《变压器工程：设计和实践》.pdf

TransformerEngineeringCopyright 2004 by Marcel Dekker,Inc.POWER ENGINEERING1.Power Distribution Planning Reference Book,H.Lee Willis2.Transmission Network Protection:Theory and Practice,Y.G.Paithankar3.Electrical Insulation in Power Systems,N.H.Malik,A.A.Al-Arainy,andM.I.Qureshi4.Electrical Power Equipment Maintenance and Testing,Paul Gill5.Protective Relaying:Principles and Applications,Second Edition,J.Lewis Blackburn6.Understanding Electric Utilities and De-Regulation,Lorrin Philipson andH.Lee Willis7.Electrical Power Cable Engineering,William A.Thue8.Electric Systems,Dynamics,and Stability with Artificial IntelligenceApplications,James A.Momoh and Mohamed E.El-Hawary9.Insulation Coordination for Power Systems,Andrew R.Hileman10.Distributed Power Generation:Planning and Evaluation,H.Lee Willis andWalter G.Scott11.Electric Power System Applications of Optimization,James A.Momoh12.Aging Power Delivery Infrastructures,H.Lee Willis,Gregory V.Welch,and Randall R.Schrieber13.Restructured Electrical Power Systems:Operation,Trading,andVolatility,Mohammad Shahidehpour and Muwaffaq Alomoush14.Electric Power Distribution Reliability,Richard E.Brown15.Computer-Aided Power System Analysis,Ramasamy Natarajan16.Power System Analysis:Short-Circuit Load Flow and Harmonics,J.C.Das17.Power Transformers:Principles and Applications,John J.Winders,Jr.18.Spatial Electric Load Forecasting:Second Edition,Revised andExpanded,H.Lee Willis19.Dielectrics in Electric Fields,Gorur G.Raju20.Protection Devices and Systems for High-Voltage Applications,Vladimir Gurevich21.Electrical Power Cable Engineering:Second Edition,Revised andExpanded,William A.Thue22.Vehicular Electric Power Systems:Land,Sea,Air,and Space Vehicles,Ali Emadi,Mehrdad Ehsani,and John M.Miller23.Power Distribution Planning Reference Book:Second Edition,Revisedand Expanded,H.Lee Willis24.Power System State Estimation:Theory and Implementation,Ali Aburand Antonio Gmez Expsito25.Transformer Engineering:Design and Practice,S.V.Kulkarni andS.A.KhapardeADDITIONAL VOLUMES IN PREPARATIONCopyright 2004 by Marcel Dekker,Inc.TransformerEngineeringDesign and PracticeS.V.KulkarniS.A.KhapardeIndian Institute of Technology,BombayMumbai,IndiaNEW YORK BASELMARCEL DEKKER,INC.Copyright 2004 by Marcel Dekker,Inc.Transferred to Digital Printing 2005Although great care has been taken to provide accurate and current information,neither theauthor(s)nor the publisher,nor anyone else associated with this publication,shall be liablefor any loss,damage,or liability directly or indirectly caused or alleged to be caused by thisbook.The material contained herein is not intended to provide specific advice or recom-mendations for any specific situation.Trademark notice:Product or corporate names may be trademarks or registered trademarksand are used only for identification and explanation without intent to infringe.Library of Congress Cataloging-in-Publication DataA catalog record for this book is available from the Library of Congress.ISBN:0-8247-5653-3HeadquartersMarcel Dekker,Inc.,270 Madison Avenue,New York,NY 10016,U.S.A.tel:2126969000;fax:2126854540Distribution and Customer ServiceMarcel Dekker,Inc.,Cimarron Road,Monticello,New York 12701,U.S.A.tel:8002281160;fax:8457961772Eastern Hemisphere DistributionMarcel Dekker AG,Hutgasse 4,Postfach 812,CH-4001 Basel,Switzerlandtel:41612606300;fax:41612606333World Wide Webhttp:/The publisher offers discounts on this book when ordered in bulk quantities.For moreinformation,write to Special Sales/Professional Marketing at the headquarters address above.Copyright 2004 by Marcel Dekker,Inc.All Rights Reserved.Neither this book nor any part may be reproduced or transmitted in any form or by anymeans,electronic or mechanical,including photocopying,microfilming,and recording,orby any information storage and retrieval system,without permission in writing from thepublisher.Current printing(last digit):10 9 8 7 6 5 4 3 2 1Copyright 2004 by Marcel Dekker,Inc.ForewordIt is a great pleasure to welcome this new book from Prof.S.V.Kulkarni and Prof.S.A.Khaparde,and I congratulate them for the comprehensive treatment given inthe book to nearly all aspects of transformer engineering.Everyone involved in or with the subject area of this book,whether fromacademics or industry,knows that the last decade has been particularly dynamicand fast changing.Significant advances have been made in design,analysis anddiagnostic techniques for transformers.The enabling factors for thistechnological leap are extremely competitive market conditions,tremendousimprovements in computational facilities and rapid advances in instrumentation.The phenomenal growth and increasing complexity of power systems have put uptremendous responsibilities on the transformer industry to supply reliabletransformers.The transformer as a system consists of several components and it isabsolutely essential that the integrity of all these components individually and asa system is ensured.A transformer is a complex three-dimensionalelectromagnetic structure,and it is subjected to variety of stresses,viz.dielectric,thermal,electrodynamic,etc.In-depth understanding of various phenomenaoccurring inside the transformer is necessary.Most of these can now be simulatedon computers so that suitable changes can be made at the design stage to eliminatepotential problems.I find that many of these challenges in the design and manufacture oftransformers,to be met in fast changing market conditions and technologicaloptions,are elaborated in this book.There is a nice blend of theory and practice inalmost every topic discussed in the text.The academic background of the authorshas ensured that a thorough theoretical treatment is given to important topics.Anumber of landmark references are cited at appropriate places.The previousindustry experience of S.V.Kulkarni is reflected in many discussions in the book.The various theories have been supported in the text by reference to actualpractices.For example,while deliberating on various issues of stray lossestimation and control,the relevant theory of eddy currents has been firstexplained.This theoretical basis is then used to explain various design andiiiCopyright 2004 by Marcel Dekker,Inc.manufacturing practices established in the industry to analyze and minimize thestray losses in the windings and structural components.The design andmanufacturing practices and processes have significant impact on theperformance parameters of the transformers,and the same have been identified inthe text while discussing various topics.Wherever required,a number of examples and case studies are given which areof great practical value.The knowledge of zero-sequence characteristics oftransformers is very important for utilities.It is essential to understand thedifference between magnetizing and leakage zero-sequence reactances of thetransformer.These two types of zero-sequence reactances are explained in thebook for three-phase three-limb,three-phase five-limb and single-phase three-limb transformers with numerical examples.One may not find such a detailedtreatment to zero-sequence reactances in the available literature.The effect oftank on the zero-sequence reactance characteristics is lucidly explained.The discussions on the sympathetic inrush phenomenon,part-windingresonance,short-circuit withstand characteristics and noise reduction techniquesshould also be quite useful to the readers.With the increase in network complexityand severity of loads in some cases,the cooperation between the transformermanufacturers and users(utilities)is very critical.The design reviews with theinvolvement of users at various stages of contract should help in enhancing thereliability of transformers.I am happy to note that such areas of cooperation areidentified at appropriate places in the text.The book propagates the use of modern computational tools for optimizationand quality enhancement of transformers.I know a number of previouslypublished works of the authors in which Finite Element Method(FEM)has beenapplied for the stray loss control and insulation design of the transformers.The useof FEM has been aptly demonstrated in the book for various calculations alongwith some tips,which will be helpful to a novice in FEM.The book is therefore a major contribution to the literature.The book will beextremely helpful and handy to the transformer industry and users.It will be alsouseful for teaching transformers to undergraduate and postgraduate students inuniversities.The thorough treatment of all-important aspects of transformerengineering given will provide the reader all the necessary background to pursueresearch and development activities in the domain of transformers.It is anticipated that this book will become an essential reference for engineersconcerned with design,application,planning,installation,and maintenance ofpower transformers.H.Jin Sim,PEVP,Waukesha Electric SystemsPast Chairman,IEEE Transformers CommitteeivForewordCopyright 2004 by Marcel Dekker,Inc.PrefaceIn the last decade,rapid advancements and developments have taken place in thedesign,analysis,manufacturing and condition-monitoring technologies oftransformers.The technological progress will continue in the forthcoming years.The phenomenal growth of power systems has put tremendous responsibilities onthe transformer industry to supply reliable and cost-effective transformers.There is a continuous increase in ratings of generator transformers andautotransformers.Further,the ongoing trend to go for higher system voltages fortransmission increases the voltage rating of transformers.The increase in currentand voltage ratings calls for special design and manufacturing considerations.Advanced computational techniques have to be used that should be backed up byexperimental verification to ensure quality of design and manufacturingprocesses.Some of the vital design challenges are:stray loss control,accurateprediction of winding hot spots,short-circuit withstand capability and reliableinsulation design.With the increase in MVA ratings,the weight and size of largetransformers approach or exceed transport and manufacturing capability limits.Also,due to the ever-increasing competition in the global market,there arecontinual efforts to optimize the material content in transformers.Therefore,thedifference between withstand levels(e.g.,short circuit,dielectric)andcorresponding operating stress levels is diminishing.Similarly,the guaranteedperformance figures and actual test values are now very close.All these factorsdemand greater efforts from researchers and designers for accurate calculation ofvarious stress levels and performance figures for the transformers.In addition,strict control of manufacturing processes is required.Manufacturing variations ofcomponents should be monitored and controlled.Many of the standard books on transformers are now more than 10 years old.Some of these books are still relevant and widely referred for understanding thetheory and operation of transformers.However,a comprehensive theoretical basistogether with application of modern computational techniques is necessary toface the challenges of fast-changing and demanding conditions.This book is aneffort in that direction.The principles of various physical phenomena occurringvCopyright 2004 by Marcel Dekker,Inc.within a transformer are explained elaborately in the text,which could also beused in a course at the undergraduate or postgraduate level.Wherever required,adequate references have been cited so that readers can explore the phenomena inmore depth.In fact,a large number of very useful references(more than 400)is oneof the hallmarks of this book.Some of the referencesclassic sources that dateback to the early part of the last centuryexplain many of the theories useful intransformer engineering.Some most recent works are also discussed to givereaders a feel for the latest trends in transformer technology.The first author worked in the transformer industry for 11 years before joiningacademia.He has vast experience in the design and development of transformers,from the small distribution range to 400 kV class 300 MVA ratings.He had ampleopportunity to investigate problems in transformer operations and sites.A fewcase studies and site investigations in which he was actively involved have beenincorporated at appropriate places in the text.Also,he found that some aspects oftransformer engineering had not been given adequate treatment in the booksavailable.Hence,the emphasis of this book is on these aspects:magnetizingasymmetry,zero-sequence reactance characteristics,stray losses and relatedtheory of eddy currents,short-circuit forces and withstand,part windingresonance phenomena,insulation design,and design aspects of transformers forrectifier,furnace and HVDC applications.The book will be particularly useful to:(1)Transformer designers and researchers engaged in optimization andquality-enhancement activities in todays competitiveenvironment(2)Utility engineers who would like to learn more about the systeminteraction aspects of transformers in an interconnected powersystem to improve on specifications and employ diagnostic toolsfor condition monitoring(3)Undergraduate and postgraduate students who wish to integratetraditional transformer theory with modern computing practicesIn Chapter 1,in addition to the transformer fundamentals,various types oftransformers in a typical power system are explained along with their features.There is a trend to use better materials to reduce core losses.Often the expectedloss reduction is not obtained with these better grades.The design andmanufacturing practices and processes that have significant impact on the coreperformance are highlighted in Chapter 2.The three-phase three-limb core hasinherent magnetizing asymmetry that sometimes results in widely different no-load current and losses in three phases of the transformer during the no-load lossmeasurement by the three-wattmeter method.It is shown that one of the threewattmeters can have a negative reading depending on the magnitude ofasymmetry between phases and the level of excitation.Although the inrushcurrent phenomenon is well understood,the sympathetic inrush phenomenonin which the magnetization level of a transformer is affected by energization ofviPrefaceCopyright 2004 by Marcel Dekker,Inc.another interconnected transformeris not well known.The factors influencingthe phenomenon are elucidated in the chapter.The phenomenon was investigatedby the first author in 1993 based on switching tests conducted at a site.Chapter 3 is devoted to reactance of transformers,which can be calculated byeither analytical or numerical methods.Procedures for the calculation ofreactance of various types and configurations of windings,including zigzag andsandwich windings,are illustrated.The reactance for complex windingconfigurations can be easily calculated by the finite element method(FEM),which is the most widely used nu