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Dielectric Liquids, 2002. ICDL 2002. Proceedings of 2002 IEEE 14th International Conference on

Date 12-12 July 2002

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  • Proceedings of 2002 IEEE 14th International Conference on Dielectric Liquids. ICDL 2002 (Cat. No.02CH37319)

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    Freely Available from IEEE
  • List of authors

    Page(s): 419 - 422
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    Freely Available from IEEE
  • Experience with UHF partial discharge measurements

    Page(s): 239 - 241
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    Some tests on UHF measuring techniques on transformers and oil-paper insulation models have been reported in literature. The results indicate the feasibility of this method for oil-paper insulation, but are not conclusive. To have a good perspective of this method, UHF partial discharge (PD) measurements were conducted on small oil-paper insulation models, large transformer windings and PD suspect jobs. Classical phase-resolved PD patterns were recorded alongside using an in-house developed system, which permit cycle-by cycle replay and analysis of the PD patterns. Acoustic PD measurements were simultaneously recorded for comparison of relative sensitivities. Experimental investigations reveal that UHF PD measurements can detect, with good sensitivity, small levels of discharges and those buried within insulating layers. In contrast, acoustic measurements can detect small levels of discharges only when a direct line of sight is available between the discharge source and sensor. For discharges buried within insulating layers, acoustic detection is possible only for some cases when discharge level is high. This paper describes the results of the experiments. View full abstract»

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  • Transport properties of electrons injected in dense noble fluids

    Page(s): 369 - 372
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    The unified theory of electron transport properties of Ar, Kr and Xe in a wide range of densities is under development. The theory takes into account an influence of the density effects well-known for these liquids. The nonmonotonic behavior of electron transport coefficients is described in the framework of this theory. View full abstract»

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  • Application of neural networks paradigms in the diagnosis and thermal ageing prediction of transformer oil

    Page(s): 258 - 261
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    In this paper we present the application of some artificial neural networks algorithms to the diagnosis and thermal ageing prediction of transformer oil. The simulation had been validated by experimental results. View full abstract»

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  • Strength investigations on long oil gaps

    Page(s): 228 - 230
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    We deal with the electrical strength properties of oil gaps. The investigations were carried out with uniform electrical fields and electrode distances up to 30 mm. Measurements were performed with alternating current (50 Hz), lightning impulses and switching impulses. Such investigations usually have a relative high dispersion of the measurement values. It will be shown that it is possible to minimize the coefficient of variation to values of about 5 to 6 percent. View full abstract»

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  • Temperature distribution in fluids treated by pulsed electric fields

    Page(s): 67 - 70
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    Measurements of the temperatures around a Pulsed Electric Field (PEF) treatment chamber for preservation of a continuous product flow are presented as a function of flow rate, showing a relative high wall temperature. A limited analytical model as well as a Finite Element Method analysis is also presented and compared to the measurements. View full abstract»

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  • Measurements of ionization current in liquid dielectric mixtures

    Page(s): 279 - 280
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    The article contains further development of the author's problem. I have tested the application of the ionization chamber as a dosimeter. I was measuring the changes of ionization current with the absorption of X-rays by metals. I was changing the thickness of the absorbent for different voltage of the X-lamp. The obtained results have the same character as in the case of other dosimeters used so far (e.g. Geiger-Mueller counter). Therefore my ionization chamber can function as dosimetric chamber (e.g. in medicine), although further research would be demanded to ensure better usage. View full abstract»

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  • Characterization of partial discharge phenomenon on paper insulation under aggravated aging conditions

    Page(s): 433 - 436
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    This paper presents the experimental results of partial discharge activity in paper insulation, namely pressboard and kraft paper. New paper samples of 1 mm thickness were used. The partial discharge occurrence in paper insulation under various combinations of the aging parameters such as different electrode configurations, different operating voltages, different oil temperatures, presence of water on the samples and the growth of microbiological (fungus) content on the samples was analyzed. View full abstract»

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  • Surface conductivity in liquid-solid interface due to image force

    Page(s): 270 - 273
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    The image force is considered to be one of the nonspecific sources of surface conductivity origin in the interface between a non-polar liquid dielectric and a polar solid one. Two possible physical mechanisms have been investigated. The first one takes into account the existence of a potential barrier to the charge movement as it leaves the surface. Therefore the charges that are in liquid are attracted to the surface. The second one is the reduction of dissociation energy of ion pairs close to the interface in comparison with bulk dissociation. Both mechanisms result in a decrease of recombination rate and in a sharp increase of dissociation rate. It has been shown that both these mechanisms could lead to creation and accumulation of an abnormal nonspecific surface charge carrier. Preliminary experimental results don't contradict theory. Surface conductivity of ceramics with ε=80 in contact with transformer oil (ε=2.3) is sharply increased in case of slight dissociating organic doping. View full abstract»

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  • The application of new diagnostic protocols for the condition-based assessment of high-voltage electrical equipment

    Page(s): 312 - 316
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    The diagnostic testing of insulation systems provides data that can be used to quantify the condition of high-voltage electrical equipment such as tap changers, circuit breakers, regulators and transformers. Using recently developed algorithms, condition codes for these types of equipment are generated using laboratory and field data. These codes are used to determine when maintenance is necessary and to establish priorities for maintenance. This paper describes how these condition codes are applied within condition-based maintenance programs. Case studies are included that illustrate the reliability and the fiscal impact of the protocols. View full abstract»

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  • Liquid rare gas detectors: recent developments and applications

    Page(s): 405 - 411
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    In the past few years, the liquid rare gas detectors (LRGD) have made a considerable progress and found application in various fields of research, such as high energy experiments, astrophysics, search of rare processes and medical imaging. In this paper, the two best established technologies based on liquid rare gases - electromagnetic calorimeters and time projection chambers - are briefly reviewed, together with their applications. The bulk of the paper is focused on the challenging development of LRGD for the search of rare processes in low background experiments and on the promising application of LRGD to medical imaging. The present status of some of the more significant developments under way is presented. View full abstract»

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  • The universal discharge mechanism in mineral oil and possible estimation of its breakdown voltage

    Page(s): 107 - 110
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    The complex experimental studies of the discharge mechanism in transformer oil using of alternative diagnostic methods under positive lightning impulse were carried out. The attempt to establish connection between the macroscopic features of discharge and the breakdown were made. View full abstract»

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  • Fluid circulation in an enclosure generated by electrohydrodynamic conduction phenomenon

    Page(s): 41 - 44
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    Fluid circulation/mixing inside an enclosure, non-mechanically, is of significant importance in various applications. This study investigates, theoretically, the circulation of an isothermal fluid inside an enclosure based on the electrohydrodynamic (EHD) conduction phenomenon. The theoretical model and the numerical solutions are presented in dimensionless forms to illustrate the effects of the controlling parameters on the induced flow. View full abstract»

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  • Technical development and future perspectives on the application and performance of dielectric liquids

    Page(s): 231 - 236
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    In this paper, the recent trends of electrical insulation in liquid dielectrics am described. The development results of the higher stress/compact design equipment, environment-friendly ester-oil, insulation diagnostic technique, higher temperature application, etc., as well as cryogenic electrical insulation are introduced. In particular, it is pointed out that the charge carriers in liquid dielectrics will be a key factor to control the higher stress electrical insulation and therefore the basic research on charge behavior and the physical mechanism should be extended for the future. View full abstract»

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  • Structure and energy spectrum of negative ions in non-polar liquids

    Page(s): 56 - 58
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    The electron photodetachment energy from a negative ion increases significantly inside a nonpolar liquid in comparison with its value in the vacuum. It is customary to consider that it is a result of the polarization interaction of the ion with the atoms or molecules of the liquid. However, the exchange interaction of the outer electron of the negative ion with the electrons of the external atomic shells of the neutrals also plays an important role. This interaction may result in the creation of voids or bubbles around the negative ions which are similar to the electron bubbles in liquid helium and some other liquids. The electron binding energy of negative ions of different atoms and molecules injected in liquid rare gases and some hydrocarbons is calculated with taking into account of the quantum nature of the outer electron state and the possibility of the creation of a void near the ion. View full abstract»

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  • On mechanisms involved in the propagation of subsonic positive streamers in cyclohexane

    Page(s): 143 - 146
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    This paper presents a study of slow positive streamers in cyclohexane under impulse voltage. A high sensitivity differential technique is used to record the streamer charge, together with high speed visualization. At voltages below the breakdown voltage, streamers stop while the voltage is still applied. It is shown that the first event preceding stopping is the hydrodynamic collapse of streamer filaments close to the point. This collapse "propagates" from the point to the streamer head, and the streamer then totally disappears. As soon as the streamer collapse starts, the streamer current is stopped, no more electrical energy is supplied, and liquid vaporization ceases. However, the streamer head still propagates at a reduced velocity. These observations constitute a direct evidence of the influence of space charges and electric field (i.e. electrostatic pressure) on propagation processes. View full abstract»

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  • Instability of electrically stressed water droplets in oil

    Page(s): 220 - 224
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    The breakup of water droplets in an electric field has been studied in naphtenic oil as a function of water conductivity and surface tension of the droplets, and frequency and waveform of the applied voltage. The critical breakup field compares well to theoretical values for low voltage frequencies, but large deviations are found for frequencies above 100 Hz. Four different instability modes are observed at droplet breakup. View full abstract»

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  • Correlations of electron attachment parameters with carcinogenic properties of matter

    Page(s): 429 - 432
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    The distribution of chemicals divided into carcinogens and noncarcinogens over electron attachment rate constant is presented. View full abstract»

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  • Evolution of current pulses in liquid argon induced by a sharp point cathode

    Page(s): 59 - 62
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    The Trichel pulses induced by a sharp point cathode in liquid argon are discussed. A crude analysis of the phenomena shows that the apparent charge carrier mobility is proportional to the current pulse duration in a given duration range. A very rough estimate of this time qualitatively accounts for its observed variations with the applied voltage in a liquid sample highly purified through the injection of electrons. View full abstract»

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  • Electrical, laser and acoustic breakdown of a liquid, resemblance and distinctions

    Page(s): 163 - 166
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    For the first time, the analysis of generality and distinction of the physical phenomena occurring in a liquid at nonlinear absorption of pulse energy of different kinds (electric, laser, acoustic) is presented. These problems are analyzed from position of transformation of one kind of energy into others. Physical and hydrodynamic phenomena are investigated at focusing of single laser pulse into water, single acoustic wave into water, and various ways of localization of energy in a liquid under action single pulses of electric energy. Mechanisms of electric, laser and acoustic-shock breakdowns of a liquid are compared. View full abstract»

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  • Measurement equipment for investigation of the influence of viscosity of dielectric working fluids on spark erosion

    Page(s): 301 - 304
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    In the paper functional goals of the measurement equipment for the investigation of electrical discharges in dielectric working fluids are discussed. Electrical discharges take place at electrode distances smaller than 200 μm. As an example the influence of the viscosity on the ignition behaviour and on typical phases of the spark erosion are analyzed. View full abstract»

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  • Stochastic model of breakdown initiation in dielectric liquids under AC voltage

    Page(s): 115 - 118
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    The electric strength of perfluorodibutyl ether and transformer oil in small gaps between hemispherical electrodes was investigated experimentally under an AC voltage of linearly increasing amplitude. The influence of the radius of the hemispherical electrodes, gap lengths and also rate of voltage increase on probability of breakdown initiation was investigated. In the macroscopic stochastic approach, breakdown initiation is described by a macroscopic function μ(E). This function is a probability density of the streamer initiation. The dependences of breakdown initiation probability on various parameters of the experiment were obtained for flat, cylindrical and hemispherical electrodes under DC and AC voltages of linearly increasing amplitude. The method of fixed breakdown probability was developed to reconstruct the function μ(E) in the case of non power-law approximation using experimental data on a series of breakdown voltages. The values of the function μ(E) for transformer oil and perfluorodibutyl ether were determined in the range of electric field 0.3-1.0 MV/cm. Stochastic computer simulations of breakdown inception were carried out. View full abstract»

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  • Aging of Kraft paper in natural ester dielectric fluid

    Page(s): 173 - 177
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    Kraft transformer insulation paper aged in natural ester (vegetable oil) dielectric fluid was compared to identical paper aged in conventional transformer mineral oil. Sealed steel aging tubes containing copper, aluminum, Kraft paper, and dielectric fluid (mineral oil and natural ester) were aged at 150°C for 500, 1000, 2000, and 4000 hours. The extent of paper degradation after aging was determined using paper tensile strength, paper degree of polymerization, and furanic compounds in the aged fluid. Water contents of fluids and paper were compared. Paper aged in conventional transformer oil degraded at a significantly faster rate than in natural ester dielectric fluid. Paper in mineral oil reached three criteria for IEEE end-of-life (50% retained tensile strength, 25% retained tensile strength, and degree of polymerization of 200) within the first 1000 hours. After 4000 hours of aging, paper in natural ester did not degrade to any of the IEEE end-of-life criteria. At 4,000 hours, the paper aged in natural ester retained about 55% of the original tensile strength and a degree of polymerization of about 280. Paper aged in conventional transformer oil degraded to the same values in about 315 and 390 hours, respectively-an order of magnitude faster. The reduced paper-aging rate in natural ester is primarily attributed to the fluid maintaining the paper in a very dry state. View full abstract»

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  • Spectroscopic investigation of electrical discharges in liquids

    Page(s): 285 - 288
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    Prebreakdown phenomena occurring in liquids are linked with emitted light in the UV, visible and IR range. A spectroscopic analysis of this light can be used to evaluate some fundamental parameters of the discharge such as energy of charge carriers, kinetic temperature of neutral molecules, electron density, etc.. In this paper, we describe the main difficulties to overcome to carry out a spectroscopic analysis in dense fluids. View full abstract»

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