Table Of ContentDieter Kind
Hermann Karner
High -Voltage
Insulation Technology
Dieter Kind
Hermann Kamer
High-Voltage Insulation Thchnology
Thxtbook for Electrical Engineers
lfanslated from the German by Y Narayana Rao
With 193 Figures
Springer Fachmedien Wiesbaden GmbH
CIP-Kurztitelaufnahme der Deutschen Bibliothek
Kind, Dieter:
High-voltage insulation technology: textbook for
electr. engineers / Dieter Kind; Hermann Kärner.
Transl. from the German by Y. Narayana Rao. -
Braunschweig; Wiesbaden: Vieweg, 1985.
ISBN 978-3-528-08599-5
Dt. Ausg. u. d. T.: Kind, Dieter: Hoch-
spannungs-Isoliertechnik für Elektro
techniker
NE: Kärner, Hermann:
Translation by Dr.-Ing. Y. Narayana Rao, Indian Institute of Technology, Madras
1985
All rights reserved
© Springer Fachmedien Wiesbaden 1985
Ursprünglich erschienen bei Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig 1985
No part of this publication may be reproduced, stored in a retrieval system or transmitted in any
form or by any means, electronic, mechanical, photocopying, recording or otherwise, without
prior permission of the copyright holder.
Produced by W. Langelüddecke, Braunschweig
ISBN 978-3-528-08599-5 ISBN 978-3-663-14090-0 (eBook)
DOI 10.1007/978-3-663-14090-0
v
Preface
The insulation of components and devices in high-voltage technology is of vital importance
and is often the decisive factor in design and construction. Knowledge of the physical
processes which limit the electric strength of an arrangement is essential for economical
manufacture and reliable performance.
The development of high-voltage insulation technology since the beginning of this century
has produced very different solutions for diverse insulations. Characteristic terminology is
frequently used pertaining to specific devices, and this often obscures the clear view of
the basic scientific principles. Manifold solutions, as a consequence of different properties
of the working materials, also impede the understanding of common ground.
This book is principally intended for students of electrical engineering who, towards the
end of their course, aim to pursue the difficult path of applying their fundamentals to
practice. Very often one has to be satisfied with a solution comprising rough approxi
mations and simplifications, yet one must not lose sight of the basic prinCiples because
knowledge of these and their proper application are prerequisites for further development
in virgin technological territories.
In full consciousness of this continuity Prof. Dr.-Ing. E .h. Hans Prinz, our mutual academic
tutor at the Technische Hochschule Mtinchen, trained his students accordingly. We are
honour-bound to gratefully acknowledge this in these pages.
Beginning with a brief review of the procedure for the determination of electric fields, in
the first section on electric strength we consider breakdown phenomena in solids, liquids
and gases, in vacuum and on contaminated insulators. The second section comprises a
condensed treatment of the properties of high-voltage insulation materials as well as their
testing.
Finally, in the third section we discuss constructional peculiarities in high-voltage tech
nology, and subsequently the design and manufacture of capacitors, bushings, lead-outs,
transformer windings and instrument transformers with examples. We conclude with
tables and diagrams frequently used in the design of high-voltage insulations. Preference
has been given to fundamentals rather than detail; a comprehensive bibliography is
appended for further assistance where our treatment may be considered rather terse.
The subject material was collated during the many years work as lecturer at the Tech
nische Universitat Braunschweig, from the consolidation of personal industrial experience
and from research work done at the Braunschweig High-Voltage Institute.
This is an updated version of the German book "Hochspannungs-Isoliertechnik" published
1982, to which many co-workers contributed. We specially thank Dr.-Ing. B. Fell and
Mr. J. Nissen for their assistance in revising the German manuscript before translation.
We also wish to extend our thanks to a number of colleagues at universities and in in
dustry for the specific perusal of and comment on individual sections.
VI Preface
This English volume was prepared in excellent collaboration with our colleague Dr.-Ing.
Y. Narayana Rao, Indian Institute of Technology, Madras, who undertook the trans
lation out of the fund of his own extensive experience in teaching and research. His work
was supplemented by Mrs. C. C. J. Schneider M.A. (Cantab.) who carefully revised the
English manuscript. Thus the same team was engaged as in the case of the earlier volume
"An introduction to High-Voltage Experimental Technique", published 1978 in the same
series. The revised manuscript was painstakingly reyped by Miss G. Bosse. Finally we wish
to thank the publishers Vieweg-Verlag for their efficient cooperation.
Braunschweig, February 1985 Dieter Kind
Hermann Karner
VII
Contents
Compilation of the most important symbols used .. . . . .. . . ... . . .... . . .. X
1 Electric strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 Electric field and breakdown voltage . . . . . . .. . . . . .. . . . . . . . . . . .
1.1.1 Determination of electric fields .... . ... .. . ........... .
1.1.2 Maximum field strengths in geometrically similar
configurations . . .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1.3 Formulation for the calculation of the breakdown voltage . . . . . 8
1.1.4 Breakdown probability. . . . . . . . . . . . . . . . . . . . ... . . 1.0 . . .
1.2 Breakdown of gases. . . . . . . . . . . . . . . . . . . . . . . . . ... . .1 4. . . . . .
1.2.1 Charge carriers in gases. . . . . . . . . . . . . . . . . . . . ... . .1 4. . . .
1.2.2 Self-sustaining discharges . . . . . . . . . . . . . . . . . . ... . . . 18 . . .
1.2.3 Breakdown mechanism in a strongly inhomogeneous field. . . .. . 22
1.2.4 Breakdown under lightning impulse voltages. . . . . . . . . . . . . 25. .
1.2.5 Breakdown under switching impulse voltages . . . . . . . . . . . . 28. .
1.3 Breakdown of solid insulating materials. . . . . . . . . . . . . . . . . . 3.0 . . . .
1.3.1 Charge carriers at low field strengths. . . . . . . . . . . . . . . . 3.0 . . .
1.3.2 Intrinsic breakdown . . . . . . . . . . . . .... . .. .. . . .. .. .... 31
1.3.3 Thermal breakdown. . . . . . . . . . . . . . . . . . . . . .. . . . 3.7 . . . .
1.3.4 Partial discharge breakdown . . . . . . . . . . . . . . . . . . . 4. 1 . . . . .
1.4 Breakdown of liqUid insulating materials . . . . . . . . . . . . . . . . . 4. 7 . . . .
1.4.1 Electric strength of technical configurations with
insulating liquids. . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 7. . . . .
1.4.2 Breakdown mechanisms . . . . . . . . . . . . . . . . . . . ... . .5 0. . . .
1.5 Breakdown in high vacuum . . . . . . . . . . . . . . . . . . . . . ... . .5 2. . . . .
1.6 Pollution flashover ...... . . . . . . . . . . . . . . . . . . . . . . . 5.4 . . . . . .
1.6.1 Development and effect of contamination layers. . . . . . . . ... . 54
1.6.2 Mechanism of poIlu tion flashover. . . . . . . . . . . . . . . . . .5 7. . . .
1.6.3 Pollution tests . . . . . . . . . . . . . . . . . . . . ... .. .. .. .. . .. . 60
2 Insulating materials in high-voltage technology . . . . . . . . . . . . . . . . . 6. 2. . . .
2.1 Requirements for insulating materials . . . . . . . . . . . . . . . . ... . . 62. . .
2.2 Properties and testing of insulating materials . . . . . . . . . . . . . . . .6 3. . .
2.2.1 Electrical properties. . . . . . . . . . . . . . . . . . . . . . . .. . 6.3 . . . .
2.2.2 Thermal properties . . . . . . . . . . . . . . . . . . . . . . . .. .6 .3 . . . .
2.2.3 Chemical properties. . . . . . . . . . . . . . . . . . . . . .. .. . . 7. 0. . .
2.3 Natural inorganic insulation materials . . . . . . . . . . . . . . . . . . . 71. . . . .
2.3.1 Natural gases . . . . . . . . . . . . . . . . . . . . . . . . . . . 71. . . . . . . .
2.3.2 Quartz and mica . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 . . . . . . .
VIII Contents
2.4 Synthetic inorganic insulating materials. . . . . . . . . . . . . . . . . . 7. 2. . . .
2.4.1 Sulphurhexafluoride (SF6) . • . . . . . • . • . • . • . • . • • . • . . 7. 2 • •
2.4.2 Glass. .. ...... . ..... . . .. .... .. .... . .... . ... .. . 74
2.4.3 Ceramic insulating materials . . . . . . . . . . . . . . . . . . .. . 7. 6. . .
2.5 Natural organic insulating materials . . . . . . . . . . . . . . . . . . . . .7 9. . . .
2.5.1 Mineral oil . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . 7. 9 . . . . .
2.5.2 Paper... . ........ . . .. . . . . ....... . ... .. ....... 81
2.5.3 Oil-impregnated paper . . . . . . . . . . . . . . . . . . . . . . .8 2 . . . . . .
2.6 Synthetic organic insulating materials . . . . . . . . . . . . . . . . . . .8 6. . . . .
2.6.1 Molecular configuration and polymerisation reactions . . . . . ... 86
2.6.2 Polyethylene (PE) . . . . . . . . . . . . . . . . . . . . . . . . . 87. . . . . . .
2.6.3 Polyvinylchloride (PVC). . . . . . . . . . . . . . . . . . . . . . 89. . . . . .
2.6.4 Polytetrafluorethylene (PTFE) " . . . . . . . . . . . . . .. .. . 9. 0. .
2.6.5 Epoxy resin (EP). . . . . . . . . . . . . . . . . . . . . . . ... . .9 .1 . . . .
2.6.6 Polyurethane resin (PUR) . . . . . . . . . . . . . . . . . . . . . 93. . . . . .
2.6.7 Silicone elastomer. . . . . . . . . . . . . . . . . . . . . . .. .. .9 4. . . . .
2.6.8 Chlorinated diphenyls . . . . . . . . . . . . . . . . . . . . .. . . 9. 4. . . .
2.6.9 Silicone oil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 6. .
3 Design and manufacture of high-voltage equipment . . . . . . . . . . . . .. .. . 9.7 .
3.1 Structural details in high-voltage technology. . . . . . . . . . . . . . . . 97. . . .
3.1.1 Basic arrangement of the insulation system . . . . . . . . . . . . .9 7 . .
3.1.2 Measures to avoid intensification of electric stress. . . . . . . . . 1.0.1
3.1.3 Rigid and leak-proof connections to insulating parts . . . . . . . .10. 6
3.1.4 Measures for air sealing oil-insulated devices. . . . . . . . . . . . 1.0 8. .
3.1.5 Temperature rise calculation of insulation systems. . . . . . . . . 1.09.
3.2 High-voltage capacitors. . . . . . . . . . . . . . . . . . . . . . . .. .. .1 1.1 . . . . .
3.2.1 Basic configurations. . . . . . . . . . . . . . . . . . . . . .. . . 1. 11. . . . .
3.2.2 Design of wound capacitors ... . . . .... ... . . . . .. . ... . .. 114
3.2.3 Types of design. . . . . . . . . . . . . . . . . . . . . . . . . 1. 1.8 . . . . . . .
3.3 Bushings and lead-outs. . . . . . . . . . . . . . . . . . . . . . . . . .1 2. 0. . . . . . .
3.3.1 Basic configurations. . . . . . . . . . . . . . . . . . . . . ... . 1.2 0. . . . .
3.3.2 Calculation of capacitive gradings. . . . . . . . . . . . . . . ... . 1.2 3. .
3.3.3 Types of design. . . . . . . . . . . . . . . . . . . . . . . . .. . .1 2. 8. . . . .
3.4 Transformer windings . . . . . • . . . . . . . . . . . . . . . . . . .. .. . 130 . . . . .
3.4.1 Design factors for magnetic circuits .. . . . . . . . . . . . . ... . 1.3 0.
3.4.2 Assembly and connection of windings . . . . . . . . . . . . . . . 13.5 . . .
3.4.3 Insulation of high-voltage windings. . . . . . . . . . . . . . . . 1. 3.7 . . .
3.4.4 Impulse voltage performance and winding construction . . . . . .1. 38
3.4.5 Types of transformer winding . . . . . . . . . . . . . . . . . . 1.4 .0 . . . .
3.5 Instrument transformers. . . . . . . . . . . . . . . . . . . . . . . ... .1 4.2 . . . . .
3.5.1 Inductive voltage transformers. . . . . . . . . . . . . . . . .. .. 1. 4.3 . .
3.5.2 Capacitive voltage transformers. . . . . . . . . . . . . . . . ... .1 4. 8 . .
3.5.3 Current transformers. . . . . . . . . . . . . . . . . . . . .. .. .1 5. 2 . . . .
Contents IX
Appendix: Tables and diagrams . . . .. . . .. ......... : . . . . . . . . . . .. . . 1. 59.
A.l Utilization factors for simple electrode configurations . . . . . . . . . . 1. 5.9 .
A.1.1 Spherical configurations. . . . . . . . . . . . . . . . . . . . . ... . .1 59 . .
A.1.2 Cylindrical configurations. . . . . . . . . . . . . . . . . . . ... . 1. 61 . . .
A.1.3 Point and knife-edge configurations . . . . . . . . . . . . . .. . . 1. 6. 3.
A.1.4 Circular ring configurations. . . . . . . . . . . . . . . . . . . . 1.6 5. . . . .
A.2 Electric strength of gas-insulated configurations . . . . . . . . . . . . . .1 68. . .
A.2.l Breakdown voltage in the homogeneous field. . . . . . . . . . . . .. 168
A.2.2 Breakdown field strength of plate, cylinder and
sphere electrodes. . . . . . . . . . . . . . . . . . . . . . . ... . 1.6 9. . . . .
A.2.3 Breakdown voltage of rod gaps in air. . . . . . . . . . . . . . . . 17.1 . . .
A.3 Properties of insulating materials . . . . . . . . . . . . . . . . . . .. . . .1 .7 3 . . .
A.4 Properties of magnetic materials. . . . . . . . . . . . . . . . . . . . . . . .. 177 . . .
Bibliography . . .. . .... .. ...... . ..... . . . ..... ... .... . . .. .. .. . 180
Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... .1 8. 7 . . . . . . . . . .
x
Compilation of the most important symbols used
a spacing, thickness, length
b mobility, width, length
d diameter
e elementary charge
f frequency
current (instantaneous value)
k Boltzmann constant, factor, parameter
1 length
IE mean iron path length
m mass, transformation ratio, natural number
n charge carrier density, natural number
p geometrical characteristic, pressure
q charge
qE effective iron cross-section
r radius, spacing
s gap spacing, thickness, standard deviation
t time
t8 formative time lag
td breakdown time
ts statistical time lag
u voltage (instantaneous value)
Uk relative short-circuit voltage
v volume, velocity, water content
w number of turns
A magnetic vector potential, constant, area
B magnetic flux density, constant, width
C capacitance
C distributed capacitance, referred capacitance
I
D electric displacement, diameter
E electric field strength, modulus of elasticity (Young's modulus)
E electric field strength (peak value)
Ed breakdown field strength
Ee inception ( onset) field strength
F force, volt-time area, relative humidity, error
F surface force
I
Fg filler content referred to total mass
H magnetic field strength
I current (fixed value, effective (rms) value)
j current (peak value)
