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STUDY OF BEHAVIOR OF SURGE ARRESTER UNDER LIGHTNING STRIKE

DZULHAIDI BIN ALI

A project report submitted in partial fulfillment of the requirement for the award of the Degree of Master of Electrical Engineering

Faculty of Electrical and Electronics Engineering Universiti Tun Hussein Onn Malaysia

JULY 2015

vi

ABSTRACT

Surge arrester is one of the important component in the electrical system network either it is in a low voltage system or high voltage system. The purpose of surge arrester is generally to limit or suppress the overvoltage due to lightning phenomena or switching activities of in network. In this project, the design of model surge arrester and we simulate it using computer software named Alternative Transient Program (ATP) is most popular to study the transient time. By using this software, the behavior of surge arrester during the lightning can be identified and this behavior can be seen from this simulation. Two types of different metal oxide varistor (MOV) used in constructing this surge arrester for simulation. Each of type will be execute in two models of surge arresters which named by IEEE Model and Pincetti-Gianettoni Model. With three-tier device voltage of 50 kV, 100 kV and 200 kV with the setting 1.2 / 50 μs were injected to determine and study the output of the surge arrester. From the finding of this project the output voltage value is too small compared to the one injected where for IEEE model is only 1% and Pincetti-Gianettoni Model is 11%.

vii

ABSTRAK

Peranti penangkap kilat ialah komponen paling penting dalam rangkaian sistem elektrik sama ada sistem voltan rendah atau sistem voltan tinggi. Tujuan peranti penangkap kilat ini biasanya adalah untuk menghadkan atau memintas voltan lebih yang disebabkan oleh fenomena kilat atau aktiviti pengsuisan rangkaian. Tujuan projek ini adalah untuk mereka bentuk model peranti penangkap kilat dan simulasi model ini akan menggunakan perisian komputer yang dinamakan sebagai Program Transient Alternatif (ATP) suatu perisian yang sangat popular digunakan untuk mengkaji pada waktu fana. Melalui perisian ini, perbezaan kelakuan peranti penangkap kilat sewaktu kilat boleh dikenalpasti dan kelakuan peranti ini dilihat daripada hasil simulasi tersebut. Terdapat dua jenis perbezaan oksida logam rintangan boleh ubah (MOV) yang digunakan didalam pembinaan peranti penangkap kilat tersebut dipilih untuk simulasi. Setiap jenis MOV akan digunakan didalam dua model peranti penangkap kilat yang dinamakan sebagai Model IEEE dan Model Pinceti- Gianettoni. Setiap litar model ini menggunakan tiga peringkat voltan iaitu 50 kV, 100 kV dan 200 kV dengan tetapan 1.2/50 µs yang disuntik untuk menentukan dan mengkaji keluaran daripada peranti penangkap kilat ini. Penemuan di akhir projek ini untuk setiap litar model tersebut, nilai voltan keluaran adalah terlalu kecil berbanding dengan nilai masukkan dimana untuk Model IEEE hanya 1% dan Model Pinceti-Gianettoni sebanyak 11%.

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CONTENTS

TITLE i DECLARATION ii DEDICATION iv ACKNOWLEDGEMENT v ABSTRACT vi ABSTRAK vii CONTENTS viii LIST OF TABLES xi LIST OF FIGURES xii LIST OF SYMBOLS AND ABBREVIATIONS xiv

CHAPTER 1 INTRODUCTION 1.1 Project Overview 1 1.2 Objectives of Project 2 1.3 Scopes of Project 2 1.4 Problem Statement 2 1.5 Organization of Report 3 1.6 Conclusion 4

CHAPTER 2 SURGE ARRESTER CHARACTERISTICS: A REVIEW 2.1 History of Arrester Technology 5 2.1.1 Simple Rod Gap 5 2.1.2 Electrolytic Arrester 7 2.1.3 Oxide Film Arrester 9 2.1.4 Gapped Silicon Carbide Surge Arrester 9

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2.2 Metal Oxide Surge Arrester 11 2.2.1 IEEE Model of Surge Arrester 12 2.2.2 The Pinceti-Gianettoni Model Surge 15 Arrester 2.3 Lightning on Overview 16 2.4 Model Mathematics for Surge Arrester 18 2.5 Model Construction for Surge Arrester 18

CHAPTER 3 ATP SURGE ARRESTER MODEL FOR SIMULATION 3.1 Introduction 21 3.2 Flow Chart of Project 21 3.2.1 Preparation Model of Surge Arrester in 24 ATP Software 3.2.1.1 IEEE Model Circuit in ATP Software 24 3.2.1.2 Pinceti-Gianettoni Model Circuit in ATP 25 Software 3.2.2 Calculation of Parameter in the IEEE Model 25 of Surge Arrester 3.2.3 Calculation of Parameter in the Pinceti- 26 Gianettoni Model of Surge Arrester 3.2.4 Setting of Lightning Impulse Waveform 26 3.2.5 V-I Characteristic Curve for MOV 27 3.2.6 Simulation of the Modeling Circuit 31 3.3 Conclusion 32

CHAPTER 4 RESULT, ANALYSIS AND DISCUSSION 4.1 Introduction 34 4.2 Output from Simulation Model 34 4.2.1 IEEE Model for MOV Type 1 34 4.2.2 IEEE Model for MOV Type 2 36

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4.2.3 Pinceti-Gianettoni Model for MOV Type 1 39 4.2.4 Pinceti-Gianettoni for MOV Type 2 41 4.3 Comparisons between IEEE Model and Pinceti- 44 Gianettoni Model 4.4 Conclusion 45

CHAPTER 5 CONCLUSION AND RECOMMENDATION 5.1 Introduction 47 5.2 Conclusion 47 5.3 Recommendation 48

REFERENCES 49 VITA 51

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LIST OF TABLES

3.1 The characteristic of MOV for Type 1 28 3.2 The characteristic of MOV for Type 2 30 4.1 Summary of all simulation for Type 1 and Type 2 44 MOV

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LIST OF FIGURES

2.1 Early power system lightning arrester 6 2.2 Horned Gapped Arrester 7 2.3 Electrolytic Arrester 8 2.4 Pellet Type Oxide Film Arrester 1915 9 2.5 First Silicon Carbide Surge Arrester 10 2.6 Schematic representation of the magnitude of 12 voltages and overvoltage versus duration of their appearance. 2.7 IEEE Model of surge arrester 13 2.8 Non-linear characteristic for A0 and A1. The 13

voltage is in p.u. referred to the Ur8/20 2.9 Pinceti-Gianettoni Model for surge arrester 14 2.10 Diagram showing lightning strike 16 2.11 Standard waveform for lightning 17 2.12 Construction of Surge Arrester for Porcelain 19 Housing 3.1 Flow chart of Project 22 3.2 The blocks diagram for modeling circuit in ATP 23 3.3 IEEE Model circuit draw in ATP software 23 3.4 Pinceti-Gianettoni Model circuit draw in ATP 24 software 3.5 Circuit to identify the Lightning Impulse Waveform 25 3.6 Standard Lightning Waveform with 50 kV peak 26 value 3.7 Type 1 of MOV for V10 125 kV 29

3.8 Type 2 of MOV for V10 248 kV 30 3.9 The complete IEEE model circuit in ATP software 31 3.10 The complete Pinceti-Gianettoni Model in ATP 32 software

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4.1 Output Waveform for peak of Input is 50 kV 34 4.2 Output waveform for peak of Input is 100 kV 34 4.3 Output waveform for peak of Input is 200 kV 35 4.4 Output waveform for peak of Input is 50 kV 36 4.5 Output waveform for peak of Input is 100 kV 37 4.6 Output waveform for peak of Input is 200 kV 38 4.7 Output waveform for peak of Input is 50 kV 38 4.8 Output waveform for peak of Input is 100 kV 39 4.9 Output waveform for peak of Input is 200 kV 40 4.10 Output waveform for peak of Input is 50 kV 41 4.11 Output waveform for peak of Input is 100 kV 42 4.12 Output waveform for peak of Input is 200 kV 42 4.13 The differences of type of MOV 44

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LIST OF SYMBOLS AND ABBREVIATIONS

A - Ampere kA - Kilo Ampere V - Volt kV - Kilo Volt

Vm - Maximum Voltage

Vr - Rated Voltage

Vn - Normal Voltage F - Frequency 흮 - Ohm M 흮 - Mega Ohm µs - Micro Second ms - Mili Second µH - Micro Henry pF - Pico Farad p.u. - Per Unit m - Meter U - Voltage I - Current R - Resistor L - Inductance C - Capacitor T - Time

Tsta - Time Start

Tsto - Time Stop m² - Meter Square A - Area

CHAPTER 1

INTRODUCTION

1.1 Project Overview

In recent years, using metal oxide (ZnO) arresters is a common and prevalent affair for transformers, capacitance banks etc protection against impulse of overvoltage. Therefore, correct and accurate investigation of ZnO arresters behavior in power networks requires correct simulation for the existing transient state software. Several papers have been presented under arresters modeling title [3, 4, 5, and 6] each has concerned different parameters in simulation process. At the beginning, the arrester was just modeled by a nonlinear resistance due to the nonlinear feature of the varistor tablets. The leakage capacitances stand around the arrester were then under consider in transient state simulations due to high frequency bands (spectrums) existence. This was specially confirmed according to the crystal shaped structure of varistors. In investigations accomplished between the waveforms resulted by voltage residual and the arresters discharge current, a series inductance was added to the arrester model due to a short delay exists in current peak and the voltage peak waveforms. Some other models were reported by Daniel (1985) and then with IEEE workgroup (1992) because the mentioned inductance was just properly performing in a limited range of frequencies. The IEEE model was an appropriate model from quality and quantity view point but was sensibly losing its efficiency and was creating difficulties in modeling process due not existence of voltage switching information in majority of catalogs (according to difficulty of such test). Therefore, other models were 2 presented to overcome such problem inspired by this model (Kim at el., 1996; Pinceti and Giannettoni, 1999). In this study, the residual voltage of the arrester of qualitative and quantitative aspects is under consider as well as the discharged energy value, unlike other papers just have investigated the maximum value of impulse caused residual voltage.

1.2 Objectives of this project

a) To design surge arrester model using Alternative Transient Program, ATP. b) To study the behavior of surge arrester when lightning strike. c) To compare the output voltage between IEEE Model and Pinceti- Gianettoni Model.

1.3 Scopes of this project

a) Simulation only under lightning condition using Alternative Transient Program, ATP. b) Simulation only with using two type of metal oxide varistor.

1.3 Problem Statement

Lightning is the most frequent cause of overvoltage on distribution systems. Basically, lightning is a gigantic 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. The voltage of a lightning stroke may start at hundreds of millions of volts between the cloud and earth. Although these values do not reach the earth, millions of volts can be delivered to the buildings, trees or distribution lines struck. In the case of

3 overhead distribution lines, it is not necessary that a stroke contact the line to produce overvoltage dangerous to equipment. This is so because "induced voltages" caused by the collapse of the electrostatic field with a nearby stroke may reach values as high as 300 kV. Surge arrester is the one way to resolve overvoltage due to the lightning strike. This because the special characteristic material used in the surge arrester called metal oxide surge arrester (MOSA).

1.5 Organization of Report

This report is divided into five main chapters which will explain the structure of the project. Brief description of each chapter as follows:

Chapter 1: This chapter explains the general introduction of the metal oxide (ZnO) used as a surge arrester and the research has been previously done. This chapter also includes the objectives, scopes, and problem statement of this project.

Chapter 2: Chapter two entitle literature review gives minutely explanations of the history, types of surge arrester and modelling circuit of surge arrester. Actually nowadays studying in surge arrester is easier with due to modelling circuits and many infrastructures that are available.

Chapter 3: In this chapter, is the explanation the method for constructing this project. For simulation, this project is using of the Alternative Transients Program (ATP) where this software is most familiar in transient power analysis.

Chapter 4: This chapter includes the results of the simulation and the discussions. It will discuss of result from the simulation, comparison between the model and the relative error of each model.

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Chapter 5: This is the closing chapter of this project. In this chapter, it will cover the conclusion and recommendations that has been stated. From this recommendation, it can be use for the further studies on the surge arrester.

1.6 Conclusion

In this chapter, is more explained initial of introduction of this project and structure of this project. Objective and scope of this project also mention in this chapter to explain the purpose and direction of project. Also the organization of project is covered in this chapter to give overview of project.

CHAPTER 2

SURGE ARRESTER CHARACTERISTICS: A REVIEW

2.1 History of Arrester Technology

The earliest roots of lightning protection of power systems dates back to the middle of the 18th century from 1890 to 1930 will be covered in this part of the history of lightning protection of power systems. During this era, lightning protection of electrical equipment divides into many subcategories, such as communications, electronics, radio towers, railroad (DC), and the one discussed herein, power systems. Protection of the telegraph gave birth to the gapped device first called an arrester. It wasn’t until the 1890’s that power lines were added to the utility poles crisscrossing the country and immediately needed arresters that could protect them from lightning also. The fundamental difference however is that telegraph lines were not energized 100% of the time as are power lines and the designs of the pre 1890 arrester used to protect the telegraph lines just did not meet the needs of power systems.

2.1.1 Simple Rod Gap

Power system engineers interested in lightning protection soon learned that the gap, what was sufficient for telegraph protection, was not of sufficient separation distance to interrupt the current from the 60 Hz power arc after the lightning surge was over. This current flowing off the power system from the AC source became known as power 6 follow current and it remained a significant challenge to the arrester designers for this entire era. They quickly learned that the only way to interrupt this power follow current once it flashed over was to turn off the AC power or insert a resistance into the circuit. The early means of inserting resistance in series with the gap was to change the size of the gap. In Figure 2.1, the arrester inventor, Sperry, ran the ground lead of the arrester through a magnetic solenoid. If the gap sparked over from lightning and was followed by power system current, it would pulse the solenoid, which in turn would allow the gap to snap open. The added distance in the gap increased the length of the arc, which is a common means of increasing the arc resistance. This increase in resistance resulted in interruption of the arc when the voltage crossed zero. It would appear that the Sperry arrester would be a maintenance issue in that it needed to be reset after a strike: something more was needed.

Figure 2.1: Early power system lightning arrester [7]

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The second method of increasing the series resistance of the gap was to use a linear resistor; however, as the system voltages increased this also became a problem. A third design that can still be seen protecting insulators today was the Horned Gapped Arrester. Figure 2.2 shows an 1896 version of this arrester type. The principal behind this type of arrester is that as the arc burns, the magnetic field pushes the arc out toward the ends of the electrodes. Since the gap size increases from the bottom to the top, the length of the arc increases, which in turn increases its resistance. This action limits the current to levels that can lead to extinguishment at voltage zero.

Figure 2.2: Horned Gapped Arrester [7]

2.1.2 Electrolytic Arrester

In 1908 the new arrester type called electrolytic arrester was introduced and was the first design to use a nonlinear current-limiting resistance element to limit follow current and allow arc interruption. The design of electrolytic arrester consisted of a sphere gap in series with a tank containing aluminum electrodes separated by a liquid electrolyte as

8 per Figure 2.3. The aluminum electrodes were formed into cells by electrolytic ally depositing a non conducting film of aluminum hydroxide thick enough to withstand the applied voltage. A lightning surge would momentarily puncture the non conducting aluminum hydroxide film. However, the follow current from the system caused the punctured hole to heal itself by the same electrolytic mechanism used to initially coat the aluminum electrodes. The main disadvantage of the electrolytic arrester was the electrolyte itself caused deterioration of the film. The electrolytic arrester, therefore, had to be recharged daily by connecting it to the power system. For the higher voltage systems, the chemical arrester, as it was known, had the answer to the series resistance issue. Arrester designers had learned that the perfect arrester would have a resistance in series with the gap that had non-linear characteristics. This means that at higher voltages and currents it would have lower resistance. This variable resistance made it possible for the arrester to conduct high lightning currents, and after the event it was also able to assist the gap to interrupt the follow current.

Figure 2.3: Electrolytic Arrester [7]

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2.1.3 Oxide Film Arrester

Figure 2.4: Pellet Type Oxide Film Arrester 1915 [7]

This new pellet type arrester had the excellent voltage and current characteristics of the aluminum cell arrester and then without a liquid dielectric as per shown in Figure 2.4. Also in this arrester had an additional advantage of lower cost and was better suited for line protection proportionate to electrolytic arrester. However, this type of arrester has some weakness such as it have a limited lifetime due to damage to the oxide film during each surge. This damage was not repairable as in the liquid oxide film arrester and it clearly more work was needed in the industry.

2.1.4 Gapped Silicon Carbide Surge Arrester

In 1926 John Robert Mc Farlin, who was still working for ESSCO, filed for a patent using a new material that he referred to as: “infusible refractory materials of limited

10 conductivity and comparatively low specific resistance in the silicon carbide family.” He goes on to state that “these properties greatly enhance the effectiveness, durability, stability and simplicity of surge arresters.” Thus began the long history of the Silicon Carbide (SiC) family of arresters shown in Figure 2.5. This type of arrester remained in production into the 1990’s in the US and is still in production in other parts of the world. As design engineering manager of the surge arrester business at Cooper Power Systems; this author personally shut down the last US based production line of this product in 1994.

Figure 2.5: First Silicon Carbide Surge Arrester [7]

It seems surprising that the introduction of the first SiC arrester did not come from GE or Westinghouse, the titans as they were in the area of overvoltage protection. Silicon carbide resistance material quickly earned the number one position in arrester designs for all voltage levels.

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2.2 Metal Oxide Surge Arrester

Metal oxide surge arresters (MOSA) are widely used as protective devices against switching and lightning pulse overvoltage occur in electrical power system. Nowadays, several types of surge arresters are available such as gapped silicon carbide, gapped or non gapped metal oxide. All type of surge arrester is operating at similar manner which mean surge arrester is high impedances at normal operating voltages and become low impedances when surge conditions. An ideal arrester must conduct electric current at a certain voltage above rated voltage, hold the voltage with little change for the duration of overvoltage and substantially cease conduction at very nearly the same voltage at which conduction started. In the other word, surge arrester constitutes an indispensable aid to insulation coordination in the power electrical systems. Figure 2.6 explained the magnitude of voltages and overvoltage in the electrical power system. Where the X axis (time) is divided into several section for fast-front overvoltage cause by lightning, in microsecond range, slow-front overvoltage by switching in millisecond range then temporary overvoltage and highest system voltage. The overvoltage can possible reached over the withstand voltage of equipment insulation especially for lightning overvoltage then the equipment insulation cannot withstand the occurring dielectric stresses. Even though a great number of surge arrester, which are gapped arrester with made from silicon carbide (SiC) are still in use but for new installation almost is using metal oxide without gaps, which means arresters with resistors made from metal oxide. If surge current in the kilo ampere range are injected into the arrester, such as in case when lightning or switching overvoltage occur, then the voltage across its terminal will remain low to protect the insulation from the effect of overvoltage.

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Figure 2.6: Schematic representation of the magnitude of voltages and overvolatages versus duration of their appearance. [8]

The non linear characteristic (V-I characteristic) of MOSA is the important factor why it is selected in the surge arrester construction. The physical construction of metal oxide surge arresters consists of metal oxide disc inside a porcelain or polymer insulator. By adding the metal oxide disc in series mean the voltages value is also increased. For the higher energy ratings can be achieved with using larger diameter of metal oxide disc or parallel columns of disc.

2.2.1 IEEE Model of Surge Arrester

The IEEE Model was recommended by IEEE W.G.3.4.11 as shown in Figure 2.7 [1]. In this model two of non linear resistor called A0 and A1 and it is separated with RL low pass filter. For arrester discharge currents with slow rising time, the influence of the

13 filter is negligible thus A0 and A1 are essentially in parallel and characterize the static behavior of the MOSA.

Figure 2.7: IEEE model of surge arrester [1]

For the fast rising surge current, the impedance of the filter become 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 input terminals, what matches the dynamic characteristics of MOSA. A0 and A1 can be derived by the curve as per Figure 2.8. The per-unit (p.u.) is referred to the peak value of the residual voltage measured during a discharge test with

10kA lightning current impulse (Ur8/20). This curve is to adjust to get a good fit with the published residual voltages for switching surge discharge currents.

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Figure 2.8: Non-linear characteristic for A0 and A1. The voltage is in p.u. referred to the

Ur8/20 [9]

The inductance L0 represents the inductance associated with the magnetic fields in the immediate vicinity of the arrester. The resistor R0 is used to avoid the numerical oscillations when running the model with a digital program. While the capacitor C0 represents the external capacitance associated to the height of the arrester. The values of

C0, L0, R0, L1 and R1 can be determined by follow a given formulas (1) to (5) and all the components is related to the physical dimensions of the arrester. [1]

(2.1)

(2.2)

(2.3)

(2.4)

(2.5)

d is the estimate high of the arrester in meter

15 n is the number of parallel columns of MO in the arrester

The component of L1 is the most influence on the result of the arrester analysis.

However the initial value of L1 is given by the physical dimensions of the surge arrester, it should be to be adjusted with try and error procedure to match the residual voltages for lightning discharge currents published in the manufacturer’s catalogue.

2.2.2 The Pinceti-Gianettoni Model Surge Arrester

Figure 2.9: Pinceti-Gianettoni Model for surge arrester [2]

From Figure 2.9, is proposed the Pinceti-Gianettoni Model for surge arrester [2]. Actually this model is based on the IEEE Model but with some modification of eliminated the capacitance, C. This capacitance is eliminated so the effects on behavior model can be negligible. This capacitance is replaced by high resistance (about 1M흮) at the input terminal and the function of this resistor only to avoid the numerical troubles. The operating principle is quite similar to that of IEEE Model surge arrester. Where the entire component is this model can be calculated following this equation: [2]

(2.6)

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(2.7)

Uris the rated voltage.

Ur1/T2 is the residual voltage at 10kA fast front current surge (1/T2µs). The decrease time is not explicitly written because different manufactures may use different values. This fact does not cause any trouble, since the peak value of the residual voltage appears on the rising front of the impulse.

Ur8/T2 is the residual voltage at 10kA current surge with 8/20 µs shape.

R0 is 1M흮 is introduced to avoid numerical instabilities. Refer to formula (6) and (7), this Pinceti-Gianettoni Model is not depending on physical dimensions and it only depend on electrical data by given from manufacturers.

2.3 Lightning on Overview

Lightning is a physical phenomenon that occurs when the clouds acquire charge or become polarized, so that the electric fields of considerable strength are created within the cloud and between the cloud and adjacent masses such as earth and other clouds, [12]. When these fields become excessive, to the extent that the dielectric (the air) of intervening space can no longer support the electrical stress, a breakdown or lightning flash occurs; this is usually a high-current discharge. This situation can be depicted in Figure 2.10.

Also lightning is the main reason for outages in transmission and distribution lines [12]. The lightning problem is classified as a transient event. When lightning strikes a power line, it is like closing a “big switch” between a large current source and the power line circuit. The sudden closing of this “big switch” causes an abrupt change in the circuit conditions, creating a transient. There is also the case when the lightning strikes the vicinity of the power line and the large magnetic field generated from the lightning current cause mutual coupling between the power line and the lightning. The

17 event alters the conditions of the power line circuit, as a result, produce an electrical transient. The lightning waveform can be defined in Figure 2.11.

Figure 2.10: Diagram showing lightning strike [12]

Figure 2.11: Standard waveform for lightning [12]

The study of lightning strokes in power lines is very important because it is known that lightning does strike the same structure over and again. This can be a very serious problem for power lines, typically, the highest structures located in high incidence lightning regions [14]. Any structure, no matter its size, may be struck by lightning, but the probability of a structure been struck increases with its height. Very

18 close dart leaders can make as significant a contribution as return strokes in inducing voltages and currents on power systems [9].

2.4 Model Mathematics for Surge Arrester

The V-I characteristic of a surge arrester has several exponential segments, where each segment can be approximated by

(2.8)

Where q is the exponent, q is the multiplier for the segment and Vref is the arbitrary reference voltage that normalizes the equation and prevents numerical overflow during exponentiation. The first segment can be approximated by a linear relationship to avoid numerical underflow and speed the simulation. At this first segment the resistance is should be very high since the surge arrester should have a little effect on the steady-state solution of the network. At normal steady-state operation currents of surge arrester should be less than 0.1 A. At the second segment is defined by the parameters p, q and

Vmin, which is the minimum voltage for segment. The accuracy of the surge arrester model can be enhance with multiple segment are typically used since the exponent decreases as the current level increases.

2. Model Construction for Surge Arrester

Before construct model of surge arrester, the some data must be obtained from the manufacturer of surge arrester. The data is: a) Manufacturer’s rating and characteristic b) Manufacturer’s V versus I curve

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At the factory, the manufacturer is tested all single disc of metal oxide with a current pulse and record their reference voltage. A typical test pulse current has a peak 10 kA with an 8/20 µs waveform has been used during their testing. The peak voltage from result testing of this typical pulse current is called reference voltage V10, the voltage at 10 kA for a single column of surge arrester. The V-I characteristic curve of metal oxide curve is often use the value of V10 as the 1 per-unit (p.u.) value. The voltage from V-I characteristic curve can be determine with multiply the p.u. metal oxide by the

V10 for that rating.

The selection of reference voltage proportional to the arrester rating V10, number of parallel columns of discs and voltage versus current (V-I) characteristic in p.u. of the reference voltage is the next step. Surge arrester V-I characteristic choose is depends upon the type of transient being simulated since current waveform with faster rise times will result in higher peak voltages. Manufacturer of surge arrester often publish several curves such as: a) The 8/20 µs characteristic applies for typical lightning surge simulations. b) The front wave (FOW) characteristic applies for transients with current. c) The 36/90 µs characteristic applies to switching surge simulations. d) The 1 ms characteristic applies to low frequency phenomena. For each test waveform, manufacturers may supply minimum and maximum curves. The maximum curve is generally used since it results in the highest overvoltage and the most conservative equipment insulation requirements. The minimum curves are used to determine the highest energy levels absorbed by the surge arrester. In Figure 2.12 is shown the construction of surge arrester for porcelain type. Where in this figure, also has shown the arrangement of MOV inside the porcelain housing. The blocks MOV is arrange in series along of surge arrester.

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Figure 2.12: Construction of Surge Arrester for Porcelain Housing [12]

CHAPTER 3

ATP SURGE ARRESTER MODEL FOR SIMULATION

3.1 Introduction

This chapter will explain about surge arrester model for simulation using computer program called Analysis Transient Program (ATP). Whore this program is very similar for studying in transient analysis and the result is must faster. The entire parameters for modeling circuit either IEEE Model or Pinceti- Gianettoni Model will be identified in this chapter. All these parameters will be calculated using the formula as explained in the previous chapter. Also this chapter will explain the differences of the input lightning waveform between 50 kV to 200 kV. So to make it simple, three different inputs lightning waveform is selected for this project which is 50 kV, 100 kV and 200 kV. The type of metal oxide varistor or surge arrester is selected from two type of surge arrester called Type 1 and Type 2. It is to understand the effect of lightning impulse waveform when it is injected into these modeling circuits. The entire output waveform for all simulation will be recorded for analysis and further discussion in the next chapter.

3.2 Flow Chart of Project

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This sub chapter will explain the simulation step by step from beginning until the output waveform can be recorded. Figure 3.2 shows the flow chart of this project. This flow chart is important because of it is the standard of procedure to complete this project. With this flow chart, the mistake due to human error can be minimizing. It is also easy to retrace and counter check all the process followed and not miss out. So, the flow chart is very important for completing this project successfully.

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START

PREPARE THE MODELING CIRCUIT IN ATP SOFTWARE

CALCULATE THE PARAMETER OF R0, R1, L0, L1, C AND R

SETTING THE LIGHTNING IMPULSE WAVEFORM

IDENTIFY TYPE OF METAL OXIDE VARISTOR

SIMULATE CIRCUIT MODEL IN ATP SOFTWARE

NO RIGHT

YES

RECORD THE OUTPUT WAVEFORM

END

Figure 3.1: Flow chart of Project

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3.2.1 Preparation Model of Surge Arrester in ATP Software

This project is divided by three sections, where the first section is the Input Section, second section is the Modeling Circuit (IEEE Model or Pinceti-Gianettoni Model) and the last section is the Output Section. Figure 3.2 is shows that the blocks diagram for preparing the modeling circuit for surge arrester in the ATP software.

Input (Lightning Model of Surge Output (Load)

Impulse Waveform) Arrester

Figure 3.2: The blocks diagram for modeling circuit in ATP

3.2.1.1 IEEE Model Circuit in ATP Software

Figure 3.3: IEEE Model circuit draw in ATP software

REFERENCES

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