i fast transient simulation of pinceti surge arrester
TRANSCRIPT
i
FAST TRANSIENT SIMULATION OF PINCETI SURGE ARRESTER MODEL ON
A TRANSMISSION LINE USING ATP SOFTWARE
YUSOF BIN MUHAMAD
A project report submitted in partial
fulfilment of the requirement for the award of the
Degree of the Master of Electrical Engineering
Faculty of Electrical and Electronics Engineering
Universiti Tun Hussein Onn Malaysia
JAN 2015
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ABSTRACT
Lightning is one of the main causes of overvoltage on power system. Over voltages
problem at the transmission line can cause flashover voltage at the insulator string,
power system disturbances and transformer failure. To prevent of insulator string and
equipment of the power system from damaging effect by lightning overvoltage, metal
oxide surge arrester is installed at overhead line in parallel with insulator string. Due to
metal oxide surge arrester have dynamic behaviour, this arrester can be simulated using
non-linear resistor. Therefore Pinceti model is proposed to simulate using Alternative
Transient Program (ATP) software. Several procedures have been following to calculate
Pinceti arrester model parameters so that compatible with 132kV overhead transmission
line system. Tested result by simulation is compared with the manufacturer arrester
datasheet to evaluate accuracy of Pinceti model before installed arrester at 132kV
transmission line model. Pinceti model are installed at several locations on the
transmission line model to evaluate the level of effectiveness and capabilities to reduce
the level of overvoltage across insulator string and to ensure lightning overcurrent draws
to ground totally.
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ABSTRAK
Kilat merupakan salah satu punca berlakunya masalah voltan lampau dalam sistem
kuasa. Masalah voltan lampau dalam talian penghantaran boleh menyebabkan
berlakunya voltan lampau pada penebat, gangguan dalam sistem kuasa dan kebakaran
pada alatubah. Untuk mencegah dari berlakunya kerosakan pada penebat dan alatan
dalam sistem kuasa kesan dari voltan lampau kilat ini, penangkap kilat jenis metal oxide
dipasang pada talian penghantaran secara selari dengan penebat. Disebabkan penangkap
kilat jenis metal oxide ini mempunyai ciri-ciri dinamik, penangkap kilat ini boleh
disimulasikan dengan meggunakan perintang bukan linear. Oleh itu, model penangkap
kilat Pinceti dicadangkan untuk disimulasikan dengan menggunakan perisian Alternative
Transient Program (ATP). Beberapa prosedur harus diikut untuk mengira parameter-
parameter pada model Pinceti supaya bersesuaian dengan talian penghantaran 132kV.
Hasil ujikaji dengan menggunakan simulasi dibandingkan dengan data penangkap kilat
yang diperolehi dari pembuat penangkap kilat sebenar bagi menilai ketepatan model
Pinceti sebelum ia dipasang pada model talian penghantaran 132kV. Model Pinceti
dipasang pada beberapa lokasi talian penghantaran untuk menilai keberkesanan dan
keupayaan bagi mengurangkan aras voltan lampau kilat pada penebat dan untuk
memastikan arus lampau kilat dapat mengalir ke bumi secara keseluruhannya.
vii
TABLE OF CONTENTS
TITLE i
DECLARATION ii
ACKNOWLEDGMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES ix
LIST OF FIGURES xi
LIST OF SYMBOLS AND ABBREVIATIONS xiv
CHAPTER 1 INTRODUCTION 1
1.1 Introduction 1
1.2 Problem statement 2
1.3 Objectives 5
1.4 Project scopes 5
1.5 Outline of dissertation 6
CHAPTER 2 LITERATURE REVIEW 7
2.1 Introduction of lightning 7
2.2 Fundamental of surge arrester 9
2.3 I-V characteristics 11
2.4 Types of surge arrester model 12
2.5 Transmission line tower 15
2.6 Lightning source 19
CHAPTER 3 RESEARCH METHODOLOGY 20
3.1 Introduction 20
viii
3.2 Study Alternative Transient Program (ATP) software 21
3.3 Study lightning source parameter 24
3.4 Study about Pinceti surge arrester model parameter 27
3.5 Study transmission line system model 32
3.6 Save ATP Program 39
3.7 Run ATP program 40
CHAPTER 4 RESULTS AND DISCUSSION 42
4.1. Introduction 42
4.2 Pinceti model testing 43
4.3 Install Pinceti model at transmission line 47
4.4 Discussion of the current draws to ground 60
CHAPTER 5 CONCLUSION AND RECOMENDATION 64
5.1 Conclusion 64
5.2 Recommendations 65
REFERENCES 66
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LIST OF TABLES
Table 3.1 Pinceti Model parameter for 20kV rating 28
Table 3.2 V-I characteristics for non-linear A0 and A1 for
V8/20µs =46.2kV 29
Table 3.3 IEC suggested for TLA rating 29
Table 3.4 ABB EXLIM P datasheet 30
Table 3.5 Pinceti Model Parameter for 120kV rating 31
Table 3.6 V-I characteristics for non-linear A0 and A1 for
V8/20µs =276kV 31
Table 3.7 Cable specification 37
Table 4.2 Calculated Residual Voltages for the ABB MWA
16kV arrester 43
Table 4.3 Voltage injected versus residual current for the
ABB MWA 16kV arrester 44
Table 4.4 Calculated residual voltages for the EXLIM P
132kV arrester 45
Table 4.5 Votage injected versus residual current for the
ABB EXLIM 120-kV arrester 45
Table 4.6 Insulator string voltage without MOV and with
MOV (left pole) 48
Table 4.7 Residual voltage and current flow to the
ground (left pole) 49
Table 4.8 Residual Voltage Without MOV and with
MOV (right pole) 55
x
Table 4.9 Residual voltage and current flow to the
ground (right pole) 55
Table 4.10 Current flow to round for each tower 60
xi
LIST OF FIGURES
Figure 1.1 Damage of transformer at TNB substation due to
lightning strike 1
Figure 1.2 No of day with lightning strike in Malaysia 3
Figure 1.3 Lightning surge arrester 5
Figure 2.1 Cloud to ground downward negative lightning 8
Figure 2.2 Porcelain housing metal oxide surge arrester 10
Figure 2.3 V-I characteristics of MO arrester 336kV 11
Figure 2.4 Pinceti Model 12
Figure 2.5 IEEE Model 13
Figure 2.6 Fernandez Model 14
Figure 2.7 132kV multi-storey transmission line 16
Figure 2.8 Insulator string 18
Figure 2.9 Time duration of a typical lightning surge 19
Figure 3.1 Main window 23
Figure 3.2 Plotting program in ATP 24
Figure 3.3 Circuit that has been used to define the parameter
of the surge model 25
Figure 3.4 Dialog box of the Hidler Type surge model 25
Figure 3.5 8/20 µs lightning waveshape 26
Figure 3.6 V-I characteristics for non-linear A0 and A1 28
Figure 3.7 Conductor phase of impedance wave 33
Figure 3.8 Shield wire of impedance wave 34
Figure 3.9 Tower surge impedance wave 35
Figure 3.10 Insulator string 35
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Figure 3.11 Cable data 36
Figure 3.12 AC source 132kVL-L 38
Figure 3.13 AC source 38
Figure 3.14 VL-L probe connection 39
Figure 3.15 Save ATP program 39
Figure 3.16 Writing file name 40
Figure 3.17 ATP run 40
Figure 3.18 Select file 41
Figure 3.19 Voltage probe name 41
Figure 4.1 Residual current testing model 43
Figure 4.2 Graph Voltage Inject Versus Residual Current
for 20kA rating 44
Figure 4.3 Graph voltage inject versus residual current 46
Figure 4.4 Surge at tower (back flashover) 47
Figure 4.5 Location of tower 47
Figure 4.6 Left pole upper phase (without Pinceti) 49
Figure 4.7 Left pole upper phase (with Pinceti) 50
Figure 4.8 Left Pole Medium Phase (without Pinceti) 50
Figure 4.9 Left Pole Middle Phase (with Pinceti) 51
Figure 4.10 Left Pole Lower Phase (without Pinceti) 51
Figure 4.11 Left Pole Lower Phase (with Pinceti) 52
Figure 4.12 Graph residual Voltage Versus Tower
(Left Pole Upper Phase) 52
Figure 4.13 Graph residual Voltage Versus Tower
(Left Pole Middle Phase) 53
Figure 4.14 Graph residual Voltage Versus Tower
(Left Pole Lower Phase) 54
Figure 4.15 Right pole upper phase (without MOV) 56
Figure 4.16 Right pole upper phase (with MOV) 56
Figure 4.17 Right pole middle phase (without MOV) 57
Figure 4.18 Right pole middle phase (with MOV) 57
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Figure 4.19 Right pole lower phase (without MOV) 58
Figure 4.20 Right Pole Lower Phase (with MOV) 58
Figure 4.21 Graph residual Voltage Versus Tower
(Right Pole Upper Phase) 59
Figure 4.22 Graph residual voltage versus tower
(Right Pole Middle Phase) 59
Figure 4.23 Graph residual Voltage Versus Tower
(Right Pole Lower Phase) 60
Figure 4.24 Balance lightning current to ground 61
Figure 4.25 Current flow in transmission line 62
Figure 4.26 Current flow in transmission line when lightning 62
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LIST OF SYMBOLS AND ABBREVIATIONS
MOV - Metal Oxide Varistor
ZnO - Zinc Oxide
SiC - Silicone Carbaid
ATP - Alternative Transient Program
MCOV - Maximum Continuous Operating Voltage
TLA - Transmission Line Surge Arrester
CFO - Critical flashover voltage
IEC - International Electrotechnical Commission
IEEE - Institute of Electrical and Electronics Engineers
AAAC - All Aluminium Alloy Conductor
ACSR - Aluminium Conductor Steel Reinforced
TNB - Tenaga Nasional Berhad
AC - Alternating Current
I-V - Current – Voltage
1
CHAPTER 1
INTRODUCTION
1.1 Introduction
Lightning is one of the main causes of the outages on power networks. The lightning
surge can produce dangerous overvoltage, causing power supply interruptions that result
in costly damage to equipment and also imposing an extra cost to the power utility
because of the undelivered energy such in Figure 1.1. The amount of energy contained
in a lightning stroke is very high and it can be extremely destructive, even a single stroke
to a distribution line can be sufficient to cause a blackout through a feeder.
Figure 1.1: Damage of transformer at TNB substation due to lightning strike
Generally lightning strikes mostly the top of a transmission tower (shied-wire)
rather than the phase conductor. When lightning current hits the top of a transmission
tower, it flows to the bottom of the tower and out onto ground. If the voltage equals or
2
exceeds the line critical flashover voltage (CFO), flashover will occur across insulator
string. This flashover issues are important for evaluating of lightning performance.
Therefore, in order to increase the reliability and availability of the power system, the
lightning-related outages rates must be reduced.
Nowadays, transmission line surge arresters (TLAs) are vital elements to protect
the power systems against the lightning surges by absorbing the energy of surges and
limiting their resultant overvoltage below a certain value which is basic impulse
insulation level [1]. TLA able to reduce lightning initiated flashovers, maintain high
power quality and to avoid damages and disturbances especially in areas with high soil
resistivity and lightning ground flash density [2]. TLA is connected in parallel with them
at selected towers. A computer program is used to determine the optimum number of
locations and to calculate the arrester stresses at each of the chosen locations. Surge
arrester as a robust and efficient alternative, could be located at line ends and along the
line at selected points.
In Malaysia, lightning overvoltage is concern more for 132kV/275kV
transmission line system. Many observations have been done to evaluate about this
problem experimentally and by software modelling. One of the famous tools for
modelling 132kV transmission line system is by using Alternative Transient Program
(ATP) software. This software is most useful for modelling transmission line model and
the most famous model design by using this software is multi-storey tower model.
1.2 Problem statement
Electrical power systems have three main parts that transform other types of energy into
electrical energy and transmit this energy to consumer. The three main components are
generation, transmission and distribution system. However, transmission line have the
longest distance compare with generation and distribution system. So transmission line
most attracted to the lightning strike due to high structure of transmission line tower.
According to Malaysia Meteorological Services Department, most state of
Malaysia has a number of days with thunderstorm more than 100 per day. Malaysia
ranks one of the countries with highest lightning activities in the world. Refer to Figure
3
1.2; average thunders for Kuala Lumpur are 180-300 per annum. Eighty percent of
lightning discharges current to ground in Malaysia exceed 20kA, potentially
approaching 50-100 million volts. Lightning is classified as a transient event. The
amount of energy contained in a lightning stroke is very high. Lightning can cause
destruction of equipment, damage to substation or power plant equipment.
Figure 1.2: No of day with lightning strike in Malaysia [3]
Lightning faults have two types which are flash over and back flashovers. Flash
over mainly following a screen failure and caused by direct hitting to the phase
conductor. Back flash over which can occur when lightning strike hits tower or the
ground wire. In this case, the potential at the top of the tower rises in an important way
and can exceed the dielectric strength of the insulator string. Therefore, it is very
important to propose some idea for improve the lightning protection scheme in electrical
power system. This can be done by proposed a new surge arrester [4].
Transmission line surge arresters are installed in an overhead line in parallel to an
insulator string to prevent flashover at the insulator string. Line arresters are preferably
installed where frequent backlash over occur due to missing or inadequate overhead
ground or shield wire protection and or high tower footing impedances. In order to
improve the supply quality of an already existing transmission or distribution line,
installing line arrester on all or only on same of the tower poles is in many cases a cost
saving alternative to improving the shielding of the line or the grounding or towers or
poles [5].
4
However for the economical factor, not all transmission line towers are installed
with surge arrester. As far as economy and other factors are concerned, the transmission
lines in our country are only installed one or two kilometres lightning conductors in and
out of the substations or power factories. Power supply faults and failure caused by
detour or back lightning striking happen especially in mountain areas [6]. TNB
transmission line department use TFlash Software to determine which tower and which
phase should be installed with Transmission Line surge arrester (TLA).
An accurate surge arrester model will increase the lightning protective level of
the electric power system. Surge arrester installation removes the superfluous charge
from the line. The most common types of surge arrester are open spark gap, Silicon
Carbaid (SiC) arrester with spark gap and metal oxide surge arrester without spark gap.
Mainly Zink Oxide under metal oxide category is today most common used [4].
Metal oxide arresters are extensively used in power systems due to their good
performance in over-voltage protection. Appropriate modelling of their dynamic
characteristics is very important for arrester location and insulation coordination studies.
For switching surge studies, the MOAs can be represented simply with their nonlinear –
characteristics. However, such a practice will not be appropriate for lightning surge
studies because the MOA exhibits dynamic characteristics such that the voltage across
the arrester increases as the time-to-crest of the arrester current decreases and the
arrester voltage reaches a peak before the arrester current peaks [7].
5
Figure 1.3: Lightning surge arrester
1.3 Objectives
The purpose of the research is to accomplish three objectives as follow:-
a) To develop 132kV high voltage transmission line system using ATP software.
b) To use Pinceti surge arrester model in ATP software.
c) To evaluate the effectiveness of the Pinceti surge arrester model.
1.4 Project scopes
As the research a boundary, several limitations has describes as follow:-
1. This project only concern on Pinceti surge arrester lightning protection model
performance.
2. Develop the 132kV overhead transmission line double circuit Bergeron model.
3. Develop the 10kA lightning current impulse 8/20µs wave shape and strike only at
top of fourth tower out of seven tower
6
4. Pinceti model surge arrester are installed at third, fourth and fifth tower
5. Study only metal oxide surge arrester type only.
1.5 Outline of dissertation
This thesis is dividing into five chapters. Basically, some theory and literature review,
introduction, methodology, simulation result, comparison of result, analysis and
discussion and conclusion were included in these five chapters.
Chapter 1 summarizes project background and elaborates on project objectives, scope
and problem statement.
Chapter 2 explains a few literature reviews about surge arrester, description of lightning
strike phenomenon and parameter of transmission line tower.
Chapter 3 describes the methodology of project development. This chapter also will
explain detail about ATP software, 132kV transmission line tower model parameter,
overvoltage cable, Pinceti surge arrester model parameter and AC voltage source.
Chapter 4 shows about the result and discussion of simulation to evaluate effectiveness
of Pinceti model surge arrester when installed at transmission line after 10kA lightning
surge strikes at transmission line tower. This chapter divided to three phases. First phase
is to shows the result of testing the effectiveness of Pinceti arrester itself. Second phase
is shows the measurement result for the value of voltage and current when lightning
strike to tower without Pinceti arrester and for the last phase is to shows the
measurement result for the value of voltage and current at transmission line with Pinceti
arrester installed parallel with insulator string. All result for those three phases are
discussed briefly in this chapter.
Chapter 5 elaborates generally about the conclusion and recommendation for this master
project overall.
7
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction of lightning
Lightning is the most frequent cause of overvoltage and is classified as a transient
overvoltage event. This is because lightning strikes a power line, it is like closing a big
switch between a large current source and the power line circuit and cause abrupt change
in the circuit conditions creating transient problem. Lightning spark resulting from the
development of millions of volts between clouds or between a cloud and the earth. It is
similar to the dielectric breakdown of a huge capacitor [1]. The voltage of a lightning
stroke may start at hundreds of millions of volts between the cloud and earth. The study
of lightning strokes in power lines is very important because typically, the highest
structures located in high incidence lightning regions. Any structure, no matter its size,
may be struck by lightning, but the probability of a structure been struck increases with
its height [8]. Most lightning strikes terminate on shield wire rather than on phase wire.
Basically, there are four types of lightning, which are cloud-to-ground downward
positive, cloud-to-ground downward negative, ground-to-cloud upward positive and
ground-to-cloud upward negative as shown in Figure 2.1 respectively. However, only
cloud-to-ground lightning has been studied widely due to human and power system
safety.
8
.
Figure 2. 1: Cloud to ground downward negative lightning [8]
Lightning occurs when clouds acquire electrical charge. Electric field is considered have
strength are created within the cloud and between cloud and earth. When the field
become excessive, the dielectric of huge capacitor cannot longer support electrical stress
and then lightning flash occurs. According to Martin A. Uman and Rocov (2001), about
90% of cloud-to-ground lightning is downward moving negative charged leader while
only 10% of the cloud-to ground lightning is downward moving positive leader. Cloud
to ground flashes are composed of a single stroke or a multiple number of component
strokes. Multiple stroke flashes have 3 to 4 strokes. Lightning flash between lightning
head and earth conductor resulting travelling-wave comes down the tower and acts
through its effective impedance, raising potential of tower top to a point where
difference in voltage across insulation is sufficient to cause flashover from tower back to
conductor. Travelling wave occurs when lightning strikes a transmission line span and a
high current surge is injected on to the conductor phase. The impulse voltage and current
waves divide and propagate in both directions from the stroke terminal at a velocity of
approximately 300 meters per microsecond with magnitudes determined by the stroke
current and line surge impedance. This strike type is called back flashover (J. Rohan
Lucas, 2001). Back flashover occurs when lightning strike terminates at overhead
ground wire or tower. Back flashover occurs across insulator string if the voltage equal
or exceed the line’s critical flashover voltage (CFO) (Andrew R. Hileman, 1999). Back
flashover is most prevalent when tower footing impedance is high.
9
2.2 Fundamental of surge arrester
Generally, the use of line arrester is to decrease or eliminate lightning flashover on
transmission and distribution lines. The purpose of line arrester installation in
transmission line system is to improve the performance of overhead lines with poor
shielding or with very high tower footing impedance. Arresters avoid lightning
flashovers since transmission lines insulation voltage is higher than the residual voltage
developed across the arresters, either due to back flashover or shielding failure [9]. The
lightning arrester is a non-linear device that acts as an open circuit to low potentials, but
conducts electrical current at very high potentials. When lightning strikes a line
protected with a lightning arrester, the non-linear resistance draws the current to ground.
Surge arresters are the primary protection against atmospheric. There are generally
connected parallel with the equipment to be protected to divert the surge current. One of
the most common lightning arresters is the MOV (Metal Oxide Varistor). The MOV has
a piece of metal oxide that is joined to the power and grounding line by a pair of
semiconductors. The semiconductors have a variable resistance dependent on voltage.
When the voltage level in the power line is at the rated voltage for the arrester, the
electrons in the semiconductors flow in a way that creates a very high resistance. If the
voltage level in the power line exceeds the arrester rated voltage, the electrons behave
differently and create a low resistance path that conducts the injected lightning current to
the ground system [10]. During lightning overvoltage, surge arrester plays an important
role in limiting voltage levels and protecting power system components. Surge arresters
used for protection of exterior electrical distribution lines will be either of the Metal-
Oxide Surge Arrester (MOSA), with resistors made of zinc-oxide (ZnO) blocks, or
gapped type with resistors made of Silicon-Carbide (SiC). Silicon carbide arresters are
developed in power systems to protect the equipment from lightning over voltages. But
this kind of surge arresters has some advantages, such as negligible power losses, low
level reliability and low speed response to the over-voltages. So, silicon carbide arresters
are replaced by metal oxide surge arresters.
10
2.2.1 Metal Oxide Surge arrester (Zine oxide)
The substitution of silicon carbide arresters with zine oxide surge arresters has brought
benefits to overvoltage protection such as higher energy absorption capacity coupled
with most simultaneous action by parallel arresters in the same line branch. Metal Oxide
is a ceramal of zinc oxide with admixtures of other metal oxides such as bismuth, cobalt,
manganese and aluminium. Metal-oxide (MO) surge arrester is very important
protection device in power systems and widely used as protective devices against
switching and lightning over-voltages in power systems [11]. Since there are no series
gaps in metal-oxide surge arresters, the arresters continuously withstand the operating
voltage applied. In order to improve performance and maximize applications of metal-
oxide surge arresters, polymer housings have been used to replace porcelain housings.
[11].
Figure 2.2: Porcelain housing metal oxide surge arrester [12]
11
Figure 2.2 shows the porcelain housing TLA containing a single column of ZnO
blocks, all individually extensively routine-tested during manufacture, dispersed with the
necessary spacers as determined by the electrical design for the arrester. Longer arresters
often require external grading or sealing ring to maintain a uniform and acceptable
voltage stress along their length. Operation of such arrester without this grading ring
therefore may lead to failure and invalidates our guarantees/warranties.
2.3 V-I characteristics
Figure 2.3:V-I characteristics of MO arrester 336kV [12]
Figure 2.3 shows the V-I characteristics of MOV arrester. The distinctive features of the
MO arresters are their extremely non-linear voltage-current or V-I characteristic,
ignorable power losses, high level reliability in the operation time, high speed response
to the overvoltage, simplicity of design, easier for maintenance and long life time.
Accurate modelling and simulation of their dynamic characteristics are very important
for arrester allocation, systems reliability and insulation coordination studies. For
switching over voltages studies, the surge arresters can be represented by their nonlinear
V-I characteristics. Metal oxide surge arresters have frequency depended properties such
as time-to-crest of the arrester current effect on residual voltage of arresters. Because of
these dynamic behaviours, surge arrester nowadays in power systems software is very
12
difficult. These V-I characteristics consist of three condition regions which are low
voltage, rated voltage and overvoltage. For the low voltage operation, MOV is not
function and leakage current about µs also draws to the ground. For the rated voltage
condition, nonlinear MOV be a high resistance and current cannot flow to the ground
and for the voltage applied to the MOV exceed from the their rating, non-linear
resistance become low resistance and current can flow to the ground [12].
2.4 Types of surge arrester model
There are various surge arrester model were proposed nowadays such as IEEE, Pinceti,
Fernandez, Schmith, Tominaga, Kim, Mardira, Popov and CIGRE model. However the
most three popular model that always used for study about surge arrester nowadays as
follows.
2.4.1 Pinceti model
Figure 2.4:Pinceti Model [13]
This model has been proposed by Pinceti and Gianettoni as in Figure 2.4 [13]. This
model is based on IEEE model such in Figure 2.5 with some minor different. All
13
necessary data are easily collected in datasheets, there is no need for an iterative
correction of the parameters, and the model’s performance is accurate. The capacitance
is eliminated, since its effect on model behaviour is negligible and only electrical
parameters are used. The two parallel resistances are substituted for only resistance, R
about 1MΩ replaced between the input terminals only to avoid numerical oscillations
and nonlinear resistors A0 and A1 can be estimated by using the V-I characteristics
curves that suggested by IEEE working group 3.4.11. The two non-linear resistances A0
and A1 are separated by a L1. Thus A0 and A1 are essentially in parallel and
characterize the static behaviour of the Metal Oxide Surge Arrester (MOSA). For fast
rising surge currents, the impedance of the filter becomes more significant, indeed the
inductance L1 derives more current into the non-linear branch A0. Since A0 has a higher
voltage for a given current than A1, the model generates a higher voltage between its
input terminals. The important point is the criteria for choosing of the value of inductive
parameters [14].
2.4.2 IEEE model
Figure 2.5: IEEE Model [10]
IEEE group proposed this model includes the nonlinear resistors, designated by A0 and
A1 separated by RL low pass filter where their parameters are calculated from the
14
estimated height of the arrester. For slow front surges, the R-L filter has very little
impedance and the two non-linear sections of the model are essentially in parallel. For
fast front surges, the impedance of the R-L filter becomes more significant and causes a
current distributed between the two branches. This results in more current in the
nonlinear section designated by A0, than in the section designated by A1. Since
characteristic A0 has a higher voltage for a given current than A1, the result is that the
arrester model generates a higher voltage due to high frequency current are forced by L1
inductance to flow more in the A0 resistance than in the A1 resistance. This model
yields good results for arrester discharge voltages, when the discharge current has a time
to crest within the range of 0.5 to 45μs. The major problem associated to it is to calculate
its parameters. The IEEE Working Group suggests an iterative method, where
adjustments are necessary to achieve better results. The initial parameters can be
obtained through formulas that take into account both the electrical data (residual
voltages), and the physical parameter (overall height, block diameter, columns number)
[14].
2.4.3 Fernandez-Diaz
Figure 2.6: Fernandez Model [15]
Figure 2.6 shows a model proposed by Fernandez and Diaz. This model has recently
been developed which is recommended by IEEE and Pinceti Model. The value of non-
15
linear resistor A0 and A1 are connected in parallel and separated by inductance, L1.
Capacitance, C is the value of terminal to terminal of capacitor and the resistor represent
of arrester which has the value of the whole resist. The capacitance, C represents the
external capacitance associated to the height of the arrester. The inductance L1, has the
most influence on the result and a formula. L1 should be adjusted by a try and error
procedure to match the residual voltages for lightning discharge current published in
manufacturer’s catalogue. The resistor R0 is used to avoid numerical oscillations when
running the model with digital program [15].
2.5 Transmission line tower
Transmission line system is one of the important things to be modelling in order to test
the effectiveness of surge arrester. So, transmission line system consists of right cable
parameter and transmission line tower parameter. The representation of transmission line
can be modelled by using ATP software. This software offers some transmission line
system model such as Bergeron, PI, J. Marti, Noda and Semlyen. The most commonly
used transmission line model in Malaysia is Bergeron model because this model
considers all transmission line tower parameter such as cross-arm, insulator string, tower
surge impedance and footing resistance. This model basically is based on distributed
LC-parameter travelling wave line model with lumped resistance. This time-domain
Bergeron model is commonly used in power system transient fault analysis (Bin Li et al,
APPEEC 2009). Figure 2.7 shows an actual Bergeron model for 132kV transmission
line in Malaysia [9]. This Bergeron transmission line tower model type called double
circuit multi-storeys model. To represent a real transmission line tower, several
parameters should be considered for modelling such as cross arm, insulator string and
tower surge impedance. Bergeron Model accurately represents only fundamental
frequency (50Hz). There for the surge impedance is constant.
One of the more well-known models is the multistory model designed by Masaru
Ishii (M. Ishii et al., IEEE, 1991). A multistory tower model basically is composed of
distributed parameter lines with parallel RL circuits and has been recommended by the
16
Japanese Guideline of insulation design/coordination against lightning (Takamitsu Ito et
al., IEEE, 2003). This model is widely used for lightning surge analysis in Malaysia.
Figure 2.7:132kV multi-storey transmission line [9]
17
2.5.1 Cross arm
Cross-arms are used as transmission-line supports for 132kV and 275kV tower. In ATP
software, transmission line cross arm are represented by distributed constant line
branched at junction point. Their surge impedance given by:
𝑍𝐴𝐾 = 60 ln(2ℎ/𝑟𝐴) (2.1)
Where h is cross-arm height (m)
rA is cross-arm radius (m2)
2.5.2 Tower surge impedance
Calculation for tower surge impedance parameter of both shield wire and phase
conductor for cylindrical tower is approximated by:
𝑍 = 60 ln(√2 (2ℎ
𝑟) − 1) (2.2)
Where h is tower height (m)
rA is tower radius (m2)
2.5.3 Tower footing resistance
Tower footing resistance play important role because more lower the value of tower
footing resistance, the easier lightning discharge current flow to ground. A footing
resistance model incorporating soil ionization effect can be approximated as follow:
RT =𝑅0
√1+(𝐼
𝐼𝑔) (2.3)
Where R0 is footing resistance at low current and low frequency
I is strike current through resistance
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Ig is limiting current to initiate sufficient soil ionization
Ig= 𝐸0𝜌
2𝜋𝑅02 (2.4)
Where 𝜌 is soil resistivity (Ωm)
E0 is soil ionization gradient (400Kv/m)
2.5.4 Insulator string
The insulator is modelled as a stray capacitor connected in parallel with a voltage
controlled switch as shown in Figure 2.8. The string which consists of glass insulators,
provides an equivalent capacitance used in the model. Insulator supports the conductor
by providing mechanical support that depends on its normal operating and transient
voltage.
Figure 2.8: Insulator string [9]
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2.6 Lightning source
Lightning impulse current of large magnitudes will strike a tower top or overhead
ground wire causing back flashover across insulator string. The type of current shape
used for this model is 8/20µs 10kA. Figure 2.9 shows the typical lightning surge. The
duration of the lightning stroke is usually less than a couple of hundred microsecond.
The industry accepted 8 x 20 current wave shown in figure as a reasonable
approximation of a lightning surge.
Figure 2.9: Time duration of a typical lightning surge [1]
Current
Time
20
CHAPTER 3
RESEARCH METHODOLOGY
3.1 Introduction
This chapter defines the necessary step to complete this project. This chapter describes
start study of lightning characteristics, surge arrester models, transmission line cable
data and ATP software. The steps diagram describes related activities to be done in each
stage so ensure this project could be finished properly and successfully as planning.
Below is the step of project methodology.
a) Study characteristics of lightning phenomenon
Preliminary studies about lightning have done on the previous chapter to know more
about lightning characteristics. The source of information such as IEEE journal and
paper, thesis and trusted web from internet.
b) Surge arrester study
The next step is study about surge arrester model such as IEEE, Schmidt, Fernandez
and Haddad. These models have related information with Pincetti model. When got
the right Pinceti parameter, the modelling arrester can be done using ATP software
easily.
c) Transmission line study
For this project 132kV transmission line system is chosen. This study modelled 7
transmission lines and is connected through 132kV overhead transmission line cable.
Cable data was used from cable datasheet that recognized by Tenaga Nasional
Berhad (TNB). The full transmission line parameter model calculated using certain
21
formula included shield wire, phase conductor, insulator string, cross-arm, tower
surge impedance, tower footing resistance. For this step, more calculation did to get
the transmission line parameter.
d) Study ATP software
Next study ATP software mean transfer all transmission line and Pinceti surge
arrester model parameter to ATP software. Before arrester model is installed to
transmission line tower, testing did to single arrester model first to ensure the
arrester will function properly. Heidler lightning surge model was used to represent
for real lightning surge.
e) Observe voltage at transmission line tower
For the last step, some comparisons did on voltage value such as between installed
surge arrester and without arrester. Arrester will install between phase conductor and
ground. The result will be analyzed at this step.
3.2 Study Alternative Transient Program (ATP) software
3.2.1 Introduction
The software used for modelling of the overhead transmission line system as ATP. ATP
is considered the most widely used for system transient simulation. It can simulate
overvoltage problem such lightning phenomena and switching problem occurring in
electric power. It has been continuously developed through international contributions.
3.2.2 Operating principle of ATP
The ATP program calculates variables of interest within electric power systems as
functions of time, typically started by some disturbances. Fundamentally, the trapezoidal
rule of integration is used to solve the differential equations of system components in the
time domain. ATP has many models including rotating machines, transformers, surge
arresters, transmission lines and cables. With this digital program, complex networks of
22
arbitrary structure can be simulated. Analysis of control systems, power electronics
equipment and components with nonlinear characteristics such as arcs and corona are
also possible. Symmetric or unsymmetrical disturbances are allowed, such as faults,
lightning surges, or any kind of switching operations including commutation of valves.
Calculation of the frequency response of phase networks is also supported [16].
For this study purpose, ATP software version 1.0 is used because this software is
more user friendly compare with other software because the user can build a graphical
picture of an electric circuit by selecting components from menus. ATP software has
two parts which are ATP Draw and ATP Plot. ATP draw supports about 70 standard
components. ATPDraw is most valuable to new users of ATP and is an excellent tool for
educational purposes. The possibility of building up libraries of circuits and sub-circuits
makes ATPDraw a powerful tool in transient’s analysis of electric power systems [16].
ATP plotXY used to display output such waveform of voltage, current and lightning
strike. Some of the typical applications of ATP software are:
a) Lightning overvoltage studies
b) Transmission lines and cable with distributed and frequency-dependent parameter
c) Elements with nonlinearities: transformers including saturation and hysteresis
arrester
d) Ordinary switches, time-dependent switches, statistical switches.
e) Switching transient and fault studies
f) Statistical and systematic overvoltage studies
g) Transient stability and motor start-up
The following supporting routines are available in ATP:
Line constant, cable constant and cable parameter for calculation of electrical
parameters of overhead lines and cables.
Generation of frequency-dependent line model input data: JMARTI setup,
BEGERON setup, SEMLYEN setup and NODA setup.
Calculation of model data transformer (XFORMER and BCTRAN)
23
ATPDraw supports most of the frequently used components in ATP. The components as
Figure 2.10 are single phase as long as nothing else is specified.
Figure 3.1: Main window
3.2.3 Plotting on ATP
ATP is interfaced with these post-processors by the disk files. Their main function is to
display simulation results in time-domain or frequency-domain. Data from ATP
simulation are stored in a file having extension.pl4. Processing can be off-line or on-line.
The latter display results while simulation is proceeding and available only if the
operating system provides concurrent PL4-file access for ATP and the post-processor
program.
24
Figure 3.2: Plotting program in ATP
In ATP, two most widely-used plotting programs are PLOTXY and GTPPLOT. PlotXY
is a WIN32 plotting program originally designed for ATP-EMTP software. It is mainly
designed to make, as easy and fast as possible for line plots in Microsoft Windows
environments. It can post-process plotted curves; algebraic operation, computation of
Fourier series coefficients, etc. It has an easy-to-use graphical user interface, and its 32-
bit code provides very fast operation. Up to 3 PL4 or ADF files can be simultaneously
held in memory for easy comparison of various data, and up to 8 curves per plots versus
time or X-Y plots are allowed. It has automatic axis-scaling, can plot with two
independent vertical axes, and provides easy tools for factors, offsets, and zoom support,
and a graphical cursor to see values in numerical format. It also can export screen plots
as Windows Metafile via win32 clipboard. Figures 3.3 and 3.4 below are examples for
plotting via PLOTXY [16].
3.3 Study lightning source parameter
To design surge arrester, the characteristics of lightning should study first. This because,
the surge arrester designed will be accurate and can be lightning stroke protection. For
this analysis purpose, the lightning current impuls of 8/20µs waveshape is chosen
according to recommended waveform by IEEE. The Heidler Type was being used in this
analysis regarding to its simple data in order to determine the front time and duration of
66
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