外文翻译-通信网络式的变电站自动化

翻译部分英文原文ASurveyofCommunicationNetworkParadigmsforSubstationAutomationHyoSikYang；Dept.ofComputerEngineering；SejongUniversity,Seoul,KoreaEmail:hsyangsejong.ac.krDaejun；KoreaElectricalPowerResearchInstitute；ByungSeokPark；KoreaEmail:blueonkepri.re.krAbstractIntherealmofsubstationautomation(SA),communicationinfrastructureplaysavitalroleinmediatingbetweenphysicalandvirtualworldsofsubstation.Specificationofdataexchangesthroughstandardizedcommunicationstacksisthereforeanimportantissueforallsubstationequipmentmanufacturersseekingtoprovidevendorinteroperability.Nowadayscompetitiveelectricutilitymarketplace,reliableandrealtimeinformationbecomethekeyfactorforreliabledeliveryofpowertotheendusers,profitabilityoftheelectricutilityandcustomersatisfaction.Theoperationalandcommercialdemandsofelectricutilitiesrequireahighperformancedatacommunicationnetworkthatsupportsbothexistingfunctionalitiesandfutureoperationalrequirements.Ascommunicationarenaischangingdaybyday,theneedforefficientandreliablecommunicationinfrastructuretoaddressSAisevident.Inthisrespect,acommunicationnetworkconstitutesthecoreoftheSA,thusthedesignofcosteffectiveandreliablenetworkarchitectureisacrucialtask.MostoftheexistingcommunicationnetworksclaimtoaddresstheneedofcommunicationarchitectureforSAbutinsomeregardtheseclaimsjustcouldnotfulfilltheconstraintsimposedbyhighlyavailableenvironmentforSA.Thispaperpresentsasurveyandanalysisofthecurrentstate-of-the-artcommunicationinfrastructureintheSA.AsEthernettechnologybecomesmorereliableandalsowidelyavailablewithfiberopticalcommunicationsothispaperalsoexaminesthekeyissuesandrequirementsforEthernetinthesubstationenvironmentandalsoopenssomeresearchchallenges.I.INTRODUCTIONSubstationAutomation(SA)isasupervisorymanagementandcontrolsystemthatliesinbetweentransmissionanddistributionsystems.TheinterestsonSAhavebeenincreasingrapidlyduetoitsnumerousbenefitstoutilities.IthasadvancedfurtherthanatraditionalSupervisoryControlandDataAcquisition(SCADA)systemprovidingadditionalcapabilityandinformationthatcanbeusedtofurtherimproveoperations,maintenanceandefficienciesinsubstations.ThemostsignificantelementsofaSAsystemincluderelaysand/orIntelligentElectronicDevices(IEDs)thatperformvariouscontrol,monitoringandprotectionrelatedoperations.Recentdevelopmentsincommunicationtechnologieshaveenabledreliableremotecontrolsystemswhichhavethecapabilityofmonitoringtherealtimeoperatingconditionsandperformanceofelectricsystems.Thesecommunicationtechnologiescanbeclassifiedintofourclasses,i.e.,powerlinecommunication,satellitecommunication,wirelesscommunication,andopticalfibercommunication.EachcommunicationtechnologyhasitsownadvantagesanddisadvantagesthatmustbeevaluatedtodeterminethebestcommunicationinfrastructureforSA.Powerlinecommunication(PLC)utilizestheexistinginfrastructureofelectricityforcommunicationtherebyofferingabroadcoverageaswellascosteffectivesolutionbutontheotherhandsufferedbynoise,capacity,signaldistortionandsecurityissues1.Wheneveritcomestoremotemonitoring,satellitecommunicationisoptedasoneoftheavailablemeantoachieveit2.Thoughsatellitecommunicationoffersglobalcoverageandrapidinstallationbutperformancestillstheproblemwithunavoidabledelay.OpticalfibercommunicationhastakenthemajorshareofcommunicationduetoitshighcapacityandimmunitycharacteristicsforEMI/RFI(ElectroMagneticInterference/RadioFrequencyInterference).Thoughcostofdeployingfiberopticcommunicationisexpensivebutitisovercomebytheadvantagesoffered.Wirelesscommunicationduetoitsrapiddeploymentandcosteffectivesolutionhasdramaticallychangethetrendofcommunicationparadigmbutstillneedtoaddressthecrucialissuesofcapacity,security,andcoverageinordertomakeitviable.Inthispaper,itisinvestigatedthatwhichcommunicationarchitectureisfeasibleforSA.Inthisregardexistingcommunicationtechnologiessuchaspowerlinecommunication,satellitecommunication,opticalfibercommunication,wirelesscommunicationareexploredtosearchforthebestavailablecommunicationinfrastructure.Therestofthispaperisorganizedasfollows.SectionIIpresentsthecurrentstate-of-the-artcommunicationinfrastructureintheSAandalsopresentanalysisonthemwithrespecttoSA.SectionIIIpresentssuggestedcommunicationarchitectureforSAandalsoproposesafuturedirectionforresearch.Finally,SectionIVsummarizesthecontributionofthispaper.II.STATEOFTHEARTCOMMUNICATIONNETWORKInthissection,areviewofdifferentcommunicationtechnologiesispresentedwiththespecialemphasisontheirapplicationforSA3.A.PowerLineCommunicationPowerlinecommunications(PLC)technologycanusethehouseholdelectricalpowerwiringasatransmissionmedium.PLCusestheelectricalwiresofahomeorbuildingastheconduittotransmitdata.Maximizingtheuseofexistinginfrastructures,PLCisareliableandsecurewaytonetwork.SettingLocalAreaNetwork(LAN)andconnectingmultiplecomputerstoshareInternetaccess,files,printers,oranyotherresources,hasneverbeeneasierthroughPLC.PLCallowsyoutosimplysetupanetworkbypluggingintoanyelectricaloutlettherebyprovidingapassageforinstantconnectivity.Commerciallydeployable,highspeedandlongdistancePLCstillrequiresfurtherresearcheffortsdespitethefactthatPLCmightprovideanalternativecosteffectivesolutiontothelastmileconnectivityproblem1.FollowingarethebenefitsofPLCwhenitcomesforitsapplicationinSA:1)Broadcoverage:BroadCoverageisoneofthemajoradvantagesofPLC.PowerLinesareavailablealmosteverywhereintheworldwherethereisacommunityofhumanbeings.Italsobenefitstheruralareaswherecommunicationinfrastructureisnotavailable.2)Highbandwidth:CurrentPLCtechnologyhasreachedamaximumspeedof45Mbps4.Thisisdividedintoamaximum27Mbpsfordownstreamspeedsand18Mbpsforupstreamspeeds.PLCwillhavethehighestaccessspeeds,comparedtoADSLclockingat512Kbpsandcableat1.5Mbps5.3)Costeffective:Costoverheadontheuserisnegligiblebecauseitutilizestheexistingwirestocarrythecommunicationsignals.Sothisisamongoneofthecheapestmethodsavailableforremotelymonitoringpowerusage.4)Easyinstallation:Aspowerlinesarealmostavailableeverywhereintheworldsoitisveryeasytoinstallascomparedtoanyothercommunicationtechnology.Itdoesnotuseextrawiringbutexistingwiresofpowerlinestherebynotposinginstallationproblemsintermsofresourcesandexperts.DespitethesebenefitsofPLCtherearesomedrawbackstoo:1)Lackofavailability:Communicationoverthepowerlinesmayloseduetotheopencircuitoftheinstalleddevices6.ThisnotonlyrestrictstheusefulnessofPLCforapplicationsespeciallyinvolvingswitches,reclosers,andsectionalizesbutalsoputaquestionmarkonthehighlyavailableenvironmentforSA3.2)Noise:Noiseindatacommunicationisoneofthegrowingconcernswhencommunicationinfrastructureisinstalledintheenvironmentwhereelectricalsignalsaregeneratedandtransmittedatalargescale.ThusitisnotfeasibletoconsiderpowerlinesascommunicationinfrastructureforSAssincepresenceofhighvoltagedevicesinsubstationgenerateanoisyenvironmentforcommunication7.ThesenoisesourcesoverthepowerlinescanresultinhighbiterrorratesduringcommunicationwhichseverelydegradetheperformanceofPLC.3)HighAttenuation:Thecommunicationoverpowerlinesmightbelostbecauseofhighsignalattenuationanddistortionormaydegradethereliabilitytotakecrucialstepsinresponsetoanevent.Physicaltopologyofthepowernetworkandloadimpedancefluctuationoverthepowerlinesarethesourcesforsignalattenuationanddistortion8.PowercablesarenottwistedandalsonothavingpropershieldingresultingfairamountofElectroMagneticInterference(EMI)9.ThusbymakinguseofradioreceiverscommunicationsignalscanbetrappedeasilyordistortedseverelybyintroducingEMI.Therefore,theproperencryptiontechniquesmustbeusedtopreventtheinterceptionofcriticaldatabyanunauthorizedperson.B.SatelliteCommunicationSatellitecommunicationcanofferinnovativesolutionsforremotecontrolandmonitoringofsubstations.Inpracticalapplications,VerySmallApertureTerminal(VSAT)satelliteservicesarealreadyavailablethatareespeciallytailoredforremotesubstationmonitoringapplications10.Furthermore,withthelatestdevelopmentsinelectricsystemautomation,satellitecommunicationisnotonlyusedforremotecontrolandmonitoringofsubstationsbutalsousedforGlobalPositioningSystem(GPS)basedtimesynchronization,whichprovidesmicrosecondaccuracyintimesynchronization11.Inaddition,satellitescanbeusedasabackupfortheexistingsubstationscommunicationnetworks.Incaseofcongestionorlinkfailuresincommunication,criticaldatatrafficcanberoutedthroughsatellites12.Inthissection,bothadvantagesanddisadvantagesofsatellitecommunicationtechnologieshavebeenreviewedwithrespecttoSA.Followingaretheadvantagesofusingsatellitecommunicationforremotemonitoring:1)Geographiccoverage:Satellitecommunicationshaveuniqueadvantagesoverconventionallongdistancetransmissions.Thiscommunicationtrendiscapableofspanninglongdistanceirrespectiveofthephysicalcondition.Thusprovidingacosteffectivesolutionfortheareaswherecommunicationinfrastructuremightnotexistduetoenvironmentalissues.2)HigherBandwidth:Satellitecommunicationhasverylargebandwidthcapacityasitiswidelyusedforthebroadcastingofvideostreaming.Thusthishigherbandwidthcanbeutilizedforthetransmissionofmissioncriticaldataandmessageswithinsubstations.Followingsarethedisadvantagesofusingsatellitecommunicationasacommunicationtechnology:1)Longdelay:Asforasthetransmissioncharacteristicsforsatellitecommunicationareconcerned,roundtripdelayisthegrowingconcernwhichiscomparativelyhigherthanthewirednetwork.Assubstationmessagesaremissioncriticalsoinordertoensureefficientandreliabletransmissionofthesemessagefromonesubstationtoothersubstationthisroundtripdelayneedtobeminimized.2)Satellitechannelcharacteristics:Performanceofsatellitechannelsisgreatlyaffectedbythechangeinoperatingclimateduetoweatherorbytheeffectoffadingtherebydegradingtheefficiencyofthewholesatellitecommunicationsystem13.C.OpticalFiberCommunicationTheOpticalFibertechnologywasfirstdemonstratedin1952forinternalmedical.LaterOpticalfibercanbeusedasamediumfortelecommunicationandnetworkingbecauseofitsflexibilitycaneasilybebundledascables.IncaseofSA,fiberopticalcommunicationisthemostdemandingandeyecatchingcommunicationinfrastructurethatgivesveryhighspeed.OpticalFibercaneasilycarryhighbandwidthdata,makingitpossibletousewithsubstationstosharebandwidthcapacity.Thiswouldalsoallowcosttobereducedbecausebysharingitwithendusers.Therebyofferinghighperformance,reliablecommunicationandgreatercoverageinthehighlyconstrainedenvironmentofsubstationswithrespecttofunctionalandperformanceparameters.FurthermoreopticalfiberisonethedemandingcommunicationmediumforsubstationsascharacterizedbyhighvoltageoperatingenvironmentbecauseofitsEMI/RFIimmunitycharacteristics6.Nowinthebrieffollowingaretheadvantagesofusingopticalfibercommunicationsasacommunicationmedium.1)Coverage:Itisespeciallyadvantageousforlongdistancecommunications,becauselightpropagatesthroughthefiberwithlittleattenuationcomparedtoelectricalcables.Forupto2Kmnoneedtoamplifythesignaloruserepeater.2)LightWeight:Opticalfibersarelightweightandsmallinsize,whichmakesthemidealforapplicationswhererunningcopperwireswouldbeimpractical.3)Security:FiberOpticalcommunicationsareverysecureascomparewiththeotherwayofcommunicationsbecauseitisveryhardtotapintoafibercabletoreaddatasignals14.4)Capacity:ExtremelyhighbandwidthcapacityofopticalfibercommunicationcanprovidehighperformancecommunicationforSAapplications.Currentopticalfibertransmissionsystemsprovidetransmissionratesupto10Gbpsusingsinglewavelengthtransmissionand40Gbpsto1600Gbpsusingwavelengthdivisionmultiplexing(WDM).Inaddition,verylowbiterrorrates(BER=1015)infiberopticcommunicationareobserved.DuetohighbandwidthcapacityandlowBERcharacteristics,opticalfiberisusedasthephysicallayerofGigabitand10GigabitEthernetnetworks.5)Immunitycharacteristics:SinceOpticalfibersareimmunetoenergyradiationandpossibleinterferencefromexternalsources15.HenceOpticalfibersaremoresecurewhenitcomestosignaltrapping,crosstalkandEMI/RFIcharacteristics.Nowtheonlydisadvantageofusingopticalfiberiscost.Thecostoftheopticalfiberitselfisstillexpensivetoinstallforelectricutilities.Itsinstallationisalsoveryexpensiveespeciallyifitisusedforremotecontrollingandmonitoringofsubstations.EventhoughthedisadvantageisonlythecostbutdominantadvantageswillimmediatelyaffecttheconsumerschoicetoinstallthistechnologyforSA.D.WirelessCommunicationWirelesscommunicationisthetransferofinformationoveradistancewithouttheuseofelectricalconductorsorwires.Informationistransferredinthismanneroverbothshortandlongdistances.Wirelesstechnologycarriesthecapabilitiesofwirednetworkstospaceswherecablecannotbeinstalled.SeveraltypesofwirelesstechnologiesarepresentinthemarketforSA6.Themaindifferenceistheirrange.Whencomparedtoconventionalwiredcommunicationnetworks,wirelesscommunicationtechnologieshavepotentialbenefitsincontrollingandmonitoringremotesubstations,e.g.,savingsincablingcostsandrapidinstallationofthecommunicationinfrastructure.Securityisoneofthegrowingconcernsinwirelesscommunicationsinceintelligentradiodevicesareavailablethatcanbeusedtotrapwirelesssignalsintheairtherebyraisingagreatthreatforsecurewirelesscommunication.Furthermorewirelesscommunicationsystemisgreatlysufferedbythelimitationsinbandwidthcapacity,coverageandvulnerabilitytoEMI.Inthebriefthemajorbenefitsofwirelessnetworksoverwirednetworksareexploredhere:1)Flexibility:Themobilityofthedeviceswithintheenvironmentisasimplemattertorelocateacommunicatingdevice,andnoadditionalcostofrewiringandexcessivedowntimeisassociatedwithsuchamove.Itisalsoasimplemattertoaddinacommunicationdevicetothesystemorremoveonefromthesystemwithoutanydisruptiontotheremainderofthesystem.2)Efficiency:Inwirelesstechnology,improveddatacommunicationleadtofastertransferofinformationandtherebyincreasingthewirelessefficiency.3)Cost:Initialoutlayonsettingupthecellsites,thecostofrunningandmaintainingaradiobasedcommunicationsolutionisminimal.Becausewirelesstechnologyenablestheusertocommunicatewhileonthemove,socablingcostisalsoeliminated.4)Rapidinstallation:Wirelessnetworkscanbeconfiguredrapidlyandinstalledascomparedtowirednetworks.Itcanalsobeeasierandcheapertoinstall.Thuscommunicationcanbeinitiatedwithinthecoveragebysimplydeployingshortcommunicationinfrastructure.Followingarethedrawbacksofusingwirelessnetworkinsteadofwirednetworkforcommunication:1)Security:Wirelesstransmissionismorevulnerabletoattackbyunauthorizedusers,posesserioussecuritychallenges,soparticularattentionhastobepaidtosecurity.Verificationofcommunicationentitiesmustalsobeperformedtoensurethatonlyregistereddevicesmaycommunicateusingthenetwork,andthatonlyregistereddevicesmayreceivethedata.Someformofencryptionmayberequiredforcommunicationtoavoidinterceptionofdatatransmittedoverthenetworkbydevicesnottakingpartinthecommunication.2)Interferenceproblem:Interferenceproblemsseemoftenifothersinthesamebuildingalsousewirelesstechnologyorwhereothersourcesofradiosignalsarepresent.Thiscouldleadtopoorcommunicationor,inextremecases,lossofwirelesscommunicationaltogether.Ontheotherhandwirelesscommunicationcanalsobelostduetocongestionwhentoomanywirelessusersinterfereeachother.3)Limitedcoverage:Insomebuildingsgettingconsistentcoveragecanbedifficult,leadingto”blackspots”wherenosignalisavailable.Forexample,instructuresbuiltusingsteelreinforcingmaterials,onemayfinditdifficulttopickuptheradiofrequenciesused.Thoughpublicwirelessnetworkssuchascellularnetwork,WIMAXandetchavegreatercoverageascomparedwithprivatewirelessnetworks,thecoverageofIEEE802.11bisapproximately100m16butasincaseofremotesubstationinlessdenselypopulatedareawirelesscommunicationservicesmaynothavebeendeployed14.4)Capacity:WirelesscommunicationtechnologiesprovidetypicallylowerQoS(QualityofService)comparedtowiredcommunicationnetworks.Itisalsopotentialforradiointerferenceduetoweather,alimitedbandwidthcapacityissupportedandhighbiterrorratesareobservedincommunication.Theapplicationaveragedatarateperenduserislowerthanthetotalbandwidthcapacity,e.g.,maximumdatarateofIEEE802.11bis11Mbpswhiletheaverageapplicationdatarateisapproximately6Mbps16.Similarly,the54Mbpsmaximumof802.11aand802.11gworksoutnearer20Mbpsinreallifeapplications,inbothcasesthewirelessnetworkingisoperatingasslowas10Mbpsevenundergoodconditions17.III.SUGGESTEDCOMMUNICATIONPARADIGMCommunicationinfrastructuresobviouslyhavethepotentialtovirtualizethephysicalworldofSA.HowevertherearemanchallengesthatneedtobeovercomeforthecompleterealizationofSA.ThissectionexplorestheviablecommunicationparadigmforSAandthemostimportantchallengesinthisregard.Thekeyassumptions,analyzedwhileexploringtheexistingcommunicationnetworksinSectionII,forsubstationarecapacity,performance,coverage,security,reliability,accuracy,andavailabilitythatneedtobeaddressedbythesuggestedcommunicationparadigmforSA.AsIEC61850hasstandardizedtheautomationprocessofSA,soaccordingtoIEC61850EthernetpacketisthechoicetotransmitthesubstationmessagewithinthesubstationbecauseofitsperformanceandalsomostoftheproprietarycommunicationsolutionsareavailablewiththeEthernetsupport19.RecentlyEthernettechnologyhaschangedthetrendofcommunicationnetworkbecauseofitsavailability,efficiency,andcosteffectiveness.NowEthernetswitchesarebeingdeployedforlonghaulcommunicationaccessnetworks.AsthelocalsubstationmessagesareinherentlyavailableinEthernetformatsothesemessagescanbetransmittedtoothersubstationwithoutincurringthecostofprotocolconversionataccessnetworkstherebyinsuringefficiency.ThisisoneoftheprimaladvantagesofusingEthernettechnologyinsubstation.Ontheotherhandopticalfibercommunicationsystemshavedramaticallytakentheattentionasadesiredmodeofcommunicationduetoitshighcapacity,efficiency,andsecurity.NowadaysdifferentprojectsarebeingruntomakeuseofopticalfiberatlargescalesuchasFTTH(FiberToTheHome),FFTO(FiberToTheOffice),andFTTC(FiberToTheCurb).NowwhatwesuggestasthedesiredcommunicationparadigmforSAisthecombinationofEthernetasacommunicationprotocol,toefficientlytransmitthesubstationmessages,andfiberopticalcommunicationsystemasacommunicationmediumtoensureefficiency,coverage,andsecurity.EPONisthedesiredcommunicationparadigmthatmeetsSAneedsasitusesEthernetascommunicationprotocolandfiberopticalcommunicationsystemascommunicationmedium.EPONalsoknownasEthernetintheFirstMile(EFM)isacollectionofprotocolsspecifiedinIEEE802.3.20.EPONisanemergi