Dieter Kind Hermann Karner. High -Voltage Insulation Technology

Size: px

Start display at page:

Download "Dieter Kind Hermann Karner. High -Voltage Insulation Technology"

Shona Cole
5 years ago
Views:

1 Dieter Kind Hermann Karner High -Voltage Insulation Technology

2 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

3 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, ISBN Dt. Ausg. u. d. T.: Kind, Dieter: Hochspannungs-Isoliertechnik für Elektrotechniker 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 DOI / ISBN (ebook)

4 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 approximations 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 technology, 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 Technische 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 industry for the specific perusal of and comment on individual sections.

5 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 translation 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

6 Contents VII Compilation of the most important symbols used X 1 Electric strength Electric field and breakdown voltage Determination of electric fields Maximum field strengths in geometrically similar configurations Formulation for the calculation of the breakdown voltage Breakdown probability Breakdown of gases Charge carriers in gases Self-sustaining discharges Breakdown mechanism in a strongly inhomogeneous field Breakdown under lightning impulse voltages Breakdown under switching impulse voltages Breakdown of solid insulating materials Charge carriers at low field strengths Intrinsic breakdown Thermal breakdown Partial discharge breakdown Breakdown of liquid insulating materials Electric strength of technical configurations with insulating liquids Breakdown mechanisms Breakdown in high vacuum Pollution flashover Development and effect of contamination layers Mechanism of poilu tion flashover Pollution tests Insulating materials in high-voltage technology Requirements for insulating materials Properties and testing of insulating materials Electrical properties Thermal properties Chemical properties Natural inorganic insulation materials Natural gases Quartz and mica

7 VIII Contents 2.4 Synthetic inorganic insulating materials Sulphurhexafluoride (SF 6 ) Glass Ceramic insulating materials Natural organic insulating materials Mineral oil Paper Oil-impregnated paper Synthetic organic insulating materials Molecular configuration and polymerisation reactions Polyethylene (PE) Polyvinylchloride (PVC) Polytetrafluorethylene (PTFE) " Epoxy resin (EP) Polyurethane resin (PUR) Silicone elastomer Chlorinated diphenyls Silicone oil Design and manufacture of high-voltage equipment Structural details in high-voltage technology Basic arrangement of the insulation system Measures to avoid intensification of electric stress Rigid and leak-proof connections to insulating parts Measures for air sealing oil-insulated devices Temperature rise calculation of insulation systems High-voltage capacitors Basic configurations Design of wound capacitors Types of design Bushings and lead-outs Basic configurations Calculation of capacitive gradings Types of design Transformer windings Design factors for magnetic circuits Assembly and connection of windings Insulation of high-voltage windings Impulse voltage performance and winding construction Types of transformer winding Instrument transformers Inductive voltage transformers Capacitive voltage transformers Current transformers

8 Contents IX Appendix: Tables and diagrams : A.l Utilization factors for simple electrode configurations A.1.1 Spherical configurations A.1.2 Cylindrical configurations A.1.3 Point and knife-edge configurations A.1.4 Circular ring configurations A.2 Electric strength of gas-insulated configurations A.2.l Breakdown voltage in the homogeneous field A.2.2 Breakdown field strength of plate, cylinder and sphere electrodes A.2.3 Breakdown voltage of rod gaps in air A.3 Properties of insulating materials A.4 Properties of magnetic materials Bibliography Index

9 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 B C C I D E E Ed Ee F F I Fg H I j magnetic vector potential, constant, area magnetic flux density, constant, width capacitance distributed capacitance, referred capacitance electric displacement, diameter electric field strength, modulus of elasticity (Young's modulus) electric field strength (peak value) breakdown field strength inception ( onset) field strength force, volt-time area, relative humidity, error surface force filler content referred to total mass magnetic field strength current (fixed value, effective (rms) value) current (peak value)

10 Compilation of the most important symbols used XI K constant, factor L self-inductance, length L' distributed inductance, referred inductance p probability, power p' power density Q charge R radius, real part of impedance (resistance) R t thermal resistance S current density, apparent power T absolute temperature, periodic time To reference temperature Tu ambient temperature U voltage (fixed value, effective (rms) value) 0 voltage (peak value) U d breakdown voltage Ue inception (onset) voltage U i ionization voltage W energy W' energy density X reactive part of impedance (reactance) Z apparent impedance (impedance) 0: electron ionization coefficient, thermal transition number, parameter 'Y secondary electron emission coefficient, density tan 0 dissipation factor e dielectric constant ( dielectric permittivity) eo electric constant (permittivity offree space) e r relative dielectric constant (relative permittivity) TI utilization factor Tie attachment coefficient of electrons {} temperature in c " conductivity A mean free path, thermal conductivity 11 permeability 110 magnetic field constant (permeability of free space) I1r relative permeability v natural number, running index p space charge density, specific resistance a variance of the mean, loss increase, surface charge density as layer conductivity 'fi electric potential w angular frequency e cp current linkage (magnetomotive force, ampere-turns) magnetic flux

Code No: RR Set No. 1

Code No: RR Set No. 1 Code No: RR410209 Set No. 1 1. What are the gases mainly used in insulating medium at high pressures? Which is more suitable? Why? What about its dielectric strength? Explain. [16] 2. (a) Define time lags