Distribution System

Substation, Distribution

1. K.S.R. POLYTECHNIC COLLEGE
TIRUCHENGODE 637 215
DISTRIBUTION AND UTILIZATION
Department of Electrical and Electronic Engineering
V A KUPPUSAMY, M.E., MISTE.,
Sr. Lecturer / EEE
K.S.R. POLYTECHNIC COLLEGE
TIRUCHENGODE –637 215
Prepared by
DISTRIBUTION
Unit -I

2. DISTRIBUTION
UNIT –I

3. SUB –STATION
•Theelectricalpowerisgenerated,transmitted
anddistributedintheformofalternating
current.
•Electricalpowerisproducedatthepower
houseswhicharefarawayfromtheconsumers.
•Itisdeliveredtotheconsumersthroughalarge
networkoftransmissionanddistribution.
•Atmanyplacesinthelineofthepowersystem,
itisdesirableandnecessarytochangesome
characteristicsofelectricsupply.
•Thisisaccomplishedbysuitableapparatus
calledsub-station.
INTRODUCTION
Sub -Station 3

4. SUB –STATION
Sub -Station 4
•Theassemblyofapparatususedtochangesome
characteristic(voltage,actodc,frequency,p.fetc)
ofelectricsupplyiscalledsubstation.
•Sub-stationsareimportantpartofpowersystem.
Thecontinuityofsupplydependsuponthe
successfuloperationofsub-stations.Thefollowing
aretheimportantpointstobeconsideredwhile
layingoutasub-station.
•Itshouldbelocatedatapropersitei.e.,attheload
centre.
•Itshouldprovidesafeandreliablearrangement.
•Thecapitalcostshouldbeminimum..

5. Classification of Sub –Station
•Sub stations may be classified according to
•Service requirement.
•Constructional features (or) design.
1. According to Service requirement
•A sub-station may be called upon to change voltage level or improve
power factor or convert a,cpower into d.cpower etc. according to the
service requirement substations may be classified into.
Sub -Station 5

6. a) Transformer sub-station
•Thesubstationwhichchangethe
voltagelevelofelectricalsupplyare
calledtransformersubstations.
•Thesesubstationsreceivepowerat
somevoltageanddeliveritatsome
othervoltage.
•Transformerwillbethemain
componentinsuchsubstations.
•Mostofthesub-stationsinthepower
systemareofthistype.
Sub -Station 6

7. b) Switching sub-station
•Thesesubstationdonotchangethe
voltagelevelieincomingand
outgoinglinehavethesamevoltage.
•Howevertheysimplyperformthe
switchingoperationsofpowerlines.
Sub -Station 7

8. c) Power factor correction sub-station
•Thesesubstationimprovethepower
factorofthesystem.
•Suchsubstationaregenerallylocated
atthereceivingendoftransmission
lines.
•Inthesesubstations,synchronous
condensersareusedforpowerfactor
improvement.
Sub -Station 8

9. d) Frequency changer sub-station
•Thesubstationwhichchangethe
normalsupplyfrequencyarecalled
frequencychangersubstationsucha
frequencychangemayberequiredfor
industrialutilisation.
Sub -Station 9

10. f) Industrial sub-station
•Bigindustrialconsumerneedbulk
power.Thesubstationwhichsupply
powertoindividualindustrial
concernsareknownasindustrialsub
station.
Sub -Station 10

11. 2. According to construction features
•Asubstationhasmanycomponentslikecircuitbreakers,switches,
fuses,instrumentsetc.
•Thesecomponentsmustbehousedproperlytoensurecontinuousand
reliableservice.
•Accordingtoconstructionalfeatures,thesubstationsareclassifiedas,
a.Indoor sub station.
b.Outdoor sub station.
c.Under ground sub station.
Sub -Station 11

12. a. Indoor sub station
•Inthesesubstationsallthe
equipment'sareinstalledwithinthe
substationbuildings.Thesesub
stationsareusuallydesignedfora
voltagerangeof11KV,33KV,and
66KV.
Sub -Station 12

13. b. Outdoor sub station
•Forvoltagebeyond66KVequipment's
areinstalledoutdoor.Itisbecausefor
suchvoltagestheclearancesbetween
conductorsandthespacerequiredfor
switches,circuitbreakersandother
equipmentbecomessogreat.
•Henceinthesesubstationallthe
equipment'saremountedinoutdoor.
•Outdoorsubstationsarefurther
classifiedintopolemountedsubstation
andfoundationmountedsubstation.
Sub -Station 13

14. a. Pole mounted substation
•Thisisanoutdoorsubstationwith
equipmentinstalledoverheadonH-pole
orA-polestructure.Itisthecheapest
formofsubstationforvoltagesnot
exceeding11KV.
•Inpolemountedsubstations,upto
100KVAcapacitytransformersare
used.
Sub -Station 14

15. b. Foundation mounted substation
•Inthesesubstationsabove100KVA
transformersaremountedovera
concretefoundation.
•Suitablefencesarearrangedforsafety.
Sub -Station 15

16. Underground substation
•Inthicklypopulatedareas,thespace
availableforequipmentandbuildingis
limitedandthecostoflandishigh.
•Undersuchsituations,thesub-stationis
arrangedintheunderground.
Sub -Station 16

17. Gas Insulated substation
•AGasinsulatedsubstationisan
electricalsubstationinwhichthemajor
structuresarecontainedinasealed
enclosurewithSF
6gasasinsulating
medium.
•Highvoltageconductor,switchgears,
instrumenttransformers,thebusbar
andallotherequipmentarehousedin
metalenclosures.
•FilledwithSF
6gasat4to6timesthe
atmosphericpressure.
Sub -Station 17

18. 11KV / 400V Distribution Substation
Sub -Station 18

19. SUB –STATION EQUIPMENT
•The equipment required for a transformer sub-station depends upon
•The type of sub-station
•Service requirement.
•The degree of protection required.
•A transformer sub –station has the following main equipment's.
•Bus Bar.
a)Single bus-bar arrangement.
b)Single bus-bar system with sectionalisation.
c)Double bus-bar arrangement.
Sub -Station 19

20. Bus -Bars
•Bus-bars are copper or aluminium bars and
operate at constant voltage.
•The incoming and outgoing lines in a sub-
station are connected to the bus-bars.
•The most commonly used bus-bar
arrangements in sub-station are:
•Single bus-bar arrangement.
•Single bus-bar system with sectionalisation.
•Double bus-bar arrangement.
•Number of lines operating at the same voltage have to be directly connected
electrically, bus bars are used as the common electrical component.
Sub -Station 20

21. Insulators
•The most commonly used material for the
manufacture of insulator is porcelain.
•There are several type of insulator (eg. Pin
type, suspension type, post insulator etc.)
•Their use in the sub-station will depend upon
the service requirements.
•The insulators serve two purposes. They support the conductors and provide
necessary insulation between conductors and supports to avoid leakage
current.
Sub -Station 21

22. Isolators
•Thisisaccomplishedbyanisolating
switchorisolator.
•Anisolatorisessentiallyaknifeswitch.It
isdesignedtoopenacircuitunderno
load.
•Thatisisolatorswitchesareoperated
whennocurrentflowsinthelineinwhich
itisconnected.
•Itisoftendesiredtodisconnectapartof
thesystemforgeneralmaintenanceand
repairs.
Sub -Station 22

23. Lightning arrestor
•In order to protect transmission line, transformer and other equipment from
lighting arrestors are used.
Sub -Station 23

24. Circuit Breaker
•Itissodesignedthatitcanbeoperated
manually(orbyremotecontrol)under
normalconditionsandautomatically
underfaultconditions.
•Forautomaticoperation,arelaycircuitis
usedwithacircuitbreaker.
•Equipmentwhichcanopenorclosea
circuitundernormalaswellasfault
conditions.
Sub -Station 24

25. Power Transformers
•Usedinasubstationtostep-uporstep-
downthevoltage.Exceptatthepower
station,allthesubsequentsubstationsuse
step-downtransformerstogradually
reducethevoltage
Sub -Station 25

26. Instrument Transformers
•Operateathighvoltagesandcarrycurrent
ofthousandsofamperes.
•Measuringinstrumentsandprotective
devicesaredesignedforlowvoltages
(generally110V)andcurrents(about5A).
•Therefore,theywillnotwork
satisfactorilyofmounteddirectlyonthe
powerlines.
•Thisdifficultyisovercomebyinstalling
instrumenttransformersonthepower
lines.
a)Currenttransformer(C.T)
b)Potentialtransformer(P.T)
Sub -Station 26

27. Current Transformers (C.T)
•Acurrenttransformerisessentiallya
stepuptransformerwhichstepsdown
thecurrentinaknownratio.
•Theprimaryofthistransformer
consistsofoneormoreturnsofthick
wireconnectedinserieswiththeline.
•Thesecondaryconsistsofalarge
numberofturnsoflinewireand
providesforthemeasuringinstruments
andrelays.
Sub -Station 27

28. Potential Transformers (C.T)
•Itisessentiallyastepdown
transformerandstepsdownthe
voltageinaknownratio.
•Theprimaryofthistransformer
consistsofalargenumberofturnsof
finewireconnectedacrosstheline.
•Thesecondarywindingconsistsofa
fewturnsandprovidesfor
measuringinstrumentsandrelaysa
voltagewhichisaknownfractionof
thelinevoltage.
Sub -Station 28

29. Metering and Indicating Instruments
•Thereareseveralmeteringand
indicatinginstruments(e.gammeters,
voltmeters,energymeteretc.)installed
inasub-stationtomaintainwatchover
thecircuitquantities.
•Theinstrumenttransformersare
invariablyusedwiththemfor
satisfactoryoperation.
Sub -Station 29

30. Miscellaneous equipment
•Inadditiontoabove,thereare
followingequipmentinasubstation.
•Fuses.
•Carrier–currentequipment.
•Sub-stationauxiliarysupplies.
Sub -Station 30

31. Carrier current equipment
•Thisequipmentisinstalledinthesubstationsforcommunication,
relayingtelemeteringorsupervisorycontrol.
•Thisequipmentissuitablymountedinaroomknownascarrierroom
andconnectedtothehighvoltagepowercircuit.
Sub -Station 31

32. Substation Auxiliary supply
•Inadditiontotheabovementionedequipment’s,substationalsocontains
someauxiliaryequipment’sandcircuits.Theyare,
•Lightingintheswitchyard,controlrooms.
•Emergencylighting.
•Measuringinstruments.
•Relays.
•Tripcoilsandclosingcoils.
•Protectionsystem.
•ControlCircuits.
•Forgivingsupplytotheseequipmentsandcircuitsauxiliarysupply
systemisnecessary.
Sub -Station 32

33. Sub -Stationqassss 33

34. Sub -Station 34

35. Bus bars
•Thebusbarisabareconductor.
•Shapeisrectangular,square,roundtubesorsolidbars
•Madeupofaluminium.
•Mainconductorfromwhichanumberofconnections
aremade.
•Busbarsare5to6metersoflength.
•Aluminiumislessweightandcheaperandexcellent
corrosionresistance.
•Single bus-bar arrangement.
•Single bus-bar system with sectionalisation.
•Double bus-bar arrangement.
Sub -Station 35

36. Single bus-bar arrangement
•Asinglesetofbus-barisusedforthe
completegeneratingstation.
•Allthetransformers,generatorsandfeeders
wereconnectedtothissinglebusbar.
•Thegeneratorsareconnectedtobusbar
throughisolatorsandcircuitbreakers.
•Similarlytheoutgoingfeedersarealso
connectedtothebus-barthroughisolatorsand
circuitbreakers.
•ThistypeofarrangementisusedforD.C
stationsandsmallA.Cstations.
Sub -Station 36

37. Single bus-bar system with sectionalisation arrangement
•Asinglesetofbus-barisdividedinto
sections.
•Anytwosectionsofthebusbarareconnected
byacircuitbreakerandisolators.
•Ifafaultoccursonanysectionofthebus,that
sectioncanbeisolatedwithoutaffectingthe
supplyfromothersections.
•Alsorepairsandmaintenanceofanysection
ofthebus-barcanbecarriedoutbyde-
energisingthatsectiononly.
Sub -Station 37

38. Double bus-bar system
•Thissystemconsistsoftwobusbars,one
mainbusbarandanotherauxiliarybusbar.
•Theincomingandoutgoinglinesare
connectedtothetwobusbarsthroughcircuit
breakerandisolator.
•Atnormalcondition,theincomingand
outgoinglinesareconnectedtotheMainbus
bar,andtheauxiliarybusbariskeptas
reservebusbar.
•Incaseofrepairormaintenanceofmainbus
bar,thecontinuityofsupplytothecircuitcan
bemaintainedbytransferringthecircuittothe
auxiliarybusbar.
Sub -Station 38

39. Sectionalised Double bus-bar system
•Thisschemeauxiliarybusbarsareusedwith
thesectionalisedmainbusbar.
•Inthismethodofconnection,anysectionof
thebusbarcanbeisolatedformaintenance
work.
•Itwillbenotedthattheauxiliarybusbaris
notsectionalisedbecausethisisnotnecessary
andisexpensive.
Sub -Station 39

40. Ring bus-bar system
•Theendsofthebusbarsarereturnedtoform
aring.Inthissystemeachfeederissupplied
fromtwopaths.
•Byadopingthisschemeofconnections,the
alternatorsconnectedtoanyoneofthebus
barsectioncanbeusedforsupplyingtheload
tothefeedersonanysection.
Sub -Station 40

41. Distribution System
•Apartofpowersystemwhichdistributeselectricpowerfromthesubstationtotheconsumersis
knownasdistributionsystem.
Sub -Station 41
Requirements of Distribution System
•Aconsiderableamountofeffortisnecessarytomaintainanelectricpowersupplywithinthe
requirementsofvarioustypesofconsumers.
•Someoftherequirementsofagooddistributionsystemarepropervoltage,availabilityof
powerondemandandreliability.
1.ProperVoltage.
2.Availabilityofpowerondemand.
3.Reliability.
1.Interconnectedsystem.
2.Reliableautomaticcontrolsystem.
3.Providingadditionalreservefacilities.

42. Parts of Distribution System
•Adistributionsystemconsistsofthreemajorparts.TheyareFeeder,DistributorsandService
mains
Sub -Station 42
Feeder
•Whichconnectsthesubstationtotheareawhere
poweristobedistributed.
•Notappingsaretakenfromthefeeder.Thecurrent
initremainsthesamethroughout
•Mainconsiderationinthedesignoffeederisthe
currentcarryingcapacity.

43. Distribution System
•Adistributionisaconductorfromwhichtappingsaretakenforsupplyingtotheconsumers.
•AB,BC,CDandDAarethedistributors.
Sub -Station 43
•Thecurrentthroughadistributorisnotconstant
becausetappingsaretakenarvariousplacesalong
itslength.Whiledesigningdistributor,voltage
dropalongitslengthisthemainconsideration
sincethepermissiblelimitofvoltagevariationsis
±5%ofratedvalueattheconsumerterminals.
Service Mains
•Aservicemainisgenerallyasmallcablewhich
connectsthedistributortotheconsumerterminals.
Sub
Station
Ring Main Distributor
A B
D C
Service Mains

44. Classification of Distribution Systems
•Adistributionsystemmaybeclassifiedaccordingto
Sub -Station 44
1. Based on type of supply
a)D.Cdistributionsystem.
b)A.Cdistributionsystem.
2. Based on Character of service voltage
a)Lowtensiondistribution(LT)(400V).
b)Hightensiondistribution(HT)(11KV).
3. Based on type of construction
a)Overheaddistributionsystem.
b)Undergrounddistributionsystem.
4. Based on number of wires
a)Twowiredistribution.
b)Threewiredistribution.
c)Fourwiredistribution.
5. Based on Scheme of connection
a)Radialdistributionsystem.
b)Ringdistributionsystem.
c)Interconnecteddistributionsystem.

45. Various system of Power Distribution
•Thepowerisdistributionintwomethods.
•1.D.Csystem 2.A.Csystem
Sub -Station 45
1. D.C system
a)D.Ctwowire.
b)D.Ctwowirewithmidpointearthed.
c)D.Cthreewire.
2. A.C system
a)Single phase two wire.
b)Single phase two wire with mid point earthed.
c)Single phase three wire.
B. Two phase A.C system
a)Twophasefourwire.
b)Threephasethreewire.
C. Three phase A.C system
A. Single phase A.C system
a)Threephasethreewire.
b)Threephasefourwire.

46. Comparison of cost of conductors in A.C and D.C system
•Whilecomparingthecostofconductorsofvarioussystemsthefollowingassumptiontobe
made.
•Thepowertransmittedbyeachsystemissame.
•Thedistanceoverwhichthepowertransmittedissame.
•Thelinelossesinthesystemaresame.
•Themaximumvoltagesbetweenanyconductorandearthisthesameinallcases.
•Inthreewiresystem,theloadsshouldbebalanced.
Sub -Station 46

47. Sub -Station 47
D.C two wire system with one conductor earthed

48. Connection Scheme of Distribution System
•Alldistributionofelectricalenergyisdonebyconstantvoltagesystem.Inpracticethe
followingdistributioncircuitsaregenerallyused.
Sub -Station 48
1. Radial System
•Inthissystemseparatefeederradiatefromasingle
substationandfeedthedistributorsatoneend
only.
•Theradialsystemisemployedonlywhenpoweris
generatedatlowvoltageandthesubstationis
locatedatthecentreoftheload.

49. Sub -Station 49
2. Ring Main System
•Inthissystem,theprimariesofdistributiontransformersformaloop.Theloopcircuitstarts
fromthesubstationbus-bars,makesaloopthroughtheareatobeserved,andreturnstothe
substation.Thesinglelinediagramofringmainsystemfora.c.distributionwheresubstation
suppliestotheclosedfeederLMNOPQRS.
•Thedistributorsaretappedfromdifferentpoints
M,OandQofthefeederthroughdistribution
transformers.
Advantages
•Lessvoltagefluctuationsatconsumerterminals.
•Thesystemismorereliablebecauseeach
distributorisfedbytwofeeders.
•Intheeventoffaultonanysectionofthefeeder
thecontinuityofsupplyismaintained.

50. Sub -Station 50
3. Inter Connected System
•Whenthefeederringisenergisedbytwoormorethangeneratingstationsorsubstations,itis
calledinter-connectedsystem.Thesinglelinediagramofinterconnectedsystemwherethe
closedfeederringABCDissuppliedbytwosubstationsS
1andS
2atpointsDandC
respectively.
•DistributorsareconnectedtopointsO,P,Qand
Rofthefeederringthroughdistribution
transformers.
Advantages
•Itincreasestheservicereliability.
•Anyareafedfromonegeneratingstationduring
peakloadhourscanbefedfromtheother
generatingstation.Thisreducesreservepower
capacityandincreasesefficiencyofthesystem.

51. Sub -Station 51
1. A.C. DISTRIBUTION CALCULATIONS
A.C.distributioncalculationsdifferfromthoseofd.cdistributioninthefollowingrespects:
•Incaseofd.csystem,thevoltagedropisduetoresistancealone.However,ina.c.system,the
voltagedropsareduetothecombinedeffectsofresistance,inductanceandcapacitance.
•Inad.csystem,additionsandsubtractionsofcurrentsorvoltagesaredonearithmeticallybutin
caseofa.csystem,theseoperationsaredonevectorically.
•Inana.c.system,powerfactor(p.f.)hastobetakenintoaccount.Loadstappedoffformthe
distributoraregenerallyatdifferentpowerfactors.Therearetwowaysofreferringpower
factorviz.
1.Itmaybereferredtosupplyorreceivingendvoltagewhichisregardedasthereference
vector.
2.Itmaybereferredtothevoltageattheloadpointitself.
Thereareseveralwaysofsolvinga.c.distributionproblems.However,symbolicnotation
methodhasbeenfoundtobemostconvenientforthispurpose.Inthismethod,voltages,currents
andimpedancesareexpressedincomplexnotationandthecalculationsaremadeexactlyasind.c.
distribution.

52. Sub -Station 52
2. METHODS OF SOLVING A.C. DISTRIBUTION PROBLEMS
•Ina.c.distributioncalculations,powerfactorsofvariousloadcurrentshavetobeconsidered
Generallythepowerfactorsarereferredintwoways.
•Powerfactorreferredtoreceivingendvoltage.
•Powerfactorreferredtoloadvoltage.
i). Power factor referred to receiving end voltage
•Considerana.c.distributorABwithconcentrated
loadsofI
1andI
2tappedoffatpointsCandB.
•TakingthereceivingendvoltageV
Basthe
referencevector,
•letlaggingpowerfactorsatCandBbecosθ
1and
cosθ
2w.r.t.V
B.
•LetR
1,X
1andR
2,X
2betheresistanceand
reactanceofsectionsACandCBofthedistributor.

53. Sub -Station 53
•Impedance of section AC
=Z
AC=R
1+ jX
1
•Impedance of section CB
= Z
CB= R
2+ jX
2
•Load current at point C= I
1
I
1= I
1 (cos θ
1–j sin θ
1)
•Load current at point B = I
2
I
2= I
2 (cos θ
2–j sin θ
2)
•Current in Section CB = I
CB
I
2= I
2(cos θ
1–j sin θ
2)
•Current in Section AC = I
AC I
AC= I
1+ I
2
= I
1 (cos θ
1–j sin θ
1) + I
2 (cos θ
2–j sin θ
2)
•Voltage drop in Section CB, V
CB = I
CB. Z
CB
= I
2 (cos θ
2–j sin θ
2) (R
2–j X
2)
R
2 + jX
2R
1+ jX
1
I
1 cos θ
1
I
2 cos θ
2
BCA

54. Sub -Station 54
•Voltage drop in Section CB, V
CB = I
CB. Z
CB
= I
2 (cos θ
2–j sin θ
2) (R
2–j X
2)
•Voltage drop in Section AC, V
AC = I
AC. Z
AC
= [I
2 (cos θ
2–j sin θ
2)I
2 (cos θ
2–j sin θ
2)] (R
2–j X
2)
•Sending end Voltage V
A = V
B+ V
AC + V
CB
•Sending end Voltage I
A = I
1+ I
2
•Sending end Voltage V
A = cos θ
S

55. Sub -Station 55
I
2X
2
I
1
I
2
I
AC
α
θ
2
β
θ
s
θ
1
R
2 + jX
2R
1+ jX
1
I
1 cos θ
1
I
2 cos θ
2
BCA

56. ii) Power factor referred to respective load voltages
•Let the power factors of the loads are referred to their respective load voltages.
•Then ∅
1is the phase angle between V
Cand I
1and ∅
2is the phase
angle between V
Band I
2.
•The vector diagram under these conditions is shown.
•Voltage drop in section CB.
V
CB= I
2Z
CB= I
2(Cos∅
2–j Sin∅
2)(R
2 + jX
2)
•Voltage at point C= V
B+ drop in section CB
= V
C∠??????
Now I
1 = I
1∠−∅
1 w.r.t voltage V
C
I
1 = I
1∠−∅
1−??????w.r.t V
B
I
1 = I
1[cos ∅
1−??????-j sin ∅
1−??????]
Sub -Station 56
I
2X
2
I
1
I
2
I
AC
∅
2
∅
1
??????

57. ii) Power factor referred to respective load voltages
Now I
AC = I
1 + I
2
I
1 = I
1[cos ∅
1−??????-j sin ∅
1−??????]
+ I
2(Cos∅
2–j Sin∅
2)
Voltage drop in section AC= I
AC Z
AC
Voltage at point A = V
B+ Drop in CB + Drop in AC.
Sub -Station 57
I
2X
2
I
1
I
2
I
AC
∅
2
∅
1
??????

58. •Therefore,theneutralsareatthesamepotentialand
voltageacrosseachimpedanceissameandequalto
phasevoltagewhetherthecircuitisbalancedor
unbalanced.
•Thethreephasecurrentsorlinecurrentscanbe
determinedbydividingthephasevoltagebythe
impedanceoftheconcernedphases.
Sub -Station 58
3 –Phase, 4 wire Star –Connected Unbalanced Load circuits
I
B
I
Y
I
YI
B
I
R
B Y
R
I
N = I
R + I
Y+ I
B
I
R =
VP
ZP
B` Y`
R`
I
B
I
Y
V
P
i.e., I
R =
V
R
ZR
; I
Y =
V
Y
ZY
;I
B =
V
B
ZB
•In3phase,4wire,star-connectedloadcircuitsthestarpointsofloadandthegeneratoraretied
togetherthroughneutralwireofzeroimpedance.
•ThecurrentinneutralwirecanbedeterminedbyapplyingKirchhoff’sfirstlawatstarpointN.
AccordingwhichI
N+I
R+I
Y+I
B=0orcurrentinneutralwire,I
N=-(I
R+I
Y+I
B)

59. •Incaseofabalancedthree–phase,four–wiresystemwhentheneutralisdisconnected,no
changeisproduced.
•Butincaseofunbalanced3–phase,4–wiresystem,whentheneutralisdisconnected,theloads
whichareconnectedbetweenanytwoconductorsandtheneutralareconnectedinseriesand
potentialdifferenceacrossthecombinedloadbecomeequaltolinevoltage.Thepotential
differenceacrosseachloadisthuschangedasperratingoftheload.
Sub -Station 59
Consequence of Disconnection of Neutral in Three Phase Four wire system

60. Sub -Station 60