Dielectrics in electric fields (1)

Dielectrics
in
Electric Fields
Gorur
G.
Raju
University
of
Windsor-
Windsor, Ontario, Canada
MARCEL
MARCEL
DEKKER,
INC.
DEKKER
NEW
YORK
BASEL
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Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
POWER
ENGINEERING
Series Editor
H.
Lee
Willis
ABB

Inc.
Raleigh, North Carolina
1.
Power Distribution Planning Reference Book,
H. Lee
Willis
2.
Transmission Network Protection: Theory
and
Practice,
Y. G.
Paithan-
kar
3.
Electrical Insulation
in
Power Systems,
N. H.
Malik,
A. A.
AI-Arainy,
and M. I.
Qureshi
4.
Electrical Power Equipment Maintenance
and
Testing, Paul
Gill
5.
Protective Relaying:

Principles
and
Applications, Second Edition,
J.
Lewis
Blackburn
6.
Understanding Electric Utilities
and
De-Regulation,
Lorrin
Philipson
and H. Lee
Willis
7.
Electrical Power Cable Engineering,
William
A.
Thue
8.
Electric Systems, Dynamics,
and
Stability with Artificial Intelligence
Applications, James
A.
Momoh
and
Mohamed
E.
EI-Hawary

9.
Insulation
Coordination
for
Power
Systems,
Andrew
R.
Hileman
10.
Distributed Power Generation: Planning
and
Evaluation,
H. Lee
Willis
and
Walter
G.
Scott
11.
Electric Power System Applications
of
Optimization, James
A.
Momoh
12.
Aging Power Delivery Infrastructures,
H. Lee
Willis,
Gregory

V.
Welch,
and
Randall
R.
Schrieber
13.
Restructured Electrical Power Systems: Operation, Trading,
and
Vola-
tility,
Mohammad Shahidehpour
and
Muwaffaq
Alomoush
14.
Electric Power Distribution Reliability, Richard
E.
Brown
15.
Computer-Aided Power System Analysis, Ramasamy
Natarajan
16.
Power System Analysis: Short-Circuit Load Flow
and
Harmonics,
J.
C.
Das
17.

Power Transformers: Principles
and
Applications, John
J.
Winders,
Jr.
18.
Spatial Electric Load Forecasting: Second Edition, Revised
and Ex-
panded,
H. Lee
Willis
19.
Dielectrics
in
Electric Fields,
GorurG.
Raju
20.
Protection Devices
and
Systems
for
High-Voltage Applications,
Vladimir
Gurevich
ADDITIONAL VOLUMES
IN
PREPARATION
TM

Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
TO
MY
PARENTS.
MY
WIFE,
PADMINI,
AND
OUR
SON,
ANAND
WHO
GA
VE
ME ALL I
VALUE.
SOME DEBTS
ARE
NEVER REPAID
IN
FULL MEASURE.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
SERIES INTRODUCTION
Power engineering
is the
oldest
and

most traditional
of the
various areas within
electrical engineering,
yet no
other
facet
of
modern technology
is
currently undergoing
a
more dramatic revolution
in
both technology
and
industry structure. This addition
to
Marcel Dekker's Power
Engineering
Series addresses
a
fundamental element
of
electrical engineering. Dielectric materials
are a key
element
of
electric power
engineering,

one of the
most challenging aspects
of
improving reliability
and
economy
of
materials.
For an
industry pressed hard
to
increasingly cram more equipment
capacity into ever-tighter spaces,
to
improve reliability, particularly mean time between
failures,
modern dielectric materials
and
engineering methods provide
a
valuable tool
to
meet these challenges.
Dielectrics
in
Electric Fields
is a
well-organized
and
comprehensive view

of
both
the
theory behind
and
application
of
dielectric materials
in
power equipment, industrial
equipment,
and
commercial appliances.
At
both
the
introductory
and
advanced levels,
it
provides both
a
solid foundation
of
theory,
fact,
nomenclature,
and
formula,
and

sound
insight into
the
philosophies
of
dielectric engineering techniques
and
their
use.
Its
unifying
approach, based
on
both physics
and
engineering, makes
it
useful
as a
day-to-
day
reference
as
well
as an
excellent tutorial:
the
book begins with
a
thorough review

of
the
basics
of
dielectric
and
polymer science
and
builds upon
it a
comprehensive
and
very
broad presentation
of all
aspects
of
modern dielectric theory
and
engineering, including
the
lastest
analysis
and
modeling
techniques.
As
the
editor
of the

Power Engineering Series,
I am
proud
to
include Dielectrics
in
Electric
Fields
among this important group
of
books. Like
all the
volumes planned
for
the
series,
Professor
Raju's
book puts modern technology
in a
context
of
proven,
practical
application;
useful
as a
reference
book
as

well
as for
self-study
and
advanced
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
classroom use.
The
series includes books covering
the
entire
field
of
power engineering,
in all its
specialties
and
sub-genres,
all
aimed
at
providing practicing power engineers
with
the
knowledge
and
techniques they need

to
meet
the
electric industry's challenges
in the
21
st
century.
H.
Lee
Willis
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
PREFACE
Materials
that
do not
normally
conduct
electricity
and
have
the
ability
to
store
electrical charge
are
known
as

dielectrics.
The
behavior
of
dielectrics
in
electric
fields
continues
to be an
area
of
study that
has
fascinated physicists, chemists, material
scientists, electrical engineers, and, more recently biologists. Ideas that explain aspects
of
dielectric behavior
in
high voltage electrical cables
are
also applicable
to the
insulating
barrier
in
metal oxide semiconductors
or
interlayer insulation
of

integrated circuits.
Microwave drying
of
milk, dielectric properties
of
agricultural products such
as
flour
and
vegetable oils
to
determine their moisture content,
and the
study
of
curing
of
cement etc.,
are
some
nontraditional
applications
of
dielectric studies that show potential promise.
Deeper insight into
the
interaction between electric
fields and
molecules
has

resulted
in
many
new
applications. Power engineers
are
interested
in the
study
of
insulating
materials
to
prolong
the
life
of
insulation
and
determine
the
degree
of
deterioration
in
service
to
plan
for
future

replacements
or
service maintenance.
Polymer scientists
are
interested
in
understanding
the
role
of
long chain molecules
in
varied applications ranging
from
heat resistant dielectrics
to
selfrepairing
plastics.
The
intensity
of
research
in
this
area,
after
a
brief
respite,

has
resumed
at a
furious
pace,
the
published literature expanding
at a
rate
faster
than ever. Advances
in
instrumentation
and
theoretical
models have also contributed
to
this renewed interest.
Organic polymers
are
considered
to be
stable materials
at
high temperatures
and
have
the
ability
to

withstand radiation, chemical attacks,
and
high electrical
and
mechanical stresses, making them suitable
for
extreme operating environments
as in a
nuclear power plant
or in
outer space. Polymer materials have
the
ability
to
store
electrical
charges. Like
a
diamond-studded sword, this property
is
wholly undesirable
in
applications
such
as
electrical equipment
and the
petrochemical industry;
yet it is a
sought-after

property
in
applications such
as
photocopying
and
telephones.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
This book explains
the
behavior
of
dielectrics
in
electric
fields
in a
fundamentally
unifying
approach
that
is
based
on
well-established principles
of
physics

and
engineering. Though excellent monographs exist
on
specialized topics dealing with
a
relatively narrow area
of
interest, there
is a
need
for a
broader approach
to
understand
dielectrics.
It has
evolved
out of
graduate lectures
for
nearly thirty-five years
at the
Indian Institute
of
Science, Bangalore (1966-1980)
and the
University
of
Windsor,
Windsor, Ontario, Canada

(1980-2002).
The
probing questions
of
students
has
helped
the
author
to
understand
the
topics better
and to a
certain extent dictated
the
choice
of
topics.
The
book begins with
an
introductory chapter that explains
the
ideas that
are
developed subsequently.
The
calculation
of

forces
in
electric
fields
in
combinations
of
dielectric media
is
included because
it
yields analytical results that
are
used
in the
study
of the
dielectric constant (Ch.
2). The
band
theory
of
solids
is
included because
it is
required
to
understand
the

energy levels
of a
dielectric,
as in the
conduction
and
formation
of
space charge (Ch.
6-11).
The
energy distribution
function
is
dealt with
because
it is a
fundamental
property that determines
the
swarm parameters
in
gaseous
breakdown
and
partial discharges (Ch. 8-9).
Chapter
2
deals with
the

mechanisms
of
electrical polarization
and
their role
in
determining
the
value
of the
dielectric constant under direct voltages. Expressions
for
the
dielectric constant
are
given
in
terms
of the
permanent dipole moment
of the
molecule
and
temperature. Several theories
of
dielectric constant
are
explained
in
detail

and
practical applications
are
demonstrated. Methods
of
calculating
the
dielectric
constant
of two
different
media
and
mixtures
of
liquids
are
also demonstrated.
Chapter
3
begins with
the
definitions
of the
complex dielectric constant
in an
alternating electric
field.
The
Debye equations

for the
complex dielectric constant
are
explained
and the
influence
of
frequency
and
temperature
in
determining
the
relaxation
is
examined. Functions
for
representing
the
complex dielectric constant
in the
complex
plane
are
given
and
their interpretation
in
terms
of

relaxation
is
provided. Several
examples
are
taken
from
the
published literature
to
bring
out the
salient points.
Chapter
4
continues
the
discussion
of
dielectric relaxation
from
chapter
3. The
concept
of
equivalent circuits
is
introduced
and
utilized

to
derive
the set of
equations
for
both Debye relaxation
and
interfacial
polarization.
The
absorption
and
dispersion
phenomena
for
electronic polarization
are
considered, both
for
damped
and
undamped
situations. These ideas have become very relevant
due to
developments
in
fiber
optics
technology.
Chapter

5
deals with
the
application
of
these ideas
to
understand
the
experimental
results
in the
frequency
domain
and
with temperature
as the
main parameter
in
selected
polymers.
A
brief introduction
to
polymer science
is
included
to
help
the

reader
understand what
follows.
The
terminology used
to
designate relaxation peaks
is
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
explained
and
methods
for
interpreting observed results
in
terms
of
physics
and
morphology
are
presented.
Chapter
6
deals with
the
measurement

of
absorption
and
desorption
currents
in the
time domain
in
polymers. Though external parameters influence these measurements
our
concern
is to
understand
the
mechanisms
of
charge
generation
and
drift.
Time
domain
currents
may be
transformed into
the
frequency
domain complex dielectric constant
and
the

necessary theories
are
explained.
The low
frequency,
high temperature relaxations
observed
in
several polymers
are
explained
as
complementary
to the
topics
in
Chapter
5.
The
magnitude
of
electric
fields
that
are
employed
to
study
the
behavior

in
dielectrics outlined
in
Chapters
1-6 is low to
moderate. However,
the
response
of a
polymer
to
high electric
fields
is
important
from
the
practical point
of
view.
The
deleterious
effects
of
high electric
fields
and/or high temperatures occur
in the
form
of

conduction currents
and the
complex mechanism
of
conduction
is
explained
in
terms
of
the
band picture
of the
dielectric. Several examples
are
selected
from
the
published
literature
to
demonstrate
the
methods
of
deciphering
the
often
overlapping mechanisms.
Factors that influence

the
conduction currents
in
experiments
are
outlined
in
Chapter
7.
Chapters
8
deals with
the
fundamental
processes
in
gaseous electronics mainly
in
uniform
electric
fields and
again,
due to
limitation
of
space, physical principles
are
selected
for
discussion

in
preference
to
experimental techniques
for
measuring
the
cross
sections
and
swarm
properties.
A set of
formulas
for
representing
the
relevant
properties
of
several gases, such
as the
swarm
coefficients
are
provided,
from
recent published
literature.
Chapter

9 is
devoted
to
studies
on
nonuniform
electric
field in
general
and
corona
phenomenon
in
particular. These aspects
of
gaseous breakdown
are
relevant
from
practical points
of
view,
for
providing better design
or to
understand
the
partial discharge
phenomena. Both experimental
and

theoretical aspects
are
considered utilizing
the
literature published since 1980,
as far as
possible. Several computational methods, such
as
the
Boltzmann equation, solutions
of
continuity equations,
and
Monte Carlo methods
are
included.
The
results obtained
from
these studies
are
presented
and
discussed.
Chapter
10
deals with thermally stimulated processes, mainly
in
polymers.
The

theory
of
thermally stimulated discharge currents
and
techniques employed
to
identify
the
source
of
charge generation
are
described
to
assist
in
carrying
out
these experiments
Chapter
11
deals with measurement
of the
space charges
in
solids
and the
different
experimental techniques
are

explained
in
detail. These nondestructive techniques have
largely
replaced
the
earlier
techniques
of
charging
a
dielectric
and
slicing
it for
charge
measurements.
The
Theory necessary
to
analyze
the
results
of
space charge experiments
and
results obtained
is
included with each method presented.
The

author
is not
aware
of
any
book that systematically describes
the
experimental techniques
and the
associated
theories
in a
comprehensive manner.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
The
book uses
the SI
units entirely
and
published literature since
1980
is
cited,
wherever possible, except while discussing
the
theoretical aspects.
The

topics chosen
for
inclusion
has my
personal bias, though
it
includes chapters that interest students
and
established
researchers
in a
wide range
of
disciplines,
as
noted earlier. Partial discharges,
breakdown
mechanisms,
liquid
dielectrics,
Outdoor
insulation
and
nanodielectrics
are
not
covered mainly
due to
limitation
of

space.
I am
grateful
to a
number
of
graduate students
who
contributed substantially
for a
clearer understanding
of the
topics covered
in
this volume,
by
their probing questions.
Drs.
Raja
Rao,
G. R.
Gurumurthy,
S. R.
Rajapandiyan,
A. D.
Mokashi,
M. S.
Dincer,
Jane Liu,
M. A.

Sussi have contributed
in
different
ways.
I am
also
grateful
to Dr.
Bhoraskar
for
reading
the
entire manuscript
and
making
helpful
suggestions.
It is a
pleasure
to
acknowledge
my
association with Drs.
R.
Gorur,
S.
Jayaram,
Ed
Churney,
S.

Boggs,
V.
Agarwal,
V.
Lakdawala,
T.
Sudarshan
and S.
Bamji
over
a
number
of
years.
Dr.
R.
Hackam
has
been
an
associate since
my
graduate student years
and it is
appropriate
to
recall
the
many discussions
I

have held
on
various aspects
of
dielectric
phenomena considered
in
this book.
The
personal encouragement
of
Professor Neil Gold,
University
of
Windsor
has
contributed
in no
small measure
to
complete
the
present book.
Special thanks
are due to Dr. N.
Srinivas
who
provided opportunity
to
complete

chapters
8 and 9
during sabbatical leave. Prof.
C. N. R.
Rao, President
of the
Jawaharlal
Nehru
Center
for
Advanced
Scientific
Research
provided
opportunity
to
spend
sabbatical
leave
during which time
I
could work
on the
manuscript.
Mr. N.
Nagaraja
Rao
extended
generous hospitality
on

campus making
it
possible
to use the
library facilities
in
Bangalore.
This book would
not
have been completed without
the
help
of Mr. S.
Chowdhury
who
showed
me how to
make
software
applications cooperate with each other.
Extraordinary help
was
provided
by
Alan Johns
in
keeping
the
computer system
in

working condition throughout.
Ms. S.
Marchand assisted
in
checking
the
manuscript
and
Ms.
Ramneek
Garewal assisted
in the
compilation
of
figures
and
tables. While
acknowledging
the
help received,
I
affirm
that errors
and
omissions
are
entirely
my own
responsibility.
I

have made sincere attempts
to
secure copyright permission
for
reproducing every
figure
and
table
from
the
published literature,
and
acknowledge
the
prompt response
from
institutions
and
individuals.
If
there
are
unintentional failures
to
secure permission
from
any
source,
I
render apology

for the
oversight.
Personal
thanks
are due to
Brian
Black
and B. J.
Clark
who
have
patiently
suffered
my
seemingly disconnected communications and, provided great assistance
in
improving
the
style
and
format.
Finally
the
inexhaustible patience
of my
wife
Padmini
has
been
a

source
of
continuous strength
all
these years.
Gorur
G.
Raju
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
CONTENTS
Series
Introduction
Preface
Chapter
1
Introductory Concepts
1.1
A
dipole
1.2
The
potential
due to a
dipole
1.3
Dipole moment
of a

spherical charge
1.4
Laplace's
equation
1.4.1
A
dielectric sphere immersed
in a
different
medium
1.4.2
A
rigid dipole
in a
cavity within
a
dielectric
1.4.3
Field
in a
dielectric
due to a
conducting inclusion
1.5
The
tunneling phenomenon
1.6
Band theory
of
solids

1.6.1
Energy bands
in
solids
1.6.2
The
Fermi level
1.6.3
Electron emission
from a
metal
1.6.4 Field intensification
factor
1.7
Energy distribution
function
1.8
The
Boltzmann
factor
1.9
A
comparison
of
distribution
functions
1.10
References
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.

TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
Chapter
2
Polarization
and
Static Dielectric Constant
2.1
Polarization
and
dielectric constant
2.2
Electronic polarization
2.3 The
internal
field
2.4
Orientational polarization
2.5
Debye equations
2.6
Experimental verification
of
Debye equation
2.7
Spontaneous polarization
2.8
Onsager's theory
2.9
Theory

of
Kirkwood
2.10 Dielectric constant
of two
media
2.10.1
Raleigh's
formula
2.10.2
Wiener's formula
2.10.3
Formula
of
Lichtenecker
and
Rother
2.10.4
Goldschmidt's
Equation
2.11
The
dissipation
factor
2.12 Dielectric constant
of
liquid mixtures
2.12.1
Raleigh's formula
2.12.2
Formula

of
Meredith
and
Tobias
2.12.3
Bruggeman'
s
formula
2.12.4
Looyenga's formula
2.12.5
Bottcher's
formula
2.13
Effect
of
high electric
fields
2.14
Atomic polarizability
2.15 References
Chapter
3
Dielectric Loss
and
Relaxation-!
3.1
Complex permittivity
3.2
Polarization

build
up
3.3
Debye equations
3.4
Bi-stablemodelofadipole
3.5
Complex plane diagram
3.6
Cole-Cole relaxation
3.7
Dielectric properties
of
water
3.8
Davidson-Cole
equation
3.9
Macroscopic relaxation time
3.10
Molecular relaxation time
3.11
Straight line relationships
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Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
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3.12
Frohlich's
analysis

3.13
Fuoss-Kirkwood
equation
3.14
Havriliak
and
Negami dispersion
3.15
Dielectric susceptibility
3.16
Distribution
of
relaxation
times
3.17
Kramer-Kronig
relations
3.18
Loss
factor
and
conductivity
3.19 References
Chapter
4
Dielectric Loss
and
Relaxation-ll
4.1
Jonscher'

s
universal
law
4.2
Cluster approach
of
Dissado-Hill
4.3
Equivalent circuits
4.3.1
A
series
equivalent circuit
4.3.2
Parallel equivalent circuit
4.3.3 Series-parallel circuit
4.3.4
Summary
of
simple equivalent
circuits
4.4
Interfacial polarization
4.5
The
Absorption phenomenon
4.6
Frequency dependence
of s*
4.7

References
Chapter
5
Experimental
Data (Frequency Domain)
5.1
Introduction
to
polymer science
5.1.1
Classification
of
polymers
5.1.2
Molecular weight
and
size
5.1.3
Glass transition temperature
5.1.4
Crystallinity
of
polymers
5.1.5
Thermally stable groups
5.1.6
Polymer degradation
and
defects
5.1.7

Dipole moment
of
polymers
5.1.8
Molecular structure
5.2
Nomenclature
of
Relaxation Processes
5.3
Non-Polar Polymers
5.3.1
Polyethylene
5.3.2
Poly(tetrafluoroethylene)
5.4
Polar Polymers
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Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
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Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
5.4.1 Polypropylene
5.4.2 Poly(vinyl chloride)
5.4.3
Polychlorotrifluoroethylene
5.4.4 Polycarbonate
5.4.5 Poly(methyl
methacrylate)
5.4.6
Poly(vinyl

acetate)
5.4.7 Polystyrene
5.4.8
Polyethylene
terephthalate)
5.4.9 Polyisoprene
5.4.10
Epoxy
Resins
5.4.11
Polyamides
5.4.12 Polyimides
5.5
Scaling methods
5.6
Concluding Remarks
5.7
References
Chapter
6
Absorption
and
Desorption Currents
6.1
Absorption current
in a
dielectric
6.2
Ramon's
approximation

6.3
Distribution
of
relaxation time
and
dielectric
function
6.3.1
Cole-Cole
function
6.3.2
Davidson-Cole
function
6.3.3
Fuoss-Kirkwood
function
6.3.4
Havriliak-Negami
function
6.4
The
Williams-Watts
function
6.5
The
G(i)
function
for
William-Watt
curent decay

6.6
Experimental measurements
6.6.1
Poly(vinyl
acetate)
6.7
Commercial dielectrics
6.7.1
Aramid paper
6.7.2
Composite polyamide
6.7.3
Polyethylene
terephthalate)
6.7.4
Fluoropolymer
6.7.5
Polyimide
6.8
References
Chapter
7
Field
Enhanced Conduction
7.1
Some general comments
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Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
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Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.

7.2
Motion
of
charge carriers
in
dielectrics
7.3
Ionic conduction
7.4
Charge injection into dielectrics
7.4.1
The
tunneling
phenomenon
7.4.2
Schottky
emission
7.4.3 Hopping mechanism
7.4.4
Poole-Frenkel
Mechanism
7.4.5 Space charge limited current (trap
free)
7.4.6 Space charge limited current (with traps)
7.5
Space charge phenomenon
in
non-uniform
fields
7.6

Conduction
in
selected polymers
7.6.1
Conduction
in
polyethylene
7.6.2 Conduction
in
fluoropolymers
7.6.3 Aromatic
polyimide
7.6.4 Aromatic polyamide
7.7
Numerical computation
7.8
Closing remarks
7.9
References
Chapter
8
Fundamental Aspects
of
Gaseous
Breakdown-l
8.1
Collision phenomena
8.1.1
Elastic collision
8.1.2

Collision
cross
section
8.1.3 Probability
of
collision
8.1.4
Inelastic collisions
8.1.5
Mean
free
path
8.1.6
lonization
by
collision
8.1.7
Direct
ionization
8.1.8
Dissociative ionization
8.1.9
Excitation
8.1.10
Dissociative excitation
8.1.11
Photoexcitation
8.1.12
Electron attachment
8.1.13

Electron detachment
8.1.14
Recombination
8.1.15
Secondary ionization
coefficient
8.1.16
Photo-ionization
8.1.17
Electron swarm coefficients
8.2
Electron Growth
in an
Avalanche
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Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
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8.3
Criteria
for
Breakdown
8.4
Paschen's
Law
8.5
Breakdown time lags
8.5.1
The
statistical time

lag
8.5.2 Formative time lags
in
uniform
fields
8.5.3 Formative time lags
in
cylindrical geometry
8.6
The
streamer mechanism
8.6.1
The
leader mechanism
8.7
Field distortion
due to
space charge
8.8
Sparkover
characteristics
of
uniform
field
gaps
in
SF
6
8.9
Sparkover characteristics

of
long gaps
8.10
Breakdown voltages
in air
with alternating voltages
8.11
Concluding remarks
8.12 References
Chapter
9
Fundamental Aspects
of
Electrical
Breakdown-ll
9.1
Electron energy
distribution
functions (EEDF)
9.1.1
EEDF:
The
Boltzmann equation
9.1.2
EEDF:
The
Monte Carlo method
9.2
Streamer formation
in

uniform
fields
9.3
The
corona discharge
9.4
Basic mechanisms: Negative corona
9.5
Basic Mechanisms: Positive corona
9.6
Modeling
of
corona discharge: Continuity equations
9.7
Non-equilibrium
considerations
9.8
Monte Carlo simulation: Negative corona
in
SF
6
9.9
Monte Carlo Simulation: Positive corona
in
SF
6
9.10 Concluding Remarks
9.11
References
Chapter

10
Thermally Stimulated Processes
10.1
Traps
in
insulators
10.2 Current
due to
thermally stimulated depolarization (TSDC)
10.3
TSD
currents
for
distribution
of
activation energy
10.4
TSD
currents
for
universal
relaxation mechanism
10.5
TSD
currents with ionic space charge
10.6
TSD
currents with electronic conduction
10.7
TSD

currents with corona charging
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Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
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10.8
Compensation temperature
10.9 Methods
and
analyses
10.10
TSD and AC
dielectric properties
10.11
References
Chapter
11
Space Charge
in
Solids
Dielectrics
11.1
The
meaning
of
space charge
11.2
Polarons
and
traps

11.3
A
conceptual approach
11.4
The
thermal pulse method
of
Collins
11.5
DeReggi's analysis
11.6
Laser intensity modulation method
(LIPP)
11.7
The
pressure pulse method
11.7.1
Laser induced pressure pulse method
11.7.2
Thermoelastic
stress
waves
11.7.3
Pressure wave propagation (PWP) method
11.7.4
Nonstructured
acoustic probe method
11.7.5
Laser generated acoustic pulse method
11.7.6

Acoustic pulse generated
by
mechanical excitation
11.7.7
Piezo-Electric
Pressure Step Method (PPS)
11.7.8
Pulsed Electro-Acoustic Stress Method
11.7.9
Electron Beam Method
11.7.10
Special Techniques
11.8
Experimental Results
11.9 Closing Remarks
11.10
References
Appendix
1:
Trade
Names
of
Polymers
Appendix
2:
General Classification
of
Polymer Dielectrics
Appendix
3:

Selected Properties
of
Insulating Materials
Appendix
4:
Relative Ranking
of
Thermoplastic
Polymers
Appendix
5:
Selected
Propertiers
of
Polymer Insulating Materials
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.
TM
Copyright n 2003 by Marcel Dekker, Inc. All Rights Reserved.