High Voltage Engineering

1 HighVoltage EngineeringFundamentalsHigh Voltage EngineeringFundamentalsSecond editionE. KuffelDean Emeritus,University of Manitoba,Winnipeg, ZaenglProfessor Emeritus,Electrical Engineering Dept.,Swiss Federal Institute of Technology,Zurich, SwitzerlandJ. KuffelManager of High Voltage and Current Laboratories,Ontario Hydro Technologies,Toronto, CanadaNewnesOXFORDAUCKLANDBOSTON JOHANNESBURGMELBOURNE NEW DELHIN ewnesAn imprint of Butterworth-HeinemannLinacre House, Jordan Hill, Oxford OX2 8DP225 Wildwood Avenue, Woburn, MA 01801-2041A division of Reed Educational and Professional Publishing LtdFirst published 1984 by Pergamon PressReprinted 1986 Second edition 2000, published by Butterworth-Heinemann E. Kuffel and Zaengl 1984 E. Kuffel, Zaengl and J. Kuffel 2000 All rights reserved.

2 No part of this publicationmay be reproduced in any material form (includingphotocopying or storing in any medium by electronicmeans and whether or not transiently or incidentallyto some other use of this publication) without thewritten permission of the copyright holder exceptin accordance with the provisions of the Copyright,Designs and Patents Act 1988 or under the terms of alicence issued by the Copyright Licensing Agency Ltd,90 Tottenham Court Road, London, England W1P for the copyright holder s written permissionto reproduce any part of this publication should be addressedto the publishersBritish Library Cataloguing in Publication DataA catalogue record for this book is available from the British LibraryLibrary of Congress Cataloguing in Publication DataA catalogue record for this book is available from the Library of CongressISBN 0 7506 3634 3 Typeset by Laser Words, Madras.

3 IndiaPrinted in Great BritainContentsPreface to second editionxiPreface to first editionxvChapter Generation and transmission of electric Voltage Testing Testing with power frequency Testing with lightning impulse Testing with switching Testing with very low frequency voltage7 References7 chapter 2 Generation of high Direct to Electrostatic Alternating Testing Series resonant Impulse Impulse Voltage generator Operation, design and construction of impulse Control systems74 References75 chapter 3 Measurement of high Peak Voltage measurements by spark Sphere Reference measuring Uniform field Rod Electrostatic Ammeter in series with high ohmic resistors and high ohmic resistor Generating voltmeters and field The measurement of peak The Chubb Fortescue Voltage dividers and passive rectifier Active peak-reading High- Voltage capacitors for measuring Voltage dividing systems and impulse Voltage Generalized Voltage generation and measuring Demands upon transfer characteristics of the measuring Fundamentals for the computation of the measuring Voltage Interaction between Voltage divider and its The divider s low- Voltage Fast

4 Digital transient recorders for impulse Principles and historical development of transient digital Errors inherent in digital Specification of ideal A/D recorder and parameters required for Future trends195 References196 chapter 4 Electrostatic fields and field stress Electrical field distribution and breakdown strength of insulating Fields in homogeneous, isotropic The uniform field electrode Coaxial cylindrical and spherical Sphere-to-sphere or Two cylindrical conductors in Field distortions by conducting Fields in multidielectric, isotropic Simple dielectric Stress control by floating Numerical Finite difference method (FDM) Finite element method (FEM) Charge simulation method (CSM) Boundary element method270 References278 chapter 5 Electrical breakdown in Classical gas Velocity distribution of a swarm of The free path of molecules and Distribution of free Collision-energy Ionization and decay Townsend first ionization Ionization by interaction of metastables with Thermal Deionization by Deionization by attachment negative ion Mobility of gaseous ions and deionization by Relation between diffusion and Cathode processes secondary Photoelectric Electron emission by positive ion and excited atom Thermionic Field Townsend second ionization coefficient Secondary electron emission by photon Transition from non-self-sustained discharges to The Townsend The streamer or Kanal

5 Mechanism of The sparking Voltage Paschen s Penning The breakdown field strength (Eb) Breakdown in non-uniform Effect of electron attachment on the breakdown Partial breakdown, corona Positive or anode Negative or cathode Polarity effect influence of space Surge breakdown Voltage time Breakdown under impulse Volt time Experimental studies of time lags362 References365 chapter 6 Breakdown in solid and liquid Breakdown in Intrinsic Streamer Electromechanical Edge breakdown and Thermal Erosion Breakdown in Electronic Suspended solid particle Cavity Electroconvection and electrohydrodynamic model of Static electrification in power transformers393 References394 chapter 7 Non-destructive insulation test Dynamic properties of Dynamic properties in the time Dynamic properties in the frequency Modelling of dielectric Applications to insulation dielectric loss and

6 capacitance The Schering Current comparator Loss measurement on complete Null Partial-discharge The basic PD test PD PD measuring systems within the PD test Measuring systems for apparent Sources and reduction of Other PD Calibration of PD detectors in a complete test Digital PD instruments and measurements453 References456 chapter 8 Overvoltages, testing procedures and insulation The lightning Energy in Nature of Simulated lightning surges for Switching surge test Voltage Laboratory high- Voltage testing procedures and statistical treatment of dielectric stress Voltage Insulation Randomness of the appearance of Types of Types of stress used in high- Voltage Errors and confidence in Laboratory test Standard test Testing with power frequency Distribution of measured breakdown probabilities (confidence inmeasuredP V ) Confidence intervals in breakdown probability (in measured values)

7 Weighting of the measured breakdown Fitting of the best fit normal Insulation Insulation Statistical approach to insulation Correlation between insulation and protection Modern power systems protection MOA metal oxide arresters500 References507 chapter 9 Design and testing of external Operation in a contaminated Flashover mechanism of polluted insulators under and Model for flashover of polluted Measurements and Measurement of insulator Measurement of pollution Contamination Contamination procedure for clean fog Clean fog test Fog Mitigation of contamination Use of insulators with optimized Periodic Grease RTV Resistive glaze Use of non-ceramic Design of Ceramic Polymeric insulators (NCI) Testing and In-service inspection and failure modes531 References531 Index533 Preface to Second EditionThe first edition as well as its forerunner of Kuffel and Abdullah published in1970 and their translations into Japanese and Chinese languages have enjoyedwide international acceptance as basic textbooks in teaching senior under-graduate and postgraduate courses in High- Voltage Engineering .

8 Both textshave also been extensively used by practising engineers engaged in the designand operation of high- Voltage equipment. Over the years the authors havereceived numerous comments from the text s users with helpful suggestionsfor improvements. These have been incorporated in the present edition. Majorrevisions and expansion of several chapters have been made to update thecontinued progress and developments in high- Voltage Engineering over thepast two in the previous edition, the principal objective of the current text is tocover the fundamentals of high- Voltage laboratory techniques, to provide anunderstanding of high- Voltage phenomena, and to present the basics of high- Voltage insulation design together with the analytical and modern numericaltools available to high- Voltage equipment 1 presents an introduction to high- Voltage Engineering includingthe concepts of power transmission, Voltage stress, and testing with varioustypes of Voltage .

9 chapter 2 provides a description of the apparatus used in thegeneration of , , and impulse voltages. These first two introductorychapters have been reincorporated into the current revision with 3 deals with the topic of high- Voltage measurements. It has under-gone major revisions in content to reflect the replacement of analogue instru-mentation with digitally based instruments. Fundamental operating principlesof digital recorders used in high- Voltage measurements are described, and thecharacteristics of digital instrumentation appropriate for use in impulse testingare 4 covers the application of numerical methods in electrical stresscalculations. It incorporates much of the contents of the previous text, but thesection on analogue methods has been replaced by a description of the morecurrent boundary element 5 of the previous edition dealt with the breakdown of gaseous,liquid, and solid insulation.

10 In the new edition these topics are described inxiiPreface to Second Editiontwo chapters. The new chapter 5 covers the electrical breakdown of breakdown of liquid and solid dielectrics is presented in chapter 6 of thecurrent 7 of the new text represents an expansion of chapter 6 of theprevious book. The additional areas covered comprise a short but fundamentalintroduction to dielectric properties of materials, diagnostic test methods, andnon-destructive tests applicable also to on-site monitoring of power expanded scope is a reflection of the growing interest in and developmentof on-site diagnostic testing techniques within the electrical power area represents what is perhaps the most quickly evolving aspect of high- Voltage testing.