Short-Circuits in AC and DC Systems

ANSI, IEEE, and IEC Standards

J. C. Das

• Publisher: CRC Press
• Year: 2017
• Topic: Technology & Engineering
• eBook ISBN:
  9781351230766
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

This book provides an understanding of the nature of short-circuit currents, current interruption theories, circuit breaker types, calculations according to ANSI/IEEE and IEC standards, theoretical and practical basis of short-circuit current sources, and the rating structure of switching devices. The book aims to explain the nature of short-circuit currents, the symmetrical components for unsymmetrical faults, and matrix methods of solutions, which are invariably used on digital computers. It includes innovations, worked examples, case studies, and solved problems.

Preface to Volume 1: Short-Circuits in AC and DC Systems

The first three chapters of this volume—design and analyses concepts of power systems, modern electrical power systems, and wind and solar power generation—are of a general nature applicable to this series.

Short-circuit studies are the very first studies that are conducted for a power system. It is important to understand the nature of short-circuit currents, the symmetrical components for unsymmetrical faults, and matrix methods of solutions that are invariably used on digital computers. This material is covered in Chapters 4, 5, and 6. A long-hand calculation of unsymmetrical fault current even in a simple system in Chapter 5 shows the complexity of such calculations and paves the way for discussions of matrix methods in Chapter 6.

A description of the AC current interruption process is provided in Chapter 7. An understanding is important to appreciate the interruption of various types of short-circuit currents, overvoltages, TRV, restrikes, and multiple reignitions in circuit breakers. This is followed by Chapter 8, which details the rating structures of circuit breakers and fuses according to ANSI/IEEE standards. The major short-circuit contributing sources are synchronous generators and rotating motors. Their models are developed using Park’s transformation and circuits of a unit machine followed by their behavior on short circuit and the resulting decaying transients.

Chapters 10 and 11 detail the methodology of short-circuit calculations using ANSI/IEEE and IEC standards. There are conceptual and analytical differences in the calculations illustrated with real-world examples. Chapter 12 is devoted to the short-circuit currents in DC systems.

This book, therefore, provides an understanding of the nature of short-circuit currents, current interruption theories, circuit breaker types, calculations according to ANSI/IEEE and IEC standards, theoretical and practical basis of short-circuit current sources, the rating structure of switching devices, and the short-circuit currents in DC systems. This volume covers a wide base of short-circuit current in the power systems and can be considered a treatize on this subject of practical and academic value.

—J.C. Das

Author

J.C. Das is an independent consultant, Power System Studies, Inc. Snellville, Georgia. Earlier, he headed the electrical power systems department at AMEC Foster Wheeler for 30 years. He has varied experience in the utility industry, industrial establishments, hydroelectric generation, and atomic energy. He is responsible for power system studies, including short circuit, load flow, harmonics, stability, arc flash hazard, grounding, switching transients, and protective relaying. He conducts courses for continuing education in power systems and is the author or coauthor of about 70 technical publications nationally and internationally. He is the author of the following books:

• Arc Flash Hazard Analysis and Mitigation, IEEE Press, 2012.
• Power System Harmonics and Passive Filter Designs, IEEE Press, 2015.
• Transients in Electrical Systems: Analysis Recognition and Mitigation, McGraw-Hill, 2010.
• Power System Analysis: Short-Circuit Load Flow and Harmonics, Second Edition, CRC Press 2011.
• Understanding Symmetrical Components for Power System Modeling, IEEE Press, 2017.

These books provide extensive converge, running into more than 3000 pages, and are well received in the technical circles. His interests include power system transients, EMTP simulations, harmonics, passive filter designs, power quality, protection, and relaying. He has published more than 200 electrical power system study reports for his clients.

He has published more than 200 study reports of power systems analysis addressing one problem or the other.

Das is a Life Fellow of the Institute of Electrical and Electronics Engineers, IEEE, (USA), Member of the IEEE Industry Applications and IEEE Power Engineering societies, a Fellow of the Institution of Engineering Technology (UK), a Life Fellow of the Institution of Engineers (India), a Member of the Federation of European Engineers (France), a Member of CIGRE (France), etc. He is registered Professional Engineer in the states of Georgia and Oklahoma, a Chartered Engineer (CEng) in the UK, and a European Engineer (EurIng) in Europe. He received a meritorious award in engineering, IEEE Pulp and Paper Industry in 2005.

He earned a PhD in electrical engineering at Atlantic International University, Honolulu, an MSEE at Tulsa University, Tulsa, Oklahoma, and a BA in advanced mathematics and a BEE at Panjab University, India.

1 Design and Analyses Concepts of Power Systems

Electrical power systems are the most complex man-made nonlinear systems on earth. Also these are highly dynamic in nature. Consider that the circuit breakers are closing and opening, the generation is varying according to load demand, and the power systems are subjected to disturbances of atmospheric origin and switching operations. The energy state of the power systems is constantly changing and the energy is being redistributed into electromagnetic and mechanical systems.

Yet, we study electrical power systems in the steady state; though, it may last for a short duration. The transition from one steady state to another does not take place instantaneously and transition to each steady state should be acceptable and stable.

The study of power systems in steady-state amounts to taking a still picture of continuously varying natural phenomena like sea waves. The study of transients that lead from one steady state to another requires transient analysis. The four volumes of this series present steady-state analysis of power systems for the material covered in these volumes. However, the transient analysis is presented as required. There cannot be a water tight compartment between the steady state and the transient state—one may lead to another. For example, short circuits in AC systems are decaying transients and subject the power system to severe stresses and stability problems, yet empirical calculations as per standards are applied for their calculations.

However, this series does not provide an insight into the transient behavior of the power systems and confines the analyses mostly to steady state. Some sporadic reference to transients may be seen in some chapters and appendices of the book. A section on effect of protective relaying on stability and fundamental concepts of power system stability are included in Volume 4.

The time duration (frequency) of the transient...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Power Analysis Handbook
• Series Preface
• Preface to Volume 1: Short-Circuits in AC and DC Systems
• Author
• 1. Design and Analyses Concepts of Power Systems
• 2. Modern Electrical Power Systems
• 3. Wind and Solar Power Generation and Interconnections with Utility
• 4. Short-Circuit Currents and Symmetrical Components
• 5. Unsymmetrical Fault Calculations
• 6. Matrix Methods for Network Solutions
• 7. Current Interruptions in AC Networks
• 8. Application and Ratings of Circuit Breakers and Fuses according to ANSI Standards
• 9. Short Circuit of Synchronous and Induction Machines and Converters
• 10. Short-Circuit Calculations according to ANSI Standards
• 11. Short-Circuit Calculations according to IEC Standards
• 12. Calculations of Short-Circuit Currents in Direct Current Systems
• Appendix A: Matrix Methods
• Appendix B: Sparsity and Optimal Ordering
• Appendix C: Transformers and Reactors
• Appendix D: Solution to the Problems
• Index