High Impulse Voltage andCurrent Measurement Techniques

Klaus Schon

High Impulse Voltage andCurrent MeasurementTechniques

FundamentalsMeasuring InstrumentsMeasuring Methods

123

Klaus SchonFormerly with the Physikalisch-Technische-Bundesanstalt

Braunschweig und BerlinBraunschweigGermany

ISBN 978-3-319-00377-1 ISBN 978-3-319-00378-8 (eBook)DOI 10.1007/978-3-319-00378-8Springer Cham Heidelberg New York Dordrecht London

Library of Congress Control Number: 2013938270

Translation from German by Y. Narayana Rao Formerly with the Indian Institute of Technology,Madras, India

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Preface

Every technical book has, on account of continuing new discoveries, furtherdevelopments in equipment set-up and changes in the area, only a finite actuality.During my professional career, I had the great benefit of engaging myself withlatest technical books of high-voltage engineering, in general, and measurementtechnique, in particular. A part of it has been published a long time ago and is, inthe meantime, out of print or available only as unchanged reprint of older editions.I have therefore taken it upon myself to publish in the present book the result ofmy experience gained over the past decades in the areas of high impulse voltageand current measurement techniques. The intention thereby is to take over actualfundamentals presented in older textbooks, which are valid even today, andcombine them with recent developments in technical equipment, test specifica-tions, calibration of measuring systems and data processing.

Besides the partial discharge measurement technique, high impulse voltage andcurrent measurement technique is generally considered to be an important buildingblock of secured transmission of electrical energy at high voltage potential. Overand above that, it poses high requirements on the engineer and technician entrustedwith measurements in the testing area. In addition to the transmission of electricalenergy, high pulse-type voltages and currents are encountered in other areas ofphysics and engineering, in which they are made use of for various applications.Catchwords for these applications are: plasma physics, power electronics, medicaltechnology, spot-welding technology, electronic ignition systems for combustionengines, electro-shock weapons and electromagnetic compatibility. Even in theseareas, impulse measurement technique acquires a special significance either toprevent an overstressing or understressing of the test object or to guarantee thequality of the application.

At the outset, it has to be borne in mind that in the energy technology area,international testing and measuring methodology has always had a strong influ-ence, not the least on the basis of globalised market economy. This pertains, on theone hand, to national and international test specifications which lay down impulseparameters and fundamental measuring and evaluation procedures, and on theother, to the world-wide network of testing and calibration laboratories; these areaccredited as per internationally accepted rules and their measurement and testresults are mutually recognised and accepted. The present book is not thought of as

v

a copy of the specifications, which have continually changed in course of time, andaccording to our experience, will continue to change even in the future. Never-theless, a few core aspects and the background, especially about the proceduresand changes in the latest editions of the ‘horizontal’ Publications IEC 60060(High-voltage test techniques) and IEC 62475 (High-current test techniques) willbe dealt with. As usual, both IEC Publications were accepted as harmonisededitions by many National Committees.

Over the last two decades, digital impulse voltage and impulse current mea-surement techniques have improved due to the enormously improved properties ofdigital recorders and personal computers. These permit the widest application ofsoftware with numerical calculating methods not only for the evaluation of therecorded waveforms, but also for filtering of the data or even to determine thedynamic behaviour of voltage dividers and current sensors with the help ofconvolution.

For understanding the content of this book, fundamental knowledge of high-voltage engineering is a prerequisite for the reader. While in Europe, measuringsystems as well as testing and measurement techniques are tailor-made for themaximum voltage level of 400 kV, in other parts of the world, more than twicethese levels of transmission voltages are required for bridging large distancesbetween energy sources and consumers. Based on the enormous economicdevelopment of the Asiatic region, voltages higher than 1,000 kV for alternatingvoltage transmission and 800 kV for direct voltage transmission are under dis-cussion. In this connection, whether the proven measuring set-ups and testingtechniques can be used without any hesitation at these higher voltages too must beexamined.

In the area of high impulse voltage and current measurement technique, a largenumber of publications exist in technical journals and conference volumes sinceabout 100 years. As a compromise, mainly, only such references appearing in thelast 30 years have been taken into consideration in this book. The historicallyinterested reader would find earlier references in older books cited in the firstchapter of this book. Multifarious possibilities of research are also available tosuch readers through the internet.

As thanksgiving, I wish to mention in the very first place, Prof. Dr.-Ing. Dr.-Ing.h.c. Dieter Kind, Professor at the Technical University of Braunschweig and Past-President of the Physikalisch Technische Bundesanstalt Braunschweig und Berlin(PTB). He has strongly influenced and fostered my professional career at the High-Voltage Laboratory of PTB, supported me on many small and big occasions andintroduced me to the international group of high-voltage experts. I also thank himfor his friendly interest in the manuscript of the German edition of this book andfor having gone through the first draft.

My hearty thanks are also due to the students who helped me in the course oftheir diploma theses or practical training. Thanks are also due to the many col-leagues in Germany and abroad, who, during discussions in PTB, in workinggroups of CIGRE, IEC, and DKE or in sittings and conferences, have contributedto the expanding and deepening of my knowledge. My thanks are also due to the

vi Preface

PTB Drawing Section and the firms for having readily made available photos forillustrations in the book.

Last but not least, I thank Prof. Y. Narayana Rao, formerly with the IndianInstitute of Technology, Madras, India, for the excellent preparation of thisEnglish volume based on the German textbook ‘‘Stoßspannungs- und Stoßstrom-messtechnik’’ published in 2010.

Braunschweig, March 2013 Klaus Schon

Preface vii

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Characterisation and Generation of High ImpulseVoltages and Currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.1 Parameters of High-Voltage Impulses . . . . . . . . . . . . . . . . . . . 5

2.1.1 Lightning Impulse Voltages . . . . . . . . . . . . . . . . . . . . 62.1.2 Switching Impulse Voltages . . . . . . . . . . . . . . . . . . . . 152.1.3 Impulse Voltages for On-Site Tests . . . . . . . . . . . . . . . 172.1.4 Steep-Front Impulse Voltages . . . . . . . . . . . . . . . . . . . 18

2.2 Parameters of High-Current Impulses. . . . . . . . . . . . . . . . . . . . 182.2.1 Exponential Impulse Currents . . . . . . . . . . . . . . . . . . . 192.2.2 Rectangular Impulse Currents . . . . . . . . . . . . . . . . . . . 212.2.3 Short-Time Alternating Currents . . . . . . . . . . . . . . . . . 22

2.3 Generation of High Impulse Voltages and Currents . . . . . . . . . . 232.3.1 Generators for Lightning and Switching

Impulse Voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.3.2 Generation of Chopped Impulse Voltages . . . . . . . . . . . 282.3.3 Generation of Steep-Front Impulse Voltages . . . . . . . . . 292.3.4 Generators for Exponential Impulse Currents . . . . . . . . 302.3.5 Generation of Rectangular Impulse Currents . . . . . . . . . 342.3.6 Generation of Short-Circuit Alternating Currents . . . . . . 35

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3 Representation of Impulses in Time and Frequency Domain . . . . . 393.1 Analytical Representation of Impulse Voltages . . . . . . . . . . . . . 393.2 Spectrum of Impulse Voltages . . . . . . . . . . . . . . . . . . . . . . . . 453.3 Analytical Representation of Impulse Currents . . . . . . . . . . . . . 483.4 Spectrum of Exponential Impulse Currents . . . . . . . . . . . . . . . . 523.5 Analytical Representation of Short-Circuit Alternating

Currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

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4 Transfer Behaviour of Linear Systems and Convolution . . . . . . . . 554.1 Step Response of a System and Convolution Integral. . . . . . . . . 564.2 Fourier Transform and Transfer Function . . . . . . . . . . . . . . . . . 594.3 Laplace Transform. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624.4 Properties of RC and RLC Circuits . . . . . . . . . . . . . . . . . . . . . 63

4.4.1 Step Response of Low-Pass Filterand Oscillatory Circuit . . . . . . . . . . . . . . . . . . . . . . . . 64

4.4.2 Transfer Function of Low-Pass Filterand Oscillatory Circuit . . . . . . . . . . . . . . . . . . . . . . . . 66

4.5 Response Time, Rise Time and Bandwidth. . . . . . . . . . . . . . . . 674.6 Examples for Convolution . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

4.6.1 Wedge-Shaped Impulse Voltage on RC Circuit . . . . . . . 704.6.2 Wedge-Shaped Impulse Voltage on RLC Circuit . . . . . . 724.6.3 Impulse Voltage on RC Circuit . . . . . . . . . . . . . . . . . . 744.6.4 Response Error and Error Diagram . . . . . . . . . . . . . . . 75

4.7 Experimental Step Response . . . . . . . . . . . . . . . . . . . . . . . . . . 784.7.1 Analysis of the Experimental Step Response. . . . . . . . . 784.7.2 Response Parameters of the Step Response. . . . . . . . . . 804.7.3 Measuring Circuits for the Step Response. . . . . . . . . . . 814.7.4 Generation of Step Voltages . . . . . . . . . . . . . . . . . . . . 83

4.8 Supplementary Observations on Transfer Behaviour . . . . . . . . . 86References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

5 Digital Recorder, Impulse Voltmeter and Impulse Calibrator . . . . 935.1 Construction and Properties of Digital Recorders . . . . . . . . . . . 945.2 Error Sources During Signal Recording . . . . . . . . . . . . . . . . . . 100

5.2.1 Ideal Digitising . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1005.2.2 Digital Recorder with Real AD Converter . . . . . . . . . . 1025.2.3 Further Sources of Error . . . . . . . . . . . . . . . . . . . . . . . 107

5.3 Software for Data Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 1095.4 Impulse Voltmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1115.5 Impulse Calibrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

6 Measurement of High-Voltage Impulses . . . . . . . . . . . . . . . . . . . . 1176.1 Measuring System with High-Voltage Impulse Divider . . . . . . . 118

6.1.1 Transfer Behaviour of High-VoltageImpulse Dividers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

6.1.2 Resistive Impulse Voltage Divider. . . . . . . . . . . . . . . . 1296.1.3 Capacitive Voltage Divider . . . . . . . . . . . . . . . . . . . . . 1386.1.4 Damped Capacitive Impulse Voltage Divider . . . . . . . . 1426.1.5 Resistive-Capacitive Mixed Voltage Divider . . . . . . . . . 151

6.2 Sphere Gap. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

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6.3 Capacitive Field Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1556.3.1 Principle of the Capacitive Field Sensor . . . . . . . . . . . . 1566.3.2 Field Sensor for Linearity Proof of Voltage Dividers . . . 1586.3.3 Three-Dimensional Field Sensor . . . . . . . . . . . . . . . . . 159

6.4 Electro-Optic Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1606.4.1 Pockels Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1606.4.2 Kerr Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

7 Measurement of High-Current Impulses . . . . . . . . . . . . . . . . . . . . 1697.1 Measurement System with Low-Ohmic Measuring Resistor . . . . 170

7.1.1 Inductances of a Low-Ohmic Resistor . . . . . . . . . . . . . 1737.1.2 Construction of Coaxial Measuring Resistors . . . . . . . . 1767.1.3 Skin Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1787.1.4 Ladder Network as Equivalent Circuit . . . . . . . . . . . . . 1817.1.5 Experimental Step Response of Measuring Resistors . . . 1827.1.6 Special Types of Construction. . . . . . . . . . . . . . . . . . . 1837.1.7 Limiting Load Integral . . . . . . . . . . . . . . . . . . . . . . . . 185

7.2 Current Measuring Coils Based on the Induction Principle . . . . . 1877.2.1 Rogowski Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1927.2.2 Current Measuring Coil with Magnetic Core. . . . . . . . . 1977.2.3 Direct Current Transformer. . . . . . . . . . . . . . . . . . . . . 1987.2.4 Magnetic Field Sensor . . . . . . . . . . . . . . . . . . . . . . . . 200

7.3 Current Sensor with Hall Probe. . . . . . . . . . . . . . . . . . . . . . . . 2027.4 Magneto-Optic Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

8 Calibration of the Measuring Systems. . . . . . . . . . . . . . . . . . . . . . 2098.1 General Information on Calibration and Traceability . . . . . . . . . 2108.2 Comparison with a Reference System for Impulse Voltage. . . . . 212

8.2.1 Principle of the Comparative Measurement. . . . . . . . . . 2138.2.2 Assigned Scale Factor . . . . . . . . . . . . . . . . . . . . . . . . 2168.2.3 Alternatives for the Linearity Proof . . . . . . . . . . . . . . . 2188.2.4 Measurement of Time Parameters . . . . . . . . . . . . . . . . 2198.2.5 Dynamic Behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . 219

8.3 Alternative Calibration of Impulse VoltageMeasuring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2218.3.1 Calibration at Low Voltage. . . . . . . . . . . . . . . . . . . . . 2228.3.2 Evaluation of the Step Response . . . . . . . . . . . . . . . . . 2238.3.3 Effect of Neighbouring Objects (Proximity Effect) . . . . 2248.3.4 Short-Term and Long-Term Stability . . . . . . . . . . . . . . 225

8.4 Calibration of Digital Recorders . . . . . . . . . . . . . . . . . . . . . . . 2278.5 Calibration of Impulse Current Measuring Systems . . . . . . . . . . 229References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

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9 Evaluation of Uncertainties of Measurement . . . . . . . . . . . . . . . . . 2339.1 The GUM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

9.1.1 Basic Concept of the GUM. . . . . . . . . . . . . . . . . . . . . 2349.1.2 Model Function of a Measurement . . . . . . . . . . . . . . . 2359.1.3 Type A Evaluation Method. . . . . . . . . . . . . . . . . . . . . 2369.1.4 Type B Evaluation Method . . . . . . . . . . . . . . . . . . . . . 2389.1.5 Combined Standard Uncertainty . . . . . . . . . . . . . . . . . 2409.1.6 Expanded Uncertainty . . . . . . . . . . . . . . . . . . . . . . . . 2429.1.7 Effective Degrees of Freedom. . . . . . . . . . . . . . . . . . . 2439.1.8 Uncertainty Budget . . . . . . . . . . . . . . . . . . . . . . . . . . 2449.1.9 Statement of the Complete Result of a Measurement . . . 2449.1.10 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . 245

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

Appendix A1: Fourier Transform and Laplace Transform . . . . . . . . . 247

Appendix A2: Examples for the Evaluation of Uncertainty . . . . . . . . . 253

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

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Abbreviations

AC Alternating CurrentAD converter Analogue-to-Digital ConverterBIPM Bureau International des Poids et MesuresCIGRE Conseil International des Grands Réseaux ÉlectriquesCMC Calibration and Measurement CapabilityDAKKS German Accreditation BodyDA converter Digital-to-Analogue ConverterDC Direct CurrentDFT Discrete Fourier TransformDIN German Institute for StandardizationDKE German Electrotechnical CommissionEA European co-operation for AccreditationEB Effective Bit numberEMP Electromagnetic PulseEMC Electromagnetic CompatibilityFFT Fast Fourier TransformFS Sphere gapGIS Gas Insulated SwitchgearGPS Global Positioning SystemGTEM Gigahertz Transverse ElectromagneticGUM Guide to the Expression of Uncertainty in MeasurementIEC International Electrotechnical CommissionISH International Symposium on High Voltage EngineeringISO International Organization for StandardizationLI Lightning ImpulseLIC Lightning Impulse ChoppedLSB Least Significant BitNEMP Nuclear Electromagnetic PulseNIST National Institute of Standards and TechnologyNMI National Metrology InstituteNPL National Physical LaboratoryOP Operational AmplifierPC Personal Computer

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PTB Physikalisch-Technische BundesanstaltSI Switching ImpulseTC Technical Committee (of IEC)TDG Test Data GeneratorTEM Transverse ElectromagneticUHV Ultra High VoltageUV Ultraviolet LightUVC Ultraviolet Light of very short WavelengthVIM International Vocabulary of MetrologyWTO World Trade Organization

xiv Abbreviations