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  • 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.

    i

  • 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.

    ii

  • 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.

    iii

  • 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

    iv

  • 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

    v

  • 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