Electrical Installations, MCB, MCCB, ELCB

Electrical Installations
SFU,
MCB,
MCCB,
ELCB,
TYPES OF WIRES AND
CABLES

1. St. Martin's Engineering College
An autonomous institution
NBA&NACC A+ Accredited
Department of Electrical &Electronics Engineering
BEE_UNIT-V
ELECTRICAL INSTALLATIONS
By
N. DANIEL MANOJ
Assistant Professor

2. Contents:
ComponentsofLTSwitchgear:SwitchFuseUnit(SFU),MCB,ELCB,MCCB,
TypesofWiresandCables
ElectricalSafetyprecautionsinhandlingelectricalappliances,electricshock,first
aidforelectricshock,safetyrules.

3. Components of LT Switchgear: Switch Fuse Unit
(SFU), MCB, ELCB, MCCB
Switchgear :Theapparatususedforswitching,controllingand
protectingtheelectricalcircuitsandequipmentisknownasswitchgear.
Theterm‘switchgear’isagenerictermencompassingawiderangeof
productslikecircuitbreakers,switches,switchfuseunits,off-loadisolators,
HRCfuses,contactors,earthleakagecircuitbreaker,etc...

4. Components of LT Switchgear: Switch Fuse Unit
(SFU), MCB, ELCB, MCCB
EssentialFeaturesofSwitchgear
Theessentialfeaturesofswitchgearare:
1.CompleteReliability
2.Absolutelycertaindiscrimination
3.Quickoperation
4.Provisionformanualcontrol

5. Components of LT Switchgear: Switch Fuse Unit
(SFU), MCB, ELCB, MCCB
Classification of Switchgear:
Switchgear can be classified on the basis of voltage level into the following:
1.Low voltage (LV) Switchgear: upto 1KV
2.Medium voltage (MV) Switchgear: 3 KV to 33 KV
3.High voltage (HV) Switchgear: Above 33 KV

6. Components of LT Switchgear: Switch Fuse Unit
(SFU), MCB, ELCB, MCCB
Components ofLTSwitchgear :
ThetermLTSwitchgearincludeslowvoltageCircuitBreakers,Switches,offload
electricalisolators,HRCfuses,EarthLeakageCircuitBreaker,MiniatureCircuit
Breakers(MCB)andMoldedCaseCircuitBreakers(MCCB)etci.e.alltheaccessories
requiredtoprotecttheLVsystem.ThemostcommonuseofLVswitchgearisinLV
distributionboard.

7. Components of LT Switchgear: Switch Fuse Unit
(SFU), MCB, ELCB, MCCB
FUSE:
Fuseisasimplestandcheapestdeviceusedforinterruptinganelectrical
circuitundershortcircuit,orexcessiveoverload,currentmagnitudes.
Theactionofafuseisbasedupontheheatingeffectoftheelectric
circuit.Thepartwhichactuallymeltsandopensthecircuitisknownas
thefuseelement.
https://www.eeeguide.com/fuses-definition/

9. Components of LT Switchgear: Switch Fuse Unit
(SFU), MCB, ELCB, MCCB
Thefusehasinversetime-currentcharacteristics

10. Advantages :
•Itisthecheapestformofprotectionavailable.
•Itrequiresnomaintenance.
•Itsoperationisinherentlycompletelyautomaticunlikeacircuitbreakerwhichrequiresan
elaborateequipmentforautomaticaction.
•Itcanbreakheavyshort-circuitcurrentswithoutnoiseorsmoke.
•Thesmallersizesoffuseelementimposeacurrentlimitingeffectundershort-circuit
conditions.
•Theinversetime-currentcharacteristicofaFusesDefinitionmakesitsuitableforover
currentprotection.
•Theminimumtimeofoperationcanbemademuchshorterthanwiththecircuitbreakers.

11. Disadvantages :
•Considerabletimeislostinrewiringorreplacingafuseafteroperation.
•Onheavyshort-circuits,discriminationbetweenfusesinseriescannotbeobtained
unlessthereissufficientdifferenceinthesizesoftheFusesDefinitionconcerned.
•Thecurrent-timecharacteristicofafusecannotalwaysbeco-relatedwiththatof
theprotectedapparatus.

12. FUSE UNITS:
The various types of fuse units, most commonly available are:
1.Round type fuse unit.
2.Kit-kattype fuse unit.
3.Cartridge type fuse unit.
4.HRC (High Rupturing Capacity) fuse units and
5.Semiconductor fuse units

13. 1. Round type fuse unit
Thistypeoffuseunitconsistsofaporcelainorbakelitebox
andtwoseparatedwireterminalsforholdingthefusewire
betweenthem.Thistypeoffuseisnotcommonuseonaccount
ofitsfollowingdisadvantages:
1.Oneoftheterminalsremainalwaysenergizedand,therefore,
forreplacementoffuseeithertheworkerwillhavetotouchthe
livemainsoropenthemainswitch.
2.Whenthefuseblowsoffthereistoomucharcingandtheunit
maybedamaged.Aftertwoorthreearcingthefuseunitbecomes
unusable.T

14. 2. Rewirable or Kit -katType Fuses
Themostcommonlyusedfusein“housewiring’
andsmallcurrentcircuitsisthesemi-enclosedor
rewirablefuse(alsosometimesknownaskitkat
typefuse).Itconsistsofaporcelainbasecarrying
thefixedcontactstowhichtheincomingand
outgoingliveorphasewiresareconnectedanda
porcelainfusecarrierholdingthefuseelement,
consistingofoneormorestrandsoffusewire,
stretchedbetweenitsterminals.

15. When fuse bridge with fuse element is inserted and the switch is made ‘on’ then only the
circuit is completed.These fuse units are rated as 5.15, 30 up to 300 Amps

16. Disadvantages of Rewirable or Kitkat
Type Fuses
• Unreliable operation.
• Lack of discrimination.
• Small time lag.
• Low rupturing capacity.
• No current limiting feature.
• Slow speed of operation.

17. 3. Cartridge Type Fuses
Thisisatotallyenclosedtypefuseunit.It
essentiallyconsistsofaninsulating
containerofbulbortubeshapeandsealed
atitsendswithmetalliccapknownas
cartridgeenclosingthefuseelementand
filledwithpowderorgranularmaterial
knownasfiller.Therearevarioustypesof
materialsusedasfillerlikesand,calcium
carbonate,quartzetc.Thistypeoffuseis
availableupto660Vandthecurrentrating
upto800A

18. 4. High Rupturing Capacity
(HRC) Fuses
Withaveryheavygenerating
capacitiesofthemodernpower
stations,extremelyheavycurrents
wouldflowintothefaultandfuse
clearingthefaultwouldberequiredto
withstandextremelyhighstressesin
thisprocess.

19. Switch Fuse Unit (SFU):
Switchfuseisacombinedunitandisknownasanironcladswitch,beingmadeofiron.
Itmaybedoublepoleforcontrollingsinglephasetwo-wirecircuitsortriplepolefor
controllingthree-phase,3-wirecircuitsortriplepolewithneutrallinkforcontrolling3-
phase,4-wirecircuits.Therespectiveswitchesareknownasdoublepoleironclad
(DPIC),triplepoleironclad(TPIC),andtriplepolewithneutrallinkironclad(TPNIC)
switches.
DPIC

20. DPIC
TPIC TPNIC

21. Switch Fuse Unit (SFU ):
1. For Two-wire DC Circuits or Single Phase AC Circuits:
240V, 16A, DPIC switch fuse
2. For Three-Wire DC Circuits: 500V, 32A (63/100/150 or
higher amperes), IS approved TPIC switch fuse.
3. For Three-Phase Balanced Load Circuits: 415V, 32A
(63/100/150 or higher amperes), IS approved TPIC switch fuse.

23. Miniature Circuit Breaker (MCB):
Adevicewhichprovidesdefiniteprotectiontothewiringinstallationsand
sophisticatedequipmentagainstover-currentsandshort-circuitfaults.
Thermaloperation(overloadprotection)isachievedwithabimetallic
strip,whichdeflectswhenheatedbyanyovercurrentsflowingthroughit.
Indoingso,releasesthelatchmechanismandcausesthecontactstoopen.
Inverse-timecurrentcharacteristicsresult.i.e.greatertheoverloador
excessivecurrent,shorterthetimerequiredtooperatetheMCB.

26. Miniature Circuit Breaker (MCB ):
Onoccurrenceofshortcircuit,therisingcurrentenergizesthesolenoid,
operatingtheplungertostrikethetriplevercausingimmediatereleaseofthe
latchmechanism.Rapidityofthemagneticsolenoidoperationcauses
instantaneousopeningofcontacts.MCBsareavailablewithdifferentcurrent
ratingsof0.5,1.2,2.5,3,4,5,6,7.5,10,16,20,25,32,35,40,63,100,125,
160Aandvoltageratingof240/415VACandupto220VDC.Operating
timeisveryshort(lessthan5ms).Theyaresuitablefortheprotectionof
importantandsophisticatedequipment,suchasair-conditioners,refrigerators,
computersetc.

28. Earth Leakage Circuit Breaker (ELCB):
Itisadevicethatprovidesprotectionagainstearthleakage.
Itisusedwhentheproductoftheoperatingcurrentinamperesand
theearth-loopimpedanceinohmsdoesnotexceed40.suchcircuit
breakersisusedwhereconsumer’searthingterminalisconnectedto
asuitableearthelectrode.

29. Earth Leakage Circuit Breaker (ELCB):

30. •AnELCB (Earth Leakage Circuit Breaker)is an electrical safety device
used to directly detect currents leaking to earth from an installation
and interrupt the power supply.
•Types
•ELCBs are two types.
•Voltage Earth Leakage Circuit Breaker (Voltage ELCB).
•Current Earth Leakage Circuit Breaker (Current ELCB).

31. •CurrentEarthLeakageCircuitBreaker
•ThecurrentELCBisacircuitbreakerthatiscommonlyused.Itisalso
calledRCCB(ResidualCurrentCircuitBreaker).
•PrincipleofOperation
•TheCurrentELCB(orRCCB)consistsofathreewindingtransformer,
whichhastwoprimarywindingsandonesecondarywinding.Itis
calledtheCoreBalanceCurrentTransformer(CBCT).
•Phaseandneutralwiresactasthetwoprimarywindings.Awire-
woundcoilisthesecondarywinding.

32. •Atthebalancedcondition,thecurrentthroughthesecondarywinding
iszero.Forexample,ifthephasewirecarries5Ameanssame5A
currentwillbereturnedtotheneutralwirealso.
•Thesumofthecurrentiszero.Itisthenormalstate,inwhichthe
currentELCBdoesn’tgetoperated.Nowconsiderahumantouchinga
phasewire,itcausescurrenttopassfromphasetoearth.
•Nowphasecarries5A(normalload)plus30mAoffaultcurrent.But
ourneutralwirecarriesa5Acurrent.
•Thereisadifferenceof30mAofcurrent.ItissensedbytheCBCT
(CoreBalancedCurrentTransformerandsendtotherelayoperating
coils.

33. •Whenafaultoccurs,asmallamountofcurrentwillflowtotheground
also.Thismakesanunbalancebetweenphaseandneutralcurrentsand
createsanunbalancedmagneticfield.
•Thisinducesacurrentacrossthesecondarywinding,whichisconnectedto
thesensingcircuit.Thiswilldetectfaultcurrentsandsendasignaltothe
trippingsystemandtripsthecontact.
•Advantages
•Voltage-operated ELCB is less sensitive to fault conditions, therefore has
fewer nuisance trips.
•They do not detect faults that are don’t pass current through the circuit
protective conductor (CPC) to the earth rod.
•Current operated ELCB is not affected by parallel earth.
•Disadvantages
•Voltage-based ELCB devices are not used in the present days due to their
drawbacks as if the fault is between phase and circuit earth, they will
isolate the supply.

34. MCCB (Molded Case Circuit Breaker) –
Construction, Types & Working
•WhatisMCCB?
•MoldedCaseCircuitBreakerorMCCBisanautomaticelectrical
device.Itisatypeofcircuitbreakerthatprotectsthecircuitfrom
overloading,shortcircuitandcurrentsurges.Itisanadvancedversion
ofminiaturecircuitbreakerMCBsinceitoperateslikeone.However,
itoffersextrafeaturesthatmakeitasuperiorcircuitbreakersuchas
remoteclosingandadjustabletripsettingsi.e.itscurrentsettingsand
timesettingscanbeadjustedaccordingtoourneeds.

35. •MCCBisusedtoprotectthelowvoltagedistributionsystem.Itisavailable
inratingupto2500Ampsand1.1kV.
•ConstructionofMoldedCaseCircuitBreaker
•AnMCCBismadefromthefollowingmainpartseachoneexplainedin
detail
•Arcchute
•Contacts
•Operatingmechanism
•TerminalConnector
•ThermalTripUnit
•MagneticTripUnit
•Handle/Trip-freeMechanism
•TripButton

37. •BelowisthebriefdetailsofeachmechanismusedinatypicalMCCB.
•ArcChute
•Arcchuteisasetofparallelmetalplatesthataremutuallyinsulatedfrom
eachother.ithelpsinextinguishingthearcbysplittingthearcand
lengtheningit.itisalsoknownasanarcdividerorarcsplitter.Theseplates
aremadeofferromagneticmaterial.
•Contacts
•Contactsarethemetallicconductorsthatareresponsibleforcarryingthe
currenttotheload.Therearetwotypesofcontactsi.e.fixedandmoving
contact.Thecontactsaremadeofarcresistancematerialhavinglow
resistivityandcorrosion.Thequalityofthematerialdecidesthelifetimeof
thecircuitbreaker.
•OperatingMechanism
•ItisthemechanismofMCCBresponsibleforopeningandclosingthe
current-carryingcontacts.itisconnectedwithtripunitthattriggersthe
operatingmechanism.Thetripunitoperatesonathermalandmagnetic
mechanism.

38. •TerminalConnector
•TheterminalconnectorsareusedtoconnecttheMCCBtotheexternal
circuit.Theupperterminalsareconnectedtotheoutput/loadwhilethe
bottomterminalsareconnectedtotheinput/supply.Althoughtheyare
bidirectional,theinputandoutputdesignationisduetotheirphysical
installation
•TripUnit
•Itistheunitresponsibletotriggertheoperatingmechanism.Thetripunit
includesathermalmechanismforoverload,magnetictrippingforshort
circuitsandatestbuttonfortesting.
•ThermalTripUnit
•Thethermaltripunitusesathermalmechanismthatisabimetallicstrip
thatbends(andopensthecontacts)whenthetemperaturerisesduetothe
overloading.

39. •MagneticTripUnit
•Themagnetictripunithasarelaythatgeneratesamagneticfieldwhen
highercurrentsflowthroughitssolenoidduetotheshortcircuit.ittrips
thecircuitbreaker.Whilethetestbuttonisusedtosimulatetheabove-said
mechanismsandtesttheresponseofthecircuitbreaker.
•Handle/Trip-freeMechanism
•Itisahandleusedtoopenorclosethebreakermanually.Itisalsoknown
asatrip-freemechanismbecauseitwilltripevenifthehandleisheldin
ONposition.
•Thehandlecouldbeineitherthreepositionsi.e.upward,middleor
downward.Ifthehandleisinupwardposition,itisONposition.Ifitisin
themiddleposition,thebreakerhasbeentrippedwhilethedownward
positionshowsOFFstatus.
•TripButton
•Thetripbuttonisusedfortestingthebreaker.Itisared-coloredbutton
thattripstheoperatingmechanismwhenpushed.

40. Working Principle of MCCB
•OverloadProtection
•Overloadoccurswhenthecurrentexceedsalimitforaprolongedduration.
MCCBhasathermalmechanismthatcontainsabimetalliccontactto
protectfromoverload.Abimetallicstripismadefromtwodifferenttypes
ofmetalhavingdifferentratesofthermalexpansion.Upontemperature
change,thestripbendsorcontracts.
•Themaincurrentpassesthroughthebimetallicstrip.Ifthecurrentexceeds
acertainlimit,thecontactsheatupandexpand.Duetodifferent
expansionrates,thestripbendsandtripsthecircuit.
•Inelectricaldevices,thecurrentcanoverloadforshortdurationsoftime,it
isnormalandshouldnotbeconsideredasfaultcurrent.Therefore,MCCB
hasatimedelaythatallowstheoverloadcurrentforashortdurationof
timebeforetrippingthecircuit.

41. •ShortCircuitProtection
•MCCBprotectsagainstashortcircuitsusingasolenoidthatproduces
electromagneticforce.Themaincurrentflowsthroughthesolenoid
thatattractsandrepelsaplungerresponsiblefortrippingthebreaker.
•Ifthecurrentremainsbelowthethreshold,thesolenoidproducesa
weakmagneticforcethatcannotattracttheplunger.Inshortcircuit
conditions,averyhighcurrentflowsthroughthesolenoidthat
generatesaverystrongmagneticforce.Itattractstheplungerthat
tripsthecircuit.

42. •Advantages andDisadvantagesof MCCB
•Advantages
•MCCB has an adjustable trip setting that allows it to be used for low
as well as large currents
•It can handle a very large current.
•It can instantly interrupt very large currents.
•It has a movable trip unit.
•It has a very small tripping time thus fast switching during fault
current.
•It also offers a remote ON/OFF feature.
•It has a compact design and takes less space.

43. •Disadvantages
•MCCBisnotsuitableforhighvoltageapplications.
•Theyarenotsuitablefordomesticapplications.
•ApplicationsofMCCBs
•SinceMCCBcanhandleveryhighcurrents,theyareusedforheavy-dutyapplicationssuchasinindustries.
•AdjustableTripSettings:MCCBissuperiortoMCBandhasmoreapplicationduetoitshighercurrent
handlingandadjustabletripsettingcapabilities.Itmakesitversatiletobeusedforhighaswellaslow
currentsettings.
•MotorProtection:MCCBisusedinindustriestoprotectlargeelectricalmotorsfromoverloading.Itoffers
adjustabletripsettingstotoleratethehighinrushcurrentwithnecessarydelay.
•WeldingMachineProtection:WeldingmachinesdrawaverylargeamountofcurrentthatanMCBcannot
handle.Therefore,MCCBisusedforweldingmachines.
•ElectricFeedersProtection:Duetoitsadjustablesettingandhighcurrenthandling,itisusedinelectric
feederstodistributePowerbecauseitcarrieshundredsofampsthatanormalMCBcannothandle.
•GeneratorProtection:Theyarealsousedforprotectionoflargegeneratorthatgenerateshundredsofamps.
•CapacitorBankProtection:Capacitorbankisusedforpowerfactorcorrection.MCCBisalsousedforits
protectionagainsthighcurrents.

44. WiresandCables:
Wire:A wire is made of a single electrical conductor
Domestic & small industry wiring applications
Cables:A cable is a group or bundle of multiple wires inside a common sheathing.
Small and big industries Distribution and Transmission system
Wires
Cable
https://www.electricaltechnology.org/2020/04/types-wires-cables.html

45. TypesofWires:
Therearemainly5typesofwires:
1.Vulcanised Indian rubber wires(V.I.P)
2.Cab type sheathed wires(C.T.S)
3.Poly Vinyl Chloride wires(P.V.C)
4.Tough rubber sheath (T.R.S)
5.Flexible Wires

46. Vulcanised Indian rubber wires(V.I.R)

48. Cab type sheathed wires(C.T.S)

62. Electrical Safety precautions in handling electrical appliances:
Switch off all plugs when not in use.
Be careful while using a water heater.
Electric geysers should be switched off when not in use.
Oven and microwave should not be left running with out supervision.
Always handle electric appliances with dry hands.
Do not use a hair dryer in the bathroom.
Do not cut and make adjustments to electric cords.
Switch off all electric supply when on a vacation

63. Electric shock
Anelectricshockoccurswhena
personcomesintocontactwithan
electricalenergysource.Electrical
energyflowsthroughaportionof
thebodycausingashock.
Exposuretoelectricalenergymay
resultinnoinjuryatallormay
resultindevastatingdamageor
death.

64. What are the causes of electric shock?
•Contact with a powerline or electrical arc flash
•Accidental contact with exposed electrical sources
•Faulty electrical wiring, installations and repairs
•Contact with metal, growing vegetation, or other conductive material exposed to electrical
current, such as a metal ladder that touches a powerline or other exposed wire
•Accidental contact with a downed power line, or with the earth near a downed powerline
•Shock from faulty or unprotected electrical products, such as household appliances (e.g., hair
dryers and toasters), power tools, medical devices, outlets, electrical plugs and extension cords
•Three-prong-to-two-prong grounded plug adapters
https://www.electrocuted.com/2019/09/11/electric-shock-what-is-it-causes-symptoms-treatments-safety/

66. Electric shock

67. First aid for electric shock
1.Thefirststepistoseparatethepersonfromthesourceofelectricityasquicklyas
possible.Thebestwayofdoingthisistoturnoffthesupply,forexample,by
unpluggingtheapplianceorbyturningthemainsoffatthefusebox(consumerunit).
2.Ifthisisn’tpossible,thentrytoremovethesourceofelectricityfromthepersonusing
apieceofinsulatingmaterial,suchasalengthofwood.
3.NEVERtouchthepersonreceivingtheelectricshock,oryoucouldsufferonetoo.
4.Afterremovingthepersonfromthesourceofelectricity,ifthepersonis
unconsciouscallforanambulanceimmediately.Onlythosewiththenecessary
knowledgeandskillshouldcarryoutfirstaid.

68. 5.Wherethepersonisconsciousandseemswell,itisstilladvisabletomonitor
theircondition,astheeffectsofanelectricshockmaynotbeimmediately
obvious.Inworstcaseconditions,anelectricshockmayleadtoacondition
knownaselectroporation,wherecellswithinthebodyrupture,leadingtotissue
death.Additionalproblemsmightincludedeep-seatedburns,muscledamage
andbrokenbones.
6.DoCPR(CardiopulmonaryResuscitation),ifNecessaryWhenyoucansafelytouchthe
person,doCPRifthepersonisnotbreathingordoesnothaveapulse.

70. Electrical Safety Rules:
1.AvoidcontactwithenergizedelectricalcircuitsPleasedon’tmakefunofthis
ruleifyoualreadyknowthis(andyouprobablyalreadyknowifyouare
readingtheselines)andrememberthatifsomethingbadoccurs–you
probablywon’thavesecondchance.That’snotfunny.
2.Treatallelectricaldevicesasiftheyareliveorenergize.Disconnectthe
powersourcebeforeservicingorrepairingelectricalequipment.
3.Useonlytoolsandequipmentwithnon-conductinghandleswhenworkingon
electricaldevices.

71. 4.Neverusemetallicpencilsorrulers,orwearringsormetalwatchbands
whenworkingwithelectricalequipment.Thisruleisveryeasytoforget,
especiallywhenyouareshowingsomeelectricalpartpointingwith
metallicpencil
5.Whenitisnecessarytohandleequipmentthatispluggedin,besurehands
aredryand,whenpossible,wearnonconductivegloves,protectiveclothes
andshoeswithinsulatedsoles.

72. 6.If it is safe to do so, work with only one hand, keeping the other hand at
your side or in your pocket, away from all conductive material. This
precaution reduces the likelihood of accidents that result in current passing
through the chest cavity.
7.If you ever read about current passing through human body you will know,
so remember –work with one hand only.
8.Minimize the use of electrical equipment incold roomsor other areas
wherecondensationis likely. If equipment must be used in such areas,
mount the equipment on a wall or vertical panel

73. 9.If water or a chemical is spilled onto equipment, shut off power at the main switch
orcircuit breaker and unplug the equipment.
Very Logical : NEVER try to remove water or similar from equipment while
energized. Afterall, it’s stupid to do so.
10.If an individual comes in contact with a live electrical conductor, do not touch
theequipment, cord or person. Disconnect the power source from the circuit breaker or
pullout the plug using a leather belt.
Tricky situation, and you must be very calm in order not to make the situation even
worse.
https://electrical-engineering-portal.com/21-safety-rules-for-working-with-electrical-equipment