Short-Circuits in AC and DC Systems ANSI, IEEE, and IEC Standards Volume 1 by J.C. Das

8. Application and Ratings of Circuit Breakers and Fuses according to ANSI

Standards

9. Short Circuit of Synchronous and Induction Machines

and Converters

This handbook on power systems consists of four volumes. These are carefully planned and designed to provide state-of-the-art material on the major aspects of electrical power systems, short-circuit currents, load flow, harmonics, and protective relaying. An effort has been made to provide a comprehensive coverage, with practical applications, case studies, examples, problems, extensive references, and 

bibliography.

The material is organized with sound theoretical base and its practical applications. The objective of creating this series is to provide the reader with a comprehensive treatise that could serve as a reference and day-to-day application guide for solving the real-world problem. It is written for plasticizing engineers and academia at the level of upperundergraduate and graduate degrees.

Though there are published texts on similar subjects, this series provides a unique approach to the practical problems that an application engineer or consultant may face in conducting system studies and applying it to varied system problems. Some parts of the work are fairly advanced on a postgraduate level and get into higher mathematics. Yet the continuity of the thought process and basic conceptual base are maintained. A beginner and advanced reader will equally benefit from the material covered. An underground level of education is assumed, with a fundamental knowledge of electrical circuit theory, rotating machines, and matrices.

Currently, power systems, large or small, are analyzed on digital computers with appropriate software. However, it is necessary to understand the theory and basis of these calculations to debug and decipher the results. A reader may be interested only in one aspect of power systems and may choose to purchase only one of the volumes. Many aspects of power systems are transparent between different types of studies and analyses—for example, knowledge of short-circuit currents and symmetrical component is required for protective relaying and fundamental frequency load flow is required for harmonic analysis. Though appropriate references are provided, the material is not repeated from one volume to another.

The series is a culmination of the vast experience of the author in solving real-world problems in the industrial and utility power systems for more than 40 years. Another key point is that the solutions to the problems are provided in Appendix D. Readers should be able to independently solve these problems after perusing the contents of a chapter and then look back to the solutions provided as a secondary help. The problems are organized so these can be solved with manual manipulations, without the help of any digital computer power system software.

It is hoped the series will be a welcome addition to the current technical literature.

The author thanks CRC Press editor Nora Konopka for her help and cooperation throughout the publication effort.

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.