IET POWER AND ENERGY SERIES 66

High-VoltageEngineeringand Testing

Other volumes in this series:

Volume 1 Power circuit breaker theory and design C.H. Flurscheim (Editor)Volume 4 Industrial microwave heating A.C. Metaxas and R.J. MeredithVolume 7 Insulators for high voltages J.S.T. LoomsVolume 8 Variable frequency AC motor drive systems D. FinneyVolume 10 SF6 switchgear H.M. Ryan and G.R. JonesVolume 11 Conduction and induction heating E.J. DaviesVolume 13 Statistical techniques for high voltage engineering W. Hauschild and W. MoschVolume 14 Uninterruptible power supplies J. Platts and J.D. St Aubyn (Editors)Volume 15 Digital protection for power systems A.T. Johns and S.K. SalmanVolume 16 Electricity economics and planning T.W. BerrieVolume 18 Vacuum switchgear A. GreenwoodVolume 19 Electrical safety: a guide to causes and prevention of hazards J. Maxwell AdamsVolume 21 Electricity distribution network design, 2nd edition E. Lakervi and E.J. HolmesVolume 22 Artificial intelligence techniques in power systems K. Warwick, A.O. Ekwue and

R. Aggarwal (Editors)Volume 24 Power system commissioning and maintenance practice K. HarkerVolume 25 Engineers handbook of industrial microwave heating R.J. MeredithVolume 26 Small electric motors H. Moczala et al.Volume 27 ACDC power system analysis J. Arrillaga and B.C. SmithVolume 29 High voltage direct current transmission, 2nd edition J. ArrillagaVolume 30 Flexible AC Transmission Systems (FACTS) Y-H. Song (Editor)Volume 31 Embedded generation N. Jenkins et al.Volume 32 High voltage engineering and testing, 2nd edition H.M. Ryan (Editor)Volume 33 Overvoltage protection of low-voltage systems, revised edition P. HasseVolume 34 The lightning flash V. CoorayVolume 36 Voltage quality in electrical power systems J. Schlabbach et al.Volume 37 Electrical steels for rotating machines P. BeckleyVolume 38 The electric car: development and future of battery, hybrid and fuel-cell cars

M. WestbrookVolume 39 Power systems electromagnetic transients simulation J. Arrillaga and N. WatsonVolume 40 Advances in high voltage engineering M. Haddad and D. WarneVolume 41 Electrical operation of electrostatic precipitators K. ParkerVolume 43 Thermal power plant simulation and control D. FlynnVolume 44 Economic evaluation of projects in the electricity supply industry H. KhatibVolume 45 Propulsion systems for hybrid vehicles J. MillerVolume 46 Distribution switchgear S. StewartVolume 47 Protection of electricity distribution networks, 2nd edition J. Gers and

E. HolmesVolume 48 Wood pole overhead lines B. WareingVolume 49 Electric fuses, 3rd edition A. Wright and G. NewberyVolume 50 Wind power integration: connection and system operational aspects B. Fox

et al.Volume 51 Short circuit currents J. SchlabbachVolume 52 Nuclear power J. WoodVolume 53 Condition assessment of high voltage insulation in power system equipment

R.E. James and Q. SuVolume 55 Local energy: distributed generation of heat and power J. WoodVolume 56 Condition monitoring of rotating electrical machines P. Tavner, L. Ran, J. Penman

and H. SeddingVolume 57 The control techniques drives and controls handbook, 2nd edition B. DruryVolume 58 Lightning protection V. Cooray (Editor)Volume 59 Ultracapacitor applications J.M. MillerVolume 62 Lightning electromagnetics V. CoorayVolume 63 Energy storage for power systems, 2nd edition A. Ter-GazarianVolume 65 Protection of electricity distribution networks, 3rd edition J. GersVolume 905 Power system protection, 4 volumes

High-VoltageEngineeringand Testing

3rd Edition

Edited by Hugh M. Ryan

The Institution of Engineering and Technology

Published by The Institution of Engineering and Technology, London, United Kingdom

The Institution of Engineering and Technology is registered as a Charity inEngland & Wales (no. 211014) and Scotland (no. SC038698).

First edition Peter Peregrinus Ltd 1994Second edition The Institution of Electrical Engineers 2001Third edition The Institution of Engineering and Technology 2013

First published 1994 (0 86341 293 9)Second edition 2001 (0 85296 775 6)Reprinted with new cover 2009Third edition 2013

This publication is copyright under the Berne Convention and the Universal CopyrightConvention. All rights reserved. Apart from any fair dealing for the purposes of researchor private study, or criticism or review, as permitted under the Copyright, Designs andPatents Act 1988, this publication may be reproduced, stored or transmitted, in anyform or by any means, only with the prior permission in writing of the publishers, or inthe case of reprographic reproduction in accordance with the terms of licences issuedby the Copyright Licensing Agency. Enquiries concerning reproduction outside thoseterms should be sent to the publisher at the undermentioned address:

The Institution of Engineering and TechnologyMichael Faraday HouseSix Hills Way, StevenageHerts, SG1 2AY, United Kingdom

www.theiet.org

While the authors and publisher believe that the information and guidance givenin this work are correct, all parties must rely upon their own skill and judgement whenmaking use of them. Neither the authors nor publisher assumes any liability toanyone for any loss or damage caused by any error or omission in the work, whethersuch an error or omission is the result of negligence or any other cause. Any and allsuch liability is disclaimed.

The moral rights of the authors to be identified as authors of this work have beenasserted by them in accordance with the Copyright, Designs and Patents Act 1988.

British Library Cataloguing in Publication DataA catalogue record for this product is available from the British Library

ISBN 978-1-84919-263-7 (hardback)ISBN 978-1-84919-264-4 (PDF)

Typeset in India by MPS LimitedPrinted in the UK by CPI Group (UK) Ltd, Croydon

Dedicated to colleagues, students and clients whom I have workedwith over the years at Reyrolle, Sunderland University, IET, IEC,DTI, EPSRC and CIGRE, as well as via research collaborations withutilities and academia (e.g. Universities of Liverpool, Strathclyde,UMIST and Northumbria). A special thanks to my four grandchildren,Alex, Ellie, Lisa and Owen, for the great pleasure they have given meover the past 20 years, and for urging me to finish this book.

[Hugh M. Ryan, Editor, 2013]

Contents

List of contributors xxv

Preface xxvii

Introdution 1

1 Electric power transmission and distribution systems 17I.A. Erinmez1.1 Introduction 171.2 Development of transmission and distribution systems 19

1.2.1 Early developments (18801930) 191.2.2 The development of the transmission grid

concept (193090) 211.2.3 Global developments 231.2.4 Recent developments 1990 to date (or 1990

onwards or post 1990) 261.3 Structure of transmission and distribution systems 30

1.3.1 Technical factors influencing the structure oftransmission and distribution systems 32

1.3.2 Organisational structures 341.4 Design of transmission and distribution systems 38

1.4.1 Security of supply 391.4.2 Quality of supply 391.4.3 Stability 40

1.5 Operation of transmission and distribution systems 411.5.1 Operational planning 411.5.2 Extended real-time operation 421.5.3 Real-time operation 421.5.4 Post real-time operation 43

1.6 Future developments and challenges 431.6.1 Organisational developments 431.6.2 Technical and technological developments 451.6.3 Control and communication developments 53

References 54

2 Insulation co-ordination for AC transmission and distribution systems 57T. Irwin and H.M. Ryan2.1 Introduction 572.2 Classification of dielectric stress 61

2.2.1 Power frequency voltage 612.2.2 Temporary overvoltages 612.2.3 Switching overvoltages 632.2.4 Lightning overvoltages 63

2.3 Voltagetime characteristics 632.4 Rated withstand voltage levels 642.5 Factors affecting switching overvoltages 67

2.5.1 Source configuration 672.5.2 Remanent charge 682.5.3 Transmission line length 692.5.4 Compensation 702.5.5 Circuit-breaker pole scatter 702.5.6 Point-on-wave of circuit-breaker closure 71

2.6 Methods of controlling switching surges 712.6.1 Circuit-breaker pre-insertion resistors 712.6.2 Metal oxide surge arresters 722.6.3 Circuit-breaker point-on-wave control 772.6.4 Comparison of switching overvoltage control methods 782.6.5 Application of insulation co-ordination for

ultra high-voltage technology 792.7 Factors affecting lightning overvoltages entering substations 80

2.7.1 Backflashover 812.7.2 Direct strike 842.7.3 Attenuation of lightning overvoltage 87

2.8 Methods of controlling lightning overvoltages 872.8.1 Location of surge arresters 87

2.9 Conclusions 89References 89

3 Applications of gaseous insulants 93H.M. Ryan3.1 Introduction 933.2 Atmospheric air clearances 96

3.2.1 Test areas 963.2.2 Sphere gaps 1003.2.3 Spark gaps 1003.2.4 Overhead lines and conductor bundles 1053.2.5 Guidelines for live working 110

3.3 Other gases 1113.4 Switchgear and GIS 113

3.4.1 Introduction 1133.4.2 Arc extinction media 116

viii High-voltage engineering and testing

3.4.3 General dielectric considerations 1193.4.4 Performance under contaminated conditions 1303.4.5 GIS service reliability 1313.4.6 Gas-insulated transmission lines (GIL) 1333.4.7 Vacuum switches 134

3.5 System modelling for switchgear design applications 1363.5.1 Field analysis techniques 1363.5.2 Prediction of breakdown voltages 143

3.6 Summary 148Acknowledgements 148References 149

4 HVDC and power electronic systems 153Gearoid o hEidhin4.1 Introduction 1534.2 HVDC transmission a brief overview 1534.3 General principles 1554.4 Main components of HVDC links 156

4.4.1 Thyristor valves 1564.4.2 Converter transformer 1584.4.3 Control equipment 1624.4.4 AC filters and reactive power control 1634.4.5 Smoothing reactor and DC filter 1654.4.6 Switchgear 1664.4.7 Surge arresters 1684.4.8 Valve cooling 1684.4.9 Auxiliary supplies 169

4.5 Converter building 1694.6 VSC HVDC 1724.7 Economics 1764.8 Power electronic support for AC systems 177

4.8.1 Static var compensators (SVCs) 1784.8.2 STATCOM 1794.8.3 Series compensators 1804.8.4 Unified power flow controller (UPFC) 182

4.9 Power electronics for industrial applications 1834.10 Conclusion 183References 185

5 The implications of renewable energy on grid networks 187Adrian Wilson5.1 Introduction 1875.2 Drivers for renewable energy 187

5.2.1 Fossil fuel 1875.2.2 Nuclear fuels 188

ix

5.3 UK renewable energy resources and technology 1885.3.1 Power transfers 1885.3.2 Wind resources 1885.3.3 Wave resources 1895.3.4 Tidal resources 1905.3.5 Biomass resources 1935.3.6 Network implications from remote resource locations 1935.3.7 Generator technologies conventional power stations 1935.3.8 Generator technologies full converter wind turbine 1955.3.9 Generator technologies partial converter wind turbine 1955.3.10 Generator technologies wave machines 1955.3.11 Generator technologies tidal machines 1955.3.12 Generator technologies biomass-fed generators 1965.3.13 Generator technologies microgeneration 196

5.4 Renewable generator technologies network implications 1965.4.1 Cost of connections 1965.4.2 Voltage rise 1975.4.3 Load flow 1975.4.4 Fault level 1975.4.5 Power quality 1985.4.6 Network extensions 1985.4.7 Regulation 1985.4.8 Grid Code issues 199

5.5 Value of energy 1995.6 Solutions for renewable energy 200

5.6.1 Voltage rise 2005.6.2 Fault level 2005.6.3 Fault current limiters 2015.6.4 Principles of superconducting fault current limiters 2015.6.5 Fault current limiters 2025.6.6 Resistive fault current limiters 2025.6.7 Shielded core fault current limiters 2035.6.8 Pre-saturated core fault current limiters 2035.6.9 Load flow 2055.6.10 Energy storage 2055.6.11 Distributed intelligence in networks 206

5.7 Conclusions 206References 206Postscript note by H.M. Ryan 209

6 High-voltage cable systems 211A.L. Barclay6.1 Introduction 2116.2 Elementary theory 212

6.2.1 Voltage, electric field and capacitance 2126.2.2 Current, magnetic field and inductance 214

x High-voltage engineering and testing

6.3 Historical development 2146.3.1 Early telegraph cables 2156.3.2 Early lighting systems 2156.3.3 Flexible cables 2156.3.4 Impregnated cables and the renaissance of high voltage 2166.3.5 Pressure-assisted (gas) cables 2166.3.6 Fluid-filled cables 2176.3.7 Polymeric cables 2176.3.8 Polypropylene-paper laminate 218

6.4 Features of real cables 2186.4.1 The conductor 2186.4.2 The insulation system 2226.4.3 Multi-core and multi-function cables 2286.4.4 Outer layers 2296.4.5 Installation 232

6.5 Current ratings 2346.5.1 Time-dependent ratings 2356.5.2 Factors affecting ratings 236

6.6 Accessories 2436.6.1 Terminations 2436.6.2 Joints 2466.6.3 Other accessories 249

6.7 Direct current and subsea cable systems 2496.7.1 Applications of AC and DC transmission 2496.7.2 Subsea cable configurations 2506.7.3 Insulation systems 2526.7.4 Manufacture 2546.7.5 Installation 2556.7.6 Accessories 255

6.8 Standards 2566.9 Testing 258

6.9.1 Development testing 2586.9.2 Type testing 2596.9.3 Prequalification testing 2606.9.4 Factory acceptance testing 2616.9.5 After-laying tests 2626.9.6 In-service monitoring 2666.9.7 Testing for periodic maintenance 2676.9.8 Fault location 268

6.10 Future directions 269References 271

xi

7 Gas-filled interrupters fundamentals 275G.R. Jones, M. Seeger and J.W. Spencer7.1 Introduction 2757.2 Principles of current interruption in HV systems 275

7.2.1 System-based effects 2777.2.2 Circuit-breaker characteristics 280

7.3 Arc control and extinction 2817.3.1 Gas-blast circuit-breakers 2837.3.2 Electromagnetic circuit-breakers 2857.3.3 Dielectric recovery 287

7.4 Additional performance affecting factors 2887.4.1 Metallic particles 2897.4.2 High-frequency electrical transients 2907.4.3 Trapped charges on PTFE nozzles 290

7.5 Other forms of interrupters 2927.5.1 Domestic circuit-breakers 2927.5.2 Oil-filled circuit-breakers 2937.5.3 Vacuum interrupters 293

7.6 Future trends 2947.6.1 Other gases 2957.6.2 Material ablation and particle clouds 2977.6.3 New forms of electromagnetic arc control 2987.6.4 Direct current interruption 299

References 300

8 Switchgear design, development and service 303S.M. Ghufran Ali8.1 Introduction 303

8.1.1 SF6 circuit-breakers 3038.1.2 Sulphur hexafluoride 305

8.2 Interrupter development 3058.2.1 Two-pressure system 3068.2.2 Single-pressure puffer-type interrupters 306

8.3 Arc interruption 3108.3.1 Fault current 3108.3.2 Capacitive and inductive current switching 3128.3.3 Reactor switching 3148.3.4 Arc interruption: gas-mixtures 315

8.4 Third-generation interrupters 3168.5 Dielectric design and insulators 3188.6 Mechanism 3188.7 SF6 live- and dead-tank circuit-breakers 319

8.7.1 Basic GIS substation design 3198.8 Opening and closing resistors/metal-oxide surge arresters 324

8.8.1 Opening and closing resistors 324

xii High-voltage engineering and testing

8.8.2 Closing resistors/metal-oxide surge arresters 3258.8.3 Main features of metal-oxide surge arresters (MOSA) 326

8.9 Disconnector switching 3278.10 Ferroresonance 3288.11 System monitoring 330

8.11.1 Monitoring during installation and in service 3308.11.2 Continuous monitoring 3318.11.3 Periodic monitoring 331

8.12 Insulation co-ordination 3328.12.1 Introduction to appendices 332

8.13 Further discussions and conclusions 334Acknowledgements 335References 336Appendices 337

A Some historic observations 337B SF6 circuit-breakers in the UK plus a perspective from USA 340C Relevant strategic IEC Standard reports 342D Update of some recent CIGRE activities relating

Appendices D and E to Substations (SC B3) and also(SC B5) compiled from CIGRE publications by H.M. Ryan 343

E Residual life concepts, integrated decision processes forsubstation replacement and an overview of CIGRE workon AM themes compiled by H.M. Ryan 349

9 Distribution switchgear 355B.M. Pryor9.1 Introduction 3559.2 Substations 357

9.2.1 Substation types 3579.2.2 Substation layouts 359

9.3 Distribution system configurations 3619.3.1 Urban distribution systems 3619.3.2 Rural distribution systems 363

9.4 Ratings 3649.4.1 Rated current 3659.4.2 Rated short-circuit-breaking current 3659.4.3 Rated short-circuit-making current 3659.4.4 Rated asymmetrical breaking current 3659.4.5 Rated short-time current 3659.4.6 Rated voltage 3669.4.7 Rated insulation withstand levels 3669.4.8 Rated transient recovery voltage 366

9.5 Switching equipment 3669.5.1 Circuit-breakers 3679.5.2 Distribution circuit-breaker types 3699.5.3 Disconnectors 376

xiii

9.5.4 Earth switches 3789.5.5 Switches 3789.5.6 Switch disconnector 3799.5.7 Switch fuse 3799.5.8 Fuse switch 3799.5.9 Fuses 3809.5.10 Contactors 3829.5.11 Ring main units 382

9.6 Circuit protection devices 3839.6.1 Surge arresters 3839.6.2 Instrument transformers 385

9.7 Switchgear auxiliary equipment 3879.8 SF6 handling and environmental concerns 387

9.8.1 SF6 breakdown products 3879.8.2 SF6 environmental concerns 388

9.9 The future (as perceived in 2000 and again in 2011) 3899.9.1 The future 1 by B.M. Pryor in 2000 3899.9.2 The future 2 by H.M. Ryan in 2011 391

Disclaimer 396Summary 396References 397Appendices by H.M. Ryan 398

A Additional CIGRE references 398B Distribution systems and dispersed generation

(after CIGRE [8]) summary of key CIGRE informationmainly from SC C6 2011 AGM [8] compiled by H.M. Ryan 399

10 Differences in performance between SF6 and vacuumcircuit-breakers at distribution voltage levels 407S.M. Ghufran Ali10.1 Introduction 40710.2 Circuit-breaker 40710.3 Vacuum circuit-breaker 40810.4 SF6 gas circuit-breakers 40910.5 Puffer circuit-breaker 40910.6 Rotating-arc circuit-breaker 41210.7 Auto-expansion circuit-breaker 41210.8 Operating mechanism 41310.9 Choice of correct circuit-breaker for special switching duties 41310.10 Capacitive and inductive current switching 41410.11 Circuit-breakers for generator circuit switching 415

10.11.1 DC offset 41610.11.2 Current chopping and reignition 416

10.12 Synchronised switching 41610.13 Conclusions and some future developments 417

xiv High-voltage engineering and testing

CIGRE perception of future developments: prepared andcompiled by H.M. Ryan 418

Acknowledgements 419Bibliography 420Appendices 421

A Relevant strategic IEC Standard reports 421B The impact of new functionalities on substation design

(relating to CIGRE published work) abridged andcompiled by H.M. Ryan 422

11 Life management of electrical plant: a distribution perspective 425John Steed11.1 Introduction 42511.2 Reliability 426

11.2.1 Sources of data 42611.2.2 Typical distribution company requirements for data 42811.2.3 Case studies using data 42811.2.4 The bath tub curve 43011.2.5 Practical example distribution transformers 43111.2.6 Human factors in plant reliability 43211.2.7 Conclusions on reliability 434

11.3 Condition monitoring 43511.3.1 Definitions 43511.3.2 Benefits of condition monitoring 43511.3.3 Application to equipment 43611.3.4 What condition monitoring information can tell us

about asset management 44511.3.5 Condition assessment leading to asset replacement 44711.3.6 The new working environment users requirements 44911.3.7 Condition monitoring the future 450

11.4 Plant maintenance 45011.4.1 General techniques 45011.4.2 Enhanced maintenance 45211.4.3 Reliability-centred maintenance (RCM) 45311.4.4 Condition-based maintenance (CBM) 454

11.5 Working plant harder 45511.5.1 Towards a risk-based strategy the reasons why 45511.5.2 Risk assessment FMEA and FMECA 45511.5.3 Working switchgear harder 45711.5.4 Working transformers harder 457

11.6 Future trends in maintenance 45811.7 A holistic approach to substation condition assessment 45911.8 Retrofit, refurbish or replace? 46011.9 Current challenges 46011.10 A standard for asset management 462

xv

11.11 The impact of smart grids on asset management 46311.12 Information management 46311.13 Conclusions 464References 464

12 High-voltage bushings 467John S. Graham12.1 Introduction 46712.2 Types of bushings 467

12.2.1 Non-condenser bushings 46712.2.2 Condenser bushings 469

12.3 Bushing design 47212.3.1 Air end clearance 47312.3.2 Oil-end clearance 47712.3.3 Radial gradients 478

12.4 Bushing applications 47812.4.1 Transformer bushings 47812.4.2 High-current bushings 48112.4.3 Direct connection to switchgear 48112.4.4 Switchgear bushings 48312.4.5 Direct current bushings 484

12.5 Testing 48612.5.1 Capacitance and dielectric dissipation factor

measurement 48712.5.2 Power frequency withstand and partial discharge

measurement 48712.5.3 Impulse voltage tests 48912.5.4 Thermal stability test 48912.5.5 Temperature rise test 49012.5.6 Other tests 490

12.6 Maintenance and diagnosis 490References 492

13 Design of high-voltage power transformers 495A. White13.1 Introduction 49513.2 Transformer action 49513.3 The transformer as a circuit parameter 49713.4 Core- and shell-form constructions and

components 49813.4.1 The core 49913.4.2 The windings 50313.4.3 Cooling 50813.4.4 Insulation 509

xvi High-voltage engineering and testing

13.4.5 Tank 51013.4.6 Bushings 51013.4.7 On-load tap-changer 511

13.5 Design features 51213.5.1 Dielectric design 51213.5.2 Electromagnetic design 51513.5.3 Short-circuit forces 51713.5.4 Winding thermal design 518

13.6 Transformer applications 51913.6.1 Power station transformers 52013.6.2 Transmission system transformers 52113.6.3 HVDC convertor transformers 52113.6.4 Phase-shifting transformers 52313.6.5 Industrial transformers 52513.6.6 Railway transformers 526

13.7 A few predictions of the future 527References 528

14 Transformer user requirements, specifications and testing 529S. Ryder and J.A. Lapworth14.1 Introduction 52914.2 Specification of user requirements 530

14.2.1 Need for user specifications 53014.2.2 Functional and design specifications 53014.2.3 Specifications and standards 53114.2.4 Specification content 53114.2.5 Guidance on specifications 535

14.3 Supplier selection 53514.3.1 Industry changes 53514.3.2 Timing 53514.3.3 Format 53514.3.4 Aims 53614.3.5 Main elements of process 536

14.4 Testing 53814.4.1 Classification of tests 53814.4.2 Performance tests 53914.4.3 Thermal tests 54014.4.4 Dielectric tests 54214.4.5 Short-circuit withstand 54714.4.6 Condition assessment testing 548

14.5 Operation and maintenance 54814.5.1 Limitations on transformer life 54814.5.2 Preventive and corrective maintenance 54914.5.3 Time- and condition-based maintenance 549

xvii

14.5.4 Oil tests 55014.5.5 Electrical tests 550

14.6 Concluding remarks 551Bibliography 552

15 Basic measuring techniques 555Ernst Gockenbach15.1 Introduction 55515.2 Measuring system 55515.3 Amplitude measurements 561

15.3.1 Direct voltage 56115.3.2 Alternating voltage 56315.3.3 Impulse voltage 56715.3.4 Impulse current 571

15.4 Time parameter 57215.5 Measuring purposes 573

15.5.1 Dielectric tests 57315.5.2 Linearity tests 573

15.6 Summary 573References 574

16 Basic testing techniques 575Ernst Gockenbach16.1 Introduction 57516.2 Recommendations and definitions 57616.3 Test voltages 578

16.3.1 DC voltage 57816.3.2 AC voltage 58016.3.3 Impulse voltage 584

16.4 Impulse current 59116.5 Test conditions 59216.6 Summary 597References 598

17 Partial discharge measuring technique 599Ernst Gockenbach17.1 Introduction 59917.2 Physical background of partial discharges 60017.3 Requirements on a partial discharge measuring system 60417.4 Measuring systems for apparent charge 60617.5 Calibration of a partial discharge measuring system 60817.6 Examples of partial discharge measurements 608

17.6.1 Partial discharge measurement on high-voltagetransformers 609

xviii High-voltage engineering and testing

17.6.2 Partial discharge measurement and location onhigh-voltage cables 609

17.6.3 Partial discharge measurement on high-voltagegas-insulated substations 611

17.6.4 Development of recommendation 61317.7 Summary 614References 614

18 Digital measuring technique and evaluation procedures 615Ernst Gockenbach18.1 Introduction 61518.2 Requirements on the recording device 61618.3 Requirements on the evaluation software 61918.4 Application of digital recording systems 620

18.4.1 DC and AC voltage measurements 62018.4.2 Impulse voltage or current measurements 62118.4.3 Partial discharge measurements 623

18.5 Application examples of evaluation procedures 62618.6 Conclusions 629References 629

19 Fundamental aspects of air breakdown 631J. Blackett19.1 Introduction 631

19.1.1 History 63319.1.2 High-voltage laboratory testing 634

19.2 Pre-breakdown discharges 63519.2.1 Electron avalanches 63519.2.2 Streamer discharges 63519.2.3 Leaders 635

19.3 Uniform fields 63619.3.1 Electron avalanches in uniform fields 636

19.4 Non-uniform fields 64019.4.1 Direct voltage breakdown 64119.4.2 Alternating voltage breakdown 64219.4.3 Impulse breakdown 64419.4.4 Leaders 64419.4.5 Sparkover, breakdown, disruptive discharge 645

19.5 The U-curve 64719.5.1 The critical time to breakdown 654

19.6 The gap factor 65519.6.1 Test procedures 65619.6.2 Air gaps of other shapes 65819.6.3 Sparkover under alternating voltages 65919.6.4 Sparkover under direct voltages 659

xix

19.7 Flashover across insulator surfaces in air 66219.8 Atmospheric effects 664

19.8.1 Introduction 66419.8.2 Density effects 66419.8.3 Humidity effects 66519.8.4 Application of correction factors 66519.8.5 Air density correction factor k1 66619.8.6 Humidity factor correction k2 66619.8.7 Other atmospheric effects 668

19.9 New developments 66919.9.1 UHV at high altitudes 66919.9.2 Testing transformers 66919.9.3 Future work 672

References 672

20 Condition monitoring of high-voltage transformers 675A. White20.1 Introduction 67520.2 How do faults develop? 67620.3 Which parameters should be monitored? 67720.4 Continuous or periodic monitoring 67720.5 Online monitoring 67820.6 Degrees of sophistication for transformer monitors 67820.7 What transformer parameters can be monitored? 68120.8 Basic monitors 68220.9 On-load tap-changer (OLTC) module 68320.10 Insulation module 68520.11 Bushing module 68520.12 Cooling module 68720.13 Advanced features measurements and analyses 68820.14 Partial discharge monitoring 68920.15 Temperature measurement 69020.16 Chemical parameters 69020.17 Dielectric parameters 69120.18 Conclusions 69120.19 Further reading 692References 692

21 Integrated substation condition monitoring 693T. Irwin, C. Charlson and M. Schuler21.1 Introduction 69321.2 The evolution of condition monitoring systems 696

21.2.1 Periodic monitoring, 19601990 69721.2.2 Basic discrete online monitoring, 19901999 697

xx High-voltage engineering and testing

21.2.3 More intelligent discrete monitoring, 20002009 69821.2.4 Integrated substation condition monitoring

(2010 onwards) 69821.3 Objectives of condition monitoring 70021.4 Application to key substation equipment 70121.5 The substation environment 70121.6 Condition monitoring platform 703

21.6.1 Data acquisition systems 70421.6.2 Sensors and transducers 70521.6.3 Conversion module 70521.6.4 Interface module 70521.6.5 Data acquisition module 70521.6.6 Control PC module 70521.6.7 Communication module 706

21.7 Data acquisition, analysis and diagnostics 70621.7.1 Developing a common monitoring platform 70721.7.2 Specification of the node unit data acquisition

system 71121.8 GDM node unit overview 711

21.8.1 Data collection 71221.8.2 Predictive alarms and SF6 gas inventory 71321.8.3 Maintenance 715

21.9 CBM node unit overview 71621.9.1 Signals measured and recorded 71621.9.2 System alarms 71821.9.3 Data storage and display 719

21.10 PDM node unit overview 72221.10.1 PDM node unit data collection 72421.10.2 Node unit sequencer controls 72421.10.3 Node unit noise monitoring and alarm control 72521.10.4 Node unit system diagnostics 727

21.11 Power transformer monitoring 72721.11.1 Sensors for dissolved gas analysis 73121.11.2 Sensors for tap-changer monitoring 732

21.12 Cable monitoring 73221.12.1 Sensors for cable monitoring 733

21.13 Surge arrester monitoring 73421.14 ISCM system overview 736

21.14.1 Substation gateway 73621.14.2 CM module: PD monitoring 74021.14.3 CM module: gas density monitoring 744

21.15 ISCM systems going forward 74721.16 Concluding remarks 748Acknowledgements 749References 749

xxi

Appendices 751A Gas density monitoring transducer options 751B Circuit breaker monitoring data sampling rates 752C Partial discharge monitoring data sampling rates 752D Disconnector and earth switch monitoring data

sampling rates 752

22 Intelligent monitoring of high-voltage equipment withoptical fibre sensors and chromatic techniques 755G.R. Jones and J.W. Spencer22.1 The nature of intelligent monitoring 75522.2 The basis of chromatic monitoring 75622.3 Online monitoring of high-voltage equipment using

optical fibre chromatic techniques 75822.3.1 Optical fibre chromatic sensors 75822.3.2 Examples of chromatic optical fibre sensors for

high-voltage systems 75922.3.3 Time and frequency domain chromatic processing

of optical fibre sensor data 76122.4 Chromatic assessment of the degradation of high-voltage

insulation materials 76822.4.1 Chromatic characterisation of partial discharge

signals (M. Ragaa) 76822.4.2 Offline assessment of high-voltage transformer

oils with chromatic techniques (E. Elzazoug andA.G. Deakin) 773

22.5 Conclusions 780Acknowledgements 781References 781Appendix A 785

23 Some recent ESI developments: environmental, state of art,nuclear, renewables, future trends, smart grids and cyber issues 787H.M. RyanPreface 78723.1 Introduction 78823.2 International takeovers in UK power sector and possible impacts 791

23.2.1 Warning: kid gloves treatment 79323.3 Some aspects of renewable energy development in the UK 796

23.3.1 Energy-mix and perceived renewable energycosts (200410) 796

23.3.2 Renewable energy vs landscape calculations(The Sunday Times, 20/11/11) 799

23.3.3 UK energy storage: call to build a series of dams tostore power from wind turbines (after D. MacKay)(Jonathan Leake, The Sunday Times, 18/3/12) 800

xxii High-voltage engineering and testing

23.3.4 Press articles: Some very public energy discussions(commentaries on articles by D. Fortson et al.,The Times, 201012) 803

23.4 UK governments recent wind of change 80823.5 Nuclear power plants: recent events and future prospects 810

23.5.1 Fukushima nuclear accident: short-term impacton global developments 810

23.5.2 Future nuclear developments 81123.5.3 Future prospects of new-build nuclear plants overseas 815

23.6 Some aspects of carbon trading 81923.6.1 Coal-fired to co-fired stations in the UK to avoid

paying rising climate taxes (after Danny Fortson,The Sunday Times, Energy Environment, 26/2/12) 820

23.6.2 Frying note: storage energy back-up 82323.7 A new green technology: carbon capture and storage (CCS)

(Tim Webb, The Times Business Dashboard, 29/3/12) 82523.7.1 Some committed CCS developments worldwide 825

23.8 Recent developments in UK Network/European Grid links 83323.8.1 New UK/International DC cable links 83323.8.2 Proposal case for a North Sea super grid (NSSG) 83323.8.3 Challenges facing AC offshore substations for

wind farms and preliminary guidelines for designand construction 839

23.8.4 Network upgrades and some operational experiences 84423.9 Some UK operational difficulties with wind farms 845

23.9.1 Wind farms paid 900,000 to switch off (1) 84523.9.2 Storm shut-down is blow to the future of wind

turbines (2) (Jon Ungoed-Thomas and JonathanLeake, The Sunday Times, 11/12/11) 846

23.9.3 Energy speculators now bet on wind farm failures (3)(J. Gillespie, The Times, December 2011) 847

23.9.4 Millions paid to wind farm operators to shut down (4) 84823.9.5 Clean energy financial support; impact of Scotland

leaving the Union after an independence vote in2014 (5) (Karl West, The Sunday Times, 22/1/2012) 850

23.9.6 Crown Estate: Scottish assets worth arguing overin independence debate [6] (Deirdre Hipwell,The Times, 21/06/2012, pp. 345) 851

23.9.7 Some poor wind farm performance statistics 85223.9.8 Flying wind farms pluck energy out of the blue,

states Gillespie in The Sunday Times(08/07/12, p. 7) 854

23.10 UK air-defence radar challenged by wind turbines 85423.11 Noise pollution: wind turbine hum (The Sunday Times,

18/12/11) 85523.12 Balancing fluctuating wind energy with fossil power stations 857

xxiii

23.13 Future developments including smart grids 85823.13.1 US study by Gellings et al. from EPRI [30] (1) 86023.13.2 Some CIGRE perspectives of energy activities and

future development [35] (2) 86323.14 Discussion and conclusions 877

23.14.1 Discussion 87723.14.2 Conclusions 890

References 891Appendices 895

A Cyber-crime and cyber-security 895B Cyber-crime 895C CIGRE: Treatment of information security for electric

power utilities 901

Index 907

xxiv High-voltage engineering and testing

Contributors

S.M. Ghufran AliFormer Chief SwitchgearEngineerPB Power Ltd

A.L. BarclayPrincipal EngineerKinectrics International Europe

J. BlackettIndependent High-Voltage Consultant

C. CharlsonTeam Leader Diagnostics andMonitoringSiemens Transmission andDistribution LtdInfrastructure and Cities SectorSmart Grid

I.A. ErinmezIndependent Power SystemsConsultant

Ernst GockenbachSchering-Institut for High-VoltageEngineeringLeibniz Universitat Hannover

John S. GrahamChief Engineer - BushingsSiemens Transmission andDistribution Ltd

Gearoid o hEidhinALSTOM GRID Power Electronics

T. IrwinIndependent High-Voltage andCondition Monitoring Consultant

G.R. JonesEmeritus ProfessorCentre for Intelligent MonitoringSystemsDepartment of Electrical Engineeringand ElectronicsUniversity of Liverpool

John LapworthSenior Principal EngineerDoble Power Test

B.M. PryorPower System Services Ltd

H.M. RyanMcLaren ConsultingEmeritus ProfessorElectrical and Electronic EngineeringUniversity of Sunderland

S. RyderPrincipal EngineerDoble Power Test

M. SchulerSiemens AGIC SG EA SYS LM SM

M. SeegerSenior Principal ScientistABB Schweiz AGCorporate ResearchRD - V3

J.W. SpencerCentre for Intelligent MonitoringSystemsDepartment of Electrical Engineeringand ElectronicsUniversity of Liverpool

John SteedHM Principal Specialist InspectorElectrical NetworksHealth & Safety Executive

A. WhitePower Transformer Consultant

Adrian WilsonApplied Superconductor Ltd

xxvi High-voltage engineering and testing

Preface

H.M. Ryan

It is now more than a decade since High-Voltage Engineering and Testing (HVET),2nd Edition, was published in the IEE Power and Energy Series. The origins of theHVET books, and also the equally successful accompanying International SummerSchool series by the same title over the period 19932008, is briefly recorded andexplained at the end of this preface to provide the readers with valuable backgroundinformation expressed in both historical and technical contexts. In the past decade,significant changes have continued to take place in the electricity supply industry inthe UK and worldwide, and many more strategic and very costly network devel-opments anticipated in the very near future will be discussed in this latest edition.There has been much talk in the past few years of smart-grids and enhancedintelligent energy networks of the future, i.e., within the next one to two decades.However major under-investment in the sector for many years, linked to the recentworld recession or economic downturn, will certainly delay completion andfull integration of these diverse/complex/extremely costly proposed technologicaladvances.

This new third edition of HVET will again provide a valuable broad overview ofthe developments in the sector including renewable energy (windfarms, biomassetc.). Cost, environmental and operational aspects are covered. Modern substationcondition monitoring strategies for switchgear, transformers and cables are discussedand new insulation co-ordination (IC) technologies are discussed adopted usinghigher performance arresters for new ultra high-voltage AC transmission substationsin China, India and Japan (operating at voltages 1,100 kV). Fundamental designconcepts, special strategic network developments, asset management issues at EHVand other special matters are also discussed.

The book also touches on how network equipment and systems operate and aremonitored and managed at this time and can perhaps best be managed in thefuture. The important roll of CIGRE in the energy sector via its extensive StudyCommittee structure (see Table 1, Introduction), and production of TechnicalBrochures, is also explained. Consider now the first two of several strategic newenergy themes discussed in this edition of HVET:

1. Recently, there have been political concerns expressed by MPs and mediacoverage commenting that Britains energy markets are inherently-flawedand that anti-competitive practices may be forcing up the costs paid by

consumers. Five of Britains energy companies are facing mounting pressureto cut fuel prices after recent figures from Ofgem (the industry regulator)showed the average profits they earned, per household, rose 40% one recentwinter to the highest figure for five years. This comes at a time of huge profitsfor the energy companies several of whom are now (at least partly) owned byoverseas companies, for example EDF Energy and GDF Suez (French owned),E.ON and RWE (German owned), Enel (Italian owned). Ofgem indicatedrecently that profit margins earned by the so-called Big Six Companies British Gas, Scottish Power, EDF Energy, npower, Scottish and SouthernEnergy (SSE) and E.ON increased from 75 per average dual-fuel custo-mer in November 2009 to 105 at the start of February 2010.

Energy bills continue to rise and UK consumers will also be footing the2535 billion bill to upgrade the UKs energy network for the next four tofive decades. In 2013, Ofgem indicated that householders will be paying offthis huge cost, via levies, over a 45 year period (instead of the existing periodof 20 years). Consequentially, it is projected, and claimed, that energy billswill reduce soon in the UK.

2. A study from the Energy and Climate Change Committee on the futureof Britains electricity networks has called for the introduction of a moreefficient smart grid, capable of intelligently managing demand andsupply. A member of this committee, P. Tipping, MP, said our existingregulatory and policy frameworks, along with grid infra-structure we relyon, were developed to serve the fossil-fuel economy of the twentieth century.The future looks very different and called for a review of the British Elec-tricity Trading and Transmission Arrangements, which have formed thefoundation for UK power activity since 2005. He also stated that by 2020,the UK network would need to accommodate a more diverse energy mix.1

Many strategic aspects will be dealt with in the new third edition of HVET. Inaddition, speculative new technologies and new techniques perhaps novel today,yet likely to become strategic and standard technology very soon for next gen-eration systems are also reported on. One example that could possibly fit this billis fault current limiters, which have been developed/researched for some yearsbut have not as yet achieved the commercial success that many predicted. Thissituation may well change dramatically in the next decade. Obviously a very strongstrategic contender in this category would be smart grids, referred to by some ascondition monitoring to achieve greatly improved electricity network commercialprofitability, management of demand, supply, etc. Electricity grid networks in UKand in many countries are still largely set up as for twentieth-century needs! Allareas of the energy sector need to draw on relevant lessons learned in other

1 At that time, the UK energy consumer was already concerned and disgruntled with the realisation thatthe seemingly ever-escalating domestic energy fuel bills would continue to rise indefinitely part ofthese payments contributing towards the highly subsidised future development to the UKs diverse-mixenergy network infrastructure.

xxviii High-voltage engineering and testing

appropriate sectors, for example telecoms. Technically, this is certainly a very goodtime for smart-grid changes as everyone is trying to work networks harder andmore efficiently. There are rich-pickings available to those who can interpretneeds and develop effective intelligent software systems, etc., capable of workingenergy networks, harder, safer, longer and more efficiently/profitably, and who cananticipate early enough what new techniques/methodologies are likely to play thebest strategic and economic roles in managing T&D networks better (technicallyand economically) in the very near future.

World events and reactions to several other important emerging energy issueswarrant and necessitate extended coverage/discussions on renewable and otherenergy issues in this third edition, partly because of the widespread unrest reported inthe UK press/media etc., on several short-term and longer-term energy-relatedissues. Similarly, because of apparent UK governments indecision concerningnuclear new-build plant vs renewables vs a recent new rush for gas initiative in thepost-Fukushima nuclear accident (2011) era and more significantly, the apparentlack of a coherent and consistent overall UK energy policy these and other strategicaspects are also covered in this new edition. Very important issues relate to technical,economic and security aspects linked to the current worldwide problems associatedwith cyber-crime, cyber-hacking, cyber-intrusion, etc. using malicious software.These aspects are covered, mainly in Chapter 23, with an indication given of thescale and frequency of the worldwide cyber issues, and how these issues are cur-rently being dealt with within the energy sector.

Finally, the extensive referencing of CIGRE Technical Brochure publicationsin this third edition of HVET has been done very deliberately. Perusal of appro-priate CIGRE Technical Brochures (TBs) can help empower the reader if he/sheuses them as an additional resource when reading refereed IET/IOP/IEEE, etc.,publications on similar themes. Sadly, in the UK, many higher degree researchersor engineering degree students doing final year projects have in the past failed tobe aware of, or to follow up effectively, extensive and valuable CIGRE TBs andElectra paper materials as they often felt little incentive to read, refer to or publishin these non-rigorously refereed journals from a research assessment publishingcredibility viewpoint. Fortunately these views are now changing worldwide, andhopefully also in the UK, as there is much valuable technical information to beobtained with this search approach as this writer has been urging students andacademics to do for 25+ years within HVET School and elsewhere.

In summary, the challenges ahead are great and the career opportunities for thenext generation of power engineer are very promising good luck.

Acknowledgements

Significant to the successes of both the HVET course over the period 19932008 andthe HVET book to date have been the excellent individual expert contributors to bothformats, each expert having been particularly active in his/her sector(s), includingESI, IEC Standards, design and manufacture, R&D, consultancy or testing aspects

xxix

and within the professional bodies IET/IOP/IEC/BSI/CIGRE, etc. The majority ofauthors in this third edition are also distinguished and active members of CIGRE,WGs, or IEC Committees or the famous Current-Zero-Club, restricted to worldexperts in Arc-Interruption. All are fully aware of the ongoing dynamic changes inthe energy and network sector, worldwide.

This Editor, who was also Chair of the successful IET/HVET Summer Schoolseries 19932008, is pleased to record his very grateful thanks to all HVET con-tributors and lecturers for their generous and committed support over the years(19932008) in passing on their expertise to the next generation of engineers in thissector.

In particular at this time, he also wishes to express his sincere thanks andgrateful appreciation to all contributors to this third edition HVET for giving theirtime so generously to prepare their valuable and strategic contributions, at a time ofheavy work commitments and other duties.

Hugh M. Ryan, Editor HVET 3rd Edition, 2013

Historical background to HVET books, Editions 1, 2 and 3

The first, second and now third editions of this HVET book developed from subjectmaterial initially prepared and delivered at the IET HVET International SchoolCourses covering the same subject areas (19932008). Interestingly, the InternationalHVET Course series covering High-Voltage, Engineering and Testing evolvedand developed in the UK following the strongly voiced concerns and wishes ofthe IEE membership at large during and following two UK IEE meetings onrelated topics that the writer chaired in 1991, one at CERL, Leatherhead the otherat IET Headquarters, Savoy Place, London. At, and subsequent to these events,there were

1. very strong concerns expressed at the diminishing UK expertise in the sector,particularly in HV measurement and traceability/testing

2. the strong wishes expressed by most of the IEE members in the audiences, atboth these events, to have suitable new training course(s) established on HVtesting, measurement and traceability, etc., developed, organised and madeavailable to facilitate the proper and appropriate training of the next gen-eration of HV experts in the UK and abroad, otherwise it was feared that muchof the expertise would be lost.

Note: To put these 1991 IEE membership concerns into perspective, it must berecognised that during the 1980s and 1990s many HV laboratories in both the oldand new universities in the UK closed and laboratory space often converted, intonew IT suites. Many of the larger machines in undergraduate laboratories were alsoremoved and progressively it was sometimes difficult to distinguish between uni-versity electrical departments and computing departments, as both were largelyresourced by many computers plus software simulation tools instead of powermachines, etc., or HV testing equipment. Similar savage cut-backs in the UK

xxx High-voltage engineering and testing

power engineering industrial manufacturing base reduced the popularity ofHV power engineering still further at that time.

Disappointingly, in recent years this power engineering downturn situation hascontinued fortunately with a few areas of outstanding expertise remaining culminating in the virtual ending of UK transmission switchgear manufacturing andcertain other traditional power engineering manufacturing capabilities. Now, in2013, the recent closure of a UK Bushing Manufacturing facility and also theClothier UHV Testing Laboratory complex, both located at Hebburn, UK, hasexacerbated the position even further. Consequently, the need for the latest versionof this HVET book is again timely, reflecting on traditional, new and anticipatedfuture strategic developments in the power engineering sector.

Historically, this writer (editor of editions 1, 2 and 3 of this HVET book)decided to prepare a report for the IEE Power Divisional Board on a proposednew HVET (High-Voltage Engineering and Testing) course, suggesting a slightlybroader scope for this proposed course, after some helpful discussions withcolleagues, who were later to become founder members of HVET CourseSteering Committee. The IEE Power Division approved this initiative and sup-ported the running this course annually, for the first several years (19932002).This International HVET Course Series (19932008) proved to be a success(commercially, educationally and technically) with more than 400 delegatescoming from more than 30 countries, and the HVET book 2nd Edition appearedin the IEE best seller lists. Therefore, it can truly be stated that this has been abottom-up initiative, from IEE members in the audiences at the above twotechnical meetings back in 1991 who were the real catalysts for starting HVET,in both course and book formats. This approach of using delegate feedbackcontinued to prove invaluable when checking, updating and maintaining theHVET course relevance year-on-year.

It had always been the policy of the IET HVET Course Organising Committee(19932008) to tweak the course delivery slightly each year and also to introducenew aspects and materials regularly, when felt to be appropriate, reflecting anychanges in the ESI and always listening and taking on board from the interactivetechnical discussions the views of the international delegates, fellow lecturers, etc.,regarding any possible improvements to course structure/themes and assessing theinterest in possible new area(s) to pick up on for the next year. Indeed, onespeculative-type lecture session was usually held each year, to introduce anddebate with course delegates one or two different speculative or new technicalaspects or drivers for the future in anticipation of likely new trends, and totouch-on how changes would affect the operation and economics of electricitynetworks of the future and equipment. Also considered were the operationalimplications and how these changes might be managed. This has been done on theHVET course by the course committee over several years, with themes such asadvanced condition monitoring, fibre optical monitoring, fibre, new developmentsin the UHV sector, evolving drivers and strategies for change in Electricity ESIs,global warming, carbon footprints, renewable energy, wind power, tidal, wave,solar, biomass, and so on! Also any relevant strategic updates or anticipated

xxxi

dynamic changes within ESIs or HV testing sectors worldwide were reported todelegates year on year, covering any recent IET/IEEE/IOP/CIGRE publicationsand including important changes to IEC Standards and relevant CIGRE TBs,Working Group (WG) reports, etc. Brief details of such developments and possiblestrategic changes were made available to delegates at the school each year andthe importance of IET/IEC/CIGRE activities touched on from a perspective ofempowering delegates in their chosen area of interest, or even broader issues.This was well received by delegates and who often remained in contact with courselecturers a long time after the school.

The HVET course, and its accompanying book, has been very well receivedboth nationally and internationally for many years. Consider just one tribute: anextract of a recent letter from the IET Chief Executive and Secretary, April 2008, toone retiring founder-member of the HVET Course Steering Committee. It states:

I am writing to you on behalf of the Institution of Engineering andTechnology in recognition of the outstanding contribution you have madeover the years to the High Voltage, Engineering and Testing Course. TheCourse has become our flagship power systems training school which hasinspired other sectors in the IET to emulate its formula. It is acceptedglobally that HVET sets the standard for other organisations providing thistraining and the sector has the highest regard for its quality and practicaldelivery. None of this would be possible without the exceptional con-tribution and energy of the volunteers behind it. It is with sadness thatI read that you have had to resign from the steering committee for healthreasons on the advice of your Doctor. Your presence among the team andIET staff will be missed as the Course continues to serve the engineeringcommunity.

Note: This writer considers the above comments to be an appropriate and accuratetribute to the individual and, in his humble opinion, it could equally well have beenwritten collectively for all the HVET committee and course lecturers, over theentire life of the HVET course up to that time (19932008). Many of these indi-viduals have also contributed to all three editions of the HVET book.

This clearly reflects their continuing commitment to passing on their expertiseto the next generation of workers in the sector! To them again, a big thank you.

xxxii High-voltage engineering and testing

Introduction

H.M. Ryan

This third edition comprises 23 chapters covering high-voltage engineering andtesting themes with many valuable references describing CIGRE work. Table 1 isset out at the end of this introduction to assist in understanding the range and scopeof individual CIGRE Study Committees (SCs) and associated terminology, whileTable 2 provides an abridged summary of recent strategic work in the transformersector by CIGRE (SC A2), which we will return to later.

Chapter 1 provides an authoritative coverage of Electric power transmissionand distribution systems by Dr Arslan Erinmez. In this, The progressive devel-opment from 1880s to date is described mainly with reference to the UK system, asmost systems around the world have gone through the same stages of developmentat and around the same time following technological, political and organisationaldevelopments which reflected the trends current at the time. Global developmentsare also reviewed together with several key factors, for example technical, orga-nisational structures that heavily influence the development and operation of thesenetworks. Design, security and operational and planning aspects are also con-sidered. Future developments and challenges: organisational, security, technicaland technological are discussed, including a large detailed list of conventional andnon conventional power electronic thyristor-controlled voltage regulators and otherdevices (also touched on in Chapters 4, 5 and briefly in Chapter 23 relating to usewith offshore-wind farms). The author also points out that although three phaseoverhead lines is still the usual method of interconnection, in cases where longtransmission distances and/or sea crossings are involved, HVDC transmission iseconomic despite the relatively higher costs of converter and terminal equipment.

Erinmez comments on HVDC transmission that is also used for inter-connecting utilities with different supply frequencies (e.g. 50/60 Hz) and in caseswhere an asynchronous link between systems is required. Back-to-back HVDCinterconnections have also been used with both converter stations situated in thesame site. Erinmez (Chapter 1) also reports that the rapid development of com-puting and communication systems has accelerated development strategies oftenreferred to as the so-called smart-grid initiatives.1

The author comments that smart-grid initiatives tend to focus on consumerdemand control, remote switching and metering aspects but considers that theycurrently suffer from inadequately defined objectives as well as protocols and

1 These are discussed further in Chapter 11 and in greater detail in Chapter 23 (section 23.13 andTables 23.923.14).

standards (this editor endorses these remarks). Further, Erinmez considers smart-grid initiatives, at transmission level, are more appropriate for special protectionand system control applications, whereas in distribution systems their applicationwill be subject to consumer approval and placement of privacy safeguards. He alsowarns that the use of Internet-based communications also exposes transmission anddistribution utilities to malicious attacks and cyber-hacking activity. These issues,which are likely to require increasing efforts to ensure robustness of systems tosuch threats, are considered further in Chapter 23, Appendix A.2

Erinmez in Chapter 1 points out that NGC is the first and largest fully priva-tised independent transmission utility in the world that has been subjected toorganisational and electricity market driven changes. As a result, it has been ableto utilise every available technology to address the challenges of facilitating com-petition and responding to the electricity market place. He outlines the leading roleof NGC in FACTS and HVDC development/applications and provides a briefsummary of both traditional and the new technology portfolio readily available toutilities (see section 1.6.2).

The important concept of insulation co-ordination (IC) of high-voltage andEHV AC systems is thoroughly covered in Chapter 2 (Irwin and Ryan), whileChapter 3 (Ryan) touches on a few important aspects of IC for UHV AC systemsrecently covered in CIGRE TBs 546 (2011) and 542 (2O13).* The more recentstudy, reproduced in a summarised form in Table 3.2, takes into account the state-of-the-art technology, with special reference to higher performance surge arresters.

*This review takes into account: the accumulated knowledge of various CIGRE working bodies; recentmeasured data of very fast temporary overvoltages (VFTO); and air gap dielectric characteristics incollaboration with CIGRE SC A3 and B3.

The emphasis in Chapter 3 relates to the application of gaseous insulants toswitchgear, mainly SF6 in GIS/GIL, and outlines criteria for EHV/UHV testinglaboratories, dielectric modelling studies enabling optimal dielectric design ofcircuit-breaker units etc. to be produced and minimum breakdown voltages to bepredicted, often without recourse to extensive and costly development testing. Ryan(Chapter 3) also considers that the subtle nuances of the complex fundamentalarc-physics measurements in SF6, systematic interrupter high-current performanceassessments and development, and effective dielectric design of practical interrupterlayouts fully justified the effective use of the complementary skills of a group ofexperts in this sector when making decisions regarding the final commercial SF6GIS and circuit-breaker designs that subsequently achieved outstanding interruptionand dielectric and in-service performance. These were systematically developedfrom a four-break interrupter design to a two-break design, and eventually to thedesign of one-break interrupter in a remarkably short timescale (see Chapter 8).3

2 The reader is encouraged to use Chapter 1 as a major reference point source when consideringsmart grids of the future and cyber-crime, cyber hacking/malicious attacks.3 The supporting R&D for these developments, carried out towards the end of the twentieth century,has been extensively reported in the literature, by S.M.G. Ali, G.R. Jones, D. Lightle, H.M. Ryan, et al.(see also Chapters 7, 8, 2123).

2 High-voltage engineering and testing

Chapters 2, 3 and 8 also discuss strategic aspects relating to UHV substationdesign; it should be recognised that, because only a few UHV AC transmissionnetworks exist and have only recently entered service worldwide, at 1.1 MV or1.2 MV (e.g. in China and in India respectively):

1. The background of the technical specifications for substation equipmentexceeding 800 kV AC [CIGRE TB 546 (2011)] is less well defined than atlower system voltage levels, where robust standards already exist.

2. Only limited experimental/technical/specification information exists forUHV substation equipment, and two recent CIGRE Technical BrochuresTB 546 and TB 542 are currently of strategic importance and will remainso till the time more robust full IEC specifications are developed forUHV systems: TB 546: This study has collated the limited available background UHV

information and has presented interim recommendations for the interna-tional specification and standardisation of UHV equipment [in CIGRETechnical Brochure TB 456-WG A3.22 (2011)];

TB 542: This study discusses the insulation co-ordination practices in threeUHV AC Systems [TB 542-WG A4.306 (2013)] at:[a] the 1100 kV Jindongnan Substation (China),[b] the 1100 kV Shin-Haruna Testing Station (Japan) and[c] the 1200 kV Bina Testing Station (India).

TB 542, a follow-on study from the work of TB 546 (2011), has describedfurther useful measures and simulation studies. It considers that overvoltage miti-gation techniques such as higher performance arresters can drastically reducelightning overvoltage levels. The CIGRE review (WG A4.306) intimated that it willprepare recommendations, such as recent practices of insulation coordination basedon the higher performance surge arresters, estimation of overvoltage and airclearance, and these will be proposed for future revisions of the application guideIEC 60071-2 (1996) and IEC apparatus standards.

Insulation co-ordination (IC) is a very complex subject area and one ofimmense strategic technical/economic importance to the network design andeffective operation. Consequently, here again it is always strongly recommendedto use the complementary skills of a group of experts in this sector when makingfinal design decisions. Aspects such as IC (including the use made of surgearresters at UHV levels), switching phenomena for circuit-breakers, dis-connectors and earthing switches and testing are also considered in Chapters 2and 8. In situations such as this, refinements and knowledge updates will continueas service experience with UHV systems increases and until full robust IECStandards are produced. Again, CIGRE technical activities are considered inmany chapters of this book and in Table 1 at the end of this introduction section,the reader is provided with useful backgroud to the wide range of CIGRE tech-nical activities: CIGRE key: SC, Study Committee; WG, Working Group andJWG, Joint Working Group; TF, Task Force; TB, Technical Brochure; TR,Technical Report; SC, Scientific Paper.

Introduction 3

Chapter 3 [CIGRE TB 546] informs the reader that, at present, UHV tech-nology is characterised by a need to minimise the sizes, weights, costs andenvironmental impacts of the overhead lines and substations and hence to developprojects which are feasible from economic, societal and technical points of view.This interim utility/CIGRE strategy is discussed together with a brief explanation ofhow, by means of the application of a number of new technologies and new ana-lysis techniques, utilities are able to reduce the dielectric requirements to valuesthat lead to much smaller structures.

This results in insulation voltage levels at UHV that are not far from the levelsapplied at the 800 kV class. For example, in Japan the towers of the UHV OH linesare only 77% of the size that would be necessary if insulation levels would havebeen extrapolated directly from lower voltage class. Chapter 3 goes on to detailother strategic aspects considered in CIGRE TBs 546 or 542. Three importantaspects included in this list, which are also touched on in Chapters 2, 8 andTable 3.2 of Chapter 3, are:

1. the use of closing resistors to control slow front overvoltages (SFO)2. the use of opening resistors to reduce opening SFO3. damping resistors to be used in GIS disconnectors to reduce the amplitude of

VFTO (very fast transient overvoltage) phenomena which otherwise mayexceed the lightning impulse withstand voltage of the switchgear

4. mitigation techniques such as higher performance arresters can dramaticallyreduce the lightning overvoltage levels [TB 542-WG A4.306 (2013)].

Further, the reader should note that, while some experts are concerned with thepresent IC situation, everyone should be at least partly reassured that anotherCIGRE expert Working Group [TB 542-WG A4.306] has had deliberations con-cerning the vital issue of field testing techniques on UHV substations during con-struction and operation. An updated CIGRE TB provisionally entitled FieldTesting Technology on UHV Substation Construction and Operation was due to beissued by CIGRE by late 2012. However, the work on this proposed documentmight well have been incorportated into TB 452-WG A4.306 (2013).

Chapter 4 by Gearoid o hEidhin considers HVDC4 and power electronicsystems that are now widely used in modern networks and will certainly findincreased application as the industry moves towards smart grids and enhancedtransmission and distribution networks of the future, that is within the next one ortwo decades. This chapter provides comprehensive material and informs thereader how modern HVDC converter stations are designed, general principles(including basic components); details of main components of HVDC linksincluding converter transformer, McNeill HVDC station designs; control systemsand AC filters and reactive power control; smoothing reactor and DC filters;switchgear; valve cooling techniques; surge arrester equipment; typical layouts ofcontrol building and valve hall; development of voltage-sourced converters(VSCs) and other devices; environmental aspects; adherence to standard

4 The term gas circuit-breakers (GCBs) has recently been used when discussing HVDC systems in theliterature.

4 High-voltage engineering and testing

specifications and more. Power electronic support for AC systems is also brieflycovered in Chapter 4.

Note: A generous list of valuable reference sources is provided for further reading and current/future CIGRE publications are available from IET/IEEE/CIGRE and can be regularly monitored, simi-larly IET/IEEE/IEC Standards, etc. In particular, CIGRE sources (see Table 1 for details of StudyCommittees) provide many regular strategic Technical Brochures (TBs) on important worldwide issuesin the sector (e.g. see appendices to Chapters 8, 9, 10 and elsewhere in this book).

The theme of back-to-back HVDC interconnections being used, withboth converter stations situated in the same site, has already been touched on inChapter 1. This is considered further in Chapter 4, by the author of HVDC andpower electronic systems, who points out:

1. If the function of a HVDC transmission scheme is to transfer power over a longdistance, then it will invariably use a high direct voltage. Most modernschemes use voltages up to 800 kV for overhead lines, while cables havebeen approaching voltages up to 600 kV progressively over the past 20 years.

2. Converter stations can be roughly characterised into two groups:(i) back-to-back converters using low direct voltage and high current typically

20250 kV and 2.55 kA(ii) long-distance transmission schemes using higher direct voltages and more

moderate current typically 300800 kV and 14 kA.

Notes:1. For back-to-back schemes, the author points out that the pressure to use HV

disappears and the voltage used is the lowest voltage at which the requiredpower can be transferred (within the limitations of the converter valves).

2. Economic HVDC power transfer, for example from a remote power source toan urban area: a DC line is significantly cheaper to build than an AC line tocarry the same power and additionally, if the distance is great enough, thiseconomy is sufficient to pay for costs of the converter stations at both ends ofthe line. Chapter 4 quotes the break-even distance as approximately 800 km foran overhead line and 50 km for a cable.

Chapter 5 by Adrian Wilson discusses the implications of renewable energy on gridnetworks and provides a valuable overview of the subject. The reader should alsobe aware that:

1. Another recent IET book Power and Energy Series 63, entitled EnergyStorage for Power Systems, 2nd edn, 2011, by A. G. Ter-Gazarian provides avaluable additional resource and contains 144 references.

2. Chapter 23 of the present book provides several interesting UK press/publicperceptions as to the recent effectiveness of renewable energy wind farm sup-plies in the UK, the high UK energy costs to the British Public, customer fuelpoverty and several other strategic aspects relating to the future energy strategyof the UK government including those for new-build nuclear, following onfrom the aftermath of the Fukushima nuclear accident of 2011.

Introduction 5

Basic cable designs and theory are covered in Chapter 6, by A. Barclay, with somebrief supplementary offshore wind farm material touching on EU North Sea Energygrid aspirations and other recent applications that plan to use modern low-losssuperconducting cable designs being briefly touched on in Chapter 23. Interest-ingly, CIGRE Table 2, in this introduction, indicates that Japanese R&D hastargeted 2020 for the commercial deployment of high-temperature superconductingtransformers in power systems.

Chapters 710 cover circuit-breaking aspects. Chapter 7, by G.R. Jones,M. Seeger and J. Spencer, provides an excellent comprehensive fundamentaltreatment of gas-filled interrupters and this is followed, respectively, by thoroughtreatment and reviews of high-power SF6 switchgear design development andservice (Chapter 8, by S.M. Ghufran Ali, Distribution switchgear; Chapter 9, byB.M. Pryor, Differences in performance between SF6 and vacuum circuit-breakers;Chapter 10, by S.M. Ghufran Ali).

The subtle nuances of the complex fundamental arc-physics measurements inSF6 (for example by Professor G.R. Jones and his group at CIMS, Department ofElectrical and Electronics, University of Liverpool and by Reyrolle switchgear stafftowards the end of the twentieth century), the systematic interrupter high-currentperformance assessments and development, and effective dielectric design of practicalinterrupter layouts fully justified the effective use by Reyrolle of the complementaryskills of a group of experts in this sector, when making a late decision regarding thefinal worldclass commercial SF6 designs that subsequently achieved outstandingcircuit-breaker interruption, dielectric and in-service performance. High-power com-mercial interrupter designs were speedily and systematically developed from four-break interrupter/phase to two-break interrupter/phase and quickly to one-break/phasecommercial interrupter design, as reported by S.M. Ghufran Ali, G.R. Jones et al.These collaborative developments are considered further in Chapter 3.

It must be stressed that vital partnerships, such as mentioned above, betweenuniversities and the power industry, are of even more strategic importance now in thetwenty-first century, and in the case of the University of Liverpool it was verypleasing for this writer to note that a major Chinese electrical engineering firm,the Pinggao Group (a direct subsidiary of the Chinese State Grid) is to invest1.5 million in research at the University of Liverpool over the next five years.Pinggao is one of Chinas major manufacturers, engaged in the design and produc-tion of switchgear and power plant equipment at HV, EHV and UHV voltage levels.It appears that the framework agreement will see the university build on theexisting provision of technological support for the development and optimisation ofPinggaos electrical apparatus, in order to supply reliable electrical equipment as Chinamoves towards developing smart grids and enhanced energy networks of the future.Welcoming this agreement while on a visit to University of Liverpool, QuingpingPang, Pinggao, Vice General Manager, ended his statement by stating: We hope thetechnologies developed here will be successfully used for the benefit of all society.5

5 Without doubt this agreement provides further robust evidence of the high quality of expertise availableat some UK universities in this case at the University of Liverpool, UK, Electrical Engineering andElectronics Department/Centre for Intelligent Monitoring Systems.

6 High-voltage engineering and testing

Much valuable supplementary strategic CIGRE switchgear-related materialis also included in the appendices of Chapters 810, mostly from appropriateCIGRE (TB) sources, thanks to its effective and wide-ranging worldwide workinggroup activities infrastructure as set in Table 1, at the end of this introductionsection. The reader is provided with further strategic CIGRE information inChapter 23.

Chapter 11, by John Steed, considers Life management of electrical plant: adistribution perspective. Overall Steed presents an interesting distribution per-spective of life management of electrical plant. He points out that the effectivemanagement of assets to ensure that the user obtains the optimum life for theplant is becoming more vital as electricity distribution systems are worked harderand all equipment need to be reliable. He considers several strategic aspectsto substantiate his viewpoints. Steed also discusses the impact of smart gridson asset management; he comments that in the early part of twenty-firstcentury much has been talked about smart grids, i.e. the use of new technologiesthat will:

1. facilitate the transition to a low-carbon electricity supply system2. enable an increase in security of supply.

Steed is of the view that as far as (2) is concerned, this relates the challengesof being able to integrate inflexible and/or intermittent generation into the system.He considers the essential elements for this will include:

a wider use of automation and intelligent systems distributed and centralised intelligence, real-time monitoring and diagnostics an integrated cyber-security data protection and data privacy safeguards.

Consequently, Steed considers that condition monitoring systems will becomeincreasingly important and are likely to be applied to more equipment especiallythose identified as system-critical, informing the users of impending failures in thesystem. (Note: Three aspects of condition monitoring are discussed exclusively andsequentially in Chapters 2022.)

Note: At this point, the attention of the reader is again directed towards the fact that frequent reference inthis book will be made to CIGRE technical publications. In anticipation of future developments in thepower sector CIGRE totally reformed its specialist professional Technical Study Committees in 2002 determined by worldwide experts in the power sector as illustrated in Table 1 and considered furtherin section 23.13.2, linked into discussing smart grids of the future and the CIGRE perception of themain challenges ahead (see also Tables 23.923.14).

Chapter 12 by John S. Graham deals comprehensively with High-voltagebushings. This chapter discusses major aspects of bushing design and developmentfor use in equipment in distribution, transmission and including UHV AC and DCtransmission systems. AC and DC bushing types are described and design aspects,clearance requirements and bushing applications in substation equipment areconsidered including transformers, switchgear including direct connection toswitchgear. A wide range of dielectric and other testing strategies are discussedtogether with required maintenance and diagnosis procedures. Finally, typical

Introduction 7

faults occurring in practical bushing designs are described and generous referencesources provided for further reading.

Chapter 13, by A. White,6 provides an authoritative description of the funda-mentals of transformer design and Chapter 14, by S. Ryder and J.A. Lapworth,considers Transformer user requirements, specifications and testing.

Chapters 13 and 14 provide much valuable resource material for the reader.They can both be revisited again and again in a new light as new publicationsfrom CIGRE, etc., become available and be perused by the reader prior torevisiting Chapters 13 and 14 and considering the implications of any such newdata on the overall picture! Conveniently, CIGRE Study Committee A2 hasissued a Study Committee Report, on a transformer efficiency theme, in Electra,2012;263(August), pp. 3640. This has been edited and abridged by this editorand reproduced in Table 2 (at the end of this introduction section) purely toprovide the reader with a further insight into transformer developments. Carefulconsideration of the technical content of this abridged Table 2, if read in con-junction with re-reads of Chapters 13 and 14, will provide the reader with afurther strategic insight and empowerment relating to the transformer topic andthe direction relevant standards are moving (obviously for advanced study thereader should consult the original CIGRE article).

Turning now to HV measurement and testing themes, these are all coveredcomprehensively in Chapters 1518 by Professor Ernst Gockenbach, University ofHannover. Chapters 15 and 16 respectively describe and explain Basic measuringtechniques and basic testing techniques, while Chapter 17 considers this strategicissues surrounding Partial discharge measuring techniques. In his final theme,Chapter 18, Ernst Gockenbach deals with Modern digital measuring techniquesand evaluation procedures.

Finally, linked in to HV testing strategies fully covered in Chapters 1418, it isimportant for the reader to be aware of, and appreciate, certain strategic aspectsrelating to the dielectric breakdown properties and characteristics of atmospheric air.This is very briefly touched on in Chapter 3 but Chapter 19, by J. Blackett, dealsexclusively with the Fundamental aspects of air breakdown. This covers pre-breakdown corona discharges and sparkover, the U-curve, gap factor and sparkovertest procedures, sparkover voltage characteristics under alternating direct voltages,flashover across insulator surfaces in air, atmospheric effects (density, humidityetc.), and developments in the sector. Generous references are provided to assistfurther reading.

Chapters 2022 focus on condition monitoring (CM) approaches:

A. White (Chapter 20), the first on CM, provides an example of the detailedmonitoring of a high-voltage substation component that is a transformer.

6 Additionally, Chapter 20 by Allen White, one of three chapters dealing specifically with aspectsof condition monitoring (i.e. Chapters 2022), considers condition monitoring of high-voltagetransformers.

8 High-voltage engineering and testing

Terry Irwin, C. Charlson and M. Schuler (Chapter 21), the second on CM,explains how monitoring the condition of an entire substation incorporatingseveral components transformers switchgear bus bar housings, etc., is beingaddressed using an integrated substation condition monitoring (ISCM)approach.

G.R. Jones and J.W. Spencer (Chapter 22), the third chapter on CM, providesan insight into future potential developments of intelligent monitoring basedupon examples of optical fibre sensors and chromatic techniques (Centre forIntelligent Monitoring Systems, University of Liverpool approach).

Condition monitoring is now a mature technology, and the reader may find it usefulto refer back to the second edition of this book (ISBN 0-85296-775-6, 2001) toappreciate the progress made in the past decade.

The final Chapter 23, by Hugh Ryan, touches on some recent ESI develop-ments and several other strategic issues, including environmental, state of the art,nuclear prospects (post Fukushima 3/2011) in the UK and overseas; nationalcustomer concerns in UK regarding energy bills and contributions to new energyinvestment costs; renewables [wind energy onshore and offshore aspects,biomass etc.] and certain public perceptions of problems associated with theiroperation, high costs of fuel bills, current levels of customer fuel poverty in theUK; future trends including offshore wind farms, smart-grids and enhancednetworks of the future presenting in detail two strategic viewpoints as toimplications and costs involved; cyber-crime issues; and how CIGRE restructuredits specialist Study Committees to meet the challenges ahead. There will bemany!

Final comments on smart grid initiatives for the future: The reader will seeinteresting overview publications in Chapter 23, e.g. by EPRI, US, and CIGRE.However we are still at the early stages. Before considering these documents, thereader should recall again the wise words of Arslan Erinmez, Chapter 1, when hereminded us that:

at present smart-grid initiatives suffer from inadequately defined objectives aswell as protocols and standards,

there are three other important points concerning transmission and distributionsystems:smart grid initiatives:

(i) smart-grid initiatives at transmission level were more appropriate forspecial protection and control applications

(ii) the application of smart-grid initiatives in distribution systems will besubject to consumer approval and placement of privacy safeguards

(iii) smart-grid initiatives must ensure robustness of transmission and dis-tribution systems to cyber-threats.

Clearly, there will be huge costs involved, much planning required and manytechnical and other issues to be resolved. There is much still to be done, so manyinterested parties to satisfy, with differing agendas, and many difficult hurdles toclear before the smart grid becomes a reality.

Introduction 9

Table 1 Fields of activities of the CIGRE Study Committees, since 2002 reform*[after A history of CIGRE, 2011]

SC A1 Rotating electrical machines [www.cigre-a1.org]Economics, design, construction, test, performance and materials for turbine gen-erators, hydrogenerators, high-power motors and non-conventional machines

SC A2 Transformers [www.cigre-a2.org]Design, construction, manufacture and operation of all types of power transformers,including industrial power transformers, DC converters and phase-shift transfor-mers, and for all types of reactors and transformer components (bushings,tap-changers, etc.)

SC A3 High-voltage equipment [www.cigre-a3.org]Theory, design, construction and operation of devices for switching, interruptingand limitation of currents, lightning arrestors, capacitors, insulators of busbars orswitchgear, and instrument transformers

SC B1 Insulated cables [www.cigre-b1.org]Theory, design, applications, manufacture, installation, tests, operation, main-tenance and diagnostic techniques for land and submarine AC and DC insulatedpower cable systems

SC B2 Overhead lines [www.cigre-b2.org]Design, study of electrical and mechanical characteristics and performance, routeselection, construction, operation, management of service life, refurbishment,uprating and upgrading of overhead lines and their component parts, includingconductors, earth wires, insulators, pylons, foundations and earthing systems

SC B3 Substations [www.cigre-b3.org]Design, construction, maintenance and ongoing management of substations and ofelectrical installations in power stations, excluding generators

SC B4 HVDC and power electronics [www.cigre-b4.org]Economics, application, planning, design, protection, control, construction andtesting of HVDC links and associated equipment. Power electronics for AC systemsand power quality improvement and advanced power electronics

SC B5 Protection and automation [www.cigre-b5.org]Principles, design, application and management of power system protection, sub-station control, automation, monitoring and recording, including associated internaland external communications, substation metering systems and interfacing forremote control and monitoring

SC C1 System development and economics [www.cigre-c1.org]Economics and system analysis methods for the development of power systems:methods and tools for static and dynamic analysis, system change issues and studymethods in various contexts, and asset management strategies

SC C2 System operation and control [www.cigre-c2.org]Technical and human resource aspects of operation: methods and tools for frequency,voltage and equipment control, operational planning and real-time security assess-ment, fault and restoration management, performance evaluation, control centrefunctionalities and operator training

(Continues)

10 High-voltage engineering and testing

Table 1 Fields of activities of the CIGRE Study Committees, since 2002 reform*[after A history of CIGRE, 2011] (Continued)

SC C3 System environmental performance [www.cigre-c3.org]Identification and assessment of the environmental impacts of electric power systemsand methods used for assessing and managing the environment impact of systemequipment

SC C4 System technical performance [www.cigre-c4.org]Methods and tools for power system analysis in the following fields: power qualityperformance, electromagnetic compatibility, lightning characteristics and systeminteraction, insulation co-ordination, analytical assessment of system security

SC C5 Electricity markets and regulation [www.cigre-c5.org]Analysis of different approaches in the organisation of the electrical supply industry:different market structures and products, related techniques and tools, regulationaspects

SC C6 Distribution systems and dispersed generation [www.cigre-c6.org]Assessment of technical impact and new requirements, which new distributionfeatures impose on the structure and operation of the system: widespread develop-ment of dispersed generation, application of energy storage devices, demand sidemanagement, rural electrification

SC D1 Materials and emerging test techniques [www.cigre-d1.org]Monitoring and evaluation of new and existing materials for electro-technology,diagnostic techniques and related knowledge rules and emerging technologies withexpected impact on the system in medium to long term

SC D2 Information systems and telecommunication [www.cigre-d2.org]Principles, economics, design, engineering, performance, operation and main-tenance of telecommunication and information networks and services for the elec-tric power industry; monitoring and related technologies

Note: Since 1921, CIGREs priority role and added value have always been to facilitate mutualexchanges between all its components: network operators, manufacturers, universities and laboratories.It has continually led to the search for a good balance between the handling of daily problemsencountered by its members in doing their jobs and the reflections on the future changes and theirequipment. Its role in exchanging information, synthesising state of the art, and serving members andindustry has constantly been met by CIGRE throughout events and through publications resulting fromthe work of its Study Committees.*

In anticipation of future developments in the power sector, CIGRE totally reformed its specialist pro-fessional Technical Study Committees in 2002 determined by worldwide experts in the power sector as illustrated in Table 1 and considered further in section 23.13.2, linked into discussing smart grids ofthe future and the CIGRE perception of the main challenges ahead (see also Tables 23.923.14).*

[*Source: The history of CIGRE (International Council on Large Electric Systems), 2011, p. 169.]www.cigre.org; www.e-cigre.org

CIGRE technical activities are considered in many chapters of this book and in Table 1 of this intro-duction the reader is now provided with useful background to the wide range of CIGRE technicalactivities: CIGRE key: SC, Study Committee; WG, Working Group and JWG, Joint Working Group;TF, Task Force; TB, Technical Brochure; TR, Technical Report; SC, Scientific Paper.

Introduction 11

Table 2 Transformer efficiency: avenues to make a good thing even better*

The comments made in the present HVET book introduction text will now be simply illu-strated by briefly touching on a CIGRE Study Committee Report on Transformer Effi-ciency prepared by SC A2 and presented in the name of its Chairman Claude Rajotte inElectra, 263, August 2012, pp. 3640, prepared to explain, describe and discuss the differentaspects of transformer efficiency and possible avenues that would allow improvement.

(i) A transformer converts electrical power with exceptional efficiency; yet despite this,Rajotte points out that transformers are with lines and cables among the top contributorsto losses in electrical networks and that this topic, i.e. power efficiency, is a strategictopic for CIGRE [1].

(ii) Rajotte goes on to state that transformer efficiency relates to several factors [2], mainlylosses but also such factors as noise, type and quantity of materials required, weight,size, overall cost, etc. Improving o