This edition first published 2020
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Library of Congress Cataloging-in-Publication Data
Names: Huang, Qi, 1976- author.
Title: Magnetic field measurement with applications to modern power grids / Qi Huang (University of Electronic Science and Technology of China) [and three others].
Description: Hoboken, NJ :Wiley-IEEE Press, 2020. | Copyrighted by John Wiley & Sons, Ltd. | Includes bibliographical references and index. | Identifiers: LCCN 2019015135 (print) | LCCN 2019017754 (ebook) | ISBN 9781119494461 (Adobe PDF) | ISBN 9781119494508 (ePub) | ISBN 9781119494515 (hardcover)
Subjects: LCSH: Electromagnetic fields. | Electromagnetic fields–Industrial applications. | Electric fields–Measurement. | Magnetic fields–Measurement. | Electric power distribution.
Classification: LCC QC665.E4 (ebook) | LCC QC665.E4 M335 2019 (print) | DDC 621.31028/7 –dc23
LC record available at https://lccn.loc.gov/2019015135
Cover Design:Wiley
Cover Images: © alengo/Getty Images, © Yelantsevv/Getty Images
To our families
Most contemporary electrical engineering at a high level can be modelled by the Maxwell equations:
where B and D are the magnetic and displacement fields, respectively, E and H are the electric and magnetizing fields, and J and ρ are the current and electric charge densities. In the compact vector notation shown, the dot and cross notations refer to divergence and curl, respectively. A significant part of the physics of these fields is the magnetic field, B, which plays an especially important role in electric power engineering both contemporaneously and historically. Reference [1] gives a concise discussion of magnetic fields as described by Maxwell's equations and how these mathematical models have evolved. Perhaps the close nexus of magnetic fields and power engineering is due to the history of the development of motors and generators. Traditionally, these devices rely on the conversion of mechanical, electrical, and magnetic energy. These have been the ‘work horses’ of world industry, but the nexus goes beyond motors and generators: sensors, measurement instruments, controls, electromagnets of a wide variety, and energy converters of all types entail applications of the phenomenon of magnetism. As such, power engineers need to appreciate not only the theory of magnetism, but also the practicalities, i.e. how applications are realized in a modern contemporary setting. These practicalities include measurement. This book focuses on sensing and measurement of magnetic fields as commonly encountered in electric power engineering. However, the present book does not lose sight of the underpinnings of electromagnetic field theory, for example the use of the Poynting vector S,
to describe the interrelationship of E and H. How S describes the spatial motion of power is explained in some detail in Chapter 1.
The present book covers a range of topics on magnetic field measurement and applications in power engineering, from the history of this part of physics to actual measurement methods and commercial applications in instrumentation. Practical measurement is discussed in detail. Monitoring the utilization of magnetics and human health (e.g. electromagnetic field exposure) are also discussed because the standardization of limits of field strengths has taken on important international acceptance. That is, if a device cannot operate in the presence of a human being, it should not be considered operable at all. These standards are a necessary consequence of international commercialization. New topical areas have implications for the integration of renewable generation resources. This is a consequence of the importance of the sustainability of electric energy resources. Because power engineering is undergoing a transformation from a traditional science to a consumer oriented, efficient, highly controlled, commercial engineering venture (i.e. the ‘smart grid’), most topics in the book have a specialized focus on smart grid topics such as ‘big data’, renewable generation integration, smart sensory applications (especially at the secondary distribution consumer level, i.e. up to 1 kW), and enhancement of efficiency. Large‐scale system applications, especially system‐wide control, are included. The book has an emphasis on measurement techniques, and these might be classified as various forms of magnetoresistive techniques (e.g. anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), tunnel magnetoresistance (TMR), colossal magnetoresistance (CMR), and extraordinary magnetoresistance (EMR), methods suitable for transmission line current measurement, electro‐optical phenomena (e.g. the Faraday effect), and how instrumentation and measurement relate to the objectives of the smart grid. In many of these cases, shielding and noise have a significant impact and need specialized methods to render measurements accurate and usable. This is the case since magnetic field strengths less than 1 mTesla are usual in typical measurement applications. It is evident that measurements made some distance from high power equipment require significant sensitivity. This is especially true when a high level of resolution is needed so that low field strengths at high spectral frequencies can be detected. In electric power engineering, in view of the large number of solid state power converters in commercial use, the subject of harmonic voltages and currents has captured significant attention (e.g. ‘power quality engineering’). Some of these ‘harmonics’ are asynchronous to the ‘power frequency’ and this may make magnetic field and electric current measurements especially difficult. For example, the popularity of pulse width modulated (PWM) converters (even at levels above 1 MW) for energy flow control results in frequency spectra that contain linear combinations and multiples of both the power frequency and the PWM carrier switching frequency. These PWM spectral components may go well above 20 kHz. As a guide, one may expect that unipolar PWM converters cause frequency spectral components approximately of the order of kfs, where fs is the PWM carrier frequency and k = 2, 4, ….Recent advances in power electronic switches have resulted in applications above fs = 10 kHz. Reference [2] describes some of the mathematics involved. Power quality applications of magnetic field measurements are discussed in Chapter 5 of this book.
In this book, magnetic field measurements in substations, transmission systems, and distribution systems are considered in some detail separately. In this way, the specialized applications of magnetic field measurements in these venues can be discussed, including the detail of typical sensors used, the field strength levels and spectral frequencies involved, and the mathematics that are needed to process data measurements.
The book concludes with a very interesting outline of challenges, trends, and needs for future magnetic measurement systems. These are categorized again mainly by transmission, substation, and distribution applications. Included are remarks on the required levels of standardization, smart grid applications, and innovative sensors.
The general topic of electromagnetics often presents challenges to electrical engineering students because of the complexity of vector mathematics and the inability to easily ‘visualize’ electromagnetic fields. This book should be a significant help in education relating to magnetic fields, especially as a complement to a university course in power engineering. The technologies of measurement are a bridge between mathematical models and application‐oriented practice. The book should be a guide to that bridge.
Magnetism, an interaction among moving charges, is one of the oldest branches of science and is still under constant active study with great implications for modern industrial applications, especially energy and environment. Electric and magnetic phenomena have been recognized since ancient times, but the means to measure, generate, control, and use the phenomena to develop practical devices became adequately understood only in the past 200 years. In recent years, with progress in the material, electronic packaging, and other related circuit technologies, the applications of magnetics have evolved and are promising. Due to their non‐contact character, magnetics‐related applications have great potential in detection in some atrocious environments or where human access is difficult. Non‐contact and non‐intrusive detection technologies are finding more and more applications in many fields. Another potential application is wireless power transmission with magnetic effects, which will potentially revolutionize power utilization, for example wireless charging for electric vehicles and cell phones is already available.
Voltage and current are the fundamental parameters in an electric power system. It is known that the magnetic field is always associated with current, therefore magnetics‐related phenomena play an important role in power systems.
This book presents the most updated technological developments in magnetic‐field‐based measurement solutions in modern power systems under the smart grid environment. Smart grids are revolutionarily transforming the modern power grid. This initiative is one of most prevalent trends in power systems all over the world, becoming the national level strategic development plan in many countries. The aims of smart grids include improving efficiencies, increasing grid flexibility, and reducing power outages, as well as other market, consumer, and societal needs, such as integration of diverse generation and storage options, integration of electric vehicles, and competitive electricity pricing, etc. It is known that information and communication/control technology is the enabler for smart grids, therefore non‐contact magnetic‐field‐based measurement will provide many solutions for smart grids.
Although there is a wide range of applications for non‐contact measurement, this book mainly focuses on the research conducted in the authors' research laboratory. The concepts of magnetism and magnetic fields are reviewed and their potential applications in modern industry, especially in power systems, are discussed. Advanced magnetic sensor technology, principally magneto‐resistive sensors, is reviewed. In Chapters 3 to 6 the applications of magnetic‐field‐based measurement solutions are presented according to the electricity production chain, i.e. generation, transformation, transmission, and distribution. Magnetism is extremely useful for converting energy from one form to another. About 99% of the power generated from fossil fuels, nuclear and hydroelectric energy, and wind comes from systems that use magnetism in the conversion process, therefore magnetic‐field‐based solutions can find applications in any aspect of modern power grids. According to the development of modern electric power systems, potential applications for renewable energy generation are discussed. In addition, as electricity utilization increases in every aspect of daily life, people are becoming aware of the harmful effect of electromagnetic exposure, and this is discussed in the chapter on distribution. Finally, future visions are presented in Chapter 7.
The authors welcome all readers to discuss the book with us and contribute to this research field.
The authors are grateful to the many people who made this book possible.
Special thanks go to Mr Louis Manohar from Wiley. Without his encouragement and help, it would have been impossible to finish the writing of the book. The authors also appreciate the efforts of all professors and graduate students whoever worked in the authors' research lab. Most of the contents are from the research projects in our research lab. These personnel include Mr Youliang Lu, Mr Fuchao Li, Mr Xiaohua Wang, and many more who cannot be mentioned here for reasons of space.
Special thanks go to Mr Wei Zhen and the Sichuan Electric Power Research Institute, Sichuan Power Company, State Grid of China. Without their help and continuous funding support, we would not have been able to persist in the research of magnetic field measurement. There are many other research scientists and engineers who provide assistance during the 10 years of research. Dr Guiyun Tian's research group is collaborating with the authors to extend electromagnetic sensors to the field of electromagnetic measurement. Mr Yang Yang from No. 9 Research Institute of China Electronics Technology Group Corporation, also known as the Southwest Applied Magnetics Research Institute, helped on sensor manufacturing and advocating the concepts proposed in this book to industrial applications. A group of research engineers at Cheng Dian Da Wei Ltd are trying to transit the prototypes into market products. The authors would also like to acknowledge the collaboration of Professor Philip Pong, from the University of Hong Kong.
Thanks also go to the publishers for granting the permission for reprinting some of the authors' publications in this book.
Finally, it is our great honor that Dr G. T. Heydt, of the US National Engineering Academy, has written a high‐impact foreword for us, which will definitely contribute to the success of the book.