Chapter 2:Transmission Lines
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S te s a n
K u a sa
Power station
P e n g h a n ta r a n
Transmission
P e n g a g ih a n
Distribution
Figure 2.1 Transmission system in overhead line
P eng gu na
Consumer
2.1 Transmission system
Transmission system was one large system linking generation station to
users through distribution system. Transmission system supply large
amount of energy of generator station to burden centres. Distribution system
also will supply energy from transmission system and distribute to major
substation and small substation to the consumer.
Electricity can be supplied and distributed whether in alternating current
(A.C) or direct current (DC). In practical, 3 phase 3 line system applies in
transmission system meanwhile for 3 phase 4 line AC system applies in
distribution system. Figure 2.1 show transmission system in overhead line.
Important considerations in transmission line operation are referring to
voltage and lost power fall which occurred on-line and also transmission line
efficiency. Components such as R resistance, L inductance and C
capacitance found in transmission line influence that circumstances.
2.2 Short Line
Transmission line which possess long less than 60 kms and operating in
voltage rate under 20 kV categorised as short line in transmission system.
Refering to short distance and low operation voltage, then as a result of this
on-line fitness is also small then capacitance effect can be neglected in this
line system, such short line performance is depends on resistance and
inductance found in transmission line. In real transmission line, resistance
and inductance found all along that transmission line. But in line case short
amount of obstruction and inductance lumped at one place or part.
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Chapter 2:Transmission Lines
2.3 Resistance and Inductance in line
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Transmission line for electric circuit usually having a few parameter such as
resistance, inductance and capacitance. This parameter is not same all
along transmission line which affect to voltage regulation and also
transmission line efficiency. This effect also depends on some transmission
line length.
2.3.1 Series Resistance Conductor
Several factors should be taken into consideration such as line length,
diameter of the line, material and environmental temperature cross sectional
area.
Current flow in oppositional direction in its and this state is known as
resistance. R resistance in ohm formed in this transmission line refering to
long  and diameter a conductor and can be stated as ;
R= 

a
……(equation: 2.1)
Where  is resistance conductor.
Resistance of the conductor ()is not only depends to material used by
conductor but also depends to environmental temperature. Series
resistance’s value found in line can be pointed through following equation:If 1 and 2 is resistance value which correlated with temperature value t1
and t2 then,
2 = 1[1 + (t1 - t2)]
……(equation: 2.2)
Where  is coefficient for material's temperature used to design conductor.
Temperature coefficient’s value for resistance also not fixed but depends on
beginning temperature. Temperature coefficient for resistance rendered as;
= 0 / (1 + 0t1)
……(equation: 2.3)
where 0 is a temperature coefficient for resistance when 0C
Through equations which indicated can be concluded that resistance occur
in transmission conductor are continuously started of transmission line until
arrived to distribution line to users.
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Chapter 2:Transmission Lines
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2.3.2 Inductance
Conductor in transmission line system is not only have resistance even
inductance also exist on that line. If we refer to Figure 2.2(a), shows two
conductor single phase, note in separatist part both that conductor marking
by distance, D. When current flow through this two conductor at any time-it
will flow in opposite direction and further create field around both conductor.
This pole will be permanently giving pressure between one by another like
those portrayed on Figure 2.2(b). (see arrow of field movement).
+
-
γ
D
-
+
γ
D
(b)
(a)
Figure 2.2: Magnetic force vein induced between two conductor
Both conductor in figure 2.2(a) and 2.2(b), will form rectangle loop for each
round through live flux current flow result in both conductor. When flux
resultant this chain to that loop it will produce inductance. Although
separatist distance between this conductor is large about 1 metres to 10
metres, because existence this compact flux number will form larger coil and
influence inductance existence.
Inductance existence in conductor for each round per metre ( when γ ≤ D )
provable through equation as follows;
L

D i
loge


 4
henry / meter ……(equation: 2.4)
where,
μ = permeability absolute medium.
μi = permeability absolute conductor material.
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Chapter 2:Transmission Lines
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2.4 Short Line circuit diagram
R
X
I
I
Line
Vm
Vsn
Load
Neutral
Figure 2.3 Single line circuit of short line
Short transmission line could be identified briefly with draw a single line
circuit. Some components found on this line could be used to make
calculation to determine voltage efficiency and fall which occurred in short
line transmission system. Figure 2.3 shows a short line single line circuit.
Referring to figure 2.3, a few parameters could be identified namely,
Vsn Vm I
R X -
Voltage in transmission end
Voltage in recipient end
Load current in R tailing
Loop resistance ()
Loop inductance ()
Short Line Vector Diagram
C
IX
Im kos m
Vsn
G
H
AA
Vm
IR
B IX sin m
Vm kos m
sn
m
O
Vm kos m
D
I
F
Figure 2.4 Short line vector diagram
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Chapter 2:Transmission Lines
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A vector diagram for short line having relation with parameters found in short
line individual line figure. In this case vector diagram follow can be drawn like
Figure 2.2.4.
Refering to Figure 2.4, a parameter identified as;
OA
OI
AB
BC
OC
Transmission end voltage , Vm
Load Current, I
effect of resistence drop at the line, IR
effect of reactance drop at the line, IX
Receiver end voltage, Vsn
Refering to this parameter we could find end voltage transmision and further
determine his power factor. Try the following solution:OC  (OD  DF ) 2  ( FB  BC ) 2
and
 (V R os R  IR) 2  (V R sin  R  IX ) 2
cos  S 
OF V R cos  R  IR

OC
VS
In fact, from this vector diagram, we will be able to determine VS and power
factor, we also can determine regulation percent for a short line by referring
to the parameter. Regulation percent voltage refering to Figure 2.4 can be
written as.
Regulation Percent =
2.5
IR cos  R  IX sin  R
x 100
VS
……(Equation: 2.5)
Regulation Voltage Change with Load Power Factor
In this condition, voltage drop are same in magnitude and phase but phase
relationship with end voltage receiver and end voltage transmission are
changed.
A Voltage drop at end voltage receiver with increas of load for inductive case
(power factor lagging) and increase with capacitance load (power factor
leading). End voltage receiver not only depends to load but also in power
factor. Regulation voltage changing at end voltage transmission for different
power factor could be describe through locust figure such as Figure 2.4.
Refering to Figure 2.5, AO vector show end voltage receiver (VR) at load
state and OX line with angle ΦR, is load power factor with cos ΦR.Beside
that OX line also showed current (I) load phase. AB line drew parallel to OX
line having IR resistance's drop lR and vertical line BC drawn vertical to OX
line having inductance’s drop IX.
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Chapter 2:Transmission Lines
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Referring to figure 2.5, ABC is impedance triangle and CA is impedance
drop total IZ line. While OC shows end voltage receiver phase (VS) and
difference between VS and VR or ( OC - OA ) is voltage drop on-line and are
also known as regulation end transmission.
This regulation change able clearly seen if we see maximum regulasi in B
point and empty regulasi in S point by referring to locust figure (Figure 2.5)
through following equation :-.
Regulation = IR cos θR + IX sin θR
Regulation wiil be maximum when d ( regulation ) / d θ = 0
IR (-sin θ ) + IX ( cos θ ) = 0
atau
Tan θ = X / R
Transmission End Voltage, VS
H F
M
Receiver End Voltage VR
N
E
VS C
G
IX
VR
Φ
ΦR
O
Φ
IR
A
Power
factor
leading
B
X
I
IX
O’ I D
R
VS
VR
K
Power
factor
lagging
Q
P
S
Figure 2.5 Vm and Vsn Locus
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Chapter 2:Transmission Lines
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2.6 Regulation per Unit
When load at end receiver get power supply then will happen voltage drop
effect from resistance and inductance in conductor. Hence voltage value at
end receiver in Vm usually less compared end voltage transmission in Vsn.
Different voltage drop in end receiver and end transmission stated as end
transmission voltage percent known as regulation.
Regulation per unit definable as voltage change in end receiver part when
full load in halted, this will make voltage in transmission end equal to
receiver end. This situation can be made to appear in form of similarity as
follows:
Regulation Percent =
Vsn  Vm
x 100
Vm
……(Equation: 2.6)
Where is Vsn is transmission end voltage and Vm receiver end voltage.As
known regulation help to maintain voltage value in load terminal by setting
limit ( 5% error voltage) by using suitable control equipment.
2.7 Transmission Efficiency
When load
given supply through transmission line will happen
disappearance in conductor because of resistance and power effect sent in
load transmission end line less than power supplied in end transmission.
Transmission line efficiency found as power ratio received to power transmit
or can be may be written as;
Re ceived Power
x 100
Transmit Power
OutputPower
=
x 100
OutputPower  PowerLosses
Transmission Efficiency =
T
=
Vm Im cos m
x 100 ……(Equations: 2.7)
VsnIsn cos sn
Where is Vm, Im and cos m is voltage, current and receiver end power
factor while Vsn, Isn dan cos sn is voltage, current and transmission end
power factor.
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Chapter 2:Transmission Lines
2.8 Regulation per Unit And Efficiency Calculation
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Voltage Regulation and transmission line visible with clearer through simple
calculations examples like in this part.
Example 2.1:
A transmission line a capable phase power 1,100 kW to factory with a
voltage 11 kV in power factor 0.8 lagging. This line have a resistance 2 and
inductance coil 3 Get;
i). Voltage at transmission end.
ii). Regulation Percent.
iii). Transmission Line Efficiency
Solution :
Given;
Resistance, R = 2
Inductance, X = 3
Power , P = 1,100 kw
Power factor m = 0.8 (mengekor)
Receiver end voltage, Vm = 11,000 V
Load Current, I =
I=
P x 1,000
Vm cos m
1,100 x 1,000
11,000 x 0.8
I = 125 A
i). Value of transmission end voltage
known,
so that
cos m = 0.8
sin m = 0.6
Vsn =
(Vm cos m  IR) 2  (Vm sin m  IX ) 2
Vsn =
(11,000 x0.8  125 x 2) 2  (11,000 x0.6  125 x 3) 2
Vsn = 11,426 V
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Chapter 2:Transmission Lines
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ii). Regulation Voltage Unit.
Vsn = 11,426 V
Vm = 11,000 V
Vsn  Vm
Regulation Percent =
x 100
Vm
11,426  11,000
=
x 100
11,000
= 3.873 %
iii). Transmission Line Efficiency.
Power Losses
= I2 R = (125)2 x 2
= 31,250 atau 31.25 kw
Transmission Power
x 100
Re ceiving Power
Transmission Efficiency =
T =
T
1100 x 1000
x 100
(1100 x 1000) + 31250
= 97.24%
Example2.2:
A transmission line three phase 11 kV owns resistance 1.5 and inductance
4 for each phase. Calculate regulation percent and efficiency line percent
if total end receiver load, 5000 kVA in power factor 0.8 lagging and voltage
supplied until last distance was 11 kV.
Solution :
Resistance for each conductor R = 1.5
Inductance for each conductor, X = 4.0
11,000
phase voltage at end of receiver, Vm =
= 6,351 V
3
Transmission Load
= 5,000 kVA
Load power factor , kos m
= 0.8 (lagging)
Line Current, I =
=
Power in kVA x100
3 x Vm
5,000 x1,000
=
3 x 6,351
262.4 amp
Transmission end voltage 262.43
for each
A phase,
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Chapter 2:Transmission Lines
Vsn = Vm + IR cosm + IX sin m
= 6,351+(262.43x1.5x0.8)+(262.43x4x0.6)
= 7,295.8 V
Transmission end voltage VSL = 3 x 7,295.8 = 12,637V
So that,
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Vsn  Vm
x 100
Vm
12,637  11,000
=
x 100
11,000
= 14.88 %
Regulation Voltage Percent =
and
Transmission line efficiency =
T
=
Output Power
x 100
Output Power  Power Losses
5000k
x100
5000k + 103280.64
T = 97.98%
MEDIUM AND LONG TRANSMISSION LINE
2.9 Introduction of Medium Line and Long Line
Besides short line, medium line and long line also in transmission lines. As
compared both this line with short line, effect of loss caused resistance and
inductance in conductor were more numerous and large. With existence
large lost power on-line medium and long thus it also also influence
transmission line efficiency. As such voltage regulation should be done also
is large to overcome loss in acceptance end transmission line.
2.9.1 Medium Line and Long Line
Transmission line which possess line length between 60 to 150 kms and line
voltage between 20 kV to 100 kV classified as medium line. If for line short
capacitance effect deserted, in medium line capacitance effect taken.
Transmission line which possess long exceeding 150 kms and voltage reach
more 100 kV it classified as long line. As known each line influenced by
resistance, capacitance, inductance and conductivity. Due to this from
calculation aspect loss found in long line was enormous compared short and
medium line.
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Chapter 2:Transmission Lines
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2.9.2 Medium Line and Long Line circuit.
Medium Line Circuit
Referring to figure 2.6, a few parameters could be identified,
Vsn Transmission end voltage
Vm Receiver end voltage
Isn Transmission end current
Im
Receiver end current
Ic
Capacitance current
R
Loop Capacitance ()
X
Loop Inductance ()
C
Capacitance (farad)
ISn
R
X
line
Vsn
Im
IC
C
Vm
load
Neutral
Figure 2.6 Medium line individual circuit
Actually exist three way that can use to determine medium line individual line
figure such as end condenser methods, T method and  method . Figure 2.6
is method end condenser. This method crumple up capacitance in load end
part. If in short line capacitance deserted, in medium line also capacitance
taken into account this is because availability addition to voltage and length
value line.
Due to this regulation calculation in medium line will participate consider
capacitance and leak reactants in line and its can be explained depends on
value of receiving voltage.
Refering to circuit in Figure 2.6, we would note line current (Isn) is total load
current (Im) and also current recharging (Ic) for capacitance.Written as;
Isn = Im + Ic ……(Equations: 2.8)
If we write equation for current recharging for capacitance, Ic = jwCVm and
Im load current = Im (cost θm - jsin θm)
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Chapter 2:Transmission Lines
We will find out Isn = Im cost θm - jIm Sin θm j, as such with this
is found;
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equation
Voltage drop in line = Isn ( R JX ) from this equation we will know voltage
value found in transmission end as follows;
Vsn = Vm + Isn (R + jX). ……(Equations: 2.9)
Through this equation we can see how power flow occurring in line delivery
system medium and further we be able to size his voltage regulation.
Long Line Circuit
A transmission line who sent out electricity power release heat due to
conductor resistance. So long line act as a barrier. Transmission line also act
as a inductance because every conductor are surrounded by a magnetic
field in transmission line length. Long transmission line also acted as a its
capacitor because conductor act as pelitic capacitor. Resistance, inductance
and capacitance as a transmission line are dispensed uniform in line length,
with magnetic field around conductor along with electric field created by
different between that field.
We could imagine that a transmission line contain thousands resistor,
inductor and basis capacitor like those demonstrated at figure 2.7.
ISn
Vsn
R/n
X/n
B/n
Im
G/n
Vsn
Load
Figure 2.7 Long line individual circuit
Refering to Figure 2.7, a few parameter could be identified in among them;
Vsn Transmission end voltage
Vm Receiver end voltage
Isn Transmission end current
Im Receiver end current
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Chapter 2:Transmission Lines
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Apart from that several statements can be done refering to same circuit,
i). Line are made up a few constant parameter namely resistance,
inductance, capacitance and conductivity all along long transmission
line distribution.
ii). Resistance (R) and inductive reactance (X) is element on-line serial
transmission
iii). Capacitance string (B) and leaking conductivity (G) are element shunt,
leaking conductivity also caused on-line lost power. It derives of
insulation leak or corona effect in conductor.
iv) Leakage current which flowed through shunt graduate is maximum in
transmission end line and lesser continuously when headed for receiver
end and finally become zero after arriving to receiver end of line.
2.10 Voltage Effects on Trasmission Efficiency.
Transmission line efficiency is not only influenced by several constant occur
in transmission line namely resistance, inductance and capacitance like
already discussed before. However line efficiency also influenced by voltage
value are brought by something corona line and effect in that line. In this part
the effects will discuss briefly.
2.10.1 High Voltage Transmission ( 132 kV / 275 kV)
Usually withdrawn electricity by one generator station is about 33 kV, 22 kV
and 11 kV. Of that generator pass energy to a few transformer through span
line on by various extension way such as ring system, radial system, network
system etc. The generated voltage is step up to the wanted value such as
132 kV, 275 kV or 500 kV. This voltage purpose of raising was to reduce
expenditure in large cable size usage because cable size used is based on
enormity current which flowed. At the same time, transmission line efficiency
can be increased.
The situation explicable with double power (W) are sent through three
phase transmission system which possess line voltage (E) and cost power
factor kos , produce equations as follows
Current Line
I
W
3 E kos
…(Equations: 2.10)
Let say :
ι = Length of conductor line
=Resistance of conductor material
 = current density
A = Conductor cross section
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Chapter 2:Transmission Lines
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line loss may be written as:
 3I 2 R 
3W
E kos
Line efficiency transmission line:
3
output
 
  1
input
E kos
Voltage drop for each line:
= IR = ι
…………(Equations: 2.11)

…(Equations: 2.12)
……(Equations: 2.13)
Copper volume:
=3ιA 
3 W
……(Equations: 2.14)
 E kos
Refering to this equation some assumptions could be made among them:Equation (2.11), giving picture that lost power are proportional inverse with
E, also inversely proportional with power factor cost .
Equation (2.12), show that efficiency increased transmission line by adding
total voltage in line and power factor.
Equation (2.13), resistance decrease at every line are fixed ( when  and ι
assumed fixed. Voltage regulation can be repaired because fall percentage
voltage could be reduced with increasing value E.
Copper volume of necessity for transmission line are proportional inverse
with a voltage and system power hereby copper need dwindling.
Can be concluded of this equation altogether, when voltage and power
system value enhanced then this result would give efficiency in transmission
line by conductor material saving also can be done and further reduce
delivery cost with small cable size in long line.
Due to this line capacity advancing by the increase of transmission line
voltage. Undeniable that cost for transmission line and terminal equipment
also rising with the increase of transmission line voltage but overall cost is
proportional with delivery voltage. Moreover it will save cost in keeping with
lost power reduction which occurred in transmission line. Effect of that, the
delivery total cost decrease with the increase of transmission line voltage.
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Chapter 2:Transmission Lines
2.10.1.1
Corona
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Corona was electrical discharge emerge around overhead line conductor,
due to air flow where would disturb radio waves and creating lost power. In
low voltage there was no change which occurred can be influenced by air
condition around conductor. However when potential different and gradually
increase, at one level, glow luminance (luminous glow) weak purple color will
rise with hissing sound. This phenomenon is known as virtual corona and
participated by gas production which has identified through system feature
his smell. All situations such as hissing sound, purple radiation and gas
production smelling known as corona.
If conductor are homogeneous and smooth and similar state fixed all along
conductor, in other circumstances rugged parts will issue brightness. If range
in conductor not too big compared to diameter, arc may be might stand in for
before glow luminance seem. This happened in keeping with statement
where range in small conductor do not have time quite enabling glow
luminance happened.
In the case of a positive conductor DC system has a uniform warmth and
brightness of the rising of the negative division. For AU system, according to
the corona current is not sinusoidal. Corona, accompanied by loss of power,
losing is caused by light, heat, noise and chemical reactions. Corona exists
at small transmission line side effects of them;
i).
ii).
Result in lost power that is during uncertain weather condition.
Found voltage drop which not sinusoidal with current not corona
sinusoidal, this situation cause little trouble of communication circuit as
a result of electromagnetic and electrostatic induction.
iii). Harmonic wave distortion which many especially in third hormonic, that
exists in transmission line.
Corona formation produce ozone gas with chemical reaction in
conductor and creating corrosion
Corona effect in transmission line like those above-mentioned of course
undeniable especially for long transmission line
i). conductor diameter (for example with ACSR).
ii). Use more from one conductor for each phase, namely use bouquet
conductor (bundle conductor)
iii). Add more range in conductor hereby stress by magnetic static could be
reduced and thereby corona effect also could be reduced.
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OVERHEAD LINE INSULATOR
2.11 Principle and design and Overhead Line
Overhead line distribution system usually involving a few key component
namely wireline, insulation, tower post etc. However in chapter, insulator
applies in overhead line distribution system will be discussed. This Insulator
could be identified is based on design.
2.11.1 Overhead Line Insulators
Conductor for distribution system overhead line is guaranteed his security
with electric equipment assistance named insulator. This insulator then
would not be have been leaks current to earth from conductor through this
equipment. Due to this insulator play important role succeed distribution
operand overhead line system. Figure 2.8 show either insulator form of
equipment.
Figure 2.8: Few insulator form overhead line
A few important features and should be taken into consideration before
insulator applies in installation any overhead line distribution system among
them;
i.). Physical strength: ability arrested suitable burden heavily something
conductor.
ii). Having high insulation resistance to prevent current leak to earth.
iii). High resilience ratio of breach leap result voltage.
iv). Material used to develop insulator was the type that does not permeable
liquid or hollow and influenced by temperature changes.
v). This process does not contain impurity and crack and impervious of
liquid substance and gas of aerospace.
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Overhead line insulator common use including pin insulator, suspension
insulator, tension insulator and shackle insulator . In this chapter, only pin
insulator, suspension and insulator insulator tension will be discused .
Pin Insulator
Pin insulator designs by having steel pin could be installed in post bar tower.
This insulator have screw in pin part steel while conductor placing at this
insulator top and bound with use wire aluminum soft with a couple coil.
Pottery part kept apart from steel division with a kind of soft metal (timbre).
Design this pin insulator visible in figure 2.9(a) for low voltage a pin insulator
used is fair enough.
For transmission line high voltage also stronger and large pin insulator
utilized. Type pin insulator high voltage is different with insulator construction
low voltage pin. Insulator construction high voltage pin comprising two or
more ceramic layer simultaneous cement. Use a insulator unit pin fair
enough for delivery system 33 kV if exceeded over in this voltage proportion
two or more insulator arrangement pin used. However inside pin insulator
use overhead line delivery system is not economy for voltage exceeding 80
kV. Figure 2.9(b) show schematic figure a pin insulator for overhead line.
(a) Design
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Chapter 2:Transmission Lines
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Conductor
Binding Wire
glazed porcelain
Plumbed
Shield
Steel pin
Tower Bar
(b) Schematic
Figure 2.9
Pin Insulator
2.11.3 Suspension Insulator
Insulator installation suspension in dependent overhead line to voltage
capacity under by conductor in line singles. Capacity expansion voltage at
one line will participate increase number insulator installation suspension in
that line. By transmission line and distribution as most handling exceeding
33 kV then sistam become bigger and distance between increased line far.
This situation cause pin insulator have no capacity to keep this line system.
Due to this to overcome this problem suspension insulator designs, insulator
exact figure pin can be observed in Figure 2.10(a)
Suspension Insulator suspend in different tower post bar with pin insulator
placing at bar top. For type this insulator, conductor will be connected in
insulator lower part suspension. As such we can add range in tower bar with
conductor through insulator addition suspension arranged by network.
Insulator increasing number suspension at one line are referring to line
voltage capacity, weather condition, transmission line and size assembly
type suspension insulator used.
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Because this insulator is fitted by network then replacement any insulator
could be made without change insulator entire network. Figure 2.9(b) show
schematic form a suspension insulator
Figure 2.10(a) Suspension Insulator
Socket
Cement
Steel Cap
Glass or Pottery
Balls
Steel Pin
Figure 2.10(b) Suspension Insulator schematic
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Chapter 2:Transmission Lines
2.11.4 Strain Insulator
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At one overhead line state having high tension, for example at end or hairpin
at transmission line. For tension its low voltage line use shackle insulator.
Whereas for line tension insulator high voltage tension used. Usually in
insulator installation in transmission line two or more insulator used. Insulator
disk tension fitted with horizontally different with suspension insulator will
fitted with vertically. Process of tension insulator are same with suspension
insulator, however height size of suspension insulator are exceeded
tension insulator (Refer to Figure 2.11).
Figure 2.11 : Tension Insulator Schematic
tegangan
Advantages and Disadvantages Overhead Line Insulator
The advantages of suspension insulator compared pin insulator can be
explained as follows;
i). Suspension insulator is cheaper from his cost aspect for capacity line
which exceeded 50 kV.
ii). For each unit of suspension insulator type will designs by refer at low
voltage capacity around 11kV . When used in high voltage capacity then
enough with connect suspension insulator by serial, disk number used
depends on voltage value in line.
iii). If occur unanticipated damage in which points suspension insulator, just
replace damaged disk only and no need replace insulator entire network
that suspension.
iv). Suspension insulator is more flexible assembled on in line. Insulator
connection tension in tower bar is ease to turn to any direction.
v). Pin insulator suitable to be fitted in low post compared suspension
insulator.
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Chapter 2:Transmission Lines
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Disadvantages of suspension insulator compared pin insulator can be
explained as follows;
i) Suspension insulator no suitable to be fitted in low tower post.
ii) Suspension insulator need high and strong post and this increase
cost delivery.
iii). Damaged at pin insulator difficult to be detected as compared
suspension insulator.
iv). Limited pin insulator capacity only in voltage below 80 kV.
v). Suspension insulator need wide column between conductor compared
pin insulator.
Tests Conducted on Overhead Line Insulator
Overhead line insulator are important instrument to achieve electricity
transmission process and distribution at some area. Due to this suitable and
safe insulator selection should be taken into consideration, so that damage
in line does not happen. Ensure insulators are used at well off overhead line
several tests should be done before its used or being marketed. Test shouls
be done before used and marketed are:(a). Design test (Test emerge arc or flashover)
(b). Performance test
(c). Habit test
(a). Design test
Design test done to ensure electric performance and mechanical insulator to
several trial condition such as test emerge dry arc, test emerge wet arc and
test emerge contamination arc. Insulator test of methods listed this
commonly made to three insulator randomly chosen. This insulator will be
tested either fulfilling standard or on the other hand.
i.
Test Emerge Dry Arc
Voltage emerge arc is voltage cause insulator surface breach insulate, allow
current flow through insulator face from conductor to supporter bar. A
insulator fixing with a safe minimum voltage imposed at insulator. This
minimum voltage is dependent to insulator type and size.
In tests emerge this dry arc, a net and dry insulator assembled on a
supporter. A voltage with power frequency system imposed in that insulator.
This voltage will increase by way staggered until minimum voltage for
insulator under test. This minimum voltage need to be given in insulator
within not less than 30 seconds . If emerge arc does not happen in that
period, insulator is good. Voltage raised again by way gradually until
flashover happened within 10 seconds. Lightning overvoltage being
recorded. This process is repeated as much as four times. Average voltage
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of flashover could not less than minimum voltage of past dry lightning that is
fixed.
ii.
Test Emerge Wet Arc
This test equal to test (a) except under synthetic rain which possess
resistance and temperature that is fixed. Angle and speed rate synthetic rain
water decline also in fix. In this time, insulator should arrested lower
minimum voltage of test (a) long 30 seconds at least without emerge arc.
iii.
Test Emerge Contamination Arc
This test equal to test (b) except involving contamination with fog, salt,
smoke, dust or chemical. Usually, lightning overvoltage is ½ value than tests
(b).
(b). Performance Test
Performance test is another test used to determine the overhead line insulators are
safe (to meet required standards). Among the tests involved dalan performance test
is;
i.
Broken Test Insulate
Breakdown tests carried out on 3% per cent of the total insulation produced. To test
the dielectric insulation. Insulation may be able to withstand extreme lightning
events have suffered, but it must be replaced if it had been breakdown.
For insulation design, flash past should occur at voltages less than voltage
breakdown. At the time of testing, the insulation shall be immersed in a clean
insulating oil to prevent flash past. The value of the test voltage is raised slowly and
the insulation must be able to withstand 1.3 times the voltage dry flash past without
breakdown.
ii. Pulse Test.
Previous voltage lightning pulses obtained by using a signal pulse as in Figure 2.11.
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Magnitude
Leading
Wave
Lagging
Wave
Time
Figure 2.12: test wave form pulse
Pulse Ratio 
iii.
Pulse Overvoltage
Lighting overvoltage power frequency
Mechanical Test
A insulator network suspend tested by one tension 1.2 times double
maximum load usually and type insulator pin tested with moment bentokan
2.5 times double maximum burden usually. After the test, dry lightning
overvoltage test required again give ensure be provided change in lightning
overvoltage.
iv.
Temperature Test
The insulator is immersed in rotation in water barrels temperature 70
degrees celsius and 7 degrees celsius. Overall immersion number is six
times, invariably take one hour long. The insulator then dried and flash test
dry implemented.
v.
Porosity Test
This is glaze test in pottery insulator. The insulator is weighed in dry state
then it immersed in water and under pressure long 24 hours. After that the
insulator is issued, his face dried. Difference between both the reading show
the pottery deep water result gelis imperfect.
(c). Habit Test
Habit test are involving high voltage and test test corrosion which conducted
on all insulator. For test insulator erosion and rustiness usually divulge to
copper solution of sulphate in temperature 15.6 celcius in time a minute.
After one minute insulator tested will in transferred and then polished and
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cleaned and then disclosed again to copper solution of sulphate. Ianya done
repeatedly up to four times. After that checked to be sure there were no any
rustiness and metal cleave to insulator tested.
High voltage test committed against pin insulator, where it
overturned and placed inside water which hit keparas insulator neck. Water
also placed in hole spindle. Then high voltage are supplied in 5 minutes
time. After going through this test should good insulator will not suffer
damage.
INSULATOR NETWORK OVERHEAD LINE
2.12 Introduction Insulator Network Overhead Line
After we learn a few
insulator form overhead line and
also tests which operate on
insulator. We have obtain
description a little bit insulator
need
for
delivery
system
overhead line
However also
need we know that insulator are
used at overhead line namely
suspension insulator (Figure
1.13), having different voltage
distribution
within
one
network.This potential difference
would
cause
network
inefficiency insulation happened
when occurence of interference
(lightning) on overhead line.
Although that kecepan this can
be repaired with a couple method which will in discuss further dalan this
input.
Figure 2.13 Insulator installation suspension in
overhead line
2.12.1 Potential Distribution in Network Insulator
Overhead line which operates in high voltage capacity using some
disk number (suspension insulator) connected by serial. Connection these
disks by serial overall known as network insulator. Each suspension
insulator having metal installation own and each metal installation for per unit
this having relative fitness on metal installation to different units. For network
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this insulator mutual capacitance are referring between metal installation
insulator per unit suspension. Shunt fitness or air fitness also refering to
each metal installation between insulator unit suspension with tower post to
earth.
Because availability faggot voltage in insulator network suspension when
dihidupkan, cause unequal voltage division at every insulator will happen.
Potential difference voltage found in insulator network is different, for
insulator near network with conductor having voltage percentage value high
compared near insulator with tower post. This situation cause voltage
division no linear in this network insulator. Situation explicable refer solution
in Figure 2.14 (a) and (b).
I1
V1
C1
A
V2
E
i1
I2
V1
C1
B
V1
C
A
V2
C
i2
E
B
V1 + V2
V3
C
C
C1
i3
V1 + V2 + V3
Figure a
V3
I3
I4
Figure b
Figure 2.14 Process (a)and equivalent circuit (b) for insulator network
Refering to Figure 2.14, known;
C : Mutual capacitance
C1 : Shunt fitness or air fitness
V1 : Voltage negotiate first suspension insulator unit (near to tower post)
V2 : Voltage negotiate second suspension insulator unit.
V3 : Voltage negotiate third suspension insulator unit (near to conductor)
E : Voltage between conductor and earth.
Take K = C1 / C or C1 = KC
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Use law kirchhoff in node A we find out:-
I2 =
CV2 =
CV2 =
CV2 =
V2 =
V2 =
C1 = KC
I1 + i1
CV1 + C1V1
CV1 + KCV1
C(V1 + KV1)
(V1 + KV1)
V1(1 + K)
……………… Get V1
By using law kirchhoff in node B we find out:I3 = I2 + i2
CV3 = CV2 + C1( V1 + V2) …………..…..Voltage negotiate C1 air's fitness
from tower post to insulator unit to two = ( V1+ V2) …… figure above and
note
CV3 = CV2 + KC( V1 + V2)
CV3 = C[V2 + K ( V1 + V2)]
know V2 = V1 (1 + K)
V3 = [V2 + K( V1 + V2)]
V3 = [KV1 + V2(1 + K)]
V3 = [KV1 + V1 (1 + K) (1 + K)]
V3 = V1 [K + (1 + K) (1 + K)] ……………….Simplified.
V3 = V1 (K + 1 + 2 K + K²)
V3 = V1 (1 + 3 K + K²)
…...…………..Get V1
Voltage between tower conductor and post (to earth) :E = V 1 + V2 + V3
E = V1 + V1(1 + K) + V1 (1 + 3 K + K²)
E = V1 ( 3 + 4K + K2 )
From this equation is found :V1 = E / ( 3 + 4K + K2 )
…..{Equations: 2.16)
After getting V1 value further obtain V2 value and V3. Of in this retrieval we
will see bezaupaya voltage negotiate each this network insulator.
Example 2.3:
A network to four insulator used to hang up a 33kV conductor, three
overhead line phase. Kapasitan air or shunt between every cap and tower
was one tenth (1/10) from each fitness unit. Calculate voltage hinder each
insulator.
Solution :
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Given:
E = 33kV
K = C1/C = 1/10 = 0.1
With use equation were obtained of 8.1 we know;
V2 = V1(1 + K)
V3 = V1 (1 + 3 K + K²)
For equation V4 voltage hinder fourth insulator, available with method used
just like in 8.1 and found as;
V4 = V1 (1 + 6K + 5K2 + K3)
So that
V2 = V1(1 + K)
V2 = V1(1 +0.1)
V2 = 1.1V1
V3 = V1 (1 + 3 K + K²)
V3 = V1(1+ 3(0.1) +(0.1)2)
V3 = 1.31V1
V4 = V1 (1 + 6K + 5K2 + K3)
V4 = V1(1+ 6(0.1) + 5(0.1)2 + (0.1)3)
V4 = 1.651V1
Voltage between tower conductor and post (to earth) :E = V 1 + V2 + V3 + V4
E = V1 + 1.1V1 + 1.31V1 + 1.651V1
E = 5.061V1
and
E=
33000
3
= 19050V
So that;
V1 = E / 5.061
V1 = 19050 / 5.061
V1 = 3764.7V
By including V1 value in V2 ,V3 equation, and V4, from this equation is
found :V2 = 1.1V1
V2 = 1.1(3764.7)
V2 = 4141.2V
V3 = 1.31V1
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V3 = 1.31(3764.7)
V3 = 4931.8V
V4 = 1.651V1
V4 = 1.651(3764.7)
V4 = 6215.5V
Refering to voltage values negotiate insulation per unit found V4 voltage's
value obstruct fourth insulator in insulation network (near to conductor) was
high compared V1 voltage's value in near insulator with tower post namely
first insulator.
2.12.2 Network Efficiency
Because availability unequal voltage division at every network insulator are
used at overhead line what when occurence of interrupt or ganguan lightning
result. Namely voltage negotiate near insulator with higher conductor and
decrease until to near insulator with tower post. Then will reduce efficiency
in insulation network used. Network efficiency also influenced by insulator
number suspension applies in a network. Apart from that depend also to
fitness ratio air (capacitance between tower unit and post) with mutual
capacitance (capacitance between unit) at one network. Network efficiency
for use overhead line definable as;
Network Efficiency =
Or can be writen as,
Network Efficiency =
Voltage Hinder Network
x 100%
n x Voltage Hinder Insulator
near to conductor
E
x 100%
nVT
…..{Equations: 2.17)
Where;
E = Voltan hinder network
n = number of insulator arranged by serial in network insulator
VT = Voltage Hinder Insulator near to conductor
Example 2.4:
A network to four insulators used to hang up a 33kV conductor, three
overhead line phase. Kapasitan air or shunt between every cap and tower
was one tenth (1/10) from each fitness unit. Calculate insulator efficiency this
network..
Solution :
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By using answer achieved of example 2.3 namely;
V4 = 6215.5V (Voltage Hinder Insulator near to conductor)
Given;
33000
E=
= 19053V
3
n= 4
So that;
Network efficiency =
E
x 100%
nVT
=
19053
4 x 6215.5
= 76.6%
x 100%
2.12.3 Repairing Potential Distribution in Network Insulator
Although found potentisal inside voltage a insulator system network
which reduces insulator efficiency network for overhead line. This problem
could be overcome and repair by variety way among them extend tower bar,
capacitance grading, shielding static and use guard ring. In this input only
two ways would discuss to improve efficiency in network insulator namely
cross arm and guard ring
(a)
Cross-arm
Cross arm mean increase bar distance serves to suspend network
insulator of tower post. Through this method network efficiency can be
increased. If referring to example 2.3, to get network efficiency is obviously
namely by adding bar distance from tower post will participate reduce K
value (capacitor ratio). When K value reduced namely lower of 0.1 then will
increase insulator efficiency network. However this method is on to high and
large tower post only because for post small tower had no enough capacity
to support long bar weight and also network insulator. Figure 2.15 show
schematic for cross arm method
Tower Bar
D
D = Bar length
Conductor
Figure 2.15 Cross arm schematic
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Chapter 2:Transmission Lines
(b)
ET302
guard ring
Ring way obstruction can be done with use static shield. This static
shield assembled on end lower part insulator unit connected by using joining
of metal in suspension insulator and then connects to line conductor.
Guard ring which functions as curtain for per unit, reduce earth capacitance
and create capacitance between insulator line and cap. Capacitance value is
big in nearby unit part with guard ring and this will reduce voltage fall
negotiate insulator per unit network. Through this way same voltage
distribution negotiates per unit is impossible obtained in practically. However
it could be considered to increase decently possible network efficiency. This
guard ring method visible like figure 2.16(a).
Tower post
I1
Tower Post
C
i1
C
1
Arc Horn
C1
C1
Obstruction Ring
i2
i3
I2
C
I3
Conductor
Ix
Cx
Iy
C
y
Iz
C
z
V2
V3
Obstruction Ring
(b) Equivalent circuit
(a) Construction
Figure 2.16 :
C
V1
Guard ring
Refering to figure 2.16(b), a guard ring were installed in conductor part
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so that level voltage voltage be equivalent. In this situation capacitanc
current i1, i2 and i3 become equal capacitance current conductor to Ix pin, Iy
and Iz. as such voltage value insulation per unit is the same namely V1 = V2
= V3 = V.
Supposing Cx, Cy and Cz is capacitance obstruction need to be same
voltage division;
Through solution with method used kirchhoff law at every node we will
achieve;
At point A,
At point C,
C1V = Cx3V
C1V = Cx3V
Cx = C1 / 3
C13V = CzV
C13V = CzV
Cz = 3C1
At point B,
C12V = Cy 2V
C1V = Cy 2V
Cy = C1
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