full thesis pd

NOISE REDUCTION AND SOURCE RECOGNITION OF

PARTIAL DISCHARGE SIGNALS IN GAS-INSULATED

SUBSTATION

JIN JUN

NATIONAL UNIVERSITY OF SINGAPORE

2005

NOISE REDUCTION AND SOURCE RECOGNITION OF

PARTIAL DISCHARGE SIGNALS IN GAS-INSULATED

SUBSTATION

JIN JUN

( B. ENG )

A THESIS SUBMITTED

FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING

NATIONAL UNIVERSITY OF SINGAPORE

2005

ACKNOWLEDGEMENT

It is in great appreciation that I would like to thank my supervisor, Associate Professor

Chang Che Sau, for his invaluable guidance, encouragement, and advice in every

phase of this thesis. It would have been an insurmountable task in completing the work

without him.

I would like to extend my appreciation to Dr. Charles ChangDr. Toshihiro Hoshino

and Dr. Viswanathan Kanakasabai for their valuable advice on this research project.

Acknowledgement is also towards to Toshiba Corporation, Japan for its support on this

project.

I would like to thank my wife and my parents for their love, patience, and continuous

support along the way.

Thanks are also given to the Power System Laboratory Technician Mr. H. S. Seow, for

his help and cooperation throughout this research project.

Last but not least, I would like to thank my friends and all those, who have helped me

in one way or another.

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PAPERS WRITTEN ARISING FROM WORK IN THIS THESIS

1. C.S. Chang, J. Jin, C. Chang, Toshihiro Hoshino, Masahiro Hanai, Nobumitsu

Kobayashi, Separation of Corona Using Wavelet Packet Transform and Neural

Network for Detection of Partial Discharge in Gas-insulated Substations, IEEE

Trans. Power Delivery, vol. 20, no. 2, pp. 1363 1369, April 2005..

2. C.S. Chang, J. Jin, S. Kumar, Qi Su, Toshihiro Hoshino, Masahiro Hanai,

Nobumitsu Kobayashi, Denoisng of Partial Discharge Signals in Wavelet Packets

Domain, IEE Proc. Science, Measurement and Technology, vol. 152, no. 3, pp.

129-140, May 2005.

3. C.S. Chang, J. Jin, C. Chang, Online Source Recognition of Partial Discharge for

Gas Insulated Substations Using Independent Component Analysis, accepted and

will appear in IEEE Transactions on Dielectrics and Electrical Insulation, Sep.

2005.

4. J. Jin, CS. Chang, C. Chang, T. Hoshino, M. Hanai and N. Kobayashi,

Classification of Partial Discharge for Gas Insulated Substations Using Wavelet

Packet Transform and Neural Network, accepted and will appear in IEE Science

Measurement and Technology, Nov. 2005.

5. C.S. Chang, J. Jin, Toshihiro Hoshino, Masahiro Hanai, Nobumitsu Kobayashi,

De-noising of Partial Discharge Signals for Condition Monitoring of GIS, Proc.

of International Power Quality Conference 2002, Singapore, vol. 1, pp 170-177.

6. C.S. Chang, J. Jin, C. Chang, Toshihiro Hoshino, Masahiro Hanai, Nobumitsu

Kobayashi, Optimal Selection of Parameters for Wavelet-Packet-Based Denoising

of UHF Partial Discharge Signals, Proc. of Australasian Universities Power

Engineering Conference 2004, paper number 38, Australia.

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7. C.S. Chang, R.C. Zhou, J. Jin, Identification of Partial Discharge Sources in Gas-

Insulated Substations, Proc. of Australasian Universities Power Engineering

Conference 2004, paper number 50, Australia.

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TABLE OF CONTENT

ACKNOWLEDGEMENT.............................................................................................i

PAPERS WRITTEN ARISING FROM WORK IN THIS THESIS.......................iii

TABLE OF CONTENT...............................................................................................iv

SUMMARY ................................................................................................................ix

LIST OF FIGURES .....................................................................................................xi

LIST OF TABLES .....................................................................................................xvi

CHAPTER 1: INTRODUCTION................................................................................1

1.1 BACKGROUND OF THE RESEARCH................................................2

1.1.1 Introduction to Gas-insulated Substation ..............................................3

1.1.2 Condition Monitoring of Gas-insulated Substation ...............................5

1.1.3 PD in SF6.................................................................................................6

1.1.4 PD Measurement in Gas-insulated Substation .....................................10

1.1.5 Overview of the UHF PD Monitoring System for GIS..........................14

1.1.6 The Necessity of Noise Reduction and Discrimination .........................16

1.1.7 The Necessity of PD Source Recognition..............................................18 1.2 REVIEW OF NOISE REDUCTION AND DISCRIMINATION ........20

1.2.1 Removal of White Noise ........................................................................20

1.2.2 Discrimiantion of Corona Interference.................................................24

1.3 REVIEW OF PARTIAL DISCHARGE SOURCE RECOGNITION ..26

1.4 OBJECTIVES AND CONTRIBUTIONS OF THE THESIS ...............29

1.4.1 Objectives of the Project .......................................................................29

1.4.2 Author's Main Contributions.................................................................32

1.5 OUTLINE OF THE THESIS ................................................................32

CHAPTER 2: DENOIZING OF PD SIGNALS IN WAVELET PACKET

DOMAIN..............................................................................................36

2.1 INTRODUCTION.................................................................................37

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2.2 WAVELET PACKET TRANSFORM AND THE GENERAL

WAVELET-PACKET-BASED DENOIZING METHOD ...................40

2.2.1 Introduction to Wavelet Packet Transform ...........................................40

2.2.2 Introduction to the General DenoizingMethod .....................................43

2.2.3 Shortcomings of the General Method....................................................44

2.3 A NEW WAVELET-PACKET-BASED DENOIZING SCHEME FOR

UHF PD SIGNALS...............................................................................45

2.3.1 Introduction...........................................................................................45

2.3.2 Parameters Setting for Denoizing .........................................................46

2.3.3 Denoizing of PD Signals .......................................................................61

2.4 RESULTS AND DISCUSSIONS .........................................................64

2.4.1 Wavelet and Decomposition Level Selection .......................................65

2.4.2 Best Tree Selection ................................................................................68

2.4.3 Thresholding Parameters Selection ......................................................72

2.4.4 Performance on PD Signal Measured without Noise Control in

Laboratory ............................................................................................74

2.5 CONCLUDING REMARKS ................................................................75

CHAPTER 3: OPTIMAL SELECTION OF PARAMETERS FOR WAVELET-

PACKET-BASED DENOIZING .......................................................76

3.1 INTRODUCTION.................................................................................77

3.2 DESCRIPTION OF THE PROBLEM ..................................................78

3.3 DENOIZING PERFORMANCE MEASURE AND FITNESS

FUNCTION...........................................................................................79

3.4 PARAMETER OPTIMIZATION BY GA............................................82

3.4.1 Brief Review of GA................................................................................82

3.4.2 GA Optimization....................................................................................83

3.4.3 Selection of Control Parameters for GA ...............................................84

3.5 PERFORMANCE TESTING................................................................90

3.6 RESULTS AND DISCUSSIONS .........................................................91

3.7 CONCLUDING REMARKS ................................................................95

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CHAPTER 4: PD FEATURE EXTRACTION BY INDEPENDENT

COMPONENT ANALYSIS ...............................................................96

4.1 INTRODUCTION ................................................................................97

4.2 PRE-SELECTION ..............................................................................101

4.3 REVIEW OF INDEPENDENT COMPONENT ANALYSIS ...........103

4.3.1 Comparison of PCA and ICA ..............................................................103

4.3.2 Introduction to ICA .............................................................................104

4.4 FEATURE EXTRACTION BY ICA..................................................108

4.4.1 Identification of Most Dominating Independent Components ............108

4.4.2 Construction of ICA-based