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Stesan
Kuasa
Penghantaran
Pengagihan
PenggunaUnit 2: TRANSMISSION
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Introduction
Penghantaran Pengagihan
TRANSMISSION DISTRIBUTION
Transmit from power plant
to distribution substationsDistribute from distribution
substations to end users.
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Transmission line
R L C
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What is Transmission line?
A transmission line is the material mediumor structure that forms all or part of a path
from one place to another for directing the
transmission of energy, such as
electromagnetic waves as well as electric
power transmission.
Components of transmission lines include
wires, coaxial cables, dielectricslabs,
optical fibres, electric power lines, and
waveguides.
http://en.wikipedia.org/wiki/Transmission_mediumhttp://en.wikipedia.org/wiki/Pathhttp://en.wikipedia.org/wiki/Transmission_%28telecommunications%29http://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Wirehttp://en.wikipedia.org/wiki/Coaxial_cablehttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Optical_fibrehttp://en.wikipedia.org/wiki/Waveguidehttp://en.wikipedia.org/wiki/Waveguidehttp://en.wikipedia.org/wiki/Optical_fibrehttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Coaxial_cablehttp://en.wikipedia.org/wiki/Wirehttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/Transmission_%28telecommunications%29http://en.wikipedia.org/wiki/Pathhttp://en.wikipedia.org/wiki/Transmission_medium -
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TransmissionSystem
Losses
4 type of power lines
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4 type of power lines:
1- Low Voltage (< 600 V)
2- Medium Voltage ( 2.4 kV to 69 kV)
3 -High Voltage (< 230kV)
4 - Extra High Voltage (800 kV, 1000
km)
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Losses
Some of the power that is fed into atransmission line is lost because of itsresistance.
This effect is called ohmicorresistiveloss(see ohmic heating). At high frequencies, another effect called
dielectric lossbecomes significant, addingto the losses caused by resistance.
Dielectric loss is caused when the insulatingmaterial inside the transmission lineabsorbs energy from the alternating electricfield and converts it to heat (see dielectricheating).
http://en.wikipedia.org/wiki/Ohmic_heatinghttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Dielectric_heatinghttp://en.wikipedia.org/wiki/Dielectric_heatinghttp://en.wikipedia.org/wiki/Dielectric_heatinghttp://en.wikipedia.org/wiki/Dielectric_heatinghttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Ohmic_heating -
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Losses (cont)
In an alternating current circuit, the inductance andcapacitance of the phase conductors can besignificant.
The currents that flow in these components of the
circuit impedance constitute reactive power, whichtransmits no energy to the load.
Reactive current flow causes extra losses in thetransmission circuit.
The ratio of real power (transmitted to the load) toapparent power is the power factor.
As reactive current increases, the reactive powerincreases and the power factor decreases.
For systems with low power factors, losses are higherthan for systems with high power factors.
http://en.wikipedia.org/wiki/Electric_power_transmission#Losses
http://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Reactive_powerhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Reactive_powerhttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Inductance -
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R,L,C in transmission line.
There are several term involves intransmission line such as resistance,capacitance and inductance calledparameter.
This parameters are not the samealong the lines and may effect the
efficiency of power transmissions. The effect may vary by length of
transmission lines.
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Component of a
transmission line
Schematic
representation of
the elementary
component of atransmission line.
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Component of a
transmission line (cont..)
The distributed resistance Rof the conductors is represented by aseries resistor (expressed in ohms per unit length).
The distributed inductance L (due to the magnetic field around thewires, self-inductance, etc.) is represented by a series inductor(henries per unit length).
The capacitance Cbetween the two conductors is represented by ashuntcapacitorC (farads per unit length). The conductance Gof the dielectric material separating the two
conductors is represented by a conductance G shunted betweenthe signal wire and the return wire (siemens per unit length).
*** The model consists of an infinite seriesof the elements shown in
the figure, and that the values of the components are specified perunit lengthso the picture of the component can be misleading. R, L,C, and Gmay also be functions of frequency. An alternativenotation is to use R', L', C' and G' to emphasize that the values arederivatives with respect to length.
http://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Self-inductancehttp://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Shunt_(electrical)http://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Shunt_(electrical)http://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Self-inductancehttp://en.wikipedia.org/wiki/Self-inductancehttp://en.wikipedia.org/wiki/Self-inductancehttp://en.wikipedia.org/wiki/Magnetic_field -
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Telegrapher's equations
The Telegrapher's Equations (or justTelegraph Equations) are a pair of
linear differential equations whichdescribe the voltage and current on
an electrical transmission line with
distance and time. They were
developed by Oliver Heaviside whocreated the transmission line model,and are based on Maxwell's
Equations.
http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Oliver_Heavisidehttp://en.wikipedia.org/wiki/Maxwell%27s_Equationshttp://en.wikipedia.org/wiki/Maxwell%27s_Equationshttp://en.wikipedia.org/wiki/Maxwell%27s_Equationshttp://en.wikipedia.org/wiki/Maxwell%27s_Equationshttp://en.wikipedia.org/wiki/Oliver_Heavisidehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Voltage -
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Classification oftransmission lines
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Classification of transmissionlines
Transmission lines are classifiedas short, medium and long.
When the length of the line is lessthan about 60km the effect ofshunt capacitance andconductance is neglected and the
line is designated as a shorttransmission line.
For these lines the operatingvoltage is less than 20KV.
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Short transmission line model
Vsn = Vm+ IR kos R + IX sin R.
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Short transmission line model(cont)
Vsn - Voltan pada penghujung
penghantaran
Vm - Voltan hujung penerima I - Arus beban pada R mengekor
R - Rintangan gelung ()
X - Kearuhan gelung ()
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S
RR
S
V
IRkosV
OC
OFkos
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Sebenarnya daripada rajah vektor ini bukan sahaja kita
dapat menentukan nilai VS dan faktor kuasa,
tapi kita juga dapat menentukan peratus pengaturan bagi
sebuah talian pendek dengan merujuk kepada parameter-parameter yang diberikan. Peratus pengaturan voltan
merujuk kepada Rajah 2.3 boleh ditulis sebagai.
Peratus Pengaturan =100
sinx
V
IXkosIR
S
RR
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Short Transmission Line
Short Transmission LineThe equivalent circuit and vector diagram of a shorttransmission line are shown in the figure given below.
In the equivalent circuit short transmission line is
represented by the lumped parameters R and L. R isthe resistance (per phase) L is the inductance (perphase) of the entire transmission line.
The effect of shunt capacitance and conductance isnot considered in the equivalent circuit.
The line is shown to have two ends : sending end(designated by the subscript S) at the generator, andthe receiving end (designated R) at the load.
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Performance of Transmission Lines
The performance of a power system ismainly dependent on the performance ofthe transmission lines in the system.
It is necessary to calculate the voltage,current and power at any point on atransmission line provided the values at onepoint are known.
The transmission line performance is
governed by its four parameters - seriesresistance and inductance, shuntcapacitance and conductance.
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Performance of TransmissionLines (CONT.)
All these parameters are distributed over the length ofthe line.
The insulation of a line is seldom perfect and leakagecurrents flow over the surface of insulators especially
during bad weather. This leakage is simulated by shunt conductance.
The shunt conductance is in parallel with the systemcapacitance.
Generally the leakage currents are small and the shuntconductance is ignored in calculations.
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Performance of TransmissionLines (CONT.)
Performance of transmission lines is meant thedetermination of efficiency and regulation of lines.
The efficiency of transmission lines is defined as:
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Performance of TransmissionLines (CONT.)
The end of the line where load is connected is called thereceiving end and where source of supply is connected iscalled the sending end.
The Regulation of a line is defined as the change in thereceiving end voltage, expressed in percent of full loadvoltage, from no load to full load, keeping the sendingend voltage and frequency constant.
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Classification oftransmission lines (cont)
Formedium transmission lines the length of the line isin between 60km - 150km and the operating linevoltage wil be in between 21KV-100KV.
In this case the shunt capacitance can be assumed to
be lumped at the middle of the line or half of the shuntcapacitance may be considered to be lumped eachend of the line.
The two representations of medium length lines aretermed as nominal-T and nominal- respectively.
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2. Medium transmission line
Vsn = Vm + Isn (R + jX).
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Lines more than 150km long and line
voltage above 100KV require calculations in
terms of distributed parameters.
Such lines are known as long transmission
lines.
This classification on the basis of length is
more or less arbitrary and the real criterionis the degree of accuracy required.
Classification oftransmission lines (cont)
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3. Long transmission line
Electronic Model of a Transmission Line
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Capacitance and inductance are associated with thephysical devices called capacitors and inductors used incircuits to create various types of filters.
Capacitance and inductance are also encounteredwhenever electricity is flowing in conductors. In this
situation, they are effectsrather than physical circuitelements.
Resistance, capacitance, and inductance are distributeduniformly along the length of a transmission line.
Capacitance is a parallel effect, inductance is a series effect,and resistance is both a series and parallel effect. The
parallel capacitance and resistance are called shuntcapacitanceand shunt resistance. All these characteristic effects are expressed on a per
distance basis, for example, farads per mile for shuntcapacitance.
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Talian terdiri dari beberapa parameter malar ialaiturintangan, kearuhan, kemuatan dan kealiran yang wujuddisepanjang pengagihan talian penghantaran yang panjang.
Rintangan (R) dan regangan beraruhan (X) merupakanelement siri dalam talian
pengehantaran. Rentetan kemuatan (B) dan kealiran bocor (G) merupankan
element pirau, kealiran bocor juga menyebabkankehilangan kuasa dalam talian. Ia berpunca daripadakebocoran penebatan atau kesan korona pada pengalir.
Arus bocor yang mengalir melalui lepasan pirau adalah
maksima pada hujung penghantaran talian penghantarandan berkurangan secara berterusan ketika menuju kehujung penerima dan akhirnya menjadi sifar setelah tiba kehujung talian penerima.
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Kesan-Kesan Voltanke atas Kecekapan
Penghantaran.
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ASSIGNMENT #1(B)
Terangkan:
Adakah peningkatan voltan dapat
meningkatkan kecekapan penghantaranbekalan kepada pengguna?
Adakah peningkatan voltan dapat
menjimatkan kos penghantaran bekalan
kepada pengguna?
Unit2/19
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Corona
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Corona discharge
Corona discharge is the creation ofions in afluid (such as air) by the presence of astrong electric field.
Electrons are torn from un-ionized air, andeither the positive ions or else the electronsare attracted to the conductor, whilst thecharged particles drift.
This effect can cause considerable power
loss, create audible and radio-frequencyinterference, generate toxic compoundssuch as oxides of nitrogen and ozone, andlead to arcing.
http://en.wikipedia.org/wiki/Corona_dischargehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Earth%27s_atmospherehttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Earth%27s_atmospherehttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Corona_discharge -
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Both AC and DC transmission lines can
generate coronas, in the former case in the
form of oscillating particles, in the latter a
constant wind.
Due to the space charge formed around the
conductors, an HVDC system may have
about half the loss per unit length of a high
voltage AC system carrying the same
amount of power.
http://en.wikipedia.org/wiki/Space_chargehttp://en.wikipedia.org/wiki/Space_charge -
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Corona is the physical manifestation ofenergy loss, and can transform dischargeenergy into very small amounts of sound,radio noise, heat, and chemical reactions ofthe air components.
Because power loss is uneconomical andnoise is undesirable, corona on
transmission lines has been studied byengineers since the early part of thiscentury.
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Factors influence the
corona.
Several factors, including:
voltage,
shape and diameter of conductor, and surface irregularities such as
scratches, nicks, dust, or water drops
can affect a conductors electricalsurface gradient and its corona
performance.
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CORONA AND INDUCED
CURRENT EFFECTS
Effects include:
audible noise,
radio, television and computer monitorinterference
gaseous effluents, shock potential.
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Overcome the corona
i). increase the conductor diameter
(example; by using ACSR).
ii). Use more than one conductor(bundle conductor)
iii). Increase the distance of
conductors, so the effect of magnetic
field will be reduced.
ALUMINIUM CONDUCTORS STEEL
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ALUMINIUM CONDUCTORS STEELREINFORCED (ACSR)
Available in a wide
range of steel
varying from as low
as 6% to as high as40%...
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http://encyclopedia2.thefreedictionary.com/Energy+transmission
Transmission lines use ACSR (aluminum cable, steelreinforced) and ACAR (aluminum cable, alloy reinforced)conductors.
In an ACSR conductor, a stranded steel core carries themechanical load, and layers of stranded aluminum surrounding
the core carry the current. An ACAR conductor is a stranded cable made of an aluminum
alloy with low resistance and high mechanical strength. ACSRconductors are usually used for high-voltage lines, and ACARconductors for subtransmission and distribution lines.
Ultrahigh-voltage (UHV) and extrahigh-voltage (EHV) lines usebundle conductors. Each phase of the line is built with two,
three, or four conductors connected in parallel and separated byabout 1.5 ft (0.5 m). Bundle conductors reduce coronadischarge
ALUMINIUM CONDUCTORS STEEL REINFORCED (ACSR)
ALUMINIUM CONDUCTORS
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ALUMINIUM CONDUCTORS
STEEL REINFORCED
This conductor consists of a solid or stranded steel coresurrounded by strands of aluminium (E.C. GRADE). ACSRconductor is available in a wide range of steel varying fromas low as 6% to as high as 40 %.
The higher strength ACSR conductors are used for river
crossings, overhead ground wires, installations involvingextra long spans etc. against any given resistance ofconductor, ACSR conductor may be manufactured forhaving a wide range of tensile strength as per requirement.
The principal advantage of these conductors are high tensilestrength and light weight with longer spans as well as withlesser supports. Due to the greater diameter of ACSRconductors a much higher corona limit can be obtainedcausing big advantages on high as well as extra highvoltage overhead lines.
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Recap
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Recap
Menakrifkan talian pendek, melakar rajah litar satu talian
pendek dan melabelkannya.
Menakrifkan talian sederhana, melakar rajah litar satu talian
pendek dan melabelkannya.
Menakrifkan talian panjang, melakar rajah litar satu talian
pendek dan melabelkannya.
Mentakrifkan pengaturan voltan.
Menakrifkan kecekapan penghantaran.