This document is a seminar presentation on using superconductors for surge current protection. It discusses superconductors and their properties like zero resistance below a critical temperature. It explains how superconducting fault current limiters work and their applications. Different types of limiters are described, including resistive and inductive models. The document provides examples of fault current limiter programs around the world. It discusses the advantages, limitations, and disadvantages of using superconductors for protection.

1. I
A
SEMINAR
ON
“SURGECURRENTPROTECTIONUSINGSUPERCONDUCTOR”
Submittedinpartialfulfillmentforbachelorof
technologyDegreeat
RajasthanTechnicalUniversity,Kota
BACHELOROFTECHNOLOGY
IN
ELECTRICALENGINEERING
SUPERVISEDBY: SUBMITTEDBY:
Prof.ASADZAI SARFARAZKHAN
RollNo.-13EVEEE051
Enrl.No.-13E1VEEEM3XP051
DEPARTMENTOFELECTRICALENGINEERING
VYASINSTITUTEOFENGINEERINGANDTECHNOLOGY,JODHPUR
RAJASTHANTECHNICALUNIVERSITY,KOTA

2. II
2017
CERTIFICATE
ThisistocertifythatthestudentMr.SarfarazKhanoffinalyear,have
successfullycompletedtheseminarpresentationon“SURGECURRENT
PROTECTIONUSINGSUPERCONDUCTOR”towardsthepartialfulfillment
ofthedegreeofBachelors ofTechnology(B.TECH)intheElectrical
EngineeringoftheRajasthanTechnicalUniversityduringacademicyear
2017undermysupervision.
Theworkpresentedinthisseminarhasnotbeensubmittedelsewherefor
awardofanyotherdiplomaordegree.
Prof.AsadZai
Supervisor
Professor
Deptt.ofElectricalEngineering
VIET,Jodhpur.
CounterSignedby:
Prof.ManishBhati
Head
Deptt.ofElectricalEngg.
VIET,Jodhpur.

3. III
ACKNOWLEDGEMENT
FirstIwanttothankmy
“ALLAH”
who neverleavesmealonein bad circumstances,help me
alwayswiththeirwellblessings.
Thereareanumberofpeoplewhodeserverecognitionfortheir
unwavering supportand guidance throughoutthis seminar
presentation.Iwouldliketotakethisopportunitytothankthem.
Firstandforemost,Iwanttothankmywell-wisheradvisorandas
aguide,Mr.AsadZaiSirforhissupport,constructivecriticism,
andnew technicalupdates.Thispresentationcouldhavenot
beencompletedwithouthisenthusiasmanddirection.
IagainwanttothankMr.AsadSirforgivingmethistypeof
technicaltheorytopicbywhichIcanunderstandmycorebranch
efficiently.
IwillbealwaysthankfultoOurHODMr.ManishBhatiSirfor
expandingmyunderstandingofglobalinequalitiesthroughout
historyandherconstantmentorship.
Iwanttothankmyfriendswhohaveencouragedmeoverthe
studyofthispresentation.
Finally,Iwanttothankmyfamily.Myparents,especially,have
beenasourceofstrengthandsupportforme.Theycontinually
pushmetothinkcriticallyandneversettleforanythinglessthan
mybest.Theykeptmefocused,ontrackandfedinthefinal
stretchofmycollegestudy.
Fortheircontinualsupport,Iamforevergrateful.

4. IV
ABSTRACT
ModernPowerSystemsaregrowingfastwithmoregenerators,
transformersandlargenetworkinthesystems.Theinstallation,
runningandmaintenancecostsofthepowersystem equipment
aremore.Wheneverafaultoccurs,thereisaneed forthe
protection ofthese systems.PowerSystem Protection is a
branch ofelectricalpowerengineering thatdeals with the
protectionofelectricalpowersystemsfrom faultsthroughthe
isolationoffaultedpartsfrom therestoftheelectricalnetwork.
Superconductorsareoneofthelastgreatfrontiersofscientific
discovery.Here,in thispaperwediscusstheuseofSuper
ConductorsasprotectivedevicesforSurgeCurrentProtection.
Superconductors conductelectricity offering zero resistance
below certaintemperatures.Westudydifferenttypesofsuper
conductorfaultcurrentlimitersandtheirworking.

5. V
LISTOFFIGURES
Fig.-(1.2)-Graphb/winrushcurrentand
time.........................................10
Fig.-(2.6)-Faultcontrolwithafault-current
limiter................................13
Fig.-(2.7.1)-Fault-currentlimiterinthemain
position...........................14
Fig.-(2.7.2)-Fault-currentlimiterinthefeeder
position.........................15
Fig.-(2.7.3)-Fault-currentlimiterinthebus-tie
position.........................15
Fig.-(2.8.1)-Fault-currentlimiterwithHTStrigger
coil.........................19
Fig.-(2.8.2)-Inductivefault-current
limiter.............................................20
Fig-(2.9.1)-SchematicdiagramoftheCRIEPIinductive
FCL..............22
Fig.-(2.9.2)-ConfigurationofcoilsintheTEPCO/Toshiba
FCL............23
Fig.-(2.9.3)-Exteriorviewofthe6.6kV2,000A-classcurrent
limiter..24

6. VI
Fig.-(2.9.4)-CurrentlimitingcharacteristicsofToshiba
FCL.................24
Fig.-(3.1)-Lightening
surge....................................................................26
Fig.-(4.1)-Powerratingoftheinductivelimitermodels
built/tested
atHydro
Quebec.....................................................................33
CONTENTS
INNERTITLE………………………………………………………………...I
CERTIFICATE……………………………………………………………….II
ACKNOWLEDGEMENT…………………………………………………...III
ABSTRACT…………………………………………………………………..IV
LISTOF
FIGURES...........................................................................................V
CONTENTS………………………………………………………………VI-VII
Chapter1:Introduction………………………………………………………8
1.1:Introduction…………………………………………………….8
1.2:SurgeCurrent…………………………………………………..9

7. VII
Chapter2:Superconductor…………………………………………………..11
2.1:Superconductor………………………………………………...11
2.2:MeissnerEffect…………………………………………………11
2.3:FaultCurrentLimiter…………………………………………12
2.4:FaultCurrentProblem………………………………………...12
2.5:FaultControlProblem…………………………………………13
2.6:SuperconductiveFcl……………………………………………13
2.7:FaultCurrentLimiterApplications…………………………..14
2.8:SuperconductiveFaultCurrentLimiterConcepts…………..16
2.8.1:SeriesResistiveLimiter………………………........................16
2.8.2:InductiveLimiter………………………………......................19
2.9:FclProgram……………………………………………………..20
Chapter3:LighteningProtection…………………………………………….25
3.1:ComponentsOfLighteningProtectionSystem……………….25
3.1.1:RodsOrAirTerminals……………………………………….25
3.1.2:ConductorCables……………………………………………..25
3.1.3:GroundRods……………………………………......................25
3.2:LighteningProtectionSystem…………………………………..26
3.2.1:HowALighteningProtectionSystemWorks……………….27
3.2.2:LighteningProtectionFacts…………………………………..28
3.2.3:LighteningDissipationMyths………………………………...28
3.3:FuturePlans……………………………………...........................30
3.4:FaultCurrentLimiter……………………………………...........30
3.5:FclPrograms……………………………………………………..31
Chapter4:AdvantagesDisadvantagesAndLimitationsOf
Superconductor.33
4.1:Advantages……………………………………...............................33
4.2:Limitations……………………………………...............................35
4.3:Disadvantages……………………………………..........................35
Chapter5:Applications…………………………………………………………38

8. VIII
5.1:BasicApplications……………………………………...................38
5.1.1:LowTemperatureSuperconductivity…………………………38
5.1.2:ParticleAcceleratorsAndMagneticFusion
Devices…………39
5.1.3:HighTemperatureSuperconductivity………………………..39
5.1.4:HtsBasedSystems……………………………………...............40
Chapter6:FutureAspects………………………………………………………41
6.1:SuperconductivityTransmissionLines………………………….41
6.2:PowerApplications,HighTc……………………………………..41
6.3:FaultCurrentLimiter…………………………………….............42
6.4:SuperconductingMotors……………………………………........42
6.5:SuperconductingMaglevTrains…………………………………42
CONCLUSION:
....................................................................................................46
REFERENCES:
....................................................................................................47
CHAPTER-1
Introduction
1.1Introduction
Beforeknowinghowthesuperconductorsactsassurgecurrentprotectors

9. 9
letus
concentrateonwhatissurgecurrent?Whatitdoestothepowersystem?And
whatare
superconductors?MeissnerEffectanddifferenttypesofsuperconductor
faultcurrent limiters.
Electricpowerdistributionsystemsincludecircuitbreakerstodisconnect
powerincaseofafault,buttomaximizereliability,theywishtodisconnect
thesmallestpossibleportionofthenetwork.Thismeansthateventhe
smallestcircuitbreakers,aswellasallwiringtothem,mustbeableto
disconnectlargefaultcurrents.
A problem arises ifthe electricitysupplyis upgraded,byadding new
generationcapacityorbyaddingcross-connections.Becausetheseincrease
theamountofpowerthatcanbesupplied,allofthebranchcircuitsmust
havetheirbusbarsandcircuitbreakersupgradedtohandlethenewhigher
faultcurrentlimit.
Thisposesaparticularproblem whendistributedgeneration,suchaswind
farmsandrooftopsolarpower,isaddedtoanexistingelectricgrid.Itis
desirabletobeabletoaddadditionalpowersourceswithoutlargesystem-
wideupgrades.
Asimplesolutionistoaddelectricalimpedancetothecircuit.Thislimitsthe
rateatwhichcurrentcanincrease,whichlimitsthelevelthefaultcurrentcan
risetobeforethebreakerisopened.However,thisalsolimitstheabilityofthe
circuittosatisfyrapidlychangingdemand,sotheadditionorremovaloflarge
loadscausesunstablepower.
Afaultcurrentlimiterisanonlinearelementwhichhasalowimpedanceat
normalcurrentlevels,butpresentsahigherimpedanceatfaultcurrentlevels.

10. 10
Further,thischangeisextremelyrapid,beforeacircuitbreakercantripafew
millisecond later.(High-powercircuitbreakers are synchronized to the
alternatingcurrentzerocrossingtominimizearcing.)
Whilethepowerisunstableduringthefault,itisnotcompletelydisconnected.
After the faulting branch is disconnected,the fault current limiter
automaticallyreturnstonormaloperation.
1.2SurgeCurrent
Themaximum instantaneousinputcurrentdrawnbyanelectricaldevice
whenfirstitisturnedonisdefinedassurgecurrent.Itisalsoknownas
InrushcurrentorInputSurgeCurrentorSwitch-onSurge.Alternatingcurrent
electricmotorsandtransformersmaydrawseveraltimestheirnormalfull-
loadcurrentwhenfirstenergized,forafew cyclesoftheinputwaveform.
Powerconvertersalsooftenhaveinrushcurrentsmuchhigherthantheir
steadystatecurrents,duetothechargingcurrentoftheinputcapacitance.
Theselectionofovercurrentprotectiondevicessuchasfusesandcircuit
breakersismademorecomplicatedwhenhighinrushcurrentsmustbe
tolerated.Theovercurrentprotectionmustreactquicklytooverloadorshort
circuitbutmustnotinterruptthecircuitwhenthe(usuallyharmless)inrush
currentflows.

11. 11
Fig.-(1.2)-Graphb/winrushcurrentandtime
Theonlylimitsofthesurgecurrentarethelineimpedance,inputrectifierdrop
andthecapacitorequivalentseriesresistance.Highinrushcurrentcanaffectthe
electricalsystemsbytrippingfusesandcircuitbreakersunnecessarily.Ifinrush
protectionisnotinplace,relaysandcircuitbreakersmustberatedthatarerated
higherthananypossibleinrushcurrent.InrushCurrentcanalsocausepitted
contactsonswitchesandrelaysduetoarcingofthecontacts.InrushCurrent
canbeashighas100timesthenormalsteadystatecurrentandlastsforless
thanhalfanormal60hertzcycle.Thissurgecurrentcancausecomponent
damageand/orfailurewithintheequipmentitself,blownfuses,trippedcircuit
breakersandmayseverelylimitthenumberofdevicesconnectedtoacommon
powersource.

12. 12
CHAPTER-2
SUPERCONDUCTOR
2.1Superconductor
Anelement,inter-metallicalloyorcompoundthatwillconductelectricity
without
resistance below a certain temperature.The Dutch Physicist Heike
KamerlinghOnnesofLeidenUniversitywasthefirstpersontoobserve
superconductivityinmercury.
Superconductivityisaphenomenonofexactlyzeroelectricalresistance
certainmaterialswhencooledbelowacharacteristiccriticaltemperature.It
isaquantummechanicalphenomenon.
TypesofSuperconductors:
LowTemperatureSuperconductor
HightemperatureSuperconductors
LTSarethesubstancesthatloseallresistivitycloseto4K,atemperature
attainableonlybyliquid helium.HTS arethesubstancesthatloseall
resistancebelowtemperaturemaintamablebyliquidnitrogen.
 ExamplesofLTS:LeadandMercury
 ExamplesofHTS:YBCO,BSCCO,LSCO,etc.
2.2MeissnerEffect
The Meissner effectis the expulsion ofthe magnetic field from a
superconductor
duringitstransitiontothesuperconductingstate.TheGermanphysicists

13. 13
Walther
MeissnerandRobertOchsenfelddiscoveredthephenomenonin1933by
measuringthemagneticfielddistributionoutsidesuperconductingtinand
leadsamples.Themagneticfluxisconservedbythesuperconductor,when
theinteriorfielddecreasedtheexternalfieldisincreased.
2.3FaultCurrentLimiter
AFaultCurrentLimiterisadevicewhichlimitstheprospectivefaultcurrent
whenafaultoccurs.Generallyfaultcurrentlimitersaresuperconductorfault
currentlimiters.SuperconductingFaultCurrentLimitersaredescribedas
beinginoneofthetwomajorcategories:
Resistive
Inductive
FirstapplicationsforFCLsarelikelytobeusedtohelpcontrolmedium-
voltage
electricity distribution systems,followed by electric-drive ships:naval
vessels,
submarinesandcruiseships.LargerFCLsmayeventuallybeemployedin
highvoltagetransmissionsystems.
Fault-currentlimiters using high temperature superconductors offera
solution to controlling fault-current levels on utility distribution and
transmissionnetworks.Thesefault-currentlimiters,unlikereactorsorhigh-
impedancetransformers,willlimitfaultcurrentswithoutaddingimpedance
tothecircuitduringnormaloperation.Developmentofsuperconductingfault
-currentlimiters is being pursued by severalutilities and electrical
manufacturersaroundtheworld,andcommercialequipmentisexpectedto
beavailablebytheturnofthecentury.[1]

14. 14
2.4Fault-CurrentProblem
Electricpowersystem designersoftenfacefault-currentproblemswhen
expanding
existingbuses.Largertransformersresultinhigherfault-dutylevels,forcing
the
replacementofexistingbusworkandswitchgearnotratedforthenewfault
duty.
Alternatively,theexistingbuscanbebrokenandservedbytwoormore
smaller
transformers.Anotheralternativeisuseofasingle,large,high-impedance
transformer,resultingindegradedvoltageregulationforallthecustomerson
thebus.Theclassictradeoffbetweenfaultcontrol,buscapacity,andsystem
stiffnesshaspersistedfordecades.
2.5FaultControlProblem
Insomeareas,suchastheUnitedStates,additionalgenerationfrom co
generators
andindependentpowerproducers(IPPs)raisesthefaultdutythroughouta
system
olderbutstilloperationalequipmentgraduallybecomesunderratedthrough
system growth;someequipment,such astransformersin underground
vaultsorcables,canbeveryexpensivetoreplacecustomersrequestparallel
servicesthatenhancethereliabilityoftheirsupplybutraisethefaultduty.
2.6SuperconductiveFCL
Superconductorsofferawaytobreakthroughsystem designconstraintsby
presenting

15. 15
impedanceto theelectricalsystem thatvariesdepending on operating
conditions.
Superconductingfault-currentlimitersnormallyoperatewithlowimpedance
andare
"invisible"componentsintheelectricalsystem.Intheeventofafault,the
limiterinsertsimpedanceintothecircuitandlimitsthefaultcurrent.With
currentlimiters,theutilitycanprovidealow-impedance,stiffsystem witha
lowfault-currentlevel.
Fig.-(2.6)-Faultcontrolwithafault-currentlimiter
Alarge,low-impedancetransformerisusedtofeedabus.Normally,theFCL
doesnotaffectthecircuit.Intheeventofafault,thelimiterdevelopsan
impedanceof0.2perunit(Z=20%),andthefaultcurrentISCisreducedto
7,400 A.Withoutthelimiter,thefaultcurrentwould be37,000 A.The
developmentofhigh temperature superconductors (HTS)enables the
developmentofeconomicalfault-currentlimiters.Superconductingfault-
currentlimiterswerefirststudiedovertwentyyearsago.Theearliestdesigns
used low temperature superconductors (LTS),materials thatlose all
resistanceattemperaturesafewdegreesaboveabsolutezero.LTSmaterials
aregenerallycooledwithliquidhelium,asubstancebothexpensiveand

16. 16
difficult to handle. The discovery in 1986 of high temperature
superconductors,whichoperateathighertemperaturesandcanbecooledby
relativelyinexpensiveliquidnitrogen,renewedinterestinsuperconducting
fault-currentlimiters.[2]
2.7Fault-CurrentLimiterApplications
Fault-currentlimiters can be applied in a numberofdistribution or
transmissionareas.
The fault-currentlimiterFCL protects an individualcircuiton the bus.
Underratedequipmentcanbeselectivelyprotectedasneededinthismanner.
Fig.-(2.7.1)-Fault-currentlimiterinthemainposition

17. 17
Fig.(2.7.2)-Fault-currentlimiterinthefeederposition
Thetwobusesaretied,yetafaultedbusreceivesthefullfaultcurrentofonly
onetransformer.Thetwobusesaretied,yetafaultedbusreceivesthefull
faultcurrentofonlyonetransformer.
Fig.-(2.7.3)-Fault-currentlimiterinthebus-tieposition.
Themostdirectapplicationofafault-currentlimiterisinthemainpositionon
abusBenefitsofanFCLinthisapplicationincludethefollowing:
 Alargertransformercanbeusedtomeetincreaseddemandonabuswithout
breakerupgrades
 A large,low impedance transformercan be used to maintain voltage

18. 18
regulationatthenewpowerlevel
 I
2
tdamagetothetransformerislimited
 Reduced fault-currentflows in the high-voltage circuitthatfeeds the
transformer,whichminimizesthevoltagedipontheupstream high-voltage
busduringafaultonthemedium-voltagebus
AnFCLcanalsobeusedtoprotectindividualloadsonthebus(Fig.4.7).The
selectiveapplicationofsmallandlessexpensivelimiterscanbeusedto
protectold
oroverstressedequipmentthatisdifficulttoreplace,suchasunderground
cablesor
transformersinvaults.AnFCLcanbeusedinthebus-tieposition(Fig.4.8).
Suchalimiterwouldrequireonly
Asmallloadcurrentratingbutwoulddeliverthefollowingbenefits:
 separatebusescanbetiedtogetherwithoutalargeincreaseinthefaultduty
on
eitherbus.
 duringafault,alargevoltagedropacrossthelimitermaintainsvoltagelevel
on
theunfaultedbus.
 theparalleledtransformersresultinlowsystemimpedanceandgoodvoltage
regulation;tap-changingtransformerscanbeavoided.
 excesscapacityofeachbusisavailabletobothbuses,thusmakingbetter
useof thetransformerrating.
2.8SuperconductiveFault-CurrentLimiterConcepts
2.8.1TheSeriesResistiveLimiter

19. 19
Thesimplestsuperconductinglimiterconcept,theseriesresistivelimiter,
exploitsthe
nonlinearresistanceofsuperconductorsinadirectway.Asuperconductoris
insertedinthecircuit.Forafull-loadcurrentofIFL,thesuperconductorwould
bedesignedtohaveacriticalcurrentof2IFLor3IFL.Duringafault,thefault
currentpushesthesuperconductorintoaresistivestateandresistanceR
appearsinthecircuit.
Superconductingfaultcurrentlimitersexploittheextremelyrapidlossof
superconductivity (called "quenching)above a criticalcombination of
temperature,currentdensity,andmagneticfield.Innormaloperation,current
flows through the superconductor without resistance and negligible
impedance.
Ifafaultdevelops,thesuperconductorquenches,itsresistancerisessharply,
andcurrentisdivertedtoaparallelcircuitwiththedesiredhigherimpedance.
(Thestructureisnotusableasacircuitbreaker,becausethenormally-
conducting superconductive materialdoes not have a high enough
resistance.Itisonlyhighenoughtocausesufficientheatingtomeltthe
material.)
Superconductingfaultcurrentlimitersaredescribedasbeinginoneoftwo
majorcategories:resistiveorinductive.
InaresistiveFCL,thecurrentpassesdirectlythroughthesuperconductor.
Whenitquenches,thesharpriseinresistancereducesthefaultcurrentfrom
whatitwouldotherwisebe(theprospectivefaultcurrent).AresistiveFCLcan
beeitherDCorAC.IfitisAC,thentherewillbeasteadypowerdissipation
from AClosses(superconductinghysteresislosses)whichmustberemoved

20. 20
bythecryogenicsystem.AnACFCLisusuallymadefrom wirewoundnon-
inductively;otherwisetheinductanceofthedevicewouldcreateanextra
constantpowerlossonthesystem.
InductiveFCLscomeinmanyvariants,butthebasicconceptisatransformer
witharesistiveFCLasthesecondary.Inun-faultedoperation,thereisno
resistanceinthesecondaryandsotheinductanceofthedeviceislow.Afault
currentquenchesthesuperconductor,thesecondarybecomesresistiveand
theinductanceofthewholedevicerises.Theadvantageofthisdesignisthat
thereisnoheatingressthroughcurrentleadsintothesuperconductor,and
sothecryogenicpowerloadmaybelower.However,thelargeamountofiron
required meansthatinductiveFCLsaremuch biggerand heavierthan
resistiveFCLs.
Thequenchprocessisatwo-stepprocess.First,asmallregionquenches
directlyinresponsetoahighcurrentdensity.Thissectionrapidlyheatsby
Joule heating,and the increase in temperature quenches adjacent
regions.
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instantaneouslyincreasesitsimpedancetenfold upon faultcondition.It
limitsthefaultcurrentforitsentiredurationandrecoverstoitsnormal
conditionimmediatelythereafter.ThisinductiveFCLisscalabletoextrahigh
voltageratings.
Thesuperconductorinitsresistivestatecanalsobeusedasatriggercoil,
pushingthe
bulkofthefaultcurrentthrougharesistororinductor.Theadvantageofthis

21. 21
configuration,showninFig.4.9,isthatitthelimitstheenergythatmustbe
absorbedbythesuperconductor.Thefault-currentlimiterFCLnormallyisa
shortacrossthecopperinductiveorresistiveelementZ.Duringafault,the
resistancedevelopedinthelimitershuntsthecurrentthroughZ,which
absorbsmostofthefaultenergy.
Fig.-(2.8.1)-Fault-currentlimiterwithHTStriggercoil
Thetriggercoilapproachisappropriatefortransmissionlineapplications,
wheretensofmegawatt-secondswouldbeabsorbedinaseriesresistive
limiter.Thetriggercoil
configurationalsoallowsanimpedanceofanyphaseangle,from purely
resistiveto
almostpurelyinductive,tobeinsertedintheline.
2.8.2TheInductiveLimiter
Anotherconceptusesaresistivelimiteronatransformersecondary,withthe
primaryinseriesinthecircuit.Thisconcept,illustratedinFig.4.10,yieldsa
limitersuitableforhigh-currentcircuits(IL>1000A).Onephaseofthelimiter

22. 22
isshown.AcopperwindingWCuisinsertedinthecircuitandiscoupledtoan
HTSwindingWHTS.Duringnormaloperation,zeroimpedanceisreflectedto
theprimary.ResistancedevelopedintheHTS windingduringafaultis
reflectedtotheprimaryandlimitsthefault.
Fig.-(2.8.2)-Inductivefault-currentlimiter
Theinductivelimitercanbemodeledasatransformer.Theimpedanceofthis
limiterinthesteadystateisnearlyzero,sincethezeroimpedanceofthe
secondary(HTS)windingisreflectedtotheprimary.Intheeventofafault,
thelargecurrentinthecircuitinducesalargecurrentinthesecondaryand
thewindinglosessuperconductivity.Theresistanceinthesecondaryis
reflectedintothecircuitandlimitsthefault.
2.9FCLProgram
ThedrivingfactorsforcurrentlimitersinJapanaresomewhatdifferentfrom
thoseintheUnitedStates,giventhatIPPsandcogeneratorsarenotas
prevalentinJapan.Rather,thedemandforpowerinJapanesemetropolitan
areas continues to grow because ofeconomic growth and increased

23. 23
consumeruseofelectricity.Inaddition,industrialuseofcomputersandother
power-quality-sensitiveequipmenthasforcedtheutilitiestoprovidehigher
qualityandmorereliablepower.Thequitesuccessfulapproachtoimproved
powerqualityinJapanhasbeentoincreaseconnectionsbetweenvarious
powersystems and to concentrate generation capacityin larger,more
efficientunits.
Increasing interconnection does,however,increase the maximum fault
currentavailableatanypointinthesystem,andthisisrapidlyleadingtothe
need forbreakerupgradesand system reconfigurations.Adding to the
complexityofthesituationinJapanisthelimitedroom atsubstationsites,
whichcanprecludebreakerupgrades.
Theprimaryneed,asexpressedbymanagementoftheTokyoElectricPower
Company (TEPCO),is fora limiterforthe nucleus ofthe Japanese
transmissionsystem,the500kVtransmissiongrids.Inresponsetothisreal
marketpulltherehasbeenaseriesofprogramstodevelopfaultcurrent
limitersusingavarietyofmethods,withrecentfocusonsuperconducting
limiters(Nakade1994).AlthoughFCLsarenotacomponentoftheNEDO
budget,TEPCOhasreportedthatitspendsabout¥100millionperyear(~$1
million)onthisprogram,andsomeresistiveFCLworkisapparentlyincluded
intheNEDObudgetunderthetopic"ResearchofSuperconductingMaterials
andDevices”.Inthelate1980s,SeikeiUniversitymanufacturedasmall-scale
three-phasecurrentlimitingreactoranddemonstratedsuccessfuloperation.
Thisthree-phasesystem introducesalargeunbalancedreactanceinthe
system tolimitcurrentsinthecaseofasingle-phaseshortandquenchesto
introduceresistanceinthecircuitinthecaseofathree-phasefault.

24. 24
MitsubishiElectricCompany(MELCO)hasbeenparticipatinginaMITI/NEDO
FCL
programsince1990.ThisisaresistivelimiterapproachusingHTSfilmsona
strontiumtitanatesubstratethathasdemonstratedlimitingof400Acurrents
to11.3A.TheCentralResearchInstituteoftheElectricPowerIndustry
(CRIEPI)hasdevelopedtheinductivelimitershowninFig.4.11(Ichikawaand
Okazaki1995).Thisapproach,similartothoseofABBandSiemens-Hydro
Quebec,usesacylinderofbulkBSCCO-2212orBSCCO-2223toseparatea
normalcoppercoilfrom anironcore.Innormaloperation,thefieldfrom the
coppercoildoesnotpenetratethesuperconductor;underfaultconditions,
however,thecurrentinducedinthesuperconductorissufficienttodriveit
normal,andthemagneticfieldlinkstheironyoke.Thisgreatlyincreasesthe
inductanceofthecoppercoil,thusprovidingcurrentlimiting.CRIEPIwork
hasfocusedonacmagneticshieldingperformanceofbulksuperconductors
andtheirresponsestofaultcurrents.
Inaddition,introductionofa"controlring"inthesystem toabsorbsomeof
theenergydepositedduringafaulthasreducedthecooldowntimeofthe
shieldfollowingafaultedstate.ThemostextensiveFCLprogram inJapan
hasbeenthecollaborationbetweenTEPCOandToshiba.Thelong-term goal
ofthisprogram isthedevelopmentofa500kVlimiterwitharatedcurrentof
8,000A.Initialdevelopmenthasbeenfocusedonadistributionlevellimiter
designedfor6.6kV.

25. 25
Fig.(2.9.1)-SchematicdiagramoftheCRIEPIinductiveFCL
AsshowninFig.4.12,theFCLisformedbyconnectingfoursuperconducting
coilsinaseries-parallelconfigurationsothetotalinductanceisminimized.
Onesetofcoilsisused foreach phaseofthedevice,and limiting is
accomplishedbyquenchingthecoils.
ThecurrentversionoftheFCLshowninFig.4.13usesaspeciallowacloss
Nb-Ti
conductor.Testsinacircuitwithanominalshortcircuitcurrentof25.8kA
havesuccessfullydemonstratedlimitingtoabout4,000amps(Fig.4.14).

26. 26
Fig.(2.9.2)-ConfigurationofcoilsintheTEPCO/ToshibaFCL
RecentworkhasincludedtheintroductionofHTScurrentleadstoreducethe
refrigerationloadofthesystem tolevelsthatcanbehandledbya4KGifford
McMahonrefrigerator.[3]
Fig.(2.9.3)-Exteriorviewofthe6.6kV2,000A-classcurrentlimiter

27. 27
Overthreegenerationsofthedevice,theheatleakhasbeenreducedfrom
13.8wattsto3.4watts,whichisnearingtherequiredlevel.
Fig.(2.9.4)-CurrentlimitingcharacteristicsofToshibaFCL
CHAPTER-3
LighteningProtection
3.1Componentsofalightningprotectionsystem
Lightningrodsor'airterminals'areonlyasmallpartofacompletelightning
protectionsystem.Infact,therodsmayplaytheleastimportantroleina
system installation.Alightningprotectionsystem iscomposedofthreemain
components:
3.1.1RodsorAirTerminals
Thesmall,verticalprotrusionsdesignedtoactasthe'terminal'foralightning

28. 28
discharge.Rodscanbefoundindifferentshapes,sizesanddesigns.Most
aretoppedwithatall,pointedneedleorasmooth,polishedsphere.The
funtionalityofdifferenttypesoflightningrods,andeventheneccessityof
rodsaltogether,aresubjectsof
manyscientificdebates.
3.1.2ConductorCables
Heavycables(right)thatcarrylightningcurrentfrom therodstotheground.
Cablesarerunalongthetopsandaroundtheedgesofroofs,thendownone
ormorecorners
ofabuildingtothegroundrod(s).
3.1.3GroundRods
Long,thick,heavyrodsburied deep into theearth around a protected
structure.The conductorcablesareconnectedtotheserodstocompletea
safepathforalightningdischargearoundastructure.
Theconductorcablesandgroundrodsarethemostimportantcomponents
ofa lightning protection system,accomplishing the main objective of
diverting lightning currentsafely pasta structure.The 'lightning rods'
themselves,thatis,thepointyvertically-orientedterminalsalongtheedgesof
roofs,donotplaymuchofaroleinthefunctionalityofthesystem.Afull
protectionsetup,givengoodcablecoverageandgoodgrounding,wouldstill
worksufficientlywithouttheairterminals.

29. 29
Fig.(3.1)-Lighteningsurge
3.2Lightningprotectionsystems-Whattheydoanddon'tdo
Alightningprotectionsystem'sonlypurposeistoensuresafetytoabuilding
anditsoccupantsiflightninghappenstohititdirectly,ataskaccomplished
byprovidingagood,safepathtogroundforthelightningtofollow.Contrary
tothemyths,lightningprotectionsystems:
 Don'tattractlightning
 Don'tandcannotdissipateorpreventlightningby'draining'astormofits
charge
 Mostdon'toffersurgeprotectionforsensitiveelectronics
 Doofferfireprotectionandstructuraldamageprotectionbypreventingahot,
explosivelightningchannelfrompassingthroughbuildingmaterials
3.2.1Howalightningprotectionsystemworks
Withoutadesignatedpathtoreachground,alightningstrikemaychooseto
insteadutilizeanyconductoravailableinsideahouseorbuilding.Thismay

30. 30
includethephone,cable,orelectricallines,thewaterorgaspipes,or(inthe
caseofasteel-framedbuilding)thestructureitself.Lightningusuallywill
followoneormoreofthesepathstoground,sometimesjumpingthroughthe
airviaasideflashtoreachabetter-groundedconductor(watchanimation
above).Asaresult,lightningpresentsseveralhazardstoanyhouseor
building.
 Fire
Firecanstartanywheretheexposedlightningchannelcontacts,penetrates
orcomesnearflammablematerial(wood,paper,gaspipes,etc)inabuilding
-includingstructurallumberorinsulationinsidewallsandroofs.When
lightningfollowselectricalwiring,itwilloftenoverheatorevenvaporizethe
wires,creatingafire.
 Sideflashes
Sideflashescanjumpacrossrooms,possiblyinjuringanyonewhohappens
tobeintheway.Theycanalsoignitematerialssuchasagasolinecanina
garage.
 Damagetobuildingmaterials
Theexplosiveshockwavecreatedbyalightningdischargecanblow out
sectionsofwalls,fragmentconcreteandplaster,andshatternearbyglass.
 Damagetoappliances
Televisions,VCRs,microwaves,phones,washers,lampsandjustabout

31. 31
anythingpluggedintoanaffectedcircuitmaybedamagedbeyondrepair.
Electronicdevicesandcomputersareespeciallyvulnerable.
Addingaprotectionsystem doesn'tpreventastrike,butgivesitabetter,
saferpathtoground.Theairterminals,cablesandgroundrodsworktogether
tocarrytheimmensecurrentsawayfrom thestructure,preventingfireand
mostappliancedamage.
3.2.2Lightningprotectionfacts
Rodsandprotectionsystemsdon'tattractlightning,nordotheyinfluence
wherelightningwillstrike.Rodsorprotectionsystemsdonotandcannot
preventlightning,norcanthey'discharge'thunderstorms.
Lightning protection systems(including placementofrods,cables,and
groundings)are custom-designed forindividualstructures and require
complexengineeringtofunctionproperly.Theyshouldonlybeinstalledby
qualifiedcontractors.
Lightningprotectionsystemsdonotalwayspreventdamagetoelectronicsor
computers.Youshouldstillunplugsuchdevicesduringthunderstormsto
ensuresufficientprotection.
3.2.3Lightningdissipation/eliminationmyths
Productscalled'lightningelimination'or'lightningdissipation'deviceshave
arisenasaresultoftwomyths:one,thatathunderstorm'schargecanbe
drainedorotherwiseaffectedbyobjectsontheground,andtwo,cloud-to-
groundlightningdischargesbeginfrom theground.Theseproducts,thatare
stillbeingsoldtoday,claim tobeabletopreventadirectlightningstriketo
anyobjectonwhichtheyareinstalled.Thedeviceshavewidelyvarying

32. 32
appearances,butusuallyarecharacterizedbyametallicframewithhundreds
ofsharp-pointedbristles,needlesorthinrods.Theframedesignsrangefrom
comb-liketoumbrella-shaped.
Thedevicesaresaidtopreventorreducedirectlightningstrikestoobjects
onwhichtheyareinstalled,usingcoronadischargetoperformoneormoreof
thefollowing:1.)todrainastorm ofitschargebeforelightningcanoccur,2.)
tocreatealocalized'spacecharge'overtheprotectedareathatdiverts
lightningstrikes,or3.)tomakeinitiationofupwardleadersfrom theobject
moredifficult,therebyreducingthechancesofadirectsteppedleader-
groundleaderconnection.
Aswediscussedinourarticleaboutthunderstorm chargedissipation,the
problemwiththesedevicesisthatwhiletheydocreatecoronadischarge,the
rateofcharge'leakage'iscompletelyinsignificantincomparisontotherate
of charge generation in the 10-mile-high,15 to 25 mile-diameter
thunderstorm overhead!Noamountofman-madecoronadischargeonsuch
asmallscalehastheslightestchanceofdrainingchargefasterthana
gargantuanthunderstorm cloudisproducingit.Andalthoughsmall-scale
coronadoeshelppreventtheinitiationoflaboratory-generatedsparks(such
asfromVandeGraaffgenerators),thiscannotbeextrapolatedtoapplytofull
-sizedlightningdischarges,whichareseveralthousandtimeslargerthanthe
artificalcounterparts(seeourarticleoncomparingartificialandnatural
lightning).Coronadischargefrom small'dissipators'isinsignificanttoafull-
sizedthunderstorm andwilldonothingtoaltertheoccurenceorbehaviorof
lightninginitsgeneeralvicinity.
Cloud-to-groundlightningstrokesinitiatehighinthunderstorms,milesabove
thesurfacewheregroundobjectshavenoeffect.Evenafterinitiationofthe

33. 33
discharge,thedownward-movingsteppedleaderis'blind'toobjectsonthe
grounduntilitisveryclosetotheground,within50to100feet.Atthat
distance,lightning willstrike within the very smallarea itis already
descendingin,regardlessofanydevicesnearbythatclaim todivertor
preventthestrike.Forexample,aphotographexistsofalightningstriketo
theMerchandiseMartbuildingindowntownChicago.MerchandiseMartis
veryclosetothe1,700foottallSearsTower,yetnoteventheSearsTower
influencedthegroundconnectionofthisclosecloud-to-groundstroke.
Inadditiontotheobviousscientificflawswiththeconceptoflightning
'dissipation'and'elimination'devices,theyhavebeenproventobeineffective
inreal-worldinstallations.Many'lightningdissipation'devicesontowersand
buildingshavebeenstruckdirectly.Despitetheevidence,theycontinuetobe
sold,installedandpromoted.
3.3FuturePlans
TEPCOwilldevelopathree-phaselimiteroverthenextthreetofouryearsand
testitinthegridwithinthiscentury.Therearefew distribution-levelFCL
applicationsseenintheTEPCO grid,however,andthecurrentplanisto
introduce solid state breakers for distribution before installing
superconductiveFCL.Thetrueapplicationforthe
superconductingFCLisattransmissionvoltagesof500kV.Theview of
TEPCOresearchersisthatthisvoltagerangewillrequiretheintroductionof
HTScoils(rather
thanLTS)toeliminatethehelium gasfrom thesystem.Introductionofa
transmissionlevelFCLonthegridisanticipatedabout2010.
3.4Fault-CurrentLimitersInEurope

34. 34
By farthe mostcomprehensive FCL program in Europe is thatbeing
conductedby
collaboration between Electricité de France,GEC Alsthom,and Alcatel
Alsthom
Recherché.Theprogram'smaingoalistoprovideFCLsforthe225kVgridin
France.ThegrouphaschosenaresistivelimiterbasedonLTSmaterialand
hasdemonstratedeffectiveoperationat40kV (rms),withanindustrial
demonstrationontheFrench63kVgridexpectedin1998.Evaluationofthe
Frenchprogram isbeyondthescopeofthisWTECstudy,sonovisitwas
madetothisproject.Verhaegeetal.(1996)provideanoverview ofthe
technologyandprojectstatus.
3.5FCLPrograms
TwositestheWTECpanelvisitedinEuropeaddressedFCL:ABBinBaden-
Daetwil,
Switzerland,andSiemensinErlangen,Germany.ABBispursuingafault-
currentlimiterconceptverysimilartothatdescribedabovefortheCRIEPI
program.Itisreferredtoasthe"shieldedironcoreconcept."Itusesawarm
ironcoreenclosedbyasuperconductingshieldinafiberglassDewar.The
copperprimarycoiliswoundexternaltothisDewar.ABBhasconstructed
andtesteda100kWprototypeusingastackoffourBi-2212rings8cm long,
and20cm indiameter.Operationwasat480Vwithfaultcurrentsof8kA.A
newABBthree-phase1.2MW FCLisnowinoperationinapowerstationin
Löntsch,Switzerland.
SiemensisfollowingtworoutesforFCLinacollaborativeprogram with
Hydro-QuebecCanada.AttheSiemenscorporatelabsinErlangen,thefocus
hasbeenonresistivelimitersusingYBCOthinfilm meanderlinesonYSZor
onYSZandsapphire(Gromolletal.1996).Theadvantageofthisapproachis

35. 35
thattheYBCOfilm hasahighnormalstateresistanceandisnotshuntedby
normalmetal,as would be the case in a composite powder-in-tube
conductor.Thefilm alsohasverylow heatcapacity,whichleadstorapid
switchingtothenormalstate(<1ms)andthepossibilityofrapidcooldown.
Analysisasof1996hasdeterminedthatbothpeaklet-throughcurrentand
steadystatelimitingcurrentdecreaseasJcisraised.Inaddition,thedesign
ofalimiterofusablesizedependsstronglyonJc--higherJcenablesamore
compactdesign.
Themajorfocusoftheprogram has,therefore,beenthefabricationof
uniform high-Jc films ofYBCO.Techniques investigated have included
pulsed laserdeposition (PLD),thermalco evaporation,and magnetron
sputteringonbufferedp-YSZ,unbufferedp-YSZ,andsapphire.Biaxially
textured YSZ bufferlayershavebeen fabricated on partofthep-YSZ
substratesbyionbeam assisteddeposition.Currentdensitiesupto3x106
A/cm2havebeenachieved,ashavegoodlimitingperformanceandrecovery
timeson theorderof1 second.Thenextmilestonefortheprojectis
constructionofa100KVAlimiterusingacrycooler.Furtherdetailsofthis
programaregivenintheSiemenssitevisitreport(AppendixD).
TwoadditionalGermanFCLprojectsbeganinJanuary1997.Thefirstisa
system studythatwillbefollowedbyconstructionofademonstrationFCL.
ThisprojectisajointeffortbytheGermanutilitiesRWE,VEW,andBadenwerk,
andbyEUSGmbHandFZK.Thesecondprojectinvolvingthedevelopmentof
a smallinductive limiteris underthe auspices ofthe German Israel
Foundation.TheGermanparticipantsareFZK,HoechstAG,andtheutility
Badenwerk;theIsraeliparticipantsareTelAvivandBenGurionUniversities.
TheworkatHydro-Quebechasresultedintheconstructionandtestofa

36. 36
numberofdevicessince1992(Fig.4.15).Thelatestsystem operatedat450
Vand95ampsforanominalpowerof43KVA.Twodifferentmaterialswere
evaluatedforthesuperconductingshield:melt-castBi-2212from Hoechst,
andcompositereactiontextured(CRT)materialfrom Cambridge.Although
successfulcurrentlimiting wasdemonstrated,thelimiterthatused the
Hoechstmaterialfailedduringa480Vshortcircuittestduetoafractureof
thesuperconductor(Caveetal.1996).SubsequentanalysisbyHydro-
Quebecindicatedthatthermalstressinthebulksuperconductorgaveriseto
thefailure.Thenear-term futuredirectionofthisprogram willbeconcerned
withimprovingthehomogeneity,criticalcurrentdensity,andresistivityofthe
bulksuperconductor.
CHAPTER-4
ADVANTAGES,DISADVANTAGESAND
LIMITATIONS
4.1ADVANTAGES

37. 37
Fig.(4.1)-Powerratingoftheinductivelimitermodelsbuilt/testedatHydro-Quebec
 Relativelynarrow superconducting wirescan beused to carryhuge
currents.
 Lessfuelrequiredtogenerateelectricitywhichwillleadtoareductionin
costs
 Superconductingcableswillbesmallerandcanfitintoexistingconduits
for expansionofthepowersupply.
 Environmentalbenefits from less pollution and more efficentpower
production
4.1.1TransformingtheElectricityGrid

38. 38
Theelectricpowergridisamongthegreatestengineeringachievementsof
the20thcentury.Demand,however,isabouttooverwhelm it.Forexample,
thenorthAmericanblackoutof2003,whichlastedaboutfourdays,affected
over50millionpersonsandcausedabout$6billionineconomicloss.
Superconductor technology provides loss-less wires and cables and
improvesthereliabilityandefficiencyofthepowergrid.Plansareunderway
toreplaceby2030thepresentpowergridwithasuperconductingpowergrid.
Asuperconductingpowersystem occupieslessrealestateandisburiedin
theground,quitedifferentfrompresentdaygridlines.[13]
4.1.2ImprovingWide-BandTelecommunication
Wide-bandtelecommunicationstechnology,whichoperatesbestatgigahertz
frequencies,isveryusefulforimprovingtheefficiencyandreliabilityofcell
phones.Suchfrequenciesareverydifficulttoachievewithsemiconductor-
based circuitry.However,they have been easily achieved by Hypres's
superconductor-basedreceiver,usingatechnologycalledrapidsingleflux
quantum,orRSFQ,integratedcircuitreceiver.Itoperateswiththeaidofa4-
kelvincryocooler.Thistechnologyisshowingupinmanycellphonereceiver
transmittertowers.
4.1.3AidingMedicalDiagnosis
Oneofthefirstlarge-scaleapplicationsofsuperconductivityisinmedical
diagnosis. Magnetic resonance imaging, or MRI, uses powerful
superconductingmagnetstoproducelargeanduniform magneticfields
inside the patient's body.MRIscanners,which contain liquid helium
refrigerationsystem,pickuphow thesemagneticfieldsarereflectedby
organs in the body.The machine eventually produces an image.MRI
machinesaresuperiortox-raytechnologyinproducingadiagnosis.Paul

39. 39
LeuterburandSirPeterMansfieldwereawardedthe2003Nobelprizein
physiology or medicine,"for their discoveries concerning magnetic
resonanceimaging,"underlyingthesignificanceofMRI,andbyimplication
superconductors,tomedicine.
4.2LIMITATIONS
 Thereisamaximumcurrentthatsuperconductingmaterialscancarry.
 Costisprohibitiveforimmediatereplacementofexistingtechnologies.
 DevelopingcountrieswillnotbeabletoaffordthetechnologyAboveacritical
currentdensity.
 superconductivitybreaksdownlimitingcurrent.
 Low criticaltemperaturesaredifficult,expensiveandenergyintensiveto
maintain.
 Thematerialsareusuallybrittle,notductileandhardtoshape.
 Theyarealsochemicallyunstableinsomeenvironments.
 ItcannotfunctionwithACelectricity,astheswitchinginACdestroysCooper
pairs.
 Thereisa"limit"tothecurrentpassingthroughthematerialbeforeitlosesits
superconductingproperties.
4.3DISADVANTAGES
 Superconductingmaterialssuperconductonlywhenkeptbelow agiven
temperaturecalledthetransitiontemperature.
 Forpresentlyknownpracticalsuperconductors,thetemperatureismuch
below77Kelvin,thetemperatureofliquidnitrogen.Keepingthem belowthat

40. 40
temperatureinvolvesalotofexpensivecryogenictechnology.[13]
 Thus,superconductorsstilldonotshow upinmosteverydayelectronics.
Scientistsareworkingondesigningsuperconductorsthatcanoperateat
roomtemperature.
 Thegreatestdrawbackofsuperconductorsisthattheyonlyfunctionassuch
attemperatureslowerthanitscriticaltemperature.
 Thistemperaturevariesbutistypicallyaround70Kelvinformostcommonly
usedsuperconductors.
 Thereforeanysuperconductingapplicationisgenerallycoupledwithsome
sortofactiveorpassivecryogeniccooling.
 Otherdrawbacksincludeprice,materialhandling,maximum currentcarrying
capacityEtc.butthecryogeniclimitationmustbethebiggest.
 This is why the search for the near-mythical ‘room temperature
superconductor’ is so important for the future of superconducting
applications.
4.3.1Highertier
Atthemoment,superconductorsonlyworkatverylowtemperatures.They
havetobekeptverycoldwithliquidnitrogenorliquidhelium.Alotofworkis
goingintodevelopingsuperconductorsthatwillworkatnormaltemperatures.
Untilthishappens,theiruseswillbelimited.
4.3.2Highmeltingandboilingpoints
Metallicbondsarestrongandalotofenergyisneededtobreakthem.Thisis
whymetalshavehighmeltingpointsandboilingpoints.
4.3.3Conductingelectricity

41. 41
Metalscontainelectronsthatarefreetomoveinthemetalstructure,carrying
chargefromplacetoplaceandallowingmetalstoconductelectricitywell.
4.4.4Metallicbonding-Highertier
Metallicbondingisthestrongattractionbetweencloselypackedpositive
metalionsanda'sea'ofdelocalisedelectrons.Theattractionbetweenthe
metalionsandthedelocalisedelectronsmustbeovercometomeltortoboil
ametal.Someoftheattractionsmustbeovercometomeltametalandallof
them mustbeovercometoboilit.Theseattractiveforcesarestrong,so
metalshavehighmeltingandboilingpoints.
Thedelocalisedelectronsareabletomovethroughthemetalstructure.
Whenapotentialdifferenceisapplied,theywillmovetogether,allowingan
electriccurrenttoflowthroughthemetal.

42. 42
CHAPTER-5
APPLICATIONS
5.1BasicApplications
 Theproductionofsensitivemagnetometersbasedonsquids
 Fastdigitalcircuits(includingthosebasedonJosephsonjunctionsandrapid
singlefluxquantumtechnology),
 Powerfulsuperconductingelectromagnetsusedinmaglevtrains,Magnetic
ResonanceImaging(MRI)andNuclearmagneticresonance(NMR)machines,
magnetic confinementfusion reactors (e.g.Tokamaks),and the beam-
steeringandfocusingmagnetsusedinparticleaccelerators
 Low-losspowercables
 RFandmicrowavefilters(e.g.,formobilephonebasestations,aswellas
militaryultra-sensitive/selectivereceivers)
 Fastfaultcurrentlimiters
 Highsensitivityparticledetectors,includingthetransitionedgesensor,the
superconductingbolometer,thesuperconductingtunneljunctiondetector,
thekineticinductancedetector,andthesuperconductingnanowiresingle-

43. 43
photondetector
 Railgunandcoilgunmagnets
 Electricmotorsandgenerators
5.1.1Lowtemperaturesuperconductivity
Thebiggestapplication forsuperconductivityisin producing thelarge
volume,stable,andhighmagneticfieldsrequiredforMRIandNMR.This
represents a multi-billion US$ marketforcompanies such as Oxford
Instruments and Siemens.The magnets typically use low temperature
superconductors(LTS)becausehigh-temperaturesuperconductorsarenot
yetcheapenoughtocost-effectivelydeliverthehigh,stableandlargevolume
fieldsrequired,notwithstandingtheneedtocoolLTSinstrumentstoliquid
helium temperatures.Superconductorsarealsousedinhighfieldscientific
magnets.
5.1.2Particleacceleratorsandmagneticfusiondevices
ParticleacceleratorssuchastheLargeHadronCollidercanincludemany
highfieldelectromagnetsrequiringlargequantitiesofLTS.Toconstructthe
LHCmagnetsrequiredmorethan28percentoftheworld’sniobium-titanium
wireproductionforfiveyears,withlargequantitiesofNbTialsousedinthe
magnetsfortheLHC’shugeexperimentdetectors.
[2]
Asmallnumberofmagneticfusiondevices(mostlytokamaks)haveusedSC
coils.ThecurrentconstructionofITERhasrequiredunprecedentedamounts
ofLTS(eg.500tonnes,causinga7foldincreaseinworldsannualproduction
capacity).
[3]
5.1.3High-temperaturesuperconductivity(HTS)

44. 44
Thecommercialapplicationssofarforhightemperaturesuperconductors
(HTS)havebeenlimited.
HTScansuperconductattemperaturesabovetheboilingpointofliquid
nitrogen,which makes them cheaper to coolthan low temperature
superconductors(LTS).However,theproblem withHTStechnologyisthat
thecurrentlyknownhightemperaturesuperconductorsarebrittleceramics
whichareexpensivetomanufactureandnoteasilyformedintowiresorother
usefulshapes.
[4]
ThereforetheapplicationsforHTShavebeenwhereithas
someotherintrinsicadvantage,e.g.in
 LowthermallosscurrentleadsforLTSdevices(lowthermalconductivity),
 RFandmicrowavefilters(lowresistancetoRF),and
 Increasinglyinspecialistscientificmagnets,particularlywheresizeand
electricityconsumptionarecritical.
 WhileHTSwireismuchmoreexpensivethanLTSintheseapplications,this
canbeoffsetbytherelativecostandconvenienceofcooling.
 Theabilitytorampfieldisdesired(thehigherandwiderrangeofHTS's
operatingtemperaturemeansfasterchangesinfieldcanbemanaged);or
cryogenfreeoperationisdesired(LTSgenerallyrequiresliquidhelium thatis
becomingmorescarceandexpensive).[14]
5.1.4HTS-basedsystems
HTShasapplicationinscientificandindustrialmagnets,includingusein
NMR andMRIsystems.Commercialsystemsarenow availableineach
category.
[5]
AlsooneintrinsicattributeofHTSisthatitcanwithstandmuchhigher
magneticfieldsthanLTS,soHTSatliquidhelium temperaturesarebeing

45. 45
exploredforveryhigh-fieldinsertsinsideLTSmagnets.Promisingfuture
industrialand commercialHTS applications include Induction heaters,
transformers,faultcurrentlimiters,powerstorage,motorsandgenerators,
fusionreactors(seeITER)andmagneticlevitationdevices.
Earlyapplicationswillbewherethebenefitofsmallersize,lowerweightor
theabilitytorapidlyswitchcurrent(faultcurrentlimiters)outweighsthe
addedcost.Longer-term asconductorpricefallsHTSsystemsshouldbe
competitiveinamuchwiderrangeofapplicationsonenergyefficiency
groundsalone.(ForarelativelytechnicalandUS-centricviewofstateofplay
ofHTS technology in powersystems and the developmentstatus of
Generation2conductor.
CHAPTER-6
FUTUREASPECTS
6.1SuperconductingTransmissionLines
Since10%to15%ofgeneratedelectricityisdissipatedinresistivelossesin
transmissionlines,theprospectofzerolosssuperconductingtransmission
lines is appealing.In prototype superconducting transmission lines at
BrookhavenNationalLaboratory,1000MW ofpowercanbetransported
withinanenclosureofdiameter40cm.Thisamountstotransportingthe
entireoutputofalargepowerplantononeenclosedtransmissionline.This
couldbeafairlylowvoltageDCtransmissioncomparedtolargetransformer
banksandmultiplehighvoltageAC transmissionlinesontowersinthe

46. 46
conventionalsystems. The superconductor used in these prototype
applications is usually niobium-titanium,and liquid helium cooling is
required.
Current experiments with power applications of high-temperature
superconductorsfocusonusesofBSCCOintapeformsandYBCOinthinfilm
forms.Currentdensitiesabove10,000amperespersquarecentimeterare
considerednecessaryforpracticalpowerapplications,andthisthresholdhas
beenexceededinseveralconfigurations.
6.2PowerApplications,HighTc
Powerapplicationsofhightemperaturesuperconductorswouldhavethe
majoradvantageofbeingabletooperateatliquidnitrogentemperature.The
biggestbarriertotheirapplicationhasbeenthedifficultyoffabricatingthe
materialsintowiresandcoils.CurrentdevelopmentfocusesonBSCCOand
YBCOmaterials.
6.3Fault-CurrentLimiters
High fault-currents caused by lightning strikes are a troublesome and
expensivenuisanceinelectricpowergrids.Oneofthenear-term applications
forhigh temperaturesuperconductorsmaybetheconstruction offault-
currentlimiterswhichoperateat77K.Theneedistoreducethefaultcurrent
toafractionofitspeakvalueinlessthanacycle(1/60sec).
Arecentlytestedfault-currentlimitercanoperateat2.4kVandcarryacurrent
of2200amperes.ItwasconstructedfromBSCCOmaterial.

47. 47
6.4SuperconductingMotors
Superconductingmotorsandgeneratorscouldbemadewithaweightof
aboutonetenththatofconventionaldevicesforthesameoutput.Thisisthe
appealofmaking such devicesforspecialized applications.Motorsand
generatorsarealreadyveryefficient,so thereisnotthepowersavings
associatedwithsuperconductingmagnets.Itmaybepossibletobuildvery
large capacity generators for power plants where structuralstrength
considerationsplacelimitsonconventionalgenerators.
In1995theNavalResearchLaboratorydemonstrateda167hpmotorwith
high-Tcsuperconductingcoilsmadefrom Bi-2223.Itwastestedat4.2Kand
atliquid neon temperature,28K with 112 hp produced atthe higher
temperature.
6.5SuperconductingMaglevTrains
Whileitisnotpracticaltolaydownsuperconductingrails,itispossibleto
constructasuperconductingsystem onboardatraintorepelconventional
railsbelowit.Thetrainwouldhavetobemovingtocreatetherepulsion,but
oncemovingwouldbesupportedwithverylittlefriction.Therewouldbe
resistivelossofenergyinthecurrentsintherails.Ohanianreportsan
engineeringassessmentthatsuchsuperconductingtrainswouldbemuch
saferthanconventionalrailsystemsat200km/h.
AJapanesemagneticallylevitatedtrainsetaspeedrecordof321mi/hin
1979 using superconducting magnetson board thetrain.Themagnets
inducecurrentsintherailsbelowthem,causingarepulsionwhichsuspends
thetrainabovethetrack.

48. 48
 FutureApplicationsofSuperconductivity
With such features as zero resistivity and high current density,
superconductivity provides low-loss operation and high magnetic field,
featuresinconceivablewithnormalconductivity.Accordingly,expectations
arehighthatsuperconductivitywillimprovetheperformanceofelectrical
appliances.
Thesuperconductingstateoccurswithinlimitedtemperature,magneticfield
and current density ranges. Thanks to the discovery of oxide
superconductorsofhighcriticaltemperatures*1andtheincreasedcritical
current density*2 of superconducting wires made from them,
superconductivityisexpectedtobeusedinabroaderrangeofcommercial
fields.
Futuristicideasfortheuseofsuperconductors,materialsthatallowelectric
currenttoflow withoutresistance,aremyriad:long-distance,low-voltage
electricgridswithnotransmissionloss;fast,magneticallylevitatedtrains;
ultra-high-speed supercomputers;superefficientmotors and generators;
inexhaustiblefusionenergy–andmanyothers,someintheexperimentalor
demonstrationstages.
Butsuperconductors,especiallysuperconductingelectromagnets,havebeen
around for a long time.Indeed the first large-scale application of
superconductivity was in particle-physics accelerators,where strong
magnetic fields steerbeams ofcharged particles toward high-energy
collisionpoints.

49. 49
Accelerators created the superconductorindustry,and superconducting
magnetshavebecomethenaturalchoiceforanyapplicationwherestrong
magneticfieldsareneeded– formagneticresonanceimaging(MRI)in
hospitals,forexample,orformagneticseparationofmineralsinindustry.
Otherscientificusesarenumerous,from nuclearmagneticresonancetoion
sourcesforcyclotrons.
Someofthestrongestandmostcomplexsuperconductingmagnetsarestill
builtforparticleacceleratorslikeCERN’sLargeHadronCollider(LHC).The
LHC uses over1,200 dipole magnets,whose two adjacentcoils of
superconducting cable create magnetic fields thatbend proton beams
traveling in opposite directions around a tunnel 27 kilometers in
circumference;theLHCalsohasalmost400quadrupolemagnets,whose
coilscreateafieldwithfourmagneticpolestofocustheprotonbeamswithin
thevacuumchamberandguidethemintotheexperiments.
TheseLHCmagnetsusecablesmadeofsuperconductingniobium titanium
(NbTi),andforfiveyearsduringitsconstructiontheLHCcontractedformore
than 28 percentofthe world’s niobium titanium wire production,with
significantquantitiesofNbTialsousedinthemagnetsfortheLHC’sgiant
experiments.
What’smore,althoughtheLHCisstillworkingtoreachtheenergyforwhichit
wasdesigned,theprogram toimproveitsfutureperformanceisalreadywell
underway.
 Designingthefuture
“Enablingtheacceleratorsofthefuturedependsondevelopingmagnetswith
muchgreaterfieldstrengthsthanarenowpossible,”saysGianLucaSabbiof

50. 50
BerkeleyLab’sAcceleratorandFusionResearchDivision(AFRD).“Todothat,
we’llhavetousedifferentmaterials.”
Fieldstrengthislimitedbytheamountofcurrentamagnetcoilcancarry,
whichinturndependsonphysicalpropertiesofthesuperconductingmaterial
suchasitscriticaltemperatureandcriticalfield.Mostsuperconducting
magnetsbuilttodatearebasedonNbTi,whichisaductilealloy;theLHC
dipolesaredesignedtooperateatmagneticfieldsofabouteighttesla,or8
T —hundredsofthousandsoftimeshigherthanEarth’smagneticfield.
TheLHCAcceleratorResearchProgram (LARP)isacollaborationamong
DOElaboratoriesthat’sanimportantpartofU.S.participationintheLHC.
SabbiheadsboththeMagnetSystemscomponentofLARPandBerkeley
Lab’s Superconducting MagnetProgram.These programs are currently
developing acceleratormagnetsbuiltwith niobium tin (Nb3Sn),abrittle
materialrequiringspecialfabricationprocessesbutabletogenerateabout
twicethefieldofniobium titanium.Yetthegoalformagnetsofthefutureis
alreadysetmuchhigher.
“Amongthemostpromisingnewmaterialsforfuturemagnetsaresomeof
thehigh-temperaturesuperconductors,”saysSabbi.“Unfortunatelythey’re
verydifficult

51. 51
CONCLUSION
Thepurposeofthispresentationwasthestudyofsurgecurrentprotection
usingSuperconductors.TheSuperconductorFaultCurrentLimitersoffers
efficientadvantagestopowersystemsandopensupamajorapplicationfor
superconductingmaterials.
Surge suppressors should be used as a mailer of habit with all
semiconductorbased
electronicandcomputerhardwareincludingperipheralssuchasprinters
monitors,
externaldiskdriversandothers.Butitcan’tbereliedupontoprovide
protectionagainstlightninginducedtransients.Sothesafestprocedureto
ensurethatallsusceptiblehardwareistounplugthesuppressormainpower
cordduringlightning.

52. 52
References
[1] KEGray,DEflower–superconductingfaultcurrentlimiters
[2] IEEEtransactiononappliedsuperconductivity,march1997
[3] HMRosenberg–TheSolidState.http://www.amazon.co.uk/Solid-State
Introduction-MaterialsEngineering
[4] CPPoole,HAFarachandRJCreswick,Superconductivity(Academic
PressInc,
[5] SanDiego,California,1995(~
£40)http://www.amazon.co.uk/SuperconductivityCharles-PPoole/
[6] SuperconductivitybyW.Buckel,ReinholdKleiner
[7] Superconductivity:PhysicsandApplicationsbyKristianFossheim,Asle
Sudboe
[8] Superconductivity:fundamentalsandapplicationsbyWernerBuckel
[9] ieeexplore.ieee.org›...›Spectrum,IEE
[10]http://www.scribd.com/doc/115890153/surge-current-protection-using-
superconductors
[11]http://jntuhome.com/surge-current-protection-using-superconductors-
seminardownload-full-paper-eee-seminar-topics/

53. 53
[12]http://kguru.info/t-surge-current-protection-using-superconductors-ppt--
55999
[13]http://en.wikipedia.org/wiki/Surge_protector
[14]http://www.edaboard.com/thread126937.html
[15]http://image.slidesharecdn.com/surgesupressor2bypratyashapatra-
140216062041-phpapp02/95/surge-supressor-21-638.jpg?cb=1392531698