolators, Transformers, Current Transformers

Potential Transformers etc. are installed in the outdoor. Busbars are supported

on the post Insulators or Strain Insulators. Substations have galvanized steel

structures for supporting the equipment, insulators and incoming and outgoing


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lines are the primary criteria for these switchyard andoccupy a large area for

installation.

(II)Gas Insulated Type-:In Gas Insulated switchyard variousequipments like Circuit Breakers, Current

Transformers, Voltage Transformers, Busbars, Earth Switches, Surge Arrestor

Isolators etc are in the form of metal enclosed SF6 gas modules. The modules are

assembled in accordance with the required Configuration. The various live parts

are enclosed in the metal enclosures (modules) containing SF6 gas at high

pressure. Thus the size of Power Substation reduces to 8% to 10% of the air

insulated power substation.

(III)Hybrid Type-:Hybridswitchyard are the combination of both conventional and Gas

insulated substation. Some bays in a switchyard are Gas Insulated Type

and some are air insulated type. The design is based on convenience, Local

Conditions available, area available and Cost.


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DISCUSSIONS OF SWITCHYARD SCHEMES-:

SCHEME 1-:Main and Transfer Bus Scheme

SCHEME 2-:

Sectionalised double main and transfer bus


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SCHEME 3-:

One and half breaker scheme

EQUIPMENT USED IN SWITCHYARD-:

1)POWER TARNSFORMER


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2)BUS BAR

3)ISOLATOR

4)EARTH SWITCH

5)CIRCUIT BREAKER

6)LIGHTENING ARRESTOR

7)CURRENT TRANSFORMER

8)CAPACITIVE VOLTAGE TRASFORMER

9)WAVE TRAP

10)PROTECTIVE RELAYS

11) CORONA RING

12)SCADA SYSTEM

1.POWER TRANSFORMERTransformer is a static equipment, which converts electrical energy from one

voltage to another.There are two power transformer used for generating and transmission of power

supply one which generating transformer and another is interconnecting

transformer.

GENERATING TRANSFORMER-:The power delivered from the turbo-generator is step up by generating

transformer to high voltage. The star-delta connection is used . The voltage are

step up from 16.5Kv to 400kv.

RATINGS-:Types of cooling - ONAN ONAF OFAF

Rated power - HV IV LV

(MVA) 189 252 315

Rated voltage - 400 16.5


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(KV)

Type - Auto transformer

Vector group - YNd11

Frequency - 50

(HZ)No of phase - 3

TRANSFORMER CONSTRUCTION-:

CORE-:Core is manufactured from lamination of solid grain oriented silicon steel, which

gives very low specific loss at operating flux densities. joints of the lamination are

designed such that the electromagnetic flux is always in the direction of grainorientation. The core clamping structure is designed such that it take cares of all

the forces produced in the winding in the event of any short circuit.

WINDING-:1)Windings are made from paper insulated copper conductors which are

transposed at regular intervals throughout the winding for ensuring equal flux

linkage and current distribution between strands.

2)interleaved or shielded construction is adopted for the high voltage windngs to

ensures uniform distribution of impulse voltage. Insulation spacers in the winding

are arranged such that oil is directed through the entire windings for ensuring

proper cooling.

COOLING-:For ONAN/ONAF cooling, oil flows through winding and external cooler unit

attached to the tank by thermo-syphonic effect.

For OF AF/OD AF/OF WF cooling, the oil is directed through the winding by oil

pumps provide in the external cooling unit.

External cooler units consists of pressed steel sheet radiators mounted directly on

the tank or separate cooler banks for air cooled transformers and oil to water

heat exchangers for water cooler transformers.


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CONSERVATOR-:Conservator are provided to take care of the expansion and contraction of

transformer oil, which takes place during normal operation of the transformer.

Wherever specified flexible separators or air cell if provided in the conservator

can prevent direct contact of air with the transformer oil.

A smaller oil expansion vessel is provided for the Off Load Tap Changer.

Magnetic oil level gauge is fitted on the main conservator which can give alarm

/trip in the event of the oil level falling below the pre-set levels due to any reason.

PRESSURE RELIEF DEVICE-:A device for avoiding high oil pressure build inside the transformer during fault

conditions is fitted on the top of the tank. The pressure relief device allows rapid

release of excessive pressure that may be generated in the event of serious fault.

This device is fitted with an alarm/trip switch.

A bright colour coded mechanical indicator pin in the cover moves with the valve

disc during the operation of the pressure relief device and is held in position by an

O ring in the pin bushing .The indicator may be reset manually by pushing itdownward until it reset on the valve disc.

GAS & OIL ACTUATED (BUCCHOLZ) RELAY-:Gas and oil actuated relay is fitted in the feed pipe from the transformer tank to

the expansion vessel for collection of gas. If generated in the oil. The relay

operates on the fact that almost every type of the fault in an oil immersed

transformer gives rise to generation of gas. This gas is collected in the body of the

relay, and is used to closed the alarm switch. In the event of any severe fault, the

sudden increase in oil pressure causes an oil surges towards the expansion vesseland this is used to closed the trip contacts. This oil surges will impinge on the flap

fitted to trip element causing it to rotate about its axis and thus bringing the

mercury switch to the closed circuit position, which in turn operates the tripping

device.


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In the event of serious oil loss from the transformer, both alarm and trip elements

operate in turn in the manner previously described for gas collection.

Two brass petcocks are fitted at the top of the relay body, the outlets of which are

threaded to take a bleed pipe if required for collection of gas samples.

SILICAGEL BREATHER-:Expansion and contraction of oil cause breathing action. The silicageldehydrating

breather absorbs any humidity in the air breathed. An oil seal in the air intake

prevents external moisture being absorbed when no breathing occurs.

The breather container is filled with silica gel crystals. It is arranged such that the

air breathed must pass through it. The desiccant contains blue and white crystals.

When the silica gel is fully active, the blue crystals will have a deep blue colour

and changes to pink as it absorbs moisture. When saturated with moisture and

the charge contained should be replaced. The gel removed from the breather may

be arranged for regeneration and preserved for future use.

WINDING TEMERATURE INDICATORS-:The winding temperature relay indicates the winding temperature of the

transformer and operates the alarm, trip and cooler control contacts. This

instrument operates on the principle of thermal imaging and it is not an actualmeasurement.

Winding temperature indicator consists of a sensor bulb in oil filled pocket in the

transformer tank cover. The bulb is connected the instrument housing by means

of two flexible capillaries tubes. One capillary is connected to the measuring

bellow of the instrument and the other to a compensation bellow. The measuring

system is filled with a liquid, which changes its volume with rising temperature.

OIL TEMPERATURE INDICATOR-:The oil temperature indicator consist of a sensor bulb, capillary tube and a dial

thermometer, the sensor bulb is fitted at the location of hottest oil. The sensor

bullb and capillary tube are fitted with an evaporation liquid. The vopour pressure

varies with temperature and is transmitted to a bourden tube inside the dial


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thermometer, which moves in accordance with the change in pressure, which is

proportional to the temperature.

BUSHING-:The high voltage connections pass from the windings to terminal bushing.Terminal bushing upto 36 kv class, 3150 amperes, are normally of plain porcielain

and oil communicating type. the oil inside the condenser bushing will not be

communicating with the oil inside transformer.

While connecting the overhead transmission line conductor to the bushing

terminal, ensure that the line pull is limited to the cantilever strength of the

bushing. The cantilever strength of bushing as per IS:

2099 for various types of bushing are as shown below.

Rated voltage

(kv)

Cantilever strength(kg.)

3150 (amps)


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Tap changers of power transformer are specifically of two types-

1.On Load Tap Changer

2.Off Load tap Changer

OFF LOAD TAP CHANGER-:In the case of off load tap changer, tap changing takes only when the transformer

is de-energized. The equipment consists of an operating handle, pointer, a non

corrosive indicator plate and a latch. Taps can be changed by lifting the latch and

turning the handle. The latch will drop into place on the indicator plate when the

new position is reached. A flat and pin that fills into a slotted sleeve on the drive

shaft connects the external mechanism with the internal tap changer. A stuffing

box seals against oil leakage around the operating handle shaft. A pair of heavy

copper bars supported from the operating shaft from the moving contacts. The

stationary contacts are mounted on a bakelite panel with tap leads connected tothem.

The Generating Transformer is OFF-LOAD tap changer.

ON LOAD TAP CHANGER-:ON-LOAD tap changer is the device for changing the tapping connection of a

winding. Whilest the transformer is on load.

The on load tap changer will be a self-contained unit housed in the main

transformer tank. Since some amount of arcing takes place during the switching

operations from one tap to other, the oil inside the tap selector will deterioratedfaster. Hence, this oil cannot be allowed to mix with the oil in the main

transformer. On load tap changer is provided with a separate conservator and oil

surge relay.

The tap changer is operated by a motor operated driving mechanism by local are

remote control and a handle is fitted for manual operation emergency.

The tap changer can be designed for changing the taps.

1. Manually

2. Automatically

3. From remote

INTECONNECTING TRANSFORMER-:It receives the power from the generating transformer at high voltage. It also an

auto-transformer and has delta-star connection. It has three terminal HV, IV and


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LV. HV side is 400kv, IV side is 220kv and IV side is 33kv. The construction are

going to same as generating transformer.

RATINGS-:

Types of cooling - ONAN ONAF OFAFRated power - HV IV LV

(MVA) 189 252 315

63 84 105

Rated voltage - 400 220 33

(KV)

Rated current - 273.12 496.59 1103.52

(A)364.16 662.11 1471.36455.20 827.64 1839.20

Type - Auto transformerVector group - YNd11

Frequency - 50

(HZ)

Insulation level - SI1050 LI950 LI950

(KV) LI1300 AC 38

AC 38 AC 95

No of phase - 3

Core & coil mass - 1,30,000

(kg)Tank & fitting mass - 70,000

Mass of oil - 77,000

Total mass - 2,77,000

Volume of oil - 86,500

Max. temperature - tap oil 50

rise over an *c 55

ambient of 50 *C AVG WDG. 55 55 55

MAX NORM MIN

There are some other transformer are used to drive equipment stabled in power

plant. These transformer are listed below-:

1) Unit auxiliary transformer

2) Station auxiliary transformer


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UNIT AUXILIARY TRANSFORMER-:This is step down transformer with transformation ratio of generator terminal to

unit auxiliary voltage (16.5/6.6kv) with an ON-LOAD tap changer.

STATION AUXILIARY TRANSFORMER-:This is a step down transformer with transformation ratio of grid voltage to the

station auxiliary supply level (220/6.6kv) with ON-LOAD tap changer.

2.BUS BAR-:In the event distribution for a large installation is at higher than generator

voltage, e.g. 34.5 kV, or in the event an interconnection with a local utility is

necessary, a switchyard will be required. The switching structure will be erected

to support the insulators, disconnecting switches, potential and currenttransformer, and the terminations for the generator step-up transformer and

transmission line.

Structure of galvanized steel or aluminum are most often used. Where the switch

yard is located close to ocean, the salt laden atmosphere may be extremely

corrosive to aluminum requiring the use of galvanized steel.

Either copper or aluminum, tubular buses will be employed depending upon the

atmosphere, with aluminum generally begins less expensive. Copper bus

economics will be bolted; aluminum connection must be welded. For isolated oroverseas establishment, only copper buses should be used. A corrosive

atmosphere will preclude the use of aluminum.

3.ISOLATOR-:In electrical engineering , a disconnector or isolator switch is used to make sure that an

electrical circuit can be completely de-energized for service or maintainence . such switches

are often found in electrical distribution and industrial application where machinery must

haveits source of driving power removed for adjustment or repair. High voltage insulation

switch are used in electrical switchyard toallow isolation of apparatus such as circuit

breaker and transformer and transmission line for maintainence.

In switchyard following type isolator are used-:


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1)Sequential L isolator

2)Pantograph isolator

SEQUENTIAL ISOLATOR-:The sequential isolators two post type in which the moving contacts movesthrough 90* on its axis.

PANTOGRAPH ISOLATOR-:

The pantograph isolator has two moving contact arms designed in scissor like fashion, which

move only 20* on its axis. While closing, the linkages of pantograph are brought nearer by

rotating the insulator column. In closed position the upper two arms of the pantograph closed

on the overhead station bus bar giving a grip. The current is carried by upper bus bar to lower

bus bar through the conducting arms of the pantograph. While opening, the rotating insulator


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column is rotated about its axis. Thereby the pantograph blades collapse in in vertical plane

and vertical isolation is obtained between line terminal and pantograph upper terminal.

Pantograph isolators cover less floor area. Each pole can be located at a suitable point and the

three poles need not be one line, can be located in a one line at desired angle with the bus

axis.

RATING-:

Type - PG

voltage (kv) - 420

BIL (kv) - 1425

Switching IMP (kv) - 1050

Pf (kv) - 520/610


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Weight (kg) - 470

STC KA/SEC (IK/TK) - 40KA/ 1SEC

Frequency (hz) - 50

Current (A) - NA

Type of drive - R.G. BOM

Control voltage (DC) - 220 kv

Weight of drive (kg) - 130

Motor voltage (v) - 415

4.EARTH SWITCH-:

Earth switches are devices which are normally used to earth a particular system to avoid any

accident which may happen due to induction on account on live adjoining circuit. These do

not handle any appreciable current.

RATING-:

Type - HCB

voltage (kv) - 420

BIL (kv) - 1425

Switching IMP (kv) - 1050/1145

Pf (kv) - 520/610

Weight (kg) - 780

STC KA/SEC (IK/TK) - 40KA/ 1SEC

Frequency (hz) - 50

Current (A) - NA

Type of drive - R.G. BOM

Control voltage (DC) - 220 kv

Weight of drive (kg) - 40


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5.CIRCUIT BREAKER-:

A circuit breaker is automatically operated electrical switch designed to protect an electrical

circuit from damaged caused by overload or short circuit. Its basic function is to detect the

fault condition and, by interrupting continuity, to immediately discontinue electrical flow.

Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset(either manually or automatically)to resume normal operation. Circuit breaker are made in

varying sizes, from small device that protect an household appliance up to large switch gear

designed to protect high voltage circuits feeding an entire city. Once a fault is detected,

contacts within the circuit breaker must open to interrupt the circuit, some mechanically-

stored energy contain within the breaker is used to separate the contacts, although some of

the energy required may be obtained from the fault current itself. small circuit breaker may

be manually operated, larger units have solenoids to the trip mechanism, and electric motor

to restore energy of the springs.

The circuit breaker contacts must carry the lad currents without excessive heating, and must

also withstand the heat of the arc produced when interrupting the circuit. Contacts are made

of copper or copper alloys, silver alloys and other materials. When a current is interrupted, an

arc is generated. This arc may be contained, cooled and extinguished in a controlled way, so


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that the gap between the contacts can again withstand the voltage in the circuit. Different

circuit breaker is use vacuum, air, insulating gas or oil as the medium in which the arc forms.

TYPES OF CIRCUIT BRAEKER-:

High voltage breaker are nearly always solenoid operated, with the current sensing protective

relays operated through current transformers.

High voltage breaker are broadly classified by the medium used to extinguish the arc.

1) Bulk oil

2) Minimum oil

3) Ail blast

4) Vacuum

5) Sf6

In switchyard only sf6 circuit breaker is used. The breaker uses sf6 (sulpher-hexa fluoride) for

extinction purpose. The gas has an excellent current interrupting and insulating properties,

chemically, it is one of the most stable compound in the pure state and under normal

condition it is physically inert, non-flammable, non-toxic and odor less and there is no danger.

Sf6 breaker called as maintenance free breaker, has simple construction with few moving

parts:


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The fission products created during breaking and not fully recombined are, either precipitated

as metallic fluoride or absorbed by a static filter which also absorbs the residual moisture.

Since no gas is exhausted from the breaker and very little compressed air is required for

operation. Since sf6 gas is inert and stable at normal temperature, contacts do not settler from

oxidization or other chemical reaction, where in oil or air type breakers oxidation of contacts

would cause high temperature rise.

During the arcing period sf6 is blown axially along the arc. The gas removes the heat from the

arc by axial convection and radial dissipation. As a result, the arc diameter reduces during the

decreasing mode of the current wave. The diameter becomes small during the current zero

and the arc extinguished. Due to its electro negativity, and low arc time constant, the sf6 gas

regains its dielectric strength rapidly after the current zero, the rate of rise of dielectric strength

is very high and the time constant is very small.

RATING OF SF6 CIRCUIT BREAKER-:

Company name - AREVA

Type - GL 316

Rated voltage (KV) - 420

Normal current (A) - 2000

Frequency (HZ) - 50Voltage across openContact (KV rms) - 610

to earth (KV rms) - 520

Lightening impulse with Stand v (KVp) - 1425

Switching surge withstand v (KVp) - 1050

First pole to clear factor - 1.3

Short time withstand current (KA) - 40

Duration of short circuit (S) - 0 1

Short circuit breaking current

Symmetrical (KA) - 40

Asymmetrical (KA) - 49


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Short circuit making current (KVAp) -100

Out of phase breaking current (KArms) -10

Operating sequence - 0-0.3 S - W3 min - W

Line charging breaking current (A) - 600

Sf6 has pressure at 20*c , 1013hpa - 0 8.5

(MPa)

6.LIGHTENING ARRESTOR-:High voltage power system experiences overvoltage that arise due to natural lightening or the

inevitable switching operation. Under these overvoltage conditions, the insulation of the

power system equipment are subjected to electrical stress which may lead to catastrophic

failure.


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Broadly, three type of over-voltages occure in power system :

1) Temporary over-voltage

2) Switching over-voltage

3) Lightening over-voltage

The duration of three over-voltages vary in the range of microseconds to sec depending upon

the type and nature of over-voltages.

Conventionally, the over-voltageprotection is obtain by the use of lightening/ surge arrestors.

Under normal operating voltages, the impedance of lightening arrestor, placed in the parallel

to the equipment to be protected, is very high and allow the equipment to perform its

respective function. Whenever the over voltage appears across the terminals, the impedance

of the arrestor collapses in such a way that the power system equipment would not

experiences the over-voltage. As soon the overvoltage disappears, the arrestor recovers its

impedance back. Thus the arrestor protects the equipment from the over-voltage.

7.CURRENT TRANSFORMER-:

Current transformer (CT) are instrument transformer that are used to supply a reduced of

current to meters, protective relays, and other instruments. CTs provide isolation from high

voltage primary, permit grounding to the secondary for safety, and step-down the magnitude

of the measured current to a value that can be safely handled by the instruments.

TYPE-:

1)The CTs shall be of ring type or window type.

2)The secondary leads shall be terminated within with copper rose contact terminals with

arrange for sealing purpose.

3)Polarity (both for primary and secondary lead) shall be marked.4)The CT shall be varnished, fiberglass tape insulated or cast resin, air cooled type. only super

enameled electrolytic grade copper wires shall be used.


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TECHNICAL DETAIL-:

1 Higher system voltage KV 245

2 Short time current KA 40 for 3 sec

3 Frequency HZ 50

4 Insulation level KV/KVp 460/1050

5 Class of accuracy 0.5

6 Supply system 3ph solidly grounded neutral system


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8.CAPACITOR VOLTAGE TRANSFORMER-:

In high and extra high voltage transmission system, capacitor voltage transformers (CVTs) are

used to provide potential outputs to metering instruments and protective relays. In addition,

when equipped with carrier accessories, CVT can used for power line carrier (PLC) coupling.

A capacitive voltage transformer (CVT) is a transformer used in power system to step down

extra high voltage signals and provide low voltage signals either for measurement or to

operate a protective relay. In the most basic form the device consists three main part :

Two capacitors across which the voltage signal is split, and inductive element is used to tune

the device to the supply frequency and a transformer used to isolate and further step down

the voltage for instrumentation or protective relay. The device has at least four terminals, a

high voltage terminals for connection of high voltage signal, a ground terminal and at least one

set of secondary terminals for connection to the instrumentation or protective relay. CVTs are

typically single phase device used for measuring voltage in excess of on hundred kilovolts

where the use of voltage transformers would be uneconomical. In practice the first capacitor,

C1, is often replaced by a stack of capacitor connected in series. This result a large voltage drop

across the stack of capacitors that replaced the first capacitor and a comparatively small

voltage drop across the second capacitor, C2, and hence the secondary terminals.


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INSULATING SYSTEM-:

The external insulation is provided by the porcielain housing and co-ordinated

with the capacitor stack, consisting of virtually identical so that the axial voltage

distribution from the line terminal to the ground is essentially uniform. Thecapacitor elements have a mixed dielectric material consisting of alternative layer

of propylene film and kraft paper. The electromagnetic unit is housed in an oil-

filled tank at the base of capacitor stack. Mineral oil is used as the insulating

medium instead of air because of its superior insulating and heat transfer

properties. The use of an oil-filled base tank remove the need for space heater in

the secondary terminal. This result more reliable and cost effective design.

INSULATIG OIL-:

We use insulating oil with excellent dielectric strength, aging, and gas absorbing

properties. The synthetic oil is used for the capacitor units possesses superior gas

absorption properties resulting in exceptionally low partial discharge with high

inception voltage ratings. The oil is used for EMU is premium naphthenic mineral

oil. The oil is filtered, vacuum dried and degassed within house processing. It

contains no PCB.

CAPACITOR STACK-:

The capacitor stack is a voltage divider which provides a reduced voltage at the

intermediate voltage bushing for a given voltage applied at the primary terminal.

the capacitor stack is a multi-capacitor unit assembly. Each unit is housed in an

individual insulator and is fitted with an aluminum. A cast aluminum covers in the

top of the upper capacitor assembly and is fitted with an aluminum terminal. an

adapter for mounting a line trap on the top of the CVT can be provide with an

optional HV terminal. the capacitor units are mechanically coupled together by

means of stain less steel hardware passing through the corrosion resistant castaluminum housing. The mechanical connection also establishes the electrical

connection between capacitor units.

There are some part of capacitor voltage transformer-:

1)Primary terminal 11) Ferro-resonance subpression device


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2)Cats aluminum bellow housing 12)Secondry terminals

3)Stainless steel expansion bellow 13) Oil level sight glass

4)Compression spring 14)Aluminum terminal box

5)Insulated voltage connection 15)Immediate transformer

6)Capacitor elements 16)Oil/air block

7)Insulator 17) Oil sampling device

8)Voltage divider tap connection 18)Compansating reactor

9)Cast epoxy bushing 19)Aluminum cover plate

10)HF terminal connection


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1)High voltage terminal

2)Compensation reactor

3)Intermediate voltage transformer

4)Ground terminal

5)Ferro resonance subpression device

6)Damping resistor7)Carrier terminal

8)Over voltage protective device

9)Secondry terminals

10)Link


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9.WAVE TRAP-:

Line trap also known as wave trap.What it does is trapping the high frequency

communicationsignals sent on the line from the remote substation and diverting

them to the telecom/teleportation panel in the switchyard control room(throughcoupling capacitor and LMU).This is relevant in Power Line Carrier Communication

(PLCC)systems for communication among various switchyard without dependence

on the telecom company network. The signals areprimarilly teleportation signal

and in addtion,voice and data communication signals.

The Line trap offers high impedance to the high frequency communication signals

thus obstructs the flow of these signals in to the substation busbars. If there were

not to be there, then signal loss is more and communication will be

ineffective/probably impossible.

CONSTRUCTION-:

MAIN COIL-:

The main coil winding are encapsulated by winding continuous filament

fiberglass. That has been impregnated with a specially selected epoxy resinharden

system. Theepoxy resinfiberglass composite is then curve according to

a programmed temperature schedule.

TUNING PACK-:

Tuning pack is connected in parallel with the main coil to provide a

highimpedance to the desired carrier frequency.

LIGHTENING ARRESTORS-:The line traps are protected by a lighting arrestors against high voltage

surgescaused by atmospheric effects or switching operations.


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CKT DIAGRAM OF WAVETRAP-:


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RESPONSE OFF WAVETRAP-:

10.PROTECTIVE RELAYS-:

Protective relaying is one of the several features of power system design. Everypart of the power system is protected. The protecting relaying is used to give an

alarm or to cause prompt removal of any element from power system from

service when that elements behave abnormally.

The relays are compact and self-contained devices which can sense abnormal

conditions. Whenever abnormal condition occur, the relay contacts get closed this

is turn closes the trip circuit of circuit breaker.

For switchyard protection following types relays are used-:

1) Overcurrent relay

2) Earth fault relay

3)REF relay

4) Differential relay


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5) Directional relay

6) Over flux relay

7) Buchholz relay

8) IDMT relay

RESTRICTED EARTH FAULT PROTECTION RELAY-:

The REF protection method is a type of "unit protection" applied to transformers

or generators andis more sensitive than the method known as differential

protection.

An REF relay works by measuring the actual current flowing to earth from the

frame of the unit. If that current exceeds a certain preset maximum value of

milliamps (mA) then the relay will trip tocut off the power supply to the unit.

DIFFERENTIAL RELAY-:

Differential protection can also be used to protect the windings of a transformer

by comparing thecurrent in the power supply's neutral wire with the current

in the phase wire. If the currents areequal then the differential protection relay

will not operate. If there is a current imbalance then thedifferential protection

relay operates.

REF protection is applied on transformers in order to detect ground faults on a

given winding moresensitively than differential protection.

DIRECTIONAL RELAY-:

Directional relays have protection zones that include all of the power system

situated in only onedirection from the relay location. (This is in contrast to

magnitude relays which are not directional, i.e., they trip based simply on themagnitude of the relay.

IDMT RELAY-:

The IDMT relay work on the induction principle, where an aluminum or copper

disc rotatesbetween the poles of electromagnet and damping magnet. The fluxes


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induce eddy current in thedisc which interact and produce rotational torque. The

disc rotates to a point where it operates apair of contact that breaks the circuit

and removes the fault condition.

11.CORONA RING-:A corona ring, also called anti-corona ring, is a toroid of (typically) conductive

material located inthe vicinity of a terminal of a high voltage device. It is

electrically insulated. Stacks of more spacedrings are often used. The role of the

corona ring is to distribute the electric field gradient and lower its maximum

values below the corona threshold, preventing the corona dischargeCorona

rings are typically installed on very high voltage power line insulators.

Manufacturerssuggest a corona ring on the line end of the insulator for above

230 kV and on both ends for above500 kV. Corona rings prolong lifetime of

insulator surfaces by suppressing the effects of coronadischarge.

CORONA RING

12.SCADA SYSTEM OF UPRVUNL-:In SCADA system measured values, i.e. analogue (measured value) data (MW,

MVAR, V, HZ Transformer Tap Position), and open/closed status information, i.e.

digital data (circuit breaker/isolator position i.e. on/off status), are transmitted

through telecommunication channels to respective sub-LCDs. For this purpose

remote terminal units at 400kv and 220kv have been installed. System values


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&status information below132 KV have not been picked up for data transmission,

except for 33KV Bus isolator position andLV side of generators. Secondary

side of Current Transformers (CT) and Potential transformer(PT) are

connected with 'Transducers'. The output of transducers is available in dc current

form (inthe range of 4mA to 20mA). Analogue to digital converter converts thiscurrent into binary pulses. Different inputs are interleaved in a sequential

form and are fed into the CPU of the RTU. The output of RTU, containing

information in the form of digital pulses, is sent to subLDC through

communication links. Depending upon the type of communication link,

the output of RTU is connected, directely or through modem, with the

communication equipment. At subLDC end, data received from RTU is fed into the

data servers. In general, a SCADA system consists of a database, displays and

supporting programmes.In UPRVUNL,subLDCs use all major functional

areas of SCADA except the 'Supervisory Control/Command' function. The briefoverview of major'functional areas' of SCADA system is as below:

1. COMMUNICATION-:

Sub LCDs computer communities with all RTU station under its control, through

a communication system. RTU polling, message formatting,

polynomialchecking and message retransmission on failure are the

activities of 'Communications' functional area.

2) DATA PROCESSING-:After receipt of data through communication system it is processed. Data

process function has three sub-functions i.e.

i) Measurements

ii) Counters

iii) Indications

i)'Measurements retrieved from a RTU are converted

to engineering units and linearized , if necessary. The measurement arethen placed in database and are checked against variouslimits which if exceeded

generate high or low limit alarms.


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i i )The system has been set-up to col lect 'Counters ' at regular

in ter val s: ty pic all y 5 or 10minutes. At the end of the hour the units is

transferred into appropriate hour slot in a 24-hour archive/history.

iii) Indications' are associated with status changes and protection. For thosestatuses that arenot classified as 'alarms', logs the change on the appropriate

printer and also enter it into acyclic event list. For those statuses, which are

defined as an 'alarms' and the indicationgoes into alarm, an entry is made

into the appropriate alarm list, as well as in the event list. For those statuses,

which are defined as an 'alarms' and the indicationgoes into alarm, an

entry is made into the appropriate alarm list, as well as in the event listand

anaudible alarm is generated in the sub-LDC.

ALARM/EVENT LOGGING-:The alarm and event logging facilities are used by SCADA dataprocessing

system. Alarms are grouped into different categories and are given

differentpriorities. Quality codes are assigned to the recently received

data for any 'limit violation'and 'status changes'. Alarms are acknowledged

from single line diagram (or alarm lists) ondisplay terminal in LDCs

MANUAL ENTRY-:There is a provision of manual entry of measured values, counters

andindications for the important sub-station/powerhouse, which are

uncovered by an RTU or some problem is going on in its RTU, equipment,

communication path, etc.

AVERAGE OF MEASURED VALUES-:As an option, the SCADA system supports averaging of all analogue

measurements. Typically, the averaging of measured values over a period of 15

minutes is stored to provide 24 hours trend.

HISTORICAL DATA STORAGE (HDR)-:The HDR, i.e. 'archive', subsystem maintains a historyof selected system

parameters over a period of time. These are sampled at a pre-selectedinterval

and are placed in historical database. At the end of the day, the data is

saved for later analysis and for report generation.


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INTERACTIVE DATA GRNERATION-:Facilities have been provided in such a way that an off-line copy of the

SCADA database can be modi f ied a l lowing the add i t ion of new

RTUs,pickup points and communication channels.

SUPERVISORY CONTROL/REMOTE COMMAND-:This function enables the issue ofremotecontrol commands to the switchyard

equipment e.g. circuit breaker command.

FAIL-OVER -:A 'Fail-over' subsystem is also provided to secure and maintain a

database ofdevices and their backups. The state of the device is maintainedindicating whether it is 'on-line' or 'failed'. There is a 'backup' system, which

maintains database on a backup computer and the system is duplicated.


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project report by manish yadav

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