UNIVERSITI PUTRA MALAYSIA

VANESSA CAROLINA LAVERDE MILEO

FK 2012 38

BREAKDOWN PERFORMANCE OF BACKFILL MATERIALS UNDER IMPULSE AND AC VOLTAGE CONDITIONS

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BREAKDOWN PERFORMANCE OF BACKFILL MATERIALS UNDER IMPULSE AND AC VOLTAGE CONDITIONS

By

VANESSA CAROLINA LAVERDE MILEO

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

Master of Science

July 2012

 

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DEDICATIONS

To my Lord

To my mother, a combatant lady and my example of life and professionalism

To my supervisors, Assoc. Prof. Dr. Mohd Zainal Abidin Ab Kadir and Dr.

Chandima Gomes for your continued support and dedication.

And lastly to my love, who supported me in all my decisions.

 

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Abstract of thesis presented to the Senate of University Putra Malaysia in fulfilment of the requirement for the degree of Master of Science

ABSTRACT

BREAKDOWN PERFORMANCE OF BACKFILL MATERIALS UNDER IMPULSE AND AC VOLTAGE CONDITIONS

By

VANESSA CAROLINA LAVERDE MILEO

July 2012

Chairman: Mohd Zainal Abidin Ab Kadir, PhD

Faculty: Engineering

Earthing means the connection of equipment through a conductor to ground. The soil

is composed by many materials, which can be good or poor conductors of electricity.

The earth as a whole is considered as a good conductor of electricity. Many electrical

systems are prone to the risk of failure as a result of lightning strikes. It requires

special arrangements to reduce the risk involved. A proper ground system is

fundamental to this regulation. Lightning impulse has a steep upslope and is source

of high frequency current. Special ground systems designs are needed and it is called

impulse earthing. Nowadays, most engineers use backfill materials to reduce the

ground resistance to low values. Backfill materials or additive fillers are used to refill

the space in the vicinity of the electrode. They provide a low ground resistance value.

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The different models which are available such as Liew and Darveniza, Cooray and

colleagues, etc., with the aim to take into account the nonlinear effects due to soil

ionization, will be mentioned in this research. Basically, they can be classified as the

variable geometry approach and the variable soil conductivity approach. This non-

linear behavior is due to the effects of two conduction processes: thermal and soil

ionizations. In the thermal process, the temperature of soil increases through the low-

energy absorption produced by the resistive heating. The soil ionization will increase

the soil conductivity and reduce its resistivity, causing the resistance of the soil to

decrease with increasing current.

This research focuses on the behaviour of dry sand, bentonite and cement under

impulse and AC voltage conditions. The selections of materials were based on the

availability and anticipation of the past research. There are many factors that could

influence the experimental results such as weather, moist of the material, material

availability, etc. The experiments were carried out at the TNB Research High

Voltage Laboratory.

For impulse and AC testings, bentonite breakdown in early stages, unlike cement and

air gap (impulse testing) and sand (AC conditions). During the alternative voltage

testings for sand and bentonite, dust puffing out from the container and fulgurite

formations were observed, this peculiarity is due to high temperatures in the backfill

materials during soil ionization.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains

PRESTASI KEROSAKAN BAHAN SENDATAN DI BAWAH KEADAAN DEDENYUT DAN VOLTAN AC

Oleh

VANESSA CAROLINA LAVERDE MILEO

Julai 2012

Pengerusi: Mohd Zainal Abidin Ab Kadir, PhD

Fakulti: Kejuruteraan

Pembumian bererti sambungan peralatan melalui konduktor ke tanah. Tanah terdiri

daripada banyak bahan-bahan yang boleh menjadi pengalir elektrik yang baik atau

lemah. Bumi secara keseluruhannya dianggap sebagai satu konduktor elektrik yang

baik. Banyak sistem elektrik terdedah kepada risiko kegagalan akibat daripada

panahan kilat. Ia memerlukan perkiraan khas untuk mengurangkan risiko yang

terlibat. Sistem pembumian yang betul adalah asas kepada peraturan ini. Dedenyut

kilat mempunyai lereng atas yang curam dan sumber arus frekuensi tinggi. Reka

bentuk sistem pembumian khas adalah diperlukan dan ia dipanggil pembumian

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dedenyut. Kini, kebanyakan jurutera menggunakan bahan sendatan untuk

mengurangkan rintangan tanah kepada nilai yang rendah.

Model yang berbeza yang ada seperti Liew and Darveniza, Cooray dan rakan-rakan

dan lain-lain, dengan tujuan untuk mengambil kira kesan tak linear yang disebabkan

oleh pengionan tanah, akan disebut dalam kajian ini. Pada asasnya, ia boleh

dikelaskan sebagai pendekatan geometri berubah dan pendekatan kekonduksian

tanah berubah. Tingkah laku bukan linear ini adalah disebabkan oleh kesan dua

proses konduksi: pengionan termal dan tanah. Dalam proses haba, suhu meningkat

tanah melalui penyerapan tenaga rendah yang dihasilkan oleh pemanasan rintangan.

Pengionan tanah akan meningkatkan kekonduksian tanah dan mengurangkan

kerintangan, menyebabkan rintangan tanah untuk mengurangkan dengan semasa

yang semakin meningkat.

Kajian ini memberi tumpuan kepada sifat pasir kering, bentonit dan simen di bawah

keadaan voltan yang berbeza. Pemilihan bahan berdasarkan ketersediaan dan

jangkaan penyelidikan yang lepas. Terdapat banyak faktor yang boleh

mempengaruhi keputusan eksperimen seperti cuaca, kelembapan bahan dan

ketersediaan baha. Kajian ini telah dijalankan di Makmal Voltan Tinggi milik TNB

Research. Bagi ujian dedenyut dan AC, bentonit rosak pada peringkat awal, tidak

seperti simen dan ruang udara (ujian dedenyut) dan pasir (ujian AC). Semasa ujian

voltan AC bagi pasir dan bentonit, habuk keluar dari bekas dan pembentukan

fulgurite telah diperhatikan. Keanehan ini adalah kerana suhu yang tinggi dalam

bahan sendatan semasa pengionan tanah.

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ACKNOWLEDGEMENTS

To my supervisors, Assoc. Prof. Dr. Mohd Zainal Abidin Ab Kadir and Assoc. Prof.

Dr. Chandima Gomes for your continued support and dedication.

To my beloved team Muhammad Noh Bin Hamzah and Halimatusaadiah Binti Rusli

for your support in the laboratory work.

Lastly, to the TNBR Research Team for your kind collaboration.

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I certify than an Examination Committee has met on 09 July 2012 to conduct the final examination of Vanessa Carolina Laverde Mileo on her thesis entitled “Breakdown performance of backfill materials under impulse and ac voltage conditions” in accordance with the Universities and University College Act 1971 and the Constitution of the University Putra Malaysia [P.U.(A) 106] 15 March 1998. The committee recommends that the student be awarded the Master of Science. Members of the Examination Committee were as follows:

Norman Mariun, PhD Ir. Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Hashim Hizam, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Noor Izzri Abdul Wahab, PhD Lecturer Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Muhammad Ramlee Kamarudin, PhD Associate Professor Wireless Communication Centre (WCC) Universiti Teknologi Malaysia (External Examiner)

SEOW HENG FONG, PhD Professor and Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date:

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This 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: Mohd Zainal Abidin Ab Kadir, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Chandima Gomes, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Member)

BUJANG BIN KIM HUAT, PhD Professor and Dean School of Graduated Studies Universiti Putra Malaysia Date:

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DECLARATION

I declare that the thesis is my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously, and is not concurrently, submitted for any other degree at Universiti Putra Malaysia or at any other institution.

VANESSA CAROLINA LAVERDE MILEO

Date: 09th July 2012

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TABLE OF CONTENTS

Page

DEDICATIONS ii ABSTRACT iii ABSTRAK v ACKNOWLEDGEMENTS vii APPROVAL Error! Bookmark not defined.viii DECLARATION x TABLE OF CONTENTS xi LIST OF TABLES xiii LIST OF FIGURES xiv CHAPTER

1 INTRODUCTION 1 1.1 Overview 1 1.2 Problem Statement 3 1.3 Research objectives 7 1.4 Scope and Limitations 7 1.5 Thesis Structure 8

2 LITERATURE REVIEW 10 2.0 Introduction 10 2.1 Soil 11 2.2 Types of soil 12 2.3 Soil Moisture 13 2.4 Soil temperature 14 2.5 Grain size and distribution of soil 15 2.6 Soil Ionization 16

2.6.1 Liew and Darveniza Model 17 2.6.2 Model of Cooray and colleagues 23

2.7 Breakdown in solids 25 2.7.1 Treeing 25

2.8 Impulse and switching voltage generation 27 2.8.1 Lightning impulse voltages 28 2.8.2 Switching impulses voltages 28 2.8.3 Impulse generator configuration 29 2.8.4 Multistage Impulse Generator 32

2.9 Up and down test method 33 2.10 High Voltage AC generation 34 2.11 Additive fillers or Backfill Materials 35

2.11.1 Acceptable Low Resistivity Materials 39 2.11.2 Unacceptable Backfill Materials 40

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3 RESEARCH METHODOLOGY 43 3.1 Introduction 43 3.2 Research Methods 43 3.3 Laboratory arrangement and testing parameters 44 3.4 Impulse testing 45 3.5 High voltage AC (HVAC) testing 47 3.6 Measurement systems 48

3.6.1 Voltage divider 50 3.6.2 Rogowski coil 52 3.6.3 Oscilloscope 54

3.7 Container and copper rod 55

4 RESULT AND DISCUSSION 58 4.1 Introduction 58 4.2 Impulse voltage result 59

4.2.1 Air Gap 59 4.2.2 Cement 63 4.2.3 Bentonite 67

4.3 Impulse voltage comparison result 71 4.4 AC Results 74

4.4.1 Sand 74 4.4.2 Cement 76 4.4.3 Bentonite 77

4.5 Summary 79

5 CONCLUSION AND RECOMMENDATION 82 5.1 Conclusion 82 5.2 Contribution 83 5.3 Recommendation for Future Research 84

REFERENCES 85 APPENDIX A 90 APPENDIX B 101 APPENDIX C 112

BIODATA OF STUDENT 123 LIST OF PUBLICATIONS 124

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