High voltage engineering

312 Pages·2007·4.532 MB·English

by  Wadhwa, C. L

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Copyright © 2007, New Age International (P) Ltd., Publishers
Published by New Age International (P) Ltd., Publishers
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ISBN (10) : 81-224-2323-X
ISBN (13) : 978-81-224-2323-5
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Preface to the Second Edition
“High Voltage Engineering” has been written for the undergraduate students in Electri-
cal Engineering of Indian and foreign Universities as well as the practising electrical
engineers.
The author developed interest in the field of High Voltage Engineering when he was a
student at the Govt. Engineering College, Jabalpur. It used to be thrilling to observe large
metal spheres flashing over, corona phenomenon on a wire placed along the axis of a
cylinder and then recording the corona loss, controlling the wave shapes of impulse voltages
etc.
The author has taught the subject at the Delhi College of Engineering for quite a number
of years and while preparing lecture notes he referred to some of the books and journals
and some literature from the internationally famed manufacturers of High Voltage
equipments e.g. Haefely, Tettex etc. The lecture notes so prepared, thus, have a touch of
both the class room requirements and a practising engineer’s requirements.
In this edition, zeroth chapter on Electric Stress estimation and c ontrol has been added
where in different methods viz. finite difference, finite element, charge simmulation method
and surface charge simulation methods have been discussed per estimation of metric
stresses in complex dielectric media and electrode configuration. a brief view of optimisation
of electrode configuration is also given in this chapter.
Chapter 1 deals with the breakdown of gases, liquids, and solid materials. Even though it
has not been possible to explain the physical phenomenon associated with breakdown of
the materials, with accuracy and precisiveness, an attempt has been made to bring out
some of the theories advocated by researchers in this field in a simple lucid and organised
way.
Chapters 2 and 3 discuss the generation of high d.c. and a.c. voltages and high impulse
voltages and currents. Some of the latest circuits have been discussed and rigorous math-
ematical treatment of the circuit has been given to make the subject more interesting and
to make the student understand the subject better.
Measurement of transient voltage and currents and high voltage and current require dif-
ferent skills and equipment as compared with common a.c. or d.c. voltages we normally
come across. Chapter 4 discusses various techniques and circuits for measurement of such
quantities.
( viii )
Chapter 5 deals into high voltage testing of electrical equipments like insulators, cables,
transformers, circuit breakers etc.
The measurements using high voltage Schering bridge, transformer ratio arm bridge and
partial discharges yield information regarding the life expectancy and the long term sta-
bility or otherwise of the insulating materials. These techniques have been discussed elabo-
rately in Chapter 6. These tests are very important both during design and operation of
the equipments.
Electrical transients last for a very short duration but these play a very important role in
the insulation design of power system. Chapter 7 takes a view of various types of tran-
sients in power system and suggests classical and more modern statistical methods of
coordinating the insulation requirements of various equipments of the system and the
devices required for protection of these equipments.
In this edition of the book following articles have been added in chapter 1 of the book :
(i) Breakdown in SF gas and Vacuum.
6
(ii) Insulating materials used in power apparatus.
(iii) Application of gases, liquid and solid insulating materials in different power appara-
tus.
A suitable number of problems have been solved to help understand the relevant theory.
At the end, a large number of multiple choice questions have been added to help the
reader to test himself. An extensive bibliography will help the reader to locate detailed
information on various topics of his interest.
There are very few High Voltage Laboratories all over the world and the reader may not
have an opportunity to visit such a laboratory. Therefore, a few photoplates have been
added at suitable locations in the book to give a physical feel of various equipments in a
well equipped high voltage laboratory. The author feels that with the inclusion of
photoplates of high voltage equipments the student as well the practising engineers would
be greatly benefited.
I wish to express my sincere thanks to M/s Emile Haefely & Co. Ltd., Switzerland for
permitting inclusion of photoplates in the book which has enhanced the utility of the book.
I also wish my express my gratitude to my wife Usha, daughter Meenu and son Sandeep
for their patience and encouragement during the preparation of the book.
Any constructive suggestion for the improvement of the book will be gratefully acknowl-
edged.
New Delhi C.L. WADHWA
Contents
Preface (vii)
0 Electric Stress Estimation and Control (xiii)
0.1 Introduction xiii
0.2 Finite Difference Method xiv
0.3 Finite Element Method xv
0.4 Charge Simulation Method xix
0.5 Surface Charge Simulation Method xxi
0.6 Comparison of Various Techniques xxiii
0.7 Electrolytic Tank xxiii
0.8 Control of Electric Field Intensity xxv
0.9 Optimisation of Electrode Configuration xxvii
0.9.1 Droplacement of Contour Points xxviii
0.9.2 Charging the Position of the Optimisation Charges and Contour Points xxix
0.9.3 Modification of Contour Elements xxx
1 Breakdown Mechanism of Gases, Liquid and Solid Materials 1
1.0 Introduction 1
1.1 Mechanism of Breakdown of Gases 1
1.2 Townsend’s First Ionization Coefficient 2
1.3 Cathode Processes—Secondary Effects 3
1.4 Townsend’ Second Ionization Coefficient 5
1.5 Townsend Breakdown Mechanism 7
1.6 Streamer or Kanal Mechanism of Spark 7
1.7. The Sparking Potential—Paschen’s Law 10
1.8 Penning Effect 14
1.9 Corona Discharges 14
1.10 Time-lag 16
1.10.1 Breakdown in Electronegative Gases 17
1.10.2 Application of Gases in Power System 17
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