# Short Circuits in Power Systems: A Practical Guide to IEC 60909-0, 2nd Edition

ISBN: 978-3-527-34136-8
312 pages
January 2018

## Description

Reflecting the changes to the all-important short circuit calculations in three-phase power systems according to IEC 60909-0 standard, this new edition of the practical guide retains its proven and unique concept of explanations, calculations and real-life examples of short circuits in electrical networks. It has also been completely revised and expanded by 20% to include the standard-compliant prevention of short circuits in electrical networks for photovoltaics and wind energy. By understanding the theory any software allows users to perform all the necessary calculations with ease so they can work on the design and application of low- and high-voltage power systems.
This book is a practitioner's guide intended for students, electrical engineers, engineers in power technology, the electrotechnical industry, engineering consultants, energy suppliers, chemical engineers and physicists in industry.
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Preface xi

Acknowledgments xiii

1 Definitions:Methods of Calculations 1

1.1 Time Behavior of the Short-Circuit Current 2

1.2 Short-Circuit Path in the Positive-Sequence System 3

1.3 Classification of Short-Circuit Types 5

1.4 Methods of Short-Circuit Calculation 7

1.4.1 Superposition Method 7

1.4.2 Equivalent Voltage Source 10

1.4.3 Transient Calculation 11

1.4.4 Calculating with Reference Variables 12

1.4.4.1 The Per-Unit Analysis 12

1.4.4.2 The %/MVA Method 14

1.4.5 Examples 14

1.4.5.1 Characteristics of the Short-Circuit Current 14

1.4.5.2 Calculation of Switching Processes 14

1.4.5.3 Calculation with pu System 14

1.4.5.4 Calculation with pu Magnitudes 16

1.4.5.5 Calculation with pu System for an Industrial System 17

1.4.5.6 Calculation with MVA System 19

2 Fault Current Analysis 23

3 The Significance of IEC 60909-0 29

4 Supply Networks 33

4.1 Calculation Variables for Supply Networks 34

4.2 Lines Supplied from a Single Source 35

4.4 Ring Networks 35

4.5 Meshed Networks 37

5 Network Types for the Calculation of Short-Circuit Currents 39

5.1 Low-Voltage Network Types 39

5.2 Medium-Voltage Network Types 39

5.3 High-Voltage Network Types 44

6 Systems up to 1 kV 47

6.1 TN Systems 48

6.1.1 Description of the System is Carried Out by Two Letters 48

6.2 Calculation of Fault Currents 49

6.2.1 System Power Supplied from Generators: 50

6.3 TT systems 52

6.3.1 Description of the System 52

6.4 IT Systems 53

6.4.1 Description of the System 53

6.5 Transformation of the Network Types Described to Equivalent Circuit Diagrams 54

6.6 Examples 56

6.6.1 Example 1: Automatic Disconnection for a TN System 56

6.6.1.1 Calculation for a Receptacle 56

6.6.1.2 For the Heater 56

6.6.2 Example 2: Automatic Disconnection for a TT System 57

7 Neutral Point Treatment in Three-Phase Networks 59

7.1 Networks with Isolated Free Neutral Point 63

7.2 Networks with Grounding Compensation 64

7.3 Networks with Low-Impedance Neutral Point Treatment 66

7.4 Examples 69

7.4.1 Neutral Grounding 69

8 Impedances of Three-Phase Operational Equipment 71

8.1 Network Feed-Ins, Primary Service Feeder 71

8.2 Synchronous Machines 73

8.2.1 a.c. Component 78

8.2.2 d.c. Component 78

8.2.3 Peak Value 78

8.3 Transformers 80

8.3.1 Short-Circuit Current on the Secondary Side 81

8.3.2 Voltage-Regulating Transformers 83

8.4 Cables and Overhead Lines 85

8.5 Short-Circuit Current-Limiting Choke Coils 96

8.6 Asynchronous Machines 97

8.7 Consideration of Capacitors and Nonrotating Loads 98

8.8 Static Converters 98

8.9 Wind Turbines 99

8.9.1 Wind Power Plant with AG 100

8.9.2 Wind Power Plant with a Doubly Fed Asynchronous Generator 101

8.9.3 Wind Power with Full Converter 101

8.10 Short-Circuit Calculation on Ship and Offshore Installations 102

8.11 Examples 104

8.11.1 Example 1: Calculate the Impedance 104

8.11.2 Example 2: Calculation of a Transformer 104

8.11.3 Example 3: Calculation of a Cable 105

8.11.4 Example 4: Calculation of a Generator 105

8.11.5 Example 5: Calculation of a Motor 106

8.11.6 Example 6: Calculation of an LV motor 106

8.11.7 Example 7: Design and Calculation of aWind Farm 106

8.11.7.1 Description of theWind Farm 106

8.11.7.2 Calculations of Impedances 111

8.11.7.3 Backup Protection and Protection Equipment 116

8.11.7.4 Thermal Stress of Cables 118

8.11.7.5 Neutral Point Connection 119

8.11.7.6 Neutral Point Transformer (NPT) 119

8.11.7.7 Network with Current-Limiting Resistor 120

8.11.7.8 Compensated Network 124

8.11.7.9 Insulated Network 125

8.11.7.10 Grounding System 125

9 Impedance Corrections 127

9.1 Correction Factor KG for Generators 128

9.2 Correction Factor KKW for Power Plant Block 129

9.3 Correction Factor KT for Transformers with Two and Three Windings 130

10 Power SystemAnalysis 133

10.1 The Method of Symmetrical Components 136

10.2 Fundamentals of Symmetrical Components 137

10.2.1 Derivation of the Transformation Equations 139

10.3 General Description of the Calculation Method 140

10.4 Impedances of Symmetrical Components 142

11 Calculation of Short-Circuit Currents 147

11.1 Three-Phase Short Circuits 147

11.2 Two-Phase Short Circuits with Contact to Ground 148

11.3 Two-Phase Short CircuitWithout Contact to Ground 149

11.4 Single-Phase Short Circuits to Ground 150

11.5 Peak Short-Circuit Current, ip 153

11.6 Symmetrical Breaking Current, Ia 155

11.7 Steady-State Short-Circuit Current, Ik 157

12 Motors in Electrical Networks 161

12.1 Short Circuits at the Terminals of Asynchronous Motors 161

12.2 Motor Groups Supplied from Transformers with TwoWindings 163

12.3 Motor Groups Supplied from Transformers with Different Nominal Voltages 163

13 Mechanical and Thermal Short-Circuit Strength 167

13.1 Mechanical Short-Circuit Current Strength 167

13.2 Thermal Short-Circuit Current Strength 173

13.3 Limitation of Short-Circuit Currents 176

13.4 Examples for Thermal Stress 176

13.4.1 Feeder of a Transformer 176

13.4.2 Mechanical Short-Circuit Strength 178

14 Calculations for Short-Circuit Strength 185

14.1 Short-Circuit Strength for Medium-Voltage Switchgear 185

14.2 Short-Circuit Strength for Low-Voltage Switchgear 186

15 Equipment for Overcurrent Protection 189

16 Short-Circuit Currents in DC Systems 199

16.1 Resistances of Line Sections 201

16.2 Current Converters 202

16.3 Batteries 203

16.4 Capacitors 204

16.5 Direct Current Motors 205

17 Power Flow Analysis 207

17.1 Systems of Linear Equations 208

17.2 Determinants 209

17.3 Network Matrices 212

17.3.2 Impedance Matrix 213

17.3.3 Hybrid Matrix 213

17.3.4 Calculation of Node Voltages and Line Currents at Predetermined Load Currents 214

17.3.5 Calculation of Node Voltages at Predetermined Node Power 215

17.3.6 Calculation of Power Flow 215

17.3.6.1 Type of Nodes 216

17.3.6.2 Type of Loads and Complex Power 216

17.3.7 Linear Load Flow Equations 218

17.3.8 Load Flow Calculation by Newton–Raphson 219

17.3.9 Current Iteration 223

17.3.9.1 Jacobian Method 223

17.3.10 Gauss–Seidel Method 224

17.3.11 Newton–Raphson Method 224

17.3.12 Power Flow Analysis in Low-Voltage Power Systems 226

17.3.13 Equivalent Circuits for Power Flow Calculations 227

17.3.14 Examples 228

17.3.14.1 Calculation of Reactive Power 228

17.3.14.2 Application of Newton Method 228

17.3.14.3 Linear Equations 229

17.3.14.4 Application of Cramer’s Rule 229

17.3.14.5 Power Flow Calculation with NEPLAN 230

18 Examples: Calculation of Short-Circuit Currents 233

18.1 Example 1: Radial Network 233

18.2 Example 2: Proof of Protective Measures 235

18.3 Example 3: Connection Box to Service Panel 237

18.4 Example 4: Transformers in Parallel 238

18.5 Example 5: Connection of a Motor 240

18.6 Example 6: Calculation for a Load Circuit 241

18.7 Example 7: Calculation for an Industrial System 243

18.8 Example 8: Calculation ofThree-Pole Short-Circuit Current and Peak Short-Circuit Current 244

18.9 Example 9: Meshed Network 246

18.10 Example 10: Supply to a Factory 249

18.11 Example 11: Calculation with Impedance Corrections 250

18.12 Example 12: Connection of a TransformerThrough an External Network and a Generator 253

18.13 Example 13: Motors in Parallel and their Contributions to the Short-Circuit Current 255

18.14 Example 14: Proof of the Stability of Low-Voltage Systems 257

18.15 Example 15: Proof of the Stability of Medium-Voltage and High-Voltage Systems 259

18.16 Example 16: Calculation for Short-Circuit Currents with Impedance Corrections 269

Bibliography 273

Standards 277

Explanations of Symbols 281

Symbols and Indices 283

Indices 286

Secondary Symbols, Upper Right, Left 287

American Cable Assembly (AWG) 287

Index 289

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## Author Information

Ismail Kasikci is Professor at the University of Applied Sciences Biberach, Germany. His main research area is electrical energy supply, design of electrical installations of buildings, solar electricity, wind power generation, building integrated renewables, design and protection of distribution power system, smart grids, solar and wind power, connectivity requirements, focused on the IEC/EN and VDE regulations. Ismail Kasikci received his Bachelor in electrical and electronics engineering from the Technical University Darmstadt and his PhD from the University of Brunel, United Kingdom. He published 17 books in German, English and Turkish and more than 64 international scientific publications. He is a member by VDE and IEEE. He is Associated Editor of the international Journal of Power and Energy Systems by ACTA press in the States and Canada. Since 2005 he is a member of the German norm group, K221 [IEC TC 64 (VDE 0100)]. He has more than 18 years of professional experience in planning and design of electrical power systems.
He plays since 1994 an active role in Turkey for educational purposes and in the regulation of IEC and EN. Within the scope of the EU Erasmus program he gives lectures at the University of Pamukkale and Ege University in the field of Electric Power Systems, Grounding and Protection.
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