The J & P Transformer Book J & P Books The J&P Transformer Book and The J&P Switchgear Book were published originally by Johnson & Phillips Ltd, and have for many years been accepted as standard works of reference by electrical engineers concerned with transformers and switchgear They now appear under the Newnes imprint The J & P Transformer Book Twelfth edition A PRACTICAL TECHNOLOGY OF THE POWER TRANSFORMER Martin J Heathcote, CEng, FIEE Newnes OXFORD BOSTON JOHANNESBURG MELBOURNE NEW DELHI SINGAPORE Newnes An imprint of Butterworth-Heinemann Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801-2041 A division of Reed Educational and Professional Publishing Ltd A member of the Reed Elsevier plc group First published 1925 by Johnson & Phillips Ltd Ninth edition 1961 Reprinted by Iliffe Books Ltd 1965 Tenth edition 1973 Reprinted 1967 (twice), 1981 Eleventh edition 1983 Reprinted 1985, 1988, 1990, 1993, 1995 Twelfth edition 1998 © Reed Educational and Professional Publishing Ltd 1998 All rights reserved No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Rd, London, England W1P 9HE Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 07506 1158 Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of congress Typeset by Laser Words, Madras, India Printed in Great Britain Contents Foreword Preface Acknowledgements Transformer theory 1.1 Introduction 1.2 The ideal transformer voltage ratio 1.3 Leakage reactance transformer impedance 1.4 Losses in core and windings 1.5 Rated quantities 1.6 Regulation Design Fundamentals 2.1 Types of transformers 2.2 Phase relationships phasor groups 2.3 Volts per turn and flux density 2.4 Tappings 2.5 Impedance 2.6 Multi-winding transformers including tertiary windings 2.7 Zero-sequence impedance 2.8 Double secondary transformers 2.9 General case of three-winding transformers Basic Materials 3.1 Dielectrics 3.2 Core steel 3.3 Winding conductors 3.4 Insulation 3.5 Transformer oil Transformer construction 4.1 Core construction 4.2 Transformer windings 4.3 Disposition of windings 4.4 Impulse strength 4.5 Thermal considerations 4.6 Tappings and tapchangers 4.7 Winding forces and performance under short-circuit 4.8 Tanks and ancillary equipment 4.9 Processing and drying out ix xi xiii 1 10 11 13 13 17 22 23 24 27 32 33 35 40 40 41 53 59 74 103 104 118 143 148 156 167 226 245 280 vi Contents Testing of transformers 5.1 Testing and quality assurance during manufacture 5.2 Final testing 5.3 Possible additional testing for important transformers 5.4 Transport, installation and commissioning Operation and maintenance 6.1 Design and layout of transformer installations 6.2 Neutral earthing 6.3 Transformer noise 6.4 Parallel operation 6.5 Transient phenomena occurring in transformers 6.6 Transformer protection 6.7 Maintenance in service 6.8 Operation under abnormal conditions 6.9 The influence of transformer connections upon third-harmonic voltages and currents Special features of transformers for particular purposes 7.1 Generator transformers 7.2 Other power station transformers 7.3 Transmission transformers and autotransformers 7.4 Transformers for HVDC converters 7.5 Phase shifting transformers and quadrature boosters 7.6 System transformers 7.7 Interconnected-star earthing transformers 7.8 Distribution transformers 7.9 Scott and Le Blanc connected transformers 7.10 Rectifier transformers 7.11 AC arc furnace transformers 7.12 Traction transformers 7.13 Generator neutral earthing transformers 7.14 Transformers for electrostatic precipitators 7.15 Series reactors Transformer enquiries and tenders 8.1 Transformer enquiries 8.2 Assessment of tenders 8.3 Economics of ownership and operation, cost of losses 313 313 315 377 384 398 398 408 422 445 485 519 560 612 636 661 661 673 679 681 690 697 703 707 729 736 739 745 750 756 758 764 764 789 793 APPENDICES Transformer equivalent circuit Geometry of the transformer phasor diagram The transformer circle diagram 803 814 820 Contents Transformer regulation Symmetrical components in unbalanced three-phase systems A symmetrical component study of earth faults in transformers in parallel The use of finite element analysis in the calculation of leakage flux and dielectric stress distributions List of National and International Standards relating to power transformers List of principal CIGRE reports and papers relating to transformers 10 List of reports issued by ERA Technology Limited relating to transformers and surge phenomena therein Index vii 825 829 851 904 931 934 937 941 Foreword The J & P Transformer Book has been in print for 75 years and during that time it has been a rewarding work of reference for students, young engineers, older engineers who have changed the direction of their careers to become involed with transformers, practising designers and for generations of applications engineers In the previous eleven editions the publishers endeavoured to revise the work, extend it and to bring it up to date The fact that The J & P Transformer Book is still in demand is a tribute to the publishers and to the authors who have carried the torch to light our way for 75 years The first edition was prepared by Mr H Morgan Lacey in 1925, based on a series of pamphlets entitled Transformer Abstracts that were first printed in 1922 The book was welcomed as a key reference, giving a guide to British experience at a time of great change in transformer technology It was reprinted and revised many times during the next three decades The ninth edition was produced in 1958 by Mr A C Franklin together with his co-author Mr S A Stignant The tenth edition was produced in 1961 by the same authors, and was revised in 1965 Mr Stignant later retired leaving Mr Franklin, as the main author of the eleventh edition, to carry on the work This edition was published in 1983 with some assistance from Mr D P Franklin, who had been appointed as his co-author The current twelfth edition has been prepared by Martin J Heathcote Unlike the previous authors, Mr Heathcote has experience as both a manufacturer and a purchaser His most recent appointment was with PowerGen, a successor company to CEGB, where he gained a wide experience in the design and manufacturing techniques adopted by many different transformer manufacturers both in Britain and overseas His strong relationship with manufacturers and users has allowed him access to a wide range of information that has been included in this edition In particular he has completely rewritten many sections of the book to bring it up to date and reflect current experience The latest information on transformer materials has been included, the modern trend to design transformers with the lowest lifetime costs has been addressed, and interface problems with other equipment has been considered in each section Mr Heathcote’s extensive experience in the operation and maintenance phases of transformer life has been included in this edition, together with a more complete analysis of the many specialist types of transformer that are installed on supply systems and in industrial networks This edition contains a wealth of new technical information that has been freely made available by transformer manufacturers, the electrical supply x Foreword industry, learned institutions and industrial associations such as CIGRE It is intended that the information contained in this twelfth edition of The J & P Transformer Book will update the knowledge of the current generation of engineers and will be of as much use to new generations of engineers as the previous editions have been to their predecessors Professor Dennis J Allan FEng Stafford, 16 March 1998 Preface to the twelfth edition A brief history of the J & P Transformer Book and of its many distinguished previous authors appears elsewhere in this volume From this it will be seen that most were chief transformer engineers or chief designers for major manufacturers The effect of this has been twofold One, all have tended to write from a manufacturer’s point of view, and two, all have held very demanding ‘day jobs’ whilst attempting to bring the benefit of their particular knowledge and experience to the task of revising and updating the efforts of their predecessors This is a task of great magnitude, and as a result of the many conflicting demands for their time, even the many ‘complete revisions’ of the J & P Transformer Book have not greatly changed the unique character that can be traced back to 1925 The production of the twelfth edition has been taken as an opportunity to carry out an almost total rewrite, and, as well as making significant changes to the structure, to change the viewpoint significantly towards that of the transformer user It is hoped that the book will, nevertheless, still be of value to the young graduate engineer embarking upon a design carreer, as well as to the student and those involved in transformer manufacture in other than a design capacity To provide more specialist design information than this would require a very much larger volume and would probably have had the effect of discouraging a significant proportion of the prospective readership For the more advanced designer, there are other sources, the work of CIGRE, many learned society papers, and some textbooks Primarily the objective has been to provide a description of the principles of transformer design and construction, testing operation and maintenance, as well as specification and procurement, in sufficient depth to enable those engineers who have involvement with transformers in a system design, installation or maintenance capacity to become ‘informed users,’ and it is hoped that, in addition, all of that valuable operational guidance contained in earlier editions has been retained and made more relevant by being brought fully into line with current thinking Above all, the hope is that the successful formula which has led to the enormous popularity of earlier editions has not been lost and it is hoped that the information contained in this edition will prove even more useful to today’s engineers than those editions which have gone before MJH Appendix 927 Figure A7.15 Figure A7.16 Future development It is clearly evident from assessing the needs of designers that fully automated procedures, in which the finite element approach appears as a ‘black box’, are required The current software has been written with this in mind and it is becoming relatively simple to link mesh routines, solvers and post processors together through the use of shell scripts The modular form of the programs also makes it easier to merge with other engineering design procedures such as Thermal, Mechanical etc Even though the design process becomes automated it is still possible to inspect or locally modify the mesh As far as improvement 928 Appendix Figure A7.17 Figure A7.18 to the solvers is concerned more work is required to improve time stepping techniques to reduce solution times and make them more flexible in their use Further development of 3-dimensional solvers is required to simplify their use on difficult ‘real’ engineering problems, but it will not be long before they are used as a regular design tool Finally, other techniques are being researched and one which may improve modelling capabilities, especially in 3-dimensions, is the hybrid method This is a combination of the boundary element and finite element method: the Appendix 929 Figure A7.19 Figure A7.20 finite element method models non-linear regions while the boundary element method models linear regions and external boundaries The main advantage is that individual components can be discretised without the need to mesh the air region which links them together, so reducing the time taken to build 3-dimensional models 930 Appendix Conclusions The preceding sections have shown that the finite element method has become a well established design tool enabling the solution of engineering problems not previously possible In order to facilitate its regular use in the design environment automatic procedures, which incorporate the finite element method, have been developed These have proved extremely useful in optimising designs but most of all in providing a clear understanding of the complete electromagnetic effect within the equipment Finally, it is only the engineer who can be innovative but it is believed that these electromagnetic CAD tools will enable him to achieve his aims more quickly and with a high degree of reliability Acknowledgements The authors wish to thank GEC ALSTHOM product companies for the use of information relating to their products Also to thank their friends and colleagues in the Electromagnetics Group of the GEC ALSTHOM Engineering Research Centre, Stafford, who have aided in the development of these techniques over many years References [1] Ray, A K ‘A study of the flux distribution in electrical machines, under non-linear conditions, using finite-difference and finite-element methods’, Ph D University of London [2] Silvester P and Chari, M V K (1970) ‘Finite-element solution of saturable magnetic field problems’, IEEE Trans., PAS-89, pp 1642 1649 [3] Jenning, A (1996) ‘A Compact Storage Scheme for the Solution of Symmetric Linear Simultaneous Equations’, Comput J (GB), 9, pp 281 285 [4] Kershaw, D S (1978) ‘The Incomplete Cholesky Conjugate Gradient Method for the Iterative Solution of Systems of Linear Equations’, J Comp Phys., No 26, pp 43 65 Appendix List of National and International Standards relating to power transformers UK National Standards European Standards BS EN 60076-1 (1997): Power transformers: Part General BS EN 60076-2 (1997): Power transformers: Part Temperature rise BS 171: Part 3: 1987 Power transformers: Part Insulation levels and dielectric tests EN 60076-1 (1997): Power transformers: Part General EN 60076-2 (1997): Power transformers: Part Temperature rise HD 398.3 (1986): Power transformers: Insulation levels and dielectric tests 931 BS 171: Part 5: 1978 Ability to withstand short-circuit HD 398.5 (1983): Ability to withstand short-circuit BS 4571: On-load tapchangers BS EN 60289: 1995 Reactors BS 7735: 1994 Guide to loading of oil-immersed power transformers HD 367 (1992): On-load tapchangers EN 60289 (1984): Reactors Not harmonised International Standards IEC Part IEC Part IEC Part 76-1 (1993): Power transformers: General 76-2 (1993): Power transformers: Temperature rise 76-3 (1980): Power transformers: Insulation levels IEC 76-3-1 (1987): External clearances in air IEC 76-5 (1976): Power transformers: Part Ability to withstand short-circuit IEC 214 (1989): On-load tapchangers IEC 289 (1988): Reactors IEC 354 (1991): Loading guide for oil-immersed transformers UK National Standards BS 5611: 1978 Application guide for on-load tapchangers BS EN 60551 (1993): Determination of transformer and reactor sound levels BS 5953: Part 1: 1980 Application guide for power transformers BS 7806: 1995 transformers Dry-type power European Standards Not harmonised EN 60551 (1987): Determination of transformer and reactor sound levels HD 464 (1991): Dry-type power transformers International Standards IEC 542 (1976): Application guide for on-load tapchangers IEC 551 (1987): Determination of transformer and reactor sound levels IEC 606 (1977): Application guide for power transformers IEC 616 (1978): Terminal and tapping markings for power transformers IEC 722 (1982): Guide for lightning impulse and switching impulse testing of power transformers IEC 726 (1982): Dry-type power transformers IEC 905 (1987): Loading guide for dry-type power transformers UK National Standards European Standards BS 7821: Part 1: 1995 Three-phase oil-immersed distribution transformers: Part General requirements and requirements for transformers with highest voltage for equipment not exceeding 24 kV HD 428.1 (1991): Three-phase oil-immersed distribution transformers: Part General requirements and requirements for transformers with highest voltage for equipment not exceeding 24 kV BS 7821: Part 2: Section 2.1: 1995 Three-phase oil-immersed distribution transformers: Part 2.1 Distribution transformers with cable boxes on the high voltage and/or the low voltage side HD 428.2.1 (1994): Three-phase oil-immersed distribution transformers: Part 2.1 Distribution transformers with cable boxes on the high voltage and/or the low voltage side UK National Standards BS 7821: Part 3: 1995 Supplementary requirements for transformers with highest voltage for equipment equal to 36 kV BS 7821: Part 4: 1995 Determination of the power rating of a transformer loaded with non-sinusoidal currents BS 7844: Part 1: 1996 Three phase dry-type distribution transformers: Part General requirements and requirements for transformers with highest voltage for equipment not exceeding 24 kV BS 7844: Part 2: 1996 Supplementary requirements for transformers with highest voltage for equipment equal to 36 kV BS EN 50195: 1997 Code of practice for the safe use of askerel filled electrical equipment BS EN 50225: 1997 Code of practice for the safe use of fully enclosed oil-filled electrical equipment which may contain PCBs BS 2562: 1979 Cable boxes for transformers and reactors BS 6435: 1984 Unfilled enclosures for the dry termination of HV cables for transformers and reactors BS 6436: 1984 Ground mounted distribution transformers for cable box or unit substation connection European Standards HD 428.3 (1994): Supplementary requirements for transformers with highest voltage for equipment equal to 36 kV HD 428.4 (1994): Determination of the power rating of a transformer loaded with non-sinusoidal currents HD 538.1 (1992): Three phase dry-type distribution transformers: Part General requirements and requirements for transformers with highest voltage for equipment not exceeding 24 kV HD 538.2 (1995): Supplementary requirements for transformers with highest voltage for equipment equal to 36 kV EN 50195 (1996): Code of practice for the safe use of askerel filled electrical equipment EN 50225 (1996): Code of practice for the safe use of fully enclosed oil-filled electrical equipment which may contain PCBs Extracts from British and International Standards are reproduced with permission Complete editions of the standards can be obtained by post from BSI Customer Services, 389 Chiswick High Road, London W4 4AL, telephone 0181 996 7000, facsimile 0181 996 7001 Appendix List of principal CIGRE reports and papers relating to transformers REPORTS FROM STUDY COMMITTEE 12 (TRANSFORMERS) WORKING GROUPS WG 12.02 HVDC transformers ‘Voltage tests on transformers and smoothing reactors for HVDC transmission’ Electra No 46, May 1976, pp 19 38 WG 12.03 Partial discharge testing ‘Volt time relationships for PD inception in oil paper insulation’ Electra No 67, December, 1979, pp 17 28 WG 12.05 Reliability survey ‘An international survey on failure in large power transformers in service’ Electra No 88, January 1983, pp 21 48 WG 12.06 Large transformers ‘Final report of WG 06 of Study Committee 12 (Transformers)’ Electra No 82, May 1982, pp 31 46 WG 12.07 Part-winding resonance ‘Resonance behaviour of high-voltage transformers’ CIGRE Report 12 14, 1984 WG 12.09 Thermal problems in transformers 6.1 ‘Recent developments by CEGB to improve the prediction and monitoring of transformer performance’, Burton, P J., Graham, J., Hall, A C., Laver, J A and Oliver, A J., September 1984 934 Appendix 935 6.2 ‘Heat run test procedure for power transformers’ 6.3 ‘Direct measurement of hot spot temperature on transformers’ 6.4 ‘A survey of facts and opinions on the maximum safe operating temperature of power transformers under emergency conditions’ Electra No 129, March 1990, pp 37 64 (see also items 13 and 16) 6.5 ‘Estimation of the remaining service life of power transformers and their insulation’ Electra No 133, December 1990, pp 652 72 6.6 ‘Lifetime evaluation of transformers’ Electra No 150, October 1993, pp 38 51 6.7 ‘Dissolved gas analysis during heat-run tests on power transformers’ 6.8 ‘Analytical determination of transformer windings hot-spot factor’ 6.9 ‘Experimental determination of power transformers hot-spot factor’ 6.10 ‘Survey of power transformer overload practices’ Electra No 168, August 1995, pp 21 52 JWG 12/14.10 HVDC converter transformers 7.1 ‘HVDC converter transformers a review of specification content’ Electra No 141, April 1992, pp 34 50 7.2 ‘In-service performance of HVDC converter transformers and oil cooled smoothing reactors’ Electra No 155, August 1994, pp 32 7.3 ‘The relationship between test and service stresses as a function of resistivity ratio for HVDC converter transformers and smoothing reactors’ Electra No 157, December 1994, pp 33 60 7.4 ‘HVDC converter transformer noise considerations’ Electra No 167, August 1996, pp 39 48 7.5 ‘Considerations of impedances and tolerances for HVDC converter transformers’ Electra No 167, August 1996, pp 49 58 WG 12.11 Fast transients in transformers ‘Distribution of very fast transient overvoltages in transformer windings’ CIGRE Report 12-204, 1992 WG 12.12 Noise measurements for transformers 9.1 IEC TC 14 (Secretariat) 190 Appendix B to IEC 551: Measurement of sound power level using sound intensity 9.2 IEC TC 14 (Secretariat) 194 Appendix C to IEC 551: Determination of current sound level 936 Appendix 9.3 ‘Transformer noise: determination of sound power level using the sound intensity measurement method’ Electra No 144, October 1992, pp 78 95 10 JWG 12/15.13 Static electrification ‘Static electrification in power transformers’ CIGRE Report 15/12.03, 1992 (see also item 13.4) OTHER ELECTRA PUBLICATIONS 11 ‘Problems related to cores of transformers and reactors’, H Kan Electra No 94, May 1984, pp 15 33 12 ‘Experience of the new dielectric tests (IEC publication 76-3) for power transformers with highest voltage for equipment greater than or equal to 245 kV’, W D Lampe Electra No 108, October 1986, pp 104 117 13 Joint Colloquium of Study Committees 12 and 15 on ‘Current problems in insulating systems including assessment of ageing and degradation’, 1989 Rio de Janeiro, Brazil 13.1 ‘Dissolved gas analysis current problems of a mature technique’, C Sobrel Vieira 13.2 ‘Dissolved gas analysis new challenges and applications’, M Duval 13.3 ‘HLPC contribution to transformer during service and heat run tests’, M Carballiera 13.4 ‘Progress in the control of static electrification in transformers’, S R Lindgren 13.5 ‘Factors which affect the electric strength and endurance of polymeric materials’, J H Mason 13.6 ‘Estimation of the remaining service life of power transformers and their insulation’, L Pettersson Electra No 133, December 1990, pp 32 72 14 ‘Effects of geomagnetically induced currents in power transformers’, J Aubin Electra No 141, April 1992, pp 24 33 15 ‘Use of ZnO varistors in transformers’, R Baehr Electra No 143, August 1992, pp 32 37 OTHER PUBLICATIONS CIRCULATED WITHIN STUDY COMMITTEE 16 ‘Summary of contributions from colloquium on thermal aspects of transformers at Rio de Janeiro, October 1989’, J Aubin Appendix 10 List of reports available from ERA Technology Ltd, formerly British Electrical and Allied Industries Research Association (ERA), relating to transformers and surge phenomena therein TRANSFORMERS Ref Q/T101a ‘Mechanical stresses in transformer windings’, by M Waters Ref Q/T103 ‘Electrical and mechanical effects of internal faults in transformers’, by E Billig Ref Q/T113 ‘The measurement of axial magnetic forces in transformer windings’, by M Waters Ref Q/T115 ‘The calculation of transformer thermal data from readings taken in service’, by M R Dickson Ref Q/T116 ‘Generation of gases in transformers R´ sum´ of available e e information’, by M R Dickson Ref Q/T117 ‘Temperature gradients in transformer windings and rates of oil flow in transformer tanks A critical review of published information’, by B L Coleman Ref Q/T118 ‘The operation of naturally cooled outdoor transformers as affected by weather and surroundings Preliminary review’, by M R Dickson Ref Q/T121 ‘The calculation of currents due to faults between turns in transformer windings’, by B L Coleman Ref Q/T126 ‘The causes and effects of water in oil-immersed transformers A critical r´ sum´ ’, by M R Dickson e e Ref Q/T130 ‘Corrosion of internal tank surfaces in non-conservator transformers’, by M Waters Ref Q/T134 ‘The measurement and calculation of axial electromagnetic forces in concentric transformer windings’, by M Waters 937 938 Appendix 10 Ref Q/T139 ‘The effects of dissolved gases in the design and operation of oil immersed transformers’, by M.R Dickson Ref Q/T141 ‘An adjustable ambient-temperature thermometer for use when testing transformers’, by M R Dickson Ref Q/T144 ‘The effect of core properties on axial electromagnetic forces in transformers with concentric windings’, by M Waters Ref Q/T151 ‘A method based on Maxwell’s equations for calculating the axial short-circuit forces in the concentric windings of an idealized transformer’, by P R Vein Ref Q/T153 ‘The measurement of axial displacement of transformer windings’, by M Waters Ref Q/T158 ‘Measurement of axial forces in a transformer with multi-layer windings’, by E D Taylor, J Page and M Waters Ref Q/T161 ‘Copper for transformer windings’, by J E Bowers and E C Mantle Ref Q/T163 ‘E.R.A researches on transformer noise 1951 59’, by A I King, A S Ensus and M Waters Ref G/T130 ‘The effect of zero phase sequence exciting impedance of threephase core transformers on earth fault currents’, by L Gosland Ref G/T140 ‘Some measurements of zero phase sequence impedance of three-phase, three-limb, core-type transformers with a delta winding’, by L Gosland Ref G/T313 ‘Measurement of overvoltages caused by switching out a 75 MVA, 132/33 kV transformer from the high voltage side’, by M P Reece and E L White Ref V/T123 ‘Application of the dispersion test to the drying of high voltage transformers’, by D C G Smith Ref 5028 ‘The mechanical properties of high conductivity copper conductors for power transformers’, by M Waters Ref 5081 ‘The mechanical properties of high conductivity aluminium conductors for power transformers’, by M Waters Ref 5096 ‘The ventilation of transformer substations or cubicles’, by M R Dickson Ref 5149 ‘An exploration of some mechanical factors affecting vibration and noise of transformer cores’, by L Gosland and M Waters Ref 5152 ‘Transformer magnetising inrush currents A r´ sum´ of e e published information’, by A A Hudson Ref 5146 ‘The effect of the level of magnetostriction upon noise and vibration of model single-phase transformers’, by N Mullineux, D E Jones and J R Reed Ref 5213 ‘Effect of slots or ducts on breakdown voltage with particular reference to transformer windings’, by N Mullineux, D E Jones and J R Reed Ref 5252 ‘Detection of winding damage in power transformers using the low-voltage impulse method’, by M Waters and R R Smith Appendix 10 Ref 5285 939 ‘A study of ferrous based soft magnetic materials for transformer and similar applications’, by T F Foley, D A Leak, R A Newbury, A R Pomeroy and A R Matthews SURGE PHENOMENA Ref S/T35 ‘Surge phenomena Seven years’ research for the Central Electricity Board (1933 1940)’, edited by H M Lacey with a foreword by E B Wedmore Ref S/T43 ‘Surge tests on a transformer with and without protection’, by H M Lacey and E W W Double Ref S/T48 ‘Surge voltage distribution in a continuous-disc transformer winding’, by K L Selig Ref S/T54 ‘An investigation of flashovers on a low voltage busbar system’, by L Gosland and E L White Ref S/T69 ‘The effects of cylindrical end rings on the distribution of surge voltages in transformer windings’, by E L White Ref S/T73 ‘Surge voltage distribution in transformer windings due to current chopping’, by E L White Ref S/T85 ‘Impulse-excited terminal oscillations due to no-load switching of a three-phase transformer installation’, by E L White Ref S/T95 ‘Transients in transformer windings’, by B L Coleman Ref S/T97 ‘Line and neutral currents in multi-limb transformers under impulse-test conditions’, by E L White Ref S/T98 ‘An experimental study of transient oscillations in windings of core-type transformers’, by E L White Ref S/T103 ‘A simple technique for producing test voltages across a transformer winding by current chopping’, by M P Reece and E L White Ref S/T109 ‘Transference of surges through a generator transformer with special reference to neutral earthing Field tests on a 15.8 MVA generator’, by E L White Ref S/T111 ‘Switching surges on a 275/132 kV auto-transformer’, by E L White Ref S/T112 ‘A summary of the E.R.A theory of oscillations and surges in transformer windings’, by R J Clowes and E L White Ref S/T115 ‘A capacitive probe method of exploring voltage distributions in windings’, by E L White Ref S/T116 ‘Maximum voltages on concentric transformer windings subjected to one-, two- or three-pole impulses’, by R J Clowes Ref 5015 ‘Excessive voltages induced in an inner winding of a transformer during impulse tests on an outer winding’, by R J Clowes Ref 5063 ‘Calculation of voltages induced in an inner winding of a transformer when an impulse is applied to the outer winding’, by R J Clowes 940 Appendix 10 Ref 5133 Ref 5134 Ref 5144 Ref 5153 Ref 5210 ‘Surge transference in generator transformers A study based on published information’, by E L White ‘Controlled current chopping as a possible overvoltage test method for transformers on site’, by E L White ‘Excessive surge voltages in a 33 kV earthing transformer’, by E L White ‘Surge voltage transference in a 100 MW unit-connected generator set at Aberthaw Station’, by E L White ‘Surge transference measurements on generator transformers connected to systems above 100 kV’, by E L White REPORTS ISSUED BY ERA TECHNOLOGY LIMITED 81 0062R ‘Monitoring transformers in service for winding displacement using the low voltage impulse method’, E L White, 1981, ISBN 7008 0283 5, 44 pp 87 0021 ‘The low flammability transformer’, M R Dickson, April 1987, ISBN 7008 0365 3, 83 pp 87 0259R ‘Measurement of the frequency response characteristics of typical distribution transformers and their influence on mains signalling’, G W A McDowell, W W C Hung, December 1987, ISBN 7008 0457 9, 43 pp 88 0406 Coil Winding International Wembley, London, September 1988 Conference Proceedings, ISBN 7008 0385 8, 184 pp 88 0478R ‘A report and commentary on insulating materials, transformers, and HV cables in CIGRE 1988’, N A Parkman, December, 1988, 83 pp 88 0566R ‘Condition monitoring of power transformers to assess residual life and fault damage’, G W A McDowell, June 1989, ISBN 7008 0447 1, 44 pp 90 0715 ‘Winding design for high-frequency transformers’, G Dubois, January 1991, 42 pp Index Air-bag seal, 254 Antivibration mountings, 441 Arrhenius law, 614 Askerels, 100 Antotransformers, 22 Back-e.m.f., Breathers, breathing systems, 98 refrigeration, 252 silica-gel, 252 Brentford regulator, 220 Buchholz relay, 573 Bushing CTs, 260 Bushings, 256 condenser, 257 high current, 260 Capacity charge, 799 Cast resin transformers, 405, 717 Commissioning, 394 Condition monitoring, 587, 607 Conservators, 251 Continuously transposed conductor, 126 Cooling: control systems, 276 core and internal steelwork, 163 double tube/double tube plate, 274 forced air, 277 leads, 163 water, 271 radiators, 165 sea water, 274 separate banks, 269 tank-mounted, 266 type of, 160 Co-ordinating gaps, 154 Copper: alloys, 57 extraction sites, 55 high conductivity, 53, 57 properties of, 58 silver bearing, 57 touch pitch, 55 winding wires, 59 Core: building, 112 building factor, 109 earthing, 116 flux density, 4, 22, 23, 25, 135, 775 frames, 109 frame size, 26, 105, 120 laminations: annealing of, 107 insulation of, 107 leg length, 120 saturation, 22 steel: amorphous, 48 cold rolled, 44 designation of, 51 domain refined, 46 grain oriented, 44 high permeability, 46 hot rolled, 43 laser etched, 46 microcrystaline, 51 tie-bars, 231 window, 119 Cores: bolts in, 109 boltless, 109 core type, 13 edge-burrs, limits of, 107 five limb, 107 mitred, 109 seven step, 105 shell type, 13 single-phase, 16, 105 step-lapped, 113, 436, 708 three-phase, 15, 105 wound, 708 Corrugated tanks, 225 Cotton linters, 63 Crimped connections, 128 Crossover coils, 711 Degradation of cellulose, 602 Design intent document, 767 Detanking, on-site, 246 Digital data collection, 352 Dissolved gas analysis, 587 during works testing, 604 Distribution transformers, 707 Double secondary transformers, 33 Double wound transformers, 17 Drainage of transformer compounds, 400 Drying out: in works, 280 on site, 389 vapour phase, 280 Dry-type transformers, 405, 717 .. .J & P Books The J& P Transformer Book and The J& P Switchgear Book were published originally by Johnson & Phillips Ltd, and have for many years been accepted as standard works... concerned with transformers and switchgear They now appear under the Newnes imprint The J & P Transformer Book Twelfth edition A PRACTICAL TECHNOLOGY OF THE POWER TRANSFORMER Martin J Heathcote,. .. although these not, in fact, occur simultaneously and, in the case of polyphase transformers, by multiplying by the appropriate phase factor and the appropriate constant depending on the magnitude