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LECTURE 03LECTURE 03
Service and UtilizationService and Utilization
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GENERATING STATION
Secondary Customer 240 V
Subtransmission Customer11kV
Subtransmission Customer33kV
TRANSMISSION TOWER550 kV, 275 kV
SUTSDT
GENERATION
TRANSMISSION
DISTRIBUTION
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IntroductionIntroduction
The service tab may be a connection on a poleThe service tab may be a connection on a polewith the overhead service drop or anwith the overhead service drop or an
underground service lateral to the building, or aunderground service lateral to the building, or a
connection to an underground utility line with aconnection to an underground utility line with aservice lateral to the building. All electricalservice lateral to the building. All electrical
construction work on private property isconstruction work on private property is
normally at he owners expenses, and fornormally at he owners expenses, and for
installation outside of private property normallyinstallation outside of private property normallybared by electric utility company (TNB) withbared by electric utility company (TNB) with
some contribution charges.some contribution charges.
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Service from the utility line to the building now daysService from the utility line to the building now daysrun underground except rural area where overheadrun underground except rural area where overhead
line is using due to certain constrain.line is using due to certain constrain.
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DistributionDistribution
TNB Sub
Station
Main Switch
Room
Sub Switch
Board
Distribution
Board/Panel
Transformer
RMU
Breaker
TNB CONSUMER
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DB
MAIN
SWITCHBOARD
SS
DP
DP
M
M
TRANSFORMER
HIGH VOLTAGE
PRIMERY
FEEDER
11,000 V
SECONDARY
SERVICE 415 V
MAIN FEEDER
415 V
BRANCH CIRCUITWIRING 415 V/240 V
STARTER PANEL
MOTOR
STARTER PANEL
SINGLE LINE DIAGRAM
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SCHEMATIC
DIAGRAM
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Overhead ServicesOverhead Services
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Overhead services are commonly used to carryOverhead services are commonly used to carry
two types of electric power lines, transmissiontwo types of electric power lines, transmissionlines @lines @ subtransmissionsubtransmission lines and distributionlines and distribution
lines (also known as feeder). Distribution lineslines (also known as feeder). Distribution lines
carry power from local substation to customers.carry power from local substation to customers.
They generally carry voltages from 4.6 to 11They generally carry voltages from 4.6 to 11
(kV) for distances up to thirty miles, and include(kV) for distances up to thirty miles, and include
transformers to step the voltage down from thetransformers to step the voltage down from the
primary voltage of the lines to the lowerprimary voltage of the lines to the lowersecondary voltage used by the customersecondary voltage used by the customer
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A service drop carries this lower voltage to theA service drop carries this lower voltage to the
customer's premises.customer's premises. SubtransmissionSubtransmission lineslinescarry higher voltage power from regionalcarry higher voltage power from regional
substations to local substations. They usuallysubstations to local substations. They usually
carry 66 kV for distances up to 60 miles.carry 66 kV for distances up to 60 miles.
Voltages of 230kV can be placed on twoVoltages of 230kV can be placed on two-- oror
threethree--pole towers. Transmission lines carryingpole towers. Transmission lines carrying
voltages of above 230kV are usually notvoltages of above 230kV are usually not
supported by poles, but by metal pylon (knownsupported by poles, but by metal pylon (knownas transmission towers).as transmission towers).
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For economic or practical reasons, such as toFor economic or practical reasons, such as to
save space in urban areas, a distribution line issave space in urban areas, a distribution line isoften carried on the same poles as aoften carried on the same poles as a
subtransmissionsubtransmission line but mounted under theline but mounted under the
higher voltage lines; a practice calledhigher voltage lines; a practice called
""underbuildunderbuild".".
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OverheadOverhead
AdvantagesAdvantages
Low costLow cost in generalin general Space ConstrainSpace Constrain
Limited accessibilityLimited accessibility
Easy InstallationEasy Installation
Shorter installation timeShorter installation time
Overhead cable are in several types;Overhead cable are in several types;
barebare
WeatherproofWeatherproof
Preassemble aerial cablePreassemble aerial cable consist three or fourconsist three or four
insulated cables wrapped together.insulated cables wrapped together.
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Overhead DistributionOverhead Cable
Aerial Cable
ABc Cable
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Underground ServicesUnderground Services
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Electric power can also be transmitted byElectric power can also be transmitted by
underground power cable instead of overheadunderground power cable instead of overhead
power lines. They can assist the transmission ofpower lines. They can assist the transmission ofpower across:power across:
Densely populated urban areasDensely populated urban areas
Areas where land is unavailable or planningAreas where land is unavailable or planning
consent is difficultconsent is difficult
Rivers and other natural obstaclesRivers and other natural obstacles
Land with outstanding natural or environmentalLand with outstanding natural or environmental
heritageheritage Areas of significant or prestigious infrastructuralAreas of significant or prestigious infrastructural
developmentdevelopment
Land whose value must be maintained for futureLand whose value must be maintained for future
urban expansion and rural developmenturban expansion and rural development
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Some other advantages of underground powerSome other advantages of underground power
cables:cables:
oo Less subject to damage from severe weatherLess subject to damage from severe weatherconditions (mainly lightning, wind and freezing)conditions (mainly lightning, wind and freezing)
ooGreatly reduced emission, into the surroundingGreatly reduced emission, into the surrounding
area, of electromagnetic fields (EMF). All electricarea, of electromagnetic fields (EMF). All electric
currents generate EMF, but the shielding providedcurrents generate EMF, but the shielding providedby the earth surrounding underground cablesby the earth surrounding underground cables
restricts their range and power.restricts their range and power.
ooUnderground cables need a narrower surroundingUnderground cables need a narrower surrounding
strip of about 1strip of about 110 meters to install, whereas an10 meters to install, whereas anoverhead line requires a surrounding strip of aboutoverhead line requires a surrounding strip of about
2020200 meters wide to be kept permanently clear200 meters wide to be kept permanently clear
for safety, maintenance and repair.for safety, maintenance and repair.
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ooUnderground cables pose no hazard to low flyingUnderground cables pose no hazard to low flying
aircraft or to wildlife, and are significantly safer asaircraft or to wildlife, and are significantly safer as
they pose no shock hazard (except to the unwarythey pose no shock hazard (except to the unwary
digger).digger).
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Some disadvantages of underground powerSome disadvantages of underground power
cables:cables:
ooUndergrounding is more expensive, since the costUndergrounding is more expensive, since the costof burying cables at transmission voltages is severalof burying cables at transmission voltages is several
times greater than overhead power lines, and thetimes greater than overhead power lines, and the
lifelife--cycle cost of an underground power cable is twocycle cost of an underground power cable is two
to four times the cost of an overhead power line.to four times the cost of an overhead power line.ooWhereas finding and repairing overhead wireWhereas finding and repairing overhead wire
breaks can be accomplished in hours, undergroundbreaks can be accomplished in hours, underground
repairs can take days or weeks, and for this reasonrepairs can take days or weeks, and for this reason
redundant lines are run.redundant lines are run.oo The principal disadvantages of this service is highThe principal disadvantages of this service is high--
cost and to overcome this direct buried technique iscost and to overcome this direct buried technique is
usedused eliminating the raceway, But, problem of thiseliminating the raceway, But, problem of this
technique is; cables cannot be pulled out if it is fault.technique is; cables cannot be pulled out if it is fault.
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Underground WiringUnderground Wiring
Exterior installation are generally in connectionExterior installation are generally in connectionwith servicewith service either directly from the utility or aeither directly from the utility or a
subfeedsubfeed between buildings . The methodsbetween buildings . The methods
available for underground wiring are:available for underground wiring are:oo direct burialdirect burial
oo TrenchTrench direct burial ductdirect burial duct
oo TrenchTrench concrete encased ductconcrete encased duct
Armored cable with 4 core, 3 core or singleArmored cable with 4 core, 3 core or single
core cable normally used for undergroundcore cable normally used for underground
wiringwiring..
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TrenchTrench
Trench - Direct Burial Duct
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TrenchTrench
Trench Concrete encased
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