THE EFFECT OF THERMAL AGEING ON LOW VOLTAGE CROSS-LINKED POLYETHYLENE INSULATED CABLE NOOR FAEZAH BINTI HAMDI A project report submitted in partial fulfilment of the requirements for the award of the degree of Master of Forensic Engineering. School of Civil Engineering Faculty of Engineering Universiti Teknologi Malaysia JANUARY 2019
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THE EFFECT OF THERMAL AGEING ON LOW VOLTAGE CROSS-LINKED
POLYETHYLENE INSULATED CABLE
NOOR FAEZAH BINTI HAMDI
A project report submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Forensic Engineering.
School of Civil Engineering
Faculty of Engineering
Universiti Teknologi Malaysia
JANUARY 2019
iii
DEDICATION
This thesis is dedicated to my parents
for their love , endless support
and encouragement.
iv
ACKNOWLEDGEMENT
"In The Name Of Allah, The Most Beneficient,The Most Merciful"
I would first like to thank my main supervisor, Dr. Mohd Azreen bin Mohd
Ariffin for his continuous support, motivation and encouragement. I am forever
grateful for his kind advice and guidance in helping me for the completion of this
thesis.
My research would have been impossible without the aid and support of Ir.
Dr. Lau Kwan Yiew from School of Electical Engineering. His guidance and
immerse knowledge helped me in all the time of research experiment.
My sincere thanks also goes to the Jabatan Perkhidmatan Awam for the study
opportunity and providing the financial support for me to further my studies at the
Universiti Teknologi Malaysia, Johor. Not to forget, my current employer, Jabatan
Kerja Raya Malaysia for the opportunities and providing me the access, data and
sample for the this research. Financial assistance from the Universiti Teknologi
Malaysia for my research work is highly appreciated.
Finally, to my families and friends, thanks you for being there with your
unconditional love and continuous support.
v
ABSTRACT
This research presents some results and discusses the investigation on thermal
ageing of low voltage cross-linked polyethylene (XLPE) insulated cable rated at
0.6/1(1.2) kV. This type of cable was found to experience premature degradation
within three to five years of service. The objective of this investigation is to study the
characteristic of XLPE insulated cable under thermal conditions. A number of tests
were conducted to investigate the chemical properties, electrical properties and
mechanical properties of unaged and aged XLPE insulated cable. Samples were
thermally aged using air ventilated oven at temperature of 90 oC. The breakdown
strength of XLPE materials were measured for each samples. The structural changes
due to the formation of carbonyl groups were observed using Fourier Transform
Infrared (FTIR) spectroscopy. The application of Differential Scanning Calorimetry
(DSC) revealed the effect of thermal ageing on the crystallinity variation on XLPE
insulated cable. Mechanical properties were observed through tensile strength test.
Experimental findings in this study suggests that thermal ageing induces significant
degradation on XLPE insulated cable.
vi
ABSTRAK
Kajian ini menerangkan hasil siasatan dan ujian terhadap kabel voltan rendah
jenis cross-linked polyethylene (XLPE) dengan kadaran penebat pada 0.6 / 1 (1.2)
kilo volts. Kabel jenis ini didapati semakin kerap mengalami kerosakan akibat
pereputan awal dalam tempoh operasi antara tiga hingga lima tahun. Objektif
siasatan ini adalah untuk mengkaji ciri-ciri kabel jenis XLPE apabila diletakkan
dalam keadaan berhaba tinggi. Beberapa siri ujian telah dibuat untuk mengkaji sifat
kimia, elektrikal dan mekanikal kabel jenis XLPE dalam keadaan baru dan lama.
Kabel dipanaskan pada suhu 90 OC di dalam ketuhar sebagai kaedah penghasilan
kabel lama / tua. Kekuatan dielektrik untuk setiap sampel XLPE diukur. Perubahan
struktur bahan akibat pembentukan kumpulan karbonil turut diteliti menggunakan
teknik spektroskopi Fourier Transform Infrared (FTIR). Penggunaan teknik
Differential Scanning Calorimetry (DSC) membolehkan kesan penuaan haba
terhadap perubahan pada penghabluran bahan XLPE. Ciri mekanikal bahan diuji
melalui ujian kekuatan tegangan bahan. Hasil dari kajian ini mendapati bahawa
kesan penuaan haba telah menyebabkan kemerosotan jangka hayat kabel jenis voltan
rendah XLPE.
vii
TABLE OF CONTENTS
TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF ABBREVIATIONS xiii
LIST OF SYMBOLS xiv
LIST OF APPENDICES xv
CHAPTER 1 INTRODUCTION 1
1.1 Problem Background 6
1.2 Problem Statement 6
1.3 Research Objectives 7
1.4 Research Scope 7
1.5 Significance of the Study 5
CHAPTER 2 LITERATURE REVIEW 7
2.1 Introduction 7
viii
2.2 Characteristics of XLPE Material 9
2.3 Thermal Ageing of the XLPE Material 9
2.4 Oxidation in XLPE Insulation 11
2.5 Electrical Properties of XLPE Insulation 12
2.6 Mechanical Properties of XLPE Insulation 13
2.7 Crystallinity of XLPE Insulation 13
CHAPTER 3 RESEARCH METHODOLOGY 15
3.1 Overview of Research Design 15
3.2 Materials and Preparation 16
3.2.1 Materials 16
3.2.2 Preparation of Materials 19
3.2.3 Thermal Ageing Procedure 19
3.3 Experimental Techniques 20
3.3.1 Breakdown Strength Test 20
3.3.2 Fourier Transform Infrared Spectroscopy 23
3.3.3 Tensile Strength Test 24
3.3.4 Differential Scanning Calorimetry 26
CHAPTER 4 RESULT 29
4.1 Breakdown Strength Test 29
4.2 Fourier Transform Infrared Spectroscopy 33
4.3 Tensile Strength Test 37
4.4 Differential Scanning Calorimetry 42
ix
CHAPTER 5 DISCUSSION AND CONCLUSION 45
5.1 Discussion of the Results 45
5.1.1 Breakdown Strength Test 45
5.1.2 Fourier Transform Infrared Spectroscopy 46
5.1.3 Tensile Strength Test 51
5.1.4 Differential Scanning Calorimetry 52
5.2 Conclusion 54
REFERENCES 57
APPENDICES 61
x
LIST OF TABLES
TABLE NO. TITLE PAGE
Table 4.1 Breakdown strength data of cable A and cable C. 23
Table 4.2 Breakdown strength data of cable B and cable C. 24
Table 5.1 Carbonyl compound group frequencies 42
Table 5.2 Functional group found in XLPE Fresh A1 43
Table 5.3 Functional group found in XLPE Fresh B1 44
Table 5.4 Functional group found in XLPE Aged A2 45
Table 5.5 Functional group found in XLPE Aged B2 46
Table 5.6 Functional group found in XLPE Degraded 47
Table 5.7 Crystallinity variation from DSC measurement
(cooling) for XLPE material of cable A and cable C.
51
Table 5.8 Crystallinity variation from DSC measurement
(cooling) for XLPE material of cable B and cable C.
51
xi
LIST OF FIGURES
FIGURE NO. TITLE PAGE
Figure 1.1 A single core low voltage XLPE insulated cable. 2
Figure 1.2 A multi-core low voltage XLPE insulated cable. 3
Figure 1.3 Degraded red core XLPE cable found in switchboard. 4