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Electrical Insulation, IEEE Transactions on

Issue 6 • Date Dec. 1982

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Displaying Results 1 - 23 of 23
  • Table of contents

    Page(s): c1
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  • IEEE Electrical Insulation Society

    Page(s): c2
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  • Elementary Processes in the Development of the Electrical Breakdown of Liquids

    Page(s): 478 - 483
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  • Breakdown in Solid Dielectrics

    Page(s): 484 - 487
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    This paper summarizes several aspects of breakdown in solid dielectrics, with emphasis on the distinction between electrical and thermal effects. Several current theories are discussed. View full abstract»

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  • Effect of Space Charge and Structure on Breakdown of Liquid and Solid

    Page(s): 488 - 492
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    Space charge and structural change in solid and liquid dielectrics play important roles as positive feedback mechanisms for breakdown. In case of a KCl single crystal, introduction of F centers by ¿-ray irradiation strongly modifies breakdown voltage due to the space-charge field distortion at cathode asperities: homo-type space charge (F' center) increases and hetero-type space charge (ionized F center) decreases dc breakdown voltage, while impulse breakdown is not affected. In case of a polyethylene film, space charge at the crystalline -amorphous boundary due to trapped carrier plays an important role for breakdown. These space charge effects disappear at higher temperature by detrapping. Space-charge field enhancement at streamer etips gives rise to the difference between positive and negative streamer propagations in liquids and solids, causing higher propagation velocities and longer streamers in liquids in the former case. Judging from pressure effects, negative streamers in liquid are usually strongly related to the presence of low density regions (bubbles), whereas positive streamers are not. However, liuqid He shows a peculiar polarity effect possibly due to formation of electron bubbles. Both streamer and bubble mechanisms coexist in liquid breakdown. The predominance depends on conditions such as pressure, electrode distance, voltage pulse duration, boiling point, electrode asperities, etc. View full abstract»

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  • Breakdown Across a Dielectric Spacer in Insulating Oil and the Role of Electrohydrodynamics in Liquid Breakdown

    Page(s): 493 - 498
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    Electrohydrodynamics is an important contributing factor in liquid breakdown, and may contribute to the breakdown across a dielectric spacer in oil. The two topics are discussed separately. View full abstract»

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  • Some Aspects of Breakdown in Gases

    Page(s): 499 - 504
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    This paper discusses the occurrence of corona in small, highly-stressed, regions in large apparatus. View full abstract»

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  • Gas Breakdown in Case of Steep-Fronted Pulses and Insulator Interfaces

    Page(s): 505 - 511
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    Two fundamental factors influencing the insulating characteristics of compressed gases are steep-fronted overvoltages and interfaces between gas and solid insulators. In order to estimate the influence of steep-fronted overvoltages it is necessary to know the limiting voltage-time-characteristics, that is the formative time lag. Especially in electronegative gases it is necessary to separate the statistical time lag from the formative time lag as the first time interval may be many orders of magnitude higher than the second. It will be shown that especially in SF6 the formative time lag may be either extremely short or rather long, mainly influenced by the field distribution. In compressed gas insulation the breakdown voltage is reduced by even ¿clean¿ insulator surfaces. In this case breakdown is induced by one or several micro-discharges caused by local field enhancement at the insulator surface. Further electron multiplication must be caused by photoionization. Breakdown occurs if several micro-discharges develop and grow together. View full abstract»

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  • Streamer Propagation in Liquids and over Liquid-Solid Interfaces

    Page(s): 512 - 516
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    The recent activity in the area of pre-breakdown streamer development has produced a considerable quantity of data characterizing the phenomena. It is not the aim of this paper to review this work in detail, much of which has been discussed in two recent reviews [1,2]. Rather we hope to point out from this work in non-uniform field geometries, some interesting observationswhich are striking and could offer insight into the mechanisms operative, yet at present remainunexplained. View full abstract»

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  • The Search for Universal Features of Electrical Breakdown in Solids, Liquids and Gases

    Page(s): 517 - 521
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    This paper discusses the commonality of electrical breakdown phenomena in gases, liquids, and solids. It is shown experimentally that the change in density fluctuations occurring in the three phases is the strongest common influence in the development of electrical breakdown. View full abstract»

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  • High-Field Electronic Conduction in Liquid Nitrogen

    Page(s): 522 - 532
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    Conduction characteristics between a needle and a plane electrode in liquid nitrogen (LN2) were investigated when a negative dc voltage was applied to the needle. Both characteristics, the overall time of voltage application T vs current I and the applied voltage V vs current I, showed the onset currents at specific values of applied voltage. On the other hand, it was found that positive triboelectric charge was produced when LN2 was forced through a metal pipe from a Dewar into a cryostat. By applying the Fowler-Nordheim theory, we showed that electron emission from a cathode was greatly influenced by both the layer of positive ions and microscopic projections on the cathode surface. Parameters in the theory concerning the emission of electrons from the cathode have not been made clear, but in this paper, they were investigated and numerically determined. View full abstract»

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  • Electrical Conduction in Synthetic Insulating Liquid

    Page(s): 533 - 538
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    Electric conduction and dielectric loss of synthetic aromatic insulating liquid for capacitor use were studied. The dielectric loss was found to originate from the ionic conduction and to depend on the concentration of impurities in the liquid. The conduction phenomena of the liquid can be divided into two temperature regions. In the low-temperature region, below about room temperature, the temperature dependence of conductivity is governed mainly by ionic carrier mobility. In the high-temperature region, however, it is characterized by thermal dissociation 0of impurities as well as carrier transport process. It was also established from the identical activation energies for mobility and viscosity that the carrier mobility is governed by the viscosity of the liquid. When an artificial impurity is dissolved in the liquid, a reduction in activation energy of the conductivity is observed in high temperature and the conduction mechanism is mainly dominated by the carrier mobility; no appreciable change was obtained in the low-temperature region. View full abstract»

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  • On the Mechanism of Treeing Inhibition by Additives in Polyethylene

    Page(s): 539 - 545
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    On the basis of the experimental observation that the conductivity of acetophenone-doped polyethylene is field dependent over a range of applied electric stresses, a simple analysis shows that the increase in resistance to electrical treeing by additives is associated with this field-dependent conductivity. The additives can be considered as weak electrolytes. The rate of their dissociation into positive and negative charge carriers which causes an increase in conductivity is field dependent. A model for the behavior of the additives which leads to the lowering of the electrical stress at sites of high and divergent electrical stresses is given. Presently available experimental results are in good agreement with our proposed theory. Other factors affecting this mechanism are also discussed. View full abstract»

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  • Effects of Temperature and Voltage on Dielectric Breakdown Strengths of PET and FRP under Mechanical Stresses

    Page(s): 546 - 553
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    The electric insulators for superconducting magnet coils to be used in a large fusion reactor are subjected to large compressive and tensile stresses to a maximum level of about 400 MPa, and these stresses should pose a significant electrical insulating problem in practice. In this paper, dc and ac dielectric breakdown characteristics of PET and FRP under mechanical stress at liquid nitrogen (LN2) temperature are presented as part of a comprehensive study for electrical insulating design of superconducting magnet coils to be used in a large fusion reactor. The results presented are complementary to those already reported for ac at room temperature. The dielectric breakdwon strength (DBS) of PET and FRP under compressive stress at 77 K shows similar variations to those obtained with ac at room temperature: the DBS increases at first, reaches a maximum value, and falls thereafter. The maximum DBS is little influenced by the temperature variation, but the compressive stress showing the maximum DBS depends strongly on the temperature regardless of voltage sources used. Under tensile stress the DBS of PET and FRP at 77 K is higher than at room temperature at a given tensile stress. View full abstract»

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  • Effect of Frequency on the Growth of Water Trees in Polyethylene

    Page(s): 554 - 559
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    The effect of frequency on the growth of water trees in polyethylene has been investigated using the water needle test. An accelerating effect was observed up to a maximum between 4 and 8 kHz with both NaCl solution and deionized water. This phenomenon cannot be ascribed to a frequency dependence of the electrical behavior of the trees. It results from the mechanical properties of the polymer itself and can be interpreted by analogy with environmental stress cracking. The frequency dependence of the growth rate appears to be a consequence of the existence of a mechanical absorption peak in polyethylene located at about 30 kHz at room temperature. View full abstract»

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  • Partial Discharges in a Cylindrical Void with a Metal Rod Electrode

    Page(s): 560 - 569
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    The distributions of the rate of partial discharge magnitudes, here called the discharge intensities, were studied in artificial voids having configurations proposed earlier for the endurance testing of materials using a multichannel analyzer, while the following parameters were varied: applied voltage, polarity, test duration, void sealing, void gap, ambient gas, rod geometry and treatment of the specimens. The intensity of partial discharges was to some extent affected by all of these factors, but the gas in the void was particularly significant. The differential rate density of discharge intensity is largely controlled by the availability of negative ions for dissocation or the presence of overstressed high field regions. Many of the parameters varied in the present study affected these features. Sporadic discharges were noted where the quantity of charge was greater than the theoretical maximum values by a factor of up to two. This was noted with all geometries. The occurrence of discharges to the wall of the void was the source of the above disparity. View full abstract»

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  • Meetings

    Page(s): 570
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  • Errata

    Page(s): 570
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  • Impulse Breakdown of Prestressed Polyethylene Films in the NS Range

    Page(s): 571 - 576
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    This paper describes the effect of prestressing on the breakdown strength and time lag of low-density polyethylene films subjected to square pulses of 100 ns width. When prestress and impulse fields are opposite in polarity, the 50% breakdown strength Eb decreases from 4.9 to 3.4 MV/cm as the prestressing field is increased from 0 to 4.6 MV/cm. When prestress and impulse fields have the same polarity, Eb increases to 5.4 MV/cm as the prestress is increased to 4.1 MV/cm. The dc breakdown strength is 5.8 MV/cm. The formative time lag tf decreases with increasing applied field. The value of tf is insensitive to the level of prestress within a given mode. The mode of opposite prestress yields considerably larger values of tf than the other two modesof no and same prestress, and at relatively low applied fields. The apparent electron mobility calculated from tf increases from 2.2×10-2 to 2.4×10-1 cm2/Vs as the total (prestress+ pulse) applied field is changed from 3.0 to 6.0 MV/cm. The results are attributed to a modification of the field intensity near the electrodes due to space charge accumulation during the period of prestressing. The breakdown mechanism is discussed on the basis of an avalanche-streamertransition in the gaseous breakdown theories. View full abstract»

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  • 1982 Index IEEE Transactions on Electrical Insulation Vol. EI-17

    Page(s): 577 - [577]-g
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  • IEEE Electrical Insulation Society

    Page(s): [577]-h
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  • Information for authors

    Page(s): [577]i
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Aims & Scope

This Transactions ceased production in 1993. The current retitled publication is  IEEE Transactions on Dielectrics and Electrical Insulation.

Full Aims & Scope