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Electrical Insulation, IEEE Transactions on

Issue 1 • Date Feb. 1987

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Displaying Results 1 - 25 of 27
  • Table of contents

    Page(s): c1
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  • IEEE Dielectrics and Electrical Insulation Society

    Page(s): c2
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  • Dielectric and Conduction Processes in Polyetherether Ketone (PEEK)

    Page(s): 1 - 7
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    The electrical conductivity and dielectric loss of films of polyether ether ketone have been investigated over a wide range of frequencies and electric fields in the temperature range of 40 to 140°C. The volume resistivity of PEEK was found to be 1014 ¿m at temperatures 80°C but decreased significantly above this temperature. The dielectric loss factor was found to be 0.01 in the frequency range 100 Hz to 100 kHz, but two lowfrequency loss processes were observed by thermally stimulated discharge measurements. The excellent high-temperature mechnical properties suggest that PEEK may be useful as the insulating material on low voltage communication cables in hostile environments, but not for power or HV distribution cables over long distances where higher resistivities may be required. View full abstract»

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  • Bulk Modification of Charge Trapping and Conductivity in Linear Low-Density Polyethylene

    Page(s): 9 - 12
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    Antioxidants, neutral phthalocyanine and titanium dioxide were added to "pure" linear low density polyethylene resin, and films were extruded. Charge storage and conduction properties were measured using TSCD and open and short Circuit TSC; and TSPC, respectively. Antioxidants increased negative and positive storage level and reduced conduction activation energies, but had little effect on lifetime. 0.01 wt% of phthalocyanine increased lifetime in the dark (x5) and conduction activation energy. Trapping may take place by the cage-like amine structure. 5 wt% of titanium dioxide increased charge lifetime by a factor of roughly 7. Defect traps were annealed out at low concentrations, and new deep traps were introduced by the titanium dioxide itself at all concentrations. Additive-matrix boundary trapping is another possibility for the latter two additives. View full abstract»

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  • Isothermal and Non-Isothermal Carrier Transport in One-Dimensional Insulators

    Page(s): 13 - 17
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    Transport of charge carriers in one-dimensional systems is considered. Kinetic equations describing trapping and release of carriers are discussed. It is shown that the equilibrium occupancy of traps in one-dimensional systems differs from that in three-dimensional ones. Particular cases of isothermal and non-isothermal carrier transport are presented. View full abstract»

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  • The Effect of Thermal Expansion on Thermally Stimulated Currents in Polyners 1. Elastomeric Materials

    Page(s): 19 - 22
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    Model calculations of thermally stimulated po'larization currents (TSPC) based on the bistable model of Fröhlich show that the current reversals observed in the glass transition range of polymeric materials result not only from the temperature dependence of equilibrium polarization but also from thermal expansion. The contribution of thermal expansion is especially significant in elastomers which are characterized by expansion coefficients that differ markedly above and below the glass transition temperature. A good qualitative and quantitative agreement with all the theoretical predictions has been found in styrene-isoprene-styrene block copolymers. View full abstract»

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  • Surface Chargine of Dielectrics by Secondary Emission and the Determination of Emission Yield

    Page(s): 23 - 28
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    A new method for the determination of the secondary emission yield of dielectrics is discussed. Results are given for Teflon® , Aclar, Kapton® , and Mylar® . Surfaces of dielectrics irradiated with electrons of energies above 2 keV become negatively charged. For lower energies the number of backscattered primaries plus backward emitted secondaries eventually exceeds that of the incoming primaries. Then the surface can be positively charged. It was recognized that this effect might lead to a simple method for the determination of the total backscatter plus secondary emission yield. This effect is used to determine the total emission yield curve in one run with a single beam energy. View full abstract»

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  • Activation Energy Distributions for Electron Traps in Polystyrene

    Page(s): 29 - 33
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    A new form of analysis of thermally stimulated luminescence data is presented, enabling the form of the (concentration capture cross-section) vs. activation energy distribution function of the electron traps in a dielectric to be deduced. At the end of the irradiation the trapped electrons are divided into four groups; namely, the fraction of fo not re-trapped, and the fractions f1, f2, and f3 re-trapped once, twice, and three times, respectively, before recombining with a luminescent center. A distribution consisting of one or more sections of the form n(E) dE¿exp[ai(E-Ei)] dE is assumed, where n(E) dE is the concentration of traps with activation energies between E and E+dE multiplied by their electron capture cross-sections and ai and Ei are constants. A temperature-dependent frequency factor s(T) given by log s(T)= a+b(T-Tirr) is also assumed, where Tirr is the irradiation temperature and a and b are constants; s(T) applies to all traps, independent of E. The paraments ai, Ei, fi a, and b are adjusted to yield best agreement between experimental and synthesized data. Results are presented for polystyrene X-irradiated at liquid nitrogen temperature. View full abstract»

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  • Transient Dielectric Response of Conduction on Humid Mica

    Page(s): 35 - 39
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    In a study aimed at elucidating the physical nature of the widely observed low-frequency dispersion (LFD) in carrier-dominated dielectrics, we report a study of the time dependence of surface conduction on humid mica in relation to the ambient humidity and the amplitude of the step-function voltage. This system shows clear LFD behavior in the frequency domain and is known to be nonlinear with voltage. Surface conduction along the cleavage planes on humid mica is reported to have a time dependence fully consistent with LFD, but while the charging current is proportional to the applied voltage less an internal EMF of approximately 1 V, the discharge current is voltage-independent. The behavior is shown to be fully consistent with a model involving a secondary battery, probably arising at the mica-aluminum contact, and an internal humidity-dependent surface resistance. The results clearly confirm the validity of the earlier assumption that the LFD phenomena are related to electrochemical interactions and cannot be reconciled with normal electrostatic charge and energy storage. The model explains the enormously high low-frequency capacitances observed in many LFD systems, sometimes exceeding 100 F/m2. View full abstract»

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  • Now is the Best Time to Join our Society

    Page(s): 40
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  • Computer-Based Permittivity Measurements and Analysis of Microwave Power Absorption in Conductive Dielectrics

    Page(s): 41 - 46
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    The time domain reflectometer technique is applied to measure the dielectric properties of a pure Debye dielectric mixed with various amounts of salt. The effect of ohmic conductivity on a Debye dielectric is studied as a function of temperature and frequency. A computer simulation technique is used to compare the heating pattern in a conductive dielectric for two microwave absorption frequencies of 2.45 GHz and 915 MHz. View full abstract»

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  • Optimizing Field Stress on High-Voltage Insulators

    Page(s): 47 - 56
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    A method is described for optimizing the field stress on HV insulators by modifying their profile, seeking a uniform distribution of the tangential field among the insulator surface. This results in an increase of the onset voltage for surface flashover and in a significant saving of the space of the HV installation. The optimization process was achieved by an algorithm developed for calculating the tangential field Component and mathematical expressions of the profile to be corrected through an iterative procedure. The algorithm was based on a modified charge-simulation technique to satisfy a better matching of the boundary conditions to the electrode and insulator surfaces involved in the HV installation. The algorithm is expanded to study the effect of contamination on the tangential field distribution. It is found that the higher the conductivity of the contamination layer, the higher is the field uniformity along the insulator surface. View full abstract»

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  • Influence of Oxidation on the Electrical Properties of Inhibited Naphthenic and Paraffinic Transformer Oils

    Page(s): 57 - 62
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    The dc electrical conductivity and dielectric losses of inhibited naphthenic and paraffinic transformer oils were measured as a function of the oxidation time. It is shown that both properties vary with the dissolved-copper, peroxide and soluble-acidity contents of the oils and that these Variations in the electrical properties with oxidation time are directly related to the generation of the aging by-products. Empirical equations relying on these three parameters and describing the conductivity and tan6 of oxidized oil are presented. The role of the chemical structure of the two oils is briefly discussed as well as the effects of filtering the oils after sludge formation. View full abstract»

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  • An Investigation of Ac Electrical Aging Phenomena in Polyethylene by Thermally Stimulated Discharge Current Measurement

    Page(s): 63 - 68
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    In previous work, the authors have shown that electrical aging of polyethylene under ac voltage was due to the build-up of a space charge which was accompanied by light emission. Study of the electroluminescence allowed us to estimate the quantity of charges trapped in the material when ac voltage was applied to the polymer. The present paper reports an investigation on space charge in polyethylene stressed by an ac electric field by the thermally stimulated discharge current (TSDC) technique. Measurements were made on the same samples, i.e., the same polyethylene and the same point-plane electrode set-up as for the light emission study. This gives us a direct comparison of the results obtained using both techniques. It is shown that both the quantity of oxygen dissolved in the material and the amplitude, type and duration of electrical polarization have an influence on the observed peaks. We suggest that the applied electric field modifies the structure of the polymer. View full abstract»

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  • An Analysis of Multi-Factor Aging of Mica-Epoxy Insulation Systems by the Infinite Sequential Stress Method

    Page(s): 69 - 76
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    In most cases the infinite sequential stressing method can be applied in the analysis of multi-factor aging of insulation systems. Although the simultaneous multi-factor aging characteristics cannot be reproduced strictly by sequential stress tests, the characteristic equation for multi-factor aging can be derived by combining all single-factor aging characteristics in sequential stress aging. Generally, such characteristic equations can be represented only in numerical form, but in the case of mica-epoxy insulation systems in which the value of n in the inverse n-th power law remains unchanged during thermal aging, and also the value of thermal aging rate remains unchanged during voltage aging, the characteristic equations for multi-factor aging can be derived in an analytical form. The mechanical aging characteristics determined by repeated bending tests seem to be of two types, uniform degradation, similar to thermal aging, and local degradation, similar to voltage aging. The ratio of these two types depends on the mica (mica-paper or mica-splitting). Characteristic equations for simultaneous thermal, voltage, and mechanical aging also can be derived by the infinite sequential stressing method. This method assumes an infinite repetition of the four kinds of aging: thermal, voltage, uniform mechanical, and local mechanical. View full abstract»

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  • Impulse Electrical Breakdown Fields of Short Vacuum Gaps

    Page(s): 77 - 79
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    Prebreakdown currents for a long-duration impulse voltage were measured as a function of a wide range of gap spacing using a . air of plane-parallel copper electrodes in a vacuum of 3xlO Pa. The field-emitted component of the prebreakdown current was found to follow the Fowler-Nordheim field emission theory and the field enhancement factor at the cathode was determined from the Fowler-Nordheim plot. The B was found to increase from 15 to 230 with increasing electrode separation in the range from 0.003 to 2.5 mm. The breakdown voltage and the average field strength were also measured in the same gap range. It was found that the average field strength decreased from 700 kV/mm to 33 kV/mm with increasing electrode separation, however, the critical microscopic electric field at breakdown is determined to be (10.2±1.5) X107 V/cm in the range investigated. View full abstract»

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  • Premiering in 1987

    Page(s): 80
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  • A New Approach to Treeing Inception Tests

    Page(s): 81 - 86
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    The paper, stressing the importance of better understanding of physical phenomena leading to the inception of treeing in polymeric insulation, presents the quantitative and qualitative advantages of using needle electrodes for tree initiation tests with much sharper tips than those used in propagation studies. The experimental procedure of getting samples with embedded electrode tip radii of about 0.1 pm is presented. Samples of epoxy resin and polyethylene with different levels of crosslinking were investigated. For comparison tests, IEC needle electrodes were also used. Both electrical total charge and partial discharges and optical photoemission phenomena accompanying the initiation phase of treeing were recorded. The results show conclusively the proposed electrodes to give much less scatter in the results, to considerably shorten the test times, and to enable a much better differentiation between various materials with regard to their tree inception behavior than "classical" electrodes. View full abstract»

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  • Particle-Initiated Breakdown Characteristics of Conical Insulator in N2 GAS and N2/02 Mixture under DC Voltage

    Page(s): 87 - 96
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    Particle-initiated breakdown characteristics of conical spacers were investigated experimentally in N2 and 79% N2/21% 02 gas mixture to provide fundamental parameters determining the breakdown voltage of a dielectric spacer contaminated by metallic particles. Experimental results show that the breakdown voltage of a particle-contaminated spacer increases with the value of |90-¿|, while in contrary that of the clean spacer decreases with the value of |90-¿| in the region of ¿ of 0|90-¿|60 degrees where the spacer angle ¿ is defined as the angle between the spacer surface and the anode plane electrode. With a given spacer the breakdown voltage reveals the minimum value (MBDV) when a particle was placed very near the anode in N2/02 mixture, and on or very near the electrodes in N2 gas. At the particle conditions giving the MBDV, the corona stabilization effect is less effective. The MBDV decreases with decreasing in the gas pressure and the wire particle diameter. The critical particle length beyond which the breakdown voltage is lowered by the particle depends on the spacer shape. Analysis of the MBDV to include a minimum electric field necessary for discharge propagation along the spacer surface and the effect of the field enhancements due to particle on a cylindrical spacer shows fairly good agreement with the experimental results. View full abstract»

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  • Time-And Space-Dependent Radiation-Induced Conductivity in Polymer Films: the "TRAPEZOID" Model

    Page(s): 97 - 99
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    In a number of polymer electrets, radiation-induced conductivity (RIC) and its time and space dependence were investigated. Electron-transmission experiments yielded the initial deposition profiles; measurements of the rear-electrode voltages during irradiation with a monoenergetic electron beam permitted determination of the time and the dose-rate dependence of the RIC. From these data, the space-charge and field profiles, and their temporal variations, were calculated on the basis of a newly developed "trapezoid" model for the spatial profile of the RIC. View full abstract»

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  • Dielectric Loss Measurement as a Tool to Determine Electrical Aging of Extruded Polym-Ric Insulated Power Cables

    Page(s): 101 - 105
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    It is shown that deterioration in the insulation of power cables under high voltage stress has such influence on the loss tangent of the material that it can be measured with a sensitive impedance bridge. View full abstract»

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  • Meetings

    Page(s): 106
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  • IEEE copyright form

    Page(s): 110
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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