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Short Circuits in Power Systems

A Practical Guide to IEC 60909-0


Ismail Kasikci


Second Edition





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This book is the result of many years of professional activity in the area of power supply, teaching at the VDE, as well as at the Technical Academy in Esslingen. Every planner of electrical systems is obligated today to calculate the single-pole or three-pole short-circuit current before and after the project management phase. IEC 60909-0 is internationally recognized and used. This standard will be discussed in this book on the basis of fundamental principles and technical references, thus permitting a summary of the standard in the simplest and most understandable way possible. The rapid development in all areas of technology is also reflected in the improvement and elaboration of the regulations, in particular in regard to IEC 60909-0. Every system installed must not only be suitable for normal operation, but must also be designed in consideration of fault conditions and must remain undamaged following operation under normal conditions and also following a fault condition. Electrical systems must therefore be designed so that neither persons nor equipment are endangered. The dimensioning, cost effectiveness, and safety of these systems depend to a great extent on being able to control short-circuit currents. With increasing power of the installation, the importance of calculating short-circuit currents has also increased accordingly. Short-circuit current calculation is a prerequisite for the correct dimensioning of operational electrical equipment, controlling protective measures and stability against short circuits in the selection of equipment. Solutions to the problems of selectivity, back-up protection, protective equipment, and voltage drops in electrical systems will not be dealt with in this book. The reduction factors, such as frequency, temperatures other than the normal operating temperature, type of wiring, and the resulting current carrying capacity of conductors and cables will also not be dealt with here.

This book comprises the following sections:

Chapter 1 describes the most important terms and definitions, together with relevant processes and types of short circuits.

Chapter 2 is an overview of the fault current analysis.

Chapter 3 explains the significance, purpose, and creation of IEC 60909-0.

Chapter 4 deals with the network design of supply networks.

Chapter 5 gives an overview of the network types for low, medium and high- voltage network.

Chapter 6 describes the systems (network types) in the low-voltage network (IEC 60364) with the cut-off conditions.

Chapter 7 illustrates the types of neutral point treatment in three-phase networks.

Chapter 8 discusses the impedances of the three-phase operational equipment along with relevant data, tables, diagrams, and characteristic curves.

Chapter 9 presents the impedance corrections for generators, power substation transformers, and distribution transformers.

Chapter 10 is concerned with the power system analysis and the method of symmetrical components. With the exception of the three-pole short-circuit current, all other fault currents are unsymmetrical. The calculation of these currents is not possible in the positive-sequence system. The method of symmetrical components is therefore described here.

Chapter 11 is devoted to the calculation of short-circuit types.

Chapter 12 discusses the contribution of high-voltage and low-voltage motors to the short-circuit current.

Chapter 13 deals with the subject of mechanical and thermal stresses in operational equipment as a result of short-circuit currents.

Chapter 14 gives an overview of the design values for short-circuit current strength.

Chapter 15 is devoted to the most important overcurrent protection devices, with time–current characteristics.

Chapter 16 gives a brief overview of the procedure for calculating short-circuit currents in DC systems.

Chapter 17 gives an introduction into power flow analysis.

Chapter 18 represents a large number of examples taken from practice which enhance the understanding of the theoretical foundations. A large number of diagrams and tables that are required for the calculation simplify the application of the IEC 60909 standard as well as the calculation of short-circuit currents and therefore shorten the time necessary to carry out the planning of electrical systems.

I am especially indebted to Dr.-Ing. Waltraud Wüst, Dr. Martin Preuss from Wiley-VCH and Kishore Sivakolundu from SPI for critically reviewing the manuscript and for valuable suggestions.

At this point, I would also like to express my gratitude to all those colleagues who supported me with their ideas, criticism, suggestions, and corrections. My heartiest appreciation is due to Wiley Press for the excellent cooperation and their support in the publication of this book.

Furthermore, I welcome every suggestion, criticism, and idea regarding the use of this book from those who read the book.

Finally, without the support of my family this book could never have been written. In recognition of all the weekends and evenings I sat at the computer, I dedicate this book to my family.

Ismail Kasikci



I would like to thank the companies Siemens and ABB for their help with figures, pictures, and technical documentation. In particular, as a member, I am also indebted to the VDE (Association for Electrical, Electronic and Information Technologies) for their support and release of different kinds of tables and data.

Additionally, I would like to thank Wiley for publishing this book and especially Dr.-Ing. Waltraud Wüst, Dr. Martin Preuss from Wiley-VCH and Kishore Sivakolundu from SPI for their assistance in supporting me and checking the book for clarity.

Finally, I appreciate the designers and planners for their feedbacks, the students for their useful recommendations, and the critics.