This document provides information about batteries, inverters, and the difference between alternating current (AC) and direct current (DC). It discusses how inverters work by using electromagnetic switches to rapidly reverse the direction of current from a DC source, producing an AC output. Batteries can be connected in series or parallel configurations to an inverter, with series increasing voltage and parallel increasing capacity. Early inverters used mechanical components like motors and generators to convert between AC and DC, while modern inverters are electronic devices that switch DC rapidly to produce AC.

1. INDUSTRIAL TRAINING REPORT
ON
BATTERIES & INVERTERS
ELECTRICAL ENGINEERING DEPARTMENT

2. INDEX
Chapter Title Page
1.0 INTRODUCTION 3
2.0 DIFFERENCE BETWEEN AC AND DC 4
3.0 WHAT IS AN INVERTER 6
4.0 How does an inverter work? 8
5.0 Batteries 11
6.0 Working 13

3. INTRODUCTION
One of the mostsignificantbattlesof the 19thcenturywas foughtnotoverlandor resourcesbutto
establishthe type of electricitythatpowersourbuildings.Atthe veryendof the 1800s, American
electrical pioneerThomasEdison(1847–1931) wentout of hisway to demonstrate thatdirectcurrent
(DC) was a betterwayto supplyelectrical powerthanalternatingcurrent(AC),asystembackedbyhis
Serbian-bornarch-rivalNikolaTesla(1856–1943). Edisontriedall kindsof deviouswaystoconvince
people thatACwas toodangerous,fromelectrocutinganelephantto(rathercunningly) supportingthe
use of ACin the electricchairforadministeringthe deathpenalty.Evenso,Tesla'ssystemwonthe day
and the worldhas prettymuchrun on ACpowereversince.The onlytrouble is,thoughmanyof our
appliancesare designedtoworkwithAC,small- scale powergeneratorsoftenproduce DC.Thatmeansif
youwant to run somethinglikeanAC- poweredgadgetfromaDC car batteryina mobile home,you
needa device thatwill convertDCtoAC—aninverter,asit'scalled.
DIFFERENCE BETWEEN AC AND DC
Whenscience teachersexplainthe basicideaof electricitytousas a flow of electrons,they're usually
talkingaboutdirectcurrent(DC).We learnthat the electronsworka bitlike a line of ants,marching
alongwithpacketsof electrical energyinthe same waythatants carry leaves.That'sa good enough
analogyforsomethinglike abasicflashlight,where we have acircuit(an unbrokenelectrical loop)linking
a battery,a lamp,and a switchand electrical energyissystematicallytransportedfromthe batterytothe
lampuntil all the battery'senergyisdepleted.Inbiggerhouseholdappliances,electricityworksa
differentway.The powersupplythatcomesfromthe outletinyourwall isbasedonalternatingcurrent
(AC),where the electricityswitchesdirectionaround50–60 timeseachsecond(inotherwords,at a
frequencyof 50–60 Hz). It can be hard to understandhow ACdeliversenergywhenit'sconstantly
changingitsmindaboutwhere it'sgoing!If the electronscomingoutof yourwall outletget,let'ssay,a
fewmillimetredownthe cable thenhave toreverse directionandgobackagain,how dotheyevergetto
the lampon your table tomake it lightup?The answerisquite simple.Imaginethe cablesrunning
betweenthe lampandthe wall packedfull of electrons.Whenyouflickonthe switch,all the electrons
fillingthe cablevibrate backandforthin the lamp'sfilament—andthatrapidshufflingaboutconverts

4. electrical energyintoheatandmakesthe lampbulbglow.The electronsdon'tnecessarilyhave torunin
circle to transportenergy:inAC,theysimply"runonthe spot."
WHAT ISAN INVERTER
Basically,apowerinverter,orinverter,isanelectronicdevice orcircuitrythatchangesdirect current
(DC) to alternate current(AC).
Directcurrent (DC) isthe unidirectionalflow of electriccharge.Directcurrentisproducedbysources
such as batteries,powersupplies,thermocouples,solarcells,ordynamos.Directcurrentmayflowina
conductorsuch as a wire,butcan alsoflow throughsemiconductors,insulators,oreventhrougha
vacuumas in electronorionbeams.The electriccurrentflowsin aconstant direction,distinguishingit
fromalternatingcurrent(AC).A termformerlyusedforthistype of currentwas galvaniccurrent.
Alternatingcurrent(AC),isanelectriccurrentinwhichthe flow of electriccharge periodicallyreverses
direction,whereasindirectcurrent(DC,alsodc),the flow of electriccharge isonlyinone direction.The
abbreviationsACandDCare oftenusedtomeansimplyalternatinganddirect,aswhentheymodify
currentor voltage.The inputvoltage,outputvoltage and frequency,andoverallpowerhandlingdepend
on the designof the specificdeviceorcircuitry.The inverterdoesnotproduce anypower;the poweris
providedbythe DC source.A powerinvertercanbe entirelyelectronicormay be a combinationof
mechanical effects(suchasarotary apparatus) and electroniccircuitry.Staticinvertersdonotuse
movingpartsin the conversionprocess.Aninverterdoesthe opposite jobandit'squite easyto
understandthe essence of howitworks.Suppose youhave abatteryina flashlightandthe switchis
closedsoDC flowsaroundthe circuit,alwaysinthe same direction,like arace car arounda track. Now
whatif youtake the batteryoutand turn itaround.Assumingitfitsthe otherway,it'll almostcertainly
still powerthe flashlightandyouwon'tnotice anydifference inthe lightyouget—butthe electric
currentwill actuallybe flowingthe oppositeway.Suppose youhadlightning-fasthandsandwere deft
enoughtokeepreversingthe battery50–60 timesasecond. You'd thenbe a kindof mechanical inverter,
turningthe battery'sDC powerintoACat a frequency of 50–60 hertz.Of course the kindof invertersyou
buyin electrical storesdon'tworkquite thisway,thoughsome are indeedmechanical:theyuse
electromagneticswitchesthatflickonandoff at highspeedtoreverse the currentdirection.Inverters
like thisoftenproduce what'sknownasa square- wave output:the currentiseitherflowingone wayor
the opposite wayorit's instantlyswappingoverbetween the twostates
Howdoes an inverterwork?

5. Imagine you're aDC batteryandsomeone tapsyouon the shoulderandasksyouto produce AC instead.
How wouldyoudoit? If all the current youproduce flowsoutinone direction,whataboutaddinga
simple switchtoyouroutputlead?Switchingyourcurrentonandoff,veryrapidly,wouldgive pulsesof
directcurrent—whichwoulddoatleasthalf the job.To make properAC, you'dneeda switchthat
allowedyoutoreverse the currentcompletelyanddoitabout50‐60 timeseverysecond.Visualize
yourself asa humanbatteryswappingyourcontactsback and forth over3000 timesa minute.That's
some neatfingerworkyou'dneed!
In essence,anold-fashionedmechanicalinverterboilsdowntoa switchingunitconnectedtoan
electricitytransformer.If you've studiedourarticle on transformers,you'llknow that
they're electromagneticdevicesthatchange low-voltage ACtohigh-voltage AC,orvice-versa,usingtwo
coilsof wire (calledthe primaryandsecondary) woundaroundacommonironcore. Ina mechanical
inverter,eitheranelectricmotororsome otherkindof automatedswitchingmechanismflipsthe
incomingdirectcurrentbackand forthin the primary,simplybyreversingthe contacts,andthat
producesalternatingcurrentinthe secondary—soit'snotso verydifferentfromthe imaginaryinverterI
sketchedoutabove.The switchingdevice worksabitlike the one inan electricdoorbell.Whenthe
powerisconnected,itmagnetizesthe switch,pullingitopenandswitchingitoff very
briefly.A springpullsthe switchbackintoposition,turningitonagainandrepeatingthe process—over
and overagain.
The basic conceptof an electromechanicalinverter.DCfeedsintothe primarywinding(pinkzig-zag
wiresonthe leftside) of atoroidal transformer(browndonut),throughaspinningplate(redandblue)
withcriss-crossconnections.Asthe plate rotates, itrepeatedlyswitchesoverthe connectionstothe
primarywinding,sothe transformerisreceivingACasitsinputinsteadof DC. Thisisa step-up
transformerwithmore windingsinthe secondary(yellowzig-zag,right-handside) thanthe primary,soit
boostsa small ACinputvoltage intoa largerAC output.The speedatwhichthe diskrotatesgovernsthe
frequencyof the ACoutput.Most invertersdon'tworkanythinglike this;thissimplyillustratesthe
concept.Aninvertersetupthisway wouldproduce averyrough square wave output.

6. Batteries
The runtime of an inverterisdependentonthe batterypowerandthe amountof powerbeingdrawn
fromthe inverterata giventime.Asthe amountof equipmentusingthe inverterincreases,the runtime
will decrease.Inordertoprolongthe runtime of aninverter,additional batteriescanbe addedtothe
inverter.Whenattemptingtoaddmore batteriestoan inverter,there are twobasicoptionsfor
installation:SeriesConfigurationandParallel Configuration.
Seriesconfiguration:If the goal isto increase the overall voltageof the inverter,one candaisychain
batteriesinaSeriesConfiguration.InaSeriesConfiguration,if asingle batterydies,the otherby
batterieswill notbe able topowerthe load.
Parallel configuration:If the goal isto increase capacityandprolongthe runtime of the inverter,
batteriescanbe connectedinparallel.Thisincreasesthe overallAmperehour(Ah) ratingof the battery
set.If a single batteryisdischargedthough, the otherbatterieswill thendischarge throughit.Thiscan
leadto rapiddischarge of the entire pack,or evenanover-currentandpossible fire.Toavoidthis,large
paralleledbatteriesmaybe connectedviadiodesorintelligentmonitoringwithautomaticswitchingto
isolate anunder-voltage batteryfromthe others.
Early batteries

7. Early invertersFromthe late nineteenthcenturythroughthe middle of the twentiethcentury,DC-to- AC
powerconversionwasaccomplishedusingrotaryconvertersormotorgeneratorsets(M-G sets).Inthe
earlytwentiethcentury,vacuumtubesandgasfilledtubesbegantobe usedasswitchesininverter
circuits.The most widelyusedtypeof tube wasthe thyratron.The originsof electromechanical inverters
explainthe source of the terminverter.EarlyAC-to-DCconvertersusedaninductionorsynchronousAC
motor direct-connectedtoagenerator(dynamo) sothatthe generator'scommutatorreversedits
connectionsatexactlythe rightmomentstoproduce DC.A laterdevelopment isthe synchronous
converter,inwhichthe motorand generatorwindingsare combinedintoone armature,withslipringsat
one endand a commutatorat the otherand onlyone fieldframe.The resultwitheitherisAC-in,DC-out.
Withan M-G set,the DC can be consideredtobe separatelygeneratedfromthe AC;withasynchronous
converter,ina certainsense itcan be consideredtobe "mechanicallyrectifiedAC".Giventhe right
auxiliaryandcontrol equipment,anM-Gset or rotary convertercanbe "runbackwards",convertingDC
to AC.Hence an inverterisan invertedconverter.
Working
Whenthe sulfuricaciddissolves,itsmoleculesbreakupintopositivehydrogenions(2H+) andsulphate
negative ions(SO4—) andmove freely.If the twoelectrodesare immersedinsolutionsandconnectedto
DC supplythenthe hydrogenionsbeingpositivelychargedandmovedtowardsthe electrodesand
connectedtothe negative terminal of the supply.The SO4— ionsbeingnegativelychargedmoved
towardsthe electrodesconnectedtothe positive terminal of the supplymain(i.e.,anode).
Each hydrogeniontakesone electronfromthe cathode,andeachsulphatesionstakesthe twonegative
ionsfromthe anodesand react withwaterandform sulfuricandhydrogenacid.
The oxygen,whichproducedfromthe above equationreactwithleadoxide andformleadperoxide
(PbO2.) Thus,duringchargingthe leadcathode remainaslead,butleadanode getsconvertedintolead
peroxide,chocolate incolour.

8. If the DC source of supplyisdisconnectedandif the voltmeterconnectsbetweenthe electrodes,itwill
showthe potential difference betweenthem.If wire connectsthe electrodes,thencurrentwill flowfrom
the positive plate tothe negative platethroughexternal circuiti.e.the cell iscapable of supplying
electrical energy.
Discharging
Whenthe cell isfull discharge,thenthe anode isof leadperoxide(PbO2) andacathode isof metallic
sponge lead(Pb).Whenthe electrodesare connectedthrougha resistance, the cell discharge and
electronsflowinadirectionoppositetothatduringcharging.
The hydrogenionsmove tothe anode and reachingthe anodesreceive one electronfromthe anode and
become hydrogenatom.The hydrogenatomcomesincontactswitha PbO2,so itattacks and formslead
sulphate (PbSO4),whitishincolourandwateraccordingto the chemical equation.
The each sulphate ion(SO4—) movestowardsthe cathode andreachingthere givesuptwoelectrons
becomesradical SO4,attack the metallicleadcathode andformleadsulphate whitishincolour
accordingto the chemical equation.
Recharging
For recharging,the anode andcathode are connectedtothe positive andthe negative terminalof the DC
supplymains.The moleculesof the sulfuricacidbreakupintoionsof 2H+ and SO4—.The hydrogenions
beingpositivelychargedmovedtowardsthe cathodesandreceivetwoelectronsfromthere andforma
hydrogenatom.The hydrogenatomreacts withleadsulphate cathode formingleadandsulfuricacid
accordingto the chemical equation.

9. Battery making processs
BERFOR START WITH BATTERY MAKING PROCESS,
LETS US DISCUSS WHAT ARE THE MAIN Construction of Lead Acid Battery
 POSITIVEPLATE
 NEGATIVEPLATE
 POLYMER SEPARATER
 SULFURIC ACID
 CONTAINER& BatteryTerminals

10. POSITIVEPLATEFORMATION
Positive plate reaction
PbO2(s) + HSO−
4(aq) + 3H+
(aq) + 2e− → PbSO4(s) + 2H2O(l)
1) OXIDE PROCESS
Lead oxide is obtained by masses of lead from melting furnaces either by Milling or Barton Pot
process methods. In the milling process, the tumbling action generated by the rotating mill on
solid lead generates heat and then the surface of the lead gets oxidized. The surface layers of the
oxide are removed while the lead particles roll in the drum. In Barton Pot process a fine stream of
lead droplets is produced by blowing air on molten lead. These droplets are reacted with oxygen
and produce lead oxide.
GRID CASTING
Grid productionand parts casting involves book casting,
continuouscasting, and strip casting. In all of these processes,

11. lead pigs are melted down and the molten lead is poured into
molds or continuouslycast into grids, strips, or parts. Expanded
metal grid productioninvolves mechanicaloperationson the
cast strip and is not a source of airborne lead dust or oxide. The
major source of lead exposure in this process is from lead
fumes and lead oxide which can become easily airborne.
Electric Lead Melting Furnace
 Low-antimony-lead alloy has been generally used as a grid material for lead/acid batteries

12. 120 BAR PRESSURE ON LOW ATIMONY LEAD ALLOY
Hydraulic Pressure Die Casting Machine
Grid MouldFor Batteries

13. POLYESTER FABARIC
Polyester fabric trimmed accordingly ,put over them
 ACTIVE MATERIAL- The material in a cell which takes active participation in a
chemical reaction (absorption or evolution of electrical energy) during charging or

14. discharging is called the active material of the cell. The active elements of the lead acid
are
LEAD DIOXIDE
Lead peroxide (PbO2) – It forms the positive active material. The PbO2 are dark chocolate
broom in colour.
 CONDUCTIONG MATERIAL - The materials which conduct electricity due to free
electrons when an electric potential difference is applied across them are known as
conducting materials
acetylene black carbon
 BINDER- a substance used to make other substances or materials stick or mix together.
PVDF (Polyvinylidene fluoride)
NMP
DMF
PASTE MIXING FOR POSITIVE PLATE
 60% GREY OXIDE(PbO)
 40%RED LED
 SUFLURIC ACID
 WATER
Additives Accelerating the Formation of the Positive
Plates
Positive plates need much more time to form than negatives. The reason for this is the dielectric behavior
of the cured positive paste. Oxidation of the bivalent lead compounds in the paste and formation of the
PbO2-positive active mass passes through a number of chemical reactions, some of which proceed at a
low rate,which retards the technological process of formation of the positive plate. In an attempt to
accelerate the formation process, additives to the positive paste have been looked for, which are
characterized by electroconductive properties and stability in sulfuric acid. These additives create an
electroconductive network in the paste and the process of oxidation proceeds simultaneously within a
large paste volume, thus accelerating plate formation.

15. Three basic types of additives that shorten the time for formation of positive plates are currently used in
the battery manufacturing practice. The effect of these additives can be summarized as follows:
1.Additives with electron conductivity. These are mostly fibers and powder particles which are in contact
with each other or with the electroconductive PbO2 zone in the paste and thus conduct the current into the
plate interior, thereby increasing the surface on which the reactions of formation proceed.
2.Additives that oxidize PbO to PbO2 and thus create electroconductive zones in the paste,again
increasing the reaction surface for the formation processes.
3.Red lead (Pb3O4) is added as paste component. On soaking and formation of the plates, Pb3O4 reacts
with H2SO4 producing PbO2 and PbSO4. The PbO2 formed contributes to the conductivity of the paste
and thus accelerates the formation process.
PASTING AND CURING
Manufacturersconsiderthe pastingmaterial asa trade secret,andtherefore notrevealthis to public.
However,thispaste material ingeneralismade withoxideof lead,redlead,litharge,wateranddilutes
sulphuricacid.These pastesare usedtofill the grids,i.e.,positiveandnegativegrids;but,forboth,the
pastesare notexactlyfilledwiththe same material,some expandermaterialsare addedformaking
negative paste.

16. The paste isthenforcedor pressedonthe intersticesof the gridsbya machine or byhand,and then
these are turnedas plates.These pastedplatesare curedinovensundercertainconditionsof
temperature near32 degree centigrade forabout48 hours,withhumiditynearingabout90 percentand
are finallyallowedtodryconditionatambienttemperatures.
Homogeneity of the paste. It depends on the technology of paste preparation and on the design
and technical characteristics of the paste mixer, i.e., its capability to mix uniformly the paste
throughout its volume.
Curing of the positive paste is the most time consuming technological procedure in the process
of lead‐ acid battery manufacture. During curing the following processes take place: Pb
oxidation, and oxide recrystallization, grid corrosion, improvement of the paste/grid contact, and
drying of the plate.
NEGATIVE PLATE FORMATION
Negative plate reaction
Pb(s) + HSO−
4(aq) → PbSO4(s) + H+
(aq) + 2e−

17. GRID CASTING
Grid productionand parts casting involves book casting,
continuouscasting, and strip casting. In all of these processes,
lead pigs are melted down and the molten lead is poured into
molds or continuouslycast into grids, strips, or parts. Expanded
metal grid productioninvolves mechanicaloperationson the
cast strip and is not a source of airborne lead dust or oxide. The
major source of lead exposure in this process is from lead
fumes and lead oxide which can become easily airborne.
Electric Lead Melting Furnace

18.  Low-antimony-lead alloy has been generally used as a grid material for lead/acid batteries
120 BAR PRESSURE ON LOW ATIMONY LEAD ALLOY
Hydraulic Pressure Die Casting Machine

19. Grid MouldFor Batteries

20.  ACTIVE MATERIAL- The material in a cell which takes active participation in a
chemical reaction (absorption or evolution of electrical energy) during charging or
discharging is called the active material of the cell. The active elements of the lead acid
are
LEAD
Sponge lead – Its form the negative active material. It is grey in colour.
 CONDUCTIONG MATERIAL - The materials which conduct electricity due to free
electrons when an electric potential difference is applied across them are known as
conducting materials
acetylene black carbon
 BINDER- a substance used to make other substances or materials stick or mix together.
PVDF (Polyvinylidene fluoride)
NMP
DMF
PASTE MIXING FOR NEGATIVE PLATE

21.  GREY OXIDE(PbO)
 ACRYLIC FIBER
 SUFLURIC ACID
 CARBON BLACK
 BARIUM SULFATE
 expander materials
PERFECTLY COMPLEMENTARY TO THE POSITIVE PLATE
SPRTING OF SULFURIC ACID
THIN FILM OF LEAD SUFLATE WHICH PRESSURE INHERNT THE MOISTURE TO
EVAPORATE SAFEGUARDING THE PLATS FROM CRACKING
PASTING AND CURING
Manufacturersconsiderthe pastingmaterial asa trade secret,andtherefore notrevealthisto public.
However,thispaste material ingeneralismade withoxideof lead,redlead,litharge,wateranddilutes
sulphuricacid.These pastesare usedtofill the grids,i.e.,positiveandnegativegrids;but,forboth,the
pastesare notexactlyfilledwiththe same material,some expandermaterialsare addedformaking
negative paste.
The paste isthenforcedor pressedonthe intersticesof the gridsbya machine or byhand,and then
these are turnedas plates.These pastedplatesare curedinovensundercertainconditionsof

22. temperature near32 degree centigrade forabout48 hours,withhumiditynearingabout90 percentand
are finallyallowedtodry conditionatambienttemperatures.
Homogeneity of the paste. It depends on the technology of paste preparation and on the design
and technical characteristics of the paste mixer, i.e., its capability to mix uniformly the paste
throughout its volume. and drying of the plate.
Separators
It is necessary to keep the positive and negative plates as close as possible without contact so that
the IR is reduced. Very close spacing is not possible because (1) lead tends to grow in dendritic
form on the substrate during charge and is likely to cause a short-circuit by coming into contact
with the adjacent plate; (2) the plates tend to buckle under pressure developed by the PbSO4
formed by buckling when the plates are overcharged or undercharged; and (3) the plates are
displaced by mechanical and thermal shocks to the supports, so some form of porous separator
that fills the intervening space completely is required. Several materials have been tried for this.
The separators are thin sheets of non-conducting material made up of chemically treated
leadwood, porous rubbers, or mats of glass fibre and are placed between the positive and negative
to insulate them from each other. Separators are grooved vertically on one side and are smooth on
the other side.
A. Assembling the elements
a) Assembly1
b)Assembly2

23. Assembly1
 CONTAINER& Battery Terminals
 Terminal Casting Machine

 Container – The container of the lead acid battery is made of glass, lead lined wood,
ebonite, the hard rubber of bituminous compound, ceramic materials or moulded plastics
and are seated at the top to avoid the discharge of electrolyte. At the bottom of the
container, there are four ribs, on two of them rest the positive plate and the others support
the negative plates.
 The prism serves as the support for the plates and at the same time protect them from a
short-circuit.The material of which the battery containers are made should be resistant to
sulfuric acid, should not deform or porous, or contain impurities which damage the
electrolyte.
Assembling the Elements
 In this process, all the parts are assembled into a battery case and covered with the plastic
moulds plastic molding plant. This step involves the formation of positive and negative
plate stacks, insertion of separators, inter-cell connector and plate burning. In this step
positive and negative plates are formed like groups which are strapped to a suitable rack,
slipped together and a separator is inserted in-between them. This separator is made up of
non-conductive material such as paper, plastic or a glass fiber.


24.  Duringthe burningoperationeachpositive andnegative plate tab is welded to lead to produce
an elementandthese are thenweldedtorespective positive andnegativepostsonthe battery’s
case top.Afterkeepingthiselementinthe jaror case,sealingcompoundisapplied to make the
space leak proof between the battery jar and cover.

Assembly2

Filling and Formation
 After the assembling, battery jar is filled with required amount of electrolyte through a
filling or vent tube. Then, it is ready for initial charging, which may require several hours
of charging depending on the battery size. Low charging rate is generally employed that
may be nearly one day to several days. This charge formation may either be dry or wet. In
a dry-formation method, batteries are shipped as dry after the positive and negative
elements are fully charged or formed and dried in tanks or as an individual plates and are
connected to positive and negative terminals of the battery.

25.  HEAT SEAL WITH PRESSURE
TEST
 SHORT CIRCUIT TEST
 AIR LEAKAGE TEST

 Intercell Welding and Post Burning
Afterworkersplace all the groupsinthe batterycase,the strapsare fusedtogetherusingatorch

26. or highelectrical powersource.Thisprocesscanalsobe done ThroughThe Partition(TTP),using
a case that has beenpunched.The connectionsare thenwelded.The unitsare testedandthe
postsare attached.The major source of leadexposure inthe intercell weldingprocesscomes
fromleadfumes.

5. Charging and Discharging

27. 
Charging and Discharging Process
After the formation, batteries are subjected to high-rate discharge test for short duration to
rule out any defects before sending them out to the final charge. After discharging and
recharging batteries for several times to attain best working condition, these are inspected
and tested with some measuring instruments.
 Then finally these are recharged for certain backup hours and sent to the next level where
additional connections, labeling and caps are inserted to battery with sealed-cotton
packing. At last, these are dispatched to ordered places.
Electrical Department-substation
Electric power is generated ,transmitted and distributed in formof AC . Electric poweris produced
at substation . Substation transform voltage from high to low , or reverse , or perform other
important functions. A substation include transformers to change voltage levels between high
transmission voltages and lowerdistribution voltages or at interconnection of twodifferent
transmission voltages.
Switch yard Component use in substation:
Followingare the substationequipment:-
 Transformer
•Power Transformer
•Distribution Transformer
•Current Transformer
•Potential Transformer
 Circuit Breaker
 Isolator
 Capacitor Bank
 Lightning Arrester
 Conductors

28.  Switchgear
 Insulator  Earthing  Bus-bars etc. 1.2.1
Transformer:
Transformerisa static machine,whichtransformsthe potential of alternatingcurrentatsame
frequency.Itmeansthe transformertransformsthe low voltageintohighvoltage &highvoltage tolow
voltage atsame frequency.Itworksonthe principle of staticinductionprinciple.
Whenthe energyistransformedintoahighervoltage,the transformeriscalledstepup
transformerbutincase of other isknownas stepdowntransformer.
Followingare the typesof transformers:
•Power Transformer
•Distribution Transformer
•Current Transformer
•Potential Transformer
1) Power Transformer

29. The powertransformergenerallyusedinthe generatingstationandsubstation.The size of
the powertransformerisabove than250 KVA.Theyare delta/deltaorstar/deltaconnected
transformers.Theyare operatedfromnormal loadtopeakloadand are disconnectedduring
lightloadperiod.Thereforetheyhave generallyratioof ironlosstocopperlossis 1:1. Thisis
the reasonthat the powertransformerisdesignedtohave maximumefficiencyatload.
Theyare designedtohave large reactance since currentcontrollingismuchmore
importance thanthat of voltage regulation.Thisisthe mostimportantcomponentof the
substations.The mainworkof a substationistodistribute powerata low voltage,by
steppingdownthe voltage thatitreceivesinitsincominglines.Powerisgenerally
transmittedoverlongdistancesatveryhighvoltages,generallyinthe range of 400 KV,200
KV,132 KV,66KV,33KV to the substations.Howeveraconsumerrequirespoweratrather
lowvoltages,11 KV for industriesand440V or 230V for domesticconsumers.The
substationsuse step-downtransformerstoattainthisvoltage andthendistributethis
power.
In phidimsubstationtransformersratingof 3MVA isusedfor33/11KV for supply
powerintransmissionanddistributionlines.
2) Distribution Transformer:
A distributiontransformerisatransformerthatprovidesthe final voltage
transmissioninthe electrical powerdistributionsystem, steppingdownvoltage tothe level used
by customers. These transformers are located near the consumer’s localitiesand step down
to 400V, 3-phase, 4-wire for supplying to the consumers. The voltage between any two
phases is 400V & between any phase and neutral it is 230V. Distributiontransformersmaybe
Figure 5: Power Transformer

30. oil filledordry-filled.DistributionTransformersconsistof twoprimarycomponents:Core and
Coil.Coil isa conductor,or winding,typically made of alow resistance materialsuchas
aluminumorcopper.Copperor aluminumconductorsare woundaroundamagneticcore to
transformcurrentfrom one voltage toanother.Liquidinsulationmaterial orair(dry-type)
surroundsthe transformercore and conductorsto cool and electricallyinsulatedthe
transformer.A core made of magneticallypermeable material like grainorientedsteel.
Distributiontransformersare eithermountedonanoverheadpole orona concrete pad at
groundlevel.There issome evidence tosuggestthatpole mountedtransformersdissipatesheat
more easilythanpadmountedunitsandmay therefore be more fullyloaded.
Figure 6: Pole mounted Distribution Transformer
3) Current Transformer:
Currenttransformerisan
instrumenttransformer,usedalongwithmeasuringor
protective devices,inA whichthe secondarycurrentis
proportional tothe primarycurrent.Currenttransformers
supplythe protective relayswithcurrentsof magnitude
proportional tothose of powercircuitbutsufficiently
reducedinmagnitude.The measuringdevicescannotbe
directlyconnectedtothe highmagnitude supplies.Hence
currenttransformersare usedto supplythose devices
withcurrentsof magnitude proportional tothose of
power.A current transformeralsoisolatesthe measuring

31. instrumentsfromhighvoltage circuits.The ratioof CT is 75/5 A usedinphidimsubstation.
Figure 7: Current Transformer
4) Potential Transformer:
Voltage transformers(VT)(also
calledpotential transformers(PT)) are aparallel
connectedtype of instrumenttransformer,usedfor
meteringandprotectioninhigh-voltagecircuitsor
pharosphase shiftisolation.Theyare designedto
presentnegligible loadto the supplybeingmeasuredand
to have an accurate voltage ratiotoenable accurate
metering.A potential transformermayhave several
secondarywindingsonthe same core as a primary
winding,foruse indifferentmeteringorprotection
circuits.The ratio of PT use in substationwas33000/110
V incomingfeederand11000/110 V for outgoingfeeder.
Figure 8: Potential TransformerFigure 7: Potential Transformer
1.2.2 Circuit Breaker
Electrical circuitbreakerisa switchingdevicewhichcanbe operatedmanuallyandautomatically
for controllingandprotectionof electrical powersystemrespectively.Asthe modernpower
systemdealswithhuge currents,the special attentionshouldbe givenduringdesigningof circuit
breakerforsafe interruptionof arcproducedduringthe operationof circuitbreaker.

32. Figure 9: Vacuum Circuit BreakerFigure 8 : Vacuum Circuit Breaker
Vacuumcircuit breakersare circuitbreakerswhichare usedtoprotect mediumandhighvoltage
circuitsfromdangerouselectrical situations.Like othertypesof circuitbreakers,vacuumcircuit
breakersliterallybreakthe circuitsothatenergycannotcontinue flowingthroughit,thereby
preventingfires,powersurges,andotherproblemswhichmayemerge.Thesedeviceshave been
utilizedsincethe 1920s, and several companieshave introducedrefinementstomake themeven
saferand more effective.
1.2.3 Isolator

33. Figure 10: Center Rotating Isolator
A mechanical switchingdevice whichisusedtomake orbreak the circuitunderno loadconditionis
knownas isolator.itisalsocalleddisconnectingswitchandusedextensivelyfordisconnection
feeder,circuitbreaker,bus-baretc.fortheirregularrepairandmaintenance workbecause this
device isdesigned tooperate under noloadcondition.Itisverysimple inconstructionandisa
cheapestdevice usedinpowersystemcontrolled.Anisolatorisusedinbus-barsystemfor
generatingstation,powersubstationanddistributionsubstationforswitchingof bus-barforrepair
and maintenance work.Because itssimple constructionalfeature andbeingcheapestamongthe
switchgear.Theyare alsousedto require the circuitbreakerforeconomy.
Centre breakisolatorare use inphidimsubstation.
Typesof isolatorare as follows:
 Central break
 Vertical swing
 Central rotating
 Pento graph
1.2.4 Lighting Arrestor
A lightningarrestorisadevice usedin powersystems
and telecommunications systemstoprotectthe
insulation andconductorsof the systemfromthe

34. damagingeffectsof lightning.The typical lightningarresterhasa high-voltage terminal anda
groundterminal.Whenalightningsurge (orswitchingsurge,whichisverysimilar) travelsalong
the powerline tothe arrester,the currentfrom the surge is divertedthroughthe arrestor,in
mostcases to earth.
Figure 11: Lighting Arrestor
1.2.5 Insulator
An electrical insulatorisamaterial whose internal electricchargesdonotflow freely,andtherefore
make it veryhard toconduct an electriccurrentunderthe influence of anelectricfield.The
insulatorservestwopurposes.Theysupportthe conductors(busbar) andconfine the currentto
the conductors.The mostcommonusedmaterial forthe manufacture of insulatorisporcelain.
There are several typesof insulators
Shackle Insulator
In earlydays,the shackle insulatorswereusedasstraininsulators.Butnow a
day,theyare frequentlyusedforlow voltage distributionlines.Such
insulatorscanbe usedeitherina horizontal positionorina
vertical
Pin type Insulator
As the name suggests,the pintype insulatorismountedonapinon the
cross-armon the pole.There isa groove on the upperendof the
insulator.The conductorpassesthroughthisgroove andistiedto the
insulatorwithannealedwire of the same material asthe conductor.Pin
type insulatorsare usedfortransmissionanddistributionof electric
powerat voltagesupto 33 kV.Beyondoperatingvoltage of 33kV,the
pintype insulatorsbecome toobulkyandhence uneconomical.
Figure 121: Shackle Insulator
Figure 132: Pin Type
Insulator
Suspension
Insulator
For voltagesgreater
than 33 kV,itis a
usual practice to
use suspension

35. type insulatorsshowninFigure.Consistof anumberof porcelaindiscs
connectedinseriesbymetal linksinthe formof a string.The conductor
issuspendedatthe bottomendof thisstringwhile the otherendof the
stringissecuredto the cross-armof the tower.The numberof disc units
useddependsonthe voltage.
Strain Insulator
A deadendor anchor pole or towerisusedwhere astraight
sectionof line ends,oranglesoff inanotherdirection.These poles
mustwithstandthe lateral (horizontal) tensionof the longstraight
sectionof
wire.Inorder
to supportthis
lateral load,
strain
insulatorsare
used.
Figure 15: Strain
Insulator
For lowvoltage lines(lessthan11 kV),shackle insulatorsare usedasstraininsulators.However,for
highvoltage transmissionlines,stringsof cap-and-pin(disc) insulatorsare used,attachedtothe
cross arm ina horizontal direction.Whenthe tensionloadinlinesisexceedinglyhigh,suchasat
longriverspans,twoor more stringsare usedinparallel position.Theycanbe directlyfixedtothe
pole witha boltor to the cross arm.
Figure 14: Suspension Insulator

36. 1.2.6 Bus-bar
Figure 15Figure : Bus-bar16: Bus-Bar
Whennumbersof generatorsorfeedersoperatingatthe same voltage have tobe directlyconnected
electrically,busbarisusedas the commonelectrical component.Busbarsare made up of copperrods
operate at constantvoltage.The followingare the importantbusbarsarrangementsusedatsubstations:
• Single bus bar system
• Single bus bar system with sectionalized.
• Duplicate bus bar system
In large stationsitisimportantthat breakdownsandmaintenance shouldinterfere aslittleas
possible withcontinuityof supplytoachieve this,duplicatebusbarsystemisused.Sucha system
consistsof twobus bars, a mainbusbar anda spare busbar withthe helpof buscoupler,whichconsist
of the circuitbreakerandisolator.Insubstations,itisoftendesiredtodisconnectapart of the system
for general maintenance andrepairs.Anisolatingswitchorisolatoraccomplishesthis.Isolatoroperates
underno loadcondition.Itdoesnothave anyspecifiedcurrentbreakingcapacityorcurrentmaking
capacity.In some casesisolatorsare usedto breakingchargingcurrentsortransmissionlines.

37. While openingacircuit,the circuitbreakerisopenedfirstthenisolatorwhile closingacircuitthe isolator
isclosedfirst,thencircuitbreakers.Isolatorsare necessaryonsupplysideof circuitbreakers,inorderto
ensure isolationof the circuitbreakerfromlive partsforthe purpose of maintenance.Inphidim
substationsingle busbarsystemtype of busbarare used.
1.2.7 Earthing
FigureFigure 16: Earthing17: Earthing
In an electrical installationoranelectricitysupplysystemanearthingsystemorgrounding system
connectsspecificpartsof that installationwiththe Earth'sconductive surface forsafetyand
functional purposes.The pointof reference isthe Earth'sconductive surface,oronships,the surface
of the sea.The choice of earthingsystemcanaffectthe safetyandelectromagneticcompatibilityof
the installation.Regulationsforearthingsystemsvaryconsiderablyamongcountriesandamong
differentpartsof electrical systems,thoughmanyfollow the recommendationsof the International
Electrotechnical Commissionwhichare describedbelow.Thisarticle onlyconcernsgroundingfor
electrical power.
Examplesof otherearthingsystemsare listedbelow withlinkstoarticles:
• To protect a structure from lightning strike, directing the lightning through the earthing system and
into the ground rod rather than passing through the structure.
• As part of a single-wire earthreturnpowerandsignal lines, such as were used for low wattage power
delivery and for telegraph lines.
• In radio, as a ground plane for large monopole antenna.

38. A functional earthingconnectionservesapurpose otherthanelectrical safety,andmaycarry
currentas part of normal operation.The mostimportantexampleof afunctional earthisthe neutral
inan electrical supplysystemwhenitisacurrent-carryingconductorconnectedtothe earth
electrode atthe source of electrical power.Otherexamplesof devicesthatuse functional earth
connectionsincludesurge suppressorsandelectromagnetinterference filters.
1.3 Relay and Panel Section Component
1.3.1 Relay
In a powersystemitisinevitablethatimmediatelyorlatersome failure doesoccursomewhereinthe
system.Whena failure occursonany part of the system, itmustbe quicklydetectedanddisconnected
fromthe system.Rapiddisconnectionof faultedapparatuslimitsthe amountof damage toitand
preventsthe effectsof faultfromspreadingintothe system.Forhighvoltage circuitsrelaysare
employedtoserve the desiredfunctionof automaticprotectivegear.The relaysdetectthe faultand
supplythe informationtothe circuitbreaker.
The electrical quantitieswhichmaychange underfaultconditionare voltage,frequency,current,phase
angle.Whena short circuit occurs at any pointonthe transmissionline the currentflowinginthe line
increasestothe enormousvalue.Thisresultinaheavycurrentflow throughthe relaycoil,causingthe
relayto operate byclosingitscontacts.Thisin turnclosesthe trip circuitof the breakermakingthe
circuitbreakeropenandisolatingthe faultysectionfromthe restof the system.Inthisway,the relay
ensuresthe safetyof the circuitequipmentfromthe damage andnormal workingof the healthyportion
of the system.Relayworksontwomainoperatingprinciples,Electromagneticattractionand
ElectromagneticInduction
RELAY USED IN CONTROLLING PANEL OF SUBSTATION
.DifferentialRelay
A differentialrelayisone thatoperateswhenvectordifference of the two or
more electrical quantitiesexceedsapredeterminedvalue.If thisdifferential
quantityisequal orgreaterthan the pickupvalue,the relaywill operateandopen
the circuitbreakerto isolate the faultysection.
Figure 187: Differential Relay

39. .OverCurrentRelay
Thistype of relayworkswhencurrentinthe circuitexceedsthe predetermined
value.The actuatingsource isthe current inthe circuit suppliedtothe relay
froma currenttransformer.These relayare usedonA.C.circuitonlyandcan
operate forfaultflowinthe eitherdirection.
Thisrelayoperateswhenphase tophase faultoccurs.
Figure 198: Over Current Relay
.Earth FaultRelay
Thistype of relaysense the faultbetweenthe linesandthe earth.It
checksthe vector sum of all the line currents.If itisnot equal tozero,it
trips.
.TrippingRelay
Thistype of relayisinthe conjunctionwithmainrelay.Whenmain
relaysense anyfaultinthe system,itimmediatelyoperatesthe trip
relayto disconnectthe faultysectionfromthe section.
.AuxiliaryRelay
An auxiliaryrelayisused
to indicate the faultby
glowingbulborshowing
variousflags.

40. Figure 1920: Earth Fault Relay
Figure 210: Tripping Relay
FigureFigure 2122:: Auxiliary
Relay Auxiliary Relay
1.3.2 Control panel

41. Figure 23: Control Panel
Metal-cladcubiclesdesignedwithwithdraw able trucksanddividedintoseveral compartmentsare
usuallyemployed.The several compartmentsinwhichthe cubicleisdividedare control compartment,
indicatingandmeteringinstrumentandprotective device compartment,circuitbreakerandoperating
mechanismcompartment,mainbus-barcompartmentandcurrenttransformersandcable sealingbox
compartment.The circuitbreakeranditsoperatingmechanismare mountedonthe truck,whichcan be
withdrawnfromthe cubicle.Inwithdraw able-truckunit-typecubiclesthe isolatingdevice isof the plug-
intype.Whenthe truck is rolledoutfromthe cubicle the holesnwhichthe isolatingdevice entersfor
makingcontact are automaticallyclose bymetal shuttersservingtoisolate the livepartfrompossible
casual contact. Whenthe truck is rolledbackintothe cubicle,the shuttersopenautomatically.
To preventanypossible openingorclosingof the disconnectingdeviceswhenthe circuitbreakeris
closed,these cubiclesare designedwithinterlockswhichpreventthe truckfrombeingrolledinor
withdrawwhenthe circuitbreakerisclosed.
1.4 Battery Bank

42. Figure 24: Battery Bank
It isusedto supplythe backuppowerto the specifiedfeederandthe indicatinglampsof the panel
board.Its ratingis 110V. The most critical componentof a protection,control andmonitoring(PCM)
systemisthe auxiliarydccontrol powersystem. The heartof a substationisthe batterybank.If this
were tofail,an electricutilitycouldexpose all feedersassociatedwiththe stationtoa condition
where theycouldnotevertripina fault.Anybackupdevices,suchasthe main breakeronthe low-
voltage side orthe high-voltageside protectionof the powertransformer,wouldall be inoperative.
1.5 Conductors use in Substation Design
An ideal conductorshouldfulfill the followingrequirements:

43. a) Should be capable of carrying the specified load currents and short time currents.
b) Shouldbe able towithstandforcesonit due to its situation. These forces comprise selfweight, and
weightof otherconductorsand equipment,shortcircuitforcesandatmosphericforcessuchas wind
and ice loading.
c) Should be corona free at rated voltage.
d) Should have the minimum number of joints.
e) Should need the minimum number of supporting insulators.
f) Should be economical.
The most suitable material forthe conductorsystemiscopperoraluminums.Steel maybe used
but haslimitationsof poorconductivityandhighsusceptibilitytocorrosion. Inaneffortto make
the conductor ideal,three differenttypeshave beenutilized,andthese include:Flatsurfaced
Conductors,StrandedConductors,andTubularConductors

44. 1.6 Sub-station Protection
1.6.1 Transformer Protection
Transformersare totallyenclosedstaticdevicesandgenerallyoilimmersed.Therefore
chancesof faultoccurringon themare veryeasyrare, howeverthe consequencesof
evena rare faultmay be veryseriousunlessthe transformerisquicklydisconnected
fromthe system.Thisprovidesadequate automaticprotectionfortransformersagainst
possible faults.Variousprotectionmethodsusedfortransformersare:-
Buchholz Relay
Buchholzrelayisa safetydevice mountedonsome oil-filledpower
transformersandreactors,equippedwithanexternal overheadoil
reservoircalledaconservator.The BuchholzRelayisusedasa
protective devicesensitive tothe effectsof dielectricfailure inside
the equipment.Dependingonthe model,the relayhasmultiple
methodstodetecta failingtransformer.Onaslow accumulationof
gas, due perhapstoslightoverload,gasproducedbydecomposition
of insulatingoil accumulatesinthe topof the relayandforcesthe oil
level down.A floatswitchinthe relayisusedtoinitiate analarm
signal.
Dependingondesign,asecondfloatmayalsoserve todetectslow
oil leaks.If anarc forms,gas accumulationisrapid,andoil flows
rapidlyintothe conservator.Thisflowof oil operatesaswitch
attachedto a vane locatedinthe pathof the movingoil.Thisswitch
normallywill operateacircuitbreakertoisolate the apparatusbefore
the faultcausesadditional damage.
Conservator and Breather
Whenthe oil expandsorcontacts by the change inthe temperature,the
oil level goeseitherupordowninmain tank.A conservatorisusedto
maintainthe oil leveluptopredeterminedvalueinthe transformermain
tank byplacingit above the level of the topof the tank.Breatheris
connectedtoconservatortankfor the purpose of extractingmoisture as
it spoilsthe insulatingpropertiesof the oil.Duringthe contractionand
expansionof oil airis
drawnin or out
throughbreather
silicagel crystals
impregnatedwith
cobaltchloride.Silica
gel ischecked
regularlyanddried
and replacedwhen
necessary.

45. FigureFigure 2425: Buch:
Buchholz Relayolz Relay
Figure 265: Silica Gel
BreatherBreather
Marshalling box
It has twometerwhichindicate the temperatureof the oil and
windingof maintank.If temperature of oil orwindingexceeds
than specifiedvalue,relayoperatestosoundanalarm.If there is
furtherincrease intemperature thenrelaycompletesthe trip
circuitto open the circuitbreakercontrollingthe transformer.
Transformercooling

46. Figure 26:Figure Marshalling
Box27: Marshalling Box

47. INDUSTRIAL TRAINING REPORT,
Page 47
Whenthe transformerisinoperationheatisgenerateddue toironlossesthe removal of heatiscalled
cooling.
There are several typesof coolingmethods,theyare asfollows:
1. Air natural cooling
In a dry type of self-cooledtransformers,the natural circulationof surroundingairisusedfor
itscooling.Thistype of coolingissatisfactoryforlow voltage small transformers.
2. Air blast cooling
It issimilartothat of dry type self-cooledtransformerswithtoadditionthatcontinuousblast
of filteredcool airisforcedthroughthe core and windingforbettercooling.A fanproducesthe
blast.
3. Oil natural cooling
Mediumandlarge rating transformershave theirwindingandcore immersedinoil,whichact
bothas a coolingmediumandaninsulatingmedium.The heatproduce inthe coresand
windingispassedtothe oil becomeslighterandrises tothe top and place istakenby cool oil
fromthe bottomof the coolingtank.
4. Oil blast cooling
In thistype of cooling,forcedairisdirectedovercoolingelementsof transformersimmersedin
oil.
5. Forced oil and forced air flow (OFB) cooling
Oil iscirculatedfromthe top of the transformerstanktoa coolingtankto a coolingplant.Oil is
thenreturnedtothe bottomof the tank.

48. INDUSTRIAL TRAINING REPORT,
Page 48
6. Forced oil and water (OWF) cooling
In thistype of coolingoil flowwithwatercoolingof the oil inexternalwaterheatexchanger
takesplace.The wateris circulatedincoolingtubesinthe heatexchanger.
1.6.2 Busbar Protection
Faultsina powersystemcanbe eitherapparatusfaultsorbus faults.Apparatusfaultrefertofaults
infeeders,transformers,generatorsormotors.Onthe otherhand busis an external
interconnectionpointforterminalsof differentapparatus.A busfaultisusuallyrare,butif and
whenithappensitsconsequencescanbe quite severe.Itcanleadlossof multiple feedersor
transmissionlinesandhence hasapotential tocreate a large enoughdisturbance toinduce
transientinstability.Evenif itdoesnotleadtotransientinstability,lossof loadfroman important
substationcanbe quite high.Because of these reasons,busrearrangementcanhave sufficient
redundancysothat incase of a busfault,an alternative busautomaticallytakesoverthe functions
of the ‘mainbus'.Thus,the enduserseesnodisruptioninservice exceptduringthe faultinterval.
Thiscan howeverinvolvesignificantcosts,viathe costof new busbarand additional circuit
breakerstoconfigure aparallel arrangement.Hence,differentbusconfigurationsare usedin
practice – eachone representingadifferenttradeoff betweencost,flexibilityandredundancy.
Alsothere are variousmethodsof busprotectiongivenasfollowing:
• Overcurrent
• Trip Blocking Schemes
• Communication‐Based Schemes
• High‐Impedance Current Differential
• Low‐Impedance Current Differential
• Distance
• Linear Coupler
• Arc Flash Detection

49. INDUSTRIAL TRAINING REPORT,
Page 49
1.6.3 Feeders Protection
Faultsoccurringon overheadandundergrounddistributionfeederscausedbyvarioussources
including:
• Faulty equipment
• Environmental inducedfaults:wind,lightning,ice,snow-storm, sagdue toextreme temperature,
salt spray
• Falling tree limbs
• Animal contacts
• People induced including: pole and overhead contacts and underground digging
Faultsoccurringin the distributionsystemmustbe sensedquicklyandimmediatelyisolatedto
preventhazardstothe general publicandutilitypersonnel.Protective relaysare usedtosense
short circuitconditionscausedbyfaultsindistributionprotectionschemesandthe use of proper
schemesandsettingscanhelptomaximize sensitivityandselectivity.
Some permanentfaultscanbe equipmentfailuresorcablescutor short-circuitedbyexcavation
equipment.The type of groundingof the distributionsystemaffectsthe voltageandcurrent
characteristicsduringafault.Properprotectionstrategiesshouldbe employedtomake
dependabilityanutmostcriterion.
Basic feederprotectionprinciplesare well-known.Phase andgroundovercurrentfunctionsreliably
detectmostfaults.Reclosingisoftenappliedtorestore service followingtemporaryfaultson
overheadcircuits.Securityismaintainedthroughtime andpickupcoordinationbetween
overcurrentdevicesthatmayoperate fora specificfaultevent.The challenge infeederprotection
isreliable operationduringunusualfaulteventssuchashighimpedance groundfaultsand
adjacentfeederfaults.A keyadvantage of microprocessorbasedfeederrelaysisthe abilityto
protectagainstthese unusual faults,while improvingthe operationof the distributionsystem
throughflexibility,programmabilityandcommunications.
CHAPTER-2
INTERNSHIP DETAILS
2.1 Replacement of Silica Gel

50. INDUSTRIAL TRAINING REPORT,
Page 50
Figure 28: Silica Gel Breather
Figure 27: Silica Gel Breather
Silicagel crystal hastremendouscapacityof absorbingmoisture.Whenairpassesthroughthese crystals
inthe breather;the moisture of the airisabsorbedbythem.Therefore,the airreachestothe
conservatorisquite dry,the dustparticlesinthe air gettrappedby the oil inthe oil seal cup. The oil in
the oil sealingcupacts as barrierbetweensilicagel crystal andairwhenthere isno flow of airthrough
silicagel breather.The colorof silicagel crystal isdark blue but,whenitabsorbsmoisture;itbecomes
pink.Whenthere issufficientdifference betweenthe airinsidethe conservatorandthe outside air,the
oil level intwocomponentsof the oil seal changesuntilthe loweroil level justreachesthe rimof the
invertedcup,the airthenmovesfromhighpressure compartmenttothe low pressure compartmentof
the oil seal.Bothof these happenwhenthe oil actsascore filterandremovesthe dustfromthe outside
air.
Whengel absorbsmoisture itscolourslowlychangesintodarkblue tolightblue topink.Pinkcolour
indicatesthe gel issaturatedandshouldbe replaced.
2.2 Replacement of Tripping coil of Outgoing Feeder
Trippingcoil isa control device thatutilizesasolenoidtoopencircuitbreaker.Tripcoil isusedto serve
the purpose of trippingthe breakerwhile currentexceedsthe certainlimit(Due tooverloadorfault) .

51. INDUSTRIAL TRAINING REPORT,
Page 51
Figure 298: Tripping Coilcoil
Trippingcoil wasburntout that is why while checkingthe triphealthincontrol panel boardits light
didn’tglow.Soreplacementof trippingcoil wasdone.
Perhapsoccasionallyacoil ona solenoidvalve mayburnoutbecause of a defectinitsmanufacture.But
usuallythe cause can be traced to some abnormal conditioneitherinoperatingconditionsof the
machine onwhichthe valve isinstalled,ortounusual environmental conditions

52. INDUSTRIAL TRAINING REPORT,
Page 52