ELECTRIC POWER SYSTEMS

xivPREFACEincluding reactive power, I had seen. That manual proved to me that it is possible towrite about electric power systems in a way that is accessible to audiences who havenot undergone the initiation rites of electrical engineering, but who neverthelesswant to get the real story. This experience suggested there might be other peoplemuch like myself—outside the power industry, but vitally concerned with it—who could benefit from such a practical approach.After finishing my dissertation in 1995, I decided to give it a try: My goal was towrite the book that I would have liked to read as a student six or seven years earlier.Considering that it has taken almost a decade to achieve, this turned out to be a muchmore ambitious undertaking than I imagined at the outset. A guiding principlethroughout my writing process was to assume a minimum of prior knowledgeon the part of the readers while trying to relate as much as possible to their directexperience, thus building a conceptual and intuitive understanding from theground up. I hope the book will serve as a useful reference, and perhaps even as asource of further inspiration for others to study the rich and complex subject ofelectric power.I envision two main audiences for this book. The first consists of students andresearchers who are learning about electric circuits and power system engineeringin an academic setting, and who feel that their understanding would be enhancedby a qualitative, conceptual emphasis to complement the quantitative methodsstressed in technical courses. This audience might include students of diverse backgrounds or differing levels of preparation, perhaps transferring into an engineeringprogram from other disciplines. Such students often need to solidify theirunderstanding of basic information presumed to be second nature for advancedundergraduates in technical fields. As a supplement to standard engineering texts,this volume aims to provide a clear and accessible review of units, definitions,and fundamental physical principles; to explain in words some of the ideas conventionally shown by equations; to contextualize information, showing connectionsamong different topics and pointing out their relevance; and to offer a glimpseinto the practical world of the electric power industry.The second major audience consists of professionals working in and around thepower industry whose educational background may not be in electrical engineering,but who wish to become more familiar with the technical details and the theoreticalunderpinnings of the system they deal with. This group might include analystsand administrators and managers coming from the fields of business, economics,law, or public policy, as well as individuals with technical or multidisciplinarytraining in areas other than power engineering. In view of the scope and importanceof contemporary policy decisions about electricity supply and delivery, both in theUnited States and abroad—from the siting of power generation and transmissionfacilities to market regulation and restructuring—a real need appears for a coherent,general education on the subject of power systems. My hope is that this volume canmake a meaningful contribution.

&ACKNOWLEDGMENTSMany individuals and organizations have made the writing of this text possible. I amdeeply grateful to my teachers for their mentorship, inspiration, and clarity, mostespecially Gene Rochlin, Felix Wu, and Oscar Ichazo. I am also indebted to themany professionals who took the time to show me around power systems inthe field and teach me about their work. The project was supported directly andindirectly by a University of California President’s Postdoctoral Fellowship,the University of California Energy Institute (UCEI), the California EnergyCommission’s Public Interest Energy Research (PIER) program, and the CaliforniaInstitute for Energy Efficiency (CIEE). I especially thank Carl Blumstein, SeverinBorenstein, Ron Hofmann, Laurie ten Hope, and Gaymond Yee for their encouragement at various stages in the process of writing this book.I also thank all my colleagues who graciously read, discussed, and helpedimprove portions of the draft manuscript. They include Raquel Blanco, AlexFarrell, Hannah Friedman, John Galloway, Chris Greacen, Sean Greenwalt,Dianne Hawk, Nicole Hopper, Merrill Jones, Chris Marnay, Andrew McAllister,Alex McEachern, Steve Shoptaugh, Kurt von Meier, and Jim Williams. Mygratitude also extends to all others who participated in the development of thetext—particularly my students who never cease to ask insightful and challengingquestions—and to my friends and family who offered encouragement andsupport. Darcy McCormick, Thomas Harris, and Steve Shoptaugh helped prepareillustrations, Cary Berkley organized the manuscript, and Trumbull Rogersimproved it by careful editing. Of course, I am solely responsible for any errors.As an endeavor that has not, to my knowledge, been attempted before, this textis necessarily a work in progress. Suggestions from readers for improving itsaccuracy and clarity will be warmly welcomed.ALEXANDRA VON MEIERSebastopol, CaliforniaAugust 2005xv

&CHAPTER 1The Physics of Electricity1.11.1.1BASIC QUANTITIESIntroductionThis chapter describes the quantities that are essential to our understanding of electricity: charge, voltage, current, resistance, and electric and magnetic fields. Moststudents of science and engineering find it very hard to gain an intuitive appreciationof these quantities, since they are not part of the way we normally see and makesense of the world around us. Electrical phenomena have a certain mystique thatderives from the difficulty of associating them with our direct experience, but alsofrom the knowledge that they embody a potent, fundamental force of nature.Electric charge is one of the basic dimensions of physical measurement, alongwith mass, distance, time and temperature. All other units in physics can beexpressed as some combination of these five terms. Unlike the other four,however, charge is more remote from our sensory perception. While we caneasily visualize the size of an object, imagine its weight, or anticipate the durationof a process, it is difficult to conceive of “charge” as a tangible phenomenon.To be sure, electrical processes are vital to our bodies, from cell metabolism tonervous impulses, but we do not usually conceptualize these in terms of electricalquantities or forces. Our most direct and obvious experience of electricity is toreceive an electric shock. Here the presence of charge sends such a strong waveof nervous impulses through our body that it produces a distinct and unique sensation. Other firsthand encounters with electricity include hair that defiantlystands on end, a zap from a door knob, and static cling in the laundry. Yet theseexperiences hardly translate into the context of electric power, where we canwitness the effects of electricity, such as a glowing light bulb or a rotating motor,while the essential happenings take place silently and concealed within pieces ofmetal. For the most part, then, electricity remains an abstraction to us, and werely on numerical and geometric representations—aided by liberal analogies fromother areas of the physical world—to form concepts and develop an intuitionabout it.Electric Power Systems: A Conceptual Introduction, by Alexandra von MeierCopyright # 2006 John Wiley & Sons, Inc.1

21.1.2THE PHYSICS OF ELECTRICITYChargeIt was a major scientific accomplishment to integrate an understanding of electricitywith fundamental concepts about the microscopic nature of matter. Observations ofstatic electricity like those mentioned earlier were elegantly explained by BenjaminFranklin in the late 1700s as follows: There exist in nature two types of a propertycalled charge, arbitrarily labeled “positive” and “negative.” Opposite charges attracteach other, while like charges repel. When certain materials rub together, one type ofcharge can be transferred by friction and “charge up” objects that subsequently repelobjects of the same kind (hair), or attract objects of a different kind (polyester andcotton, for instance).Through a host of ingenious experiments,1 scientists arrived at a model of theatom as being composed of smaller individual particles with opposite charges,held together by their electrical attraction. Specifically, the nucleus of an atom,which constitutes the vast majority of its mass, contains protons with a positivecharge, and is enshrouded by electrons with a negative charge. The nucleus also contains neutrons, which resemble protons, except they have no charge. The electricattraction between protons and electrons just balances the electrons’ natural tendency to escape, which results from both their rapid movement, or kinetic energy,and their mutual electric repulsion. (The repulsion among protons in the nucleusis overcome by another type of force called the strong nuclear interaction, whichonly acts over very short distances.)This model explains both why most materials exhibit no obvious electrical properties, and how they can become “charged” under certain circumstances: The opposite charges carried by electrons and protons are equivalent in magnitude, and whenelectrons and protons are present in equal numbers (as they are in a normal atom),these charges “cancel” each other in terms of their effect on their environment. Thus,from the outside, the entire atom appears as if it had no charge whatsoever; it iselectrically neutral.Yet individual electrons can sometimes escape from their atoms and travel elsewhere. Friction, for instance, can cause electrons to be transferred from one materialinto another. As a result, the material with excess electrons becomes negativelycharged, and the material with a deficit of electrons becomes positively charged(since the positive charge of its protons is no longer compensated). The ability ofelectrons to

electrical engineering majors. The second category had the information I needed, but was guarded by a layer of impenetrable phasor diagrams and other symbolism that obviously required a special sort of initiation. I was extremely fortunate to have access to some of the most highly respected