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PART9.2:BUILDINGSERVICESELECTRICALANDALLIEDINSTALLATIONS

CONTENTSPage

9.2.1SCOPE2

9.2.2DEFINITIONSANDCOVENTIONALSYMBOLS2

9.2.3GENERALREQUIREMENTS10

9.2.4PLANNINGOFELECTRICALINSTALLATIONS11

9.2.5DISTRIBUTIONOFSUPPLYANDCABLING22

9.2.6WIRING45

9.2.7FITTINGSANDACCESSORIES59

9.2.8EARTHING67

9.2.9INSPECTIONANDTESTINGOFINSTALLATION73

9.2.10TELECOMMUNICATIONANDOTHERMISCELLANEOUSSERVICES82

9.2.11LIGHTINGPROTECTIONOFBUILDINGS86

APPENDIXA95

APPENDIXB98

APPENDIXC99

APPENDIXD100

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PART9.2:BUILDINGSERVICESELECTRICALANDALLIEDINSTALLATIONS

9.2.1 SCOPE

Thissectioncoverstheessentialrequirementsforelectricalinstallationsinbuildingstoensureefficientuseofelectricity includingsafety from fireandshock.Thissectionalso includesgeneralrequirementsrelatingtolightingprotectionofbuildings.

9.2.2 DEFINITIONSANDCONVENTIONALSYMBOLS

9.2.2.1 ForthepurposeofthisSection,thefollowingdefinitionsshallapply.

AccessoryAdevice,otherthancurrentusingequipment,associatedwithsuchequipmentorwiththewiringonaninstallation.

Apparatus Electrical apparatus including all machines, appliances and fittings in whichconductorsareusedorofwhichtheyformapart.

Appliance An item of current using equipment other than a luminaire or an independentmotor.

Bunched Cables are said tobe bunchedwhen twoormore are containedwithin a singleconduit,duct,ducting,ortrunkingor,ifnotenclosed,arenotseparatedfromeachother.

Cable A length of single insulated conductor (solid or stranded), or two ormore suchconductors,eachprovidedwith itsown insulation,whichare laidup together. The insulatedconductoror conductorsmayormaynotbeprovidedwith anoverallmechanicalprotectivecovering.

Cable,ArmouredAcableprovidedwithawrappingofmetal (usually in the formof tapeorwire)servingasamechanicalprotection.

Cable,FlexibleAcablecontainingoneormorecores,each formedofagroupofwires, thediametersofthecoresandofthewiresbeingsufficientlysmalltoaffordflexibility.

Cable,MetalSheathedAninsulatedcablewithametalsheath.

Cable, PVC SheathedInsulated A cable in which the insulation of the conductor is apolyvinylchloride(PVC)compound;withPVCsheathalsoprovidingmechanicalprotectiontotheconductorcoreorcoresinthecable.

Cable,WeatherproofAcablesoconstructedthatwheninstalledinuncoveredlocations,itwillwithstandallkindsofweathervariations(SeebelowfordefinitionofWeatherproofing).

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Cable,ELPEAcableinwhichtheinsulationoftheconductoriscrosslinkedpolytheneandthemechanical protection is provided for the core or cores by a sheath of a poly chloridecompound.

Ceiling Rose A fitting (usually used to attach to the ceiling) designed for the connectionbetween theelectrical installationwiringanda flexible cord (which is in turn connected toalampholder).

Circuit An assembly of electrical equipment supplied from the same origin and protectedagainstovercurrentbythesameprotectivedevice(s).Certaintypesofcircuitarecategorizedasfollows:

(a) Category/CircuitA circuit (other thana firealarmoremergency lighting circuit)operatingatlowvoltageandsupplieddirectlyfromamainssupplysystem.

(b) Category2CircuitWiththeexceptionoffirealarmandemergencylightingcircuits,any circuit for telecommunication (for example, radio, telephone, sounddistribution, intruder alarm, bell and call and data transmission circuits)which issuppliedfromasafetysource.

(c) Category3CircuitAfirealarmcircuitoranemergencylightingcircuit.

Circuit Breaker A mechanical switching device capable of making, carrying and breakingcurrentsundernormalcircuitconditionsandalsoofmaking,carryingforaspecifiedabnormalcircuitconditionssuchasthoseofshortcircuit.

NOTEACircuitbreaker isusually intendedtooperate infrequently,althoughsometypesaresuitableforfrequentoperation.

Circuit,FinalSubAnoutgoingcircuitconnectedtoonewaydistributionboardandintendedtosupply electrical energy at one or more points to current, using appliances without theinterventionofafurtherdistributionboardotherthanaonewayboard.Itincludesallbranchesandextensionsderivedformthatparticularwayintheboard.

CleatAninsulatedincombustiblesupportnormallyusedforinsulatedcable.

Conductor,AerialAny conductorwhich is supportedby insulatorsabove thegroundand isdirectlyexposedtotheweather.

NOTEFourclassesofaerialconductorsarerecognized:

a) Bareaerialconductors,b) Coveredaerialconductors,c) Insulatedaerialconductors,andd) Weatherproofneutralscreenedcable.

Conductor,BareAconductornotcoveredwithinsulatingmaterial.

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Conductor,EarthedAconductorwithnoprovisionforitsinsulationfromearth.

Conductor,InsulatedAconductoradequatelycoveredwithinsulatingmaterialofsuchqualityandthicknessastopreventdanger.

ConductorofaCableorCoreTheconductingportionconsistingofasinglewireorgroupofwires,assembledtogetherandincontactwitheachotherorconnectedinparallel.

Connector The part of a cable coupler or of an appliance couplerwhich is providedwithfemalecontactandisintendedtobeattachedtotheflexiblecableconnectedtothesupply.

ConnectorBoxor JointBoxAbox formingapartofwiring installation,provided tocontainjointsintheconductorsofcablesoftheinstallations.

Connector for Portable Appliances A combination of a plug and socket arranged forattachmenttoaportableelectricalapplianceortoaflexiblecord.

Consumers Terminals Theendsof theelectrical conductors situatedupon any consumerspremisesandbelongtohimatwhichthesupplyofenergyisdeliveredfromtheserviceline.

Cord, Flexible A flexible cable having conductor of small crosssectional area. Two flexiblecordstwistedtogetherareknownastwinflexiblecord.

Core of a Cable A single conductor of a cable with its insulation but not including anymechanicalprotectivecovering.

CutoutAnyapplianceforautomatically interruptingthetransmissionofenergythroughanyconductorwhenthecurrentrisesaboveapredeterminedamount.

DampSituationAsituation inwhichmoisture isetherpermanentlypresentor intermittentlypresenttosuchanextentastobelikelytoimpairtheeffectivenessofaninstallationconformingtotherequirementsforordinarysituations.

DeadAportionof thecircuit (normallyexpected tocarryavoltage)atornearaboutearthpotentialorapparentlydisconnectedfromanylivesystem.

Direct Earthing System A system of earthing inwhich the parts of an installation are soearthedasspecifiedbutarenotconnectedwithin the installation to theneutralconductorofthesupplysystemortoearththroughthetripcoilofanearthleakagecircuitbreaker.

DistanceAreaorResistanceArea (forEarthElectrodeonly)Theareaofground (aroundanearth electrode) within which a voltage gradient measurable with ordinary commercialinstrumentsexistswhentheelectrodeisbeingtested.

Discrimination(OverCurrentDiscrimination)Coordinationoftheoperatingcharacteristicsoftwoormoreovercurrentprotectivedevicessuchthat,ontheincidenceofovercurrentswithin

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stated limits, thedevice intended tooperatewithin these limitsdoes so,while theothersdonot.

NOTES

1. Protective devices should have discrimination so that only the affected part(minimum section)of thecircuit is isolated,even thoughanumberofprotectivedevicesmaybeinthepathoftheovercurrent.

2. Distinction ismadebetweenseriesdiscrimination involvingdifferentovercurrentprotective devices passing substantially the same overcurrent and networkdiscrimination involving identicalprotectivedevicespassingdifferentproportionsoftheovercurrent.

EarthTheconductivemassoftheearth,whoseelectricpotentialatanypointisconventionallytakenaszero.

EarthContinuityConductorTheconductor, includinganyclamp,connecting to theearthingleadortoeachotherthosepartsofaninstallationwhicharerequiredtobeearthed.Itmaybeinwholeorinpartthemetalconduitorthemetalsheathorarmourofthecables,orthespecialcontinuityconductorofacableorflexiblecordincorporatingsuchaconductor.

EarthElectrodeAconductororgroupofconductorsinintimatecontactwithandprovidinganelectricalconnectiontoearth.

EarthFaultAccidentalconnectionsofaconductortoearthwhentheimpedanceisnegligible,theconnectioniscalledadeadearth.

EarthingLeadThefinalconductorbywhichtheconnectiontotheearthelectrodeismade.

Earth Leakage Circuit Breaker System A system of earthing in which the parts of aninstallation,specified,tobeearthedaresoearthedthroughoneormoreearth leakagecircuitbreakersorrelays.

EnclosedDistributionBoardAnenclosurecontainingbusbarswithoneormorecontrolandprotected devices for the purpose of protecting, controlling or connecting more than oneoutgoingcircuitsfedformoneormoreincomingcircuits.

ExposedMetalAllmetalpartsofaninstallationwhichareeasilyaccessibleotherthan:

(a) Partsseparatedfromlivepartsbydoubleinsulation;(b) Metalnameplates,screwheads,covers,orplates,whicharesupportedonorattached

orconnectedtosubstantialnonconductingmaterialonlyinsuchamannerthattheydonotbecomealive intheeventoffailureof insulationof livepartsandwhosemeansoffixingdonotcomeincontactwithanyinternalmetal;and

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(c) Partswhichare separated from livepartsbyothermetalpartswhichare themselvesearthedorhavedoubleinsulation.

Fire Survival Cable A cablewhich continues in service after exposure to a temperature of9000Cfor20minor7000for90min.

Fitting, lighting A device for supporting or containing a lamp or lamps (for example,fluorescent or incandescent) together with any holder, shade, or reflector, for example, abracket,apendantwithceilingrose,anelectrolier,oraportableunit.

Flameproof Enclosure An enclosure which will withstand without injury any explosion ofinflammable gas thatmay occurwithin it under practical conditions of operationwithin theratingoftheapparatus(andrecognizedoverloads,ifany,associatedtherewith)andwillpreventthe transmissionof flamewhichmay ignite any inflammable gas thatmaybepresent in thesurroundingatmosphere.

Notes

1. Hazardousareasareclassified intodifferentzones,dependingupon theextent towhichanexplosiveatmospherecouldexistatthatplace.Insuchareasflameproofswitchgear,fittings,accessories,havetobeused/installedinflameproofenclosure.

2. Anelectricalapparatus isnotconsideredasflameproofunless itcomplieswiththeappropriatestatutoryregulations.

3. Other types of fittings are also in vogue in wiring installations, for example,increasedsafety.

FlameRetardantCableFlameretardantcablewithreducedhalogenevaluationandsmoke.

FuseAdevice that,by the fusionofoneormoreof itsspeciallydesignedandproportionedcomponents,opens the circuit inwhich it is insertedwhen the current through it exceeds agivenvalueforasufficienttime.Thefusecomprisesallthepartsthatformthecompletedevice.

FuseElementApartofthefuselinkdesignedtomeltundertheactionofcurrentexceedingsomedefinitevalueforadefiniteperiodoftime.

Harmonics(CurrentandVoltage)Allalternatingcurrentwhich isnotabsolutelysinusoidal ismadeupofafundamentalandacertainnumberofcurrentharmonicswhicharethecauseofitsdeformation(distortion)whencomparedtothetheoreticalsinewave.

InflammableAmaterialcapableofbeingeasilyignited.

Installation(Electrical),ofBuildingsAnassemblyofassociatedelectricalequipmenttofulfilaspecificpurposeorpurposesandhavingcoordinatedcharacteristics.

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Insulated Insulated shallmean separated from adjacent conductingmaterial or protectedfrompersonal contactbyanonconducting substanceoranair space, ineither caseofferingpermanentlysufficientresistancetothepassageofcurrentortodisruptivedischargesthroughoroverthesurfaceofthesubstanceorspace,toobviatedangerorshockorinjuriousleakageofcurrent.

Insulation,Basic Insulationapplied to liveparts toprovidebasicprotectionagainstelectricshock.

Note Basic insulation does not necessarily include insulation used exclusively forfunctionalpurposes.

Insulation,DoubleInsulationcomprisingbothbasicandsupplementaryinsulation.

Insulation(Electrical)Suitablenonconductingmaterial,enclosing,surroundingorsupportingasconductor.

Insulation, Reinforced Single insulation applied to live parts, which provides a degree ofprotectionagainstelectricshockequivalenttodoubleinsulationundertheconditionsspecifiedintherelevantstandard.

Note The term single insulation does not imply that the insulationmust be onehomogeneouspiece. Itmaycompriseseverallayerswhichcannotbetestedsinglyassupplementaryorbasicinsulation.

Insulation, Supplementary Independent insulationapplied in addition tobasic insulation inothertoprovideprotectionagainstelectricshockintheeventofafailureofbasicinsulation.

Linked Switch Switches linked togethermechanically so as tooperate simultaneouslyor indefinitesequence.

LiveorAliveElectricallychargedsoastohaveapotentialdifferentfromthatofearth.

Locations,IndustrialLocationswheretoolsmachineryrequiringelectricalwiringare installedormanufactureorrepair.

Locations, NonIndustrial Locations other than industrial locations, and shall includeresidences,offices,shops,showrooms,storesandsimilarpremisesrequiringelectricalwiringforlighting,orsimilarpurposes.

Miniature Circuit Breaker Mechanical switching device capable of making, carrying andbreaking currents under normal circuit conditions and also making carrying currents forspecifiedtimesandautomaticallybreakingcurrentsunderspecifiedabnormalcircuitconditionssuchasthoseofoverloadandshortcircuits.

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MultipleEarthedNeutralSystemA systemofearthing inwhich thepartsofan installationspecified to be earthed are connected to the general mass of earth and, in addition, areconnectedwithintheinstallationtotheneutralconductorofthesupplysystem.

Neutral Conductor Includes the neutral conductor of a threephase fourwire system, theconductorofa singlephaseordc installationwhich isearthedby the supplyundertaking (orotherwiseatthesourceofthesupply),andthemiddlewireorcommonreturnconductorofathreewiredcorsinglephaseacsystem.

PlugAdevice,providedwithcontactpins,whichisintendedtobeattachedtoaflexiblecable,andwhichcanbeengagedwithasocketoutletorwithaconnector.

Point (inWiring) A terminationof the fixedwiring intended for the connectionof currentusingequipment.

Residual Current CircuitBreaker Amechanical switching device design tomake, carry andbreakcurrentsundernormalserviceconditionsandtocausetheopeningofthecontactswhentheresidualcurrentsattainsagivingvalueunderspecifiedconditions.

ServiceTheconductorsandequipmentrequiredfordeliveringenergyfromtheelectricsupplysystemtothewiringsystemofthepremisesserved.

SocketOutletAccessoryhavingsocketcontactsdesignedtoengagedwith thepinsofaplugandhavingterminalsfortheconnectionofcable(s).

NoteAluminairetracksystemisnotregardedasasocketoutletsystem.

SwitchAmechanicalswitchingdevicecapableofmaking,carryingandbreakingcurrentundernormalcircuitconditions,whichmay includespecifiedoperatingoverloadconditions,andalsoof carrying for a specified time currents under specified abnormal circuit conditions such asthoseofshortcircuit.

Note A switch may also be capable of making, but not breaking, shortcircuitcurrents.

SwitchboardAnassemblyofswitchgearwithorwithout instruments,butthetermdoesnotapplytoagroupoflocalswitchesinafinalcircuit.

NoteThetermswitchboardincludesadistributionboard.

SwitchDisconnectorsAdeviceusedtopen(orclose)acircuitwheneithernegligiblecurrentisinterrupted(orestablished)orwhenthesignificantchangeinthevoltageacrosstheterminalsofeach of the pole of the disconnectors occurs; in the open position it provides an isolatingdistancebetweentheterminalsofeachpole.

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SwitchDisconnectorFuseAcompositeunit,comprisingaswitchwiththefusecontainedinormountedonthemovingmemberoftheswitch.

SwitchgearAgeneraltermcoveringswitchingdevicesandtheircombinationwithassociatedcontrol,measuring,protectiveand regulatingequipment,alsoassembliesof suchdevicesandequipmentwithassociatedinterconnections,accessories,enclosuresandsupportingstructures,intended in principle for use in connection with generation, transmission, distribution andconversionofelectricenergy.

UsableWall spaceAportionsofawall,except thatoccupiedbyadoor in itsnormalopenposition,oroccupiedbyafireplaceopening,butexcludingwallspaceswhicharelessthan1minextentmeasuredalongthewallatthefloorline.

Voltage,ExtraLow(ELV)Thevoltagewhichdoesnotnormallyexceed50V.

Voltage,Low(LV)Thevoltagewhichnormallyexceed50Vbutdoesnotnormallyexceed250V.

Voltage,Medium(MV)Thevoltagewhichnormallyexceeds250Vbutdoesnotexceed650V.

Voltage,High(HT,HV)Thevoltagewhichnormallyexceeds650Vbutlessthanorequalto33kV.

Voltage,ExtraHigh(EHT)Thevoltage,whichnormallyexceeds33kV.

WeatherproofAccessories,lightingfittings,currentusingappliancesandcablesaresaidtobeoftheweatherprooftype,iftheyaresoconstructedthatwheninstalledinopensituationtheywillwithstandtheeffectsofrain,dustandtemperaturevariations.

Fordefinitionofothertermsreferencemaybemadetoacceptedstandards[82(1)].

9.2.2.2 ConventionalSymbols

The architectural symbols that are tobe used in all drawings,wiring plans, etc for electricalinstallationsinbuildingsshallbeasgiveninAnnexA.

Forothergraphicalsymbolsusedinelectrotechnology,referencemaybemadetogoodpractice.

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9.2.3GENERALREQUIREMENTS

9.2.3.1 ConformitywithElectricityAct,2003andrulesamendeduptodate

The installation shall generally be carried out in conformity with the requirements of TheElectricityAct,2003.

9.2.3.2 Materials

Allmaterials,fittings,appliances,etc.usedinelectricalandalliedinstallations,shallconformtoPart7buildingandotherstandards.

9.2.3.3 CoordinationwithLocalSupplyAuthority

a) In all cases, that is, whether the proposed electrical work is a new installation orextensionofanexistingone,oramodification involvingmajorchanges,theelectricitysupplyundertakingshallbeconsultedaboutthefeasibility,etc.atanearlydate.

b) Additiontoan InstallationAnaddition,temporaryorpermanent,shallnotbemadetotheauthorizedloadofanexistinginstallation,untilithasbeendefinitelyascertainedthatthecurrentcarryingcapacityandtheconditionofexistingaccessories,conductors,switches, etc. affected, including those of the supply authority are adequate for theincreasedload.Thesizeofthecable/conductorshallbesuitablyselectedonthebasisoftheratingsoftheprotectivedevices.Ratingsofprotectivedevicesandtheirtypesshallbebasedontheinstalledload,switchingcharacteristicsandpowerfactor.

Load assessment and applicationof suitablediversity factor toestimate the full load currentshallbemadeasafirststep.Thisshouldbedoneforeverycircuit,submainandfeeder.Powerfactorandefficiencyofloadsshallalsobeconsidered.Diversityfactorassumedshallbebasedononesownexperience.. Allowanceshouldbemadeforabout15percentto20percentforextension innearfutureandthedesigncircuit iscalculatedforeachcircuitandsubmain. Thewiring system to be adopted should also be decided in accordancewith the environmentalrequirements.Thesizesofwiringcablesaredecidednotmerelytocarrytheloadcurrents,butalso towithstand thermal effectsof likelyover currents and also ensure acceptance levelofvoltagedrop.

9.2.3.4 PowerFactorImprovementinConsumersInstallation

9.2.3.4.1 Conditions of supply of electricity boards or licensees stipulate the lowerlimit ofpowerfactorwhichisgenerally0.85.

9.2.3.4.2 Principal causes of low power factor aremany. For guidance to the consumers ofelectricenergywhotakesupplyatlowandmediumvoltagesforimprovementofpowerfactor,referenceshallbemadeinaccordancewithgoodpractice.

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9.2.3.5 ExecutionofWork

Unless otherwise exempted under the appropriate rule of the Electricity Company ofGhanaworkofelectricalinstallationsshallbecarriedoutbyalicensedelectricalcontractorandunderthedirectsupervisionofapersonholdingacertificateofcompetencyandbypersonsholdingavalidpermitissuedandrecognizedbyanyStategovernment.

9.2.3.6 Safety procedures and practices shall be kept in view during execution of the work inaccordancewithgoodpractice.

9.2.4 PLANNINGOFELECTRICALINSTALLATIONS

9.2.4.1 General

Thedesignandplanningofanelectricalwiringinstallationinvolveconsiderationofallprevailingconditions, and is usually influenced by the type and requirement of the consumer. Acompetentelectricaldesignengineer shouldbe involvedat theplanning stagewithaview toproviding for an installation thatwillprove adequate for its intendedpurpose, and safe andefficientinitsuse.Theinformationgivenin3shallalsobekeptinview.

9.2.4.1.1Thedesignandplanningofanelectricalwiringinstallationshalltakeintoconsideration,someorallofthefollowing:

a) thetypeofsupply,occupancy,envisagedloadandtheearthingarrangementavailable;

b) the atmospheric condition, such as cooling air temperature,moisture or such otherconditionswhicharelikelytoaffecttheinstallationadversely;

c) thepossiblepresenceofinflammableorexplosivedust,vapourorgas;

d) thedegreeofelectricalandmechanicalprotectionnecessary;

e) theimportanceofcontinuityofserviceincludingthepossibleneedforstandysupply;

f) theprobabilityofneedformodificationorfutureextension;

g) theprobableoperationandmaintenancecosttakingintoaccounttheelectricitysupplytariffsavailable;

h) therelativesotofvariousalternativemethods;

j) theneedforradioandtelecommunicationinterferencesuppression;

k) caseofmaintenance;

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m) safetyaspects;

n) energyconservation;and

p) the importanceofproperdiscriminationbetweenprotectivedevices for continuityofsupplyandlimitedisolationofonlytheaffectedportion.

9.2.4.1.2Allelectricalapparatusshallbesuitablefortheservicestheseareintendedfor:

9.2.4.1.3Coordination

Propercoordinationandcollaborationbetween thearchitect,civilengineerandtheelectricalandmechanical engineer shall be effected from the planning stage of the installation. Theprovisionsthatwillbeneededfortheaccommodationofsubstation,transformer,switchrooms,servicecableducts,risingmainsanddistributioncables,subdistributionboards,openingsandchases in floors and walls for all required electrical installations, etc. shall be specified inadvance.

9.2.4.1.4 Before starting wiring and installation of fittings and accessories, information should beexchanged between the owner of the building/architect/electrical contractor and the localsupplyauthorityinrespectoftariffsapplicable,typesofapparatusthatmaybeconnectedundereach tariff, requirement of space for installing meters, switches, etc. and for total loadrequirementsoflights,fansandpower.

9.2.4.1.5Whileplanninganinstallation,considerationshouldbetakenoftheanticipatedincreaseintheuseofelectricityforlighting,generalpurposesocketoutlet,kitchenhearting,etc.

Itisessentialthatadequateprovisionshouldbemadeforalltheserviceswhichmayberequiredimmediately and during the intended useful life of the building, for the householder mayotherwisebetemptedtocarryoutextensionofthe installationhimselfortorelyuponuseofmultiplugadoptersandlongflexiblecords,bothofwhicharenotrecommended.

9.2.4.2 LocationandRequirementofSubstation

Informationonlocationandrequirementsofasubstationshouldcoverthefollowing:

9.2.4.2.1Location

a) Thesubstationshouldpreferablybelocatedinseparatebuildingandcouldbeadjacenttothegeneratorroom.Ifany.Locationofsubstationinthebasementfloorsshouldbeavoided,asfaraspossible.

b) The ideal location foranelectricalsubstation foragroupofbuildingswouldbeat theelectricalloadcentreonthegroundfloor.

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c) Thefloorlevelofthesubstationorswitchroomshallbeabovethehighestfloodlevelofthelocality.

d) Generallytheloadcentrewouldbesomewherebetweenthegeometricalcentreandtheair conditioning plant room, as air conditioning plant room would normally be thelargestchunkofload,ifthebuildingisairconditioned.

e) Substations with oil filled equipment will require great consideration for the firedetection,protectionandsuppression. Oilcooledtransformersrequireasuitablesoakpitwithgravityflowtocontaintheoilintheeventofthepossibilityofoilspillagefromthetransformeronitsfailure.Substationswithoilfilledequipmentshallnotbelocatedinanyfloorotherthanthegroundfloororasemibasement.Suchsubstationswithhighoilcontentmaybehousedinaseparateservicebuildingorasubstationbuilding,whichisnotthepartofamultistoreyedbuilding.

f) In case electric substation has to be locatedwithin themainmultistoreyed buildingitself forunavoidable reasons, then it shouldbe locatedon the floor close togroundlevel,butshallhavedirectaccessfromthestreetforoperationoftheequipments.Theprovisionfor installationandremovalofsubstationequipmentsmaybeprovidedfrominsidethebuilding.

g) Substations located within a multistoreyed building shall not have oil filedtransformers,even if it isattheground level. Substationswithvery littlecombustiblematerial,suchasadrytypetransformer,withVacuum(orSF6)HTswitchgearandACBorMCCBforMVcanbelocatedinthebasementaswellasupperfloorsinabuildingwithhigh loaddensity intheupperfloors. (Somefunctionalbuildingssuchashospitals,airtrafficcontroltowers,computercentresare likelytohavehigh loading inafewupperfloorsand insuchcases, itmaybepreferable toprovideoilfreesubstationsatupperlevels. This measure will decrease the current flow at various points, therebycontributingtoreductionofvulnerabilitytofire).

h) Thepowersupplycontrol toanysuchsubstationor transformer (locatedatbasementlevels or upper floors) shall be from a location on ground floor/first basement levelhavingdirectaccess fromoutside so that in caseof fire, theelectricity supply canbeeasilydisconnected.

j) Oilfilledtransformersmaybeusedonlyinsubstationslocatedinseparatesingleortwostoreyedservicebuildingsoutsidethemainbuildingstructureandthereshallatleast6meter clear distance between the adjoining buildings and substation such that firetenderisabletopassbetweenthetwostructures.

k) If dry type transformer is used, it may be located adjacent to medium voltageswitchgearintheformofunittypesubstation.Noseparateroomorfirebarrierforthe

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transformer is required, in a substationwith oil free equipment. In such a case theroomsizewilldecrease.Layoutofequipmenthastokeeptherequirementthatanyonepieceofequipmentorsubassemblycanbetakenoutofserviceandoutoftheinstalledlocation,whilekeepingtheremainingsysteminservice.

m) The emergency power supply (such as generating sets) should not be allowed to beinstalledaboveground floororbelow firstbasement levelofbuilding. Thereshallbeprovisionofseparatedirectescapeandentry into theseareas fromoutsideso that incaseoffire,electricalsuppliescanbedisconnectedtoavoidadditionalloseswhichmaybecausedduetoelectricalsupply,presentatthetimeoffire.

n) For transformers having large oil content (more than 2,000 litres). Rules of theElectricityCompanyofGhana(ECG)asamendedfromtimetotimeshallapply.

p) Facility for connections from substation to adjoining building to feed essentialemergency load inthatbuilding,suchasescaperoute lighting,fireorsprinklerpumps,emergency communication systems shall be provided. Similarly, the essentialemergency loadswitchboardofthisbuildingorbuildingcomplexshouldbesoastobecapableofreceivingpowerforsuchloadsfromtheadjoinbuildingorbuildingcomplex,withadjoiningbuildingorbuilding complex,with itsown substation/DG sets shutoffduetocrisisconditionssuchasfire.

q) The availability of power lines nearbymay also be kept in view while deciding thelocationofthesubstation.

r) Fordetailed informationregarding locationoftransformersreferencemaybemadetogoodpractice,

s) Alldooropeningsfromsubstation,electricalrooms,etc.shouldopentowardsoutside.

t) For acoustical enclosures/treatment reference may be made to Part 9.4:BuildingServicesAcoustics,SoundInsulationandNoiseControl.

9.2.4.2.2Typeofbuildingforsubstations

Thesubstationsenclosurethat is,walls,floor,ceiling,openings,doors,etc.shallhavea2hourfirerating.

9.2.4.2.3Layoutofsubstation

In allocating the areaof substation, it is tobenoted that the flowof electricpower is fromsupply companys room toHV room, then to transformer and finally to themedium voltageswitchgearroom.Thelayoutoftheroomshallbeinaccordancewiththisflow,soastooptimizethecables,bustrunkingetc.Visibilityofequipmentcontrolledfromtheoperatingpointofthe

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controlling switchgear isalsoadesirable feature, though itmaynotbeachievable in caseoflargesubstations.

9.2.4.2.4Room/spacesrequired

Generallythefollowingrooms/spacesarerequiredinasubstation:

a) Supplycompanysswitchgearfromand/orspaceformeters.

b) CapacityandSizeThecapacityofasubstationdependsupontheareaofthebuildingandits type. The capacity of substation may be determined based on the following loadrequirements.

TableoftypicalAllowancesforDiversity

Purposeoffinalcircuitfedfromconductorsorswitchgeartowhichdiversityapplies

Individualhouseholdinstallations,includingindividualdwellingof

aBlock

Typeofpremises

small,shops,storesofficesandbusiness

Typeofpremisessmallhotels,boardinghouses,

etc.

Lighting 66%oftotaldemand90%oftotalcurrentdemand

75%oftotalcurrentdemand

Heatingandpower

80%oftotalcurrentdemandupto10A+40%ofanycurrentdemandinexcessof10A

80%fullloadoflargestappliance+60%ofremainingappliances

80%fullloadoflargestappliance+60%ofsecondlargestappliances+40%ofremainingappliances

Cookingappliances

10A+30%fullloadofconnectedcookingappliancesinexcessof10A+5Aifsocketoutletincorporatedinunit.

80%fullloadoflargestappliance+60%fullloadofsecondlargestappliance+50%fullloadofremainingappliances

80%oflargestappliance+60%offullloadofsecondlargestappliance+50%fullloadofremainingappliances

Motor(otherthanliftmotorswhicharesubjecttospecialconsideration)

80%fullloadoflargestmotor+60%fullloadofsecondlargestmotor+50%fullloadofremainingmotors

80%fullloadoflargestmotor+50%fullloadofremainingmotors

Waterheater 80%fullloadoflargest 80%fullloadof 80%fullloadoflargest

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appliance+50%ofsecondlargestappliance+25%fullloadofremainingappliances

largestappliance+60%ofsecondlargestappliance+25%fullloadofremainingappliances

appliance+60%ofsecondlargestappliance+25%fullloadofremainingappliances

Floorwarminginstallations 50%

Waterheatersthermalstoragespaceheatinginstallations

50%

Table(contd.)

(1) (2) (3) (4)

StandardarrangementsoffinalcircuitsinaccordancewithIS732

80%ofcurrentdemandoflargestcircuit+40%ofcurrentdemandofeveryothercircuit

80%ofcurrentdemandoflargestcircuit+50%ofcurrentdemandofeveryothercircuit

Socketoutletsotherthanthoseincludedaboveandstationaryequipmentotherthanthoselistedabove

80%ofcurrentdemandoflargestpointof+40%ofcurrentdemandofeveryotherpointof.

80%ofcurrentdemandoflargestpointof+60%ofcurrentdemandofeveryotherpointof.

80%ofcurrentdemandoflargestpointof+60%ofcurrentdemandofeverypointinmainrooms(diningrooms,etc)+40%ofcurrentdemandofeveryotherpointof.

Notes

1. Forthepurposeofthetableaninstantaneouswaterheaterisdeemedtobeawaterheaterofanyloadingwhichheatswateronlywhilethetapisturnedonandthereforeuseselectricityintermittently.

2. It is important to ensure that the distribution boards are of sufficient rating to take the total loadconnectedtothemwithouttheapplicationofanydiversity.

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After calculating the electrical load on the above basis, a load factor of 7090 percent is to beapplied to arrive at theminimum capacity of substation. The area required for substation andtransformerroomfordifferentcapacitiesisgiveninAnnexCforgeneralguidance.Forreliability,itwouldbenecessarytosplitthe load intomorethanonetransformerandalsoprovideforstandbytransformeraswellasmultiplesources,bussection,etc.

c) HighVoltageSwitchRoomIncaseofsubstationhavingonetransformerandonesourceofsupply, theowner is required toprovideonehighvoltage switch. Incaseof singlepointsupply with two or more transformers the number of switch required will be one forincoming supply and one for each transformer. In case of duplicate supply two switchesshall be providedwithmechanical/electrical in locking arrangementwhere necessary incableswithswitches. Incase thenumberof incomingandoutgoingswitchesexceed five,buscouplerofsuitablecapacityshould invariablybeprovided. The floorarea required incaseofasingleswitchisroughly4mx4mandforeveryadditionalswitchthelengthwouldbeincreasedby1m.

d) Facilityforconnectionfromsubstationofadjoiningbuildingto feedemergency loadsshallbepermittedforfeedingescaperouteandsignagelightingaswellasselectedsectionofthefireprotectionsystem. Similarlyonareciprocalbasisfacilitytofeedtheadjoiningbuildingforsuchemergencyloadsmaybeprovidedbynecessaryswitchgear.

e) Medium Voltage Switch Room The floor area required in respect ofmedium voltageswitchgear room may be determined keeping in view the number and type ofincoming/outgoingbuscouplerswitchesincludinglikelyexpansioninfuture.

f) Room for StandbyGenerator It ispreferable to install the standbygenerator in service

building.Ifinstalledinmainbuildingitshallbeatthegroundfloororatthesemibasement,alternatively, in the first basementwith facilities for forced ventilation. Adequate spaceshallbeprovidedforstoringoffuel. Compartmentationforfireprotectionwithdetectionandfirstaidprotectionmeasures isessential. Differenttypeofrequirementsexistforthedieselengineandgeneratorfortheoilstorageareaandfortheswitchgear.

g) Facilities including spaceatappropriatepositions, relative to the locationof the installed

equipmenthastobekeptinthelayoutdesignforremovalofequipmentorsubassembliesfor repair ormaintenance. When it is located, other than the ground levelwith directequipmentaccess,ahatchorrampshallberequired.

h) Otherenvironmental requirementsunder theprovisionsofEnvironmentProtectionRules,

1986 as amended timetotime shall be taken into account form the aspect of engineemissions including regarding theheightofexhaustpipeandpermittednoise levels/noisecontrol.

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j) Thecapacityofstandbygeneratingsetshallbechosenonthebasisofessential light load,essentialairconditioningload,essentialequipmentloadandessentialservicesload,suchasoneliftoutofthebankoflifts,oneorallwaterpumps,etc.Havingchosenthecapacityandnumberofgeneratingsets,requiredspacemaybeprovidedfortheirinstallation(SeeAnnexDforgeneralguidance).

k) ThegeneratingsetshouldpreferablybehousedadjacenttoMVswitchgearinthesubstationbuildingtoenabletransferofelectricalloadquicklyaswellastoavoidtransferofvibrationand noise to themain building. Acoustics lining of the room shall be in line with therequirementsofcentralPollutionControlBoard(CPCB).IfDGSetislocatedoutdoor,itshallbehousedinacousticsenclosure.Thegeneratorhouseshouldhaveproperventilation,firefightingequipment,etc.(Seealso4.2.2).

l)Requirementsofroom

1) Theareasgivenaboveinrespectofthedifferentcategoriesofroomsholdsgoodiftheyareprovidedwithwindowsandindependentaccessdoorsinaccordancewithlocalregulations.

2) Alltheroomsshallbeprovidedwithpartitionsuptotheceilingandshallhaveproper ventilation. Special care shouldbe taken to ventilate the transformerroomsandwherenecessary louversat lower levelandexhaust fansathigherlevelshallbeprovidedatsuitablelocations.

3) In order to prevent stormwater entering the transformer and switch roomsthrough the soakpits, the floor level, the substation shall be at least 15 cmabovethehighestfloodwaterlevelthatmaybeanticipatedinthelocality.Also,facilityshallbeprovidedforautomaticremovalofwater.

4) Theminimumheightofhighvoltageswitchgearroomshallbe3.6mbelowthesoffitofthebeam.

m)Firecompartmentation It isadvisabletoprovide firecompartmentationofbuildingsandsegregationofassociatedwiring.Busbartrunkingofhorizontalandverticaldistributiontypeinplaceofcablebaseddistributionsystemshallbeused.

9.2.4.3 Locationofswitchroom

Inlargeinstallationsotherthanwhereasubstationisprovided,aseparateswitchroomshallbeprovided;thisshallbelocatedascloselyaspossibletotheelectricalloadcentrepreferablyneartheentranceof thebuildingon theground floororon the firstbasement level,and suitableductsshallbelaidwithminimumnumberofbendsfromthepointsofentryofthemainsupply

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cable to thepositionof themainswitchgear. The switch room shallalsobeplaced insuchapositionthatrisingductsmayreadilybeprovidedtherefromtotheupperfloorsofthebuildinginonestraightverticalrun.Inlargerbuildings,morethanonerisingductmayberequiredandthenhorizontalductsmayalsoberequiredforrunningcablesfromtheswitchroomtothefootofeachrisingmain.Suchcableductsshallbeeitherbereservedfortheelectricalservicesonlyorprovidedwithameansofsegregationformediumandlowvoltageinstallations,suchascallbellsystems;telephoneinstallations,firedetectionandalarmsystem,announcementorpublicaddresssystem.Cablesforessentialemergencyservicessuchasthoserelatedtofiredetection,alarm,announcementshoulduseeithermetalconduitinadditiontophysicalsegregationroompowercablesorusefiresurvivalcables,sothattheserviceismaintainedevenintheeventofafireatleastforaperiodofabout20min.

9.2.4.4 Locationandrequirementsofdistributionpanels

Theelectricalcontrolgeardistributionpanelsandotherapparatus,whicharerequiredoneachfloormayconvenientlybemountedadjacenttotherisingmains,andadequatespaceshouldbeprovidedateachfloorforthispurpose.

9.2.4.5 Substationsafety

Theowneror theoperatorofanysubstationshallbecollectivelyandseverallyberesponsibleforanylapseorneglectleadingtoanaccidentoranincidenceofanavoidableabnormalityandshalltakecareofthesafetyrequirementsasfollows:

a) Enclose the substations where necessary to prevent, so far as is reasonablypracticable,dangerorunauthorizedaccess;

b) Enclose any part of the substation, which is open to the air and contains liveequipmentwhichisnotencased,withafenceorwallnotlessthan2.4minheighttoprevent,sofarasisreasonablypracticable,dangerorunauthorizedaccess;

c) Ensurethat,sofarasisreasonablypracticable,thereareatalltimesdisplayed:1) Sufficientsafetysignsofsuchsizeandplacedinsuchpositionsasarenecessary

to give due warning of such danger as is reasonably foreseeable in thecircumstances;

2) Anoticewhichisplacedinaconspicuouspositionandwhichgivesthelocationor identificationof the substation, thenameofeach generatorordistributorwhoownsoroperatesthesubstationequipmentmakingupthesubstationandthe telephone number where a suitably qualified person appointed for thispurposebythegeneratorordistributorwillbeinconstantattendance;and

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3) Such other signs,which are of such size and placed in such positions, as arenecessary to give duewarning of danger having regard to the siting of, thenature of, and the measures taken to ensure the physical security of, thesubstationequipment;and

d) Take all reasonable precautions tominimize the risk of fire associatedwith the

equipment.

9.2.4.6 Overheadlines,wiresandcables

9.2.4.6.1Heightrequirement

Whileoverheadlinesmaynotberelevantwithinbuildings,regulationsrelatedtooverheadlinesareofconcernfromtwodifferentangles.

a) Overheadliensmayberequiredinbuildingcomplexes,thoughuseofundergroundcablesisthepreferredalternative.

b) Overhead linesmaybepassing through the siteofabuilding. In suchacase thesafety aspects are important for the construction activity in the vicinity of theoverhead line as well as portions of low height buildings that may have to beconstructedbelowtheoverheadlines.

Forminimumdistance (verticalandhorizontal)ofelectric liens/wires/cables frombuildings,referencemaybemadetoPart3DevelopmentControlRulesandGeneralRequirements.

c) Any person responsible for erecting an overhead line will keep informed theauthority(s) responsible for services in that area for telecommunication, gasdistribution,waterandseweragenetwork,roadssoastohavepropercoordinationtoensure safety. He shallalsopublish the testing,energizingprogramme for thelineintheinterestsofsafety.

9.2.4.6.2Position,insulationandprotectionofoverheadlines

Any part of an overhead linewhich is not connectedwith earth andwhich is not ordinarilyaccessibleshallbesupportedoninsulatorsorsurroundedbyinsulation.

Any part of an overhead line which is not connected with earth and which is ordinarilyaccessibleshallbe:

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a) Madedead;orb) So insulated that it is protected, so far it is reasonably practicable, against

mechanicaldamageorinterference;orc) Adequatelyprotectedtopreventdanger.

Any person responsible for erecting a building or structurewhichwill cause any part of anoverhead linewhich is not connectedwith earth to become ordinarily accessible shall givereasonablenoticetothegeneratorordistributorwhoownsoroperatestheoverheadlineofhisintentiontoerectthatbuildingorstructure.

Anybareconductornotconnectedwithearth,whichispartofalowvoltageoverheadline,shallbesituatedthroughoutitslengthdirectlyaboveabareconductorwhichisconnectedwithearth.

Nooverheadlineshall,sofarasisreasonablypracticable,comesoclosetoanybuilding,treeorstructureastocausedanger.

In this regulation the expression ordinarily accessible means the overhead line could bereachedbyhand ifanyscaffolding, ladderorotherconstructionwaserectedorplacedon/in,againstorneartoabuildingorstructure.

9.2.4.6.3Precautionsagainstaccessandwarningsofdangers

Every support carrying a high voltage overhead line shall, if the circumstances reasonablyrequire,befittedwithdevicestoprevent,sofar it isreasonablypracticable,anyunauthorizedpersonfromreachingapositionatwhichanysuchlinewouldbeasourceofdanger.

Everysupportcarryingahighvoltageoverhead line,andeverysupportcarryinga lowvoltageline incorporatingbarephase conductors, shallhaveattached to it sufficient safety signsandplaced insuchpositionsasarenecessary togiveduewarningofsuchdangeras isreasonablyforeseeableinthecircumstances.

Poles supportingoverhead linesnear the road junctionsand turnings shallbeprotectedbyamasonryorearthfillstructureormetalbarricade,topreventavehiclefromdirectlyhittingthepole,so that thevehicle, ifoutofcontrol, is restrained fromcausing totaldamage to the liveconductorsystem,likelytoleadtoahazardousconditionontheroadorfootpathorbuilding.

9.2.4.6.4Fittingofinsulatorstostaywires

Every staywirewhich formspartof,or isattached to,any supportcarryinganoverhead lineincorporatingbarephaseconductors9exceptwhere the support isa lattice steel structureorother structureentirelyofmetaland connected toearth) shallbe fittedwithan insulatornopartofwhichshallbe lessthan3mabovegroundorabovethenormalheightofanysuch lineattachedtothatsupport.

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9.2.4.7 Mapsofundergroundnetworks

9.2.4.7.1Anypersonororganizationorauthority layingcablesshallcontactauthority inchargeofthatareaandfindoutthelayoutof:

a) waterdistributionpipelinesinthearea;

b) sewagedistributionnetwork;

c) telecommunicationnetwork,and

d) gas pipeline network and plan the cable network in such amanner that thesystem is compatible, safeandnon interferingeitherduring its installationorduring itsoperationandmaintenance. Planoftheproposedcable installationshallbebroughttothenoticeoftheotherauthoritiesreferredabove.

9.2.4.7.2Suitablecablemarkersanddangersignaswouldbeappropriateforthesafetyoftheworkmenofanyofthesystemsshallbeinstalledalongwiththecableinstallation.Notificationoftestingandenergizationofthesystemshallalsobesuitablypublishedforensuringsafety.

9.2.4.7.3 Any person or organization or authority laying cables shall have and, so far it isreasonablypracticable,keepup todate,amapor seriesofmaps indicating thepositionanddepthbelowsurfacelevelofallnetworksorpartsthereforwhichtheownsoroperates.

Anymappreparedorkeptshallbeavailable for inspectionbyanyof themunicipalauthority,otherserviceproviders,generalpublicprovidedtheyhaveareasonablecause forrequiringtoinspectanypartofthemap.

9.2.5 DISTRIBUTIONOFSUPPLYANDCABLING

9.2.5.0 General

Intheplanninganddesignofanelectricalwiringinstallation,dueconsiderationshallbemadeofalltheprevailingconditions.Itisrecommendedthatadviceofacompetentelectricalengineerbe sought at the initial stage itselfwith a view to providing an installation, thatwill proveadequateforitsintendedpurposebereliableandsafeandefficient.

Acertainredundancyintheelectricalsystemisnecessaryandhastobebuiltinfromtheinitialdesign stage itself. Theextentof redundancywilldependon the typeof load, its criticality,normalhoursofuse,qualityofpowersupplyinthatarea,coordinationwiththestandbypowersupply,capacitytomeetthestartingcurrentrequirementsoflargemotors,etc.

9.2.5.1 SystemofSupply

9.2.5.1.1Allelectricalapparatusshallbesuitableforthevoltageandfrequencyofsupply.

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9.2.5.1.2Incaseofconnectedloadof100kVAandabove,therelativeadvantageofhighvoltagethreephasesupplyshouldbeconsidered.Thoughtheuseofhighvoltagesupplyentailstheprovisionsof space for the capital cost of providing suitable transformer substation at the consumerspremises,thefollowingadvantagesaregained:

a) advantageintariff;

b) moreeffectiveearthfaultprotectionforheavycurrentcircuits;

c) eliminationofinterferencewithsuppliestootherconsumerspermittingtheuseoflargesizemotors,weldingplant,etc.,and

d) bettercontrolofvoltageregulationandmoreconstantsupplyvoltage.

NoteAdditionalsafetyprecautionsrequiredtobeobservedinHVinstallationsshallalsobekeptinview.

Inmanycasestheremaybenochoiceavailabletotheconsumer,asmostofthe licenseshaveformulatedtheirpolicyofcorrelatingthesupplyvoltagewiththeconnectedloadorthecontractdemand.Generallythesupplyisat400/230volts,11kV(or22kV)forloadsupto5MVAand33kVor66kVforconsumersofmorethan5MVA.

9.2.5.1.3 Invery large industrialbuildingswhereheavyelectricdemandsoccurat scattered locations,the economics of electrical distribution at high voltage from the main substation to othersubsidiary transformer substations or to certain items of plant, such as large motors andfurnaces, shouldbe considered. The relative economy attainablebyuseofmediumorhighvoltage distribution and high voltage plant is amatter for expert judgement and individualassessmentinthelightofexperiencebyaprofessionallyqualifiedelectricalengineer.

9.2.5.2 Substationequipmentandaccessories

Substations require an approval by the Electrical Inspectorate. Such approval ismandatorybefore energizing the substation. It is desirable to get the approval for the general layout,schematic layout,protectionplanetc.,beforethestartoftheworkfromthe Inspectorate. Allsubstation equipment and accessories and materials, etc, shall conform to relevant IndianStandardswherever theyexist,otherwise the consumer (orhisconsultant)has to specify thestandardstowhichtheequipmenttobesuppliedconfirmsandthatshallbeapprovedbytheauthority.Manufacturersofequipmenthavetofurnishcertificateofconformityaswellastypetestcertificatesforacceptancetestsandinstallationrelatedtestsforearthing,earthcontinuity,loadtestsandtestsforperformanceofprotectivegear.

9.2.5.2.1Highvoltageswitchgear

9.2.5.2.1.1Theselectionof the typeofhighvoltageswitchgear forany installation interaliadependsuponthefollowing:

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a) voltageofthesupplysystem

b) theprospectiveshortcircuitcurrentatthepointofsupply;

c) thesizeandlayoutofelectricalinstallation;

d) theaccommodationavailable;and

e) thenatureofindustry.

Making and breaking capacity of switchgear shall be commensurate with shortcircuitpotentialitiesofthesupplysystemandthesupplyauthorityshallbeconsultedonthissubject.

9.2.5.2.1.2 Guidelines on various types of switchgear equipment and their choice for a particularapplicationshallbeinaccordancewithgoodpractice.

9.2.5.2.1.3 In extensive installationsof switchgear (havingmore than four incoming supply cablesorhavingmorethan12circuitbreakers),banksofswitchgearsshallbesegregatedfromeachotherbymeansoffireresistingbarriershaving2hfireresistanceratinginordertopreventspreadingoftheriskofdamagebyfireorexplosionarisingfromswitchfailure. Whereabusbarsectionswitch is installed, it shallalsobe segregated fromadjoiningbanks in the sameway. Exceptmain LTpanel, itwouldbepreferable to locate the subpanels/distributionboardsnear loadcentre.Further,itshouldbeensuredthatthesepanelsareeasilyapproachable.Thepreferablelocationofpanelsshallbeneartheexitways.

9.2.5.2.1.4Itshouldbepossibletoisolateanysectionfromtherestoftheswitchboardssuchthatworkmightbe undertakenon this sectionwithout the necessityofmaking the switchboarddead.Isolatingswitchesusedfortheinterconnectionofsectionsorforthepurposeofisolatingcircuitbreakersofotherapparatus,shallalsobesegregatedwithinitscompartmentsothatnolivepartisaccessiblewhenworkinaneighbouringsectionisinprogress.

9.2.5.2.1.5Inthecaseofduplicateorringmainsupply,switchgearswithinterlockingarrangementshallbeprovidedwithinterlockingarrangementshallbeprovidedtopreventsimultaneousswitchingof two different supply sources. Electrical and/ormechanical interlocksmay preferably beprovided.

9.2.5.2.2Cables

9.2.5.2.2.1 The smallest sizeof the cable that shallbeused,willdependupon themethodof layingcable,permissiblemaximumtemperatureitshallwithstand,voltagedropoverthelengthofthecable, the prospective shortcircuit current to which the cable may be subjected, thecharacteristicsoftheoverloadprotectiongearinstalled,loadcycleandthermalresistivityofthesoil.

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9.2.5.2.2.2Theadviceofthecablemanufacturerwithregardtoinstallation,jointingandsealingshallbefollowed.

9.2.5.2.2.3 The HV cables shall either be laid on the cable rack/builtup concretetrenches/tunnel/basement or directly buried in the ground depending upon the specificrequirement.Itispreferabletousefourcorecableinplaceofthreeandhalfcoretominimizeheatingofneutral coredue toharmonic content in the supply systemandalsoavoidanceofoverloadfailures.Allcablesshallbeinstalledinaccordancewithgoodpractice.

9.2.5.2.2.4Colouridentificationofcoresofnonflexiblecables

FunctionColourIdentificationofcoreofrubberofpvc

insulatednonflexiblecable,orofsleeveordisctobeappliedtoconductororcablecode

Protectiveorearthing

Neutralofa.c.singleorthreephasecircuit

PhaseRof3phasea.c..circuit

PhaseYof3phasea.c.circuit

PhaseBof3phasea.c.circuit

Positiveofd.c.2wirecircuit

Outer (positiveornegative)ofd.c.2wirecircuitderivedfrom3wiresystemPositiveof3wire systempositiveof3wired.c.circuitMiddlewireof3wired.c.circuitNegativeof3wired.c.circuitFunctionalEarthTelecommunication

GreenandyelloworGreenwithyellowstripes1)

Red

Yellow

Blue

Red

Black

RedRedBlackBlueCream

1) Bareconductorsarealsousedforearthingandearthcontinuityconductors.But it ispreferabletouseinsulatedconductorswithgreeninsulationwithyellowstrips

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9.2.5.2.2.5Colour,identificationofcoresofflexiblecablesandflexiblecords

NumberofCores FunctionofCore Colour(s)ofCore1

2

3

4or5

PhaseNeutralProtectiveorEarthing

PhaseNeutral

PhaseNeutralProtectiveorEarthing

PhaseNeutralProtectiveorEarthing

Brown1)(Light)BlueGreen&yellow

Brown(Light)Blue1)

Brown(Light)Blue1)Green&yellow

BrownorBlack1)(Light)Blue1)Green&yellow

1Certainalternativesareallowedinwiringregulations

9.2.5.2.3Highvoltagebusbartrunking/ducting

Highvoltagebusbar trunkingsystem isa typetestedswitchgearandcontrolgearassembly inthe formofanenclosed system. HVbus system isused for transportingpowerbetweenHVGenerators,transformersandtheinfeedmainswitchgearofthemainHVswitchgear.

Generallythreetypesofbusductsnamelynonsegregated,segregatedand isolatedphasebusductshallbeused.Thenonsegregatedbusductsconsistsofthreephasebusbarsrunning inacommon enclosuremade of steel or aluminum. The enclosure shall provide safety for theoperational personnel and reduces chances of faults. The enclosures shall be effectivelygrounded.

Segregated phase bus duct are similar to nonsegregated phase duct except that metal orinsolationbarriersareprovidedbetweenphaseconductorstoreducechancesofphasetophasefaults.However,itispreferabletousemetalbarriers.

In the case of isolated bus ducts, each phase conductor shall be housed in separate nonmagneticenclosures.Thebusductshallbemadeofsectionswhichareassembledtogetheratsite tomakecompleteassembly.Theenclosure shallbeofeither roundor square shapeandwelded construction. Theenclosuresofallphases ingeneral tobe supportedona commonsteelstructure.ProvisionoffireprotectionshallbeprovidedinallopeningsinaccordancewithPart2UseandOccupancy.Fireseparationinopeningsshallbeprovidedusingmaterialshaving2hfireresistancerating.

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9.2.5.2.4MV/LVbusbartrunking/risingmains

Whereheavy loadsaretobecarried,busbarsystemsarepreferred. Thebusbarsareavailablefor continuous run frompoint topointorwith tapoffsat standard intervalsandhave tobechosenasperspecificrequirement. MV/LVbusbartrunkingshallbeatypetestedswitchgearandcontrolgearassemblyintheformofanenclosedsystem.TherearetwotypesofMV/LVbusductsystemforpowerdistributionsystem:

a) conventionaltypeb) compactandsandwichtype.

Conventionaltypebusductisusedforlargepowerhandlingbetweentransformerandswitchgerorbetweenswitchgearandlargepowerloads,suchascompressordrivemotoretc.Thistypeisgenerallyusedinplantrooms,risershafts,substationsetc.

Compact type is available either air insulated or sandwich type for usewithin areas of thebuildingwhich are put to other higher (aesthetic) level of use. They could be used in falseceilingspacesoreven incorridorsandshafts fordistributionwithoutany falseceilingas theyprovideanaestheticallyacceptablefinishtomergewithotherbuildingelementssuchasbeams,ductsorpipesinfunctionalbuildings.

The class of protection shall be specific depending on the requirement at the place ofinstallation. Protection class (IPxx)will automatically identify the ventilation,protection fromweather,water,dust,etc.

Inmodernbuildingtechnology,highdemandsaremadeofthepowerdistributionsystemanditsindividualcomponents:

a) Longlifeandgoodservicequality,b) Safeprotectionintheeventoffire,c) Lowfireload,d) Lowspacerequirement,ande) Minimumeffortinvolvedincarryingoutretrofits.

Thehigh loaddensity inmodern largebuildingsandhighrisebuildingsdemandscompactandsafe solution for the supply of power. The use of busbar trunking system is ideal for suchapplications.

Bas bar trunking can be installed in vertical risers ducts or horizontally in passages fortransmissionanddistributionofpower.Busbartrunkingsystemsallowelectricalinstallationstobeplannedinasimpleandclearfashion.Inthebuildingcomplexes,additionalsafetydemandswithrespecttofirebarriersandfireloadanduseofbusbartrunkingmeetsthisrequirement.

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Busbar trunking system reduces the combustiblematerial near the areawith high energy incomparisonwithotherdistributionsystemssuchascablesandmakesthebuildingsafefromtheaspectofvulnerabilitytofireofelectricalorigin.Inaddition,unlikecablesystemsthereliabilityof a bus trunking system is very high. These systems also require very little periodicmaintenance.

Choiceofbusbartrunkingfordistributioninbuildingscanbemadeonthebasisof:

a) Reducedfireload(drasticallyreducedincomparisontothecablesystem).b) Reducedmaintenanceoveritsentirelifetime.c) Longerservicelifetimeincomparisonwithacabledistribution.d) Enhanced reliabilitydue to rigidbolted jointsand terminationsandextremely low

possibilityofinsulationfailure.

9.2.5.2.5Transformers

9.2.5.2.5.1General design objectivewhile selecting the transformer(s) for a substationwould be toprovideat leasttwoormoretransformers,sothatacertainamountofredundancy isbuilt in,even if a standby system is provided. The total installed transformation capacity would bemarginallyhigher than theanticipatedmaximumdemand. Withgrowingemphasisonenergyconservation, thesystemdesign ismade forbothextremesof loading. During theperiodsoflowestloadinthesystem,itwouldbedesirabletooperateonlyonetransformerandswitchinadditional transformers as the load variation takes place in a day. Theminimum size of atransformerwouldquiteoftendependontheminimumloadthatisanticipatedoveraperiodofabout4hinaday.Totaltransformercapacityisgenerallyselectedonthebasisofpresentload,possiblefutureload,operationandmaintenancecostandothersystemconditionsandselectionof the maximum size (capacity) of the transformer is guided by shortcircuit making andbreakingcapacityoftheswitchgearusedinthemediumvoltagedistributionsystem.Maximumsizelimitationisimportantfromtheaspectoffeedtoadownstreamfault.

For feeding final singlephasedomestic typeof loadsorgeneraloffice loads it isadvisable toevenuse transformersof capacitymuch lower thanwhat the switchgear canhandle, so thatlowerfaultMVAisavailableinsuchareasanduseofhandheldequipmentfedthroughflexiblecordsissafe.

For reasons of reliability and redundancy it is normal practice to provide at least twotransformersforanyimportantinstallation.Interlinkingbytielinesisanalternativetoenhancereliability/redundancyisareaswherethereareanumberofsubstationsinclosevicinity,suchasacampuswiththreeorfourmultistoreyedblockseachwithasubstation.

Ringmaintypeofdistributionispreferredforcomplexeshavinganumberofsubstations.

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9.2.5.2.5.2Where twoormore transformers are tobe installed in a substation to supply amediumvoltagedistributionsystem,thedistributionsystemshallbedividedintoseparatesectionseachofwhichshallbenormallyfedfromonetransformeronlyunlessthemediumvoltageswitchgearhas the requisite shortcircuit capacity. Provision may, however, be made to interconnectseparate sections, through a bus coupler in the event of failure or disconnection of onetransformer.SeeSection9.2.4.2fordetailsoflocationandrequirementsofsubstation.

Thetransformers,thatmayatanytimeoperateinparallel,shallbesoselectedastosharetheload in proportion to their respective load ratings. While the general practice is to avoidoperationof transformers inparallel for feeding finaldistribution inbuildings, it ispossible touse transformerswith slightlydifferent impedanceor voltage taps tooperate inparallel,butwithappropriateprotection. Installationsdesigned forparalleloperationof transformersshallhave protection for avoiding circulating current between transformers, avoid overload ofanyonetransformerduetoreactancemismatchandthesystemshallbesoarrangedastotripthesecondarybreakerincasetheprimarybreakerofthattransformertrips.

9.2.5.2.6Switchgear

9.2.5.2.6.1 Switchgear (and its protective device) shall have breaking capacity not less than theanticipatedfault level inthesystematthatpoint. Systemfault levelatapoint indistributionsystemispredominantlydependentonthetransformersizeanditsreactance.Paralleloperationoftransformersnaturallyincreasesthefaultlevel.

9.2.5.2.6.2 Isolationandcontrollingcircuitbreaker shallbe interlocked so that the isolatorcannotbeoperatedunlessthecorrespondingbreakerisinopencondition.Thechoicebetweenalternativetypesofequipmentmaybeinfluencedbythefollowingconsiderations:

a) In certain installations supplied with electric power from remote transformersubstations,itmaybenecessarytoprotectmaincircuitswithcircuitbreakersoperatedbyearthfault,inordertoensureeffectiveearthfaultprotection.

b) Where largeelectricmotors, furnacesorotherheavyelectricalequipment is installed,themaincircuitsshallbeprotected fromshortcircuitsbyswitchdisconnector fuseorcircuitbreakers. Formotorprotection, thecombinationofcontactoroverloaddeviceand fuseorcircuitbreakersshallbeType2coordinated inaccordancewithacceptedstandards.Wherevernecessary,backupprotectionandearthfaultprotectionshallbeprovidedtothemaincircuit.

c) Wheremeanof isolatingmaincircuits isseparatelyrequired,switchdisconnector fuseorswitchdisconnectormayformpartofmainswitchboards.

9.2.5.2.6.3Itshallbemandatorytoprovidepowerfactorimprovementcapacitoratthesubstationbus.Suitable capacitormay be selected in consultationwith the capacitor aswell as switchgear

30

manufacturedependinguponthenatureofelectricalloadanticipatedonthesystem.Necessaryswitchgear/feedercircuitbreakershallbeprovidedforcontrollingofcapacitorbank.

Powerfactorof individualmotormaybe improvedbyconnecting individualcapacitorbanks inparallel.Forhigherrangeofmotors,whicharerunningcontinuouslywithoutmuchvariationsinload,individualpowerfactorcorrectionatloadendisadvisable.

Note: Care shouldbe taken in deciding the kVA rating of the capacitor in relation to themagnestisingkVAofthemotor. Overratingofthecapacitormaycause injurytothemotorandcapacitorbank. Themotorstillrotatingafterdisconnectionfromthesupply,mayactasgeneratorbyselfexcitationandproduceavoltagehigherthansupplyvoltage.Ifthemotorisagain switched on before the speed has fallen to about 80 percent of the normal runningspeed,thehighvoltagewillbesuperimposedonthesupplycircuitsandwilldamageboththemotorandcapacitor.

Asageneral rule, thekVA ratingof thecapacitor shouldnotexceed thenoloadmagnetizingkVAofthemotor.

Generally itwould be necessary to provide an automatic control for switching in capacitorsmatching the loadpower factorand thebusvoltage. Sucha schemewouldbenecessaryascapacitorspermanentlyswitchedinthecircuitmaycauseovervoltageattimesoflightload.

9.2.5.2.6.4 Sufficient additional space shall be allowed in substations and switchrooms to allowoperationandmaintenanceandpropermeansshallbeprovidedforisolatingtheequipmenttoallowaccessforservicing,testingandmaintenance.Sufficientadditionalspaceshallbeallowedfor temporary location and installation of standard servicing and testing equipment. Spaceshouldalsobeallowedtoprovideforanticipatedfutureextensions.

9.2.5.2.6.5Electricalinstallationsinaroomorcubicleorinanareasurroundedbywallfence,accesstowhichiscontrolledbylockandkeyshallbeconsideredaccessibletoauthorizedpersonsonly.

Awallorfence lessthan1.8m inheightshallnotbeconsideredaspreventingaccessunless ithasotherfeaturesthatprovideadegreeofisolationequivalenttoa1.8mfence.

9.2.5.2.6.6Harmonicsonthesupplysystemsarebecomingagreaterproblemduetotheincreasinguseof electronic equipments, computer, fluorescent,mercury vapour and sodium vapor lighting,controlled rectifier and inverters for variable speeddrives,power electronics andothernonlinearloads.Harmonicsmayleadtoalmostasmuchcurrentintheneutralasinthephases.Thiscurrentisalmostentirelythirdharmonic.Phaserectificationdevicesmaybeconsideredforthelimitsofharmonicvoltagedistortionmaybeconsideredattheplanningstageinsuchcases.

Withthewidespreaduseofthyristorandrectifierbasedloadsthereisnecessityofprovidingafullsizeneutral;butthisrequirement is limitedto the3phase4wiredistributiongenerally in

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the 400/230 V system. As a result it is not desirable to use halfsize neutral conductor, aspossibilityofneutralconductoroverloadduetoharmonicsislikely.

9.2.5.3 Receptionanddistributionofmainsupply

9.2.5.3.1Controlatpointofcommencementofsupply

9.2.5.3.1.1Thereshallbeacircuitbreakerorminiaturecircuitbreakersora loadbreakswitchfuseoneach live conductor of the supplymains at the point of entry. Thewiring throughout theinstallationshallbesuchthatthereisnoswitchorfuseunitintheearthedneutralofconductor.Theneutralshallalsobedistinctlymarked. In thisconnection,Rules,asamendedup todateshallalsobereferred.

9.2.5.3.1.2 The main switch shall be easily accessible and situated as near as practicable to theterminationofserviceline.

9.2.5.3.1.3 On themain switch,where the conductors include an earthed conductor of a twowiresystemoranearthedneutralconductororamultiwiresystemoraconductorwhich is tobeconnected thereto, an indication of a permanent nature shall be provided to identify theearthed neutral conductor. In this connection, Electricity Company ofGhanaRules, shall bereferredasamendeduptodate.

9.2.5.3.1.4Energymeters

EnergymetersshallbeinstalledinresidentialbuildingsatsuchaplacewhichisreadilyaccessibletotheownerofthebuildingandtheAuthority.Theseshouldbeinstalledataheightwhereitisconvenient tonote themeter reading, it shouldpreferablynotbe installedbelowonemetrefrom the ground. The energymeters should either be providedwith a protecting covering,enclosingitcompletelyexcepttheglasswindowthroughwhichthereadingsarenotedorshouldbemounted inside a completely enclosed panel providedwith hinged or sliding doorswitharrangementforlocking.

Inmultistoreyedbuildingsmetersshallbe installedwithtappingpointformetersoftherisingmain(bustrunking)onindividualfloors.

9.2.5.3.2Mainswitchesandswitchboard

9.2.5.3.2.1Allmainswitchesshallbeeitherofmetalcladenclosedpatternorofanyinsulatedenclosedpatternwhichshallbefixedatcloseproximitytothepointofentryofsupply.Everyswitchshallhave anenvironmentalprotection level rating (IP), so that itsoperation is satisfactory in theenvironmentoftheinstallation.

NoteWoodworkshallnotbeusedfortheconstructionormountingofswitchesandswitchboardsinstalledinabuilding.

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9.2.5.3.2.1Location

a) The locationof themainboard shouldbe such that it is easily accessible forfireman and other personnel to quickly disconnect the supply in case ofemergencies.Iftheroomislockedforsecurity,meansofemergencyaccess,byschemessuchasbreakglasscupboard,shallbeincorporated.

b) Mainswitchboardshallbe installed inroomsorcupboardssoastosafeguardagainstoperationbyunauthorizedpersonnel.

c) Switchboardsshallbeplacedonlyindrysituationsandinventilatedroomsandthey shall not be placed in the vicinity of storage batteries or exposed tochemicalfumes.

d) Indampsituationorwhereinflammableorexplosivedust,vapourorgasislikelytobepresent,theswitchboardshallbetotallyenclosedandshallhaveadequatedegreeofprotection.Insomecasesflameproofenclosemaybenecessitatedbyparticularcircumstances.

e) Switchboardsshallnotbeerectedabovegasstovesorsinks,orwithin2.5moranywashingunitinthewashingroomsorlaundries,orinbathrooms,lavatoriesortoilets,orkitchens.

f) In case of switchboards unavoidably fixed in places likely to be exposed toweather, todrip,or toabnormalmoist temperature, theoutercasingshallbeweatherproof and shall be provided with glands or bushings or adopted toreceivescrewedconduit,accordingtothemannerinwhichthecablesarerun.

g) Adequate illumination shall be provided for all working spaces about theswitchboardswheninstalledindoors.

9.2.5.3.2.3Metalcladswitchgearshallpreferablybemountedonanyofthefollowingtypesofboards:

a) HingedtypemetalboardsThese shallconsistofaboxmadeof sheetmetalnot less than2mm thickandshallbeprovidedwithahingedcover toenabletheboardtoswingopenforexaminationofthewiringattheback.

The jointsshallbewelded. Thereshallbeacleardistanceofnot lessthan2/5cmbetweentheteakwoodboardandthecover,thedistancebeing increasedfor larger boards in order that on closing of the cover, the insulation of thecablesisnotsubjectedtodamageandthereshouldbenoexcessivetwistingorbendinginanycase. Theboardshallbesecurelyfixedtothewallbymeansofrag bolts, plugs, or wooden plugs and shall be provided with a lockingarrangementandanearthingstud. Allwirespassingthroughthemetalboard

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shallbeprotectedbya rubberorwoodenbushat theentryhole. Theearthstud should commensurate with the size of earth lead/leads. Alternatively,metalboardsmaybemadeofsuitablesizeangleironofminimumsize35mmx35mmx6mmorchannel ironofminimumsize35mmx25mmx6mmframesworktaggedtospecificationonfrontwitha3mmthickmildsteelplateandonbackwith1.5mmthickmidsteelsheet.Noapparatusshallprojectbeyondanyedgeofpanel.Nofusebodyshallbemountedwithin2.5cmofanyedgeofthepanel.

NoteSuchtypeofboardsareparticularlysuitableforsmallswitchboardformountingmetalcladswitchgearconnectedtosupplyatlowvoltages.

b) FixedtypemetalboardsTheseshallconsistofanangleorchannelironframefixedonthewalloronfloorandsupportedonthewallatthetop,ifnecessary.Thereshallbeacleardistanceof1m infrontoftheswitchboards. IfthereareanyattachmentsofbareconnectionsatthebackoftheswitchboardsECGrulesshall apply. The connections between the switchgear mounting and theoutgoingcableuptothewallshallbeenclosedinaprotectionpipe.

NoteSuchtypeofboardsareparticularlysuitableforlargeswitchboardsformountinglargenumberofswitchgearsorhighcapacitymetalcladswitchgearorboth.

c) Protectedtype switchboard A protected switchboard is one where all of theconductorsareprotectedbymetalorotherenclosures.Theymayconsistofametalcubiclepanel,oranironframeuponwhichismountedmetalcladswitchgear.Theyusually consistofamain switch,busbarsand circuitbreakersor fuses controllingoutgoingcircuits.

d) Opentype switchboard An open type switchboard is one,which has exposedcurrentcarryingpartsonthefrontoftheswitchboard. Thistypeofswitchboard israrely used nowadays but where this exists, a hand rail or barrier has to beprovided to prevent unintentional or accidental contactwith exposed live parts.Theymustbe located inaspecialswitchroomorenclosureandonlyacompetentpersonmayhaveaccesstotheseswitchboards.

NoteTheseboardsmaybeexistinginoldinstallations. Itisrecommendedthatthey be phased out. With the continuously increasing fault power feed due toincreases in generation and strengthening of distribution systems, these openboardsareasourceofaccidents.

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9.2.5.3.2.4Recessingofboards

Where so specified, the switchboards shall be recessed in the wall. Ample room shall beprovidedatthebackforconnectionandatthefrontbetweentheswitchgearmountings.

9.2.5.3.2.5Markingofapparatus

a) Whereaboardisconnectedtovoltagehigherthan250V,alltheapparatusmountedonitshallbemarkedonthefollowingcoloursto indicatethedifferentpolesorphasestowhichtheapparatusoritsdifferentterminalsmayhavebeenconnected.

AlternatingCurrent DirectCurrent

Threephasesred,yellow,blue1Neutralblack

Threewiresystem2outerwire,positiveredandnegativeblue1Neutralblack

Wherefourwirethreephasewiring isdone,theneutralshallbe inonecolourandtheotherthreewires inanothercolourasmentionedaboveorshallbesuitablytaggedorsleevedforfoolproofidentification.

b) Whereaboardhasmorethanoneswitch,eachsuchswitchshallbemarkedtoindicatewhichsectionof the installation itcontrols. Themainswitchshallbemarkedassuchandwherethereismorethanonemainswitchinthebuilding,eachsuchswitchshallbemarkedtoindicatewhichsectionoftheinstallationitcontrols.

Allmarkingsshallbeclearandpermanent.

9.2.5.3.2.6Drawings

Before proceeding with the actual construction, a proper drawing showing the detaileddimensionsanddesignincludingthedispositionofthemountingsoftheboards,whichshallbesymmetrically and neatly arranged for arriving at the overall dimensions, shall be preparedalongthebuildingdrawing.Suchdrawingswillshowthemandatoryclearancespacesifany,andclearheightbelow the soffitof thebeam to satisfy regulationsand safetyconsiderations, sothatotherdesignersorinstallersdonotgetintosuchareasorspacesfortheirequipment.

9.2.5.3.2.7Where a board hasmore than one switch, each such switch shall bemarked to indicatewhichsectionoftheinstallationitcontrols.Themainswitchshallbemarkedassuchandwherethereismorethanonemainswitchinthebuilding,eachsuchswitchshallbemarkedtoindicatewhichsectionoftheinstallationitcontrols.

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Allmarkingsshallbeclearandpermanent.

9.2.5.3.2.8 Busbar chambers, which feed two or more circuits, must be controlled by a maindisconnnector(TP&N),orIsolatinglinksorTPNMCBtoenablethemtobedisconnectedfromthesupply.

9.2.5.3.3Distributionboards

A distribution board comprises of one ormore protective devices against over current andensuring thedistributionofelectrical energy to the circuits. Distributionboard shallprovideplenty of wiring space, to allow working as well as to allow keeping the extra length ofconnectingcables,likelytoberequiredformaintenance.

9.2.5.3.3.1Maindistributionboardshallbeprovidedwithacircuitbreakeroneachpoleofeachcircuit,or a switchwith a fuseon thephaseor live conductor and a linkon theneutralor earthedconductorofeachcircuit.Theswitchesshallalwaysbelinked.

Allincomersshouldbeprovidedwithsurgeprotectiondevices.

9.2.5.3.4Branchdistributionboards

9.2.5.3.4.1 Branch distribution boards shall be provided, alongwith earth leakage protective device(ELCB)(incoming),withafuseoraminiaturecircuitbreakerorbothofadequaterating/settingchosenon the live conductorof each subcircuit and the earthedneutral conductor shallbeconnected to a common link and be capable of being disconnected individually for testingpurposes. At leastone sparecircuitof the same capacity shallbeprovidedoneeachbranchdistribution board. Further, the individual branching circuits (outgoing) shall be protectedagainst overcurrentwithminiature circuit breaker of adequate overcurrentwithminiaturecircuit breaker of adequate rating. In residential/industrial lighting installations, the variouscircuitsshallbeseparatedandeachcircuitshallbeindividuallyprotectedsothatintheeventoffault,onlytheparticularcircuitgetsconnected.

9.2.5.3.4.2Circuitsshallbeseparatedfor installationathigher levelsuchasthose intheceilingandathigher levels,above1cm.on thewallsand for installationsat lower levelsuchassockets forportableorstationerypluginequipments.Fordevicesconsuminghighpowerandwhicharetobesuppliedthroughsupplycordandplug,separatewiringshallbedone.ForpluginequipmentprovisionsshallbemadeforprovidingELCBprotectioninthedistributionboard.

9.2.5.3.4.3 It ispreferabletohaveadditionalcircuitforkitchenandbathrooms. Suchsubcircuitshallnothavemorethanatotaloftenpointsoflight,fansand6Asocketoutlets.Wheretheloadofsuchcircuitisprovided,thenumberoffansinthecircuitshallnotexceedten.Powersubcircuitshallbedesignedaccordingtotheloadbutinnocaseshalltherebemorethantwo16Aoutletsoneachsubcircuit.

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9.2.5.3.4.4Thecircuitsforlightingofcommonareashallbeseparate.Forlargehalls3wirecontrolwithindividualcontrolandmastercontrolinstalledneartheentranceshallbeprovidedforeffectiveconservationofenergy.

9.2.5.3.4.5Wheredaylightwouldbeavailable,particularly in largehalls, lighting in theareanear thewindows, likely to receivedaylightshallhaveseparatecontrols for lights,so that theycanbeswitchedoffselectivelywhendaylightisadequate,whilekeepingthelightsintheareasremotefromthewindowson.

9.2.5.3.4.6Circuits forsocketoutletsmaybekeptseparatecircuits feeding fansand lights. Normally,fansand lightsmaybewiredonacommoncircuit. In largespacescircuits for fansand lightsmayalsobesegregated.Lightsmayhavegroupcontrolinlargehallsandindustrialareas.Whileprovidinggroupcontrolconsiderationmaybegiven for thenatureofuseof thearea litbyagroup.Considerationhastobegivenforthedaylightutilization,whilegrouping,sothatagroupfeedingareasreceivingdaylightcanbeselectivelyswitchedoffduringdaylightperiod.

9.2.5.3.4.7Theloadonanylowvoltagesubcircuitshallnotexceed3000W.Incaseofanewinstallation,allcircuitsandsubcircuitsshallbedesignedwithaninitialloadofabout2500W,soastoallowaprovisionof20percent increase in loaddue toany futuremodification. Powersubcircuitsshallbedesignedaccording to the load,where the circuit ismeant fora specificequipment.Goodpracticeistolimitacircuittoamaximumoffoursockets,whereitisexpectedthattherewill be diversity due to use of very few sockets in large spaces (example sockets for use ofvacuumcleaner).Generalpracticeistolimitittotwosocketsinacircuit,inbothresidentialandnonresidential buildings and to provide a single socket on a circuit for a known heavy loadappliancesuchasairconditioner,cookingrangeetc.

9.2.5.3.4.8Inwiringinstallationsatspecialplaceslikeconstructionsites,stadium,shipyards,openyardsinindustrialplants,etc.wherealargenumberofhighwattagelampmayberequired,thereshallbenorestrictionofloadonanycircuitbutconductorsusedinsuchcircuitshallbeofadequatesizefortheloadandpropercircuitprotectionshallbeprovided.

9.2.5.3.5Locationofdistributionboards

a) thedistributionboardsshallbelocatedasnearaspossibletothecentreoftheloadtheyareintendedtocontrol;

b) These shall be fixed on suitable stanchion or wall and shall be accessible forreplacement/resetofprotectivedevices,and shallnotbemore than1.8m from floorlevel.

c) These shall be of either metalclad type, or air insulated type. But, if exposed toweatherordamp situations, these shallbeof theweatherproof typeand, if installed

37

whereexposed toexplosivedust,vapourorgas, these shallbeof flameproof type inaccordancewithacceptedstandards.Incorrosiveatmospheres,theseshallbetreatedwithanticorrosivepreservativeorcoveredwithsuitableplasticcompound.

d) Wheretwoand/ormoredistributionboardsfeedinglowvoltagecircuitsarefedfromasupplyofmediumvoltage,themetalcaseshallbemarkedDanger415Vandidentifiedwithproperphasemarkinganddangermarks.

e) Eachshallbeprovidedwithacircuitlistgivingdiagramofeachcircuitwhichitcontrolsandthecurrentratingofthecircuitandsizeoffuseelement.

f) Inwiringbranchdistributionboard,total loadofconsumingdevicesshallbedividedasfaraspossibleevenlybetweenthenumberofways intheboard leavingspacecircuitsforfutureextension.

9.2.5.3.6Protectionofcircuits

a) Appropriateprotectionshallbeprovidedatswitchboards,distributionboardsandatalllevelsofpanels forallcircuitsand subcircuitsagainst shortcircuits,overcurrentandotherparametersas required. Theprotectivedevice shallbe capableof interruptingmaximumprospectiveshortcircuitcurrentthatmayoccur,withoutdanger.Theratingsand settingsof fusesand theprotectivedevices shallbe coordinated soas toaffordselectivityinoperationandinaccordancewithacceptedstandards.

b) Wherecircuitbreakersareusedforprotectionofamaincircuitandofthesubcircuitsderived therefrom, discrimination in operation may be achieved by adjusting theprotectivedevicesofthesubmaincircuitbreakerstooperateatlowercurrentsettingsandshortertimetagthanthemaincircuitbreaker.

c) WhereHRCtypefusesareusedforbackupprotectionofcircuitbreakers,orwhereHRCfusesareusedforprotectionofmaincircuits,andcircuitbreakersfortheprotectionofsubcircuitsderivedthere from, intheeventofshortcircuitsprotectionexceedingtheshortcircuitscapacityof thecircuitbreakers, theHRC fuses shalloperateearlier thanthe circuitbreakers;but for smalleroverloadswithin the shortcircuit capacityof thecircuitbreakers,thecircuitbreakersshalloperateearlierthantheBRICfuseblows.

d) If rewireable type fuses areused to protect subcircuits derived from amain circuitprotectedbyHRCtypefuses,themaincircuitfuseshallnormallyblowintheeventofashortcircuit or earth fault occurring on subcircuit, although discrimination may beachieved inrespectofoverloadcurrents. Theuseofrewireable fuses isrestricted tothecircuitswithshortcircuitlevelof4kA;forhigherleveleithercartridgeorHRCfusesshallbeused. However,useof requireable fuse isnotdesirable,even for lower fault

38

levelareas.MCBsprovideabetteranddependableprotection,astheircurrentsettingisnottemperable.

e) A fuse carrier shall not be finedwith a fuse element larger than that forwhich thecarrierisdesigned.

f) Thecurrentratingofafuseshallnotexceedthecurrentratingofthesmallestcable inthecircuitprotectedbythefuse.

g) Every fuse shall have its own case or cover for the protection of the circuit and anindelibleindicationofitsappropriatecurrentratinginanadjacentconspicuousposition.

9.2.5.4Voltageandfrequencyofsupply

Itshouldbeensuredthatallequipmentconnectedtothesystemincludinganyappliancestobeusedonthemaresuitableforthevoltageandfrequencyofsupplyofthesystem.Thenominalvaluesof lowandmediumvoltagesystems inGhanaare240Vand415Vac.,respectively,andthefrequency50Hz.

Notes

1. Thedesignofwiringsystemandthesizesofthecablesshouldbedecidedtakingintoaccounttwofactors;a) VoltageDropThisshouldbekeptaslowaseconomypermitstoensureproperfunctioningof

allelectricalappliancesandequipmentincludingmotors;and

b) Firstcostagainstoperatinglosses.

2. Inviewof the latestdevelopmentat the international level,nominalsystemvoltageshavebeenalignedwithIECrecommendationandaccordinglythenominalacsystemvoltageshallbechangedfrom240/415Vto230/400Vwithatoleranceof+10percent.

9.2.5.5Ratingofcablesandequipments

9.2.5.5.1Thecurrentcarryingcapacityofdifferent typesofcablesshallbechosen inaccordancewithgoodpractice.

9.2.5.5.2Thecurrentratingsofswitchesfordomesticandsimilarpurposesare6Aand16A.

9.2.5.5.3Thecurrentratingsofisolatorsandnormaldutyswitchesandcompositeunitsofswitchesandfusesshallbeselectedfromoneofthefollowingvalues:

16,25,32,63,100,160,200,320,400,500,630,800,1,000and1250A.

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9.2.5.5.4TheratingsofrewireableandHRCfusesshallbeinaccordancewithgoodpractice.

9.2.5.5.5Thecurrentratingsofminiaturecircuitbreakersshallbechosenfromthevaluesgivenbelow:

6,8,10,13,16,20,25,32,40,50,63,80,100and125A

9.2.5.5.6The current ratingsofmoulded case circuitbreakers shallbe chosen from the values givenbelow.

100,125,160,200,250,315,400,630,800,1,000,1250and1600A

9.2.5.5.7Thecurrentratingsofaircircuitbreakersshallbechosenfromthevaluesgivenbelow:

630,800,1000,1250,1600,2000,2500,3200and4000A.

9.2.5.5.8Thecurrentratingsofthedistributionfuseboardshallbeselectedfromoneofthefollowingvalues:

6,16,25,32,63and100A.

9.2.5.6Installationcircuits

TypeofCircuit WireSize NumberofCircuitsLightingSocketoutlets10ASocketoutlets15or20AWaterheater3kWWaterheater36kWFreestandingelectricrangeSeparateovenand/orcooktopPermanently connectedappliances including dishwashers,heaters,etc.Submains to garage or outbuildingMainscable

1.0 mm22.0 2.5mm22.5mm21.5mm22.5mm26.0mm2

4.0mm22.5mm22.5mm2

16mm2

2ormoreAnynumberAreas such as kitchens andlaundries 3 x double socketoutlets per circuit. Other areasupto12doublesocketoutlets111111above10A.Upto10Acanbewired as part of a socketoutletcircuit1foreach1

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9.2.5.6.1Selectingandinstallingcables

9.2.5.6.1.1Cableinsulationtypes

Forthemainscable Toughplasticsheathed(TPS)cable

Forinstallationwiring Toughplasticsheathed(TPS)cables

Formainearthormainequipotentialwire Polyvinylchloride(PVC)insulatedconduitwire

Underground installation and installation in

cabletrench,feedersbetweenbuildings,etc.

PVC insulated, PVC sheathed armoured cables or

XLPE insulated, PVC sheathed cables armoured

cables

Installationinplantrooms,switchroomsetc,

oncabletrayorladderorprotectedtrench,

whereriskofmechanicaldamagetocabledoes

notexist.

PVCinsulated,PVCsheathedorXLPEinsulated,PVC

sheathedunarmouredcables

For thepurposeof thisCodecablesabove1mm2musthavestrandedconductors. Allcableswheninstalled,mustbeadequatelyprotectedagainstmechanicaldamage.Thiscanbecarriedoutbyeitherhavingadditionalprotection,suchasbeingenclosedinPVCconduitormetalpipes,orplacingthecablesinasuitablelocationthatrequiresnoadditionalprotection.Thecablesforwiring circuits in electrical installation must have the appropriate wire size matching therequirementoftheloadsandthefollowingtablegivestherecommendationsfordifferenttypesofloads.

9.2.5.6.1.2Circuitwiresizes

Circuits MinimumWireSize WireColour1waylighting 2+Ecablewires1.5mm2 RedBlackGreenorGreen/Yellow2way lighting control(straps between the 2switches)

3wirecable1.5mm2 RedWhiteBlue

Storage water heatersupto3kW

2 + E cable 1.5mm2 (strandedconductors)

RedBlackGreenorGreen/Yellow

Storage water heatersbetween3kWand6Kw

2 + E cable 2.5mm2 (strandedconductors)

RedBlackGreenorGreen/Yellow

Socketoutlets andpermanent connectionunits

2 + E cable 2.5mm2 (strandedconductors)

RedBlackGreenorGreen/Yellow

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Submains to garages oroutbuildings

2 + E cable 2.5mm2 (strandedconductors)

RedBlackGreenorGreen/Yellow

Cookinghobs 2+Ecable4mm2 RedBlackGreenorGreen/YellowSeparateovens 2 + E cable 4mm2 (stranded

conductors)Electricrange 2 + E cable 6mm2 (stranded

conductors)RedBlackGreenorGreen/Yellow

Mains 2 wire cable 16 mm2 (strandedconductors)

RedBlack

Main equipotentialbondingwire

Conduit wire 4mm2 (strandedconductors)

GreenorGreen/Yellow

Mainearthwire Conduit wire 6mm2 (strandedconductors)

GreenorGreen/Yellow

2 + E is also known astwinandearth

Switchorisolatorcontrollingawaterheaterorgeysershouldnotbelocatedwithin1mfromthelocationof a showerorbath tub, to avoid aperson inwet condition reaching the switchorisolator.Itispreferabletoprovidethecontrolswitchoutsidethebathroomneartheentranceand provide an indication at thewater heater. A socket or a connector blockwith suitableprotection againstwater spray shouldbeprovided to connect thewaterheater. The aboveconsiderations apply to switches for outdoor lights and other appliances,with the object ofavoidanceofoperationofaswitchwhenaperson iswet. Socket inkitchen,bathroom,toilet,garageetc.shouldnotbeprovidedwithinaheightof1mfromthegroundlevel.Similarcarehastobe taken for installations involving foundations, swimmingpoolsetc. Light fittings in suchareasshouldbe fedat lowvoltage,preferably throughan isolating transformerwithaproperearthleakageprotection.

9.2.5.6.2Requirementsforphysicalprotectionofundergroundcables

ProtectiveElement SpecificationsBricks

a) 100mmminimumwidthb) 25mmthickc) Sand cushioning 100mm and sand cover 100

mm

Concreteslabs Atleast50mmthick

Plastic slabs (polymetric cover strips), Fibre reinforcedplastic

Atleast10mmthick,dependingonpropertiesandhastobematchedwiththeprotectivecushioningandcover

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PVC conduit or PVC pipe or stoneware pipe or humepipe

Thepipediametershouldbesuchthatthecableisabletoeasilyslipdownthepipe

The trench shallbebackfilled to cover the cable initiallyby200mmof fill;and thenaplasticmarketstripoverthefulllengthofcableinthetrench.Fillthetrenchshallbelaidbeforefillingthefulltrench.Themarkersignswhereanycableentersorleavesabuildingshallbeput.Thiswillidentifythatthereisacablelocatedundergroundnearthebuilding.Ifthecablesriseabovegroundtoenterabuildingorotherstructure,amechanicalprotectionsuchasaGIpipeorPVCpipeforthecablefromthetrenchdepthtoaheightof2.0mabovegroundshallbeprovided.

9.2.5.7Lightingandlevelsofillumination

9.2.5.7.1General

Lighting installation shall take into consideration themany factors onwhich the quality andquantityofartificial lightingdepends. Themodernconcept istoprovide illuminationwiththehelpofalargenumberoflightsourcesnotofhigherilluminationlevel.Alsomuchhigherlevelsofilluminationarecalledfor,thaninthepast,oftennecessitatingtheuseoffluorescentlightingsuitablysupplementedwithincandescentfittings,whererequired.

9.2.5.7.2Futuredemand

However, ifforfinancialreasons, it isnotpossibletoprovidea lighting installationtogivetherecommended illumination levels, thewiring installationat least should sodesigned thatatalater date, it will permit the provision for additional lighting fittings or conversion fromincandescenttofluorescentlightingfittingstobringtheinstallationtotherequiredstandard.Itisessentialthatadequateprovisionsshouldbemadeforalltheelectricalserviceswhichmayberequiredimmediatelyandduringtheintendedusefullifeofthebuilding.

9.2.5.7.3Principlesoflighting

Whenconsidering the functionofartificial lighting,attentionshouldbegiven to the followingprinciplecharacteristicsbeforedesigninganinstallation.

a) Illuminationanditsuniformity;b) Specialdistributionof light. This includes a reference to the compositionofdiffused and

directional light,directionof incidence, thedistributionof luminances and thedegreeofglare;and

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c) Colourofthelightandcolourrendition.

9.2.5.7.4Thevarietyofpurposeswhichhavetobekeptinmindwhileplanningthelightinginstallationcouldbebroadlygroupedas:

a)industrialbuildingsandprocesses;

b)offices,schoolsandpublicbuildings;

c)surgeriesandhospitals;and

d)hostels,restaurants,shopsandresidentialbuildings.

9.2.5.7.4.1Itisimportantthatappropriatelevelsofilluminationfortheseandthetypesandpositionsoffittingsdeterminedtosuitthetaskandthedispositionoftheworkingplanes.

9.2.5.7.5Forspecificrequirementsforlightingofspecialoccupancies,referenceshallbemadetogoodpractice.

9.2.5.7.6Energyconservation

Energyconservationmaybeachievedbyusingthefollowing:

a) Energyefficientlamps,chokes,ballast,etc.forlightingequipmentb) Efficient switching systems such as remote sensors, infrared switches, master switches,

remoteswitches,etc.forswitchingONandOFFoflightingcircuits.c) Properlymade/connectedjointscontactstoavoidloosejointsleadingtolossofpower.

9.2.5.8Inconditionswherethesystemvoltageexceeds650V,asisthecaseinindustriallocations,fordetailsofdesignandconstructionwiringinstallation,referencemaybemadetogoodpractice.

9.2.5.9GuidelinesforelectricallayoutinresidentialbuildingsForguidelinesforelectricallayoutinresidentialbuildings,referencemaybemadetogoodpractice.Atypicaldistributionscheme inaresidentialbuildingwithseparatecircuitsfor lightsand fansandforpowerappliancesisgiveninFig.1.

9.2.5.10Fordetailedinformationregardingtheinstallationofdifferentelectricalequip