Electric Power Distribution A S Pabla Consulting Engineer and Former Chief Engineer Punjab State Electricity Board McGraw-Hill New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto
Preface xvn 1. Power System 1.1 General Concept 7 1.2 Distribution of Power 4 1.3 Quality of Supply 12 1.4 System Study 15 1.5 Benchmarking 16 1.6 Electricity Reforms 19 1.7 Future Distribution Systems 20 Problems 24 Bibliography 24 2. Electricity Forecasting 2.1 Power Loads 26 2.2 Connected Load 33 2.3 Load Forecasting 41 2.4 Definitions of Some Basic Concepts in Statistics 2.5 Regression Analysis 45 2.6 Correlation Theory 50 2.7 Analysis of Time Series 51 2.8 Factors in Power System Loading 56 2.9 Unloading the System 59 2.10 Forecast of System Peak 63 2.11 Strategic Forecasting (10) 66 42 26
2.12 Spatial Load Forecasting 67 2.13 Technological Forecasting 69 2.14 Sources of Error: Regulating the Model 72 Problems 72 Bibliography 73 3. System Planning 74 3.1 Planning Process 74 3.2 Planning Criteria and Standards 81 3.3 System Development 83 3.4 Dispersed Generation 89 3.5 Distribution System Economics and Finance 92 3.6 Mapping 96 ; 3.7 Enterprise Resource Planning (ERP) 100 3.8 Modelling 103 3.9 System Calculations 104 3.10 Introductory Methods 107 3.11 Network Elements 7 72 3.12 Load Flow 777 3.13 Automated Planning 123 3.14 Fault Studies 131 3.15 Effect of Abnormal Loads 139 3.16 line Circuits 140 3.17 Urban Distribution 742 3.18 Outsourcing 143 Problems 144 Bibliography 145 4. Design and Operation 147 4.1 Engineering Design 147 4.2 Operation Criteria and Standards 757 4.3 Sub-transmission 153 4.4 Sub-station and Feeder 156 4.5 Low Voltage-Three-phase or Single-phase 162 4.6 Practices 164 4.7 Location of Sectionalizer 767 4.8 Voltage Control 168 4.9 Harmonics 178 4.10 Load Variations 189
ix '4.11 Impact Loading of Transformer 4.12 Ferroresonance 197 4.13 System Losses 199 4.14 Energy Management 276" 4.15 Model Distribution System 218 Problems 220 Bibliography 221 197 5. Distribution Automation 223 5.1 Distribution Automation (DA) 223 5.2 Project Planning 225 5.3 Definitions 227 5.4 Communication 232 /,5.5 Sensors 246 5.6 Supervisory Control and Data Acquisition (SCADA) 5.7 Consumer Information Service (CIS) 253 5.8 Geographical Information System (GIS) 254 5.9 Automatic Meter Reading (AMR) 254 5.10 Automation Systems 255 Problems 261 Bibliography 262 249 6. Optimization 6.1 Introduction 264 6.2 Costing of Schemes 265 6.3 Typical Network Configurations 277 6.4 Planning Terms 273 6.5 6.6 6.7 Network Cost Modelling 274 Voltage Levels 282 Synthesis of Optimum Line Networks 285 6.8 6.9 Applications of Linear Programming to Network Synthesis 292 Optimum Phasing Sequence 294 6.10 Economic Loading of Distribution Transformers 295 Worst-Case Loading of Distribution Transformers 303 6.12 Discussion 305 Problems 306 Bibliography 306 264
X Contents 7. Reliability and Quality 308 7.1 Introduction 308 7.2 Definition of Reliability 310 7.3 Failure 310 7.4 Probability Concepts 312 7.5 Limitations of Distribution Systems 317 7.6 Power Quality 320 7.7 Reliability Measurement 326 7.8 Power Supply Quality Survey [3] 333 7.9 Reliability Aids 334 Problems 341 Bibliography 341 8. Consumer Services 343 8.1 Supply Industry 343 8.2 Natural Monopoly 343 8.3 Regulations 344 8.4 Other Legal Provisions 349 8.5 Distribution Code 351 8.6 Consumer Care 352 8.7 Standards 353 8.8 Consumer Load Requirements 354 8.9 Consumer Factors 354 8.10 Least Cost of Supply 358 8.11 Revenue and Return 358 8.12 Load Management [2] 359 8.13 Energy Audit 375 8.14 Theft of Electricity 382 8.15 Metering of Energy 386 8.16 Periodical Testing of Meters 357 8.17 Consumer Load Monitoring 399 Problems 399 Bibliography 400 9. Tariffs and Billing 402 9.1 Objectives 402 9.2 Costing 404 9.3 Pricing Approach 410
XI 9.4 Classifications 412 9.5 Economically Efficient Tariff Structure 418 9.6 Electricity Market 420 9.7 Rational Tariffs 422 9.8 Tariff Applications 424 9.9 Billing 437 Problems 442 Bibliography 443 10. Grounding 10.1 Grounding System 444 10.2 Earth and Safety 446 10.3 Nature of an Earth Electrode System 449 10.4 Earth Conductor Sizes 452 10.5 Design of Earthing Electrodes 454 10.6 System Earthing 458 10.7 Earth Testing 472 Problems 476 Bibliography 477 11. Overhead Lines 11.1 Choice of the System 4 79 11.2 Optimum Design Considerations 481 11.3 Overhead Lines 482 11.4 Design of Overhead Power Lines 488 11.5 Overhead Line Construction 502 11.6 Vibrations 506 11.7 line Accessories 507 11.8 Installation of Distribution Transformer 516 11.9 Compact Lines 575 11.10 Aerial Bunched Cables (ABC) System 520 11.11 Service Line 521 Problems 522 Bibliography 522 12. Underground Cables 12.1 Circuit Design: Key to Reliability [6] 524 12.2 Determination of Cable Rating 536 12.3 Stress Grading 540 444 479 524
XII Contents 12 A Thermo-Mechanical Effects in Cable Systems 541 12.5 Cable Materials 542 12.6 Cable Jointing 544 12.7 Installation of Cables 546 12.8 Principal Causes of Cable Failure 553 12.9 Selection of Cables 554 12.10 System Fault Location 556" Problems 562 Bibliography 563 13. System Overvoltages 564 13.1 Causes of Overvoltages 564 13.2 Lightning 566 13.3 Protective Devices 569 13.4 Failure of Lightning Arresters 577 13.5 Detection of Arrester Failures in the Field 580 13.6 Allowable Maximum Distance of Separation 557 13.7 Travelling Waves 583 \ 13.8 Protection Schemes 585 13.9 Pole-Mounted Distribution Transformers 588 13.10 Cable Junction 589 13.11 Lightning Arresters: Earthing 590 Problems 592 Bibliography 592 14. Rural Supply 594 14.1 Rural System 596 14.2 Reliability 601 14.3 Faults and Protection 602 14 A Improvement of Existing Distribution Systems 6*05 14.5 Single Wire Earth Return System 609 14.6 Fault Locating 610 14.7 Auto-Reclosers 672 14.8 Determination of Rating of Induction Motor (Cage Type) 613 14.9 Constructional Practices 616 14.10 Future Orientation of Rural System 629 Problems 643 Bibliography 644
xiii 15. Power Capacitors 646 15.1 Reactive Power 646 15.2 Series and Shunt Capacitors 654 15.3 System Harmonics 665, 15.4 HT Shunt Capacitors' Installation Requirements 6"67 15.5 Size of Capacitors for Power Factor Improvement 671 15.6 LT Capacitors 672 15.7 Construction Features 679 15.8 Failures [7, 6] 680 Problems 682 Bibliography 683 16. Insulation Measurements 685 16.1 Insulation Supervision 685 16.2 Insulation Measurement-Non-Destructive Techniques [9] 686 16.3 Insulation Testing: Destructive Tests 697 16.4 Transformer Oil Testing 699 Problems 706 Bibliography 706 17. System Protection 708 17.1 Time Current Characteristics 708 17.2 Fuses 709 17.3 Switching Devices 717 17A Circuit Breakers 720 17.5 Protective Relaying 729 17.6 Instrument Transformers 742 17.7 Overcurrent Schemes 746 17.8 Unit Protection 748 Problems 749 Bibliography 750 if* System Maintenance * 751 B.I Successful Maintenance 751 16.2 Failures and Maintenance 757 18.3 Porcelain Insulators 764 18.4 Transformer Oil Maintenance 765 18.5 Transformer Drying 769
18.6 Maintenance Staff and Tools 772 18.7 Maintenance Costs 776 Problems 777 Bibliography 777 19. Electrical Services 779 19.1 Standards 779 19.2 Electrical Installations 779 19.3 Reception of Electric Supply 780 19.4 Supply Voltage 783 19.5 Consumer Supply Arrangement 785 19.6 Internal Wiring 790 19.7 Switchgear 796 19.8 Plug and Socket Outlets 798 19.9 Circuit Loading 798 19.10 Load Estimation 804 19.11 Earthing 506 19.12 Lighting 809 19.13 Lamps 570 19.14 Luminaires 572 19.15 Lighting Design 812 19.16 Road Lighting 814 19.17 Floodlighting 819 19.18 Automatic Fire Alarm System 527 19.19 Electrical Call Bell Services 824 19.20 Other Services 824 19.21 Lightning Protection 527 19.22 Standby Supplies 830 19.23 Voltage Stabilizers [5] 537 Problems 833 Bibliography 834 Appendix I: International Electricity Supplies 836 Appendix II: Conductors and Cable Data 841 Appendix III: Power Cable Laying Merits 852 Appendix IV: Village Electrification and Pumpset Energization 854 Appendix V: Electrical Accidents 856 Appendix VI: Illumination Levels 859 Appendix VII: Optimum Specific Energy Consumption 863 Appendix VIII: Tinned Copper Fuse Wire 865
XV Appendix IX: Power Factors 867 Appendix X: Ambient Temperature and Average Altitude 869 Appendix XI: Transmission and Distribution Losses in States 577 Index 873