lec 03a#service utilization

8/7/2019 Lec 03a#Service Utilization

1/27

LECTURE 03LECTURE 03

Service and UtilizationService and Utilization


2/27

GENERATING STATION

Secondary Customer 240 V

Subtransmission Customer11kV

Subtransmission Customer33kV

TRANSMISSION TOWER550 kV, 275 kV

SUTSDT

GENERATION

TRANSMISSION

DISTRIBUTION


3/27

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.


4/27

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.


5/27

DistributionDistribution

TNB Sub

Station

Main Switch

Room

Sub Switch

Board

Distribution

Board/Panel

Transformer

RMU

Breaker

TNB CONSUMER


6/27

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


7/27

SCHEMATIC

DIAGRAM


8/27

Overhead ServicesOverhead Services


9/27

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


10/27

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).


11/27

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".".


12/27

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.


13/27

Overhead DistributionOverhead Cable

Aerial Cable

ABc Cable


14/27


15/27

Underground ServicesUnderground Services


16/27

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


17/27

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.


18/27

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).


19/27

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.


20/27

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..


21/27


22/27


23/27

TrenchTrench

Trench - Direct Burial Duct


24/27


25/27

TrenchTrench

Trench Concrete encased


26/27


27/27

lec 03a#service utilization

Documents