MODELLING AND ANALYSIS OF METALLIC PARTICLE
CONTAMINATION IN GAS INSULATED SUBSTATION UNDER
PURE SF6 AND SF6+N2 GAS MIXTURES
“A synopsis”
submitted in partial fulfillment of the requirements for the award of the
degree of Doctor of Philosophy in
“FACULTY OF ELECTRICAL ENGINEERING”
By
D.PADMAVATHI
[REG.NO.30706EE/PH]
RESEARCH AND DEVELOPMENT CELL
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY
KUKATPALLY, HYDERABAD – 500 085, A.P. INDIA.
September 2010
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Synopsis on
MODELLING AND ANALYSIS OF METALLIC PARTICLE
CONTAMINATION IN GAS INSULATED SUBSTATION UNDER
PURE SF6 AND SF6+N2 GAS MIXTURES
Introduction:
Demand for electrical power has become one of the major challenges faced by
the developing countries. Considering the relative low per capita power
consumption, there is a constant need for power capacity addition and
technological upgradation whereas non-conventional energy systems have
proved to be good alternative sources for energy. In developing countries like
India most of the additional power has been met by conventional electric
sources. Hence, the emphasis has shifted towards improving the reliability of
transmission and distribution systems and ensuring that the innovations are
not harmful to the environment. Due to rapid urbanization and overgrowing
population is making the task of expanding transmission network very difficult
due to right of way problem and limited space availability. Power needed a
creative solution to its urbanization problem, a compact design on a smaller
site with improved aesthetics to lessen the impact on the neighborhood. Gas
Insulated Substation has found a broad range of applications in power systems
for more than two decades because of their high reliability, easy maintenance
and small ground space requirement etc. In our country, a few GIS units have
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been in operation and a several large number of units are under various stages
of installation. Gas Insulated Substations are essential in the transmission of
electrical power to growing urban centers where conventional air insulated
substations can no longer meet the requirements of available space, pollution,
safety, maintenance and other similar expectations. The Gas Insulated
Switchgear (GIS) contains major substation equipment, such as gas circuit
breaker, disconnecting switch, earthing switch, voltage transformer, current
transformer, and lightning arrester in the grounded metallic enclosure and is
filled with SF6 gas, which has the best insulation and arc- quenching
capabilities.
The introduction of SF6 gas has revolutionized not only the technology of
circuit breakers but also the layout of substations. Gases are used as an
insulating medium for compact substation components and gas insulated
cables. In recent years, sulphur hexafluoride (SF6) gas has been of considerable
technological interest as an insulation medium in high voltage apparatus
because of its superior insulating properties, high dielectric strength at
relatively low pressure and its thermal and chemical stability. SF6 exhibits
many properties that make it suitable for equipment utilized in the
transmission and distribution of electric power SF6 has been found to be a
greenhouse gas. It absorbs infrared radiation and is also immune to chemical
and photolytic degradation. Therefore, its contribution to global warming is
cumulative and virtually permanent. Over a 100 years, its global warming
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potential (GWP) is estimated to be 24000 times greater than that of CO 2. For
this reason it is included in the six gas basket of the Kyoto Protocol.
Calculations based on atmospheric measurements show that the total
worldwide emissions of SF6 contribute only about 0.1 percent of the overall
anthropogenic greenhouse effect. This includes both the SF6 emissions from
the major area of use in electricity transmission and distribution systems
(about 70-80 % of the global SF6 production is used in this sector) and those
from all other uses.
The searches for even better gas insulation continues in order to develop
gases and gas mixtures to satisfy specific requirements for various devices,
provided such gases have dielectric properties comparable or superior to each
other. There are two basic reasons for carrying out such investigations. Firstly,
the aims are to develop an insulating medium, which is technically as well as
economically attractive. The other reason is to obtain a better understanding of
the breakdown mechanisms operating in compressed gases, and their gas
mixtures. Most of the published data refer to uniform or nearly uniform field
gaps for SF6, CO2, (carbon dioxide) N2 (nitrogen) and air [1-2].
In a typical industrial application the non-uniform field breakdown
predominates. Earlier experimental results showed strong dependence of
breakdown voltages upon applied voltage, voltage polarity, electrode spacing,
pressure and the nature of the gas. It is recognized that Sulfur Hexafluoride
(SF6) gas has excellent dielectric and heat transfer properties and is
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increasingly being used in high-pressure gas insulated systems. However, in
practice the electrical breakdown strength of compressed SF6 is often governed
by a local field enhancement due to the protrusions, surface roughness, and
the presence of conducting particles in the system. In addition the fact that SF6
is a strong greenhouse gas has prompted interest in substitute gases with
lower or no environmental impact. Therefore, there is an increasing interest in
the possible application of mixtures of SF6 and other gases to reduce insulation
cost and to minimize the possible hazard of particle-initiated breakdown. Many
researches have studied behavior of air, N2 and CO2 mixed with a small
percentage of SF6 as an additive. The mixture of SF6+N2 gases is used for
numerous applications, including use as insulation for high voltage equipment.
From a practical point of view, only SF 6 mixtures with those common gases or
buffer gases (air, N2) show an importance in most industrial applications [4].
L.G.Christophorou .et.al.,[3] stated that addition of small amount of SF6
to N2 gas can considerably improve the breakdown strength depending on the
gas pressure and reduces insulation cost of the system at higher gas
pressures. This type of behavior is more pronounced when the field
configuration is highly non-uniform and/or gas pressure is high.
SF6 is the main mode of insulation in a GIS. However, in recent years, the
future use of SF6 has been debated throughout the world in spite of it having
all the desirable properties of a good insulating and arc quenching medium.
Sulfur hexafluoride (SF6) has been used as a gaseous dielectric (insulator) in
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high voltage equipment since the1950s. It is now known that SF6 is a potent
greenhouse warming gas with one of the highest global warming potentials
(GWP) known. Because of its high GWP, it is being phased out of all frivolous
applications.SF6 is an efficient absorber of infrared radiation, particularly at
wavelengths near 10.5 µm. Additionally, unlike most other naturally occurring
green house gases (e.g., CO2, CH4), SF6 is only slowly decomposed; therefore its
contribution to global warming is expected to be cumulative and long lasting.
The strong infrared absorption of SF6 and its long lifetime in the environment
are the reasons for its extremely high global warming potential which for a 100yeartime horizon is estimated to be approximately 24,200 times greater (per
unit mass) than that of CO2, the predominant contributor to the greenhouse
effect. The concern about the presence of SF6 in the environment derives
exclusively from this very high value of its potency as a greenhouse gas.
However,
the
present
inventors
have
determined
that
given
the
environmental difficulty of SF6 [3], it is necessary to relax certain of the
requirements traditionally held as important and accept as an alternative gas,
compromise candidates with a lower GWP. For example, gases which are nontoxic are often inert with long atmospheric lifetimes which can yield high GWP.
By accepting a somewhat more reactive gas than SF6, the GWP can be greatly
reduced. Among the environmentally benign insulating gases alternative to SF6
gas, SF6/N2 gas mixtures (at different percentages of SF6) is regarded as one of
the most attractive gases because of the synergistic effect in electrical
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insulation performance. By using SF6/N2 gas mixture, it is to reduce SF6 gas
amount for power apparatus and this enables us to suppress the global
warming effect. SF6-N2 mixtures are the most thoroughly investigated among
all known gas mixtures. Based on the research conducted worldwide, the
optimum composition of SF6-N2 mixture for practical applications is considered
to be 40% SF6 - 60% N2 mixture [4]. But, recent studies carried out also
suggest that SF6-N2 mixture with SF6 concentration as low as 20% can be used
with an advantage [5]. Even with low SF6 content, this mixture has been found
to exhibit many of the desirable properties of pure SF6 when used as an
insulant.
Although, GIS has been in operation for several years, some of the problems
need full attention. These problems include generation of over voltages during
switching operations like enclosure faults and particle contamination. Sulphur
Hexafluoride (SF6) and SF6/N2 gas mixtures are generally found to be very
sensitive to field perturbations such as those caused by conductor surface
imperfections and by conducting particle contaminants [6-7]. A study of CIGRE
group suggests that 20% of failures in Gas Insulated Substations (GIS) are due
to the existence of various metallic contaminations in the form of loose
particles. The presence of contamination can therefore be a problem with gasinsulated substations operating at high fields. If the effects of these particles
could be eliminated, then this would improve there liability of compressed gas
insulated substation. It would also offer the possibility of operating at higher
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fields to affect a potential reduction in the GIS size with subsequent savings in
the cost of manufacture and installation. Defects like metallic particles or
protrusion or contamination on the surface of an epoxy spacer in GIS would be
a cause of partial discharges (PD) which may lower the corona onset and can
lead to final dielectric breakdown of the equipment. Metallic particles can be
either free to move in the GIS or they may be stuck either to an energized
electrode or to an insulator surface (spacer, bushing etc.).
Depending on the shape of the particles, as well as the geometry and
voltage levels of the system, the particles get more or less influenced by the
electric field which, in turn, makes them hazardous to the electrical system.
Particles in practical systems can exist in a wide variety of shapes and sizes,
and of materials of different densities. However, most contaminating particles
have been reported to be wire in shape in practical compressed gas insulated
systems. The particles may be conducting or insulating in nature, the latter
being not harmful. Conducting contaminants effects are more pronounced at
higher gas pressures [9]. Conducting contaminant effects are more pronounced
under application of lightning and switching impulse voltages superimposed on
power frequency voltages.
Metallic particles are known to drastically impair the insulation integrity of
compressed gas insulated sub-station (GIS) equipment. Such particles present
a special hazard when present in close proximity of support insulators. Most
GIS equipment manufacturers employ a variety of techniques and devices,
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such as electrostatic particle traps, to control metallic particle contamination.
Further research is vitally needed to detect the presence of these particles and
mitigate their effects, and thus minimize unplanned outages. Reliability of
electric supply is important and its economic impact is recognized by all users
and suppliers. Some of the methods of conducting particle control and deactivation are:
1. Conditioning by particle movement and trapping
2. Electrostatic particle traps
3. Dielectric coating
4. Discharging of conducting particles through radiation.
Dielectric coating:
A Dielectric coating on the inside of the enclosure can deactivate particles
by delaying their acquiring the electrostatic charge necessary for elevation until
significantly higher voltages than those needed to cause lift – off conditions
with bare electrodes are applied. The efficiency and effectiveness of dielectric
coatings on high voltage electrodes in gaseous insulation systems have been
studied over the past several years. Data indicate that the dielectric coatings
are beneficial and improve the breakdown voltage in gaseous insulation
systems. Moreover, results of some preliminary studies show that such
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coatings reduce the adverse impact of metallic particles in GIS equipment, thus
increasing the reliability of the system [10-11].
STATEMENT OF THE PROBLEM:
A method based on the particle motion is proposed to obtain the particle
trajectory in a Gas Insulated Bus duct (GIB). In order to determine the
movement of particle in a GIB, an inner conductor diameter of 55 mm and
outer enclosure diameter of 152 mm is considered. Aluminum, copper and
silver particles of size, length and radius of 10mm/0.25mm and also
10mm/0.3mm are considered to be present on the enclosure surface as well on
the epoxy coated spacer inclined at an angle 450 with respect to the enclosure
under SF6 Gas and SF6+N2 mixtures environment. The motion of a particle is
simulated by using the charge acquired by the particles, the macroscopic field
at the particle site, the drag coefficient, Reynolds’s number and coefficient of
restitution. The distance traveled by the particle which is calculated by using
appropriate equations is found to be in good agreement with the published
work for a given set of parameters.
To obtain the random behavior of moving particles, the calculation of
movement in axial and radial directions was carried out by Monte-Carlo
technique. Aluminum, copper and silver particles are considered for simulation
purpose.
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The thesis presents the movement pattern of metallic particles at different
operating voltages in a single phase isolated conductor Gas insulated Bus duct
(GIB) has been simulated with and without dielectric coated enclosure. The
purpose of dielectric coating is to improve the insulation performance. Free
conducting particles situated inside the GIS enclosure decrease high local
fields caused by conductor roughness. The coating reduces the charge on the
particle colliding with the coated enclosure, which in turn reduces the risk of
breakdown due to increase of the lift-off field of particles.
The equations governing the motion of the particle in a 64/500mm 3-phase
common enclosure GIS have been formulated to obtain the conducting
contaminant trajectories under pure SF 6 gas also with SF6+N2 Gas mixtures.
For
SF6+N2 gas mixtures with different concentrations of N2 in SF6+N2 gas
mixtures the viscosity of gas mixtures changes
number,
and hence the Reynolds
which is then substituted in motion equation to calculate the
movement of the particle. The result obtained for particle trajectory in three
phase common enclosure GIS with SF6+N2 gas mixtures is in good agreement
with published work of pure SF6 gas and new results have been presented and
analyzed in this thesis.
MAIN CONTRIBUTION OF THE THESIS:
In this thesis the following investigations have been carried out to obtain
the particle movement in a Gas Insulated Substation (GIS) or Gas Insulated
Bus duct (GIB).In order to determine the particle movement in a GIB of an
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inner conductor and outer enclosure diameters of 55mm and 152 are
considered.
Metallic particles like Al, cu and Ag of wire type are considered to be present
in Single phase GIB on bare electrode and also on coated enclosure under
application of power frequency voltages and also with lightning impulse voltage
superimposed on power frequency voltages with SF6 as well as with SF6+N2 gas
mixtures as dielectric medium have been presented and analyzed for voltages
of 75kV, 100kV, 120kV, 132kV, 145kV, 160kV, 200kV and 245kV respectively.
The following studies have been analyzed and presented in this thesis:
A) Modeling and analysis of a particle movement in a single phase GIB with
Uncoated enclosure with electric field effect under pure SF6 gas environment is
presented as follows:

Modeling and analysis of particle trajectories in gas insulated Bus
duct on application of power frequency voltage.

Modeling and analysis of particle trajectories in gas insulated Bus
duct on application of lightning impulse voltage superimposed on
power frequency voltage.

Modeling and analysis of particle trajectories in gas insulated Bus
duct on application of switching impulse voltage superimposed on
power frequency voltage on power frequency voltage.
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B) Modeling and analysis of a particle movement in a single phase GIB with
Uncoated enclosure with electric field effect SF6+N2 gas mixtures environment
is presented as follows:

Modeling and analysis of particle trajectories in gas insulated Bus
duct on application of power frequency voltage.

Modeling and analysis of particle trajectories in gas insulated Bus
duct on application of lightning impulse voltage superimposed on
power frequency voltage on power frequency voltage.

Modeling and analysis of particle trajectories in gas insulated Bus
duct on application of switching impulse voltage superimposed on
power frequency voltage.
C) Modeling and analysis of a particle movement in a single phase GIB under
coated enclosure condition with electric field is presented as follows:

Modeling and analysis of particle trajectories in gas insulated Bus
duct on application of power frequency voltage with pure SF6 gas.

Modeling and analysis of particle trajectories in gas insulated Bus
duct on application of power frequency voltage with SF6+N2 gas
mixtures.
D) Modeling and analysis of a particle on epoxy coated conical spacer in a
single phase GIB with contaminant at different positions on conical spacer
inclined at an angle of 45 degrees under application of typical single phase
power frequency voltages.
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E) Modeling and analysis of a particle movement in three phase common
enclosure GIS under application of power frequency voltage with SF6 gas and
also with SF6+N2 gas mixtures considering wire like contaminant and also with
spherical contaminant.
ORGANISATION OF THESIS:
CHAPTER I presents introduction to Gas Insulated Substations and adverse
effects of conducting contaminant in GIS are discussed. Since SF6 Gas is the
main dielectric medium which is a green house gas with highest GWP, the best
substitute for SF6 gas is presented with literature survey.
CHAPTER II Presents the statement of problem, Main contribution of the
thesis and Organization of the thesis.
CHAPTER III presents the modeling of metallic particles in a bare electrode
and coated enclosure system with SF6 gas as well as with SF6+N2 gas mixtures
as dielectric medium under application of power frequency voltage and also
with lightning impulse voltage superimposed on power frequency voltage.
Further modeling of single phase GIB With contaminant on the spacer is
presented .Movement pattern is obtained for metallic particle considered to be
present at different positions on the conical spacer inclined at 45 deg with
respect to enclosure are presented.
CHAPTER IV presents the modeling and analysis of metallic particle in
common enclosure with pure SF6 gas as well as with SF6+N2 gas mixtures. Wire
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like and spherical particles are considered under application of power
frequency voltage.
CHAPTER V presents the conclusions and results of dissertation. The future
scope of this work is also discussed.
CONCLUSIONS:
Gas insulated substation, which has become the essentiality in this rapid
energy demanding era, has inspired many with its varied characteristics. Apart
from being compact it proved to be a fail- safe solution and also provided
economic solution in easier installation and maintenance. The tech savvy and
aesthetic GIS can be adopted almost anywhere, which was earlier only a
dream. In my work, the major study constituted the discussion of excellent
properties of the insulating gas ‘SF 6’ its potentiality and its possible effect on
the environment has become a burning topic as “GREEN HOUSE” gas. Among
the environmentally benign gases, alternative to SF6 gas, the SF6- N2 gas
mixtures is regarded as one of the most attractive gases for the same setup
used for SF6, because of the synergetic effect in electrical insulation
performance. As the presence of conducting contaminants is a major threat to
GIS leading to reduction in insulation integrity, the time taken for the
breakdown of insulation can be estimated by obtaining the contaminant
particle trajectory, which is carried out here with pure SF 6 gas and SF6/ N2 gas
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mixtures. Defects occurring in Gas Insulated Substations and the methods for
their control and deactivation are reviewed.
An uncharged metallic particle resting on bare electrode in a Gas
Insulated System will gradually acquire charge due to the application of electric
field around it. The charge accumulated is a function of Electric field, shape,
size and orientation of the particle. Three forces act on the particle: eg.
Electrostatic force and oppositely acting gravitational and drag forces. When
electrostatic force exceeds the gravitational and drag forces the particle lifts
from its position. A further increase in the applied voltage makes the particle
move into the inter electrode gap in the direction of applied field. This increases
the probability of a flashover. If an investigation reveals the presence of a
particle, it is required to analyze the particle i.e., find the material and
approximate size of the particle as certain particles are more deleterious than
others The influence of increased voltage level on the motion of the particles is
also investigated. If the calculations, as described above, are performed at a
higher voltage level, the particle will lift higher from the surface and the time
between bounces will increase .Results are obtained with pure SF6 gas and also
with SF6+N2 gas mixtures. The results obtained with mixture of gases are in
good agreement with the published work of pure SF6 gas and new results with
mixture of gases are presented. The results show that the movement of the
particles increases as the applied voltage increases and it is found that the
movement of aluminium particle is more when compared to copper and silver
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particles due to its lighter mass, and hence acquiring greater charge/mass
ratio.
The purpose of dielectric coating is to improve the insulation performance.
Free conducting particles situated inside the GIS enclosure decrease high local
fields caused by conductor roughness. The coating reduces the charge on the
particle colliding with the coated enclosure, which in turn reduces the risk of
breakdown due to increase of the lift-off field of particles. As the thickness of
the coating increases, the lift –off field increases and hence the movement of
the particle decreases. Also the metallic contaminant have been considered on
the conical spacer at different positions on the spacer reveal that the movement
of the particle increases as the conducting contaminant is assumed to be
present nearer to the hV conductor.
The work reported in this thesis also deals with the movement of the
metallic particles in a 3-phase common enclosure bus duct with bare
electrodes. The macroscopic electric field at the surface of the enclosure for the
3-phase system is calculated in Cartesian coordinates. The electric field has
been used to determine the charge as well as the force on the particle. The
radial movement is calculated using the standard equation of motion. The
calculations have been done for power frequency voltages. The results obtained
from the calculations show that additional information about the particle could
be obtained when voltage dependence is introduced in the calculations. The
results are presented and analyzed by considering wire like particle and also
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spherical particle under pure SF6 and SF6+N2 gas mixtures. As the operating
voltage increases the axial and radial movement of the particles also increases
in both the cases. In case of spherical particle, as the radius of the particle
increases, the charge/mass ratio decreases resulting in the increase of lift-off
field, thereby, decreasing the movement of the particle. It is found that 40%60% of N2 in SF6+N2 gas mixtures is the optimal mixture which can substitute
for same set up of electrical equipment with pure SF6 gas. As the concentration
of N2 in SF6 + N2 changes the viscosity of gas mixtures changes and hence the
movement of the particle also changes and further, it is observed that the
movement of the particle for optimal mixture of gases is found to be less when
compared to the movement of particle under pure SF6 gas environment.
REFERENCES:
[1]Kevork Mardikyan, Orhan Ersen, Ergun Canarsian, "Ac Breakdown Strength
of N2, SF6 and a Mixture of N2+SF6 containing a small amount of SF6”.IEEE
conference on Electrical Insulation, Canada, June 16-19, 1996.
[2] Emel Önal, “Breakdown Characteristics of Gases in Non Uniform Fields”.
Journal of Electrical and Electronics Engg-Istanbul University, Vol 4 pp.11771182, 2004.
[3] NIST Technical note-1425 : Gases for Electrical Insulation and arc
interruption: Possible present and future alternatives to pure SF6 by
L.G.Christophorou , J.K.Olthoff and D.S.Green.
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[4]] L. G. Christophorou, J. K. Olthoff, R. J. Van Brunt, “SF6 /N2 mixtures,
basic and HV Insulation properties”, IEEE Transactions,Dielectrics and
Electrical Insulation 2 (5), October 1995 pp 952-1002.
[5] Y.Hoshina et.al “ Dielectric properties of SF6/N2 gas mixtures on full scale
model of the gas insulated bus bar ” , IEEE Transactions ,Dielectrics and
Insulation 2000 IEEE pp-2129-2134.
[7] N.H. Mallik and A.H.Qureshi , “Breakdown gradients in SF6-N2 ,SF6-AIR
and SF6-Co2 Mixtures” . IEEE Transactions on Electrical Insulation Vol EI-15
No.5 october 1980.
[8] N.J.Felici, “Forces et charges de petits objects en contact avec une electrode
affectee d’un champ electrique”; Revue generale de I’electricite, pp. 1145-1160,
October 1966.
[9] Olivier. G, Gervais.Y, Mukhedkar.D, "A new approach to compute uniform
field breakdown of gases", IEEE Trans. on Power Apparatus and Systems, Vol.4
PAS-97, pp.1177-1182, 2004.
[10] G.V.Nagesh Kumar, J. Amarnath, B.P. Singh and K.D. Srivastava, “Electric
Field Effect on Metallic Particle Contamination in a Common Enclosure Gas
Insulated Bus duct ”, IEEE Transactions in Dielectrics and Electrical
Insulation, April 2007, PP. 334-340.
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[11] G.V.Nagesh Kumar, J. Amarnath, B.P. Singh and K.D. Srivastava,
“Reduction of Particle Movement in a 3 phase common enclosure GIS with
Dielectric Coated Electrodes” IEEE International Conference on Control,
Instrumentation and Systems, University of Perdinya, Srilanka, 8th – 10th
August 2007
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LIST OF PUBLICATIONS FROM THIS THESIS:
TECHNICAL PUBLICATIONS IN INTERNATIONAL JOURNALS:
1) D.Padmavathi, J.Amarnath and S.Kamakshaiah “Assessment of Dielectric
Behavior of Sf6/N2 gas mixtures in the presence of
metallic particle
contamination in a common enclosure gas insulated bus duct”,
International
journal of applied Engineering and Research, ISSN 0973-4562 , Volume 5
Number 10 (2010) pp. 1789–1787.
2) D.Padmavathi, J.Amarnath and S.Kamakshaiah “Effect of lightning impulse
voltage on the performance of 1-phase gas
insulated bus duct in the
presence of metallic particle contamination with SF6/N2 gas Mixtures”
(Accepted for Journal of theoretical and applied and information technology
International Journal –September2010 volume)
3) D.Padmavathi, J.Amarnath and S.Kamakshaiah “Conducting contaminant
trajectory on Epoxy coated 1-Φ in Gas insulated Bus duct”(paper accepted
for International journal of Industrial Engg and Technology,IJIET).
4) D.Padmavathi, J.Amarnath and S.Kamakshaiah “Conducting contaminant
Movement restriction using coated enclosure in a single phase Gas insulated
bus duct with SF6/N2 gas mixtures” (communicated to ARPN Journal) .
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INTERNATIONAL CONFERENCES:
1) D.Padmavathi, J.Amarnath and S.Kamakshaiah
“Behavior of metallic
particle contamination in SF6/N2 Gas mixtures under the Influence of electric
field in a Common enclosure gas insulated bus duct”, Proceedings of the 16th
international symposium on high voltage ,Aug-2010,Cape Town, South Africa
2) D.Padmavathi, J.Amarnath and S.Kamakshaiah “Assessment of Dielectric
Behavior of SF6/N2 Gas Mixtures with Dielectric coated Enclosure in A 1Phase Gas Insulated Bus duct In
the Presence Of metallic Particle
Contamination” Proceedings of the 16th international symposium on high
voltage engineering -Aug-2010,Cape Town, South Africa
3) D.Padmavathi, J.Amarnath and G.V.Nagesh Kumar, Deepak Chowdary
“Dielectric Behavior of Compact Design Three Phase Coated Gas Insulated Bus
duct with Metallic Particle Contamination”, International Conference on High
Voltage Engineering and Application,
Chongqing, China, November 9-13,
2008
4) D.Padmavathi, J.Amarnath and S.Kamakshaiah “Effect of Lorentz Force
on The Conducting Contaminant Trajectory In A Three Phase Gas
Insulated Bus duct”, CEIDP-2009 18th-21st Virginia Beach, USA
5) D.Padmavathi, J.Amarnath and S.Kamakshaiah “Determination of particle
Movement on Epoxy Coated Spacer in A single phase Gas Insulated Bus duct”,
22
presented at International conference on
Power Modulator and high voltage
Engg Atlanta from May 2010.
6) D.Padmavathi, J.Amarnath and S.Kamakshaiah “ Determination of
conducting contaminant trajectory on Epoxy coated spacer using Monte-Carlo
Technique” International conference on high voltage Engineering and
Application (Oct ICHVE2010), Neworlans,USA.. (Accepted).