FACTS UNIT-I KITS AS PER KITS R20 SYLLABUS

FACTS UNIT-I KITS

1. 1
FLEXIBLEALTERNATING
CURRENTTRANSMISSION
SYSTEMS
.
Presented By :
HARI MADHAVA REDDY. Y (Ph.D)., M.Tech., MISTE., SSI., IAENG
Assistant professor
DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

2. 2
Contents
Unit–I: Introduction to FACTS
Unit–II:Objectives of shunt and Series Compensation
Unit–III:Shunt Compensators
Unit–IV:Series Compensators
Unit V:Combined Controllers

3. About
COURSE
OBJECTIVES
introduction
lesson1
Lesson 2 Lesson 3
FLEXIBLE
ALTERNATING
CURRENT
TRANSMISSION
SYSTEMS

4. Course
objective
introduction
lesson1Lesson 2 Lesson 3
Presented by:
HARI MADHAVA REDDY.Y
M.Tech., ISTE., IAENG., SSI
ASSISTANT PROFESSOR
DEPT. of EEE
About

5. About
Tolearnthebasicsofpowerflow
controlintransmissionlinesusing
FACTScontrollers
Toexplainoperationandcontrolofvoltage
sourceconverter.
Tounderstandcompensationmethods
toimprovestabilityandreducepower
oscillationsofapowersystem.
Tolearnthemethodofshuntcompensation
usingstaticVARcompensators.
Tolearnthemethodsofcompensation
usingseriescompensators
ToexplainoperationofUnifiedPower
FlowController(UPFC).
COURSE
OBJECTIVES
introduction
lesson1
Lesson 2 Lesson 3 Lesson
4
Lesson 5

6. Lesson
1
Introduction to
FACTS
Lesson
2
Voltage
source and
Current
source
converters
Lesson
3
FLEXIBLE ALTERNATING CURRENT TRANSMISSION SYSTEMS
As per JNTUK
Shunt
Compensators
–I
Lesson
4
Shunt
Compensators
–II
Lesson
5
Series
Compensators
Lesson
6
Combined
Controllers

7. Lesson
1
Introduction to
FACTS
Lesson
2
Objectives of
shunt and
Series
Compensation
Lesson
3
FLEXIBLE ALTERNATING CURRENT TRANSMISSION SYSTEMS
Shunt
Compensators
Lesson
4 Lesson
5
Series
Compensators
Combined
Controllers

8. 1 2
4
Introduction to
FACTS
3
Shunt
Compensator
Series
Compensators
Objectives of
shunt and
Series
Compensation

9. A
bo
ut
Power flow in an AC System
Loading capability limits
Dynamic stability considerations
Importance of controllable parameters
Basic types of FACTS controllers
Benefits from FACTS controllers
Requirements and characteristics of high Hist
ory
lesson
1
Lesson
2
Lesso
n
3

power devices
Voltage and current rating
Losses and speed of switching
Parameter trade–off devices.

10. AboutHistory
introduction
lesson1 Lesson 2Lesson 3
Objectives of shunt and Series Compensation
Objectives of shunt compensation
Mid–point voltage regulation for line segmentation
End of line voltage support to prevent voltage
instability
Improvement of transient stability
Power oscillation damping.
Concept of series capacitive compensation
Improvement of transient stability
Power oscillation damping
Functional requirements.

11. About
History
introduction
lesson1 Lesson 2 Lesson 3
Shunt Compensators
Thyristor Switched Capacitor(TSC)
Thyristor Switched /Controlled Reactor
Fixed Capacitor–Thyristor Controlled Reactor
(FC-TCR),
Thyristor Switched Reactor (TSC–TCR).
Static VAR compensator(SVC) and Static
Compensator(STATCOM):
The regulation and slope transfer function and
dynamic performance
Transient stability enhancement and power
oscillation damping
Operating point control and summary of
compensation control.

12. About
History
introduction
Lesson
4
Series Compensators (Qualitative Treatment)
Static series compensators:
Variable Impedance type Series Compensators
GTO thyristor controlled Series Capacitor
(GSC)
Thyristor Switched Series Capacitor (TSSC)
and Thyristor Controlled Series Capacitor
(TCSC).
Switching Converter type Series Compensation

13. About
History
introduction
Lesson
5
Combined Controllers
Voltage&PhaseangleRegulator
TCVRandTCPAR–SwitchedConverter
BasedVoltagePhaseAngleRegulator
Schematic and basic operating principles of
Unified Power Flow Controller (UPFC).
Interline Power Flow Controller (IPFC)
Application on transmission lines.

14. 14
Learning Objectives
CO1:Tolearnthebasicsofpowerflowcontrolintransmission
linesusingFACTScontrollers
CO2:DistinguishfunctionalRequirementsofshuntandseries
compensators.
CO3:TodescribesthemethodofshuntcompensationusingstaticVAR
compensators.
CO4:Tolearnthemethodsofcompensationusingseriescompensators
CO5:ToLearnthemethodsofcompensationusingcombined
compensators(UPFC&IPFC).

15. 15
Learning Outcomes
UnderstandpowerflowcontrolintransmissionlinesusingFACTS
controllers.
Analyzecompensationmethodstoimprovestabilityandreduce
poweroscillationsinthetransmissionlines.
ExplainthemethodofshuntcompensationusingstaticVAR
compensators.
Understandthemethodsofcompensationsusingseries
compensators.
ExplainoperationofCombinedController.

16. 16
Text Books:
1. “Understanding FACTS” N.G. Hingoraniand L.Guygi, IEEE
Press.IndianEdition is available:––Standard Publications, 2001.
Reference Books:
1.“Flexible ac transmission system (FACTS)” Edited by Yong Hue
Song and Allan T Johns, Institution of Electrical Engineers,
London.
2.Thyristor-based FACTS Controllers for Electrical Transmission
Systems, by R. MohanMathurand Rajiv k.Varma, Wiley
WEBLINKS:
1. https://www.siemens-energy.com/global/en/offerings/power-transmission/
2. https://www.gegridsolutions.com/facts.htm

17. 17

18. 18
Unit–I
Introduction to FACTS
1.1.PowerflowinanACSystem
1.2.Loadingcapabilitylimits
1.3.Dynamicstabilityconsiderations
1.4.Importanceofcontrollableparameters
1.5.BasictypesofFACTScontrollers
1.6.BenefitsfromFACTScontrollers
1.7.Requirementsandcharacteristicsofhighpowerdevices
1.7.1.Voltageandcurrentrating
1.7.2.Lossesandspeedofswitching
1.7.3.Parametertrade–offdevices.

19. 19
FlexibleACTransmissionSystems,calledFACTS,gotintherecent
yearsawellknowntermforhighercontrollabilityinpowersystemsby
meansofpowerelectronicdevices.
ThebasicapplicationsofFACTS-devicesare:
power flow control,
increase of transmission capability,
voltage control,
reactive power compensation,
stability improvement,
power quality improvement,
power conditioning,
flicker mitigation,
interconnection of renewable
and distributed generation and
storages.
Introduction to FACTS

20. 20
AnumberofFACTScontrollershavebeencommissioned.Mostofthem
performausefulroleduringbothsteady-stateandtransientoperation,
butsomearespecificallydesignedtooperateonlyundertransient
conditions.
FACTS controllers intended for steady-state operation are as follows
(IEEE/CIGRE´,1995):
Thyristor-controlledphaseshifter(PS):thiscontrollerisanelectronic
phase-shiftingtransformeradjustedbythyristorswitchestoprovidea
rapidlyvaryingphaseangle.
Loadtapchanger(LTC):thismaybeconsideredtobeaFACTS
controllerifthetapchangesarecontrolledbythyristorswitches.
Thyristor-controlledreactor(TCR):thisisashunt-connected,thyristor-
controlledreactor,theeffectivereactanceofwhichisvariedina
continuousmannerbypartialconductioncontrolofthethyristorvalve.
Thyristor-controlledseriescapacitor(TCSC):thiscontrollerconsistsof
aseriescapacitorparalleledbyathyristor-controlledreactorinorderto
providesmoothvariableseriescompensation.

21. 21
Interphasepowercontroller(IPC):thisisaseries-connectedcontroller
comprisingtwoparallelbranches,oneinductiveandonecapacitive,
subjectedtoseparatephase-shiftedvoltagemagnitudes.Activepower
controlissetbyindependentorcoordinatedadjustmentofthetwophase-
shiftingsourcesandthetwovariablereactances.Reactivepowercontrol
isindependentofactivepower.
Staticcompensator(STATCOM):thisisasolid-statesynchronous
condenserconnectedinshuntwiththeACsystem.Theoutputcurrentis
adjustedtocontroleitherthenodalvoltagemagnitudeorthereactive
powerinjectedatthebus.
Solid-stateseriescontroller(SSSC):thiscontrollerissimilartothe
STATCOMbutitisconnectedinserieswiththeACsystem.Theoutput
currentisadjustedtocontroleitherthenodalvoltagemagnitudeorthe
reactivepowerinjectedatoneoftheterminalsoftheseries-connected
transformer.

22. 22
Unifiedpowerflowcontroller(UPFC):thisconsistsofastatic
synchronousseriescompensator(sssc)andaSTATCOM,connectedin
suchawaythattheyshareacommonDCcapacitor.TheUPFC,bymeans
ofanangularlyunconstrained,seriesvoltageinjection,isabletocontrol,
concurrentlyorselectively,thetransmissionlineimpedance,thenodal
voltagemagnitude,andtheactiveandreactivepowerflowthroughit.It
mayalsoprovideindependentlycontrollableshuntreactive
compensation.
StaticVARcompensator(SVC):thisisashunt-connectedstaticsourceor
sinkofreactivepower.
High-voltagedirect-current(HVDC)link:thisisacontrollercomprising
arectifierstationandaninverterstation,joinedeitherback-to-backor
throughaDCcable.Theconverterscanuseeitherconventional
thyristorsorthenewgenerationofsemiconductordevicessuchasgate
turn-offthyristors(GTOs)orinsulatedgatebipolartransistors(IGBTs).

23. 11-06-2024 23
The Power Quality Evaluation Procedure

24. 11-06-2024 24
General classes of power quality and voltage
quality problems
Therearedifferentclassificationsforpowerqualityissues,eachusingaspecific
propertytocategorizetheproblem.
Someofthemclassifytheeventsas"steady-state"and"non-steady-state"
phenomena.Insomeregulations(e.g.,ANSIC84.1[22])themostimportant
factoristhedurationoftheevent.Otherguidelines(e.g.,IEEE-519)usethe
waveshape(durationandmagnitude)ofeacheventtoclassifypowerquality
problems.Otherstandards(e.g.,IEC)usethefrequencyrangeoftheeventfor
theclassification.
Forexample,IEC61000-2-5usesthefrequencyrangeanddividesthe
problemsintothreemaincategories:
lowfrequency(<9kHz),
highfrequency(>9kHz),
andelectrostaticdischargephenomena.In
addition,eachfrequencyrangeisdividedinto"radiated"and"conducted"
disturbances.

25. 11-06-2024 25

26. 11-06-2024 26

27. 11-06-2024 27

28. 28

29. 29

30. 30
Theworld'selectricpowersupplysystemsarewidelyinterconnected.
Thisisdoneforeconomicreasons,toreducethecostofelectricity
andtoimprovereliabilityofpowersupply.
Why We Need Transmission Interconnections?
Apartfromdelivery,thepurposeofthetransmissionnetwork
istopoolpowerplantsandloadcentersinordertominimizethetotal
powergenerationcapacityandfuelcost.
Transmissioninterconnectionsenabletakingadvantageof
diversityofloads,availabilityofsources,andfuelpriceinorderto
supplyelectricitytotheloadsatminimumcostwitharequired
reliability.
Ingeneral,ifapowerdeliverysystemwasmadeupofradial
linesfromindividual.Localgeneratorswithoutbeingpartofagrid
system,manymoregenerationresourceswouldbeneededtoservethe
loadwiththesamereliability,andthecostofelectricitywouldbe
muchhigher.

31. 31
Withthatperspective,transmissionisoftenan
alternativetoanewgenerationresource.Lesstransmission
capabilitymeansthatmoregenerationresourceswouldbe
requiredregardlessofwhetherthesystemismadeupoflargeor
smallpowerplants.
Infactsmalldistributedgenerationbecomesmore
economicallyviableifthereisabackboneofatransmission
grid.
Onecannotbereallysureaboutwhattheoptimum
balanceisbetweengenerationandtransmissionunlessthe
systemplannersuseadvancedmethodsofanalysiswhich
integratetransmissionplanningintoanintegratedvalue-based
transmission/generationplanningscenario.Thecostof
transmissionlinesandlosses,aswellasdifficultiesencountered
inbuildingnewtransmissionlines,wouldoftenlimitthe
availabletransmissioncapacity.

32. 32
Powertransfersgrow,thepowersystembecomesincreasingly
morecomplextooperateandthesystemcanbecomelesssecurefor
ridingthroughthemajoroutages.Itmayleadtolargepowerflowswith
inadequatecontrol,excessivereactivepowerinvariouspartsofthe
system,largedynamicswingsbetweendifferentpartsofthesystemand
bottlenecks,andthusthefullpotentialoftransmissioninterconnections
cannotbeutilized.
Thepowersystemsoftoday,byandlarge,aremechanically
controlled.Thereisawidespreaduseofmicroelectronics,computers
andhigh-speedcommunicationsforcontrolandprotectionofpresent
transmissionsystems;however,whenoperatingsignalsaresenttothe
powercircuits,wherethefinalpowercontrolactionistaken,the
switchingdevicesaremechanicalandthereislittlehigh-speedcontrol.
Anotherproblemwithmechanicaldevicesisthatcontrolcannotbe
initiatedfrequently,becausethesemechanicaldevicestendtowearout
veryquicklycomparedtostaticdevices.

33. 33
Ineffect,fromthepointofviewofbothdynamicandsteady-
stateoperation,thesystemisreallyuncontrolled.Powersystem
planners,operators,andengineershavelearnedtolivewiththis
limitationbyusingavarietyofingenioustechniquestomakethe
systemworkeffectively,butatapriceofprovidinggreateroperating
marginsandredundancies.Theserepresentanassetthatcanbe
effectivelyutilizedwithprudentuseofFACTStechnologyona
selective,asneededbasis.
Inrecentyears,greaterdemandshavebeenplacedonthe
transmissionnetwork,andthesedemandswillcontinuetoincrease
becauseoftheincreasingnumberofnonutilitygeneratorsand
heightenedcompetitionamongutilitiesthemselves.
TheFACTStechnologyisessentialtoalleviatesomebutnotallofthese
difficultiesbyenablingutilitiestogetthemostservicefromtheir
transmissionfacilitiesandenhancegridreliability.

34. 34

35. 35

36. 36
1.1. Power flow in an AC System
Transmissionfacilitiesconfrontoneormorelimiting
networkparametersplustheinabilitytodirectpowerflowatwill.
Inacpowersystems,giventheinsignificantelectricalstorage,
theelectricalgenerationandloadmustbalanceatalltimes.Tosome
extent,theelectricalsystemisself-regulating.
Ifgenerationislessthanload,thevoltageandfrequencydrop,
andtherebytheload,goesdowntoequalthegenerationminusthe
transmissionlosses.However,thereisonlyafewpercentmarginfor
suchaself-regulation.Ifvoltageisproppedupwithreactivepower
support,thentheloadwillgoup,andconsequentlyfrequencywill
keepdropping,andthesystemwillcollapse.Alternately,ifthereis
inadequatereactivepower,thesystemcanhavevoltagecollapse.

37. 37
Whenadequategenerationisavailable,activepowerflowsfromthe
surplusgenerationareastothedeficitareas,anditflowsthroughall
parallelpathsavailablewhichfrequentlyinvolvesextrahigh-voltage
andmedium-voltagelines.Often,longdistancesareinvolvedwith
loadsandgeneratorsalongtheway.Alongloop,becauseofthe
presenceofalargenumberofpowerfullowimpedancelinesalong
thatloop.Thereareinfactsomemajorandalargenumberofminor
loopflowsandunevenpowerflowsinanypowertransmission
system.

38. 38
1.1.1.Power Flow In Parallel Paths
Consideraverysimplecaseofpowerflow[Figure],throughtwoparallel
paths(possiblycorridorsofseverallines)fromasurplusgenerationarea,
shownasanequivalentgeneratorontheleft,toadeficitgenerationareaon
theright.Withoutanycontrol,powerflowisbasedontheinverseofthe
varioustransmissionlineimpedances.
Thelowerimpedancelinemaybecomeoverloadedandtherebylimitthe
loadingonbothpathseventhoughthehigherimpedancepathisnotfully
loaded.Therewouldnotbeanincentivetoupgrade.currentcapacityofthe
overloadedpath,becausethiswouldfurtherdecreasetheimpedanceandthe
investmentwouldbeself-defeatingparticularlyifthehigherimpedancepath
alreadyhasenoughcapacity.

39. 39
WithHVDC,powerflowsasorderedbytheoperator,becausewith
HVDC powerelectronicsconverterspoweriselectronically
controlled.Also,becausepoweriselectronicallycontrolled,theHVDC
linecanbeusedtoitsfullthermalcapacityifadequateconvertercapacity
isprovided.Furthermore,anHVDCline,becauseofitshigh-speed
control,canalsohelptheparallelactransmissionlinetomaintain
stability.However,HVDCisexpensiveforgeneraluse,andisusually
consideredwhenlongdistancesareinvolved,suchasthePacificDC
Intertieonwhichpowerflowsasorderedbytheoperator.
Figure showsthesametwopaths,butoneofthese hasHVDC
transmission.

40. 40
AsalternativeFACTSControllers,Figurescanddshowoneofthe
transmissionlineswithdifferenttypesofseriestypeFACTS
Controllers.Bymeansofcontrollingimpedance[Figurec]orphase
angle[Figured],orseriesinjectionofappropriatevoltage(not
shown)aFACTSControllercancontrolthepowerflowasrequired.
Maximumpowerflowcaninfactbelimitedtoitsratedlimitunder
contingencyconditionswhenthislineisexpectedtocarrymorepower
duetothelossofaparallelline.

41. 41
1.1.2.Power Flow In a Meshed System
Tounderstandthefreeflowofpower,consideraverysimplifiedcaseinwhich
generatorsattwodifferentsitesaresendingpowertoaloadcenterthrougha
networkconsistingofthreelinesinameshedconnection(Figure).
SupposethelinesAB,BC,andAChavecontinuousratingsof1000MW,
1250MW,and2000MW,respectively,andhaveemergencyratingsoftwice
thosenumbersforasufficientlengthoftimetoallowreschedulingofpowerin
caseoflossofoneoftheselines.
oneofthegeneratorsisgenerating2000MW
andtheother1000MW,atotalof3000MW
wouldbedeliveredtotheloadcenter.Forthe
impedancesshown,thethreelineswould
carry600,1600,and1400MW,respectively,
asshowninFigure
overloadlineBC(loadedat1600MWforitscontinuousratingof1250MW),
andthereforegenerationwouldhavetobedecreasedatB,andincreasedatA,
inordertomeettheloadwithoutoverloadinglineBC.
Power,inshort,flowsinaccordancewithtransmissionlineseriesimpedances
(whichare90%inductive)thatbearnodirectrelationshiptotransmission
ownership,contracts,thermallimits,ortransmissionlosses.

42. 42
Solution1:If,acapacitorwhosereactanceis-5Ωatthesynchronous
frequencyisinsertedinoneline[Figure],itreducestheline'simpedance
from10Ωto5Ω,sothatpowerflowthroughthelinesAB,BC,andAC
willbe250,1250,and1750MW,respectively.
Observation:Itisclearthatiftheseriescapacitorisadjustable,then
otherpower-flowlevelsmayberealizedinaccordancewiththe
ownership,contract,thermallimitations,transmissionlosses,anda
widerangeofloadandgenerationschedules.
Drawback:Althoughthiscapacitorcouldbe
modularandmechanicallyswitched,thenumber
ofoperationswouldbeseverelylimitedbywearon
themechanicalcomponentsbecausethelineloads
varycontinuouslywithloadconditions,generation
schedules,andlineoutages.
Othercomplications,iftheseriescapacitorismechanically
controlledis
mayleadtosub-synchronousresonance(typicallyat10-40Hzfora50Hzsystem).
Thisresonanceoccurswhenoneofthemechanicalresonancefrequenciesofthe
shaftofamultiple-turbinegeneratorunitcoincideswith50Hzminustheelectrical
resonancefrequencyofthecapacitorwiththeinductiveimpedanceoftheline.
suchresonancepersists,itwillsoondamagetheshaft.

43. 43
outageofonelineforcesotherlinestooperateattheiremergencyratingsand
carryhigherloads,powerflowoscillationsatlowfrequency(typically0.3-3Hz)
maycausegeneratorstolosesynchronism,perhapspromptingthesystem's
collapse.
Ifallorapart ofthe series capacitor isthyristor-controlled,
itcanbevariedasoftenasrequired.
canbemodulatedtorapidlydampanysub-synchronousresonance
conditions,aswellasdamplowfrequencyoscillationsinthepower
flow.
allowthetransmissionsystemtogofromonesteady-stateconditionto
anotherwithouttheriskofdamagetoageneratorshaftandalsohelp
reducetheriskofsystemcollapse.
athyristor-controlledseriescapacitorcangreatlyenhancethestabilityof
thenetwork.
Conclusion :
series compensation to be mechanically controlled and part
thyristor controlled, soasto counter the system constraints atthe
least cost.

44. 44
Similarresultsmaybeobtainedby
increasingtheimpedanceofoneofthe
linesinthesamemeshedconfigurationby
insertinga7Ωreactor(inductor)inseries
withlineAB[Figure].
Again,aseriesinductorthatispartly
mechanicallyandpartlythyristor-controlled,
itcouldservetoadjustthesteady-state
powerflowsaswellasdampunwanted
oscillations.
Asanotheroption,athyristor-controlled
phase-angleregulatorcouldbeinstalled
insteadofaseriescapacitororaseries
reactorinanyofthethreelinestoservethe
samepurpose.
InFigure,theregulatorisinstalledinthe
thirdlinetoreducethetotalphase-angle
differencealongthelinefrom8.5degrees
to4.26degrees.Asbefore,acombinationof
mechanicalandthyristorcontrolofthephase-
angleregulatormayminimizecost.

45. 45
Thesameresultscouldalsobeachievedbyinjectingavariable
voltageinoneofthelines.
Balancingofpowerflowintheabovecasedidnotrequiremore
thanoneFACTSController,andindeedthereareoptionsof
differentcontrollersandindifferentlines.
Ifthereisonlyoneownerofthetransmissiongrid,thenadecision
canbemadeonconsiderationofoveralleconomicsalone.
Ontheotherhand,ifmultipleownersareinvolved,thenadecision
mechanismisnecessaryontheinvestmentandownership.

46. 46
1.2. WHAT LIMITS THE LOADING
CAPABILITY?
The objective is to make transmission assets is to maximize loading
capability. The limitations on loading capability as follows
1.Thermal limit
2.Voltage limit
3.Dielectric limit
4.Stability limit

47. 47
Thermalcapabilityofanoverheadlineisafunctionoftheambient
temperature,windconditions,conditionoftheconductor,andground
clearance.
Itvariesperhapsbyafactorof2to1duetothevariableenvironmentand
theloadinghistory.
Thenominalratingofalineisgenerallydecidedfortheworstambient
environment.Someutilitiesassignwinterandsummerratings.
Therearealsooff-line/on-linecomputerprogramsthatcancalculatea
line'sloadingcapabilitybasedonavailableambientenvironment,recent
loadinghistoryandoverperiodoftime,ageofautomation.(sometimes
ambientconditionsmayworsethanassumed)
Duringplanning/designstages,normalloadingofthelinesisfrequently
decidedonalossevaluationbasisunderassumptionswhichmayhave
changedforavarietyofreasons.
1.Thermal limit

48. 48
Increasingloadingonlinesimpactsonratingoftransformersandother
protectionequipment.
Realtimeloadingcapabilityoftransformersisalsoafunctionofambient
temperature,agingofthetransformerandrecentloadinghistory.
Off-lineandon-linemonitorscanalsobeusedtoobtainrealtime
loadingcapabilityoftransformers,alsolendsitselftoenhancedcooling.
Increasingloadingcapabilityisthepossibilityofupgradingalineby
changingtheconductortothatofahighercurrentrating,whichmayin
turnrequirestructuralupgrading.Finally,thereisthepossibilityof
convertingasingle-circuittoadouble-circuitline.Thequestionis
Willtheextrapoweractuallyflowandbecontrollable? Willthe
voltageconditions be acceptable with sudden load dropping, etc.?
The FACTS technology can help in making aneffective use
ofthisnewfound capacity.

49. 49
Voltage & Dielectric limit
•Foragivennominalvoltagerating,itisoftenpossibletoincrease
normaloperationby+10Vvoltage(i.e.,500kV-550kV)oreven
higher.
Careisthenneededtoensurethatdynamicandtransientover
voltagesarewithinlimits.
Fromaninsulationpointofview,manylinesaredesignedvery
conservatively.
Moderngaplessarrestersorlineinsulatorswithinternalgapless
arresters,orpowerfulthyristor-controlledovervoltagesuppressorsat
thesubstationscanenablesignificantincreaseinthelineand
substationvoltagecapability.
TheFACTStechnologycouldbeusedtoensureacceptableover-
voltageandpowerflowconditions.

50. 50
Thestabilityissuesthatlimitthetransmissioncapabilityare:
Transient stability
Dynamic stability
Steady-state stability
Frequency collapse
Voltage collapse
Subsynchronousresonance
Stability limit

51. 51
Theinterconnectedpowersystemshallremainstableuponlossof
anyonesingleelementwithoutsystemcascadingthatcouldresultin
thesuccessivelossofadditionalelements.
TheFACTStechnologycancertainlybeusedtoovercomeanyof
thestabilitylimits,inwhichcasetheultimatelimitswouldbe
thermalanddielectric.

52. 52
ThepowertransfercapabilityofTr.Lineismostaffectedby_______
Ans:Inducatnce

53. 53
1.3. POWER FLOW AND DYNAMIC STABILITY
CONSIDERATIONS
OF A TRANSMISSION INTERCONNECTION
Fig: Ac power flow control of a transmission line:
(a) simple two-machine system (b) current flow perpendicular to the driving voltage
Locations 1 and 2 could be any transmission substations connected
by a transmission line. Substations may have loads, generation, or
may be interconnecting points on the system and for simplicity
they are assumed to be stiff busses.
E1andE2arethemagnitudesofthebusvoltageswithanangleδbetween
thetwo.ThelineisassumedtohaveinductiveimpedanceX,andtheline
resistanceandcapacitanceareignored.

54. 54
??????=
????????????
??????
and lags E
L by 90
0
.
E
Lis the driving voltage drop in the line.
•Foratypicalline,angleδandcorrespondingdrivingvoltage,or
voltagedropalongtheline,issmallcomparedtothelinevoltages.
Giventhatatransmissionlinemayhaveavoltagedropatfull
loadofperhaps1%/10km,andassumingthatalinebetween
twostiffbusbars(substations)is200kmlong,thevoltagedrop
alongthislinewouldbe20%atfullload,andtheangleδwouldbe
small.
•Forexample,thatwithequalmagnitudesofE1andE2,andXof
0.2perunitmagnitude,theangleδwouldbeonly0.2radiansor
11.5degrees.
•ThecurrentflowonthelinecanbecontrolledbycontrollingE
LorX
orδ.
•In order to achieve a high degree of control on the currentin this
line, the equipment required in series with the line would not have
a very high power rating.

55. 55
Forexample,a500kV(approximately300kVphase-ground),
2000Alinehasathree-phasethroughputpowerof1800MVA,
and,fora200kmlength,itwouldhaveavoltagedropofabout60
kV.Forvariableseriescompensationofsay,25%,theseries
equipmentrequiredwouldhaveanominalratingof0.25x60
kVx2000A=30MVAperphase,or90MVAforthree
phases,whichisonly5%ofthethroughputlineratingof1800
MVA.Voltageacrosstheseriesequipmentwouldonlybe15
kVatfullload,althoughitwouldrequirehigh-voltageinsulation
toground(thelatterisnotasignificantcostfactor).However,
anyseries-connectedequipmenthastobedesignedtocarry
contingencyoverloadssothattheequipmentmayhavetobe
ratedto100%overloadcapability.
TheratingofseriesFACTSControllerswouldbeafractionof
thethroughputratingofaline.

56. 56
Thecurrentflowphasorisperpendiculartothedrivingvoltage
(90°phaselag).Iftheanglebetweenthetwobusvoltagesis
small,thecurrentflowlargelyrepresentstheactivepower.
Increasingordecreasingtheinductiveimpedanceofalinewill
greatlyaffecttheactivepowerflow.
Thusimpedancecontrol,whichinrealityprovidescurrent
control,canbethemostcost-effectivemeansofcontrollingthe
powerflow.
controlloops,canbeusedforpowerflowcontroland/orangle
controlforstability.
Figure shows, a phasor diagram ofthe relationship between the
active and reactive currents with reference to the voltages at the
two ends.

57. 57

58. 58
Active component of the current flow at E1 is:
I
p1= (E
2sin δ)/X
Reactive component of the current flow at ,E1 is:
I
q1= (E
1-E
2cos δ)/X
Thus, active power at the E1 end:
P
1 = E
1(E
2sin δ)/X
Reactive power at the E
1end:
Q
1= E
1(E
1-E
2cos δ)/X
Similarly, active component of the current flow at E
2is:
Ip2= (E
1sin δ)/X
Reactive component of the current flow at E2 rs:
I
q2= (E
2-E
1cosδ)/X
Thus, active power at the E2 end:
P
2=E
2(E
1sin δ)/X
Reactive power at the E2 end:
Q
2= E
1(E
2-E
1cosδ)/X
Naturally P1 and P2 a;rethe same:
P = E
1(E
2sin δ)/X

59. 59
Byvaryingthevalueof‘X’P,Q
1andQ
2willvary.
Whenδincreasesfrom0
0
to90
0
activepowerincreases.Further
increaseofδfrom90
0
to180
0
powerthenfalls.
ThereforewithoutthehighspeedcontrolofanyoneofparametersE
1,
E
2,E
1-E
2,Xandδ,thetransmissionlinecanbeutilizedonlytoalevel
wellbelowthatcorrespondingto90
0
.
Thisisnecessary,inordertomaintainanadequatemarginneededfor
transientanddynamicstability.
Foragivenpowerflow,varyingofXwillcorrespondinglyvarythe
anglebetweenthetwoends.
Power/currentflowcanalsobecontrolledbyregulatingthemagnitude
ofvoltagephasor.ElorvoltagephasorE2
WithchangeinthemagnitudeofE
1,themagnitudeofthedriving
voltagephasorE
1–E
2doesnotchangebymuch,butitsphaseangle
does.ThismeansregulationofE
1,orE
2hasmuchmoreinfluence
overthereactivepowerflow.

60. 60
FIG:(e)regulatingvoltagemagnitudemostlychangesreactivepower(f)injecting
voltageperpendiculartothelinecurrentmostlychangesactivepower(g)injecting
voltagephasorinserieswiththeline.
Figure(f)thatwhentheinjectedvoltageisinphasequadraturewiththecurrent
(whichisapproximatelyinphasewiththedrivingvoltage)itdirectlyinfluencesthe
magnitudeofthecurrentflow,andwithsmallangleinfluencessubstantiallytheactive
powerflow.
Thevoltageinjectedinseriescanbeaphasorwithvariablemagnitudeandphase
relationshipwiththelinevoltage[Figure(g)].Itisseenthatvaryingtheamplitude
andphaseangleofthevoltageinjectedinseries,boththeactiveandreactivecurrent
flowcanbeinfluenced.

61. 61
1.4. RELATIVE IMPORTANCE OF
CONTROLLABLE PARAMETERS
ControlofthelineimpedanceXcanprovideapowerfulmeansof
currentcontrol.
Whentheangleisnotlarge,controlofXortheanglesubstantially
providesthecontrolofactivepower.
Controlofanglewhichinturncontrolsthedrivingvoltage,providesa
powerfulmeansofcontrollingthecurrentflowandhenceactive
powerflowwhentheangleisnotlarge.
Injectingavoltageinserieswiththeline,andperpendiculartothe
currentflow,canincreaseordecreasethemagnitudeofcurrentflow
andhencetheactivepowerwhentheangleisnotlarge.

62. 62
Injectingvoltageinserieswiththelineandwithanyphaseanglewith
respecttothedrivingvoltagecancontrolthemagnitudeandthephase
ofthelinecurrent.Thismeansthatinjectingavoltagephasorwith
variablephaseanglecanprovideapowerfulmeansofprecisely
controllingtheactiveandreactivepowerflow.Thisrequiresinjection
ofbothactiveandreactivepowerinseries.
Becausetheperunitlineimpedanceisusuallyasmallfractionofthe
linevoltage,theMVAratingofaseriesControllerwilloftenbea
smallfractionofthethroughputlineMVA.
Whentheangleisnotlarge,controllingthemagnitudeofoneorthe
otherLinevoltages(e.g.,withathyristor-controlledvoltageregulator)
canbeaverycost-effectivemeansforthecontrolofreactivepower
flowthroughtheinterconnection.
CombinationofthelineimpedancecontrolwithaseriesController
andvoltageregulationwithashuntControllercanalsoprovideacost-
effectivemeanstocontrolboththeactiveandreactivepowerflow
betweenthetwosystems.

63. 63
1.5. BASIC TYPES OF FACTS
CONTROLLERS
Shunt
connected
controllers
Series
connected
controllers
Combined
series-series
controllers
Combined
shunt-series
controllers
The FACTS controllers can be classified as
Depending on the power electronic devices used in the control, the
FACTS controllers can be classified as
(A) Variable impedance type
(B) Voltage Source Converter (VSC)
based.

64. 64
The variable impedance type controllers include:
(i) Static VarCompensator (SVC), (shunt
connected)
(ii) Thyristor Controlled Series Capacitor or
compensator (TCSC), (series connected)
(iii) Thyristor Controlled Phase Shifting
Transformer (TCPST) of Static PST (combined
shunt and series)

65. 65
The VSC based FACTS controllers are:
Static synchronous Compensator (STATCOM)
(shunt connected)
Static Synchronous Series Compensator (SSSC)
(series connected)
Interline Power Flow Controller (IPFC)
(combined series-series)
Unified Power Flow Controller (UPFC)
(combined shunt-series)

66. 66
SomeofthespecialpurposeFACTScontrollersare
(a) Thyristor Controller Braking Resistor (TCBR)
(b) Thyristor Controlled Voltage Limiter (TCVL)
(c) Thyristor Controlled Voltage Regulator (TCVR)
(d) Interphase Power Controller (IPC)
(e) NGH-SSR damping

67. 67
SeriesControllers:[Figure(b)]TheseriesControllercouldbeavariable
impedance,suchascapacitor,reactor,etc.,orapowerelectronicsbased
variablesourceofmainfrequency,subsynchronousandharmonic
frequencies(oracombination)toservethedesiredneed.Inprinciple,all
seriesControllersinjectvoltageinserieswiththeline.Evenavariable
impedancemultipliedbythecurrentflowthroughit,representsan
injectedseriesvoltageintheline.Aslongasthevoltageisinphase
quadraturewiththelinecurrent,theseriesControlleronlysuppliesor
consumesvariablereactivepower.Anyotherphaserelationshipwill
involvehandlingofrealpoweraswell.

68. 68
ShuntControllers:[Figure(c)]AsinthecaseofseriesControllers,the
shuntControllersmaybevariableimpedance,variablesource,ora
combinationofthese.Inprinciple,allshuntControllersinjectcurrent
intothesystematthepointofconnection.Evenavariableshunt
impedanceconnectedtothelinevoltagecausesavariablecurrentflow
andhencerepresentsinjectionofcurrentintotheline.Aslongasthe
injectedcurrentisinphasequadraturewiththelinevoltage,theshunt
Controlleronlysuppliesorconsumesvariablereactivepower.Anyother
phaserelationshipwillinvolvehandlingofrealpoweraswell.

69. 69
Combinedseries-seriesControllers:[Figure(d)]Thiscouldbea
combinationofseparateseriescontrollers,whicharecontrolledina
coordinatedmanner,inamultilinetransmissionsystem.Oritcouldbea
unifiedController,Figure(d),inwhichseriesControllersprovide
independentseriesreactivecompensationforeachlinebutalsotransfer
realpoweramongthelinesviathepowerlink.Therealpowertransfer
capabilityoftheunifiedseries-seriesController,referredtoasInterline
PowerFlowController,makesitpossibletobalanceboththerealand
reactivepowerflowinthelinesandtherebymaximizetheutilizationof
thetransmissionsystem.Notethattheterm"unified"heremeansthat
thedcterminalsofallControllerconvertersareallconnectedtogether
forrealpowertransfer.

70. 70
Combinedseries-shuntControllers:[Figures(e)and(f)]Thiscouldbe
acombinationofseparateshuntandseriesControllers,whichare
controlledinacoordinatedmanner[Figure(e)],oraUnifiedPowerFIow
Contollerwithseriesandshuntelements[Figure(f)].Inprinciple,
combinedshuntandseriesControllersinjectcurrentintothesystemwith
theshuntpartoftheControllerandvoltageinseriesinthelinewiththe
seriespartoftheController.However,whentheshuntandseries
Controllersareunified,therecanbearealpowerexchangebetweenthe
seriesandshuntControllersviathepowerlink.

71. 71

72. 72
1.6. CHECKLIST OF POSSIBLE BENEFITS
FROM FACTS TECHNOLOGY
1.Controlofpowerflowasorderedmeansmeettheutilitiesownneeds,ensure
optimumpowerflow,ridethroughemergencyconditions,oracombination.
2.Increasetheloadingcapabilityoflinestotheirthermalcapabilities,
includingshorttermandseasonal.
3.Increasethesystemsecuritythroughraisingthetransientstabilitylimit,
limitingshort-circuitcurrentsandoverloads,managingcascadingblackouts
anddampingelectromechanicaloscillationsofpowersystemsandmachines.
4.Providesecuretielineconnectionstoneighboringutilitiesandregionsthereby
decreasingoverallgenerationreserverequirementsonbothsides.
5.Providegreaterflexibilityinsitingnewgeneration.Upgradeoflines.
6.Reducereactivepowerflows,thusallowingthelinestocarrymoreactive
power.Reduceloopflows.
7.Increaseutilizationoflowestcostgeneration.Oneoftheprincipalreasons
fortransmissioninterconnectionsistoutilizelowestcostgeneration.
Whenthiscannotbedone,itfollowsthatthereisnotenoughcost-effective
transmissioncapacity.Cost-effectiveenhancementofcapacitywilltherefore
allowincreaseduseoflowestcostgeneration.

73. 73
1.7.1. Voltage and Current Rating
Devicecellsforhighpowerareusuallysinglecrystalsiliconwafers,75-125
mmindiameter,andpushingtoward150mmindiameter.
siliconcrystalhasaveryhighvoltagebreakdownstrengthof20kV/cmanda
resistivitysomewhereinbetweenmetalsandinsulators.
Dopingwithimpuritiescanalteritsconductioncharacteristics.
Lowerdopingmeanshighervoltagecapability,butalsohigherforward
voltagedropandlowercurrentcapability.Tosomeextentthecurrentand
voltagecapabilitiesareinterchangeable.
Alargerdiameternaturallymeanshighercurrentcapability.
A125mmdevicemayhaveacurrent-carryingcapabilityof3000-4000
amperesandavoltage-withstandcapabilityintherangeof6000-10,000
volts.
1.7. HIGH-POWER DEVICE
CHARACTERISTICS AND REQUIREMENTS

74. 74
The useable device voltage will be about half the blocking voltage capability.
Devicesareconnectedinseriesforhigh-voltagevalves.
Ensuringequalsharingofvoltageduringturn-on,turn-off,anddynamic
voltagechangesbecomesamajorexerciseforavalvedesignerinconsidering
trade-offamongvariousmeanstodosoanddecidingonthebestmix.
Theshort-circuitcurrentdutydeterminestherequiredcurrentcapacity.
Thedeviceselectionmustthereforeconsiderallpossiblefaultandprotection
scenariostodecideonthecurrentandalsovoltagemarginsandredundancy.
Thethyristorfamilyofdevicescancarryalargeoverloadcurrentforshort
periodsandaverylargesingle-cyclefaultcurrentwithoutfailures.The
thyristoranddiodefamilyofdevicesfailinashortcircuitwithlow-voltage
drop,sothecircuitmaycontinuetooperateiftheremainingdevicesinthe
circuitcanperformtheneededfunction.
Asdictatedbythemarketneedsofconverters,mostofthedevicesmadewith
turn-offcapability,aremadewithnoreverseblockingcapability.Theyare
thereforereferredtoasasymmetricturn-offdevices,oftenjustturn-off
devices.Asitturnsoutthevoltage-sourcedconvertersalsorequireareverse
diodeinparallelwitheachmaindevice.

75. 75
1.7.2. Losses and Speed of Switching
•Forward-voltagedropandconsequentlossesduringfullconducting
state(onstatelosses).Losseshavetoberapidlyremovedfromthe
waferthroughthepackageandultimatelytothecoolingmediumand
removingthatheatrepresentsahighcost.
•Speedofswitching.Transitionfromafullyconductingtoafullynon
conductingstate(turn-off)withcorrespondinghighdv/dtjustafterturn-
off,andfromafullynonconductingtoafullyconductingstate(turn-on)
withcorrespondinghighdi/dtduringtheturn-offareveryimportant
parameters.Theydictatethesize,cost,andlossesofsnubbercircuits
neededtosoftenhighdv/dtanddi/dt,easeofseriesconnectionof
devices,andtheuseabledevicecurrentandvoltagerating.

76. 76
Switching losses. During the turn-on, the forward current rises; before
the forward voltage falls and during turn-off of the turn-off devices, the
forward voltage rises before the current falls. Simultaneous existence of
high voltage and currentinthe device represents power losses. Being
repetitive,theyrepresentasignificantpartofthelosses,andoftenexceed
theon-stateconductionlosses.
Ina power semiconductor design, thereisa trade-off between switching
losses and forward voltage drop (on-state losses), which also means that
the optimizationofdevice designisa functionofthe application circuit
topology. Even though normal system frequencyis50 or60Hz,
atype of converters called "pulse-widthmodulation(PWM)"
converters have high internal frequency of
hundredsofHz,toevenafewkilo-Hzforhigh-powerapplications.With
many times more switching events, the switching lossescanbecome a
dominantpartofthetotallossesinPWMconverters.

77. 77
•Thegate-driverpowerandtheenergyrequirementareaveryimportant
partofthelossesandtotalequipmentcost.Withlargeandlongcurrent
pulserequirements,forturn-onandturn-off,notonlycantheselossesbe
Importantinrelationtothetotallosses,thecostofthedrivercircuitand
powersupplycanbehigherthanthedeviceitself.Thesizeofall
componentsthataccompanyapowerdeviceincreasesthestray
inductanceandcapacitance,whichinturnimpactsthestressesonthe
devices,switchingtimeandsnubberlosses.Giventhehighimportance
ofcoordinationofthedeviceandthedriverdesignandpackaging,the
futuretrendistopurchasethedeviceandthedriverasasinglepackage
fromthedevicesupplier.

78. 78
1.7.3. Parameter Trade-Off of Devices
Thecostofdevicesisrelatedtoproductionyieldofgooddevices,whicharethen
gradedintovariousratings.Thisthereforecallsforgoodqualitycontrolalltheway
fromthestartingmaterialtothefinishedproductandincludingthequalityofthe
electricpowersupplyintheproductionplant.Allpowerdevicesforhigh-power
Controllersareindividuallytested,asisthepracticewithHVDCconverters,andtheir
recordkeptforfuturereplacementservice.
Apartfromthetrade-offbetweenvoltageandcurrentcapability,othertradeoff
parametersinclude:
powerrequirementsforthegate
di/dtcapability
dv/dtcapability
turn-ontimeandturn-offtime
turn-onandturn-offcapability
uniformityofcharacteristics
qualityofstartingsiliconwafers
classofcleanenvironmentformanufacturingofdevices,etc.

79. 79
Advanceddesignandprocessingmethodshavebeendevelopedand
continuetobedeveloped.
Manufacturersdividemarketintovariousdevicetypesbasedon
applicationandmarketsize.
Devicesarealsotailoredforindividuallargecustomersandproject
orders.
Switchingspeed,switchinglosses,size,andcostofsnubbercircuitsare
attributedtopowersemiconductordevices.
Devicesaresoldseparatelyfromgate-drivecircuitsandsnubbercircuits.
Thedeviceperformanceisinfluencedbythegatedriver,snubber,and
circuit-busdesignforconnectingdevice-modulesintoaconverter,in
orderofpriority.
Thecostofapplicationcanbesignificantlyreducedbyassemblingand
sellingdevices,gatedrivers,snubbers,andbus-workclosetothem.The
electrical-mechanicalintegrationofthewaferandgate-drivecircuit
providesbenefitsthroughouttheapplication.
ThePowerElectronicsBuildingBlock(PEBB)programfocusesonintegration,
reducingconversioncosts,losses,weight,andsize.Itoffersdevices,gatedrivers,
packaging,andbus-workundervarioustradenames,recognizingpotential
benefits.

80. 80
1.Thepurposeofthetransmissionnetworkistopoolpowerplantsandloadcentersin
ordertominimizethe_____and______.
A.totalpowergenerationcapacity,fuelcost
B.totaldistributioncapacity,unitcost
C.totaltransmissioncapacity,runningcost
D.totalpowergenerationcapacity,maintenancecost
2. By providing added flexibility, FACTS Controllers can enable a line to carry power
closer to its ________.
A.DielectricratingB.StabilityC.ThermalRatingD.RatedVoltage
3.Inacpowersystems,giventheinsignificantelectricalstorage,the____and___must
balanceatalltimes.
A.electricaltransmissionanddistributionB.electricalgeneration,load
C.electricaltransmissionandload D.Noneoftheabove
4.Powerflowisbasedontheinverseofthevarioustransmissionline________.
A.Impedance B.CapacitanceC.Voltage D.Current
5.AnHVDCline,becauseofitshigh-speedcontrol,canalsohelptheparallelac
transmissionlinetomaintain_____.
A.Voltage B.RatedpowerC.ThermalRatingD.Stability

81. 81
6.Bymeansofcontrolling_______aFACTSControllercancontrolthepowerflowas
required.
A.impedance B.phaseangle
C.seriesinjectionofappropriatevoltage D.Alltheabove
7.Aseriescapacitorinalinemayleadto_________.
A.Sub-synchronousresonanceB.MechanicalOscillationsC.DampingD.All
theabove
8.________limitstheloadingcapabilityofTransmissionlines
A.ThermalB.Dielectric C.StabilityD.Alltheabove
9.Thermalcapabilityofanoverheadlineisafunctionofthe________.
A.ambienttemperature,windconditions B.loadingCapability
C.conditionoftheconductor,andgroundclearanceD.A&C
10._______canbetakenintoaccountonthereal-timevaluebasisofextraloading
capability.
LossesB.RatedpowerC.Voltage D.Current

82. 82
11.Dielectricfroman____pointofview,manylinesaredesignedveryconservatively.
A.ConductionB.ElectricalpotentialC.Insulation D.Resistance
12. The current flow on the line can be controlled by controlling ______
A.E
L B.X C.δ D.Alltheabove
13.A500kV(approximately300kVphase-ground),2000Alinehasathree-phase
throughputpowerof1800MVA,and,fora200kmlength,itwouldhaveavoltagedrop
ofabout60kV.Forvariableseriescompensationofsay,25%,theseriesequipment
requiredwouldhaveanominalratingof_______MVAperphase,whichisonly
_____%ofthethroughputlineratingof1800MVA.
A.35, 5.5 B. 30, 5 C. 30, 4 D. 35, 5
14. Increasing or decreasing the inductive impedance of a line will greatly affect the
_____flow.
A. active powerB. reactive powerC . A &B D. None of the Above
15. Control of the line impedance X (e.g., with a thyristor-controlled series capacitor)
can provide a powerful means of ____ control.
A. VoltageB Current C. Power D. None of the Above

83. 83
16.Aninjectinga_______phasorwithvariablephaseanglecanprovideapowerful
meansofpreciselycontrollingtheactiveandreactivepowerflow.
A.VoltageBCurrent C.Power D.NoneoftheAbove
17.Inprinciple,allseriesControllersinject_______inserieswiththeline.
A.VoltageBCurrent C.Power D.NoneoftheAbove
18.Inprinciple,allshuntControllersinjectcurrentintothesystematthe________.
A.TransmissionsideB.Pointofconnection
C.DistributionsideD.Neartotheload
19. Silicon crystal has a very high voltage breakdown strength of ______ kV/cm
A.198 B.240 C.155 D.200
20.Transitionfromafullyconductingtoafullynon-conductingstate(turn-off)with
corresponding_____justafterturn-off,andfromafullynon-conductingtoafully
conductingstate(turn-on)withcorresponding______duringtheturn-offarevery
importantparameters.
A.lowdv/dt,lowdi/dt B.highdv/dt,lowdi/dt
C.highdv/dt,highdi/dt D.lowdv/dt,highdi/dt

84. 84
ANSWERS
1.(A)totalpowergenerationcapacity,fuelcost
2.(C)thermalrating
3.(B)electricalgeneration,load
4.(A) impedance
5.(D)stability
6.(D)impedanceorphaseangleorseriesinjectionofappropriatevoltage
7.(A)sub-synchronousresonance
8.(D)Alltheabove
9.(D)ambienttemperature,windconditions,conditionoftheconductor,andgroundclearance
10.(A)losses
11.(C)insulationpoint
12.D
13.(B)0.25X60kVX2000A=30,5
14.A.activepower
15.BCurrent
16.AVoltage
17.AVoltage
18.Bpointofconnection
19.D.200kV/cm
20.Chighdvldt,highdildt

85. 85
1.Threebussystems,ithastwogeneratorwithrealpowergenerationof4p.uatbus1,
2p.uatbus2andloadof6p.uatbus3.Supposethelines1-2,2-3,and1-3have
continuousratingsof2p.u,2.5p.uand4p.u.Theimpedanceratingofline1-2is10
ohm,line2-3is5ohmand1-3is10ohm.Assumebasepoweris1000MVAand
impedancebaseis10000.Identifytheoverloadedline.?
a..Findtheminimumvalueofadditionalseriescapacitiveimpedancerequiredfor
thecompensationofoverloadedline….ohm
b.Findtheminimumvalueofadditionalseriesinductiveimpedancerequiredfor
thecompensationofoverloadedline….ohm
c.Letassumepowerangleofbus1is0degree,bus2is-0.0343degreeandbus3is
-0.080degreeinabovequestion(Q1)AThyristorcontrolledphase-angleregulator
couldbeinstalledinsteadofaseriescapacitor.Thenwhatisthephaseangletobe
providedbytheregulatorforthecompensationoftheoverloadedline?
Exercise Problem

86. 86
a.

87. 87
b.
c.

88. 88
Important Questions
1.a).Whatisthenecessityofinterconnectioninelectricalpowersystems?
Explain
problemswithinterconnectedpowersystems?
b).Discussloadingcapabilitylimitsinatransmissionline.
2.a).Discusstherequirementsandcharacteristicsofhighpowerdevicesfor
FACTScontrollers.
b).ListthebasictypesofFACTScontrollers?Explaineachoneinshort.
3.a).Explainhowpowerflows&typesofpowersinacsystems?
b).Byusingpoweranglecurveexplainhowbychangingthevalueofline
impedancethemaximumamountofactivepowerflowwillchange?
4.a).Derivetheexpressionforactiveaswellasreactivepowerflowin
losslesstransmissionline?Drawnecessaryphasordiagram.
b).Writethefunctionsofparametertradeoffofdevicesinselectionof
highpowerdevices.

89. 89
5.Threebussystems,ithastwogeneratorwithrealpowergeneration
of4p.uatbus1,2p.uatbus2andloadof6p.uatbus3.Suppose
thelines1-2,2-3,and1-3havecontinuousratingsof2p.u,2.5p.u
and4p.u.Theimpedanceratingofline1-2is10ohm,line2-3is5
ohmand1-3is10ohm.Assumebasepoweris1000MVAand
impedancebaseis10000.Identifytheoverloadedline.?
a..Findtheminimumvalueofadditionalseriescapacitiveimpedance
requiredforthecompensationofoverloadedline….ohm
b.Findtheminimumvalueofadditionalseriesinductiveimpedance
requiredforthecompensationofoverloadedline….ohm

90. 90
THANK YOU...!
FOR YOUR ATTENTION