EHV AC Undergrounding Electrical Power: Performance and Planning

185 Pages·2010·3.83 MB·English

by  Roberto Benato

Power Systems
Roberto Benato · Antonio Paolucci
EHV AC Undergrounding
Electrical Power
Performance and Planning
123
RobertoBenato,Asst.Prof. AntonioPaolucci,Prof.
UniversitàdiPadova UniversitàdiPadova
Dipto.IngegneriaElettrica Dipto.IngegneriaElettrica
ViaGradenigo,6/A ViaGradenigo,6/A
35131Padova 35131Padova
Italy Italy
[email protected]
ISSN 1612-1287 e-ISSN1860-4676
ISBN 978-1-84882-866-7 e-ISBN 978-1-84882-867-4
DOI 10.1007/978-1-84882-867-4
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tomy threewonderfulwomen Monica,
IsabelMariaand LetiziaMaria
Roberto
tomy wife,my sonMarco andmydaughter
Chiara
Antonio
Foreword
ThisisatimeinwhichthedeploymentofHVandEHVinsulatedcablesystemsis
exhibitingsignificantgrowthand,mostimportantly,whenseriousconsiderationis
beinggiventotheadoptionofsuchsystemsinamuchgreatervarietyofcasesthan
inthepast.
Whatthisimpliesisthatinsulatedcablesarecurrentlylookeduponbyusersas
an enabling network solution that can help them address effectively, rapidly and
reliably a variety of complex problems, for example through the deployment of
mixed overhead and underground lines, rather than, as was often the case in the
past,anichesolutiontobeemployedonlywhenabsolutelyinevitable.
This trend, driven by environmentalconcernswhich have made overheadlines
less attractive,and facilitated by technologicalprogresswhichhas madeinsulated
cablesmorecompetitive,requiresanongoingobjectiveevaluationofthepossibili-
tiesofferedbymoderncableandmixedsystems.
Against this background this book represents a timely and useful contribution
towardsabetterunderstandingofthefactorsthatneedtobetakenintoconsideration
whenintroducinginsulatedcablesystemsinthenetwork.
Thebook’sthoroughcoverageofmanyoftheassociatedtechnicalaspects,cou-
pled with its analysis of the broader economic, environmental and social factors
involved,willcertainlybeofgreatinterestforcablesystemusers,cableengineers
andstudentsofelectricalengineering.
Milan,May2009 AldoBolza
vii
Preface
Weshallnotceasefromexploration
Andtheendofallourexploring
Willbetoarrivewherewestarted
Andknowtheplaceforthefirsttime.
T.S.Eliot,FourQuartets
InthedevelopmentoftheACpowersystems,longtransmissionlinesandoverhead
lines(OHL)havebeenconsideredformanyyearsanindissolublebinomial,whereas
theuseofHVandEHVinsulatedcableswasdevotedmostlytoDCsubmarinelinks;
inthelastdecades,astrengthenedsensibilitytowardstheenvironment,withconse-
quentbighindrancestoOHLinstallations,andanincreasedreliabilityofhighqual-
ityextrudedinsulations(cross-linkedpolyethylene–XLPE)ofcableshaveinduced
thetransmissionsystemplannersandgridownerstoinstallnumerousACHVand
EHVcablelines:theyhaveunquestionablequalitiesofadaptabilitytotheproblems
given by the territory when realizing modifications, widening or reinforcementof
thetransmissionnetwork.Nowadays,inthejargonofelectricalengineering,words
such as undergrounding,UGC (UndergroundCables) and mixed lines (a cascade
compositionofOHLandUGC)haveaclearmeaning.
The planningof any new line (OHL, UGC or mixed line) in the electricalgrid
must be always validated by extensive network simulations, among which power
flow,shortcircuit,transientanalyses;generallythosestudiesoughttobepreceded
byapropedeuticalinvestigation,inordertoassistthesystemplannerintheconfigu-
ration,comparisonandchoiceofthemoresuitablesolutions,chieflywhenthefield
ofchoicecanbeverywideasintheinsulatedcablemarket.Infact,atargetofthis
bookwasthedevelopmentofthispropedeuticalphaseregardingtheelectricenergy
transmissionstandpointwithparticularattentiontotheoperatingrequirements.
Startingfromtheclassicalequationsoftransmissionlines,developedmorethan
a centuryago,andbyrearrangingthemwith originalprocedures,theauthorshave
created some novel capability charts (for UGCs in Chapter 3, for mixed lines in
Chapter4)whichimmediatelyvisualizethebestpossibleperformanceswithinthe
limits of current and voltage compatible with the line lifetime and power quality.
Thesecapabilitycharts(whichtakeintoaccountthesteadystateampacityandvolt-
age levels, subtransient voltages, shunt compensation degree and other important
parameters)areofprimaryimportance(inthesamewayofpowercirclediagrams):
theyofferanoriginalandefficientguideextremelyusefulforboththeplanningof
ix
x Preface
UGCormixedlinesystemsandafullcompatibilityoftheirinsertioninthepower
network.
Through the book, there are also several occasions of cultural widening in the
fieldofthecircuittheory:oneofthemostmeaningfulcontributionsistherecovery
ofOssanna’stheory,completelydevelopedin1926(andinthebooknewlypresented
inSection3.9.2).Itgivesasimplebutextremelyelegantandpowerfulanalyticaldi-
rectcomputationofthepossiblevoltageregimesobtainableinanyACpowersystem
byfixingthecomplexpoweratoneofitsports,soavoidingtheiterativeprocedures
uptillnowlargelyused.Thismethod,particularlyusefultocompletethelineperfor-
manceanalysis,oughttobealsogenerallyappreciatedasoneofthemoreimportant
toolinthecircuittheory.
Also, the authors’ attemptin Chapter 6 of framing the economicalcomparison
between UGC and OHL on an engineeringfair basis takes aim at helping the in-
volvedstakeholderstoclearthefieldofsubjectiveimpressions.
Briefly,thebookoffers:
(cid:129) awidepanoramaofthelargeEHVcableinstallationswhichhasbeenenhanced
bymeansofsomedetailedreportsofparadigmaticinstallations(Chapter1);
(cid:129) anoutlineofpositivesequencemodellingtoanalysethesteadystateregimesof
typicalOHLs,ofcross-bonded(withphasetranspositions)cablesystemsandof
gasinsulatedlines(Chapter2);
(cid:129) calltotheconstantuseofsomeinternationalrulesandnationalstandards;
(cid:129) novelcapabilitycharts(withalotofexamplesbothforUGCsandmixedlines)
which offer a throughoutvisualization of transmission line performancescom-
patiblewithchosencurrentandvoltageconstraints;
(cid:129) criteria regarding the energization and de-energization phenomena of no-load
transmissionlines(UGCandmixedlines);
(cid:129) criteria for the dimensioning and check of the shunt reactive compensation of
UGC(uniformlyorlumped);
(cid:129) commentsofeducationalpurposeonthephysicalmeaningofsomeformalana-
lyticalexpressions;
(cid:129) introduction to the multiconductor analy sis of undergrounding with self-made
powerfrequencymatrixprocedures(Chapter5),whichallowsinvestigatingthe
electrical behaviours of all cable conductors (phases and sheaths) with some
case studies and offers the possibility of comparing and validating simplified
approaches;
(cid:129) a technical and economical comparat ive procedure between overhead and ca-
blelineswhichcancontributetotheEnvironmentalImpactAssessmentrecom-
mendedbytheEuropeancommunity(Chapter6).
The authorshopeto havegiventhe electric engineersa modernand sound toolto
facethechallengesofthefutureelectricalgridswheretheundergroundingwillplay
akeyrole.
Padova,June2009 RobertoBenatoandAntonioPaolucci
Contents
1 HVCableWorldStatisticsandsomeLargeInstallations............ 1
1.1 Introduction ............................................... 1
1.2 StatisticsofCableInstalledLengths........................... 3
1.3 LargeInstallationsofEHVCableSystems ..................... 7
1.4 LandandSubmarine150kVACCableLinkSardinia–Corsica:
SAR.CO .................................................. 7
1.5 TheMadrid“Barajas”AirportProject(Spain)................... 11
1.5.1 MilestonesoftheBarajasProject....................... 12
1.5.2 TechnicalCharacteristicsoftheLink.................... 12
1.5.3 TunnelandEarthingSystemCharacteristics.............. 12
1.5.4 PowerEHVCables................................... 14
1.5.5 CableLayingintheTunnel............................ 16
1.5.6 TheTransitionCompoundsandProtectionSchemes....... 17
1.6 380kVDouble-CircuitCableofMixedLineTurbigo–Rho(Italy) .. 19
1.6.1 MilestonesoftheTurbigo–RhoProject .................. 19
1.6.2 TheUndergroundingLinkoftheTurbigo–RhoMixedLine . 20
1.6.3 PowerEHVCables................................... 21
1.7 CableLaying .............................................. 23
1.7.1 TheTransitionCompoundsandProtectionSchemes....... 25
References..................................................... 27
2 ThePositiveSequenceModelofSymmetricalLines ................ 29
2.1 Introduction ............................................... 29
2.2 TheTransmissionMatrixofaUniformLine .................... 29
2.3 ComputationofSingle-CoreCableKilometricParameters ........ 33
2.3.1 Computationofr (Cable) ............................. 33
2.3.2 Computationof`(Cable) ............................. 34
2.3.3 Computationofc(Cable) ............................. 35
2.3.4 Computationofg(Cable) ............................. 36
2.4 ComputationofGILKilometricParameters .................... 37
2.4.1 ComputationofGILApparentKilometricResistancer .... 38
xi
xii Contents
2.4.2 ComputationofGILKilometricInductance`............. 39
2.4.3 TheComputationofGILKilometricCapacitancec........ 41
2.4.4 ComputationofGILKilometricShuntConductanceg ..... 41
2.5 SomeOtherMatrixRelationsDerivingfromtheFundamentalOne . 41
2.6 CascadeConnectionsofTwoPortNetworks(TPN) .............. 42
2.7 ParallelConnectionofEqualTwoPortCircuitsThermally
andElectricallyDecoupled .................................. 43
2.8 TheShuntReactiveCompensation ............................ 45
2.8.1 TheUniformlyDistributedCompensation ............... 45
2.8.2 TheLumpedCompensation ........................... 46
References..................................................... 48
3 OperatingCapabilityofLongACEHVPowerCables.............. 49
3.1 Introduction ............................................... 49
3.2 TheBasicConstraints....................................... 49
3.3 FirstAnalysis:U .ı/,I Constrained........................ 52
0S R
3.4 SecondAnalysis:U .#/,I Constrained ..................... 54
0S S
3.5 VoltagesandCurrentsAlongtheCable ........................ 55
3.6 PowerValuesCompatiblewithBasicConstraints
andwithVoltageLevelsattheReceiving-End................... 57
3.7 No-LoadEnergizationandDe-Energization .................... 60
3.8 PowerCapabilityCharts..................................... 63
3.8.1 TheoreticalLimitsoftheLengthd ..................... 70
3.9 SteadyStateRegimesWithinPowerAreas ..................... 70
3.9.1 EnhancedCapabilityCharts ........................... 72
3.9.2 ApplicationofOssanna’sMethod....................... 75
3.10 CableswithGasInsulation(GILs) ............................ 78
3.11 RegimeswithU ¤230kV................................. 80
0S
3.12 “ReceivingArea”and“SendingArea”asSetIntersection......... 80
3.12.1 TheDeterminationoftheReceivingAreaasSetIntersection 81
3.12.2 TheDeterminationoftheSendingAreaasSetIntersection . 82
3.13 TheAnalysisAlongtheCablewithLumpedShuntCompensation.. 82
3.14 Conclusions ............................................... 86
References..................................................... 86
4 OperatingCapabilityofACEHVMixedLines
withOverheadandCablesLinks................................. 89
4.1 Introduction ............................................... 89
4.2 MixedLines:OHL–UGC–OHL .............................. 90
4.3 TheTransmissionMatricesfortheSystemStudy ................ 92
4.4 FirstAnalysis.............................................. 92
4.5 SecondAnalysis ........................................... 94
4.6 TheCapabilityCharts....................................... 96
4.6.1 PhaseVoltageLevelsatR............................. 99
4.7 No-LoadEnergizationandDe-Energization .................... 99