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ELECTRIC
POWER
TR ANSFORMER
ENGINEERING
© 2004 by CRC Press LLC
© 2004 by CRC Press LLC
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International Standard Book Number 0-8493-1704-5
Library of Congress Card Number 2003046134
Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
Printed on acid-free paper
Library of Congress Cataloging-in-Publication Data
Electric power transformer engineering / edited by James H. Harlow.
p. cm. — (The Electric Power Engineering Series ; 9)
Includes bibliographical references and index.
ISBN 0-8493-1704-5 (alk. paper)
1. Electric transformers. I. Harlow, James H. II. title. III. Series.
TK2551.E65 2004
621.31d4—dc21 2003046134
© 2004 by CRC Press LLC
Preface
Transformer engineering is one of the earliest sciences within the field of electric power engineering, and
power is the earliest discipline within the field of electrical engineering. To some, this means that
transformer technology is a fully mature and staid industry, with little opportunity for innovation or
ingenuity by those practicing in the field.
Of course, we in the industry find that premise to be erroneous. One need only scan the technical
literature to recognize that leading-edge suppliers, users, and academics involved with power transformers
are continually reporting novelties and advancements that would have been totally insensible to engineers
of even the recent past. I contend that there are three basic levels of understanding, any of which may
be appropriate for persons engaged with transformers in the electric power industry. Depending on day-
to-day involvement, the individual’s posture in the field can be described as:
• Curious — those with only peripheral involvement with transformers, or a nonprofessional lacking
relevant academic background or any particular need to delve into the intricacies of the science
• Professional — an engineer or senior-level technical person who has made a career around electric
power transformers, probably including other heavy electric-power apparatus and the associated
power-system transmission and distribution operations
• Expert — those highly trained in the field (either practically or analytically) to the extent that
they are recognized in the industry as experts. These are the people who are studying and pub-
lishing the innovations that continue to prove that the field is nowhere near reaching a techno-
logical culmination.
So, to whom is this book directed? It will truly be of use to any of those described in the previous
three categories.
The
curious person will find the material needed to advance toward the level of professional. This
reader can use the book to obtain a deeper understanding of many topics.
The
professional, deeply involved with the overall subject matter of this book, may smugly grin with
the self-satisfying attitude of, “I know all that!” This person, like myself, must recognize that there are
many transformer topics. There is always room to learn. We believe that this book can also be a valuable
resource to professionals.
The
expert may be so immersed in one or a few very narrow specialties within the field that he also
may benefit greatly from the knowledge imparted in the peripheral specialties.
The book is divided into three fundamental groupings: The first stand-alone chapter is devoted to
Theory and Principles. The second chapter, Equipment Types, contains nine sections that individually treat
major transformer types. The third chapter, which contains 14 sections, addresses Ancillary Topics asso-
ciated with power transformers. Anyone with an interest in transformers will find a great deal of useful
information.
© 2004 by CRC Press LLC
I wish to recognize the interest of CRC Press and the personnel who have encouraged and supported
the preparation of this book. Most notable in this regard are Nora Konopka, Helena Redshaw, and
Gail Renard. I also want to acknowledge Professor Leo Grigsby of Auburn University for selecting me to
edit the “Transformer” portion of his The Electric Power Engineering Handbook (CRC Press, 2001), which
forms the basis of this handbook. Indeed, this handbook is derived from that earlier work, with the
addition of four wholly new chapters and the very significant expansion and updating of much of the
other earlier work. But most of all, appreciation is extended to each writer of the 24 sections that
comprise this handbook. The authors’ diligence, devotion, and expertise will be evident to the reader.
James H. Harlow
Editor
© 2004 by CRC Press LLC
Editor
James H. Harlow has been self-employed as a principal of Harlow Engineering Associates, consulting to
the electric power industry, since 1996. Before that, he had 34 years of industry experience with Siemens
Energy and Automation (and its predecessor Allis-Chalmers Co.) and Beckwith Electric Co., where he
was engaged in engineering design and management. While at these firms, he managed groundbreaking
projects that blended electronics into power transformer applications. Two such projects (employing
microprocessors) led to the introduction of the first intelligent-electronic-device control product used
in quantity in utility substations and a power-thyristor application for load tap changing in a step-voltage
regulator.
Harlow received the BSEE degree from Lafayette College, an MBA (statistics) from Jacksonville State
University, and an MS (electric power) from Mississippi State University. He joined the PES Transformers
Committee in 1982, serving as chair of a working group and a subcommittee before becoming an officer
and assuming the chairmanship of the PES Transformers Committee for 1994–95. During this period,
he served on the IEEE delegation to the ANSI C57 Main Committee (Transformers). His continued
service to IEEE led to a position as chair of the PES Technical Council, the assemblage of leaders of the
17 technical committees that comprise the IEEE Power Engineering Society. He recently completed a
2-year term as PES vice president of technical activities.
Harlow has authored more than 30 technical articles and papers, most recently serving as editor of
the transformer section of
The Electric Power Engineering Handbook, CRC Press, 2001. His editorial
contribution within this handbook includes the section on his specialty, LTC Control and Transformer
Paralleling. A holder of five U.S. patents, Harlow is a registered professional engineer and a senior member
of IEEE.
© 2004 by CRC Press LLC
Contributors
Dennis Allan
MerlinDesign
Stafford, England
Hector J. Altuve
Schweitzer Engineering
Laboratories, Ltd.
Monterrey, Mexico
Gabriel Benmouyal
Schweitzer Engineering
Laboratories, Ltd.
Longueuil, Quebec, Canada
Behdad Biglar
Trench Ltd.
Scarborough, Ontario,
Canada
Wallace Binder
WBBinder
Consultant
New Castle, Pennsylvania
Antonio Castanheira
Trench Brasil Ltda.
Contegem, Minas Gelais, Brazil
Craig A. Colopy
Cooper Power Systems
Waukesha, Wisconsin
Robert C. Degeneff
Rensselaer Polytechnic Institute
Troy, New York
Scott H. Digby
Waukesha Electric Systems
Goldsboro, North Carolina
Dieter Dohnal
Maschinenfabrik Reinhausen
GmbH
Regensburg, Germany
Douglas Dorr
EPRI PEAC Corporation
Knoxville, Tennessee
Richard F. Dudley
Trench Ltd.
Scarborough, Ontario, Canada
Ralph Ferraro
Ferraro, Oliver & Associates, Inc.
Knoxville, Tennessee
Dudley L. Galloway
Galloway Transformer
Technology LLC
Jefferson City, Missouri
Anish Gaikwad
EPRI PEAC Corporation
Knoxville, Tennessee
Armando Guzmán
Schweitzer Engineering
Laboratories, Ltd.
Pullman, Washington
James H. Harlow
Harlow Engineering Associates
Mentone, Alabama
Ted Haupert
TJ/H2b Analytical Services
Sacramento, California
William R. Henning
Waukesha Electric Systems
Waukesha, Wisconsin
Philip J. Hopkinson
HVOLT, Inc.
Charlotte, North Carolina
Sheldon P. Kennedy
Niagara Transformer
Corporation
Buffalo, New York
Andre Lux
KEMA T&D Consulting
Raleigh, North Carolina
Arindam Maitra
EPRI PEAC Corporation
Knoxville, Tennessee
Arshad Mansoor
EPRI PEAC Corporation
Knoxville, Tennessee
© 2004 by CRC Press LLC
Shirish P. Mehta
Waukesha Electric Systems
Waukesha, Wisconsin
Harold Moore
H. Moore & Associates
Niceville, Florida
Dan Mulkey
Pacific Gas & Electric Co.
Petaluma, California
Randy Mullikin
Kuhlman Electric Corp.
Versailles, Kentucky
Alan Oswalt
Consultant
Big Bend, Wisconsin
Paulette A. Payne
Potomac Electric Power
Company (PEPCO)
Washington, DC
Dan D. Perco
Perco Transformer Engineering
Stoney Creek, Ontario, Canada
Gustav Preininger
Consultant
Graz, Austria
Jeewan Puri
Transformer Solutions
Matthews, North Carolina
Leo J. Savio
ADAPT Corporation
Kennett Square, Pennsylvania
Michael Sharp
Trench Ltd.
Scarborough, Ontario, Canada
H. Jin Sim
Waukesha Electric Systems
Goldsboro, North Carolina
Robert F. Tillman, Jr.
Alabama Power Company
Birmingham, Alabama
Loren B. Wagenaar
America Electric Power
Pickerington, Ohio
© 2004 by CRC Press LLC
Contents
Chapter 1 Theory and Principles Dennis Allan and Harold Moore
Chapter 2 Equipment Types
2.1 Power Transformers H. Jin Sim and Scott H. Digby
2.2 Distribution Transformers Dudley L. Galloway and Dan Mulkey
2.3Phase-Shifting Transformers Gustav Preininger
2.4 Rectifier Transformers Sheldon P. Kennedy
2.5Dry-Type Transformers Paulette A. Payne
2.6 Instrument Transformers Randy Mullikin
2.7Step-Voltage Regulators Craig A. Colopy
2.8 Constant-Voltage Transformers Arindam Maitra, Anish Gaikwad,
Ralph Ferraro, Douglas Dorr, and Arshad Mansoor
2.9Reactors Richard F. Dudley, Michael Sharp, Antonio Castanheira,
and Behdad Biglar
Chapter 3
Ancillary Topics
3.1 Insulating Media Leo J. Savio and Ted Haupert
3.2Electrical Bushings Loren B. Wagenaar
3.3Load Tap Changers Dieter Dohnal
3.4Loading and Thermal Performance Robert F. Tillman, Jr.
3.5Transformer Connections Dan D. Perco
3.6Transformer Testing Shirish P. Mehta and William R. Henning
3.7 Load-Tap-Change Control and Transformer Paralleling
James H. Harlow
3.8Power Transformer Protection Armando Guzmán, Hector J. Altuve,
and Gabriel Benmouyal
3.9 Causes and Effects of Transformer Sound Levels Jeewan Puri
3.10Transient-Voltage ResponseRobert C. Degeneff
3.11 Transformer Installation and MaintenanceAlan Oswalt
3.12Problem and Failure Investigation Wallace Binder
and Harold Moore
3.13On-Line Monitoring of Liquid-Immersed Transformers Andre Lux
3.14U.S. Power Transformer Equipment Standards and Processes
Philip J. Hopkinson
© 2004 by CRC Press LLC
1
Theory and Principles
1.1Air Core Transformer
1.2Iron or Steel Core Transformer
1.3Equivalent Circuit of an Iron-Core Transformer
1.4The Practical Transformer
Magnetic Circuit • Leakage Reactance • Load Losses • Short-
Circuit Forces • Thermal Considerations • Voltage
Considerations
References
Transformers are devices that transfer energy from one circuit to another by means of a common magnetic
field. In all cases except autotransformers, there is no direct electrical connection from one circuit to the
other.
When an alternating current flows in a conductor, a magnetic field exists around the conductor,
asillustrated in Figure 1.1. If another conductor is placed in the field created by the first conductor such
that the flux lines link the second conductor, as shown in Figure 1.2, then a voltage is induced into the
secondconductor. The use of a magnetic field from one coil to induce a voltage into a second coil is the
principle on which transformer theory and application is based.
1.1Air Core Transformer
Some small transformers for low-power applications are constructed with air between the two coils. Such
transformers are inefficient because the percentage of the flux from the first coil that links the second
coil is small. The voltage induced in the second coil is determined as follows.
E = N d
J/dt 10
8
(1.1)
where N is the number of turns in the coil, dJ/dt is the time rate of change of fluxlinking the coil, and J
is the flux in lines.
Ata time when the applied voltage to the coil is E and the flux linking the coils is
Jlines, the
instantaneous voltage of the supply is:
e = 2 E cos [t = N dJ/dt 10
8
(1.2)
dJ/dt = (2 cos [t 10
8
)/N(1.3)
The maximum value of Jis given by:
J= (2 E 10
8
)/(2TfN)(1.4)
Using the MKS (metric) system, where Jis the flux in webers,
Dennis Allan
MerlinDesign
Harold Moore
H. Moore and Associates
© 2004 by CRC Press LLC
[...]... & Electric Company Consultant 2.3 Niagara Transformer Corporation 2.4 Randy Mullikin Kuhlman Electric Corp Craig A Colopy Cooper Power Systems 2.5 2.6 Trench Ltd © 2004 by CRC Press LLC Instrument Transformers Overview • Transformer Basics • Voltage Transformer • Current Transformer Ferraro, Oliver & Associates Richard F Dudley Michael Sharp Antonio Castanheira Behdad Biglar Dry-Type Transformers Transformer. .. De-Q’ing • Sound Level and Mitigation 2.1 Power Transformers H Jin Sim and Scott H Digby 2.1.1 Introduction ANSI/IEEE defines a transformer as a static electrical device, involving no continuously moving parts, used in electric power systems to transfer power between circuits through the use of electromagnetic induction The term power transformer is used to refer to those transformers used between the generator... Phase-Shifting Transformers • Details of Transformer Design • Details of OnLoad Tap-Changer Application • Other Aspects Sheldon P Kennedy Paulette A Payne Distribution Transformers Historical Background • Construction • General Transformer Design • Transformer Connections • Operational Concerns • Transformer Locations • Underground Distribution Transformers • Pad-Mounted Distribution Transformers • Transformer. .. the transformer rating may have a slightly different meaning Based on some standards, the kVA rating can refer to the power that can be input to a transformer, the rated output being equal to the input minus the transformer losses Power transformers have been loosely grouped into three market segments based on size ranges These three segments are: 1 Small power transformers: 500 to 7500 kVA 2 Medium power. .. Transformer Losses • Transformer Performance Model • Transformer Loading • Transformer Testing • Transformer Protection • Economic Application Dudley L Galloway Gustav Preininger Power Transformers 2.7 Step-Voltage Regulators Introduction • Power Systems Applications • Ratings • Theory • Auto-Booster • Three-Phase Regulators • Regulator Control • Unique Applications 2.8 Constant-Voltage Transformers Background... apparent the larger the unit Power transformers are available for step-up operation, primarily used at the generator and referred to as generator step-up (GSU) transformers, and for step-down operation, mainly used to feed distribution circuits Power transformers are available as single-phase or three-phase apparatus The construction of a transformer depends upon the application Transformers intended for... power transformers: 7500 to 100 MVA 3 Large power transformers: 100 MVA and above Note that the upper range of small power and the lower range of medium power can vary between 2,500 and 10,000 kVA throughout the industry It was noted that the transformer rating is based on “usual” service conditions, as prescribed by standards Unusual service conditions may be identified by those specifying a transformer. .. liquid immersed For outdoor use, transformers are usually liquid immersed This section focuses on the outdoor, liquid-immersed transformers, such as those shown in Figure 2.1.1 FIGURE 2.1.1 20 MVA, 161:26.4 © 2004 by CRC Press LLC 13.2 kV with LTC, three phase transformers 2.1.2 Rating and Classifications 2.1.2.1 Rating In the U.S., transformers are rated based on the power output they are capable of... above Power systems typically consist of a large number of generation locations, distribution points, and interconnections within the system or with nearby systems, such as a neighboring utility The complexity of the system leads to a variety of transmission and distribution voltages Power transformers must be used at each of these points where there is a transition between voltage levels Power transformers... Harmonic Currents on Transformers • Thermal Tests • Harmonic Cancellation • DC Current Content • Transformers Energized from a Converter/Inverter • Electrostatic Ground Shield • Load Conditions • Interphase Transformers PEPCO Arindam Maitra Anish Gaikwad Arshad Mansoor Douglas Dorr Phase-Shifting Transformers Introduction • Basic Principle of Application • Load Diagram of a PST • Total Power Transfer • . Cataloging-in-Publication Data
Electric power transformer engineering / edited by James H. Harlow.
p. cm. — (The Electric Power Engineering Series ; 9)
Includes. LLC
Preface
Transformer engineering is one of the earliest sciences within the field of electric power engineering, and
power is the earliest discipline within the field of electrical
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