This book is intended for use by practicing power engineers and managers interested in the emerging field of power quality in electrical systems. We take a realworld point of view throughout with numerous examples compiled from the literature and the authors’ engineering experiences.
[...]... heat in motors, causing early failures Heat also builds up in wire insulation causing breakdown and failure Increased operating temperatures can affect other equipment as well, resulting in malfunctions and early failure In addition, harmonics on the power line can prompt computers to restart and adversely affect other sensitive analog circuits The reasons for the increased interest in power quality. .. to the effects of harmonics For instance, in electric motors, harmonic current causes AC losses in the core and copper windings.6 This can result in core heating, winding heating, torque pulsations, and loss of efficiency in these motors Harmonics can also result in an increase in audible noise from motors and transformers7 and can excite mechanical resonances in electric motors and their loads Harmonic... a brief increase in the rms line-voltage of 110 to 180 percent of the nominal line-voltage for a duration of 0.5 cycle to 1 minute Sources of voltage swells are line faults and incorrect tap settings in tap changers in substations ■ An impulsive transient is a brief, unidirectional variation in voltage, current, or both on a power line The most common causes of impulsive transients are lightning strikes,... waveform at 60 Hz with a line-line-voltage of 480 V rms Shown are the line-neutral voltages of each phase.2 Figure 1.2 distortion of the voltage in the supply system, which is an indication of poor power quality Nonlinear Load: The Rectifier The rectifier, for converting alternating current to direct current, is the most common nonlinear load found in electrical systems It is used in equipment that ranges... resulting from the placement and use in the described manner ALEXANDER KUSKO, SC.D., P.E MARC T THOMPSON, PH.D xi Copyright © 2007 by The McGraw-Hill Companies, Inc Click here for terms of use This page intentionally left blank Power Quality in Electrical Systems This page intentionally left blank Chapter 1 Introduction In this introductory chapter, we shall attempt to define the term “power quality, ”... signals involved Telephone transmission can be disrupted by EMI-induced noise This recent emphasis on the purity of delivered power has resulted in a new field of study—that of “power quality. ” The Definition of Power Quality Power quality, loosely defined, is the study of powering and grounding electronic systems so as to maintain the integrity of the power supplied to the system IEEE Standard 11598 defines... Metering: Poor power quality can affect the accuracy of utility metering ■ Protective relays: Poor power quality can cause protective relays to malfunction ■ Downtime: Poor power quality can result in equipment downtime and/or damage, resulting in a loss of productivity ■ Cost: Poor power quality can result in increased costs due to the preceding effects ■ Electromagnetic compatibility: Poor power quality. .. voltage, current, or both on a power line These can occur due to the switching of power factor correction capacitors, or transformer ferroresonance ■ An interruption is defined as a reduction in line-voltage or current to less than 10 percent of the nominal, not exceeding 60 seconds in length 9 Generally, it’s called a sag in the U.S and a dip in the UK 8 Chapter One Interruption Sag Swell Long duration... [1.63–1.64]? The bottom line is that the end user wants to see the noninterruption of good quality electrical service because the cost of downtime is high Shown in Table 1.1, we see a listing of possible mitigating strategies for poor power quality, and the relative costs of each The Scope of This Text We will address the significant aspects of power quality in the following chapters: Chapter 1, Introduction,... for the subject, including definitions, examples, and an outline for the book Chapter 2, Power Quality Standards, discusses various power -quality standards, such as those from the IEEE and other bodies Included are standards discussing harmonic distortion (frequencies that are multiples of the line frequency) as well as high-frequency interharmonics caused by switching power supplies, inverters, and . Thompson Consulting, Inc., an engineering consulting firm specializing in power electronics, magnetic design, and analog circuits and systems. He is also an adjunct professor of electrical engineering at. Analysis in Detail 205 Summary 213 References 213 Index 215 x Contents Preface This book is intended for use by practicing power engineers and man- agers interested in the emerging field of power quality. This page intentionally left blank Power Quality in Electrical Systems This page intentionally left blank Chapter 1 Introduction In this introductory chapter, we shall attempt to define the term