Faculty of Electrical Engineering IMPACT OF DISTRIBUTED GENERATION ON POWER SYSTEM PROTECTION Dawood Saleem Ahmed Master of Electrical Engineering (Industrial Power) 2016 brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Universiti Teknikal Malaysia Melaka (UTeM) Repository
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Faculty of Electrical Engineering
IMPACT OF DISTRIBUTED GENERATION ON POWER SYSTEM
PROTECTION
Dawood Saleem Ahmed
Master of Electrical Engineering (Industrial Power)
2016
brought to you by COREView metadata, citation and similar papers at core.ac.uk
provided by Universiti Teknikal Malaysia Melaka (UTeM) Repository
This dissertation work is dedicated to my wife, and my big family; you are good examples
and you have taught me to work hard for the things that I aspire to achieve.
i
ABSTRACT
This dissertation describes a simulation study of the impact of distributed generation (DG) interconnection to an existing distribution system of an Iraq system. The increase load demand in many countries pushes the electrical company to use DG technology to meet their load. From the literature review, it was found in spite of many positive effects of DG such as reduce the power losses and reduce voltage drop; the parallel operation of DG with an existing distribution system has many technical problems. One of the most significant issues of parallel operation is the change of fault level and suitability of existing protection system that indeed needs to be maintained within acceptable limits as defined in the international standards. Therefore, this dissertation is performed to investigate the impact of DG based synchronous generator driven by diesel engine on both the fault level and protection system. A small part of the distribution system in Baghdad capital-Iraq which the DG is currently interconnected at 11kV bus has been chosen and modeled using DIgSILENT PowerFactory version 15. The impacts of DG installation at three different locations, i.e. two possible locations which are 33kV and 132kV buses as well as the actual location have been investigated. The dissertation basically includes two investigations which are; examine the change in the fault level without the presence of DG and with DG interconnection at three interconnection locations by executing three-phase fault at each bus of the network as well as investigate the suitability of protection devices through performing single-line-to-ground and three-phase faults at 33kV and 11kV feeders within the distribution system. The results show that after an extensive simulation study, the increase in short circuit level is noticeable at the buses where the DG is interconnected and the protection performance of unidirectional overcurrent relay suffer from blinding and sympathetic tripping as well as the under reach of distance relay, therefore, a series remedy is needed for safety purposes and to reliability of the system.
ii
ABSTRAK
Disertasi ini menerangkan tentang kajian simulasi kesan sambungan Penjana Teragih (PT) kepada system pengagihan yang sedia ada dalam sistem Iraq. Peningkatan permintaan beban di banyak negara memaksa syarikat elektrik menggunakan teknologi PT untuk memenuhi beban mereka. Daripada kajian literatur, didapati walaupun banyak kesan positif PT seperti mengurangkan kehilangan kuasa dan mengurangkan kejatuhan voltan operasi selari PT dengan sistem pengagihan yang sedia ada mempunyai banyak masalah teknikal. Salah satu isu yang paling penting ialah perubahan aras kerosakan dan kesesuaian sistem perlindungan sedia ada yang sememangnya perlu dikekalkan dalam had yang boleh diterima seperti yang ditakrifkan dalam piawaian antarabangsa. Oleh itu, kajian ini dijalankan untuk menyiasat kesan penjana segerak PT berasaskan enjin diesel terhadap aras kerosakan dan sistem perlindungan. Sebahagian kecil daripada sistem pengagihan di Bandar Baghdad, Iraq yang mana PT disambungkan di bas 11kV telah dipilih dan dimodelkan menggunakan DIgSILENT PowerFactory Versi 15. Kesan pemasangan DG di tiga lokasi berbeza iaitu dua lokasi kemungkinan, di bas 33kV dan 132 kV serta lokasi sebenar telah disiasat. Disertasi pada dasarnya menyentuh dua kes utama iaitu; memeriksa perubahan dalam aras kerosakan tanpa kehadiran PT dan dengan sambungan DG di tiga lokasi sambungan melalui pelaksanaan kerosakan tiga fasa pada setiap bas rangkaian serta menyiasat kesesuaian peranti perlindungan dengan melakukan kerosakan talian tunggal ke bumi dan kerosakan tiga fasa pada penyuap 33 kV dan 11kV dalam sistem pengagihan. Keputusan kajian simulasi menunjukkan peningkatan yang banyak pada aras litar pintas adalah ketara pada bas disambungkan dengan PT dan prestasi perlindungan bagi geganti arus lebih satu arah mengalami masalah terpelantik kabur dan simpatetik serta di bawah jangkauan geganti jarak. Oleh itu, penyelesaian yang serius diperlukan untuk tujuan keselamatan dan untuk meningkatkan kebolehpercayaan sistem.
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ACKNOWLEDGMENT
First my praise is to the Almighty “Allah”, on whom we ultimately depend. Then, I would
like to sincerely thank my supervisor Dr. Hidayat Bin Zainuddin and my Co-supervisor Dr.
Mohd Hendra Bin Hairi for their guidance, advice, and support.
This research would not be possible without financial support from the ministry of
electricity Iraq.
I am greatly indebted to all the teaching staff for their helpful recommendation, supports,
and giving infinite during my study in UTeM.
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TABLE OF CONTENTS
PAGE
DECLARATION ................................................................................................................. APPROVAL ......................................................................................................................... DEDICATION ..................................................................................................................... ABSTRACT ........................................................................................................................ i ABSTRAK .......................................................................................................................... ii ACKNOWLEDGMENT .................................................................................................. iii TABLE OF CONTENTS ................................................................................................. iv LIST OF TABLES ............................................................................................................ vi LIST OF FIGURES ........................................................................................................ viii
LIST OF APPENDICES ................................................................................................. xii LIST OF ABBREVIATIONS ........................................................................................ xiii LIST OF SYMBOLS ....................................................................................................... xv
1.1 Background ........................................................................................................... 1 1.2 Motivation for Research ....................................................................................... 3 1.3 Problem Statement ................................................................................................ 4 1.4 Objective of Research ........................................................................................... 4
1.5 Scope of Research ................................................................................................. 5 1.6 Contribution of Research ...................................................................................... 5 1.7 Organization of Dissertation ................................................................................. 6
2.3.4 Micro Turbines 15 2.3.5 Induction and Synchronous Generators 16
2.4 Islanding of a Power Network ............................................................................ 19 2.5 Interconnection Protection .................................................................................. 22 2.6 Impact of Distributed Generation on Power System Grid .................................. 25
2.6.1 Impact of DG on Voltage Regulation 26 2.6.2 Impact of DG on System Losses 27
2.6.3 Impact of DG on Short Circuit Level 27 2.6.4 Impact of DG on Distribution System Protection 30
2.6.4.1 Coordination Protection Problem 31
2.6.4.2 Sympathetic Tripping 34 2.6.4.3 Blinding of protection 35
3. RESEARCH METHODOLOGY .............................................................................. 39 3.1 Introduction ......................................................................................................... 39 3.2 Power Flow Study ............................................................................................... 40 3.3 Radial Line Fault Current Calculation ................................................................ 44 3.4 DIgSILENT PowerFactory ................................................................................. 54
3.4.1 Power Flow Study in DIgSILENT 54 3.4.2 Short Circuit Calculation in DIgSILENT 55
3.5 Modeling of the Iraq system in DIgSILENT ...................................................... 58 3.6 Methodology of Analysis .................................................................................... 61
3.6.1 Load Flow Study 62 3.6.2 Fault Level Study 62
3.6.3 Protection System Study 62 3.7 Summary ............................................................................................................. 63
4. RESULTS AND DISSCUSSION .............................................................................. 64
4.1 Introduction ......................................................................................................... 64 4.2 Description of the Network Used ....................................................................... 67 4.3 Validation study .................................................................................................. 71
4.3.1 Load Flow Analysis Using IEEE System 71 4.3.2 Short-Circuit Analysis Using IEEE System 75
4.5 Short Circuit Level Investigation ........................................................................ 82 4.6 Performance of the Protection System ................................................................ 95
4.6.1 Blinding of Protection 95
4.6.1.1 Case 1: 3PH fault at 90% of feeder FA3 96 4.6.1.2 Case 2: 3PH fault at 90% of feeder SB4 97
4.6.2 Sympathetic Tripping 103 4.6.2.1 Case 1: 1LG Fault at OHL of Feeder FA3 103 4.6.2.2 Case 2: 1LG Fault at 90% of Feeder F-1 107
4.6.2.3 Case 3: 3PH Fault at 90% of Underground Feeder FA3 109
4.6.2.4 Case 4: 3PH Fault at SB4 112 4.6.3 Reduction in Reach of Distance Relay 116
4.6.3.1 Case1: Without DG Interconnection 116 4.6.3.2 Case2: With DG Interconnection 120
5. CONCLUSION AND RECOMMENDATION ...................................................... 127 5.1 Conclusion ........................................................................................................ 127 5.2 Achievement of Research Objective ................................................................. 128 5.3 Significance of Research Outcomes ................................................................. 129 5.4 Suggestions for Future Research ...................................................................... 129
REFERENCES .............................................................................................................. 131 APPENDIX A ................................................................................................................. 140 APPENDIX B ................................................................................................................. 149
vi
LIST OF TABLES
TABLE TITLE PAGE
2.1 Classification of DG depending on range of size 9
4.1 IEEE 4 node voltage-phase A 73
4.2 IEEE 4 node voltage-phase B 73
4.3 IEEE 4 node voltage-phase C 74
4.4 IEEE 4 node branch current 74
4.5 Comparison of 3HP and 1LG fault results 78
4.6 Base Case Load Flow at Al-Farabi Substation 80
4.7 Load Flow at Al-Farabi Substation with DG1 81
4.8 Variation of fault current [kA] at different buses 91
4.9 Rate of change in the fault current level 92
4.10 Change in the Equivalent Impedances at the fault points 93
4.11 Time overcurrent characteristics of relays R6, R7, and R9 98
4.12 Characteristics of overcurrent relay at intertie point 98
4.13 Characteristics of overcurrent relay at AL-Sebaq and up to
AL- Farabi substation 99
4.14 Results of 3PH fault at 90% of feeder FA3 99
4.15 Results of 3PH fault at 90% of feeder SB4 100
4.16 Results of 1LG fault at FA3 OHL 104
4.17 Results of 1LG fault at feeder f-1 107
4.18 Results of 3PH fault at feeder FA3 111
vii
4.19 Distance relay zones setting and reach operation 124
4.20 Reduction in reach as ratio % 124
A.1 Synchronous generator data 140
A.2 Excitation system model IEEE type DC2 (EXDC2) data 141
A.3 Diesel governor model (DEGOV) data 142
A.4 Transformer TR3 data 142
A.5 Transformers TR1 and TR2 data 143
A.6 Distribution transformers 143
A.7 Sub-transmission line data 132kV 143
A.8 Overhead line data 144
A.9 Underground cable 11kV (3×150 mm2) data 144
A.10 Underground cable 33kV (1×400 mm2) data 144
A.11 Underground cable 132 kV (1×800 mm2) data 144