F. Kiessling • P. Nefzger • J.F. Nolasco • U. Kaintzyk

Overhead Power LinesPlanning, Design, Construction

With 402 Figures and 193 Tables

Springer

Contents

1 Overall planning 11.0 Symbols 11.1 Development stages of a transmission project 11.2 Transmission planning 2

1.2.1 Objective 21.2.2 Planning stages 21.2.3 Planning aspects regarding transmission lines 3

1.3 Planning methods 31.3.1 Data acquisition and preparation 31.3.2 Formulation and preselection of alternatives 41.3.3 Electrical studies 41.3.4 Economic studies and final evaluation 4

1.4 Planning criteria 41.4.1 General 41.4.2 Criteria for steady-state conditions 51.4.3 Criteria for temporary and transient conditions 5

1.5 Evolution and selection of voltage levels 51.5.1 Evolution of transmission voltages 51.5.2 Introduction of transmission voltages 6

1.6 Conductor selection 81.7 Selection of line configuration 91.8 Direct current transmission 12

1.8.1 Aspects of DC transmission components 121.8.2 Economic comparison of DC and AC lines 121.8.3 Technical comparison of AC and DC transmission 131.8.4 Practical use of DC transmission 13

1.9 Transmission with higher order phase lines 141.9.1 Options 141.9.2 Properties of multiple-phase systems 151.9.3 Present experience 15

1.10 Investments 161.11 Licences and permit procedures 171.12 Underground transmission versus overhead lines 18

1.12.1 Application and planning aspects 181.12.2 Environmental constraints 191.12.3 Technical limitations 191.12.4 Comparative investments 191.12.5 Perspectives 20

1.13 Results of overall planning 211.14 References 22

2 Electric requirements and design 252.0 Symbols 252.1 Overhead lines as components of electric systems 28

2.1.1 Surge impedance and surge impedance load (natural power) 282.1.2 Stability 292.1.3 Voltage regulation and maximum permissible losses 30

XII Contents

2.1.4 Capability of a line 302.1.5 Reliability and availability 302.1.6 Reactive power compensation 312.1.7 Power transmitted versus right-of-way width 32

2.2 Current-related phenomena 322.2.1 Normal and emergency conditions 322.2.2 Ohmic losses 322.2.3 Short circuit condition 33

2.3 Voltage and current-related phenomena 332.3.1 Introduction 332.3.2 Electrical and magnetic fields 33

2.3.2.1 Effects on humans and animals 332.3.2.2 Effects on electronic devices 36

2.3.3 Corona phenomena and related effects 362.3.3.1 General 362.3.3.2 Calculation of voltage gradients on individual conductors 362.3.3.3 Calculation of voltage gradient by approximate formulae 372.3.3.4 Radio noise or radio interference (RI) 39

2.3.4 Audible noise (AN) 402.3.5 Impact of line design on voltage- and current-depending phenomena . . 42

2.4 Line performance and insulation requirements 432.4.1 Introduction 432.4.2 Power frequency voltages and temporary overvoltages 432.4.3 Slow-front overvoltages 462.4.4 Fast-front overvoltages 462.4.5 Principles of insulation coordination 46

2.4.5.1 General principles 462.4.5.2 Insulation design for permanent power frequency voltages 472.4.5.3 Insulation design for slow-front overvoltages 472.4.5.4 Insulation design for fast-front overvoltage 50

2.4.6 Live-line maintenance 512.5 Clearances 51

2.5.1 Clearance requirements 512.5.1.1 Types of electrical clearances 512.5.1.2 Calculation of electrical clearances 52

2.5.1.2.1 Required withstand voltages of air gaps 522.5.1.2.2 Voltages to be considered 542.5.1.2.3 Summary of formulae for electrical clearances 56

2.5.1.3 Empirical data for clearances 572.5.2 Internal and external clearances 58

2.5.2.1 Introduction 582.5.2.2 Design principles 582.5.2.3 Load cases for the calculation of clearances 59

2.5.2.3.1 Maximum conductor temperature at no-wind condition 592.5.2.3.2 Ice load without wind 592.5.2.3.3 Wind load assumptions 60

2.5.2.4 Insulator and conductor position under wind action 612.5.2.4.1 Definition of wind action 612.5.2.4.2 Calculation of swing angle 632.5.2.4.3 Time distribution of swing angles 642.5.2.4.4 Determination of swing angles by measurements 652.5.2.4.5 Conductor and insulator position according to standards . . . . 65

Contents XIII

2.5.2.5 Midspan clearances 652.5.2.6 Minimum clearances within a span or at a tower 672.5.2.7 Clearances to ground and obstacles 672.5.2.8 Examples 67

2.5.2.8.1 Electrical clearances for a 110 kV overhead line 672.5.2.8.2 Electrical clearances for a 380 kV overhead line 692.5.2.8.3 Electrical clearances for a 500 kV overhead line 702.5.2.8.4 Clearances to obstacles for line design, empirical approach . . . 712.5.2.8.5 Time distribution of swing angles 722.5.2.8.6 Tower top geometry according to statistic considerations . . . . 732.5.2.8.7 Tower top geometry according to European standards 742.5.2.8.8 Tower top geometry according to Brazilian practice 74

2.6 References 75

3 Electric parameters 793.0 Symbols 793.1 Introduction 803.2 Resistance 813.3 Positive-sequence impedance 81

3.3.1 Introduction 813.3.2 Inductance and inductive Reactance 82

3.4 Zero-sequence impedance 853.4.1 Introduction 853.4.2 Simplified approach for the determination of zero-sequence impedances 85

3.5 Capacitance and capacitive reactance 883.5.1 General considerations 883.5.2 Single-circuit lines 893.5.3 Double-circuit lines 90

3.6 Admittance 913.7 Electric representation of lines 92

3.7.1 Goals and basic conditions 923.7.2 Short- and medium-length lines 923.7.3 Long-length transmission lines 93

3.7.3.1 Representation by exponential functions 933.7.3.2 Representation by hyperbolic functions 943.7.3.3 The equivalent II-circuit of a long line 95

3.8 References 97

4 Lightning protection 994.0 Symbols 994.1 Significance of lightning 994.2 Formation of lightning strokes 100

4.2.1 Mechanism of lightning discharge 1004.2.2 Impulse behaviour of lightning discharges 1004.2.3 Electric characteristics of the discharges 101

4.3 Frequency and intensity of lightning strokes 1024.3.1 Keraunic levels and earth flash density 1024.3.2 Magnitude of lightning stroke currents 1044.3.3 Direct and indirect lightning strokes 105

4.4 Arrangement and efficiency of earth wires 1064.4.1 Theoretical background 1064.4.2 Effective shielding by earth wires 107

XIV Contents

4.4.3 Surge arresters 1104.4.4 Assessment of lightning performance of overhead lines 110

4.5 Earthing in view of lightning protection 1104.5.1 Significance of earthing for lightning protection 1104.5.2 Surge impedance of earthing systems I l l

4.6 References 112

5 Earthing 1155.0 Symbols 1155.1 Purpose of earthing 1165.2 Definitions and basic principles 1175.3 Requirements 118

5.3.1 Standards 1185.3.2 Safety of persons 1185.3.3 Thermal short-circuit strength 1195.3.4 Mechanical strength and corrosion resistance 1195.3.5 Currents to be considered 120

5.4 Earthing for personal safety purposes 1215.5 Operational earthing 1245.6 Lightning protection earthing 1245.7 Rating for short-term currents 1255.8 Soil resistivity and conductivity 1255.9 Calculation of earthing resistance 126

5.9.1 Spherical electrode 1265.9.2 Earthing rods 1275.9.3 Horizontally arranged electrode wires (counterpoises) 129

5.10 Measurements of soil resistivity 1305.10.1 Basic principles 1305.10.2 Measuring methods 131

5.11 Measurement of earthing resistance 1325.12 Earthing resistance in non-homogeneous soils 135

5.12.1 Soil resistivity in a two-layer soil structure 1355.12.2 Computation of earthing resistance in a two-layer soil structure . . . . 1365.12.3 Computation of earthing resistance by means of the apparent resistivity 1385.12.4 Computation of earthing resistance of three-dimensional structures . . 1385.12.5 Example for computation of earthing resistance 139

5.13 Practical rules for installation of earthing systems 1395.13.1 Radial and ring-type earthing counterpoises 1395.13.2 Vertically or obliquely driven earthing rods 1405.13.3 Bonding between earthing electrodes 1405.13.4 Earthing connections 140

5.14 References 140

6 Requirements on loading and strength 1436.0 Symbols 1436.1 Mechanical design of the overhead line system 145

6.1.1 Components and elements of an overhead line 1456.1.2 Reliability 1456.1.3 Calculation of reliability 1466.1.4 Strength coordination and selection of reliability 1506.1.5 Effect of maximum load intensity on a high number of components . . 1526.1.6 Use factor and its effect on the design 154

Contents XV

6.2 Strengths of line components and elements 1566.2.1 Strength limits 1566.2.2 Rating of individual components and elements 1576.2.3 Damage and failure limits 158

6.3 Wind loads 1586.3.1 Wind measurements 1586.3.2 Determination of meteorological reference wind velocities 159

6.3.2.1 Evaluation of wind measurements 1596.3.2.2 Effect of the terrain roughness 1626.3.2.3 Variation of reference wind velocity with height 163

6.3.3 Wind action on line components and elements 1636.4 Ice loads 165

6.4.1 Atmospheric icing 1656.4.2 Ice observations and measurements 1676.4.3 Determination of reference ice loads 168

6.4.3.1 Basic relations 1686.4.3.2 Evaluation of ice load information 1686.4.3.3 Reference ice load 1686.4.3.4 Loading of supports and load cases 169

6.5 Combined wind and ice loads 1696.5.1 Probability of occurrence and combination of parameters 1696.5.2 Determination of design parameters 170

6.5.2.1 Ice load 1706.5.2.2 Wind load 1706.5.2.3 Effective drag factors and ice densities 171

6.5.3 Wind action on the ice covered conductor 1716.6 Climatic loads according to relevant standards 172

6.6.1 Standards for overhead power lines 1726.6.2 Wind loads 172

6.6.2.1 Wind load model according to IEC 60 826 1726.6.2.2 Wind model according to the European standard EN 50 341-1 . . . 1746.6.2.3 Wind models according to EN 50 341-3 1766.6.2.4 Comparison of wind load models with measurements 179

6.6.3 Ice loads 1816.6.3.1 Ice load model according to IEC 60 826 1816.6.3.2 Ice load model according to EN 50 341-1 1826.6.3.3 Ice load model according to EN 50 341-3 183

6.6.4 Combined wind and ice action 1836.6.4.1 Model according to IEC 60 826 1836.6.4.2 Model according to EN 50 341-1 1846.6.4.3 Combined wind and ice action according to EN 50 341-3 184

6.7 Loads at construction, operation and maintenance 1856.7.1 Introduction 1856.7.2 Requirements according to IEC 60 826 1866.7.3 Requirements according to EN 50 341-1 and EN 50 341-3 186

6.8 Failure containment and other special loads 1876.8.1 Introduction 1876.8.2 Provisions according to IEC 60 826 1876.8.3 Provisions according to EN 50 341-1 187

6.9 Statistical distributions 1886.9.1 Introduction 1886.9.2 Normal distribution (Gaussian distribution) 188

XVI Contents

6.9.3 Log-normal distribution 1906.9.4 Gumbel distribution 190

6.10 References 192

7 Selection of conductors 1957.0 Symbols 1957.1 Conductor types and design 196

7.1.1 Introduction 1967.1.2 Conductor designation 1987.1.3 Progress in technical development 1987.1.4 Materials 200

7.1.4.1 Aluminium 2007.1.4.2 Aluminium-magnesium-silicon alloys 2017.1.4.3 Steel wires 2027.1.4.4 Aluminium-clad steel wires 2027.1.4.5 Copper and copper alloys 2027.1.4.6 Thermal resistant aluminium alloys 202

7.1.5 Wire testing 2037.1.5.1 Introduction 2037.1.5.2 Dimensions and surfaces 2037.1.5.3 Testing the tensile strength 2037.1.5.4 Wrapping and twisting test 2047.1.5.5 Testing zinc mass, cladding thickness and uniformity 2047.1.5.6 Testing resistivity 204

7.1.6 Conductors made of wires with the same material 2047.1.6.1 All aluminium conductors 2047.1.6.2 All aluminium alloy conductors 2057.1.6.3 Aluminium-clad steel conductors 2067.1.6.4 Copper, copper alloy and steel conductors 206

7.1.7 Composite conductors 2067.1.7.1 Configuration and design 2067.1.7.2 Characteristic data 2087.1.7.3 Production 2117.1.7.4 Joints 2127.1.7.5 Shipment 213

7.1.8 Conductor testing 2137.1.8.1 Classification of tests 2137.1.8.2 Extent of sample tests 2137.1.8.3 Surface condition, dimensions, inertness and mass 2147.1.8.4 Stress-strain diagram 2147.1.8.5 Tensile breaking strength 2157.1.8.6 Test of creep behaviour 2167.1.8.7 Testing the tension stringing ability of conductors 216

7.1.9 Bundle conductors 2177.1.10 Special conductor designs 218

7.1.10.1 Non-standardized conductors made of round wires 2187.1.10.2 Conductors for increased operation temperature 2197.1.10.3 Conductors with enlarged diameters 2207.1.10.4 Conductors with smooth surfaces 2217.1.10.5 Compacted conductors 2217.1.10.6 Self-damping conductors 2217.1.10.7 Vibration resistant conductors 222

Contents XVII

7.1.10.8 Low noise conductors 2227.1.10.9 Conductors with treated surfaces 223

7.2 Design with regard to current loading 2237.2.1 Introduction and requirements 2237.2.2 Principles for determination of conductor temperature 2247.2.3 Design with regard to current carrying capacity 2257.2.4 Design with regard to short-circuit current 2287.2.5 Design based on economic considerations 2287.2.6 Line capacity as a function of the weather conditions 231

7.3 Design with regard to stresses caused by voltages 2327.3.1 Introduction and requirements 2327.3.2 Design with respect to the electric parameters 2327.3.3 Design with respect to conductor surface gradients and corona effects . 2347.3.4 Corona losses 234

7.4 Mechanical design of conductors 2347.4.1 Introduction and requirements 2347.4.2 Stresses under extreme load conditions 2357.4.3 Stresses under everyday conditions 2367.4.4 Impact of the conductor tensile load on line investment 2377.4.5 Conductor creep 2387.4.6 Recommendations for selection of conductor tensile stresses 238

7.5 References 238

8 Earth wire selection 2438.0 Symbols 2438.1 Types of earth wires 2438.2 Electric and thermal design 244

8.2.1 Requirements 2448.2.2 Earth wire design under short-circuit conditions 2448.2.3 Temperature limits of earth wires in case of short circuits 2478.2.4 Fault clearing and reclosing operations 2478.2.5 Examples of earth wire current carrying capacity in case of short circuits248

8.3 Mechanical design 2508.3.1 Loss of mechanical strength during heating process 2508.3.2 Establishing tensile stresses and forces 251

8.4 Steps for selection of conventional earth wires 2518.5 Earth wires comprising optical fibres (OPGW) 252

8.5.1 Generalities and design 2528.5.2 Installation conditions 2548.5.3 Accessories 2548.5.4 Tests 255

8.6 References 255

9 Insulators 2579.0 Symbols 2579.1 Introduction 2579.2 Ceramic insulators 258

9.2.1 Insulator types and their application 2589.2.2 Raw materials 2629.2.3 Production 263

9.3 Glass insulators 2659.3.1 Raw materials and production 265

XVIII Contents

9.3.2 Insulator types and application 2669.4 Composite insulators 267

9.4.1 Raw materials, design and production 2679.4.2 Types of composite insulators and their application 268

9.5 Comparison of insulator types 2699.6 Tests on insulator units 271

9.6.1 Basic information 2719.6.2 Tests on ceramic and glass insulators 271

9.6.2.1 Type tests 2719.6.2.2 Sample tests 2739.6.2.3 Routine tests 275

9.6.3 Tests on composite insulators 2769.6.3.1 Basic information 2769.6.3.2 Test of the structural design and type test 2769.6.3.3 Sample and routine tests 277

9.7 Design of insulator sets 2789.7.1 Suspension insulator sets 2789.7.2 Tension insulator sets 281

9.8 Requirements for insulator sets 2819.8.1 Electric requirements for AC lines 2819.8.2 Particularities for DC lines 2849.8.3 Audible noise (AN) performance 2869.8.4 Mechanical design 287

9.9 Operational performance of insulator strings 2879.9.1 Introduction 2879.9.2 Voltage stresses 2889.9.3 Behaviour of individual insulator types 2909.9.4 Behaviour under pollution layers 292

9.9.4.1 Formation of pollution layers 2929.9.4.2 Simulation of pollution layers 2929.9.4.3 Pollution levels 2939.9.4.4 Assessment of pollution levels by means of local measurements . . . 2939.9.4.5 Measures to maintain insulation capacity 294

9.10 Testing of insulator sets 2959.10.1 Basic information and assumptions 2959.10.2 Standard atmospheric conditions 2959.10.3 Artificial rain 2959.10.4 Testing arrangements 2959.10.5 Power frequency voltage test 2969.10.6 Fast-front and slow-front overvoltage tests 2969.10.7 Power arc behaviour 2969.10.8 Radio interference strength test 2969.10.9 Corona onset or extinction voltage test 297

9.11 Example for insulator selection 2979.12 References 300

10 Overhead line fittings 30510.1 Definitions 30510.2 Fittings for conductors 305

10.2.1 Conductor attachment at suspension insulator sets 30510.2.2 Conductor attachments at dead-end terminations 30810.2.3 Turn buckles 309

Contents XIX

10.2.4 Connectors 30910.2.5 Spacers for bundle conductors 31010.2.6 Vibration dampers for single conductors 31110.2.7 Spacer dampers for bundle conductors 312

10.3 Fittings for insulator sets 31310.4 Rating and tests 313

10.4.1 General 31310.4.2 Electric requirements 31310.4.3 Mechanical requirements 31410.4.4 Corrosion protection 31510.4.5 Selection of material 31610.4.6 Tests 316

10.5 References 317

11 Conductor vibrations 32111.0 Symbols 32111.1 Overview and types of vibration 32211.2 Aeolian vibrations 323

11.2.1 Basic physical aspects, mathematic-mechanic model of a line 32311.2.2 Conductor free-span amplitude 32511.2.3 Conductor strains and stresses 32711.2.4 Bending stiffness of a conductor 32711.2.5 Origin of vibrations 32811.2.6 Consequences of vibrations 32911.2.7 Consequences for line design 33211.2.8 Verification of vibration intensity and effectiveness of damping measures 33611.2.9 Evaluation of vibration measurements 338

11.3 Subspan oscillations 34011.3.1 Origin and consequences 34011.3.2 Remedy measures 341

11.4 Galloping 34111.4.1 Origin and consequences 34111.4.2 Remedy measures 343

11.5 Short-circuit oscillations 34411.5.1 Origin and consequences 34411.5.2 Remedy measures 344

11.6 References 345

12 Supports 34912.0 Symbols 34912.1 Support types and their applications 354

12.1.1 Definitions 35412.1.2 Tasks of supports in an overhead line 354

12.1.2.1 Suspension supports 35412.1.2.2 Angle suspension supports 35512.1.2.3 Angle supports 35512.1.2.4 Strain and angle-strain supports 35512.1.2.5 Dead-end supports 35612.1.2.6 Special supports 356

12.1.3 Support design and application 35612.1.3.1 Selection of support design 35612.1.3.2 Self-supporting lattice steel towers 357

XX Contents

12.1.3.3 Self-supporting steel poles 35812.1.3.4 Steel-reinforced concrete poles 35912.1.3.5 Wood poles 36012.1.3.6 Guyed supports 36012.1.3.7 Crossarmless supports 360

12.2 Tower top geometry 36112.2.1 Requirements 36112.2.2 Electrical clearances according to relevant standards 36112.2.3 Clearance between conductors 361

12.2.3.1 Equal cross sections, alike materials and equal sags of conductors . 36112.2.3.2 Conductors with different cross sections, materials or sags 364

12.2.4 Clearances at supports 36512.3 Basic design requirements 367

12.3.1 Introduction 36712.3.2 Static design 36712.3.3 Design values and verification methods 368

12.4 Load cases and partial factors 36912.4.1 Combination of loads 36912.4.2 Extreme wind load 37012.4.3 Wind load at minimum temperature 37112.4.4 Uniform and unbalanced ice loads without wind 37112.4.5 Combined wind and ice load 37212.4.6 Construction and maintenance loads 37212.4.7 Security loads 37312.4.8 Partial factors for actions on supports 37312.4.9 Partial factors for materials 374

12.5 Lattice steel towers 37412.5.1 Structural design 374

12.5.1.1 Structural design of members 37412.5.1.2 Connections 37612.5.1.3 Walkways 37712.5.1.4 Production 37812.5.1.5 Corrosion protection 378

12.5.2 Materials 37912.5.2.1 Materials for angle sections and plates 37912.5.2.2 Material for bolts 379

12.5.3 Analysis of member forces 38012.5.4 Calculation of the member forces at a plane system 381

12.5.4.1 Basic procedure 38112.5.4.2 Forces in the leg members 38112.5.4.3 Forces in bracings, loaded by horizontal forces 38212.5.4.4 Forces in bracings, loaded by asymmetrical vertical forces 38312.5.4.5 Forces in bracings, loaded by torsional moments 38312.5.4.6 Total forces in bracings 38412.5.4.7 Forces in horizontal members at tower waist 38412.5.4.8 Forces in horizontal bracings within the tower body 38512.5.4.9 Forces in leg extensions 38512.5.4.10 Forces in crossarm members 386

12.5.5 Analysis of member forces at a three-dimensional system 38712.5.5.1 Basic approach of the finite element method 38712.5.5.2 Application to three-dimensional truss structure systems 395

12.5.6 Comparison of computations at plane and three-dimensional systems . 396

Contents XXI

12.5.7 General format of verification of members and connections 39812.5.8 Design of compression members 399

12.5.8.1 Effective cross section properties for compression members 39912.5.8.2 Flexural buckling of axially compressed members 39912.5.8.3 Flexural torsional buckling of centrally compressed members . . . . 40612.5.8.4 Bending and axial compression forces 408

12.5.9 Design of compound members 408L2.5.9.1 Member connected by batten plates 408L2.5.9.2 Laced box-type members 410

12.5.10 Design of tensile-loaded members 413L2.5.10.1 Members axially loaded in tension 413L2.5.10.2 Axial tensile force and bending 415

12.5.11 Design of connections 41512.5.12 Design for bending due to transverse loads 41712.5.13 Design of redundant members 41712.5.14 Deformation 41812.5.15 Calculation of foundation loads 42012.5.16 Application of computer programs for calculation of lattice steel towers 42112.5.17 Upgrading the support strength 42312.5.18 Example: Static calculation of a 110 kV suspension support 42512.5.19 Example: Calculation guy wire and mast loads in a guyed-V tower . . 440

12.6 Steel poles 44212.6.1 Structural design 44212.6.2 Analysis of loads 44312.6.3 Rating 44412.6.4 Example for design of a conical solid-wall steel pole 447

12.7 Steel-reinforced concrete poles 44912.7.1 Selection of cross sections 44912.7.2 Spun concrete poles 44912.7.3 Vibrated concrete poles 45112.7.4 Structural design 45112.7.5 Production 45112.7.6 Rating 45212.7.7 Example for design of a spun concrete pole 455

12.7.7.1 Basic data 45512.7.7.2 Calculation of loads 45512.7.7.3 Verification of cross sections 457

12.8 Wood poles 45912.8.1 Application and design 45912.8.2 Rating 46012.8.3 Treatment of wood poles 461

12.9 Loading and failing tests 46112.9.1 Introduction 46112.9.2 Foundations for support under test 46212.9.3 Material for the tower under test 46212.9.4 Fabrication of the prototype tower under test 46312.9.5 Strain measurements 46312.9.6 Assembly and erection 46312.9.7 Test loads 46312.9.8 Load application 46412.9.9 Load procedure 46412.9.10 Load measurement 464

XXII Contents

12.9.11 Deflections 46412.9.12 Acceptance and failures 46512.9.13 Destruction test 46512.9.14 Disposition of test tower 46512.9.15 Test report 465

12.10 References 466

13 Foundations 47113.0 Symbols 47113.1 Requirements and preconditions 47213.2 Types of subsoils 473

13.2.1 Classification of soil 47313.2.2 Undisturbed natural soil 47413.2.3 Rock 47513.2.4 Filled-up soil 475

13.3 Subsoil investigation 47513.3.1 Purpose of subsoil investigation 47513.3.2 Methods for obtaining soil samples 476

13.3.2.1 Type of samples 47613.3.2.2 Trial pits 47613.3.2.3 Exploratory borings 47713.3.2.4 Soil investigation by drilling probes 478

13.3.3 Probes 47813.3.3.1 Types of probes 47813.3.3.2 Driven probes 47813.3.3.3 Standard penetration test 48013.3.3.4 Van-type probes 48013.3.3.5 Compression probes 480

13.3.4 Evaluation of soil investigation 48113.3.4.1 Classification and description of soil types 48113.3.4.2 Classification of rock 48313.3.4.3 Concrete-aggressive water and soils 48513.3.4.4 Borehole log 48513.3.4.5 Graphical representation 487

13.4 Design and calculation of foundations 48813.4.1 Type of foundation and load 48813.4.2 Soil characteristics 48913.4.3 Compact foundations 490

13.4.3.1 Definition 49013.4.3.2 Monoblock foundations 49113.4.3.3 Monoblock foundations without base enlargement 49213.4.3.4 Monoblock foundation with base enlargement 49413.4.3.5 Slab foundations 49513.4.3.6 Single grillage foundation 49913.4.3.7 Single pile foundations 49913.4.3.8 Foundation of self-supporting timber poles 502

13.4.4 Separate foundations 50213.4.4.1 Definition 50213.4.4.2 Stepped block foundations 50313.4.4.3 Auger-bored and excavated foundations 50713.4.4.4 Separate grillage foundations 51113.4.4.5 Pile foundations 512

Contents XXIII

13.4.4.6 Steel reinforced pad and chimney foundation 51913.4.4.7 Foundations in rock 521

13.4.5 Anchoring of leg member stubs 52313.4.6 Foundation for guyed towers 524

13.4.6.1 Acting loads 52413.4.6.2 Central footings 52413.4.6.3 Foundations for guy wires 52513.4.6.4 Field tests 526

13.5 Testing of foundations 52713.5.1 Definitions and object 52713.5.2 Categories of tests 52713.5.3 Foundation installation 52813.5.4 Testing equipment 52813.5.5 Testing procedure 52913.5.6 Test evaluation and acceptance criteria 53113.5.7 Uplift load tests on construction and test piles 532

13.6 References 534

14 Sag and tension calculations 53914.0 Symbols 53914.1 Basis 54014.2 Sags described by the catenary curve 54014.3 Conductor sagging curve as a parabola 544

. 14.4 Span with differing attachment levels 54614.5 Conductor state change equation 546

; 14.6 Span with concentrated loads 54914.7 Span with tension insulator sets at both ends 55114.8 Conductor forces and sags in a tensioning section 553

14.8.1 Introduction 55314.8.2 Conductor state in spans with end points movable in line direction . . 55414.8.3 Conductor stresses and sags in case of inverted V-insulator sets . . . . 55614.8.4 Conductor state change equation for a tensioning section 55714.8.5 Computer program for conductor state change in a tensioning section . 56214.8.6 Approximate formulae of sags at ice load in one span only 562

' 14.9 Clearances to ground and to objects 56314.9.1 Requirements 56314.9.2 Calculation of clearance to ground 56414.9.3 Calculation of the clearance to a crossed road 56514.9.4 Calculation of clearance to a crossed line 567

14.10 References 570

15 Route selection and detailed line design 57315.0 Symbols 57315.1 Introduction 573

15.1.1 Basic information 57315.1.2 Preliminary activities 574

•15.2 Route selection and licences 57515.2.1 Introduction 575

15.2.1.1 General aspects and guidelines 57515.2.1.2 Alternative line designs 57715.2.1.3 Conversion of existing lines 57715.2.1.4 Underground transmission 577

XXIV Contents

15.2.2 Regulatory controls and permit procedures 57815.2.2.1 Introduction 57815.2.2.2 Permits 57815.2.2.3 Regulations, approvals and procedures 57815.2.2.4 Compensations 579

15.2.3 Environmental impact assessment 58015.2.3.1 Outline of the process 58015.2.3.2 Enviromental impact studies 58115.2.3.3 Existing environmental situation without the line project 58115.2.3.4 Reference alternative 58315.2.3.5 Environmental impacts of a new line 583

15.2.4 Route selection and line design in view of visual impact 58315.2.4.1 Introduction 58315.2.4.2 Conceptual approaches 58415.2.4.3 Assessment through qualitative methods 58415.2.4.4 Assessment through quantitative methods 58415.2.4.5 Routing for minimum visual impact 58515.2.4.6 Visualization of new lines 58715.2.4.7 Design of components to reduce visual impact 588

15.2.5 Route selection in view of people 59115.2.6 Route selection and line design in view of ecological systems 591

15.2.6.1 Introduction 59115.2.6.2 Impacts on avifauna 59115.2.6.3 Impacts on wild animals 59215.2.6.4 Impacts on vegetation 59315.2.6.5 Conservation and wilderness areas 593

15.2.7 Route selection in view of land use 59315.2.7.1 Introduction 59315.2.7.2 Agricultural areas 59315.2.7.3 Forestry 59415.2.7.4 Industrial areas and infrastructure developments 59415.2.7.5 Urban areas 595

15.3 Survey on site 59515.3.1 Steps of survey 59515.3.2 Survey procedures and instruments adopted 596

15.3.2.1 Direct survey in the terrain 59615.3.2.2 Indirect line survey 59815.3.2.3 Terrain data banks 600

15.3.3 Survey of angle points and line alignment 60015.3.4 Survey of terrain profile 60115.3.5 Location of supports 60115.3.6 Survey of existing lines 601

15.4 Line design and establishing of plans 60315.4.1 Clearances 60315.4.2 Determination of support locations, tower types and heights 605

15.4.2.1 Evaluation of the profile survey 60515.4.2.2 Basis and relevant parameters 60515.4.2.3 Manual tower spotting 60615.4.2.4 Tower spotting and optimization by means of data processing . . . 607

15.4.3 Documentation of lines 61015.5 Data processing for line design and administration 611

15.5.1 Data processing systems for planning of overhead lines 611

Contents XXV

15.5.2 Establishing the longitudinal profile 61115.5.3 Establishing the plan layout 61415.5.4 Graphical Information System with integrated data bank 61615.5.5 Administration of plans, lists and documents 617

15.6 References 617

16 Construction 62116.0 Symbols 62116.1 Construction planning 622

16.1.1 Introduction 62216.1.2 Construction time schedule 62216.1.3 Mobilisation and stockyard 623

16.2 Transportation 62416.2.1 Means of transport 62416.2.2 Access roads 62516.2.3 Fences, gates and cattle-guards 625

16.3 Construction of foundations 62516.3.1 Introduction 62516.3.2 Concrete foundations black and slab foundations 62516.3.3 Augerbored foundations 62616.3.4 Driven pile foundations 627

16.3.4.1 Common rules 62716.3.4.2 Steel piles 62816.3.4.3 Steel piles grouted by mortar 62816.3.4.4 Testing 629

\ j 16.3.5 Grillage foundations 62916.3.6 Anchor foundations 63016.3.7 Concrete for foundations 631

16.3.7.1 Ready-mixed and site-mixed concrete 63116.3.7.2 Constituent materials 63116.3.7.3 Requirements on concrete and concrete properties 63316.3.7.4 Ready-mixed concrete 63616.3.7.5 Site-mixed concrete 63616.3.7.6 Handling and placing the concrete 63816.3.7.7 Curing the concrete 638

; 16.3.7.8 Methods for verification of concrete properties 63916.3.7.9 Quality supervision and quality management 639

jffB.4 Installation of earthing 64018.5 Setting of tower stubs or bases 641

16.5.1 Methods and tools 641|T 16.5.2 Inclination of angle and dead-end towers 642|$6.6 Erection of supports 645h 16.6.1 Introduction 645?i 16.6.2 Assembly and erection by elevation 645fi 16.6.3 Tower erection using a crane 645

. 16.6.4 Tower erection by means of a gin pole 646SS. 16.6.4.1 Procedures 646| i 16.6.4.2 Erection with a gin pole outside the tower 646| t 16.6.4.3 Erection with gin pole in the tower centre 647

16.6.4.4 Erection with a gin pole in the tower at a leg member 648& 16.6.5 Erection of guyed towers 648

16.6.5.1 Hoisting of a crossarm using a gin pole 648

XXVI Contents

16.6.6 Tower erection using helicopters 64916.6.6.1 Manual method 65016.6.6.2 Use of an auxiliary mast 65016.6.6.3 Erection by cranes 651

16.6.7 Bolts and torques 65216.7 Installation of insulator sets and hardware 653

16.7.1 Insulator sets 65316.7.2 Joints 653

16.8 Conductor stringing 65316.8.1 General requirements 65316.8.2 Stringing methods 65416.8.3 Conductor stringing equipment 655

16.8.3.1 Requirements 65516.8.3.2 Pulling ropes 65516.8.3.3 Rope connections 65616.8.3.4 Stringing blocks 65716.8.3.5 Puller for conductor stringing 65716.8.3.6 Tensioner 65916.8.3.7 Reel stands 660

16.8.4 Conductor stringing 66016.8.4.1 Preparations 66016.8.4.2 Stringing procedure 66116.8.4.3 Sagging the conductors 66216.8.4.4 Terminating the conductors 66316.8.4.5 Clipping-in of conductors 66316.8.4.6 Installation of jumper loops 66416.8.4.7 Installation of dampers and bundle spacers 66416.8.4.8 Conductor replacement 66416.8.4.9 Stringing conductors with optical fibres 66516.8.4.10 Installation of conductors adjacent to or crossing energized lines . . 665

16.8.5 Determination of initial sags 66616.8.5.1 Requirements 66616.8.5.2 Position of the conductor on stringing blocks and in clamps . . . . 66616.8.5.3 Impact of conductor creep 67016.8.5.4 Example: Sagging data for an overhead line in a mountainous area . 672

16.9 References 673

17 Commissioning, operation and line management 67717.0 Symbols 67717.1 Commissioning 677

17.1.1 Introduction 67717.1.2 Supervision of approval, design and manufacturing stage 67817.1.3 Supervision and acceptance of construction 67917.1.4 Final inspection and acceptance 68117.1.5 Quality assurance 68217.1.6 Performance tests 682

17.1.6.1 Measurements of tower earthing resistance 68217.1.6.2 Power losses and electrical resistance of conductors 68217.1.6.3 Line energization test 68417.1.6.4 Electrical and magnetic fields (EMF) 68517.1.6.5 Vibration performance measurements 685

17.1.7 Energization and commence of operation 686

Contents XXVII

,17.2 Operation 68617.2.1 Real-time monitoring of conductor ampacity 686

17.2.1.1 Targets and benefits 68617.2.1.2 Direct methods 68717.2.1.3 Indirect methods 68817.2.1.4 Examples and experience 688

17.2.2 Thunderstorm monitoring and forecast 68917.2.3 Ice observations 69017.2.4 Galloping alerting system 69117.2.5 Insulator contamination and performance 691

| JT.3 Asset management 69317.3.1 Definitions 693

' 17.3.2 Introduction and targets 69417.3.3 Risk management of line assets 69417.3.4 Net present value of annual expenditures 69517.3.5 Planned expenditures 69517.3.6 Risk of failure 69617.3.7 Consequences of a failure 69617.3.8 Overhead line asset management process 697

-17.3.9 Data base 69817.3.10 Management options 699

' 17.3.11 Example on management of risk of failure 70017.3.11.1 Basic data 70017.3.11.2 Calculation of planned expenditures and risks 70017.3.11.3 Management options and assessment 701

?.4 Maintenance 702'17.4.1 Introduction 702

£'17.4.2 Inspection 70317.4.2.1 Reasons and procedures for inspections 70317.4.2.2 Inspection classification and frequency 70417.4.2.3 Foundations and stubs 70617.4.2.4 Supports including corrosion protection 70717.4.2.5 Conductors 70817.4.2.6 Joints and fittings 71117.4.2.7 Insulators 71217.4.2.8 Clearances 713

f17.4.3 Corrective maintenance 71417.4.3.1 Strategy 71417.4.3.2 Refurbishment and upgrading of foundations 71417.4.3.3 Renewal of coating, replacement of tower components 71417.4.3.4 Repair of conductors 71517.4.3.5 Replacement of insulators, fittings, dampers and spacers 715

17.4.3.5.1 Tasks and priorities 71517.4.3.5.2 Dead-line work 71617.4.3.5.3 Live-line work 716

17.4.3.6 Clearing of right-of-way, trimming of trees 71717.4.3.7 Access roads 71917.4.3.8 Earthing 719

117.4.4 Investigation of line failures 71917.4.4.1 General 71917.4.4.2 Causes of failure 71917.4.4.3 Investigation procedures 720

XXVIII Contents

17.4.4.4 Experience on line failures 72117.5 Reliability and availability 723

17.5.1 Introduction and definitions 72317.5.2 Energy availability, general description and guidelines 725

17.5.2.1 Availability 72517.5.2.2 Determination of energy availability, example 726

17.6 Line refurbishment, upgrading and uprating 72717.6.1 Definitions 72717.6.2 Uprating 728

17.6.2.1 Current uprating 72817.6.2.2 Uprating by reconductoring or voltage increase 72817.6.2.3 Replacement of earth wire by optical cables (OPGW) 729

17.6.3 Upgrading 72917.6.3.1 Introduction 72917.6.3.2 Upgrading of a 380/220 kV river crossing in Germany 72917.6.3.3 Upgrading of a 380/110 kV line in view of increased ice loads . . . 730

17.7 References 731

Index 735