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    Evaluation on flashover voltage property of snow accreted insulators for overhead transmission lines, part I - field observations and laboratory tests to evaluate snow accretion properties

    Yaji, K. ; Homma, H. ; Sakata, G. ; Watanabe, M.
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 21 , Issue: 6
    DOI: 10.1109/TDEI.2014.004564
    Publication Year: 2014 , Page(s): 2549 - 2558

    IEEE Journals & Magazines

    This paper presents evaluation of snow accretion properties of long-rod and cap & pin insulators focusing on the phenomena found in the snowstorm in 2005, which related to wet snow accretion packed with sea-salt. Field observations at severe natural environment and laboratory tests under defined conditions were parallelly carried out in order to clarify wet snow accretion process under various conditions. In field observations, it was confirmed that snow easily accreted on insulators at temperature range especially between 0 and +1.0°C. The long-rod insulator's sheds were bridged more easily than that of cap & pin type because of its narrower shed spacing. In laboratory tests, cylindrical snow accretion, which was found in the snowstorm in 2005, was achieved. The mechanisms on explaining snow accretion on long-rod insulators were found to be similar to those confirmed for wires. The laboratory simulations agree well with the field observations. In order to estimate the amount of snow flux on insulators caused by a snow event for given climatic conditions, an index called the snow accretion potential ability (SAP) was proposed. SAP is defined by using the snow flux and associated with the weight term in the index for the snow stress product (SSP). SAP was adopted to evaluate snow accretion characteristics by field observations and laboratory tests, and the snow accretion phenomenon during a snowstorm in 2005 was discussed. View full abstract»

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    Analysis for calculation method of shielding flashover rate on common-tower double transmission line

    Meisheng Chang ; Gailian Yuan
    Electricity Distribution (CICED), 2010 China International Conference on

    Publication Year: 2010 , Page(s): 1 - 5

    IEEE Conference Publications

    Based on the EGM (electric geometry method), some problems when calculating the ratio of exposure arc to exposure arc and shielding arc, exposure arc projection, striking distance coefficient, shielding failure flashover rate etc are analyzed and discussed. It points out that the general maximum striking distance formula is not appropriate for some conditions. Calculating shielding failure flashover rate by current density probability function is proposed; It also suggested that three phase conductors use corresponding striking distance coefficient with the conductor height. View full abstract»

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    Effects of Parameters on The Phase-to-Phase Flashover Characteristics of UHV Transmission Lines

    Miyake, K. ; Watanabe, Y. ; Ohsaki, E.
    Power Engineering Review, IEEE

    Volume: PER-7 , Issue: 10
    DOI: 10.1109/MPER.1987.5526770
    Publication Year: 1987 , Page(s): 68 - 69

    IEEE Journals & Magazines

    First Page of the Article
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    Variation of ice surface conductivity during flashover

    Zhang, J. ; Farzaneh, M. ; Chen, X.
    Electrical Insulation and Dielectric Phenomena, 1995. Annual Report., Conference on

    DOI: 10.1109/CEIDP.1995.483767
    Publication Year: 1995 , Page(s): 479 - 483
    Cited by:  Papers (7)

    IEEE Conference Publications

    In this paper, the variation of conductivity of melting water which drips from ice samples during the de-icing process and flashover was investigated. An equivalent surface conductivity was introduced and the relationship between it and the conductivity of freezing water was determined. These results are used in the modeling of flashover along ice-covered insulators View full abstract»

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    Monte Carlo Simulation of Surface-Charging Phenomena on Insulators Prior to Flashover in Vacuum

    Kai-kun Yu ; Guan-Jun Zhang ; Nan Zheng ; Raitses, Y. ; Fisch, N.J.
    Plasma Science, IEEE Transactions on

    Volume: 37 , Issue: 5
    DOI: 10.1109/TPS.2009.2015450
    Publication Year: 2009 , Page(s): 698 - 704

    IEEE Journals & Magazines

    Before flashover across an insulator under high electric field in vacuum, there are charging phenomena occurring on the insulator surface, which significantly affect the developing process of flashover. Based on the secondary-electron-emission-avalanche model and by using the Monte Carlo method, a 2-D analysis of surface charge density on cylindrical and conical insulators prior to flashover in vacuum has been performed under unipolar voltage. Different materials are employed, i.e., alumina ceramic, PTFE, PMMA, and PI. The influences of materials, voltage amplitudes, and coning angles on charge distribution are investigated. The results reveal that negative charges exist in a small surface region near the cathode, while the surface charges positive in a larger region away from the cathode. With increasing applied voltage, both the negative charge density and region decrease, and even vanish, whereas both the positive charge density and region increase, and the peaks of both regions move toward the cathode. For the conical insulator with a negative angle, the positive charge density is greater than that with a positive angle, and the simulation describes well experimental data relating the coning angle, the surface charge, and the flashover voltage. View full abstract»

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    Variation in time lags of vacuum surface flashover utilizing a periodically grooved dielectric

    Guoxin Cheng ; Dan Cai ; Zhiqiang Hong ; Lie Liu
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 20 , Issue: 5
    DOI: 10.1109/TDEI.2013.6633728
    Publication Year: 2013 , Page(s): 1942 - 1950
    Cited by:  Papers (1)

    IEEE Journals & Magazines

    In a wide variety of high-power pulsed devices, vacuum surface flashover plays an important role in the system performance. The capability of grooved dielectric to hold off high-voltage pulse is investigated experimentally by using a long pulse electron beam accelerator, which is capable of generating a quasi-square wave with pulse duration of 180 ns and output voltage of 100-400 kV. It is found that both concavely and convexly grooved dielectrics increase promisingly the flashover time lags. With groove width of 2 mm, depth of 2 mm, period of 4 mm, electrode gap spacing of 100 mm, and diode voltage of 265 kV, the flashover time lag for polycarbonate is found to increase from 93.0 ns to 182.6 ns. While for polytetrafluoroethylene, its flashover time lag is increased from 45.0 ns to 81.2 ns, and for high-density polyethylene, its flashover time lag is increased from 72.4 ns to 100.5 ns. Electrical and optical diagnoses on temporal evolution of flashover channel confirm that surface flashover in vacuum is characterized by three-phase development, namely the secondary electron emission avalanche (SEEA), impact ionization in desorbed gas, and the final plasma driven breakdown. Based on this analyzing, it is found that the increase of flashover time lags is mainly due to the suppressing of SEEA process by using grooved structures. View full abstract»

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    Improvement of particle-initiated DC flashover characteristics by using electrode and surface shapes in SF6 gas

    Lee, H.-H. ; Egashira, T. ; Hara, M.
    Properties and Applications of Dielectric Materials, 1991., Proceedings of the 3rd International Conference on

    DOI: 10.1109/ICPADM.1991.172114
    Publication Year: 1991 , Page(s): 529 - 532 vol.1
    Cited by:  Papers (1)

    IEEE Conference Publications

    To improve the withstand voltage under particle-contaminated conditions in SF6 gas, the electrode and surface shapes of a spacer are changed simultaneously. It is shown that the breakdown voltage is considerably influenced by the distance from a particle to a rib. The characteristics are determined mainly by the field relaxation effect near the electrode and a long distance from a particle to a rib, and mainly by the barrier effect along the surface for a short distance. Therefore, it is desirable for high withstand performance under particle contaminated conditions that the electric field near the electrode decreases while keeping the barrier effect along the surface to some degree. In the case of a thick rib, the severest insulation condition takes plane when a particle is located at the rib top View full abstract»

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    Development of contamination flashover pre-warning system and analysis of operating experience

    Chenlong Zhao ; Hongwei Mei ; Mingxi Zhu ; Hanqi Dai ; Liming Wang ; Zhicheng Zhou
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 22 , Issue: 4
    DOI: 10.1109/TDEI.2015.004472
    Publication Year: 2015 , Page(s): 2234 - 2241

    IEEE Journals & Magazines

    Pollution flashover has been a serious threat to the operation safety for the power system. Online monitoring is one most important way for the operation and maintenance of power system. The leakage current on insulator surface is a comprehensive reflection of the insulator surface contamination, environmental conditions and other affecting factors. The purpose of outdoor insulation state on-line monitoring could be achieved by measuring and monitoring the leakage current on insulator surface. This paper showed that close relationship existed between leakage current in both low humidity and saturated moisture conditions. A negative exponential relationship exists between pollution flashover voltage and a new parameter I* which could reflect the insulator shape and the maximum leakage current under saturated humidity. The flashover voltage under saturated humidity could be predicted through current obtained under low humidity conditions. A contamination pre-warning system was constructed in accordance using this mathematical model combined with some hardware system. Pilot systems were established in some typical polluted area in Jiangsu Province. The results showed that the system could achieve online monitoring purposes. View full abstract»

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    Method of calculating shielding failure flashover times of transmission line in complex terrain area

    Qing-zhou Zhao ; Qing Yang ; Hao-yuan Zheng ; Wen-xia Sima ; Tao Yuan ; Jian-biao Li
    High Voltage Engineering and Application (ICHVE), 2012 International Conference on

    DOI: 10.1109/ICHVE.2012.6357120
    Publication Year: 2012 , Page(s): 330 - 333

    IEEE Conference Publications

    Calculating shielding failure flashover rate of transmission line with regulation method, EGM method and LPM method, the height of conductor and ground wire are often expressed by average height, the terrain feature are often expressed by ground obliquity. If the actual line parameters are beyond the scope of the effective calculation conditions, traditional methods can't reflect the influence of sag and line corridor's complex terrain area. In recent years, some scholars put forward to select multiple tangent planes of a line span, then calculated the shielding failure flashover rates of every tangent planes to reflect the line span's lightning protection performance, but it was complicated to get the ground obliquities of every tangent planes. A new approach for calculating shielding failure flashover times in complex terrain area was presented, which was based on the electro-geometric model (EGM), the new method considered of the line corridor's micro-topography and the relative position among the ground wire, the conductor wire and the ground, a line span was taken as the research object, got the shielding failure flashover times of the line span through calculating the conductor exposed surface's horizontally-projected area. A 500kV transmission line in complex terrain area was taken as an example, the calculation results shown that using this method can obtain a line span's lightning protection performance simple and exactly, and reflect the influence of line corridor's complex terrain area better, which also provide a reference for differentiation technology and strategy of lightning protection. View full abstract»

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    Flashover rate due lightning in overhead distribution lines

    Vasquez, C. ; Osal, W. ; Blanco, C.
    Electrical Power Quality and Utilisation, 2007. EPQU 2007. 9th International Conference on

    DOI: 10.1109/EPQU.2007.4424191
    Publication Year: 2007 , Page(s): 1 - 4

    IEEE Conference Publications

    This paper has as objective to determine the flashover rate by lightning in overhead distribution lines of 24 kV and the analysis of the protections alternatives. The shield wire or the surge arrester located in distributed form can be used for the protection of the overhead distribution lines. The flashover rate calculated for the lines without protection is gotten of two (2) ways: through the analysis of the fault statistic for an 11 year-old period and through the software SISDEA V1.0. For the calculations of the flashover rate of these lines protected with shield wire and surge arrester located in distributed form only is used the software SISDEA V1.0. The results show the calculations of the flashover rate for lines protected and not protected shield wire and surge arrester located in distributed form. The conclusion shows the importance to carry out studies like these for improvement the quality of the electrical service for the clients. View full abstract»

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    Pulsed Flashover of Insulators in Vacuum

    Milton, O.
    Electrical Insulation, IEEE Transactions on

    Volume: EI-7 , Issue: 1
    DOI: 10.1109/TEI.1972.299183
    Publication Year: 1972 , Page(s): 9 - 15
    Cited by:  Papers (67)

    IEEE Journals & Magazines

    Dielectric specimens in the shape of a frustum of a cone were evaluated for surface flashover strength in vacuum of 10-5 torr. Data were obtained for positive and negative pulses of several hundred kilovolts amplitude and with rise times in the nanosecond and microsecond region. The results indicate that most materials exhibit a greater resistance to breakdown if the base of the cone is at the cathode and that the strength is greatly affected by the angle that the dielectric makes with the applied field. Lucite, polystyrene, polyethylene, cast Nylon, and 7740 glass are shown to be relatively resistant to flashover in comparison with the ceramics and molded plastics. It is also observed that the surface strength in vacuum is a small fraction (approximately 1/10 or less) of the volume strength and consequently breakdown through the bulk seldom occurs. Data are given for several common insulating materials. View full abstract»

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    Optical emission characteristics of polycrystalline diamond during surface flashover in vacuum

    Kirkici, H.
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 4 , Issue: 6
    DOI: 10.1109/94.654719
    Publication Year: 1997 , Page(s): 822 - 826
    Cited by:  Papers (3)

    IEEE Journals & Magazines

    This work presents experimental results of optical emission from polycrystalline, as well as single crystal diamonds, during the surface flashover events in a vacuum environment. Optical emission spectra were recorded and the source of this luminosity was investigated. Analysis showed that the surface flashover events were associated with relatively high intensity optical emissions. The light emission started much earlier than the voltage collapse, increased very rapidly with the breakdown, and eventually ended after few seconds; much later than the voltage across the surface was recovered. The polycrystalline diamond sample used in the experiments was produced by a microwave plasma CVD (chemical vapor deposition), and the sample surface was polished to optical quality before the experiments. The electrode material was copper, and a dc voltage was applied between the electrodes. Surface flashover voltage characteristics and breakdown voltage waveforms of both samples were determined View full abstract»

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    Influence of conductive particles on the impulse flashover of disc spacer in compressed SF6

    Yu cunyi
    Conduction and Breakdown in Solid Dielectrics, 1992., Proceedings of the 4th International Conference on

    DOI: 10.1109/ICSD.1992.224944
    Publication Year: 1992 , Page(s): 256 - 260

    IEEE Conference Publications

    The influence of a conductive particle fixed on the spacer surface on the impulse flashover value in compressed SF6 was investigated experimentally. Both smooth and corrugated spacer surfaces were studied. The results show that the metal particle could reduce the impulse flashover level by about 33%. It is also shown that the tangential component of the field strength is mainly responsible for the reduction of the flashover level. The results demonstrate that for impulse performance the corrugated spacer is much better than the smooth spacer View full abstract»

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    Flashover on d.c. machines

    Swinnerton, B.R.G. ; Turner, M.J.B.
    Electrical Engineers, Proceedings of the Institution of

    Volume: 115 , Issue: 7
    DOI: 10.1049/piee.1968.0178
    Publication Year: 1968 , Page(s): 980 - 986

    IET Journals & Magazines

    This paper presents a review of published work on flashover, mainly of Russian, German and American origin. The information obtained from these sources, combined with supporting experimental work, enables a comprehensive explanation of the phenomena to be given. A list of running conditions for which flashover has been reported is given. There are two basically different causes of flashover; they are (a) severe brush arcing, and (b) interbar arcing caused by conducting debris etc. in the gaps. The voltage distribution around the commutator is then critical in determining whether flashover occurs when either of these conditions exists. Methods of avoiding or reducing the risk of flashover are suggested. A comprehensive list of references is included. View full abstract»

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    Impulse flashover along the outer surface of a cylindrical dielectric solid with a gas layer inside

    Ohki, M. ; Saito, S.
    Physical Science, Measurement and Instrumentation, Management and Education - Reviews, IEE Proceedings A

    Volume: 135 , Issue: 2
    DOI: 10.1049/ip-a-1.1988.0016
    Publication Year: 1988
    Cited by:  Papers (1)

    IET Journals & Magazines

    Impulse flashover voltage along the outer surface of a layered dielectric composition, composed of two coaxial hard glass cylinders and an inner gas layer, is known to have a V-shaped curve as a function of pressures inside the gas layer. It is the purpose of the paper to clarify the reason for this V-shaped curve. Variation of electric field intensity along the outer surface caused mainly by ionisation in the gas layer, and partly by the residual charges on the inner surface of the outer cylinder is found to play an important role in determining the flashover voltage View full abstract»

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    Surface flashover sustained by electrostatic surface charge on epoxy resin insulator in SF6 [GIS insulators]

    Wang, C.X. ; Wilson, A. ; Watts, M.W.
    Dielectric Materials, Measurements and Applications, 1992., Sixth International Conference on

    Publication Year: 1992 , Page(s): 182 - 185
    Cited by:  Papers (1)

    IET Conference Publications

    It has been confirmed that sufficiently high electrostatic surface charge density can sustain surface flashover when the stored surface energy released can cause further ionisation and establish a chain reaction. Therefore, in addition to the widely reported results that surface charges can aggravate the triple junction field enhancement under certain conditions, it is now clear that once triggered, surface flashover can self-propagate a long distance away from the initiation sites, resulting in unexpected and erratically low flashover voltages. The proposed self-sustained surface flashover criterion has been tested to apply for different geometries and at various SF6 pressures. The criterion simply states that the electrostatic surface energy should be sufficient for renewed ionisation activities View full abstract»

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    High-voltage D-C flashover of solid insulators in compressed nitrogen

    Trump, John G. ; Andrias, James
    Electrical Engineering

    Volume: 60 , Issue: 11
    DOI: 10.1109/EE.1941.6434541
    Publication Year: 1941 , Page(s): 986 - 989

    IEEE Journals & Magazines

    HIGH-voltage apparatus insulated by compressed gas requires the use of solid insulating supports. It is generally recognized that even in a uniform field the flashover voltage of such solid insulation is considerably lower than for the gas-filled gap of equal length. An increase in the allowable gradient along such insulators would in general result in a reduction in the size, weight, and cost of gas-insulated apparatus, and must therefore be considered an important and fundamental objective of high-voltage engineering. It is probable that the flashover strength of solid insulators may be brought closer to that of the gases in which they are immersed, or to their inherent volume breakdown strength, through a better understanding of the influence on insulator flashover of such factors as material, surface condition, corrugations, and gas pressure. Most of the scant literature on this subject is restricted to relatively low alternating voltages, small samples of solid dielectrics, or to special insulator shapes in non-uniform fields.1 Reher studied the flashover of plain cylinders of ebonite, paraffin, and porcelain in dry air at pressures up to 15 atmospheres, using alternating voltages up to 140 kv maximum.2 Goldman and Wul3 have investigated the flashover of plain ebonite cylinders in nitrogen with alternating voltages up to 125 kv maximum and pressures up to 20 atmospheres. The present paper reports d-c flashover values up to 250 kv across short cylindrical insulators placed in the uniform field between metallic electrodes. These studies were made on both plain and corrugated cylinders of three dissimilar insulating materials immersed in dry nitrogen at gauge pressures up to 400 lbs. per square inch. View full abstract»

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    Room flashover and subsequent filling of the structure with smoke

    Lilley, D.G.
    Energy Conversion Engineering Conference, 2002. IECEC '02. 2002 37th Intersociety

    DOI: 10.1109/IECEC.2002.1392022
    Publication Year: 2002

    IEEE Conference Publications

    This work describes room flashover and subsequent filling of the structure with smoke. Modeling of the progress of the smoke is possible with a variety of available computer codes, thus permitting calculations of temperature and smoke level in different rooms as time progresses. The CFAST computer code (Consolidated model of Fire growth And Smoke Transport) is used to calculate temperatures and smoke levels in the various rooms of the house initially. Experimental work assists in understanding fire behavior in structural fires. View full abstract»

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    Numerical study on high power microwave flashover and breakdown on output-window by EM-fluid simulation

    Dong Ye ; Zhou Qian-Hong ; Yang Wen-Yuan ; Dong Zhi-Wei ; Zhou Hai-Jing
    Plasma Sciences (ICOPS), 2015 IEEE International Conference on

    DOI: 10.1109/PLASMA.2015.7179957
    Publication Year: 2015 , Page(s): 1

    IEEE Conference Publications

    Summary form only given. An electromagnetic-field FDTD method coupled with plasma fluid model is put forward to study the phenomena of High Power Microwave flashover and breakdown on output-window. The numerical results could be concluded as follows. For flashover and breakdown on outer surface, output microwave pulse is shortened without cut-off; there is a standing-wave distribution of electric field RMS (Root-Mean-Square) value before the window with fixed-positions of wave nodes and antinodes; there is a ultra-high-density (~1021/m3) and ultra-thin (~mm) plasma shell with slow diffusion, microwave could penetrate the plasma-shell partly; the shortening of output microwave is caused by plasma absorption mostly. The output pulse of microwave could be lengthened by decrease the initial density or depth of plasmas; the other way is to shorten incident microwave pulse or decrease the value of incident microwave power. For flashover and breakdown on inner surface, there is also a standing-wave distribution of electric field RMS value before the window but the positions of wave nodes and antinodes varying with time; the plasma region move to the direction of microwave source; with strong-outgassing, output microwave pulse is shortened without cut-off, there are a “thread-like” ultra-high-density (~1021/m3) and ultra-thin (~mm) plasma regions with slow diffusion, the distance between two “thread-like” region is about a quarter of microwave wavelength, the shortening of output microwave is caused by plasma absorption mostly; with weak-outgassing and low electric field value, the output pulse of microwave are lengthened but cut-off finally, there are a “belt-like” high-density (~1018/m3) and thin (mm~cm) plasma regions with fast diffusion, the distance between two “belt-like” region is about a quarter of microwave wavelength, the shortening of- output microwave is caused by plasma absorption mostly; with weak-outgassing and high electric field value, output pulse of microwave is cut-off quickly, a “block-like” diffuse ultra-high-density (~1021/m3) and deep (~cm) plasma regions are formed with very fast diffusion, the shortening of output microwave is caused by plasma reflection mostly. View full abstract»

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    Atmospheric flashover in a symmetric electric field geometry

    Rogers, G. ; Neuber, A. ; Hatfield, L. ; Laity, G. ; Frank, K. ; Dickens, J.
    Power Modulator and High Voltage Conference (IPMHVC), 2010 IEEE International

    DOI: 10.1109/IPMHVC.2010.5958293
    Publication Year: 2010 , Page(s): 51 - 54
    Cited by:  Papers (1)

    IEEE Conference Publications

    In an attempt to identify the mechanisms leading to pulsed dielectric surface flashover in atmospheric conditions, surface flashover across a magnesium fluoride (MgF2) window was studied. The electrode configuration and the applied pulsed voltage level were chosen such that the generated electric field was symmetric with respect to the centerline between the electrodes. That is, neither electrode was favored with respect to flashover/breakdown initiation. A semiconductor-switched 32 kV pulse with 140 ns rise time was applied to the 8 mm wide flashover gap in air, nitrogen, and oxygen at atmospheric pressure. Fast voltage and current measurements along with nanosecond imaging revealed four stages of flashover development: (1) Onset of a cathode directed streamer with a charge on the order of 100 pC and traveling with a speed of ~1 mm/ns at a macroscopic field level of ~10 kV/cm associated with a slow current rise (on the order of 10-3 A/ns) temporarily augmented by (2) a 5 ns wide current spike at the moment when the streamer reaches the cathode followed by (3) a cathode directed streamer focused toward the center of the flashover gap with a slow rising current leading to (4) a sharp current rise (on the order of 10 A/ns) reaching roughly a circuit limited 45 A about 20 ns after the return strike meets an anode directed streamer. Although present in all tested gases, the current spike at the end of stage (2) is most different for all three gases and having the greatest impact in air. View full abstract»

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    Dielectric surface flashover in vacuum at cryogenic temperature (100 K)

    Neuber, A. ; Krompholz, H. ; Hatfield, L.L.
    Electrical Insulation and Dielectric Phenomena, 1997. IEEE 1997 Annual Report., Conference on

    Volume: 2
    DOI: 10.1109/CEIDP.1997.641139
    Publication Year: 1997 , Page(s): 575 - 578 vol.2
    Cited by:  Papers (5)

    IEEE Conference Publications

    Recent developments in high power systems use cryogenic components, where the performance of insulators at such low temperatures is unknown. In a fast coaxial setup, electrodes and dielectric sample are cooled to less than 100 K in vacuum, and the flashover initiation processes for gap distances on the order of 1 cm are characterized using fast electrical and optical diagnostics. As reported before, two development stages can be distinguished: a first phase with slowly rising current and the presence of free electrons, with a duration of 10-50 ns, and a second stage with a fast current rise due to gaseous ionization and collision dominated electrons. First experiments comparing cooled samples and samples at room temperature do not show discernible differences for Lexan. For Alumina, however, an increase of the duration of phase 1 is observed, with a higher current amplitude at the transition from phase one to phase two. Also, the current rise in phase two is reduced. These results indicate a temperature dependence of the electron induced outgassing process which is expected to cause the transition from phase one to phase two View full abstract»

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    Influence of non uniformity of pollution thickness on insulator flashover under impulse voltage

    Slama, M.E.-A. ; Beroual, A. ; Hadi, H.
    High Voltage Engineering and Application (ICHVE), 2010 International Conference on

    DOI: 10.1109/ICHVE.2010.5640711
    Publication Year: 2010 , Page(s): 528 - 531

    IEEE Conference Publications

    This paper is aimed at the influence of the linear non uniformity of pollution layer on critical flashover voltage Vcri of polluted insulator under lightning impulse voltage. It is shown that the experimental values of Vcri depends on the configuration of pollution and the polarity of voltage. A mathematical model enabling to compute the flashover discharge characteristic constants (n and N) and the critical thickness of pollution layer and thence the critical flashover voltage is presented. It's also shown that n and N are not static and they depend on the parameters of the equivalent electrical circuit, thermal characteristics of discharge and the condition of propagation. The computed critical voltages are found in a good accordance with the experimental ones. View full abstract»

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    Experience with Preventing External Flashovers in HVDC Converter Stations

    McDermid, W. ; Black, T.
    Electrical Insulation, 2008. ISEI 2008. Conference Record of the 2008 IEEE International Symposium on

    DOI: 10.1109/ELINSL.2008.4570283
    Publication Year: 2008 , Page(s): 81 - 84
    Cited by:  Papers (3)

    IEEE Conference Publications

    Wall bushings, apparatus bushings, transductors (DCCTs) and post insulators are vulnerable to flashover in HVDC converter stations under conditions of non-uniform (N-U) wetting, fog, etc. Experience is reported over a 30 year period in preventing external insulation flashovers through the use of booster sheds or RTV coatings. View full abstract»

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    Flashover characteristics of flat model under DC voltage in wind-sand two-phase mixture

    SiMa Wen-xia ; Ma Gao-quan ; Yang Qing
    High Voltage Engineering and Application, 2008. ICHVE 2008. International Conference on

    DOI: 10.1109/ICHVE.2008.4773898
    Publication Year: 2008 , Page(s): 158 - 162

    IEEE Conference Publications

    The influence of sand dust on discharge of outdoor insulation has caused widespread concern. At present, the research results show wind-sand electricity has have a remarkable effect on the discharge characteristics of insulator and has little influence on the discharge characteristics of air gap. The flashover of insulator strings is discharge along the insulator surface and air gaps, and the sand dust deposited on the insulator surface may affect the flashover characteristics of insulator strings. This paper studies flashover characteristics of flat model under DC voltage in wind-sand two-phase mixture. The experimental results show that under positive polarity voltage the flashover voltage of flat model has a maximum value while under negative polarity voltage the flashover voltage has a minimum value with a certain degree of sand dust deposition. The wind or sand under sand-dust weather has an important effect on the discharge characteristics of flat model. In certain variation range of electric charge, electric charge of sand dust has little effect on the flashover voltage of flat model under direct voltage. The deposition of sand has significant influence on the flashover process of flat model, and the extent is related to the deposition density and moisture content of sand particle. The moistened sand can be considered as a special kind of contamination. View full abstract»

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    Research on Electric Field Strength Distortion near the Insulators When There Is Any Guano-Caused Flashover of Insulators of Power Transmission Lines

    Zheng Jingwen ; Li Yuchao
    Power and Energy Engineering Conference (APPEEC), 2012 Asia-Pacific

    DOI: 10.1109/APPEEC.2012.6307744
    Publication Year: 2012 , Page(s): 1 - 4

    IEEE Conference Publications

    Along with the rapid development and continuous deepening of the market economy system, the whole society's demands for safe and high-quality services of power system have been becoming higher and higher. However, the flashover of insulators of power transmission lines caused by guano frequently threatens the safe and reliable operation of the power transmission lines, which can cause tremendous economic losses to the power industry. This paper describes the occurrence mechanisms for flashover faults of insulators of power transmission lines, and carries out simple simulation and modeling research to summarize the preliminary data drawn from the research, meanwhile, the theoretical results have been obtained by virtue of some relevant materials, which has provided theoretical bases and methods for reducing and or even preventing the guano-caused flashover faults of insulators of power transmission lines, therefore, it is of great significance in protecting the safe and stable operation of power grid and reducing the losses caused by the guano-caused flashover faults of insulators of power transmission lines. View full abstract»

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    Investigation of Surface Flashover on Dielectrics Enhanced by Excimer Laser Processing

    Sarjeant, W.J. ; Zirnheld, J. ; Berkow, J. ; Strzempka, P. ; Cieri, J.
    Power Modulator Symposium, 2006. Conference Record of the 2006 Twenty-Seventh International

    DOI: 10.1109/MODSYM.2006.365186
    Publication Year: 2006 , Page(s): 81 - 85
    Cited by:  Papers (2)

    IEEE Conference Publications

    One of the factors that contributes to surface flashover on dielectrics is the existence of defects on the surface of the material. For our studies, excimer laser processing was utilized on alumina dielectrics in an attempt to substantially increase the threshold voltages for flashover. Through excimer laser processing, the surface material melts and re-crystallizes to form a uniform surface structure. The defects on the dielectric surface can be minimized, reducing charge trapping, leading to higher flashover voltages. Two sets of samples were tested. The first set of samples was processed using the laser and the second set was not. The samples were then stressed under high voltage to induce surface flashover. Analysis of the effects of the excimer laser processing was performed and are shown View full abstract»

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    Partial vacuum flashover of aerial lift documentation and failure analysis

    Booker, James R.
    Electrical Insulation, 2004. Conference Record of the 2004 IEEE International Symposium on

    DOI: 10.1109/ELINSL.2004.1380580
    Publication Year: 2004 , Page(s): 328 - 330

    IEEE Conference Publications

    Full understanding of different failure modes of extra high voltage (EHV) aerial lifts has been obtained in over 30 years of testing. Finding problems by flashover helped speed up the learning curve. One failure mode, the vacuum flashover is especially troublesome because of the lack of understanding of the problem. In 1983, a vacuum flashover occurred during a certification attempt on two different occasions. ANSI A92.2 states that vacuum flashover will be prevented by use of vacuum breakers. The actual preflashover conditions will be described and explained. Photographs and sketches will document the action that 15 witnesses saw during the certification test on an 800 kV class aerial lift. The actual vacuum flashover occurred during a daylight test at 467 kV starting a fire inside the insulating section. The test underway was a 600 kV 3 minute hold per ANSI A92.2. This fire burned itself out of oxygen, because of the sealed boom, and was not discovered until a retest was about to take place. A photograph was taken through the silica gel canister hole confirming the fire, which melted the all the hydraulic hoses. A full investigation proved the existence of the vacuum flashover and the pre-flashover photos and arcing condition added documentation to the vacuum flashover theory. The analysis places all the functions of this problem in proper order. The lack of understanding of this basic problem has caused fatalities and at least 11 or 12 vacuum flashovers of EHV aerial lifts in the world to date. View full abstract»

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    Effect of annealing and polishing on flashover characteristics of ceramic in vacuum

    Shioiri, T. ; Shindo, T. ; Kamikawaji, T. ; Kaneko, E. ; Ohshima, I.
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 9 , Issue: 3
    DOI: 10.1109/TDEI.2002.1007705
    Publication Year: 2002 , Page(s): 416 - 420
    Cited by:  Papers (6)

    IEEE Journals & Magazines

    Experiments were carried out to study the effects of surface polishing and annealing of ceramic specimens on the dielectric breakdown characteristics of their surfaces. It was found that when the samples were annealed at 1000°C, allowing the residual stresses in their surfaces to decrease, the breakdown voltage rose, whereas with the polished samples, reductions of residual stresses resulted in a slight rise of the breakdown voltage. Prior to dielectric breakdown, a surface glow was observed, due to luminescence from electron bombardment and insulator surface defects. The starting voltage of luminescence rose when residual stresses were reduced. It is suggested that the mechanical strain due to surface defects contributes to dielectric breakdowns on ceramic surfaces View full abstract»

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    The influence of a DC electric field on high power microwave window flashover in air and N2 environments

    Foster, J. ; Thomas, M. ; Krompholz, H. ; Neuber, A.
    Pulsed Power Conference, 2009. PPC '09. IEEE

    DOI: 10.1109/PPC.2009.5386323
    Publication Year: 2009 , Page(s): 480 - 483

    IEEE Conference Publications

    Observed delay times for high power microwave surface flashover are influenced significantly by the presence of a DC electric field. The experimental setup to investigate theses influences is comprised of an S-band magnetron operating at 2.85 GHz with a pulse rise time shortening switch assembly that produces a 50 ns rise time at a ~ 2.5 MW power level. A wire electrode charged to ±20 kV is inserted into the dielectric interface perpendicular to the electric field of the TE10 mode to provide a DC electric field in the flashover region. Tests have been conducted in pure N2 at 125 torr in order to provide an environment composed of primarily electrons and positive ions. The average measured delay of window flashover with a DC field pointing into the dielectric has been observed to increase by ~50%. Additionally, effective emission rates of seed electrons initiating breakdown have shown a decrease from 14 e/¿s to 2 e/¿s, indicating the removal of charged species from the high microwave field region due to charge drift in the applied DC field. An overview of the experimental setup is given along with a statistical analysis of delay times measured in Air as well as N2. The open question of where seed electrons originate from and the quantification of the primary processes involved will be addressed. View full abstract»

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    Surface flashover characteristic of disc-type spacer system initiated by wedge shaped gas gap and its improvement

    Hama, H. ; Yamamoto, H. ; Sakuma, S. ; Takatsuka, K. ; Yamauchi, T.
    Power Delivery, IEEE Transactions on

    Volume: 8 , Issue: 3
    DOI: 10.1109/61.252633
    Publication Year: 1993 , Page(s): 1070 - 1079
    Cited by:  Papers (3)

    IEEE Journals & Magazines

    The surface flashover characteristics initiated by local field intensification are investigated for lightning impulse, switching impulse, and AC voltages, using disc-type model spacer systems with a wedge-shaped gas gap formed between the spacer flange and the earthed sheath end. The surface flashover voltages of the systems are evaluated by simple theory in SF/sub 6/ gas and compared with experimental results. Thin dielectric coating of a low-permittivity material on the sheath ends and the shielding of sheath ends which protrude inwardly are effective in improving the dielectric performance of the system.<> View full abstract»

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    Numerical electromagnetic field analysis of archorn voltages during a back-flashover on a 500-kV twin-circuit line

    Mozumi, T. ; Baba, Y. ; Ishii, M. ; Nagaoka, N. ; Ametani, A.
    Power Delivery, IEEE Transactions on

    Volume: 18 , Issue: 1
    DOI: 10.1109/TPWRD.2002.803828
    Publication Year: 2003 , Page(s): 207 - 213
    Cited by:  Papers (12)

    IEEE Journals & Magazines

    Archorn voltages of a simulated 500-kV twin-circuit line, in the case of one-phase back-flashover due to lightning to a tower top, are analyzed by the thin-wire time-domain analysis (TWTDA) code. Prior to this analysis, a recently proposed flashover model is incorporated into TWTDA. It becomes clear that the archorn voltages of the other two phases show a quite similar time-varying characteristic after one-phase back-flashover. An EMTP simulation is also carried out. The archorn voltages computed by the electromagnetic transients program (EMTP) agree well with those computed by TWTDA before the back-flashover on one phase. On the other hand, during about 1 μs after the one-phase back-flashover, the archorn voltages of the other two phases computed by EMTP deviate much from those computed by TWTDA. Particularly in the case of the middle- or the lower-phase back-flashover, the deviation is noticeable. The reason for this discrepancy is discussed. View full abstract»

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    Insulator-surface flashover conditioning: A streak photographic investigation

    Asokan, T. ; Sudarshan, T.
    Plasma Science, IEEE Transactions on

    Volume: 21 , Issue: 3
    DOI: 10.1109/27.277555
    Publication Year: 1993 , Page(s): 298 - 304
    Cited by:  Papers (5)

    IEEE Journals & Magazines

    Conditioning behavior of surface flashover strength of a large-bandgap insulator (quartz) is investigated with the aid of streak photography in conjunction with electrical (voltage and current) and optical UV (phototube) diagnostics. The breakdown strength of the sample is found to be conditioned during the initial test as well as the subsequent test, performed after an overnight rest period. The results suggest that light emission during the initial test is dominated by visible light whereas during the subsequent test it is dominated by UV. The initial conditioning is attributed primarily to the desorption of absorbed molecules and rearrangement of the same by migration kinetics. Processes such as negative charge formation on the insulator surface and trapping of electrons in the deep traps are proposed to be responsible for the observed conditioning after the overnight rest period. The breakdown strength of the sample was found to degrade after experiencing breakdown at higher fields (i.e., after second day test). This deconditioning behavior is discussed in terms of evaporation of electrode material and deposition of the same on the insulator near the cathode end View full abstract»

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    Analytical computation of discharge characteristic constants and critical parameters of flashover of polluted insulators

    El-A Slama, M. ; Beroual, A. ; Hadi, H.
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 17 , Issue: 6
    DOI: 10.1109/TDEI.2010.5658227
    Publication Year: 2010 , Page(s): 1764 - 1771
    Cited by:  Papers (13)

    IEEE Journals & Magazines

    This paper presents mathematical expressions of dc and ac flashover discharge characteristic constants (n and N) of polluted insulators. It's shown that the proposed relationships of n and N are not static and they depend on the parameters of the equivalent electrical circuit and thermal characteristics of discharge. The critical voltages and currents computed using the dynamic equations of n and N we established are found in a good accordance with the experimental ones. Under dc, the temperature of the discharge channel is higher with a positive point than with a negative point. And under ac, the discharge temperature range is almost identical to that one corresponding to the dc positive polarity case. View full abstract»

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    A unique experimental validation in atmospheric flashover phenomena

    Buneo, J.D. ; Tursi, J.P. ; Reid, B.H. ; Couchman, P.E. ; Zirnheld, J.L. ; Burke, K.M. ; Sarjeant, W.J.
    Electrical Insulation, 2002. Conference Record of the 2002 IEEE International Symposium on

    DOI: 10.1109/ELINSL.2002.995923
    Publication Year: 2002 , Page(s): 245 - 247
    Cited by:  Papers (2)

    IEEE Conference Publications

    Lack of flashover robustness has been shown to catastrophically damage energy systems. A greater general understanding is needed to be able to design modern energy systems around this unique failure process. A flashover is a disruptive discharge through air around or over the surface of insulation produced by the application of voltage wherein the breakdown path becomes sufficiently ionized to maintain an electric arc. Flashover in insulators has in the past been shown to occur at the interface between insulator, conductor and air (or some other insulating medium) and is known as the triple point. The focus of this study is on the adverse effects of flashover on thin polyester and polypropylene films cut to initial lengths and widths of 12" × 3/4" respectively. The thickness for the polypropylene film is 7 microns while the polyester is 4.5 microns. The bulk resistance for the polypropylene film is 7Ω/square inch and for polyester is 3Ω/square inch. Flashover on the samples was initiated by the application of 2400 Vac. Preliminary results have shown that the thin polyester film is resistant to flashover formation and sublimates upon the application of the test voltage. However, the polypropylene was able to sustain the flashover without sublimating. Upon further investigation, the polypropylene would sustain flashover when scaled down linearly in voltage and length to a minimum of 150 Vac and 3/4" length. Little is known of flashover basics, and this fundamental work, for the very first time, both experimentally validates and theoretically explains the behavior for a phenomenon of grave robustness concern for energy systems. View full abstract»

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    Surface Flashover of Water Repellant Insulators under Moist Conditions

    Cheng, T.C. ; Jolly, D.C. ; King, D.J.
    Electrical Insulation, IEEE Transactions on

    Volume: EI-12 , Issue: 3
    DOI: 10.1109/TEI.1977.298021
    Publication Year: 1977 , Page(s): 208 - 213
    Cited by:  Papers (8)

    IEEE Journals & Magazines

    A study was conducted to determine how surface moisture can lower the flashover strength of insulation, with particular reference to out-door high voltage insulation. Since water repellant greases are used to prevent flashover under moist, contaminated conditions, and since new insulator materials will have improved water repellancy, the study concentrated on surface wetting effects. Studies were made of droplet growth during fog for several surfaces. Flashover studies showed that near threshold, flashover occurred by means of droplet deformation in the electric field. Rough agreement was obtained with a simple theory. The study provided further support for the development of hydrophobic coatings for outdoor insulation. View full abstract»

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    VUV emission from dielectric surface flashover at atmospheric pressure

    Rogers, G. ; Neuber, A. ; Laity, G. ; Dickens, J. ; Frank, K. ; Schramm, T.
    Pulsed Power Conference, 2009. PPC '09. IEEE

    DOI: 10.1109/PPC.2009.5386373
    Publication Year: 2009 , Page(s): 855 - 859
    Cited by:  Papers (1)

    IEEE Conference Publications

    Spectroscopic measurements in the vacuum ultraviolet (VUV) regime are difficult to make due to extremely large absorption of VUV radiation in most materials. This paper describes an experimental setup designed for studying the optical emission during pulsed surface flashover for the wavelength range between 115 nm to 180 nm at atmospheric pressures with a focus on the scheme used to excite the spark gap. The surface flashover of interest occurred on an MgF2 window (front side of window in air, backside in vacuum) imaged onto the entrance slit of a 1 m vacuum spectrograph. Emission spectra were recorded with an Andor DH740 series ICCD camera. All data was taken at atmospheric pressure with a flashover spark length of about 8 mm created by a pulser designed for a 500 ns pulse, max 50 kV output. The centerpiece of this pulser is the CCSTA14N40 thyristor by Solidtron/Silicon Power which features a rate of change current of maximum 30 kA/¿s and a hold-off voltage of up to 4 kV. A pulse transformer with Metglas® core was used to elevate the voltage to 50 kV with a rise time of 180 ns and a peak current of 500 A. The pulser was designed for a repetition rate of 10 Hz and is triggered by TTL pulses. Discussed in this paper, along with the measured spectra and their relation to the physics of surface flashover at atmospheric pressure, will be the design of the pulser. View full abstract»

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    Critical flashover voltage of short HV insulator covered with ice at low atmospheric pressure

    Li, Y. ; Farzaneh, M. ; Zhang, J.
    Power System Technology, 1998. Proceedings. POWERCON '98. 1998 International Conference on

    Volume: 1
    DOI: 10.1109/ICPST.1998.729018
    Publication Year: 1998 , Page(s): 520 - 523 vol.1
    Cited by:  Papers (3)

    IEEE Conference Publications

    The main purpose of the present paper is to investigate the effects of high altitude on AC flashover of a short insulator covered with ice. The experiments were carried out in an evacuated chamber in which the air pressure condition at high altitude up to 9000 m may be simulated. It was found that low pressure at high altitudes could reduce the minimum flashover voltage of the short insulator covered with ice. The results also showed that the effects of low air pressure on the minimum flashover voltage of ice-covered insulators depend on insulator profile View full abstract»

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    Dynamic arc model of the flashover of the polluted insulators

    Bessedik, S.A. ; Hadi, H.
    Electrical Insulation and Dielectric Phenomena (CEIDP), 2011 Annual Report Conference on

    DOI: 10.1109/CEIDP.2011.6232716
    Publication Year: 2011 , Page(s): 550 - 554
    Cited by:  Papers (2)

    IEEE Conference Publications

    The importance of the research on insulator pollution has been increased considerably with the rise of the voltage of transmission lines. In order to determine the flashover behavior of polluted high voltage insulators and to identify to physical mechanisms that govern this phenomenon, the researchers have been brought to establish a modeling. In this study after presenting the theoretical and experimental open model, a dynamic arc model has been developed to calculate the flashover. The validity of the model was verified by comparing the computed results with the experimental results of previous researchers and good correlation has been shown. View full abstract»

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    Effect of different coning angles on flashover characteristics across machinable ceramic in vacuum

    Xue-Zeng Huang ; Jiang-Yang Zhan ; Nan Zheng ; Hai-bao Mu ; Guan-Jun Zhang
    Electrical Insulating Materials (ISEIM), Proceedings of 2011 International Conference on

    DOI: 10.1109/ISEIM.2011.6826293
    Publication Year: 2011 , Page(s): 305 - 308

    IEEE Conference Publications

    Surface flashover in vacuum is a kind of complicated surface and interface phenomena, which seriously restricts the development of high voltage electro-vacuum devices. Introducing a kind of machinable ceramic with excellent machinable performance and good surface electrical capability into vacuum insulation system, and considering the commonly used truncated cone structure, machinable ceramic samples with different coning angles are machined. Their surface flashover voltage are investigated under pulsed voltage in vacuum, and the electric field distributions and surface charge density of different coning angles are numerically simulated. The experimental results indicate that, the flashover voltage of cone insulators is higher than that of cylindrical insulators, the flashover voltage of truncated cone samples with positive coning angle is much higher than that of with negative coning angles, and the flashover voltage with ~45° conical frustum is highest. It is considered that, the coning angle plays an important role on the electric field of cathode triple junction (CTJ) and surface charge distribution. When the coning angle is positive, the electric field of CTJ and surface charge distribution is smaller, and when the coning angle is negative, these values are bigger, so its higher CTJ electric field and surface charge result in a lower flashover voltage than that with positive angle, and also the short free path of electrons and decreased energy of electrons colliding with insulator surface lead to a higher flashover voltage than that of cylindrical insulators. View full abstract»

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    Study on Pollution Flashover Characteristics of ±800kV DC Composite Insulators

    Luo Bing ; Li Licheng ; Rao Hong ; Li Xiaolin
    Power Engineering Society Conference and Exposition in Africa, 2007. PowerAfrica '07. IEEE

    DOI: 10.1109/PESAFR.2007.4498056
    Publication Year: 2007 , Page(s): 1 - 5
    Cited by:  Papers (5)

    IEEE Conference Publications

    This paper presents the basic structure parameters of 800kV DC composite insulator specimen and the pollution test scheme. The condition of 800kV DC composite insulator pollution test under whole 800kV voltage and whole structure dimension completed in STRI, which is completed first time in the world, is introduced. The study results indicate that the linear relation between the pollution flashover voltage and the length of 800kVDC composite insulator is high-blooded. The consistency of test data between STRI and China lab is good. The pollution flashover characteristics of I string and V string under whole voltage and whole structure dimension is confirmed. The formula of DC pollution flashover grads calculated by SDD of DC composite insulator is obtained. View full abstract»

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    Flashover characteristics and surface processes under negative impulse voltage in atmospheric air

    Shimazaki, T.
    Electrical Insulation, IEEE Transactions on

    Volume: 27 , Issue: 3
    DOI: 10.1109/14.142711
    Publication Year: 1992 , Page(s): 488 - 495
    Cited by:  Papers (5)

    IEEE Journals & Magazines

    Breakdown phenomena on surfaces of acrylic plates, 1 to 10 mm thick, were investigated under negative impulse voltage in atmospheric air. The 50% flashover voltage V50 and the 50% corona inception voltage were measured, and the discharge phenomena were observed with an image converter camera, in the creeping distance d =0.4 to 10 cm. The V50 vs. d characteristics are classified into two regions, C' and A. The creeping distance in the C' region is d=0.4-dc cm and in the A region d=dc-10 cm, where the boundary distance dc depends on the thickness of the acrylic plate τ. In the C' region the V50 increases at the rate of ~18.4 kV/cm independently of τ, and the positive leader leads to flashover as in air gaps, while in the A region the V50 increases at the rate of 1 to 4 kV/cm and the negative leader plays an important part in the flashover. These flashover processes are illustrated with typical photographs, the conceptual figures constructed on the basis of photographic observations, and flashover characteristics are explained View full abstract»

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    The early phase of dielectric surface flashover

    Hegeler, F. ; Masten, G. ; Krompholz, H. ; Hatfield, L.L.
    Electrical Insulation and Dielectric Phenomena, 1992. Annual Report. Conference on

    DOI: 10.1109/CEIDP.1992.283209
    Publication Year: 1992 , Page(s): 463 - 468
    Cited by:  Papers (3)

    IEEE Conference Publications

    Results of high-temporal-resolution current, luminosity, and X-ray measurements indicate the existence of free electrons during the first phase of dielectric surface flashover. The linearly rising current points to a saturation mechanism of the carrier amplification during this phase. In a subsequent phase, the exponentially rising current, the termination of the X-ray emission, and the build-up of plasma above the surface indicate gaseous ionization processes. The observations are compatible with the standard model for dielectric surface flashover-the saturated secondary electron emission avalanche and electron induced gas desorption View full abstract»

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    AC flashover performance and voltage of long polluted and iced XP-70 suspension insulator string

    Xingliang Jiang ; Caixin Sun ; Lichun Shu ; Wenxia Sima
    Properties and Applications of Dielectric Materials, 2003. Proceedings of the 7th International Conference on

    Volume: 1
    DOI: 10.1109/ICPADM.2003.1218377
    Publication Year: 2003 , Page(s): 158 - 161 vol.1

    IEEE Conference Publications

    Based on a series of systematic laboratory investigation carried out on the flashover of strings of three to twenty-one suspension insulator units ice-covered with polluted spraying water aimed at obtaining the AC flashover performance and voltage, this paper discusses the flashover performance and voltage of long iced XP-70 insulator string. According to the analysis of tested results, it puts forward that the product σ0 of the icing water conductivity γ20 converted to the value of 20°C and the average ice amount w accreted on each insulator unit could be used as a characteristic parameter to show the effect of the ice and the contaminated icing water as well as the pre-contamination of the insulator on the minimum flashover voltage, and that the minimum flashover voltage of an iced insulator string in the severe ice-covered state can be expressed as a power function of σ0 by a index of -0.32. And it indicates that the minimum flashover voltage of an ice-covered XP-70 insulator string is direct proportional to the units or length of an insulator string. View full abstract»

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    Discussion on ¿Copper drag on commutators¿, ¿Flashover on d.c. machines¿ and ¿Commutation phenomena in electrical machines. Part 2: Further experiments in flashover¿


    Electrical Engineers, Proceedings of the Institution of

    Volume: 116 , Issue: 11
    DOI: 10.1049/piee.1969.0350
    Publication Year: 1969 , Page(s): 1914 - 1919

    IET Journals & Magazines

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    Experimental study on the pollution flashover mechanism of polymer insulators

    Wang Shaowu ; Liang Xidong ; Huang Lengceng
    Power Engineering Society Winter Meeting, 2000. IEEE

    Volume: 4
    DOI: 10.1109/PESW.2000.847332
    Publication Year: 2000 , Page(s): 2830 - 2833 vol.4
    Cited by:  Papers (2)

    IEEE Conference Publications

    For an extensive understanding of the pollution flashover mechanism on hydrophobic surfaces, a series of experiments were designed to investigate the relationship between hydrophobicity, pollution severity and pollution withstand property of polymer insulators. Rain tests with the conductivity 100 μS/cm to 100000 μS/cm were conducted on the silicone rubber insulators presenting various hydrophobicity statuses. It is found that the electric conductivity and accumulating status of water droplets or zones on the hydrophobic surface is tied closely to the sequence flashover voltage, even in the case of complete hydrophobicity. The accumulating status and the conductivity of water droplets on the contaminated polymer insulators depend both on the hydrophobicity and on the pollution severity. It suggests that the pollution flashover voltage on the hydrophobic surface relates not only to the hydrophobicity but also to the pollution severity. Based on the results, pollution flashover mechanism on the hydrophobic surface is discussed View full abstract»

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    Effect of altitude on electric breakdown and flashover of aircraft insulation

    Berberich, L. J. ; Moses, G. L. ; Stiles, A. M. ; Veinott, C. G.
    Electrical Engineering

    Volume: 63 , Issue: 6 , Part: Supplement
    DOI: 10.1109/EE.1944.6440310
    Publication Year: 1944 , Page(s): 345 - 353

    IEEE Journals & Magazines

    ELECTRIC power to operate auxiliaries is now an indispensable requirement of modern aircraft. Within the past ten years the electric load on an airplane has increased more than tenfold.1 The optimum voltage for electric systems for large aircraft already has more than exceeded the present 24-volt standard,2,3 and the use of higher-voltage systems, already tried experimentally,4 now appears to be a certainty. Moreover, the operating altitudes of modern airplanes, particularly military craft, are climbing steadily to ever increasing heights. Each of these factors indicates a need for a careful study of the requirements for insulation of aircraft electric apparatus in order to achieve minimum weight and space without sacrifice of reliability. A preliminary study of this subject was made and reported5 prior to the use of the 120-volt a-c system on the XB-19, but the projected use of 208-volt systems4 for still higher altitudes makes a more comprehensive study of this problem most timely. View full abstract»

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    General criterion for the prediction of pollution flashover

    Hesketh, S.
    Electrical Engineers, Proceedings of the Institution of

    Volume: 114 , Issue: 4
    DOI: 10.1049/piee.1967.0106
    Publication Year: 1967 , Page(s): 531 - 532
    Cited by:  Papers (14)

    IET Journals & Magazines

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    Exploration of self-produced vacuum ultraviolet radiation from dielectric surface flashover at atmospheric pressure

    Laity, G. ; Fierro, A. ; Hatfield, L. ; Neuber, A.
    Electrical Insulation and Dielectric Phenomena (CEIDP), 2011 Annual Report Conference on

    DOI: 10.1109/CEIDP.2011.6232719
    Publication Year: 2011 , Page(s): 563 - 566
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper describes recent experiments to study self-produced vacuum ultraviolet (VUV) emission from pulsed atmospheric plasma structures. While it has been classically believed that photo-ionization plays a significant role on plasma generation during fast timescales (i.e. streamers), the exact role of VUV radiation (energy greater than 7 eV) has only recently been explored and is currently an area of interest for the development of high power devices in the aerospace community. Since VUV emission is heavily absorbed by molecular oxygen and most optical materials, the direct observation of VUV radiation produced by atmospheric pressure plasmas is challenging. Experiments at Texas Tech University were performed with multiple vacuum monochromators, custom designed VUV transparent optical instruments, VUV sensitive intensified CCD and photomultiplier time-resolved diagnostics, and nanosecond-timescale electrical probes of the plasma. Previous studies were limited due to the non-linearity of the focusing optics used for VUV transmission, and thus the current experiment was designed to minimize chromatic abberation of recorded emission in the VUV regime of interest (115-135 nm). Quantitative observation of VUV emission from surface flashover in air revealed that the majority of emission is due to radiation from atomic oxygen and nitrogen in the wavelength range 130-135 nm, which has been confirmed by spectral calculation for an estimated Boltzmann temperature of 10 eV. High resolution spectral measurements in the range 115-130 nm also led to observation of various impurities along the surface, which were only observable due to the upgraded focusing system. Finally, time resolved measurements showed that the earliest VUV emission occurs during the streamer phase, where the recorded signal-to-noise ratio of the observed emission has been significantly increased due to more efficient optical diagnostics. View full abstract»

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    Study of Polluted Insulator Flashover Forecasting Based on Nonlinear Time Series Analysis

    Xu Jianyuan ; Teng Yun ; Lin Xin
    High Voltage Engineering and Application, 2008. ICHVE 2008. International Conference on

    DOI: 10.1109/ICHVE.2008.4773895
    Publication Year: 2008 , Page(s): 148 - 151
    Cited by:  Papers (1)

    IEEE Conference Publications

    To solve the problem of the flashover forecasting of contaminated or polluted insulator, a flashover forecasting model of contaminated insulators based on nonlinear time series analysis is proposed in the paper. The equivalent salt deposit density (ESDD) is the key of flashover on polluted insulator. The ESDD value of insulator can be forecasted by the method of nonlinear time series analysis of the ESDD time series and a forecasting model of polluted insulator flashover is proposed in the paper. The forecasting model consists of two artificial neural networks that reflect relationship of environment, ESDD and flashover probability. The first is used to estimate the ESDD time series of insulator and the second is employed to calculate the probability of the flashover. A series of artificial pollution tests show that the results of the forecasting model is acceptable. View full abstract»

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    Impulse flashover of particle-contaminated spacers in compressed sulphur hexafluoride

    Hampton, B.F. ; Fleming, S.P.
    Electrical Engineers, Proceedings of the Institution of

    Volume: 120 , Issue: 4
    DOI: 10.1049/piee.1973.0107
    Publication Year: 1973 , Page(s): 514 - 518
    Cited by:  Papers (6)

    IET Journals & Magazines

    The impulse flashover stresses of coaxial-disc spacers, both clean and when contaminated with conducting particles, have been measured for pressures of the ambient SF6 gas between 0.47 and 1.5 MN/m2. Clean spacers had a higher flashover stress on positive than on negative polarity, but, for contaminated spacers, the positive stress was reduced much more than the negative stress. The effect of particles increased with their size over the 35¿210 ¿m range used in these experiments, and was greater at the higher gas pressures. Insulating particles of similar sizes had little effect. Experimental results followed a Gaussian distribution, and could be extrapolated to give stresses at which the flashover probability was very low. View full abstract»

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    Anomalous creeping flashover characteristics in N2/SF 6 mixtures and effect of barrier surface

    Ueno, H. ; Kamatani, F. ; Egawa, Y. ; Nakayama, H.
    Electrical Insulating Materials, 2001. (ISEIM 2001). Proceedings of 2001 International Symposium on

    DOI: 10.1109/ISEIM.2001.973679
    Publication Year: 2001 , Page(s): 379 - 382

    IEEE Conference Publications

    Creeping flashover characteristics have been investigated for an N 2/SF6 composite insulating system consisting of insertion of an insulating barrier between the needle electrode and the plane electrode. The negative flashover voltage (FOV) for the flat and stepped systems in N2 (D=0%) is as high as that of SF6 (D=0%) by the effective field relaxation from the accumulated charges. Remarkable reduction of FOV induced by few percentages SF6 addition should originate from the barrier interaction such as ineffective charge accumulation and photon-related emission. However, for the grooved system, the confinement effect should be effective, resulting in lower FOV in N2 View full abstract»

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    Experimental investigation of surface flashover characteristics in vacuum

    Dai, Ling ; Lin, Fuchang ; Shi, Xiangyu ; Yao, Xingchen ; Cheng, Yaohong ; Li, Zhiwei ; Su, Cheng
    Power Modulator and High Voltage Conference (IPMHVC), 2012 IEEE International

    DOI: 10.1109/IPMHVC.2012.6518770
    Publication Year: 2012 , Page(s): 422 - 426
    Cited by:  Papers (1)

    IEEE Conference Publications

    This paper devotes itself to the experimental study on surface flashover characteristics of insulating material, which is closely connected to the compact pulsed power system operating in vacuum. The rated voltage of the pulsed power source is several kV and the peak current is several kA. To simulate the actual operating condition and possible failure mode of pulsed power system, a series of experiments are performed to validate the adaptability of high pulsed power device in vacuum. This paper concentrates on the mechanism of surface flashover in vacuum and corresponding influence factors. Different metal electrode materials, different creepage distances and the interference effect of hot plasma have been studied. Research indicates that external plasma plays a key role in the formation of surface flashover. In medium vacuum (1×10−3 Pa), the surface flashover voltage of 3mm surface creeping distance on organic glass is above 17 kV; But if there is external plasma source, the flashover voltage would reduce significantly with the increase of plasma density; flashover voltage would rush to 1 kV or lower. Based on the experiment study, some measures are taken on the several kilovolts pulsed power source (PPS) produced in prior work. The device can operate stably in the vacuum of 10−3 Pa. View full abstract»

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    Surface modification of polymethyl-methacrylate using atmospheric pressure argon plasma jets to improve surface flashover performance in vacuum

    Tao Shao ; Yixiao Zhou ; Cheng Zhang ; Wenjin Yang ; Zheng Niu ; Chengyan Ren
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 22 , Issue: 3
    DOI: 10.1109/TDEI.2015.7116373
    Publication Year: 2015 , Page(s): 1747 - 1754

    IEEE Journals & Magazines

    Hydrophilic modification of polymethyl methacrylate (PMMA) surface is performed by atmospheric pressure plasma jet (APPJ) in Ar gas for improving the PMMA surface flashover performance in vacuum. In the experiments, APPJ is driven by a microsecond-duration pulsed generator, which has voltages of 0-30 kV, a rise time of 300 ns and a full width at half maximum of 2μs. Characteristics of the APPJ are analyzed according to its voltage and current waveform, discharge image and optical emission spectrum. Furthermore, surface properties of the PMMA surface before and after the treatment are characterized by water contact angle measurements and morphology observations. Results show that the main species of the plasma jet are composed of N2, Ar, OH, and O, among which such polar groups as OH and O enhance the hydrophilic property of the PMMA surface. The water contact angle decreases from 68° to a minimum value (16°) after the treatment. In addition, all the surface flashover voltages in vacuum for the PMMA samples treated by APPJ are higher than those for the untreated PMMA samples. View full abstract»

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    AC flashover performance for line post and pin post insulators in distribution 22 kV

    Thipprasert, W. ; Sritakeaw, P. ; Jirapong, P.
    Vehicle Power and Propulsion Conference (VPPC), 2012 IEEE

    DOI: 10.1109/VPPC.2012.6422794
    Publication Year: 2012 , Page(s): 464 - 468

    IEEE Conference Publications

    Electrical insulators in 22kV distribution system of the Provincial Electricity Authority (PEA) are mostly porcelain insulator types that consists of suspension, pin type, line post, and pin post insulators. The distribution lines will be polluted by industrial contaminants, salt fog or natural dust. Experience shows that pollution flashover is one of the main natural calamities harming and affecting the voltage stability and reliability of distribution system. This paper compares the test results obtained from artificial pollution tests according to IEC 60507 with line post type and pin post type insulators of medium system under same test conditions. The salt fog test results indicate that the pollution flashover performance of line post insulator is less than to 50 percent of wet power frequency withstand voltage at equivalent salt deposit density (ESDD) = 0.5 mg/cm2 and the leakage current (LC) of line post insulator increased to 10.2 mA at ESDD = 0.5 mg/cm2 at nominal voltage. In the experiment indicate that AC pollution flashover performance of pin post insulator has better than line post insulator in the serious pollution area. View full abstract»

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    Pollution flashover performance of full-scale ±800 kV converter station post insulators at high altitude area

    Chuyan Zhang ; Liming Wang ; Zhicheng Guan ; Fuzeng Zhang
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 20 , Issue: 3
    DOI: 10.1109/TDEI.2013.6518940
    Publication Year: 2013 , Page(s): 717 - 726
    Cited by:  Papers (4)

    IEEE Journals & Magazines

    On the background of the peculiar technology problems with the external insulation of UHV dc equipment in China, caused by high altitude and heavy pollution, this paper presents the pollution flashover performance of full-scale ±800 kV converter station post insulators at actual high altitude area. The tests were carried out according to the solid layer method, and the 50% withstand voltage (U50%) was determined by the up-and-down method. The artificial contamination test results indicated that the shed configuration and the rod diameter had a significant influence on the flashover voltages. Shed parameters of one big and one small alternating shed composite post insulator which had superior dc pollution flashover performance had been recommended. The relationship between U50% and insulation height was approximately linear at actual high altitude area for post insulators. It was found that partial discharges occurred at the top section firstly and partial arcs easily appeared at the parts nearby the connecting fittings during the flashover process. And arc floating phenomenon was significantly serious in actual high altitude area. Furthermore, comparison was made between the U50% values of composite post insulators in fog and in rain. The U50% values in fog of composite post insulators were generally higher than that in rain. Thus, the outdoor insulation design of composite post insulators should primarily consider the U50% value in fog. This work thus provides useful reference for the design, operation and maintenance of UHV dc converter stations outdoor insulators in China. View full abstract»

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    Surface and interface physical phenomena induced by flashover across solid dielectrics in vacuum

    Guan-Jun Zhang ; Nan Zheng ; Kai-kun Yu ; Xi-Wei Hao
    Discharges and Electrical Insulation in Vacuum, 2008. ISDEIV 2008. 23rd International Symposium on

    Volume: 2
    DOI: 10.1109/DEIV.2008.4676830
    Publication Year: 2008 , Page(s): 463 - 468

    IEEE Conference Publications

    Essentially surface flashover across a solid in vacuum is considered as a kind of complicated surface and interface physical phenomena. Based on the concurrent electrical and optical measurements and microscopic observations, the research works of our group concentrate on the relationship between flashover and surface/interface condition of insulating materials. There are some different optical phenomena detected from the surface of alumina and polymers, and we attribute the preflashover phenomena to the differences between the surfaces of different insulating materials and different electrode contacts. The experimental results reveal that, under low electric field, prior to field electron emission from the cathode triple junction, electroluminescence phenomena occur due to the radiative recombination of electrons and holes injected into the surface states from the electrodes. According to the results, the phenomena mentioned above are related to the surface states in the surface layer of a material. This work is a contribution to the traditional secondary electron emission avalanche (SEEA) model. View full abstract»

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    Sudden Flashover Of Nonceramic Insulators In Artificial Contamination Tests


    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 4 , Issue: 3
    DOI: 10.1109/TDEI.1997.598293
    Publication Year: 1997 , Page(s): 348

    IEEE Journals & Magazines

    First Page of the Article
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    A laboratory investigation of the flashover performance of outdoor insulators covered with ice

    Farzaneh, M. ; Kienicki, J. ; Martin, R.
    Properties and Applications of Dielectric Materials, 1994., Proceedings of the 4th International Conference on

    Volume: 2
    DOI: 10.1109/ICPADM.1994.414052
    Publication Year: 1994 , Page(s): 483 - 486 vol.2
    Cited by:  Papers (8)

    IEEE Conference Publications

    This paper presents the results of a laboratory study of AC flashover performance of an EPDM (ethylene propylene diene monomer) composite insulator covered with wet-grown ice formed from supercooled droplets. Withstand voltage (Vws) of the insulator string was determined using a method based on IEC 507. The results of Vws obtained using EPDM were compared to those measured using IEEE standard insulators iced under similar conditions. This study is of particular usefulness in the design of compact lines using composite insulators View full abstract»

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    AC flashover performance of insulators covered with artificial ice

    Farzaneh, M. ; Drapeau, J.F.
    Power Delivery, IEEE Transactions on

    Volume: 10 , Issue: 2
    DOI: 10.1109/61.400824
    Publication Year: 1995 , Page(s): 1038 - 1051
    Cited by:  Papers (77)

    IEEE Journals & Magazines

    A field observation of ice accretion on Hydro-Quebec HV insulators was carried out, as well as a laboratory investigation of the AC flashover performance of various types of insulators covered with artificial ice. The field observations made it possible to identify the type and physical aspect of naturally occurring ice accretions produced during freezing rain precipitation. The laboratory investigation was conducted in a 4.8×2.8 m×3.8 m climate room using a HV transformer of 120 kV, 240 kVA with a short-circuit impedance of 5%. A method based on the standard IEC 507 method was developed for measuring the maximum withstand voltage (VWS) of ice-covered insulators. Various factors were investigated, including the effects on the insulator VWS of such particulars as type, thickness, and uniformity of the ice, as well as the arcing distance of the insulators and the conductivity of freezing water. The effects of uniform ice, 2 cm thick, on 5 IEEE insulator units was thus considered to be equivalent to the effect of an ESDD of about 0.13 mg/cm2 on the same insulators View full abstract»

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    Experimental investigation of influence of surface roughness on flashover performance of ceramics in vacuum

    Lijian Ding ; Youping Tu ; Li, C.R. ; Wei Wang
    Electrical Insulation, 2004. Conference Record of the 2004 IEEE International Symposium on

    DOI: 10.1109/ELINSL.2004.1380553
    Publication Year: 2004 , Page(s): 261 - 264
    Cited by:  Papers (2)

    IEEE Conference Publications

    This paper provides some experimental investigation on the influence of the surface roughness on the flashover performance of ceramics in vacuum. The test samples were prepared with four kinds of ceramics (99.9% Alumina) which were polished by four different SiC abrasives. The flashover performances of 20 kinds of test samples have been tested with an impulse voltage in vacuum. According to the experimental results, it was found that the roughness of the test sample was quite different among different ceramics although the same grinding procedure was used with the same abrasive. It was also found that the flashover performance was influenced by the surface roughness, and there is a trend that the samples with a lower surface roughness have a higher breakdown voltage. View full abstract»

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    Progress in resolving flashovers of FRP hot sticks during EHV live line work

    McDermid, W. ; Swatek, D.R. ; Bromley, J.C.
    Electrical Insulation, 2004. Conference Record of the 2004 IEEE International Symposium on

    DOI: 10.1109/ELINSL.2004.1380690
    Publication Year: 2004 , Page(s): 548 - 551
    Cited by:  Papers (8)

    IEEE Conference Publications

    In 1997 a FRP hot stick flashed over during live line work at 550 kV AC. In spite of improvements in the maintenance and testing of the hot sticks, a second flashover occurred during similar work in 2002. A low level of surface pollution is believed to have been the cause of the more recent flashover. Laboratory tests have shown that the leakage distance of the FRP hot stick needs to be substantially greater than the minimum air gap approach distance. View full abstract»

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    DC flashover of a dielectric surface in atmospheric conditions

    Krile, J.T. ; Neuber, A. ; Dickens, J.C. ; Krompholz, Hermann G.
    Plasma Science, IEEE Transactions on

    Volume: 32 , Issue: 5 , Part: 1
    DOI: 10.1109/TPS.2004.835483
    Publication Year: 2004 , Page(s): 1828 - 1834
    Cited by:  Papers (11)

    IEEE Journals & Magazines

    Surface flashover is a major consideration in a wide variety of high-voltage applications, and yet has not been studied in great detail for atmospheric conditions, with modern diagnostic tools. Environmental conditions to be considered include pressure, humidity, and gas present in the volume surrounding the dielectric. In order to gain knowledge into the underlying process involved in dielectric surface flashover, a setup has been created to produce and closely monitor the flashover event. Within the setup parameters such as geometry, material, and temporal characteristics of the applied voltage can be altered. Current, voltage, luminosity, and optical emission spectra are measured with nanosecond to subnanosecond resolution. Spatially and temporally resolved light emission data is also gathered along the arc channel. Our fast imaging data show a distinct trend for the spark in air to closely follow the surface even if an electrical field with a strong normal component is present. This tendency is lacking in the presence of gases such as nitrogen, where the spark follows more closely the electric field lines and develops away from the surface. Further, the breakdown voltage in all measured gases decreases with increasing humidity, in some cases as much as 50% with an increase from 10% relative humidity to 90% relative humidity. View full abstract»

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    Performance of flashover on the resin spacer surface in N2/SF6 and SF6/air gas mixture under AC power frequency

    Cong Wang ; Youping Tu ; Xiao Li ; Rong Tan
    Electrical Insulation (ISEI), Conference Record of the 2012 IEEE International Symposium on

    DOI: 10.1109/ELINSL.2012.6251444
    Publication Year: 2012 , Page(s): 141 - 144

    IEEE Conference Publications

    With the development of the electric power and railway industry, more and more SF6 gas-insulated equipments have been applied. However the greenhouse effect and environmental pollution that caused by SF6 gas has been paid attention in recent years. Therefore looking for the SF6 alternative gas without reducing its insulation performance becomes one of the research hotspots. Epoxy resin has been widely used as the preferred material of post insulator in cubicle type gas insulated switchgear (C-GIS) for its excellent dielectric performance and mechanical properties. In this paper, the power frequency surface flashover characteristics tests are done on the epoxy resin insulator which is in the SF6-N2 and SF6-air gas mixtures with lower pressure range, nonuniform electric field. The test results show that the insulator's power frequency surface flashover voltage increases linearly with the increasing pressure, the proportion of SF6 in the gas mixture influences the insulator's power frequency surface flashover voltage greatly, and adding a small amount of SF6 to the pure N2 or the pure Air can significantly improve the insulator's power frequency surface flashover voltage. With the proportion of SF6 in the gas mixture increasing, the insulator's power frequency surface flashover voltage increases with a saturation trend. View full abstract»

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    The influence of magnetic fields on dielectric surface flashover

    Korzekwa, R. ; Lehr, M. ; Krompholz, H. ; Kristansen, M.
    Power Modulator Symposium, 1990., IEEE Conference Record of the 1990 Nineteenth

    DOI: 10.1109/MODSYM.1990.201008
    Publication Year: 1990 , Page(s): 277 - 280

    IEEE Conference Publications

    The effect of magnetic fields on dielectric surface flashover was investigated using two experimental setups, one with DC magnetic fields and the other with pulsed magnetic fields produced by currents of up to 175 kA. The observed insulation effects depend on the dielectric material, ambient gas pressure, surface roughness, and the presence of background plasma. It is sufficient to place the magnetic field in the vicinity of the cathode region only. For practical applications, small low-cost NdFe permanent magnets can be used, even for plasma background conditions with an electron density of 104 cm-3. The flashover voltage retains the characteristic dependence proportional to the square root of the gap distance with and without the applied magnetic field for DC magnetic field experiments View full abstract»

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    DC flashover performance and effect of sheds configuration on polluted and ice–covered composite insulators at low atmospheric pressure

    Xingliang Jiang ; Yafeng Chao ; Zhijin Zhang ; Jianlin Hu ; Lichun Shu
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 18 , Issue: 1
    DOI: 10.1109/TDEI.2011.5704498
    Publication Year: 2011 , Page(s): 97 - 105
    Cited by:  Papers (14)

    IEEE Journals & Magazines

    How to choose external insulation under high altitude, pollution and icing conditions for UHVDC transmission project is a complicated problem. To provide technical reference to this engineering roadblock, the dc icing flashover performance of seven types of pre-polluted short samples of composite insulators at low air pressure simulated by the multifunction artificial climate chamber was researched in this paper. The influences of ice thickness, pollution and air pressure on icing flashover performance were analyzed. The correct formula of dc icing flashover gradient of seven types of pre-polluted specimens at high altitude was presented. The influence of the sheds configuration parameters on the flashover gradient was discussed. And the selection of sheds configuration was suggested. View full abstract»

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    Creepage Flashover Characteristics of Oil/Pressboard Interfaces and Their Scale Effects

    Okubo, H. ; Okamura, K. ; Ikeda, M. ; Yanabu, S.
    Power Engineering Review, IEEE

    Volume: PER-7 , Issue: 1
    DOI: 10.1109/MPER.1987.5527310
    Publication Year: 1987 , Page(s): 44 - 45

    IEEE Journals & Magazines

    First Page of the Article
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    Phase-Phase Switching, Suite Flashovers: Weather Correction Factors

    Grant, Ian S. ; Paulson, Albert S. ; Presser, M.A.
    Power Apparatus and Systems, IEEE Transactions on

    Volume: PAS-100 , Issue: 4
    DOI: 10.1109/TPAS.1981.316522
    Publication Year: 1981 , Page(s): 1820 - 1828

    IEEE Journals & Magazines

    Weather correction factors for spacings of 3 to 12 feet have been obtained from phase-phase switching surge flashover tests. New statistical methods of analysis of flashover data were used to show that correction factors published for phase-ground flashovers are inadequate for phase-phase. Correction factors for phase-phase flashovers calculated from relative air density, humidity, and relative humidity are given. View full abstract»

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    Study on fog flashover performance and fog-water conductivity correction coefficient for polluted insulators

    Jiang Xingliang ; Zhao Shihua ; Xie Yanbin ; Zhang Zhijin ; Shu Lichun
    Generation, Transmission & Distribution, IET

    Volume: 7 , Issue: 2
    DOI: 10.1049/iet-gtd.2012.0651
    Publication Year: 2013 , Page(s): 145 - 153

    IET Journals & Magazines

    The pollution flashover performance of insulators is generally tested by the steam fog method. However, environmental temperature in tests differs greatly, so the dispensability of test results is high. Moreover, the influence of fog-water conductivity has not been taken into account. Compared with the steam fog method, the cold-fog method simulating natural fog is more consistent with the actual operating conditions of transmission line insulators. This deals with the influence of salt deposit density (SDD) and fog-water conductivity on pollution flashover performance. The influence of the two factors is determined by analysing the results of laboratory experiments where polluted insulators were tested by using the cold-fog method. The results show that the 50% AC pollution flashover voltage (U50) decreases as SDD and fog-water conductivity increase. The correction coefficient (K) indicating the influence of fog-water conductivity on U50 can be expressed as an exponential function, where the factors are 0.0476, 0.0587 and 0.0567 for samples A, B and C, respectively. View full abstract»

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    Flashover voltage prediction of outdoor insulators subjected to road salt contamination

    Venkataraman, S. ; Gorur, R.S.
    Electrical Insulation and Dielectric Phenomena, 2005. CEIDP '05. 2005 Annual Report Conference on

    DOI: 10.1109/CEIDP.2005.1560679
    Publication Year: 2005 , Page(s): 293 - 296
    Cited by:  Papers (1)

    IEEE Conference Publications

    A new approach has been developed to predict the flashover voltage (FOV) of contaminated porcelain insulators based on surface resistance (SR) measurement performed at low voltage under wet conditions. The emphasis of this paper is on contamination resulting from the use of road salts in winter for deicing. Electric field simulations were performed to determine the role of water droplets at the tip of the sheds, which can contribute to flashover at lower contamination severities. The approach has been extended to polymer or nonceramic insulators. View full abstract»

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    Influences of grading ring arrangement on AC flashover performance of 220 KV ice-covered composite insulators

    Lichun Shu ; Shijing Wang ; Xingliang Jiang ; Qin Hu ; Yanzhun He ; Zhi Wu
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 21 , Issue: 6
    DOI: 10.1109/TDEI.2014.004646
    Publication Year: 2014 , Page(s): 2652 - 2661

    IEEE Journals & Magazines

    The grading ring (GR) can adjust the potential distribution along the composite insulator and reduce the electric field (E-field) strengths near its end fittings. However, little research has been conducted about the effects of GR on the insulation performance of composite insulators under icing condition. Therefore, the ac icing flashover performance of two kinds of 220 kV composite insulators under different GR arrangement patterns are tested in the artificial climate chamber. Combining with the numerical simulation, the effects are analyzed. The results indicate that when GR is installed at the high voltage (HV) end, the E-field strength close to the end fitting and the icing uniformity on the whole insulators are both improved. These cause the effect of icing degree on the icing flashover voltage to be larger than that without GR at the HV end. When GR is installed at the grounded end, the perpendicular icicles on the GR will impact the flashover arc path, which causes the icing flashover voltages to be lower than that without GR at the grounded end. When different GRs are only installed at the HV end, the characteristic exponents b (characterizing the influence of freezing water conductivity on icing flashover voltage) are all larger than that without GR. Moreover, the value of b increases with the decrease of GR's diameter and with the raise of GR's height. But b changes slightly when there are variations in GR's pipe diameter and structure. The research can provide reference for the application of GR for 220 kV composite insulators in icing regions. View full abstract»

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    Investigation of Contamination Flashover Voltage of A Porcelain Long Rod Insulator with Silicone Rubber Coating on The Trunks

    Gautam, B.S. ; Matsumura, S. ; Matsushita, S. ; Hashimoto, T. ; Sakanishi, K. ; Matsuoka, R.
    Properties and applications of Dielectric Materials, 2006. 8th International Conference on

    DOI: 10.1109/ICPADM.2006.284247
    Publication Year: 2006 , Page(s): 591 - 594
    Cited by:  Papers (1)

    IEEE Conference Publications

    Higher flashover voltages of transmission line polymer insulators were found to be due to large ratio of shed to trunk diameter. This causes current density at the trunks to be very high and all the trunks get dried causing the applied voltage to the whole insulator divided and allotted to individual trunks. Similar effect was aimed by applying hydrophobic silicone rubber coating to the trunks of a porcelain long rod insulator. In this paper, investigation results of the contamination flashover voltages of porcelain long rod insulators coated with RTV silicone rubber coating on the trunks are presented View full abstract»

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    Comparison of AC flashover performance for line post and pin post insulators in distribution 22 kV

    Thipprasert, W. ; Jirapong, P.
    Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology (ECTI-CON), 2012 9th International Conference on

    DOI: 10.1109/ECTICon.2012.6254199
    Publication Year: 2012 , Page(s): 1 - 4

    IEEE Conference Publications

    Electrical insulators of the Provincial Electricity Authority (PEA) of medium system are mostly porcelain insulator types that consists of suspension, pin type, line post, and pin post insulators. The distribution lines will be polluted by industrial contaminants, salt fog or natural dust. Experience shows that pollution flashover is one of the main natural calamities harming and affecting the voltage stability and reliability of distribution system. This paper compares the test results obtained from artificial pollution tests according to IEC 60507 with line post type and pin post type insulators of medium system under same test conditions. The salt fog test results indicate that the pollution flashover performance of line post insulator is less than to 50 percent of wet power frequency withstand voltage at equivalent salt deposit density (ESDD) = 0.5 mg/cm2 and the leakage current (LC) of line post insulator increased to 10.2 mA at ESDD = 0.5 mg/cm2 at nominal voltage. In the experiment indicate that AC pollution flashover performance of pin post insulator has better than line post insulator in the serious pollution area. View full abstract»

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    Electrostatic discharge test with simulated coverglass flashover for multi-junction GaAs/Ge solar array design

    Bao Hoang ; Wong, F. ; Funderburk, V.V. ; Mengu Cho ; Toyoda, K. ; Masui, H.
    Photovoltaic Specialists Conference (PVSC), 2010 35th IEEE

    DOI: 10.1109/PVSC.2010.5614721
    Publication Year: 2010 , Page(s): 001118 - 001123
    Cited by:  Papers (7)

    IEEE Conference Publications

    Space Systems/Loral (SS/L) successfully completed electrostatic discharge (ESD) tests of Multi-junction (MJ) GaAs/Ge solar array design in geosynchronous space environment. This ESD test was based on ISO-11221, Space systems - Space solar panels -Spacecraft Charging Induced Electrostatic Discharge Test Methods. In addition to the ISO reference for the test schematic, SS/L implemented modified test circuitry to better simulate the on-orbit operational conditions of our solar array design. The ESD test circuit also included simulated solar array panel coverglass flashover. The ESD test program utilized a 25-cell coupon that had been subjected to 2,000 thermal cycles caused by earth eclipses in GEO orbit and >12,000 thermal cycles caused by the shadow of the spacecraft antennas. Other ESD test coupons are 4-cell coupons that, after baseline ESD experiments, can later be subjected to combined space environmental exposures tests. To demonstrate design robustness, we performed ESD tests to voltages and currents that are higher than that of on-orbit solar array operational voltages and currents. This paper discusses the coverglass flashover simulation, ESD test setup, the importance of the electrical test design in simulating the on-orbit operational conditions, and the test results. View full abstract»

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    Time-to-Flashover Characteristics of Polluted Insulation

    Zoledziowski, S.
    Power Apparatus and Systems, IEEE Transactions on

    Volume: PAS-87 , Issue: 6
    DOI: 10.1109/TPAS.1968.292106
    Publication Year: 1968 , Page(s): 1397 - 1404
    Cited by:  Papers (6)

    IEEE Journals & Magazines

    It is shown that times to flashover obtained by von Cron and Dorsh with alternating voltage on an artificially polluted insulator can be fitted into a relation ( V2-V02) t = KR2 where V is the applied voltage, t is the time to flashover, R is the resistance of pollution, and Vo and K are experimental constants. Experiments were carried out using pulse unidirectional voltage applied to a narrow conductive path of water solution of sodium chloride, and the empirical expression obtained was V2-V02) ¿ CR2L3 where L is the leakage length and C is another experimental constant. These relations are explained as results of an energy equation p·¿t = e·¿t where¿t at is the time required to extend the discharge by ¿x, p being the power available for the discharge Propagation and e the energy required to elongate the discharge by a unit length. View full abstract»

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    Influence of heat treatment in atmosphere on surface flashover characteristics of alumina in vacuum

    Asari, N. ; Shioiri, T. ; Sato, J. ; Matuso, K. ; Kojima, H. ; Hayakawa, N.
    Discharges and Electrical Insulation in Vacuum (ISDEIV), 2014 International Symposium on

    DOI: 10.1109/DEIV.2014.6961626
    Publication Year: 2014 , Page(s): 89 - 92

    IEEE Conference Publications

    Alumina Ceramics are widely used for vacuum insulation in devices such as vacuum interrupters. In development and design of vacuum interrupters, it is very important to improve the flashover characteristics on alumina ceramic surfaces in a vacuum. Thus, it is necessary to clarify the flashover mechanism on alumina ceramics in a vacuum. From past research, it is well-known that these characteristics are influenced by the insulation material, its surface condition, surface charging of the insulator and so on.(1) This paper presents the results of measurements of surface flashover characteristics and the cathode luminescence (C.L.) spectra after heat treatment in the atmosphere. These results are compared with those without heat treatment in the atmosphere. It is thus found that oxygen defects on an alumina ceramic surface decreases and the flashover voltage is improved by heat treatment in the atmosphere. View full abstract»

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    Characteristics of interface charges on oil-pressboard insulation and their influence on flashover under polarity reversal voltage

    Bo Qi ; Chunjia Gao ; Chengrong Li ; Linjie Zhao ; Xiaqing Sun
    Electrical Insulation and Dielectric Phenomena (CEIDP), 2015 IEEE Conference on

    DOI: 10.1109/CEIDP.2015.7352093
    Publication Year: 2015 , Page(s): 844 - 847

    IEEE Conference Publications

    Converter transformer is one of the important apparatus of high voltage direct current (HVDC) transmission system. Because of the complex structures and operating conditions, the winding of valve side of converter transformer will withstand DC voltage, combined AC-DC voltage and even polarity reversal voltage, and the insulating properties of which under polarity reversal voltage has drawn great attention. Under the special condition, the interface charge will be accumulated on the oil-pressboard interface, which can directly affect the electric field distribution of the converter transformer dielectric and even decrease the flashover voltage. Therefore, it is necessary to study the characteristics of interface charges and their influence on flashover voltage. The oil-pressboard insulation test platform is designed in this paper, including the interface charge of oil-pressboard insulation measurement platform and polarity reversal test platform. The minimum spatial resolution of interface charge measurement platform is about 1mm2, and its measuring sensitivity can reach 0.129pC/mm2. This paper adopts a needle-plate test model for measurement. The reversal time of the polarity reversal test apparatus is on the level of millisecond that conforms to the actual operation of the converter transformer. The experimental results under polarity reversal voltage indicated that the interfacial charge could greatly reduce the flashover voltage of polarity reversal, and the surface potential produced by charges can be up to 40% of polarization voltage. The changes of oil-pressboard interface charge density before and after the polarity reversal have been measured. It is found that the electric field produced by interface charge can strengthen the maximum synthesis field intensity of the needle electrode after polarity reversal, thus greatly decreases the flashover voltage. View full abstract»

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    Influence of surface ion exchange on pulsed flashover characteristics of machinable ceramics in vacuum

    Nan Zheng ; Guan-Jun Zhang ; Huang, Xue-Zeng ; Peng Zhai ; Xin-Pei Ma ; Guang-Xin Li
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 18 , Issue: 4
    DOI: 10.1109/TDEI.2011.5976089
    Publication Year: 2011 , Page(s): 1011 - 1016
    Cited by:  Papers (1)

    IEEE Journals & Magazines

    For pulsed power devices, the surface flashover across their solid insulation becomes a serious problem. Investigators have paid much attention on improving the surface electric withstanding strength of insulator. It is found that surface treatment is very useful to increase the surface flashover voltage. The flashover phenomena along machinable ceramics (MCs) are investigated under pulsed voltage in vacuum. The ion exchange method is used to adjust the surface components of MCs for improving its surface electric strength. CuSO4 is used for ion exchanging with the MC. It is found that ion exchange treatment greatly changes the surface components and microstructure of MCs, which has obvious influence on flashover characteristics of MCs. The MCs with 10 h ion-exchange time show a much improved flashover holdoff. Based on the secondary electron emission avalanche (SEEA) theory, the improvement of flashover withstanding ability can be reasonably explained by electron impact and transport behaviors. View full abstract»

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    Parametric analysis of overvoltages caused by back-flashover in “Siah-bishe” 400kV GIS substation

    Babaei, M. ; Babaei, M. ; Niasati, M.
    Electric Power and Energy Conversion Systems (EPECS), 2013 3rd International Conference on

    DOI: 10.1109/EPECS.2013.6713049
    Publication Year: 2013 , Page(s): 1 - 6

    IEEE Conference Publications

    This paper presents the way of implementation of transient modeling concepts which are fully analyzed in referred standards, for the purpose of evaluating the lightning performance of studied system caused by back-flashover. In this regard, the impact of several parameters on lightning behavior of the system has been studied. The focus of this paper is on the lightning study of “Siah-bishe” 400kV gas insulated substation (GIS) and practical application of the study to the insulation design of this substation as a substation with a distinctive arrangement of equipment. This practical application has been rarely done before. The study was carried out by modeling all pieces of equipment in EMTP-RV and careful consideration of different modeling guidelines and instructions described in available standards. View full abstract»

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    On-line monitoring of insulator contamination causing flashover based on acoustic emission

    Pei, C.M. ; Shu, N.Q. ; Li, L. ; Li, Z.P. ; Peng, H.
    Electric Utility Deregulation and Restructuring and Power Technologies, 2008. DRPT 2008. Third International Conference on

    DOI: 10.1109/DRPT.2008.4523673
    Publication Year: 2008 , Page(s): 1667 - 1671
    Cited by:  Papers (1)

    IEEE Conference Publications

    Conventional electrical measurements of polluted- insulator partial discharge (PD) activity have certain inherent limitations, which have prompted the research of non-electrical techniques. An acoustic emission (AE) monitoring method is presented in this paper. When a partial discharge occurs, there is an instantaneous release of energy, some of which is emitted as acoustic energy. Through detecting the sound signals, the pollution severities of insulators in-service can be monitored and accordingly threaten to the insulation of power grid is evaluated. Therefore preventive steps will be taken efficiently and quickly to avoid the happening of flashover. Artificial contaminations experiments are aid in acquiring important information about the relationship of AE signal and PD, in which the sound signals are obtained in different moments of flashover process. The studied method is a new way of AE technique in monitoring and characterizing defects of electrical power equipments in-service. View full abstract»

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    Influence of nonsoluble contaminants on the flashover voltages of artificially contaminated insulators

    Matsuoka, R. ; Kondo, K. ; Naito, K. ; Ishii, M.
    Power Delivery, IEEE Transactions on

    Volume: 11 , Issue: 1
    DOI: 10.1109/61.484042
    Publication Year: 1996 , Page(s): 420 - 430
    Cited by:  Papers (30)

    IEEE Journals & Magazines

    This paper describes the results of investigation into the influence of a kind of nonsoluble contaminant (Tonoko or Kaolin) on flashover voltages of artificially contaminated insulators. The deposit density of Kaolin on the insulator surface is less than that of Tonoko when contaminated with the suspension containing the same amount of Tonoko or Kaolin. However, a discernible difference is observed in contamination flashover voltage between these two nonsoluble contaminants, not only under DC but also under AC when nonsoluble contaminant deposit densities (NSDD) are adjusted to the same degree. The difference in the performance is considered attributable to the less uniform contaminant layer produced by Tonoko suspension compared with Kaolin. When a dispersion agent was added to Tonoko suspension, which does not give any influence on the conductivity of the suspension, the layer uniformity and flashover voltage (FOV) for this modified Tonoko suspension became almost equal to those for Kaolin View full abstract»

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    AC flashover performance and voltage correction of 27.5 and 110 kV iced composite insulator at 4000∼5500 m high altitude districts

    Jiang Xing-liang ; Sun Cai-xin ; Sima Wen-xia ; Tian Yu-chun ; Shu Li-chun
    Power System Technology, 2002. Proceedings. PowerCon 2002. International Conference on

    Volume: 3
    DOI: 10.1109/ICPST.2002.1067861
    Publication Year: 2002 , Page(s): 1890 - 1894 vol.3
    Cited by:  Papers (5)

    IEEE Conference Publications

    Based on the test results carried out in the multi-function artificial climate chamber of Chongqing University (China) on two types of composite insulator, this paper discusses the effects of atmospheric pressures or altitudes, contamination level and ice amount secreted on the minimum AC flashover voltages of composite insulators, and analyzes the flashover performance of the composite insulator in icing, contaminating and low pressure conditions. The authors therefore put forward a correction method of flashover voltages. View full abstract»

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    Nanodielectric surface flashover studies under kHZ range pulsed fields in partial vacuum

    Fang Li ; Kirkici, H.
    Power Modulator and High Voltage Conference (IPMHVC), 2010 IEEE International

    DOI: 10.1109/IPMHVC.2010.5958391
    Publication Year: 2010 , Page(s): 453 - 456

    IEEE Conference Publications

    In this paper, we present the experimental results of surface flashover characteristics of nanodielectric filled epoxy resin in partial pressure of nitrogen. Nano-sized Al2O3 and TiO2 powder are used as fillers in epoxy resin with known properties. The surface flashover studies are conducted first under dc applied field and then 20 kHz pulsed unipolar field. The voltage, current, and light emission waveforms during the flashover events are recorded. The optical data is also collected by a video camera. All of the samples are produced in-house and for each sample, two weight ratios, namely 1:50, 1:16.6 (2% and 6%) (powder/epoxy), are cast on Teflon plates. Copper electrodes are mounted over the surface of dielectric samples to initiate surface flashover. The results of surface flashover voltages as a function of pressure are presented. Additionally, optical emission characteristics along with the voltage and current waveform data are also presented. View full abstract»

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    Flashover of Contaminated Insulators with Cylindrical Symmetry under DC Conditions

    Jolly, D.C. ; Poole, C.D.
    Electrical Insulation, IEEE Transactions on

    Volume: EI-14 , Issue: 2
    DOI: 10.1109/TEI.1979.298159
    Publication Year: 1979 , Page(s): 77 - 84
    Cited by:  Papers (11)

    IEEE Journals & Magazines

    A series of experiments was done to determine how contamination flashover occurs under dc conditions. It was found that polarity influenced the flashover voltage, with flashover occurring more readily for negative polarity. Several reasons are advanced to explain this, including cathode spot phenomena, and electrochemical effects. Further experiments showed electrochemical alteration of the amount, type, and distribution of surface contaminant during simulated fog exposure. This will affect the interpretation of artificial test results and should be taken into account in evaluating insulator designs. View full abstract»

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    Equivalence of Influence of Pollution Simulating Methods on DC Flashover Stress of Ice-Covered Insulators

    Xingliang Jiang ; Ling Chen ; Zhijin Zhang ; Caixin Sun ; Jianlin Hu
    Power Delivery, IEEE Transactions on

    Volume: 25 , Issue: 4
    DOI: 10.1109/TPWRD.2009.2032329
    Publication Year: 2010 , Page(s): 2113 - 2120
    Cited by:  Papers (12)

    IEEE Journals & Magazines

    The solid-layer method (SLM) and the icing-water- conductivity method (IWCM) are widely used in the insulator icing tests, but little research has been dedicated to the equivalence of these two methods. Based on the research on dc flashover performance of ice-covered insulators in the artificial climate chamber, this paper studied the equivalent relation between SLM and IWCM according to the equivalent principle of the flashover stress of ice-covered insulators. The results show that the influence of these two methods on flashover stress of iced insulator is equivalent, and this equivalence is determined by the configuration of insulator as well as the icing degree, but the icing flashover stress of the same type of insulators which are on the same pollution level simulated by the two different methods is consistent. View full abstract»

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    What polymers and fiberglass reinforced plastics (FRP) may add to classical primary insulation of distribution system construction for withstanding lightning critical flashover voltages (CFO)

    Shwehdi, M.H. ; Quasem, M.A. ; Elhadri, M.
    Electrical Insulation, 1994., Conference Record of the 1994 IEEE International Symposium on

    DOI: 10.1109/ELINSL.1994.401433
    Publication Year: 1994 , Page(s): 205 - 208

    IEEE Conference Publications

    Insulation composites used on present-day distribution lines frequently consist of two or more types of materials such as wood, porcelain, polymers and fiberglass reinforced plastics (FRP) connected in series. A study included the laboratory determination of the critical flashover voltage (CFO) of 17 single component, 90 combinations of 2 component and 80 combinations of 3 component, and the acquired data were used to develop methods of predicting CFO levels of various multiple series electrical insulations. This paper illustrates the results and analyses of the classical primary insulation (porcelain), and of the modern-day insulation of polymers or FRP. It also presents results of whether these newly emerged FRP and polymers may add or supplement insulation strength to the two and three dielectrics combination. The paper also presents advantages and guidelines for the use of polymers and FRP to either replace or complement porcelain. This may help optimize the choice of dielectrics on distribution lines View full abstract»

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    Spectroscopic observations of surface flashover across an insulator in vacuum under pulsed excitation

    Li, C.R. ; Sundararaman, R. ; Sudarshan, T.S.
    Plasma Science, IEEE Transactions on

    Volume: 21 , Issue: 5
    DOI: 10.1109/27.249651
    Publication Year: 1993 , Page(s): 598 - 604
    Cited by:  Papers (13)

    IEEE Journals & Magazines

    Spectroscopic investigations of surface flashover of insulators are performed with materials such as alumina and PMMA (polymethyl methacrylate) in vacuum under the application of a high-voltage pulse. The spectra of emitted light from the flashover plasma reveal the roles played by the background gases in the system (H atomic line and N2 molecular band), desorbed gases such as CO from the insulator, material defects (AlO molecular bands), and excited species of the electrode material (as seen from the atomic lines Al I, Al II, and Al III). In contrast, the spectra of the preflashover phenomenon shows only the AlO bands and a weak molecular CO band. This observation suggest that not only desorbed gases, but also material defects from the specimen insulator, can be a dominant cause for the initiation of the surface flashover plasma in vacuum View full abstract»

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    Surface flashover strength of different insulating materials in N 2-SF6 gas mixtures under combined AC/DC voltages

    Sundara Rajan, J. ; Dwarakanath, K. ; Srinivasan, N.
    Electrical Insulating Materials, 2001. (ISEIM 2001). Proceedings of 2001 International Symposium on

    DOI: 10.1109/ISEIM.2001.973641
    Publication Year: 2001 , Page(s): 262 - 265

    IEEE Conference Publications

    Performance of insulating spacers in SF6-N2 gas mixture will be an important design factor in deciding the choice of spacer materials. In this study, 5 different polymers have been comparatively evaluated for surface flashover strengths in SF6-N2 gas mixtures of different proportions. The effect of AC, DC and combined AC/DC voltages on these spacer materials has been discussed. Compatibility of two different materials in terms of flashover behavior is also discussed. Though cycloaliphatic resin spacers show good performance, other spacer materials have distinct advantages in terms of surface tracking, bulk failure, and breakdown under combined and composite AC/DC voltages View full abstract»

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    The influence of charge on surface flashover

    Fouracre, R.A. ; Twema, F.A. ; MacGregor, S.J. ; Given, M.J.
    High Voltage Engineering, 1999. Eleventh International Symposium on (Conf. Publ. No. 467)

    Volume: 3
    DOI: 10.1049/cp:19990766
    Publication Year: 1999 , Page(s): 329 - 332 vol.3
    Cited by:  Papers (1)

    IET Conference Publications

    The presence of surface charge can significantly affect the properties of surface discharges such as the initiation voltage, the appearance and the geometrical structure. The charge may be produced through injection, from the electrodes, at triple junction sites, from contact and tribo-charging, or from gaseous ionisation processes. The pre-charging of a dielectric surface has been used in the generation of long, surface discharges. This has enabled surface discharges of up 5 metres in length to be generated and investigated using modest voltages in the range 10-30 kV. The generation of such discharges has facilitated a detailed study into surface discharge characteristics. The system used to generate the surface discharges is described along with results which indicate the propagation velocity and the factors which affect this. Variations in the discharge behaviour with voltage magnitude and polarity are described. A study of the emission spectra from discharges in SF6 and air is presented and the effect of surface charge on the spectral content is shown View full abstract»

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    Flashover problems caused by ice build up on insulators

    Farzaneh, M. ; Kiernicki, J.
    Electrical Insulation Magazine, IEEE

    Volume: 11 , Issue: 2
    DOI: 10.1109/57.372510
    Publication Year: 1995 , Page(s): 5 - 17
    Cited by:  Papers (71)

    IEEE Journals & Magazines

    The number of single-phase faults in the transmission networks in wintertime increases substantially during cold atmosphere precipitation and after ice accretions followed by a rise in air temperature above 0°C.<> View full abstract»

  • Freely Available from IEEE

    Estimation of Flashover Rates of Overhead Power Distribution Lines by Lightning Strokes to Nearby Ground

    Chowdhuri, P.
    Power Engineering Review, IEEE

    Volume: 9 , Issue: 7
    DOI: 10.1109/MPER.1989.4310843
    Publication Year: 1989 , Page(s): 84

    IEEE Journals & Magazines

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    Study on the vacuum surface flashover characteristics of epoxy composites with microTiO2 fillers under steep high-voltage impulse

    Wang, Z.B. ; Cheng, Y.H. ; Chen, Y. ; Ding, M. ; Zhou, J.B. ; Meng, G.D. ; Wu, K.
    Properties and Applications of Dielectric Materials, 2009. ICPADM 2009. IEEE 9th International Conference on the

    DOI: 10.1109/ICPADM.2009.5252343
    Publication Year: 2009 , Page(s): 667 - 670

    IEEE Conference Publications

    With the tendency towards higher power, higher capacity and less scale of the pulsed-power devices, the vacuum surface flashover strength turns to be a primary limitation of the development of the pulsed-power equipments, as it is much lower than the vacuum breakdown strength. To improve the different capabilities of the epoxy composite material, different kinds of micron inorganics are filled to the epoxy resin. TiO2 (TO) is a typical kind of oxide ceramic, as well as an important sort of broad band-gap oxide semiconductor material. With its unique optical and electrical properties, excellent chemical stability, high dielectric constant and semi-conductive properties, it is widely applied to enhance the performance of the organic composite material. In this article, the experimental results of vaccum surface flashover characteristics of epoxy resin and epoxy resin cast with 1 mum powdered TO samples are presented. In addition, their dielectric spectrum and thermally stimulated depolarization current (TSDC) are measured. Considering the influence of the dielectric constant, the conductivity, the trap energy and the trap density, associated with the interface theory, the article analyzes the influence mechanism of micro-scale TO fillers on the vacuum flashover voltage of epoxy composite material. View full abstract»

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    The estimation of flashover voltage as 20 kV outdoor insulator in tropical environment based on leakage current data

    Yandri, V.R.
    Electrical Engineering and Informatics (ICEEI), 2011 International Conference on

    DOI: 10.1109/ICEEI.2011.6021833
    Publication Year: 2011 , Page(s): 1 - 5

    IEEE Conference Publications

    This paper explains the research results of leakage current, and flashover voltage on ceramics as 20 kV outdoor insulator in a chamber at tropical climate conditions. The waveform of leakage current (LC) was measured using a digital oscilloscope. The digital data was transferred to a personal computer using a RS-232 cable. The digital data was analyzed using Fast Fourier Transform. The result showed that LC was affected by various environment conditions like temperature, humidity and pollution. The estimation of flashover voltage for ceramics insulator is calculated based on leakage current data by using simulation in some softwares, i.e SPSS and MATLAB. This value is different for low and high humidity condition, i.e 0.20 kV/mm for low humidity and 0.15 kV/mm for high humidity. These estimation values are not much different with data from the producer of ceramics insulator. View full abstract»

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    Influence of fluorination time on surface flashover of epoxy in insulating gas

    Mohamad, A. ; Chen, G. ; Du, B.X.
    Electrical Insulation Conference (EIC), 2015 IEEE

    DOI: 10.1109/ICACACT.2014.7223576
    Publication Year: 2015 , Page(s): 384 - 387

    IEEE Conference Publications

    The accumulation of charges on polymeric insulation under high voltage DC stress is a major concern in the transmission system as its formation distorts the local electric field and has an adverse impact on the electrical performance. By undergoing fluorination treatment on the insulation, improved surface properties similar to fluoropolymers can be attained without changing the bulk properties of the original material. The change in chemical components at the surface of polymeric insulation should lead to a corresponding change in electrical properties at the surface and thus can suppress charge build up. Previous research on surface flashover on fluorinated epoxy resin at atmospheric condition shows a significant improvement in flashover strength. In this paper, the authors investigated the effect of different degree of fluorination treatment on cast epoxy resin on suppressing surface charge accumulation and its contribution towards the improvement in surface breakdown strength. In comparison to previous research, it has been found that there is an optimum time duration of fluorination treatment which improves the surface breakdown strength of epoxy spacer. The mechanisms that govern the effect of fluorination treatment on surface flashover were discussed. View full abstract»

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    Flashover prevention on high-altitude HVAC transmission line insulator strings

    Daochun Huang ; Jiangjun Ruan ; Wei Cai ; Tianwei Li ; Yuanhang Wei ; Jia Liu
    Dielectrics and Electrical Insulation, IEEE Transactions on

    Volume: 16 , Issue: 1
    DOI: 10.1109/TDEI.2009.4784555
    Publication Year: 2009 , Page(s): 88 - 98
    Cited by:  Papers (1)

    IEEE Journals & Magazines

    Numerical analysis, on-site measurements, and laboratory experiments are used in this paper to analyze and solve the flashover problems of 330 kV AC high altitudes transmission line middle phase glass suspension insulator strings. A sub-model approach based on a finite element method (FEM) applied in calculating the potential and electric field distribution along the insulator strings under clean and dry conditions. Using this approach, three dimensional electrostatic models (taking into account the grading rings, subconductors, tower framework, and yoke plates) are set up and investigated. On-site and laboratory measurements were also carried out to make a comparison. A relatively good agreement was obtained among the calculated, the on-site, and the laboratory measured results, which demonstrated that insulator disk nearest to the high-voltage end is required to withstand relatively high voltage according to the standard in China; in addition, the insufficient dry arc distance of the insulator strings is also proposed. Subsequently, the long insulator-string flashover tests under dry, wet, and artificial contaminated (ESDD=0.05 mg/cm/2, NSDD=0.3 mg/cm/2) conditions, considering the middle (flashover) and side phase (never flashover), respectively, are carried out to validate the proposed insufficient dry arc distance and discuss the measures for solving the flashovers. From the effective, convenient and economical standpoint for the reconstruction of the flashover lines, lowering the grading rings' position and adding a unit of insulator are considered to lengthen the dry arc distance of the middle-phase insulator string in the tests. The experimental results are compared and discussed, and it has been concluded that adding a unit of insulator is an effective and economical way to solve the flashover problems. The methods for analyzing the flashover problems are effective and can be used for other voltage-level transmission lines. View full abstract»

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    Effects of Voltage Gradient Distribution on External Flashovers of Polluted Outdoor High Voltage Power Plant

    Alame, N. ; Shihab, S.
    Athens Power Tech, 1993. APT 93. Proceedings. Joint International Power Conference

    Volume: 1
    DOI: 10.1109/APT.1993.686843
    Publication Year: 1993 , Page(s): 57 - 60
    Cited by:  Papers (1)

    IEEE Conference Publications

    First Page of the Article
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    Impulse flashover in liquid nitrogen along a glass tube with a gas layer inside

    Ohki, M. ; Saito, S.
    Properties and Applications of Dielectric Materials, 1991., Proceedings of the 3rd International Conference on

    DOI: 10.1109/ICPADM.1991.172085
    Publication Year: 1991 , Page(s): 415 - 418 vol.1

    IEEE Conference Publications

    In atmospheric air, impulse flashover voltage along the outer surface of a layered dielectric composition, composed of two coaxial hard glass cylinders with a gas layer in between, is known to have a V-shaped curve as a function of the pressure of the gas layer. The authors examine whether such a phenomenon also occurs in liquid nitrogen. It was found that impulse flashover voltage in liquid nitrogen along the outer surface of the glass tube, inside which a gas layer exists, also shows a V-shaped pressure dependence, which is similar to the dependence observed in the case of atmospheric air. In normal hexane at room temperature, however, such as V-shaped pressure dependence was not observed. It is suggested, therefore, that gas bubbles vaporized in non-pressurized liquid nitrogen play an important role in the flashover mechanism. This finding is not only interesting from the viewpoint of discharge physics, but is also important in designing bushings or feedthroughs for electrical insulation at cryogenic temperatures View full abstract»

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    Influence of the thickness and the nature of HVAC insulator model on the flashover voltage and the leakage current

    Teguar, M. ; Namane, D. ; Mekhaldi, A.
    Solid Dielectrics (ICSD), 2013 IEEE International Conference on

    DOI: 10.1109/ICSD.2013.6619796
    Publication Year: 2013 , Page(s): 186 - 189

    IEEE Conference Publications

    The aim of this study is to analyze the behavior of an insulating plan model. For this purpose, we have interested to the variation of the flashover voltage and the leakage current according to the thickness and the relative permittivity (nature) of the dielectric. Two materials were used: glass and plexiglass. The experimental study has been supported and explained by a numerical approach based on analysis of the charge and the field distributions using FEMM 4.0 software. The main results obtained show that the flashover voltage is practically independent of both nature and thickness of the insulator model. It depends only on the distance between electrodes. However, the leakage current depends significantly on the nature, the thickness of the dielectric and the distance between electrodes. Indeed, the measurement of leakage currents is influenced by the insulating material and its volume proportions. View full abstract»

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    The influence of magnetic fields on dielectric surface flashover

    Korzekwa, R. ; Lehr, F.M. ; Krompholz, Hermann G. ; Kristiansen, M.
    Electron Devices, IEEE Transactions on

    Volume: 38 , Issue: 4
    DOI: 10.1109/16.75200
    Publication Year: 1991 , Page(s): 745 - 749
    Cited by:  Papers (4)

    IEEE Journals & Magazines

    The influence of low-amplitude magnetic fields, in a variety of configurations, on pulsed dielectric surface flashover has been investigated. These variations include DC magnetic fields; pulsed magnetic fields simulating conditions for magnetic self-insulation; and different environments (vacuum, ambient, gas, plasma), geometries, dielectric materials, and orientations of the magnetic field. For field amplitudes of 0.3 T, typically a doubling of the flashover voltage is observed, if the E×B drift is away from the surface. For flashover in vacuum, it is sufficient to place permanent magnets in the cathode vicinity to increase the flashover voltage. The observations are consistent with the saturated surface secondary avalanche model and electron-induced gas desorption. The pulse shape of light emission during the prebreakdown phase depends on the orientation and amplitude of the magnetic field and shows that the electron trajectories above the surface are altered by magnetic fields View full abstract»

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    Flashover between Closely Spaced Electrodes on an Insulating Surface

    Gray, Eoin W.
    Plasma Science, IEEE Transactions on

    Volume: 13 , Issue: 5
    DOI: 10.1109/TPS.1985.4316437
    Publication Year: 1985 , Page(s): 355 - 356

    IEEE Journals & Magazines

    The dc breakdown field strength of copper electrodes separated by an epoxy-glass insulator in air shows a -0.04 (1/25) power dependence on the length of the electrode-insulator-gas triple junction in the range 10-2-102 cm. The breakdown field strength was found to have an electrode-gap spacing power dependence of -0.45 in the range ~ 10-3-~10-1 cm. This is a similar power factor to both that of the Paschen curve for air at atmospheric pressure and for dc-and microsecond-pulsed discharges over insulating surfaces in vacuum. These results may be applicable to various surface discharge switches and surface discharge plasma sources. View full abstract»

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    Effect of Test Geometry, Permittivity Matching and Metal Particles on the Flashover Voltage of Oil/Solid Interfaces

    Anker, Morten U.
    Power Engineering Review, IEEE

    Volume: PER-3 , Issue: 12
    DOI: 10.1109/MPER.1983.5520134
    Publication Year: 1983 , Page(s): 33

    IEEE Journals & Magazines

    First Page of the Article
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