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UNIVERSITI PUTRA MALAYSIA

INVESTIGATION ON THE ELECTRICAL PERFORMANCES OF A 10 kV POLYMER INSULATOR WITH SURFACE MOSS DEPOSITION

FARAH ASYIKIN ABD RAHMAN

FK 2018 148

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Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of

Master of Science

July 2018

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PMAll material contained within the thesis, including without limitation text, logos, icons, photographs and all other artwork, is copyright material of Universiti Putra Malaysia unless otherwise stated. Use may be made of any material contained within the thesis for non-commercial purposes from the copyright holder. Commercial use of material may only be made with the express, prior, written permission of Universiti Putra Malaysia. Copyright © Universiti Putra Malaysia

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PMAbstract of thesis presented to the Senate of Universiti Putra Malaysia in

fulfilment of the requirement for the degree of Master of Science


By


July 2018

Chair : Mahdi Izadi, PhD Faculty : Engineering

The polymer insulator is known for its superior insulation performance due to its hydrophobicity and has been widely used in power systems especially for distribution networks. In sustaining this upper hand status, several extensive studies have been undertaken in evaluating and investigating the relationship between hydrophobicity and the electrical performance of polymer insulator with pollution severity, weather and ultraviolet (UV) effects. For a tropical country such as Malaysia, the issue of the formation of moss deposited on the insulator surface as a part of pollution severity should be considered. In this study, a 10 kV polymer insulator was selected as a case subject with moss deposition on the surface. Its electrical performance was studied and compared with a clean polymer insulator through Maxwell and HFSS software simulation under both steady state and impulse voltage conditions. In addition to this study, both insulators were tested under different environmental conditions and voltage profiles in a fog chamber. The results showed that the deposited moss on the surface had a direct effect on the voltage breakdown values and that the moss can reduce the electrical stability of a power line especially a core contaminated polymer insulator under polluted air. These findings have significant implications for distribution network systems, especially in areas with a high probability of moss formation. It would be wise to take this information into account when designing any new line projects or improving existing networks by setting the proper insulation level.

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PMAbstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia

sebagai memenuhi keperluan untuk ijazah Master Sains

PENYIASATAN PRESTASI ELEKTRIK 10 kV PENEBAT POLYMER DENGAN PEMENDAPAN LUMUT DI ATAS PERMUKAAN

Oleh


Julai 2018

Pengerusi : Mahdi Izadi, PhD Fakult : Kejuruteraan

Penebat polimer dikenali sebagai penebat yang berprestasi tinggi disebabkan oleh sifat kalis airnya dan ia telah digunakan secara meluas dalam sistem kuasa terutama di bawah rangkaian pengagihan. Justeru, dalam usaha mengekalkan prestasi ini, beberapa kajian menyeluruh telah dilakukan dalam menilai dan menyiasat hubungan antara sifat kalis air dengan prestasi elektrik penebat polimer di bawah ketegaran pencemaran, cuaca dan kesan UV. Untuk negara tropika, isu pemendapan lumut pada permukaan penebat adalah tambahan kepada isu pencemaran yang perlu dipertimbangkan juga. Dalam kajian ini, penebat polimer 10kV telah dipilih sebagai kes subjek kepada isu pemendapan lumut tersebut. Prestasi elektriknya dikaji dan dibandingkan dengan penebat polimer bersih melalui simulasi perisian Maxwell dan HFSS di bawah keadaan mantap dan voltan dedenyut. Sebagai tambahan kepada kajian ini, kedua-dua penebat telah diuji di bawah keadaan persekitaran yang berbeza dan profil voltan di dalam ruang kabus. Keputusan menunjukkan bahawa lumut yang disimpan di permukaan mempunyai kesan langsung ke atas nilai pecahan voltan dan ia dapat mengurangkan kestabilan elektrik talian kuasa, terutama pada penebat yang mempunyai pemendapan lumut pada teras ketika di dalam udara tercemar. Penemuan ini mempunyai implikasi yang ketara untuk sistem rangkaian pengagihan terutama di kawasan dengan kebarangkalian pembentukan lumut yang tinggi. Adalah bijak untuk mengambil kira notasi ini apabila merancang sebarang projek pengagihan baru atau memperbaiki rangkaian sedia ada dengan menetapkan tahap penebat yang betul.

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PMACKNOWLEDGEMENTS

The completion of my Master Degree in Universiti Putra Malaysia (UPM) would not have been possible without the participation and assistance of so many people whose names may not all be mentioned. Their contributions are sincerely appreciated and gratefully acknowledged. However, I would like to express my deep appreciation and indebtedness particularly to the following: Dr. Mahdi Izadi, Prof. Ir. Dr. Mohd Zainal Abidin Ab Kadir, Dr Jasronita Jasni, Muhammad Syahmi Abdul Rahman, Norhidayu Rameli and Benny Azmi, my supervisor, co-supervisor, friend and colleagues, respectively, for their endless support, as well as their kind and understanding spirit during my course of study. Special thanks to my father, Abd Rahman Hj Yahya and my mother, Zakiah Ibrahim and siblings for their tireless support and love throughout all my studies. Their help and guidance have been invaluable to me in my life choices. To my friends and colleagues from the Centre of Electromagnetic and Lightning Protection Research (CELP), Electrical & Electronic Engineering Department UPM and PKK who in one way or another shared their support, either morally, financially or physically, thank you. Above all I thank Allah s.w.t; the author of knowledge and wisdom; for giving me the strength and ability to complete my Master Degree.

I thank you all.

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PMI certify that a Thesis Examination Committee has met on ( ...... ) to conduct the final examination of Farah Asyikin Abd Rahman on her thesis entitled “Investigation On The Electrical Performances Of A 10 kV Polymer Insulator With Surface Moss Deposition” in accordance with the Universities and University Colleges Act 1971 and the Constitution of the Universiti Putra Malaysia [P.U.(A) 106] 15 March 1998. The Committee recommends that the student be awarded the Master of Science.

Members of the Thesis Examination Committee were as follows:

Name of Chairperson, PhD Title, Name of Faculty, Universiti Putra Malaysia (Chairman)

Name of Examiner, PhD Title, Name of faculty, Universiti Putra Malaysia (Internal Examiner)

Name of External Examiner, PhD Title, Name of Faculty, Name of University, (External Examiner)

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PMThis thesis was submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirement for the degree of Master of Science. The members of the Supervisory Committee were as follows:

Mahdi Izadi, PhD Research Fellow, Faculty of Engineering, Universiti Putra Malaysia (Chairman)

Mohd Zainal Abidin Ab. Kadir, PhD Professor, PEng Faculty of Engineering, Universiti Putra Malaysia (Member)

Jasronita Jasni, PhD Senior Lecturer, Faculty of Engineering, Universiti Putra Malaysia (Member)

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PMDeclaration by graduate student

I hereby confirm that: � this thesis is my original work; � quotations, illustrations and citations have been duly referenced; � this thesis has not been submitted previously or concurrently for any other

degree at any other institutions; � intellectual property from the thesis and copyright of thesis are fully-

owned by Universiti Putra Malaysia, as according to the Universiti Putra Malaysia (Research) Rules 2012;

� written permission must be obtained from supervisor and the office of deputy vice- chancellor (Research and Innovation) before thesis is published (in the form of written, printed or in electronic form) including books, journals, modules, proceedings, popular writings, seminar papers, manuscripts, posters, reports, lecture notes, learning modules or any other materials as stated in the Universiti Putra Malaysia (Research) Rules 2012;

� there is no plagiarism or data falsification/fabrication in the thesis, and scholarly integrity is upheld as according to the Universiti Putra Malaysia (graduate studies) rules 2003 (revision 2012-2013) and the Universiti Putra Malaysia (Research) Rules 2012. The thesis has undergone plagiarism detection software.

Signature: ______________________________ Date: __________________

Name and Matric No: Farah Asyikin Abd Rahman (GS44147)

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PMDeclaration by Members of Supervisory Committee

This is to confirm that: � the research conducted and the writing of this thesis was under our

supervision; � supervision responsibilities as stated in the Universiti Putra Malaysia

(Graduate Studies) Rules 2003 (Revision 2012-2013) are adhered to.

Signature: Name of Chairman of Supervisor Committee: Mahdi Izadi

Signature: Name of Member of Supervisory Committee: Mohd Zainal Abidin Ab. Kadir

Signature: Name of Member of Supervisory Committee: Jasronita Jasni

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TABLE OF CONTENTS

ABSTRACT i ABSTRAK ii AKNOWLEDGEMENT iii APPROVAL iv DECLARATION vi LIST OF TABLES x LITS OF FGURES xii LIST OF ABBREVIATION xv

CHAPTER

1 INTRODUCTION 1 2 LITERATURE REVIEW 5

2.1 Introduction 5 2.2 Insulators 5 2.3 Polymer Insulators 7 2.3.1 Polymer Insulator Structure And The Engineering

Issue 9 2.3.2 Effects Of Pollution On The Electrical

Performance Of Polymer Insulator 15 2.4 Overview Of Lightning Physics 21

2.4.1 Cloud To Ground Lightning Sequence Formation 21

2.5 Overview Of The Climate, Lightning Activities And Ecology Of Malaysia 23

2.6 Overview Of Previous Studies Under Steady State Test And Transient Test Standards 24

2.6.1 Steady State Test Standards 25 2.6.2 Transient Test Standards 32 2.7 The Standard Wave Shape Of The Impulse Voltage And

Current 33 2.8 Overview On The Finite Element Method 34 2.9 Summary 37

3 METHODOLOGY 39

3.1 Introduction 39 3.2 Work Flow Of The Study 39

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3.3 Overview Of HFSS Software 41 3.3.1 General Steps In The HFSS 3D Geometry

Solution 43 3.4 Overview Of Maxwell Software 47

3.4.1 General Steps in the Maxwell 2D Geometry Solution 48

3.5 Experimental Insulator Preparation Setup 52 3.5.1 Moss Deposited Contamination Conductivity

Calculation 53 3.6 Experimental Salt Fog Chamber 54

3.6.1 Testing Standards Benchmarking 56 3.6.2 Measurement Standards 58

3.7 Chapter Summary 60

4 RESULTS AND DISCUSSION 61

4.1 Introduction 61 4.2 Simulation Of A Polymer Insulator Under A 235 KV

Lightning Impulse Voltage 61 4.3 Simulation Of The Polymer Insulator Under 10 Kv

Steady State Frequency 79 4.4 Evaluation of Insulator Performance through Impulse

Voltage Experimental Test 91 4.5 Evaluation of Insulator Performance through Steady

State Power Frequency Experimental Work 100 4.6 Chapter Summary 102

5 CONCLUSION 104

REFERENCES 106 APPENDICES 113BIODATA OF STUDENT 140 LIST OF PUBLICATIONS 141

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PMLIST OF TABLES

Table Page 2.1 Standard Insulation Levels Based On IEC 60071 [84] 35 3.1 Maximum Mesh Size For FEM Model 43 3.2 Technical Specification Of A 10 kV Polymer Insulator [90] 45 3.3 Material And Condition Parameters 45 3.4 Solution Setup Settings 47 3.5 Maximum Mesh Size For FEM Model 51 4.1 Comparison Between The Electric Field Of A Clean Insulator

Under Different Weather Conditions 66 4.2 Comparison Between The Voltage Distributions Of A Clean

Insulator Under Different Weather Conditions 66 4.3 Comparison Between The Electric Field Of The Sample P

Insulator Under Different Weather Conditions 70 4.4 Comparison Between The Voltage Distributions Of The Sample

P Insulator Under Different Weather Conditions 70 4.5 Comparison Between The Electric Field Of The Sample Q

Insulator Under Different Weather Conditions 74 4.6 Comparison Between Voltage Distributions Of The Sample Q

Insulator Under Different Weather Conditions 74 4.7 Comparison Between The Electric Field Of The Sample R

Insulator Under Different Weather Conditions 78 4.8 Comparison Between Voltage Distributions Of The Sample R

Insulator Under Different Weather Conditions 78 4.9 Comparison Between The Electric Field Of The Clean Insulator

Under Different Weather Conditions 81 4.10 Comparison Between Voltage Distributions Of The Clean

Insulator Under Different Weather Conditions 81 4.11 Comparison Between The Electric Field Of The Sample P

Insulator Under Different Weather Conditions 84 4.12 Comparison Between Voltage Distributions Of The Sample P

Insulator Under Different Weather Conditions 84 4.13 Comparison Between The Electric Field Of The Sample Q


Insulator Under Different Weather Conditions 87 4.15 Comparison Between The Electric Field Of The Sample R


Insulator Under Different Weather Conditions 90 4.17 Comparison Of Average Breakdown Voltage Of The Clean

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PMInsulator Under Various Weather Conditions 93

4.18 The Comparison Of Average Breakdown Voltage Of The Contaminated Insulator Under Various Weather Conditions 96

4.19 The Clean And Contaminated Insulator Breakdown Voltage Under Various Weather Conditions For Negative Polarity Lightning Impulse 97

4.20 Sample Of Leakage Currents Measured From Clean And Contaminated Insulators Under Various Weather Conditions 98

4.21 (cont) Sample Of Leakage Currents Measured From Clean And Contaminated Insulators Under Various Weather Conditions 99

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PM LIST OF FIGURES

Figure Page 2.1 Strain Insulators As Tension Reliever And A Mechanical 6 2.2 Illustration Of How An Insulator Is Supported On A Pin [28] 6 2.3 Example Of Surface Flashover On A Pin Insulator [32] 8 2.4 An Example Of Polymer Insulator Available In The 9 2.5 Insulator Cross Section [42] 10 2.6 (a) Tracking Failure And (b) Erosion Failure [43] 12 2.7 Brittle Fracture Failure Of 115 KV Polymer Insulator [43] 13 2.8 In The Early Years Of The Metal Wedging Process, The 14 2.9 Dry Band Formation [44] 16 2.10 A Flashover Event On An Insulator [47] 17 2.11 (a) Salt [50] And (b) Icing Deposit On A Polymer 18 2.12 A Flashover Event On A Polymer Insulator [53] 19 2.13 A Close Look At The Lightning Discharge Channels [66] 23 2.14 The Average Number Of Thunderstorm Days In 24 2.15 Tracking Wheel Test Number 1 [57] 26 2.16 Rotating Wheel Dip Test [57] 27 2.17 The Controlled Environment Chamber (CEC) [60] 29 2.18 Aspergillus Nigger Growth On A Polymer Insulator [60] 30 2.19 A Lightning Impulse With A Wedge-Shaped Design [83] 33 2.20 A Full Lightning Impulse With A Steep-Front Time [83] 33 2.21 An Exponential Impulse Current With The Tail Crossing 34 3.1 Block Diagram Of The Study 40 3.2 Flow Chart Of The HFSS 3D Geometry Process 41 3.3 The HFSS Flow Chart Iterative Solution Process 42 3.4 The Six-Steps In HFSS Design 44 3.5 The 10 KV Polymer Insulator Modelling 44 3.6 The 6-Faces Of The Square Box As Radiation Boundaries 46 3.7 The Lightning Voltage Excitation Entering And Exiting 46 3.8 Lightning Voltage Wave Shape 47 3.9 Flow Chart Of The Maxwell 2D Geometry Process 48 3.10 The Four-Steps In The Maxwell Design [95] 49 3.11 The 10 kV Polymer Insulator 2D Modelling 49 3.12 The Four Edges Of The Rectangle Set As Balloon 50 3.13 The Steady State Voltage Setup 51 3.14 Three Months Into The Moss Growing Process 52 3.15 15 Months Into The Moss Growing Process 52 3.16 0.02 m X 0.02 m X 0.02 m Square Case 54 3.17 The Salt Fog Chamber With Six Fog Nozzles 54 3.18 The Fog Maker Placed On The Top Of The Chamber 55 3.19 Uniformly Wet Insulator Surface 55 3.20 TERCO Two-Stage Impulse Generator 57 3.21 The Experimental Setup For Dry, Foggy And Polluted 57 4.1 Summary Of Simulation Work In This Study 62 4.2 Clean Insulator 63 4.3 The Behaviour Of The Electric Field And Voltage Distribution

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4.4 The Behaviour Of The Electric Field And Voltage Distribution Of A Clean Insulator Under Weather With 70 % Humidity 64

4.5 The Behaviour Of The Electric Field And Voltage Distribution Of A Clean Insulator Under Foggy Weather Conditions 64

4.6 The Behaviour Of The Electric Field And Voltage Distribution Of A Clean Insulator Under Polluted Weather Conditions 65

4.7 Observation Points At Three Critical Locations 65 4.8 Polymer Insulator With Partial Moss On The Surface 67 4.9 The Behaviour Of The Electric Field And Voltage Distribution

Of An Insulator (Sample P) Under Dry Weather Conditions 68 4.10 The Behaviour Of The Electric Field And Voltage Distribution

Of An Insulator (Sample P) Under Weather With 70 % Humidity 68

4.11 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample P) Under Foggy Weather Conditions 69

4.12 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample P) Under Polluted Weather Conditions 69

4.13 Polymer Insulator With Partial Moss On The Surface 71 4.14 The Behaviour Of The Electric Field And Voltage Distribution

Of An Insulator (Sample Q) Under Dry Weather Conditions 72 4.15 The Behaviour Of The Electric Field And Voltage Distribution

Of An Insulator (Sample Q) Under Weather With 70 % Humidity 72

4.16 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample Q) Under Foggy Weather Conditions 73

4.17 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample Q) Under Polluted Weather Conditions 73

4.18 Polymer Insulator With Partial Moss On The Surface 75 4.19 The Behaviour Of The Electric Field And Voltage Distribution

Of An Insulator (Sample R) Under Dry Weather Conditions 76 4.20 The Behaviour Of The Electric Field And Voltage Distribution

Of An Insulator (Sample R) Under Weather With 70 % Humidity 76

4.21 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample R) Under Foggy Weather Conditions 77

4.22 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample R) Under Polluted Weather Conditions 77

4.23 The Behaviour Of The Electric Field And Voltage Distribution Of A Clean Insulator Under Dry Weather Conditions 79

4.24 The Behaviour Of The Electric Field And Voltage Distribution Of A Clean Insulator Under Weather With 70 % Humidity 80

4.25 The Behaviour Of The Electric Field And Voltage Distribution

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PMOf A Clean Insulator Under Foggy Weather Conditions 80

4.26 The Behaviour Of The Electric Field And Voltage Distribution Of A Clean Insulator Under Polluted Weather Conditions 81

4.27 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample P) Under Dry Weather Conditions 82

4.28 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample P) Under Weather With 70 % Humidity 83

4.29 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample P) Under Foggy Weather Conditions 83

4.30 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample P) Under Polluted Weather Conditions 84

4.31 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample Q) Under Dry Weather Conditions 85

4.32 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample Q) Under Weather With 70 % Humidity 86

4.33 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample Q) Under Foggy Weather Conditions 86

4.34 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample Q) Under Polluted Weather Conditions 87

4.35 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample R) Under Dry Weather Conditions 88

4.36 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample R) Under Weather With 70 % Humidity 89

4.37 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample R) Under Foggy Weather Conditions 89

4.38 The Behaviour Of The Electric Field And Voltage Distribution Of An Insulator (Sample R) Under Polluted Weather Conditions 90

4.39 Breakdown voltage for clean insulator under dry air 92 4.40 Breakdown voltage for clean insulator under foggy air 92 4.41 Breakdown voltage for clean insulator under polluted air 93 4.42 Breakdown voltage for contaminated insulator under dry air 94 4.43 Breakdown voltage for contaminated insulator under foggy air

95 4.44 Breakdown voltage for contaminated insulator under polluted

air 96 4.45 Measured voltage under steady state power frequency and

foggy air for contaminated insulator 101 4.46 Measured voltage under steady state power frequency and

polluted air for contaminated insulator 101 4.47 Surface discharge of contaminated insulator under foggy air

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4.48 Surface discharge of contaminated insulator under polluted air test 102

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PMLIST OF ABBREAVIATIONS

Description BIL Creepage distance SDD NSDD r

σ %RH E J LC SiR FEM

Basic Impulse Insulation Level Leakage Distance Salt Deposit Density Non-Soluble Material Deposit Density Relative Permittivity Bulk Conductivity Percentage of Relative Humidity Electric Field Current Density Leakage Current Silicone Rubber Finite Element Method

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INTRODUCTION

1.1 Research Overview

An insulator is an essential component in power transmission and distribution networks as it serves as a mechanical support for power lines. The outdoor insulators also act as front line protection by preventing any unwanted flow of current to earth via the supporting structure. However, this feature is dependent on the rate of environmental pollution deposited on the surface of an insulator, which tends to mask its performance. There are at least six known factors of environmental pollution, namely, temperature, UV radiation, altitude, rain, icing and pollution. Thus, this study has been tasked to seek enlightenment concerning the influence of environmental pollution on the electrical performance of an outdoor polymer insulator under a lightning impulse voltage.

Distribution insulators are widely used in Malaysia in 33 kV, 11 kV and 400/230 V distribution networks. Nonetheless, in certain parts of Johor and Perak, the distribution voltage may also include 22 kV and 6.6 kV [1],[2]. Currently, Tenaga Nasional Berhad (TNB), Malaysia’s largest electricity utility company and one of the largest in the region [3], operates and maintains 1245 km of 11 kV, 1156 km of 22 kV and 5285 km of 33 kV bare overhead lines [4],[5]. The insulators used in these medium and low voltage distribution networks in Malaysia are currently made of ceramic, glass and polymer [6],[7]. These outdoor insulators are employed on lines that pass through transverse areas of urban and rural parts and inescapably into a 20,456,000 ha of forest in the country, which inevitably subjects the insulators to environmental stresses and pollution stresses [8]-[14], adding to the existing stresses of the line in the form of electrical and mechanical stresses [11],[15]. These stresses can lead to the insulators suffering issues which can cause their performance to deteriorate [9],[11],[13]. Environmental stresses such as rain, ultraviolet radiation, temperature and humidity variations are rated as important contributing factors to this deterioration [11],[13]. Unfortunately, all of these elements are experienced in Malaysia. Malaysia is positioned near to the equator line at 1° to 7° North latitude and 100° to 120° East longitude [16] and is characterised by an equatorial climate. High temperatures that are likely be uniform throughout the year, high humidity, relatively moderate winds and abundant rainfall are all characteristics of this kind of climate. Malaysia has a low variation in temperature at typically 2 °C throughout the year with the range of a minimal average of 22 °C to 24 °C and a maximum average of 29 °C to 33 °C per month [16]. On the other hand, due

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to the equatorial location, the humidity is relatively high and lies between 70 to 90 %. A further effect of the geographical location and topographical nature of Malaysia results in seasonal monsoon winds and causes the level of solar radiation received to fluctuate as the clouds absorb the sunshine and reduce the insolation. The daily average of solar radiation in Malaysia comes to 4500 kWh/m2 [16]. With such harsh exposure and stresses upon the insulators, they will eventually age and the performance of these outdoor insulators will reduce. 1.2 Problem Statement/Motivation

The influence of bio-contamination on the electrical performance of a polymer insulator is an interesting topic that has been studied by many researchers, especially from countries with a tropical climate. Bio-contamination thrives well in this kind of climate. Malaysia has it all - high rainfall, high humidity, intensive sun radiation and elevated temperature which are especial conditions that make biological growth within the territory more probable. Consequently, it is important to consider the local bio-contamination issue when designing new power lines. A number of reports have surfaced from Uruguay, Tanzania, Sri Lanka, Germany, USA (Texas, Georgia, and Florida), Columbia, Japan and Sweden [17]-[21] concerning visible greenish, blackish and sometimes brownish spots on the surface of a polymer insulator, causing a drop in the withstand level of the wet and dry flashovers and an increase in the leakage current [18],[20],[22]. These spots have subsequently been identified as algae, lichen, moss, mould or fungal growth [17]-[20], which are biological-contamination-types typically found in a tropical environment with high rainfall, high humidity, intensive sun radiation and elevated temperature [17]-[18],[20]. When these bio-contaminates colonise the surface of the insulators, they will impeded the drying of the surface and there is a possibility of increasing the degradation of the insulators through deposit enzymes [18],[21]-[22]. The research gap among previous research refers to considering the abovementioned case under lightning conditions.

Many reports have cited the effects of these bio-contaminates, and yet researchers are still unclear as to how much the growth of these contaminates can affect the performance of polymer insulators under high humidity conditions, let alone under natural field conditions. Thus, it is necessary to perform thorough research and share the findings with the community of researchers. Malaysia has high rainfall, high humidity, intensive sun radiation and elevated temperature. All these conditions encourage biological growth within the

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territory. Further, the occurrence of lightning in Malaysia is among the highest levels recorded in the world [23]. Therefore, considering the effect of bio-contamination materials on the surface of a polymer insulator in terms of the electrical performance of the insulator under impulse lightning voltage conditions can be helpful to increase the stability level of the line. This research considers the case from both the experimental and simulation points of view and the results will be explained and discussed accordingly. 1.3 Objectives

The aim of this study is to evaluate the electrical performance of a 10 kV polymer insulator with moss deposited on the surface under lightning impulse conditions. The objectives are listed as follows:

1. To model and simulate polymer insulators with surface moss in both steady state and lightning condition under various air conditions.

2. To investigate the electric field behaviour and voltage distribution of the abovementioned insulators.

3. To examine the electrical breakdown and measured the leakage current the abovementioned insulator under positive lightning impulse voltage and various air conditions.

1.4 Scope Of Work/Limitations

The scope and limitations of this study are listed as follows:

1. A 10 kV polymer insulator was studied.

2. A lightning impulse voltage was used in studying the electrical performance of the abovementioned insulator under lightning conditions.

3. Surface moss was generated (moss deposition on the insulator surface) under natural conditions.

4. Parameter for moss has been obtained from experimental works.

5. A limitation in modelling an edge rounded structure of the polymer shed and surface moss in HFSS and Maxwell software interface resulting in different values of tetrahedral mesh for each drawing and therefore influenced the outcome results.

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1.5 Thesis Layout

The layout of the written thesis is as follows:

1. Chapter 1 – Introduction

This chapter briefly discusses insulators, lightning and the associated environmental pollution that led to the motivation to take up research in terms of studying polymer insulator performance including deposited moss under lightning conditions. The summary of the research includes the objectives and limitations.

2. Chapter 2 – Literature Review

This chapter reviews past research that has significant connection to this study. The associated research literature concerns the classification of insulators, the physics of lightning and its standards as well as the effects of environmental factors on the performance of polymer insulators.

3. Chapter 3 – Methodology

Chapter 3 touches on the methodology of the experimental and simulation works in achieving the ultimate objective of this study, namely the electrical performance of a 10 kV polymer insulator under lightning conditions with moss deposition on the insulator surface.

4. Chapter 4 – Results And Discussion

In this chapter, the experimental and simulation results corresponding to the objectives of this study are presented and discussed accordingly.

5. Chapter 5 - Conclusion

In this final chapter, a summary of the results is expressed and the relevance to the application side is presented. Moreover, recommendations and potential future works are proposed.

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REFERENCES [1] Tenaga Nasional Berhad (TNB) 2015. TNB Electrical System. Malaysia:

TNB [2] Wikipedia, The Free Encyclopedia. (2015). National Grid (Malaysia).

Retrieved on December 21, 2015, from https://en.wikipedia.org/wiki/National_Grid_(Malaysia)

[3] Tenaga Nasional Berhad (TNB) 2015. Corporate Profile. Malaysia: TNB [4] Ariffin, M.F. et al. (2011). Managing Transient Interruptions on Aged 22kV

Overhead Lines in TNB Distribution Network Through Engineering Practices Assessment and Insulation Coordination Guidelines, 21st International Conference on Electricity Distribution. Frankfurt: CIRED.

[5] Ariffin, M.F. (2013). Use of Combined Approaches towards Mitigating Faults Caused by Lightning on TNB Distribution Overhead Lines, 22nd International Conference on Electricity Distribution. Stockholm: CIRED.

[6] Samsudin, M.R. et al. (2010). Development of the assessment procedure to evaluate the performance of High Voltage Insulator Coating (HVIC) Modern Electric Power Systems (MEPS), 2010 Proceedings of the International Symposium. Wroclaw: IEEE.pp.1-6.

[7] Othman, N.A. et al. (2014). Measurement of Surface Charge Distribution on Glass Insulator using Steel Mesh. 2014 IEEE International Conference Power & Energy (PECON). Kuching, Malaysia: IEEE.pp.105-108.

[8] Manjang, S. et al. (2011). Characteristics of High Voltage Polymer Insulator under Accelerated Artificial Tropical Climate Multi Stress Aging. Conference Proceedings of ISEIM2011. Kyoto, Japan: IEEE. pp. 221-224.

[9] Meyer, L.H. et al. Study of the Performance of 25kV Insulators under Various Weather Conditions. “Unpublished”.

[10] Joneidi, I.A. et al. (2013). Electric Field Distribution under Water Droplet and Effect of Thickness and Conductivity of Pollution Layer on Polymer Insulators using Finite Element Method. International Journal of Computer and Electrical Engineering, vol.5(2),pp.266-270.

[11] Harid, N. et al. (2014). Flashover Characteristics of Polluted Silicone Rubber Insulators Exposed to Artificial UV Irradiation. 2014 Electrical Insulation Conference. Pennsylvania. pp.440-444.

[12] Krzma, A.S.(2014). Comparative Performance of 11kV Silicone Rubber Polymeric Insulators under Rotating Wheel Dip Test. “Unpublished”.

[13] Xu,G. et al. (1996). Accelerated Environmental and Electrical Aging of Polymer Insulators. IEEE Annual Report – Conference on Electrical Insulation and Dielectric Phenomena. pp.404-407.

[14] Venkatesulu , B. & Thomas, M. J. (2011). Long-term Accelerated Weathering of Outdoor Silicone Rubber Insulators. IEEE Manuscript. Bangalore, India : IEEE. pp. 418-424.

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