Power Cables and their Application Parti

Materials • Construction Criteria for Selection Project Planning Laying and Installation • Accessories Measuring and Testing

Editor: Lothar Heinhold

3rd revised edition, 1990

Siemens Aktiengesellschaft

Contents

Constructional Elements of Insulated Cables

1 Conductors 11

1.1 Wiring Cables and Flexible Cables . . 12 1.2 Power Cables 13

2 Insulation 15

2.1 Polymers 15 2.1.1 Thermoplastics (Plastomers) . . . . 17

Copolymers • Fluoroplastics • Poly­vinyl Chloride (PVC) • Polyethylene (PE)-Cross-Linked Polyethylene (XLPE)

2.1.2 Elastomers 23 Thermoplastic Elastomers (TPE)-Con­ducting Rubber-Natural Rubber (NR)-Styrene Butadiene Rubber (SBR) • Nitrile Butadiene Rubber (NBR)-Butyl Rubber (IIR)-Ethylene-Propylene Rubber (EPR)-Silicone Rubber (SiR) • Ethylene Vinyl Acetate (EVA)

2.1.3 Thermosetting Polymers (Duromers) 26 2.2 Chemical Aging of Polymers . . . . 27 2.3 The Influence of Moisture on

Polyolefine Insulating Materials . . . 30 2.4 Impregnated Paper 35 2.5 Literature Referred to in Section 2 . . 35

3 Protective Sheaths 37

3.1 Thermoplastic Sheaths 37 3.2 Elastomer Sheaths 38 3.3 Sheathing Materials for Special

Purposes 39 3.4 Metal Sheath 39

4 Protection against Corrosion 41

4.1 Cable with Lead Sheath 41 4.2 Aluminium-Sheathed Cables . . . . 42

5 Armour 43

6 Concentric Conductors 44

7 Electrical Screening 45

7.1 Conducting Layers 45 7.2 Metallic Components of Electrical

Screening 46 7.3 Longitudinally Water Proof Screens. . 47

Insulated Wires and Flexible Cables

8

8.1 8.1.1 8.1.2 8.1.3 8.1.4 8,2 8.2.1 8.2.2 8.2.3 8.3

8.4

9

10

Types of Wires and Cables 49

National and International Standards 49 VDE Specifications 49 Harmonized Standards 49 National Types 54 IEC Standards 55 Selection of Flexible Cables 55 Cables for Fixed Installations . . . . 56 Flexible Cables 62 FLEXO Cords 74 Flexible Cables for Mining and Industry 75 Halogen-Free SIENOPYR Wiring and Flexible Cables with Improved Performance in the Event of Fire . . 79

Core Identification of Cables

Definition of Locations to DIN VDE 0100 . . . .

82

11 Application and Installation of Cables 86

11.1 Rated Voltage, Operating Voltage . . 88 11.2 Selection of Conductor Cross-Sectional

Area 89

Power Cables

12 National and International Standards

12.1 12.2 12.3

13

13.1 13.2 13.3

VDE Specifications Standards of Other Countries . IEC and CENELEC Standards

93

93 94 94

Types of Construction of Low- and High-Voltage Cables 97

General 97 Type Designation 100 Selection of Cables and Accessories 102

14 Power Cables for Special Applications 124

14.1 Cable with Elastomer Insulation . . .124 14.2 Shipboard Power Cable 124 14.2.1 Construction and Characteristics . . 124

14.2.2 Application and Installation . . . . 125 14.3 Halogen-Free Cables with Improved

Characteristics in the Case of Fire . . . 125 14.3.1 Testing Performance under Conditions

of Fire 125 Spread of Fire • Corrosivity of Combus­tion Gases-Smoke Density. Insulation Retention under Conditions of Fire

14.3.2 Construction and Characteristics . . 128 14.3.3 Laying and Installation 129 14.4 Cables for Mine Shafts and Galleries 129 14.5 River and Sea Cables 130 14.6 Airport Cables 131 14.7 Cable with Polymer Insulation and

Lead Sheath 131 14.8 Insulated Overhead Line Cables . . . 132

15 High-and Extra-High-Voltage Cables . 134

15.1 Cable with Polymer Insulation . . . 134 15.2 Low-Pressure Oil-Filled Cable with

Lead or Aluminium Sheath 135 15.3 Thermally Stable Cable in Steel Pipe 138 15.3.1 High-Pressure Oil-Filled Cable . . . 138 15.3.2 Internal Gas-Pressure Cable 139 15.3.3 External Gas-Pressure Cable (Pressure

Cable) 139

Planning of Cable Installations

16 Guide for Planning of Cable Installations 141

17 Cable Rated Voltages 146

17.1 Allocation of Cable Rated Voltages 146 17.2 Rated Lightning Impulse Withstand

Voltage 147 17.3 Voltage Stresses in the Event of Earth

Fault 147

18 Current-Carrying Capacity in Normal Operation 150

18.1 Terms, Definitions and Regulations 150 18.2 Operating Conditions and Design

Tables 152 18.2.1 Operating Conditions for Installations

in Ground 152 18.2.2 Operating Conditions, Installation in

Air 157 18.2.3 Project Design Tables 159

Load Capacity Installed in Ground/Air-Rating Factors for Installation in Ground, for Differing Air Temperatures and for Groups in Air

18.2.4 18.3 18.4 18.4.1 18.4.2

18.4.3

18.4.4

18.4.5

18.4.6

18.5 18.5.1 18.5.2 18.5.3 18.6

18.6.1 18.6.2 18.6.3 18.6.4 18.6.5 18.6.6 18.7 18.8

19 19.1 19.2

19.2.1

19.2.2

Use of Tables 180 Calculation of Load Capacity . . . .181 Thermal Resistances 184 Thermal Resistance of the Cable . . .184 Thermal Resistance of Air 186 Horizontal Installation-Vertical Installa­tion • Atmospheric Pressure • Ambient Temperature • Solar Radiation • Arrange­ment of Cables Thermal Resistance of the Soil . . . 197 Temperature Field of a Cable • Definition of Soil-Thermal Resistance • Daily Load Curve and Characteristic Diameter-Dry­ing-Out of the Soil and Boundary Iso­therm dx • Fictitious Soil-Thermal Resis­tance 7*x and T^ • Load Capacity Grouping in the Ground 207 Fictitious Additional Thermal Resistances AJX' and ATx'y due to Grouping-Load Ca­pacity-Extension of the Dry Area-Cur­rent-Carrying Capacity of Dissimilar Cables Installation in Ducts and Pipes . . . 213 Thermal Resistances 7^ and Tp • Load Capacity for an Installation of Pipes in Ground or Air or in Ducts Banks Soil-Thermal-Resistivity 218 Cable in the Ground - Physical and Ther­mal Characteristics of Soil • Influence of Moisture Content Measuring Basic Quantities for Calculation-Bedding Mate­rial Sand-Gravel Mixtures • Sand-Cement Mixtures • Calculation of Load Capacity Installation in Channels and Tunnels . 230 Unvcntilated Channels and Tunnels . 230 Arrangement of Cables in Tunnels . . 233 Channels with Forced Ventilation . . 235 Load Capacity of a Cable for Short-Time and Intermittent Operation . . 239 General 239 Calculation with Minimum Time Value 239 Adiabatic Heat Rise 241 Root-Mean-Square Value of Current . 241 Short-Time Operation 242 Intermittent Operation 243 Symbols Used in Formulae in Section 18 245 Literature Referred to in Section 18 . . 250

Short-Circuit Conditions 253 General 253 Temperature Rise of Conductor under Line-To-Earth Short Circuit . . . . 257 Conductor and Sheat Currents under Line-To-Earth Short Circuit . . . . 257 Load Capacity under Line-To-Earth Short-Circuit 259

19.3 Short-Circuit Thermal Rating . . . . 265 19.3.1 Guide for Project Design 265

Performance under Short-Circuit Condi­tions • Short-Circuit Duty • Short-Circuit Capacity of Conductor, Screens, Sheaths and Armour

19.3.2 Calculations of Short-Circuit Capacity 285 Adiabatic and Non-Adiabalic Tempera­ture Rise Method Temperature Rise dur­ing Short-Circuit

19.3.3 Thermo-Mechanical Forces and Expansion 292 General • Effect of Thermal Expansion in Cables-Mounting of Single-Core Cables

19.3.4 Accessories 296 19.4 Mechanical Short-Circuit Capacity . . 297 19.4.1 Electromagnetic Forces 297

Effect of Electromagnetic Forces • Line-To-Earth, Line-To-Line and Balanced Three-Phase Short Circuit

19.4.2 Multi-Core Cable 300 Tensile Force F^-Surface Pressure FF-Cable Construction • Experience and Calculation Quantities • Fixing Elements

19.4.3 Single-Core Cables and Fixing Methods 305 Bending Stress • Surface Pressure FF • Stressing of Clamps and Binders

19.4.4 Accessories 315 19.5 Symbols used in Formulae

in Section 19 316 19.6 Literature Referred to in Section 19 . 319

20 Resistance and Resistance per Unit Length of Conductor 320

20.1 Resistance per Unit Length on d.c. 320 20.2 Resistance per Unit Length on a.c. . . 320 20.3 Current Related Losses 321

21 Inductance and Inductance per Unit Length 322

21.1 Inductance per Unit Length of a Conductor System 322

21.2 Single-Core Cables 322 21.2.1 Earthed at Both Ends 322 21.2.2 Arrangement of Cables 326 21.2.3 Earthing from Either One or Both

Ends of Metal Sheath or Screen . . . 328 21.2.4 Cross-Bonding of the Sheaths,

Transposition of the Cables 328 21.3 Multi-Core Cables 329 21.4 Zero-Sequence Impedance and Zero-

Sequence Impedance per Unit Length 329 21.5 Literature Referred to in Section 21 . 330

22

22.1 22.2

22.3

22.4

23

24

24.1 24.2 24.3

25

25.1

25.2

26

26.1 26.1.1 26.1.2 26.1.3

26.1.4

26.1.5

26.2 26.3 26.4 26.5 26.6

27

27.1 27.2

27.2.1 27.2.2

27.2.3 27.3 27.3.1 27.3.2

Capacitance and Capacitance per Unit Length 331

General 331 Operating Capacitance per Unit Length C{, 331 Capacitive Current re and Earth-Fault Current I'e of a Cable 334 Dielectric Losses 336

Insulation Resistance, Insulation Resistance per Unit Length and Leakage 337

Determination of Voltage Drop . . . 340

General 340 Short Cable Runs 340 Long Cable Runs 340

Economic Optimization of Cable Size 343

Symbols used in Formulae in Section 25 347 Literature Referred to in Section 25 . 347

Interference of Power Cables with Control and Telecommunication Cables 349

Inductive Interference 351 Mutual Inductance 351 Inducing Currents 352 Current Reduction Factor of the Influencing Power Cable 352 Voltage Reduction Factor of the Influenced Telecommunication Cable . 355 Reduction Factors of Compensating Conductors 357 Noise Voltage in Symmetrical Circuits 358 Ohmic Interference 358 Inductive and Ohmic Interference . . 359 Details Required for Planning . . . . 359 Calculated Example 360

Design and Calculation of Distribution Systems 362 Introduction 362 Determination of Power Requirement as a Basis for Planning 363 Load Requirement of Dwellings . . . 363 Load Requirements of Special Consumers 365 Total Load 366 Planning of Distribution Systems . . 366 General 366 Selection of Distribution Voltage . . 367

27.3.3 Low-Voltage Systems 368 System Configuration and Types of Op­eration in the Public Supply-Extension of a Low-Voltage System Systems of Build­ings-Industrial Supply Systems • Location of Substations • Component Parts of the Low-Voltage System

27.3.4 Medium-Voltage Systems 375 Public Supply-Expansion of the Medium-Voltage System-Distribution Systems in Large Buildings • Industrial Supply Sys­tems Standby Power Supply-Component Parts of the Medium-Voltage System • Charge Current Compensation and Star Point Treatment • The Superimposed High-Voltage System

27.4 System Calculation 381 27.4.1 Basics 381 27.4.2 Calculation of a Low-Voltage System 383 27.4.3 Investigations of Protective Measures

Against Excessive Touch Voltage . .385 27.4.4 Investigation of Short-Circuit

Protection and Discrimination . . . .389 27.4.5 Computer-Aided System Calculation . 392 27.5 Literature Referred to in Section 27 . 393

Laying and Installation

28 Cable Identification Marking . . . . 395

28.1 Manufacturers, VDE-Marking . . . 395 28.2 Colours of Outer Sheaths and

Protective Coverings 395 28.3 Core Identification for Power Cables

up to U0/U=0.6/l kV 397 28.4 Core Identification for Cables for

Rated Voltages Exceeding i y t / = 0 . 6 / l kV 398

29 Laying the Cables 399

29.1 Transporting 399 29.2 Preparation for Laying the Cable . . 400 29.3 Differences in Level of the Cable

Route 401 29.4 Laying of Cables in the Ground . . . 401 29.4.1 Cable Route 401 29.4.2 Laying of the Cables 403 29.5 Laying of Cables Indoors 408 29.5.1 Cables on Walls, Ceilings or Racks . . 408 29.5.2 Cable Tunnels and Ducts 408 29.6 Cable Clamps 410 29.6.1 Types of Clamps 411 29.6.2 Arrangements and Dimensions . . . 412

30 Installation Guide 415 30.1 Preparation of Cable Ends 415

30.2

30.3

31

31.1

31.2

32 32.1 32.2 32.3 32.4

32.4.1 32.4.2 32.4.3 32.4.4 32.4.5 32.4.6 32.5

33

Earthing of Metallic Sheaths and Coverings 416 Conductor Jointing 418

Repair of Damage to Outer Sheath . . 420

Outer Sheath of Polyvinylchloride (PVC) and Polyethylene (PE) . . . . 420 Jute Servings on Cables with Lead Sheath 423

Cable Accessories 424

Fundamental Objectives 424 Requirements 424 Stress Control 426 Fundamental Principles for the Construction and Installation of Accessories 427 Compound Filling Technique . . . . 427 Cast-Resin Techniques 429 Shrink-On Technique 433 Lapping Technique 434 Push-On Technique 435 Plug Technique 437 Literature Referred to in Section 32 . 437

Cable Plan 438

Measuring and Testing of Power Installations

34 Electrical Measurements in the Cable Installation, as Installed 439

35 Voltage Tests 440

35.1 General 440 35.2 Testing with d.c. Voltage 440 35.3 Testing with a.c. Voltage 442

36 Locating Faults 443 36.1 Preliminary Measurements 443 36.2 Location Measurements by the

Conventional Method 444 36.3 Locating of Faults by Pulse Reflection

Method 447 36.4 Preparation of Fault Point by Burn-

Through 449 36.5 Locating Using Audio Frequency . . 450 36.6 Testing of Thermoplastic Sheaths . . 452

37 Construction and Resistance of Conductors 454

38 Conversion Table 457

Index 458