EBOOK - Electric Power Transmission System Engineering Analysis and Design (Turan Gonen) | Cộng đồng Kỹ thuật cơ điện Việt Nam EBOOKBKMT

EBOOK - Phân tích và thiết kế kỹ thuật hệ thống truyền tải điện (Turan Gonen) - 878 Trang.

The structure of an electric power system is very large and complex. Nevertheless, its main components (or subsystems) can be identified as the generation system, transmission system, and distribution system. These three systems are the basis of the electric power industry.

Today, there are various textbooks dealing with a broad range of topics in the power system area of electrical engineering. Some of them are considered to be classics. However, they do not particularly concentrate on topics dealing specifically with electric power transmission. Therefore, this text is unique in that it is specifically written for in-depth study of modern power transmission engineering.

CONTENTS:

I Electrical Design and AnalysisSEctIon

1Chapter Transmission System Planning .......................................................3

1.1 Introduction .................................................................3

1.2 Aging Transmission System ...................................................3

1.3 Benefits of Transmission ...............................4

1.4 Power Pools ....................................................6

1.5 Transmission Planning ............8

1.6 Traditional Transmission System Planning Techniques ..........................................................8

1.7 Models Used in Transmission System Planning ...................................................................11

1.8 Transmission Route Identification and Selection ..................................................................11

1.9 Traditional Transmission System Expansion Planning .........................................................11

1.9.1 Heuristic Models .......................................................................................................12

1.9.2 Single-Stage Optimization Models ...........................................................................13

1.9.2.1 Linear Programming (LP) ..........................................................................13

1.9.2.2 Integer Programming ..................................................................................14

1.9.2.3 Gradient Search Method .............................................................................15

1.9.3 Time-Phased Optimization Models ..........................................................................15

1.10 Traditional Concerns for Transmission System Planning .....................................................16

1.10.1 Planning Tools ..........................................................................................................16

1.10.2 Systems Approach ....................................................................................................17

1.10.3 Database Concept ..................................................................................................... 17

1.11 New Technical Challenges ....................................................................................................

1.12 Transmission Planning after Open Access ............................................................................21

1.13 Possible Future Actions by Federal Energy Regulatory Commission... ................................22

2Chapter Transmission Line Structures and Equipment ..............27

2.1 Introduction ...........................................................................................................................27

2.2 The Decision Process to Build a Transmission Line .............................................................27

2.3 Design Tradeoffs ...................................................................................................................29

2.4 Traditional Line Design Practice ...........................................................................................30

2.4.1 Factors Affecting Structure Type Selection .............................................................31

2.4.2 Improved Design Approaches ..................................................................................31

2.5 Environmental Impact of Transmission Lines ...................................................................... 33

2.5.1 Environmental Effects .............................................................................................. 33

2.5.2 Biological Effects of Electric Fields ......................................................................... 33

2.5.3 Biological Effects of Magnetic Fields.......................................................................34

2.6 Transmission Line Structures ................................................................................................35

2.6.1 Compact Transmission Lines....................................................................................35

2.6.2 Conventional Transmission Lines .............................................................................38

2.6.3 The Design of Line Support Structures ....................................................................38

2.7 Subtransmission Lines ...........................................................................................................40

2.7.1 Subtransmission Line Costs ......................................................................................42

2.8 Transmission Substations ......................................................................................................43

2.8.1 Additional Substation Design Considerations ..........................................................48

2.8.2 Substation Components ............................................................................................49

2.8.3 Bus and Switching Configurations ...........................................................................50

2.8.4 Substation Buses .......................................................................................................51

2.8.4.1 Open-Bus Scheme ....................................................................................54

2.8.4.2 Inverted-Bus Scheme ................................................................................55

2.9 Sulfur Hexafluoride (SF6

)-Insulated Substations ..................................................................56

2.10 Transmission Line Conductors ..............................................................................................56

2.10.1 Conductor Considerations .........................................................................................56

2.10.2 Conductor Types .......................................................................................................58

2.10.3 Conductor Size ..........................................................................................................59

2.10.3.1 Voltage Drop Considerations ....................................................................60

2.10.3.2 Thermal Capacity Considerations ............................................................60

2.10.3.3 Economic Considerations .........................................................................62

2.10.4 Overhead Ground Wires (OHGW) ...........................................................................62

2.10.5 Conductor Tension ....................................................................................................62

2.11 Insulators ...............................................................................................................................63

2.11.1 Types of Insulators ....................................................................................................63

2.11.2 Testing of Insulators .................................................................................................64

2.11.3 Voltage Distribution over a String of Suspension Insulators ....................................66

2.11.4 Insulator Flashover due to Contamination................................................................70

2.11.5 Insulator Flashover on Overhead High-Voltage DC (HVDC) Lines ........................73

2.12 Substation Grounding ............................................................................................................74

2.12.1 Elecric Shock and Its Effects on Humans ................................................................74

2.12.2 Ground Resistance ....................................................................................................77

2.12.3 Soil Resistivity Measurements..................................................................................78

2.12.4 Substation Grounding ...............................................................................................81

2.12.5 Ground Conductor Sizing Factors ............................................................................83

2.12.6 Types of Ground Faults .............................................................................................84

2.12.6.1 Line-to-Line-to-Ground Fault ..................................................................84

2.12.6.2 Single-Line-to-Ground Fault ....................................................................85

2.12.7 Ground Potential Rise ...............................................................................................85

2.13 Transmission Line Grounds ..................................................................................................86

2.14 Types of Grounding ...............................................................................................................87

2.15 Transformer Connections ......................................................................................................88

2.16 Autotransformers in Transmission Substations .....................................................................88

2.17 Transformer Selection ...........................................................................................................89

2.18 Transformer Classifications ...................................................................................................89

3Chapter Fundamental Concepts ...............................93

3.1 Introduction ...........................................................................................................................93

3.2 Factors Affecting Transmission Growth ...............................................................................93

3.3 Stability Considerations .........................................................................................................94

Contents xi

3.4 Power Transmission Capability of a Transmission Line .......................................................96

3.5 Surge Impedance and Surge Impedance Loading of a Transmission Line ...........................96

3.6 Loadability Curves ................................................................................................................96

3.7 Compensation ........................................................................................................................98

3.8 Shunt Compensation ............................................................................................................100

3.8.1 Effects of Shunt Compensation on Transmission Line Loadability .......................100

3.8.2 Shunt Reactors and Shunt Capacitor Banks ...........................................................100

3.9 Series Compensation ...........................................................................................................101

3.9.1 The Effects of Series Compensation on Transmission Line Loadability ...............101

3.9.2 Series Capacitors ....................................................................................................102

3.10 Static Var Control (SVC) .....................................................................................................107

3.11 Static Var Systems ...............................................................................................................109

3.12 Thyristor-Controlled Series Compensator...........................................................................109

3.13 Static Compensator ..............................................................................................................110

3.14 Thyristor-Controlled Braking Resistor ................................................................................111

3.15 Superconducting Magnetic Energy Systems ....................................................................... 112

3.16 Subsynchronous Resonance (SSR) ......................................................................................113

3.17 The Use of Static Compensation to Prevent Voltage Collapse or Instability ......................113

3.18 Energy Management System (EMS) ...................................................................................114

3.19 Supervisory Control and Data Acquisition .........................................................................115

3.20 Advanced Scada Concepts ..................................................................................................116

3.20.1 Substation Controllers.............................................................................................117

3.21 Six-Phase Transmission Lines .............................................................................................119

Overhead Power Transmission .......................................................................................................123

4.1 Introduction .........................................................................................................................123

4.2 Short Transmission Lines (up to 50 mi, or 80 km) ..............................................................123

4.2.1 Steady-State Power Limit .......................................................................................126

4.2.2 Percent Voltage Regulation .....................................................................................128

4.2.3 Representation of Mutual Impedance of Short Lines .............................................133

4.3 Medium-Length Transmission Lines (up to 150 mi, or 240 km) ........................................133

4.4 Long Transmission Lines (above 150 mi, or 240 km) .........................................................143

4.4.1 Equivalent Circuit of Long Transmission Line ......................................................152

4.4.2 Incident and Reflected Voltages of Long Transmission Line .................................155

4.4.3 Surge Impedance Loading of Transmission Line ...................................................158

4.5 General Circuit Constants ................161

4.5.1 Determination of A, B, C, and D Constants ...........................................................162

4.5.2 A, B, C, and D Constants of Transformer .............................................................. 168

4.5.3 Asymmetrical πand T Networks ........................................................................... 169

4.5.4 Networks Connected in Series ................................................................................ 170

4.5.5 Networks Connected in Parallel ............................................................................. 172

4.5.6 Terminated Transmission Line ............................................................................... 174

4.5.7 Power Relations Using A, B, C, and D Line Constants .......................................... 178

4.6 Bundled Conductors ............................................................................................................

4.7 Effect of Ground on Capacitance of Three-Phase Lines..................................................... 187

4.8 Environmental Effects of Overhead Transmission Lines .................................................... 188

Underground Power Transmission and Gas-Insulated Transmission Lines .................................. 197

5.1 Introduction .........................................................................................................................

5.2 Underground Cables ............................................................................................................

5.3 Underground Cable Installation Techniques .......................................................................202

5.4 Electrical Characteristics of Insulated Cables .....................................................................204

5.4.1 Electric Stress in Single-Conductor Cable .............................................................204

5.4.2 Capacitance of Single-Conductor Cable .................................................................209

5.4.3 Dielectric Constant of Cable Insulation ..................................................................211

5.4.4 Charging Current .................................................................................................... 212

5.4.5 Determination of Insulation Resistance of Single-Conductor Cable ..................... 213

5.4.6 Capacitance of Three-Conductor Belted Cable ...................................................... 215

5.4.7 Cable Dimensions ...................................................................................................222

5.4.8 Geometric Factors ...................................................................................................222

5.4.9 Dielectric Power Factor and Dielectric Loss ..........................................................226

5.4.10 Effective Conductor Resistance ..............................................................................229

5.4.11 Direct-Current Resistance ......................................................................................230

5.4.12 Skin Effect ..............................................................................................................231

5.4.13 Proximity Effect .....................................................................................................232

5.5 Sheath Currents in Cables ................................................................................................... 233

5.6 Positive- and Negative-Sequence Reactances .....................................................................238

5.6.1 Single-Conductor Cables ........................................................................................238

5.6.2 Three-Conductor Cables .........................................................................................239

5.7 Zero-Sequence Resistance and Reactance ..........................................................................240

5.7.1 Three-Conductor Cables .........................................................................................240

5.7.2 Single-Conductor Cables ........................................................................................245

5.8 Shunt Capacitive Reactance ................................................................................................251

5.9 Current-Carrying Capacity of Cables .................................................................................253

5.10 Calculation of Impedances of Cables in Parallel ................................................................253

5.10.1 Single-Conductor Cables ........................................................................................253

5.10.2 Bundled Single-Conductor Cables ..........................................................................257

5.11 Ehv Underground Cable Transmission ................................................................................262

5.12 Gas-Insulated Transmission Lines ......................................................................................269

5.13 Location of Faults in Underground Cables ..........................................................................274

5.13.1 Fault Location by Using Murray Loop Test ...........................................................274

5.13.2 Fault Location by Using Varley Loop Test .............................................................275

5.13.3 Distribution Cable Checks ...................................................................................... 276

Direct-Current Power Transmission ..............................................................................................281

6.1 Introduction .........................................................................................................................281

6.2 Overhead High-Voltage DC Transmission ..........................................................................281

6.3 Comparison of Power Transmission Capacity of High-Voltage DC and AC ......................282

6.4 High Voltage DC Transmission Line Insulation .................................................................287

6.5 Three-Phase Bridge Converter ............................................................................................291

6.6 Rectification .........................................................................................................................291

6.7 Per-Unit Systems and Normalizing .....................................................................................302

6.7.1 Alternating-Current System Per-Unit Bases ...........................................................303

6.7.2 Direct-Current System Per-Unit Bases ...................................................................304

6.8 Inversion ..............................................................................................................................309

6.9 Multibridge (B-Bridge) Converter Stations .........................................................................316

6.10 Per-Unit Representation of B-Bridge Converter Stations ....................................................319

6.10.1 Alternating-Current System Per-Unit Bases ...........................................................322

6.10.2 Direct-Current System Per-Unit Bases ...................................................................323

Contents xiii

6.11 Operation of Direct-Current Transmission Link .................................................................325

6.12 Stability of Control ..............................................................................................................328

6.13 The Use of “Facts” and HVDC to Solve Bottleneck Problems

in the Transmission Networks .............................................................................................332

6.14 High-Voltage Power Electronic Substations ........................................................................332

6.15 Additional Recommends on HVDC Converter Stations .....................................................333

Transient Overvoltages and Insulation Coordination ....................................................................343

7.1 Introduction .........................................................................................................................343

7.2 Traveling Waves ..................................................................................................................343

7.2.1 Velocity of Surge Propagation ................................................................................347

7.2.2 Surge Power Input and Energy Storage ..................................................................348

7.2.3 Superposition of Forward- and Backward-Traveling Waves ..................................350

7.3 Effects of Line Terminations ...............................................................................................350

7.3.1 Line Termination in Resistance ..............................................................................352

7.3.2 Line Termination in Impedance .............................................................................353

7.3.3 Open-Circuit Line Termination ..............................................................................357

7.3.4 Short-Circuit Line Termination ..............................................................................358

7.3.5 Overhead Line Termination by Transformer ..........................................................358

7.4 Junction of Two Lines ..........................................................................................................359

7.5 Junction of Several Lines.....................................................................................................361

7.6 Termination in Capacitance and Inductance .......................................................................363

7.6.1 Termination through Capacitor ..............................................................................363

7.6.2 Termination through Inductor ................................................................................365

7.7 Bewley Lattice Diagram ......................................................................................................365

7.8 Surge Attenuation and Distortion ........................................................................................368

7.9 Traveling Waves on Three-Phase Lines ..............................................................................368

7.10 Lightning and Lightning Surges .......................................................................................... 371

7.10.1 Lightning ................................................................................................................371

7.10.2 Lightning Surges .....................................................................................................373

7.10.3 The Use of Overhead Ground Wires for Lightning Protection of the

Transmission Lines .................................................................................................375

7.10.4 Lightning Performance of Transmission Lines ......................................................375

7.11 Shielding Failures of Transmission Lines ...........................................................................378

7.11.1 Electrogeometric (EGM) Theory ...........................................................................378

7.11.2 Effective Shielding..................................................................................................380

7.11.3 Determination of Shielding Failure Rate ................................................................380

7.12 Lightning Performance of UHV Lines ................................................................................382

7.13 Stroke Current Magnitude ...................................................................................................382

7.14 Shielding Design Methods .................................................................................................. 383

7.14.1 Fixed-Angle Method ............................................................................................... 383

7.14.2 Empirical Method (or Wagner Method) .................................................................384

7.14.3 Electrogeometric Model .........................................................................................384

7.15 Switching and Switching Surges .........................................................................................387

7.15.1 Switching ................................................................................................................387

7.15.2 Causes of Switching Surge Overvoltages ...............................................................389

7.15.3 Control of Switching Surges ...................................................................................390

7.16 Overvoltage Protection ........................................................................................................390

7.17 Insulation Coordination .......................................................................................................397

7.17.1 Basic Definitions .....................................................................................................397

7.17.1.1 Basic Impulse Insulation Level (BIL) .....................................................397

7.17.1.2 Withstand Voltage ...................................................................................397

7.17.1.3 Chopped-Wave Insulation Level .............................................................397

7.17.1.4 Critical Flashover (CFO) Voltage ............................................................397

7.17.1.5 Impulses Ratio (for Flashover or Puncture of Insulation) .......................397

7.17.2 Insulation Coordination ..........................................................................................397

7.17.3 Insulation Coordination in Transmission Lines .....................................................400

7.18 Geomagnetic Disturbances and Their Effects on Power System Operations .....................404

Limiting Factors for Extra-High and Ultrahigh Voltage Transmission: Corona,

Radio Noise, and Audible Noise ....................................................................................................

8.1 Introduction ............................................................ 411

8.2 Corona ................................................................................................................................. 411

8.2.1 Nature of Corona .................................................................................................... 411

8.2.2 Manifestations of Corona ....................................................................................... 412

8.2.3 Factors Affecting Corona ....................................................................................... 413

8.2.4 Corona Loss ............................................................................................................418

8.3 Radio Noise .........................................................................................................................421

8.3.1 Radio Interference (RI) .......................................................................................... 422

8.3.2 Television Interference ............................................................................................426

8.4 Audible Noise (AN) ...........................................427

8.5 Conductor Size Selection ................................................................427

Symmetrical Components and Fault Analysis ...............................................................................

9.1 Introduction .........................................................................................................................

9.2 Symmetrical Components ...................................................................................................

9.3 The Operator a .......................................436

9.4 Resolution of Three-Phase Unbalanced System of Phasors into Its Symmetrical

Components .........................................................................................................................438

9.5 Power in Symmetrical Components ...........................................

9.6 Sequence Impedances of Transmission Lines .....................................................................443

9.6.1 Sequence Impedances of Untransposed Lines .......................................................443

9.6.2 Sequence Impedances of Transposed Lines ...........................................................445

9.6.3 Electromagnetic Unbalances due to Untransposed Lines ......................................447

9.6.4 Sequence Impedances of Untransposed Line with Overhead Ground Wire ..........454

9.7 Sequence Capacitances of Transmission Line ....................................................................455

9.7.1 Three-Phase Transmission Line without Overhead Ground Wire .........................455

9.7.2 Three-Phase Transmission Line with Overhead Ground Wire ..............................458

9.8 Sequence Impedances of Synchronous Machines...............................................................462

9.9 Zero-Sequence Networks .............................465

9.10 Sequence Impedances of Transformers .............................467

9.11 Analysis of Unbalanced Faults .......................471

9.12 Shunt Faults ..........................472

9.12.1 Single Line-to-Ground Fault ..................................................................................475

9.12.2 Line-to-Line Fault...................................................................................................483

9.12.3 Double Line-to-Ground Fault .................................................................................486

9.12.4 Three-Phase Fault ...................................................................................................491

Contents xv

9.13 Series Faults ........................495

9.13.1 One Line Open (OLO).........................................................................................496

9.13.2 Two Lines Open (TLO) .......................................................................................497

9.14 Determination of Sequence Network Equivalents for Series Faults .................................497

9.14.1 Brief Review of Two-Port Theory .......................................................................497

9.14.2 Equivalent Zero-Sequence Networks ..................................................................500

9.14.3 Equivalent Positive- and Negative-Sequence Networks .....................................500

9.15 System Grounding .................................504

9.16 Elimination of SLG Fault Current by Using Peterson Coils .............................................509

9.17 Six-Phase Systems .............................................................................................................512

9.17.1 Application of Symmetrical Components ...........................................................512

9.17.2 Transformations ...................................................................................................513

9.17.3 Electromagnetic Unbalance Factors ....................................................................515

9.17.4 Transposition on the Six-Phase Lines .................................................................516

9.17.5 Phase Arrangements ............................................................................................517

9.17.6 Overhead Ground Wires .....................................................................................517

9.17.7 Double-Circuit Transmission Lines ....................................................................517

1Chapter 0 Protective Equipment and Transmission System Protection ..

10.1 Introduction .................535

10.2 Interruption of Fault Current ............................... 535

10.3 High Voltage Circuit Breakers (CB) .....................537

10.4 CB Selection ......................................................................................................................540

10.5 Disconnect Switches ..........................................................................................................544

10.6 Load-Break Switches .........................................................................................................544

10.7 Switchgear .........................................................................................................................544

10.8 The Purpose of Transmission Line Protection ..................................................................545

10.9 Design Criteria for Transmission Line Protection .............................................................545

10.10 Zones of Protection ............................................................................................................547

10.11 Primary and Backup Protection ........................................................................................ Reclosing............................................................................................................................ 550

10.13 Typical Relays Used on Transmission Lines .....................................................................552

10.13.1 Overcurrent Relays .............................................................................................. 553

10.13.1.1 Inverse-Time Delay Overcurrent Relays ........................................... 553

10.13.1.2 Instantaneous Overcurrent Relays ..................................................... 553

10.13.1.3 Directional Overcurrent Relays ......................................................... 553

10.13.2 Distance Relays ...................................................................................................554

10.13.2.1 Impedance Relay ...............................................................................554

10.13.2.2 Admittance Relay .............................................................................. 554

10.13.2.3 Reactance Relay ................................................................................ 555

10.13.3 Pilot Relaying ......................................................................................................562

10.14 Computer Applications in Protective Relaying .................................................................564

10.14.1 Computer Applications in Relay Settings and Coordination ..............................565

10.14.2 Computer Relaying ..............................................................................................565

1Chapter 1 Transmission System Reliability.................................................................................................... 573

11.1 National Electric Reliability Council (NERC) ..................................................................573

11.2 Index of Reliability ............................................................................................................573

xvi Contents

11.3 Section 209 of Purpa of 1978 ..............................................................................................575

11.4 Basic Probability Theory .....................................................................................................580

11.4.1 Set Theory .............................................................................................................581

11.4.2 Probability and Set Theory ................................................................................... 583

11.5 Combinational Analysis ......................................................................................................588

11.6 Probability Distributions .....................................................................................................589

11.7 Basic Reliability Concepts ...................................................................................................592

11.7.1 Series Systems .......................................................................................................600

11.7.2 Parallel Systems .....................................................................................................602

11.7.3 Combined Series-Parallel Systems ........................................................................603

11.8 Systems with Repairable Components ................................................................................604

11.8.1 Repairable Components in Series ..........................................................................604

11.8.2 Repairable Components in Parallel .......................................................................607

11.9 Reliability Evaluation of Complex Systems ........................................................................609

11.9.1 Conditional Probability Method ............................................................................609

11.9.2 Minimal-Cut-Set Method ......................................................................................610

11.10 Markov Processes ................................................................................................................612

11.11 Transmission System Reliability Methods ..........................................................................616

11.11.1 Average Interruption Rate Method ........................................................................616

11.11.2 Frequency and Duration Method ...........................................................................616

11.11.2.1 Series Systems ......................................................................................617

11.11.2.2 Parallel Systems ...................................................................................618

11.11.3 Markov Application Method .................................................................................620

11.11.4 Common-Cause Forced Outages of Transmission Lines ......................................624

II Mechanical Design and AnalysisSEctIon

12 Chapter

Construction of Overhead Lines ....................................................................................................641

12.1 Introduction ......................................................................................................................... 641

12.2 Factors Affecting Mechanical Design of Overhead Lines ..................................................643

12.3 Character of Line Route ......................................................................................................643

12.4 Right-of-Way .......................................................................................................................643

12.5 Mechanical Loading ............................................................................................................644

12.5.1 Definitions of Stresses ...........................................................................................644

12.5.2 Elasticity and Ultimate Strength ...........................................................................645

12.5.3 NESC loadings ......................................................................................................646

12.5.4 Wind Pressure........................................................................................................647

12.6 Required Clearances............................................................................................................648

12.6.1 Horizontal Clearances ...........................................................................................648

12.6.2 Vertical Clearances ................................................................................................648

12.6.3 Clearances at Wire Crossings ................................................................................648

12.6.4 Horizontal Separation of Conductors from Each Other ........................................649

12.7 Type of Supporting Structures ............................................................................................651

12.7.1 Pole Types ..............................................................................................................651

12.7.2 Soil Types and Pole Setting ...................................................................................653

12.8 Mechanical Calculations .....................................................................................................655

12.8.1 Introduction ...........................................................................................................655

12.8.2 Bending Moment due to Wind on Conductors .......................................................656

12.8.3 Bending Moment due to Wind on Poles .................................................................657

12.8.4 Stress due to Angle in Line.....................................................................................662

12.8.5 Strength Determination of Angle Pole ...................................................................663

12.8.6 Permissible Maximum Angle without Guys...........................................................664

12.8.7 Guying ....................................................................................................................665

12.8.8 Calculation of Guy Tension ....................................................................................665

12.9 Grade of Construction .........................................................................................................670

12.10 Line Conductors ..................................................................................................................670

12.11 Insulator Types ....................................................................................................................671

12.12 Joint Use by Other Utilities .................................................................................................672

12.13 Conductor Vibration ............................................................................................................673

12.14 Conductor Motion Caused by Fault Currents ......................................................................676

1Chapter 3 Sag and Tension Analysis ..........679

13.1 Introduction .........................................................................................................................679

13.2 Effect of Change in Temperature ........................................................................................680

13.3 Line Sag and Tension Calculations .....................................................................................681

13.3.1 Supports at Same Level ..........................................................................................681

13.3.1.1 Catenary Method .....................................................................................681

13.3.1.2 Parabolic Method ....................................................................................688

13.3.2 Supports at Different Levels: Unsymmetrical Spans .............................................692

13.4 Spans of Unequal Length: Ruling Span ..............................................................................693

13.5 Effects of Ice and Wind Loading ........................................................................................694

13.5.1 Effect of Ice ............................................................................................................694

13.5.2 Effect of Wind ........................................................................................................696

13.6 National Electric Safety Code .............................................................................................699

13.7 Line Location ......................................................................................................................700

13.7.1 Profile and Plan of Right-of-Way ............................................................................702

13.7.2 Templates for Locating Structures ..........................................................................703

13.7.3 Supporting Structures .............................................................................................706

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