AC Auxiliary Systems In Power Substations (Design ...

Substation AC auxiliary systems are typically used to supply loads such as transformer cooling, oil pumps, and load tap changers, ... Searchfor:CyberMondayOffer❱❱Get20%OFFonProPremiummembershipand30%OFFoncourses&bundleswithdiscountcodeCYBERMONDAY21(expiresonDec3rd).MoreInformation»PowerSubstation/Protection/TransformersACAuxiliarySystemsInPowerSubstations(DesignRequirementsandEquipment)ByEdvard|February,14th2018|6comments|Translate|SavetoPDF♛Subscribe|Share!Home/TechnicalArticles/ACAuxiliarySystemsInPowerSubstations(DesignRequirementsandEquipment)TypicalLoadsSuppliedSubstationACauxiliarysystemsaretypicallyusedtosupplyloadssuchastransformercooling,oilpumps,andloadtapchangers,circuitbreakeraircompressorsandchargingmotors,outdoordeviceheaters,outdoorlightingandreceptacles,motor-operateddisconnectingswitchesandcontrolhouse.ACAuxiliarySystemsInPowerSubstations(DesignRequirementsandEquipment)Controlhouseusuallyincludeslightingandreceptacles,heating,ventilatingandairconditioning,batterychargerinputandwaterwellpump.Now,let’sdiscussthefollowingtopicsaboutmaindesignrequirementsfortypicalACauxiliarysysteminapowersubstationandelectricalequipmentusedforimplementing:DesignRequirements:DemandLoadNumberofPrimaryFeedsOverheadorUndergroundEntryCriticalLoadsSecondaryVoltageLevelTransferSchemeAuxiliarySystemFaultCurrentsEquipmentForACAuxiliarySystems:TransformersElectricalPanelboardsLightingandHeatingEquipmentSummaryDesignRequirements1.DemandLoadTabulatetheconnectedkVAofallsubstationACloadsandapplyademandfactortoeach.DemandkVAisusedtosizetheauxiliarytransformer(s).Loaddiversityandloadfactorneednotbeconsideredinthiscase.Inauxiliarytransformersizing,examinethesubstationgrowthrate.Ifexpansionisplannedinthenearfuture,considertheestimateddemandloadoftheexpansioninthetransformersize.Ifexpansionisinthefarfuture,itmaybeeconomicallyadvantageoustoplanfortheadditionofatransformeratexpansiontime.GobacktoContents↑2.NumberofPrimaryFeedsInsmalldistributionsubstationsoneauxiliarytransformerisusuallysufficient.Assubstationsizeincreases,customerloadcriticalityincreases.Adecisionhastobemadeastoredundancyofsubstationauxiliaryservicesinlightofeconomicsandcustomerrequirements.Largetransmissionsubstations,servicinglargeloadblocks,anddistributionstations,shouldhavedualfeedersservingtwoseparateauxiliarytransformers.Whendualfeedsareselected,locatetwoseparate,independentsourcessothelossofonewillnotaffectserviceoftheother.Designatetheleastreliableasthealternativesupply.Apopularoptiontoconsiderinthiscaseistheuseofatertiarywindingofthepowertransformerasanormalsource.Analternativesourcecouldbeadistributionfeederatacustomerservicelevel,480or240volts,singleorthreephase.Dependingonauxiliarysecondaryvoltagelevelselected,thiscouldeliminateonetransformer.Figure1–MVdualfedradialnetworkwithnocoupler(Themainswitchboardisfedbytwosourceswithcoupler.Switchboards1and2arefedbytwosourceswithnocoupler,theonebackinguptheother.Servicecontinuityisgood.Thefactthatthereisnosourcecouplerforswitchboards1and2meansthatthenetworkislessflexibletouse.)GobacktoContents↑3.OverheadorUndergroundEntryTheauxiliarysource(s)couldbeeitheroverheadorundergrounddistributionlines.Whenundergroundingwithinthesubstationproperty,evenfromanoverheadsource,direct-buriedconduitisrecommended.Aspare,capped,conduitshouldbeinstalledtominimizedowntimeifacablefailureoccurs.Thefaultedcablecanalwaysberemovedafterservicerestoration.GobacktoContents↑4.CriticalLoadsSomelow-voltageloadshavetobemaintainedatalltimes:Batterychargerswhich,throughthebatteries,supplybreakertripandclosecircuitsaswellascommunicationcircuitsTransformercoolingPowercircuitbreakercompressorsandmotorsTroublelightreceptaclesinthestationyardSecuritylightingBreakercontrolcircuitsFirealarmcircuit(s)ElectricheatingSubstationautomationcircuitryCriticalloadsforeachstationshouldbedetermined.Theseloadsshouldbeservedfromapanel(s)fedfromthenormalsourceandrepresentingtheminimumloadfortransfertoalternativesupply.GobacktoContents↑5.SecondaryVoltageLevelSeveralsecondaryvoltageorutilizationlevelsareavailableforACauxiliaries.Forthepurposesofstandardization,onagivenpowersystemitisbestthatonlyonelevelbeselected.Thisisnotalimitingrule,however.Anexceptioncouldbejustified.Possiblesecondaryvoltagelevelsareasfollows:1.480/240Volts,Three-PhaseDeltaThree-phasetransformerfansandoilpumpsneedtobespecifiedat480volts.Inpractice,theunitsareratedat460/230volts,butthisisinsidetheNEMAplus10percentvoltagerequirement.Otherloadsmaybespecifiedateither480or240volts,singlephase.Thissystemisungroundedandshouldbeusedwithagrounddetectionsystemsothata“fault”oronelegofthesystemwillcauseanalarm.Thesystemshouldtripwhenasecondlegonthesystemisgrounded.Figure2–480/240Volts,Three-PhaseDelta2.480/277Volts,WyeConnected,Three-Phase,Four-WireThree-phasetransformerfansandoilpumpsneedtobespecifiedat480volts.Inpractice,motorsarerated460/230volts,butthisiswithintheNEMAplus10percentvoltagerequirement.Theadvantagehereisthatluminairescanbeequippedwith277-voltballasts,savinglightingtransformercostsoveruseofmorecommon120-voltlampedluminaires.Conveniencereceptaclesarefedthroughsmalldry-type480-120volttransformers.Figure3–480/277Voltsand208/120VoltsWyeConnected,Three-Phase,Four-Wire3.208/120Volts,Wye-Connected,Three-Phase,Four-WireThree-phase208voltsorsingle-phase120voltsoracombinationofthetwocanbeusedfortransformercooling(Figure3).Combinationpowerandlightingpanelscanbeused,resultinginreducedlaborandmaterialcosts.Thissavingcouldbeoffsetbyhigherconductorcostsascomparedtothe480-voltsystem.Receptaclescanbeservedwith120voltsdirectly.4.240Volts,Three-PhaseDeltaThree-phasetransformerfansandoilpumpsneedtobespecifiedat240volts.Inpractice,themotorsareratedat230volts,butthisisinsidetheNEMAplus10percentvoltagerequirements.Thissystemisungroundedandshouldbeusedwithagrounddetectionsystemsothata“fault”ononelegofthesystemwillcauseanalarm.Thesystemshouldtripwhenasecondlegonthesystemisgrounded.Figure4–240Volts,Three-PhaseDelta5.240/120Volts,Delta-Connected,Three-Phase,Four-WireThisisthemostcommonlevelinuseinmoderate-sizesubstations.Onephaseoftheauxiliarytransformeriscentertappedtoobtain120volts.Combinationpanelscanbeused,and240-voltsingle-phaseloadscanbeserved.Figure5–240/120Volts,(Open)Delta-Connected,Three-Phase,Four-Wire6.240/120Volts,OpenDelta-Connected,Three-Phase,Four-WireThisisessentiallythesameasthecloseddeltaconnectionexceptonly58percentofthekVAcapacityofthethreetransformerscanbeused.Thisconfiguration(Figure5)willprovideconstructioneconomyforamedium-sizeinstallationorfortemporaryuse.Withsingle-phaseunits,thethirdtransformercanbeaddedinthefutureforincreasedkVAcapacity.Itisfrequentlyusedforconstructionpowerwhereboththree-phaseandsingle-phasesuppliesarerequired.7.240/120Volts,Single-Phase,Three-WireThisis“residential”servicebutapplicabletosmallsubstations.Commonpanelscanbeused,withtwoavailablevoltages.Figure6–240/120Volts,Single-Phase,Three-WireGobacktoContents↑6.TransferSchemeWheretwosources,normalandalternative,arefeedingsubstationauxiliaries,ameanstotransferfromonetotheotherhastobeestablished.Atanattendedstationthiscanbeamanualtransferarrangement.Automatictransferhastobeprovidedatanunattendedstation.Transferisdoneonthesecondarysideforequipmenteconomy.Figure7–NECArticle700:EmergencySystemsArticle700oftheNationalElectricalCode(NEC)asshowninfigure7–outlinesgeneralrequirementsforthistypeofscheme.AtypicalconfigurationisshowninFigure8.Transferswitchselectionisanimportantfactorinthesystemdesign.Operationshouldbe“breakbeforemake”double-throwoperationtopreventshortingthetwosources.Mechanicalinterlockingshouldbeprovidedtoensuretheswitchcanbeinonlyoneofthetwopositions.TheswitchshouldhaveanamperewithstandcapabilityforfaultsatpointsA,B,andCofFigure8.ThefaultatCwillbehighest,thefeederimpedancetoBandAlimitingthefaultcurrenttoanamountbelowthatatC.TheauxiliarysysteminFigure7assumestransferofallloads.Thefullloadcurrentofthe150kVAtransformeris360amperes,soa400-ampereswitchwouldbeselected.Figure8–TypicalACAuxiliarySystemAssuminga250,000kVAsource,two500kcmil,3.05-meter(10-foot)feedersperphasetotheswitch,and4percenttransformerreactance,thefaultcurrentisapproximately10,000amperes.Thisvalueiswellwithinmanufacturers’standardratingsfor400-amperefullloadtransferswitches.Automatictransferswitchesarebuilttodetectemergencyconditionsandtransfertothealternativesupplywhenthenormalsupplyfallsto83percentofratedvoltage.Returntonormalsupplyisaccomplishedthroughanadjustabletimedelayatapproximately92to95percentofratedvoltage.Avarietyofacces-soriesareavailablewithtransferswitches.Manufacturers’dataisreadilyavailable,andtheengineershouldconsultsuchdatawhenspecifyingatransferswitch.Providemeanstoalarmforlossofvoltagefromeithersource.GobacktoContents↑7.AuxiliarySystemFaultCurrentsThedeterminationoffaultcurrentsinthree-phaseacauxiliarysystemsisjustasbasicasthedeterminationofloadcurrentsinsizingcircuitbreakersorfuses.Theprotectivedevicehastooperateoropenduringfaultsaswellascarryloadcurrentduringnormalconditionsorequipmentdamagecouldresult.Thesymmetricalshortcircuit(fault)currentiscomputedusingEquation1:IF=Line-to-LinekV/(√3×OhmsResistance)Ohmsreactanceisthetotalreactanceofallcurrent-carryingpartsfromthesourcetothefault.InFigure8abovethe250,000kVAsourcehasareactanceof0.00023ohms.The150kVAtransformerreactanceis0.0023ohms,thecurrenttransformer0.0005ohms,the3.05-meter(10-foot)cableabout0.001ohms,andsoforth.AllreactancesaretotaledandusedinEquation1.TheasymmetricalfaultcurrentisafunctionofthefaultcircuitX/Rratio.Amultiplyingfactor(1.7)fortheasymmetricalcurrentissatisfactoryforauxiliarypowersystemcalculations.FuseandcircuitbreakermanufacturershavehandbookswithX,R,andZvaluesfortransformers,currenttransformers,cables,etc.,togetherwithmethodsfordeterminingprotectivedeviceratingsbasedonestimatedfaultcurrents.GobacktoContents↑EquipmentForACAuxiliarySystems1.TransformersANSIStd.C57.12.25andANSIStd.C57.12.26areapplicableforselectionofACauxiliarysystempad-mountedtransformers.ThistypeoftransformerisgoodforlargesubstationauxiliaryserviceuseThesecondaryvoltagelevelslistedinaboveSection‘Secondaryvoltagelevel’aremanufacturers’standards.Considerthefeasibilityofestablishingsubstationauxiliarysystemvoltageatthesamelevelasthatforservingundergroundcustomers.Withthisstandardization,sparetransformerscanbestockedandbothcustomerandsubstationservicemaintainedatminimumcost.Pad-mountedtransformerscanbepurchasedwithfusedswitchesontheprimarysidefortransformerfaultcurrentprotection.Highvoltagefuses,inthisusesizedforfull-loadtransformerprimarycurrents,willinherentlyhavesufficientcurrentinterruptingratingstoprotectthetransformersunderfaultconditions.Primaryloadbreakswitchesarealsoavailable.Ifthenormalandalternativesourcesareoverhead,pole-mounted,andhookstickoperated,fusedswitchesareapossiblesolutiontotransformerprimaryprotection.Undergroundcableisusedfortheconnectionfromtheswitchestothetransformerpad.ANSIStd.C57.12ANSIStd.C57.12.25–Pad-MountedCompartmental-Type,Self-Cooled,Single-PhaseDistributionTransformerswithSeparableInsulatedHigh-VoltageConnectors;HighVoltage,34500GRDY/19920VoltsandBelow;LowVoltage,240/120Volts;167kVAandSmaller.ANSIStd.C57.12.26–Pad-MountedCompartmental-TypeSelf-Cooled,Three-PhaseDistributionTransformersforUsewithSeparableInsulatedHigh-VoltageConnectors,HighVoltage,34500GRDY/19920VoltsandBelow;2500kVAandSmaller.Pad-mountedtransformersandthekVAratingspreviouslymentionedapplytoafairlylargesubstation.Forsmallerinstallations,structure-mounteddistributiontransformers,properlyapplied,canbeused.GobacktoContents↑2.ElectricalPanelboardsThedefinitionofabranchcircuitpanelboardintheNEC(Article384)isonehavingmorethan10percentofitsovercurrentdevicesrated30amperesorlessforwhichneutralconnectionsareprovided.Additionally,thenumberofbranchcircuitdevicesinoneenclosureislimitedto42poles.Switchboardsdifferfrompanelboardsinthatswitchboardsarefreestanding.Frontorrearaccesstolineandloadterminalsarevendoroptions.Branchescanbegroupmountedorindividuallymounted,withorwithoutbarriers.EnclosuresshouldbespecifiedNEMA1,generalserviceforindooruse,orNEMA3R,raintightforoutdooruse.Panelboardsareavailableforflushorsurfacemounting,withfusibleorcircuitbreakerbranchcircuits.Mainbreakers,ifrequired,canbefurnished.VoltageratingsforanylevelselectedfromaboveSection‘Secondaryvoltagelevel’canbesupplied.Themaindecisiontobemadeinpanelboardselectioniswhethertousefusibleorcircuitbreakerbranches.Thebranchcircuitdeviceisusedtoprotectthebranchcircuitwiring,sothedecisionshouldbebasedonfirstcostandmaintainability.Foraverysmallinstallationwithfewcircuits,fuseswillmeanlowerfirstcost.Iffusesareselected,aninventoryhastobemaintainedatthesubstation.Thereisalwaysthepossibility,howeverremote,thatthewrongsizecouldbeusedasreplacementforablownfuse.Theseproblemsdonotexistwithcircuitbreakers,aplusfactorrelativetomaintainability.Forlightingcircuitserviceexclusively,inamoderatelysizedinstallation,acircuitbreakerpanelboardofferstheadvantageofswitchingthelights,therebyeliminatinglightswitches.Forexteriorlighting,theengineermayconsidermountingaweatherproofthree-polemagneticcontactorfedfromanadjacentoutdoorpanel.GobacktoContents↑3.LightingandHeatingEquipmentLightingOutdoorlightingservestwobasicpurposes:substationsecurityandsafety.Dependingonthearea,certainluminairesmaybeusedduringhoursofdarknessforsubstationsecurity.Thesearephotoelectricallycontrolled.AmicrowavetowercouldrequireFAAlighting.Thiswouldalsobecontrolledphotoelectrically.Lampsforoutdooruseareessentiallyincandescent,mercury,orsodiumlamps.Exceptforanunusualcondition,thelampspresentlyinuseonagivensystemshouldcontinueinuse,simplifyinginventory.Theunusualconditioncouldbeanewlargesubstationwhereadifferentsourceisdesirableandaseparate,on-stationinventorycanbekept.Luminairesforsubstationuse,fromthebasicflatdomereflectortoIlluminatingEngineeringSociety(IES)patternrefractors,areavailable.Pole-toporbracketmountingscanbeused.Theengineer,withthepropervendordata,candevelopalightinglayouttosatisfythepurposerequired.Yardlightingdesignisbeyondthescopeofthisguide.Thebasicrequirementsareoneortwofoot-candlesinequipmentareas.Substationlighting(photocredit:GenluxLighting)Conveniencereceptaclesshouldbeinequipmentcabinetsandalsostrategicallylocatedtoserve50-footextensioncordswithtroublelights.Conveniencereceptaclesinthesubstationyardshouldhavegroundfaultinterruptionprotection.Indoorlightingshouldbedesignedformaximumoperatorconvenience.Luminairesshouldbelocatedtoadequatelyilluminaterelayandcontrolpanelfronts.Withfluorescentunits,4-footlampsarerecommended,sincestorageiseasierthanfor8-footlamps.Provideduplexreceptaclesforextensioncordlightsforinitialpanelinterconnectionwork,relaysetting,andplantmaintenance.HeatingandventilationProvidecontrolhouseelectricheatingforcomfortandfreezeprevention.Thiscanbedonewithceilingorwall-mountedelectricunitheatersand/orelectricbaseboardheatingunits.Providepoweredroofventilator(s)alongwithfloor-level,manuallyoperatedwalllouver(s)toprovideforthreetofiveairchangesperhour.Louversshouldbeprovidedwithfusiblelinksasameans,incaseoffire,tokeepdamagetoaminimum.Gravityroofventilatorsshouldalwaysbeinstalledtopreventconcentrationofhydrogeninbatteryrooms.Airconditioningofthecontrolhouse,whererequired,isbestprovidedbypackagedthrough-wallunit(s).Packagedthrough-wallunitspumpanenergy-efficientheating/coolingoptionformostclimatesandcanhavesupplementalresistanceheat.Built-inresistanceheatersareprovidedinsometoprovideall-seasonuse.Vendordataisavailableasanaidinselectingsuchunits.GobacktoContents↑SummaryAsubstationacauxiliarysystemconsistsmainlyofthefollowingparts:Oneortwoincomingprimaryfeed(s)seldomabovethe34.5kVlevel,onedesignatednormalsource,theotherdesignatedalternativesource.Thesourcesshouldbeasindependentaspossible.Oneortwoauxiliarytransformerstoreducetheprimaryvoltagetotheutilizationlevel.Amainswitchboard,usuallylocatedoutdoorsbetweenthetwotransformers.Thisswitchboardhousesthetransferswitchandfusesorcircuitbreakerstofeedbothcontrolhouseandyardpanelboards.Panelboards(indoororoutdoor)havingcircuitbreakersorfusessizedfortheloadsinvolvedshouldhaveapproximately20percentsparebreakersorfuses.AllbranchcircuitbreakersfeedingACyardcircuitsshallbeGroundFaultInterruptingtype(GFI).Wherefusedpanelsareselected,yardreceptaclesshallbeGFItype.GobacktoContents↑Reference//DesignGuideforRuralSubstationsbyUnitedStatesDepartmentofAgricultureRelatedEEP'scontentwithsponsoredlinksPremiumMembershipGetaccesstopremiumHV/MV/LVtechnicalarticles,electricalengineeringguides,researchstudiesandmuchmore!Ithelpsyoutoshapeupyourtechnicalskillsinyoureverydaylifeasanelectricalengineer.MoreInformationEdvardCsanyiElectricalengineer,programmerandfounderofEEP.HighlyspecializedfordesignofLV/MVswitchgearsandLVhighpowerbusbartrunking(<6300A)inpowersubstations,commercialbuildingsandindustryfacilities.ProfessionalinAutoCADprogramming.6CommentsHalidMwasumileAug04,2020ThisarticleisusefulasitgivesgeneraloverviewonsubstationdesignrequirementsReplyA.AzizAug21,2019ilikethesubjectwhichusefulinmymajorworkandupdatethankyoubutmyareaneedmoreloadinACwhichtheloadinbiggerandsometimeaffectthemainboardintheymakeupgradeandnotconsidertheloadaswellthankyouReplyPauloJun24,2018Hi!IneedhelptosizingtheMVcablesuitableforthefollowingsituation:Ihavea220/60/15kVPowerTransformer.ThetertiaryofthePowerTransformerwillbeconnecttoa15/0.4kV(150kVA)TransformerforsupplyingtheSubstationAuxiliaryServices.ThemaximumtertiarypowerofthePowerTransformeris20MVA.Bymycalculationsthemaximumcurrentinthetertiarywillbe20MVA/(1.73x15kVA)=769,8A.Themaximumcurrentinprimaryofthe15/0.4kV(150kVA)Transformeris5,8A.InthiscasewhatwillbethecriteriontobeappliedforthedimensioningoftheMVCablethatconnectsthetertiaryofthePowerTransformertotheAuxiliaryServicesTransformer.Bestregards,ReplyJOSEPHDOMBROWSKI,PEFeb20,2018MYEXPERIENCECOMEFROMTHENONUTILITYSIDE(LARGEPURCHASERSOFPOWERATHIGHERTHAN480VOLTUPTO35KVSYTEMS.WHILETHEREAREISMUCHTHATISWORHTWHILEINYOUARTICLEIWOULDLIKETOPOINTOUT:1)MOSTAUXILLARYDEVICESCANCOMEWITHASPECIFIEDVOLTAGEOFYOURCHOOSING.ITRYTOUSECOMMONLYAVAILABLEVOLTAGESTOMINIMIZERESTORATIONDELAYSINTHEEVENTOFAPROLEM.2)IHAVEFOUNDTHAT240VDELTAPOWERSOURCESANDUTILIZATIONEQUIPMENTAREGETTINGLESSANDLESSCOMMON.FOREXAMPLE460VOLTRATEDEQUIPMENTISAUTILIZATIONVOLTAGEFOR480VOLTSYTEMS.MULTIRATEDMOTORS(E.G.200/230VOLT)AREMADETOBEOPERATEDON208Y/120VOLTSYSTEMSASWELLAS240VOLTSYSTEMS(WITHANAPPRORIATEMOTORCURRENTOVERLOADDEVICEIFAPPLICABLE).3)ASTHESPECIFIERITISMYRESPONSIBILITYTOENSURETHEVOLTAGESAREINTERNALLYCOORDINATEDDURINGDESIGNANDREVIEWEDDURINGTHESUBMITTALPROCESS.4)NOTSUREWHEREADVICEONBALLASTSISCOMINGFROM,LEDSEEMSTHEWAYTOGO.FARLESSLOADINVOLVED,LIFESPANISLONGANDHEATISN’TTYPICALLYANISSUEWHEREICOMEFROM!ReplyHeriSetiawanFeb16,2018ThisarticleisinterestingandIwouldliketohaveitReplyEgildaCastilloFeb15,2018ThisarticleisinterestingandIwouldliketohaveitReplyLeaveaCommentCancelReplyTelluswhatyou'rethinking...wecareaboutyouropinion!Pleasekeepinmindthatcommentsaremoderatedandrel="nofollow"isinuse.So,pleasedonotuseaspammykeywordoradomainasyourname,oritwillbedeleted.Let'shaveaprofessionalandmeaningfulconversationinstead.Thanksfordroppingby!Yourrealname*Emailaddress*ProvethatyouarenotR2D2.Solvesomemath:three  ×  three  =  ΔCyberMondayOffer🎀Get20%OFFonEEPProPremiummembershipand30%OFFoncourses&bundleswithcodeCYBERMONDAY21(expiresonDecember3rd).MoreInfoSubscribetoNewsletterSubscribetoourWeeklyDigestnewsletterandreceivefreeupdatesonnewtechnicalarticles,videocoursesandelectricalguides.Subscribe©2021EEP-ElectricalEngineeringPortal.AllRightsReserved|PrivacyPolicy|TermsandConditionsThecontentiscopyrightedtoEEPandmaynotbereproducedonotherwebsites.TechnicalArticlesTechnicalArticlesCategories(42)ElectricalGuidesElectricalEngineeringPowerSubstationsControl&ProtectionGenerationT&DABBProtectionBooksSiemensEEBasicsSchneiderElectricCTsIndustrialAutomationDataCenterGuidesABBDrivesGuidesAlternativeEnergyElectricalDesignDocsElectricalToolsExcelSpreadsheetsSoftwareReviewsVideoTrainingsElectricalEngineeringPLCProgrammingTesting&Commiss.EEResourcesHomeSitemapEEPAcademyCoursesContact/AdvertisementContactAdvertisementFreeNewsletterEEWeeklyDigestFacebookLinkedinLinkedinTwitterPremiumMembership♛PlansandPricingLogIn