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Dielectrics and Electrical Insulation, IEEE Transactions on

Issue 5 • Date October 2011

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  • IEEE Transactions on Dielectrics and Electrical Insulation [Front cover]

    Page(s): C1
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  • IEEE Dielectrics and Electrical Insulation Society

    Page(s): C2
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    Freely Available from IEEE
  • Electrostatics [Editorial]

    Page(s): i
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    Freely Available from IEEE
  • Electrification of aerosol particles in supersonic atomizers

    Page(s): 1353 - 1360
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (7867 KB) |  | HTML iconHTML  

    Factors limiting charge-to-mass ratio achievable for induction-charged aerosol produced in supersonic atomizers are discussed. Experimental investigations performed using supersonic atomizers fitted with de Laval nozzle and concentric induction electrode have demonstrated moderately low electrification levels obtained in case of elevated flow rate of liquid being atomized. It was shown that low charging degree is associated with occurrence of shielding effect. A simplified model of conducting liquid charging process was worked out for the case of atomized liquid cone shielded by an "umbrella" of droplets. Manifestation of the shielding phenomenon and regularities arising from the assumed model has been confirmed experimentally. View full abstract»

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  • A century of development in applied electrostatics; nothing static here

    Page(s): 1361 - 1365
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    Although the topic of electrostatics is well known as the earliest of the electrical sciences, it is mainly in the twentieth century that real engineering applications have developed. Today, electrostatic processes are the basis of many important industries in fields as diverse as air pollution control, printing and copying, painting, material's separation and even sandpaper manufacture. Worldwide these applications account for many billions of dollars in annual business. In this paper the meaning of the term electrostatics is discussed and the fundamental properties that lead to these applications reviewed. The important advancements of the past century are highlighted by describing the development of three key processes; electrostatic precipitation, electrostatic painting and coating, and electrophotography. The continuing evolution of the field is put in context by summarizing the fundamental properties of the electrostatic forces and new applications in the fields of MEMS, biotechnology and nanotechnology are suggested. View full abstract»

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  • Electrostatic force behavior of a nonuniformly charged particle on a planar dielectric solid

    Page(s): 1366 - 1373
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    This paper presents the analysis of the electrostatic force on a nonuniformly charged dielectric particle resting on a dielectric solid. The purpose of the analysis is to clarify the force enhancement caused by the nonuniform charging when the particle is on the dielectric solid, and to examine the role of the dielectric solid on the force behavior in the presence of an external electric field. The method of images using multipoles is applied to electric field calculation, and the electrostatic force is determined from the Maxwell stress. The analytical results show significant force enhancement due to nonuniform charging even in the case where the particle and the dielectric solid have the same dielectric-constant value. However, with an externally applied electric field, the nonuniform charging also results in higher force magnitude for detachment of the particle from the plane in comparison with the case of uniform charging. The roles of the dielectric constants of the media involved on the electrostatic force behavior are investigated. Critical difficulty for the detachment is not found for a particle with dielectric constant equal to 4, which is remarkably different from the corresponding case of a particle lying on a conducting plane. View full abstract»

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  • Simulation of space charge dynamics in low-density polyethylene under external electric field and injection barrier heights using discontinuous galerkin method

    Page(s): 1374 - 1382
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    In this paper, a novel high-order accurate numerical method was proposed to simulate the space charge transport in solid dielectrics. It is based on a unified framework, discontinuous Galerkin (DG) method, to solve both charge concentration and electric field. It is easier to implement and more efficient than the combined DG and boundary element method (BEM) with equivalent numerical accuracy. With this new method and symmetric model parameters for low-density polyethylene (LDPE), space charge concentration and electric field distribution under different external electric field and injection barrier heights were obtained. The simulation shows that above an electric field threshold, large oscillations appear in the time-dependent maximum electric field strength and the total charge quantity. This phenomenon can be considered as a sign of a relatively larger quantity of charge injection compared to the low field regime. When the Schottky injection barrier height in the simulation is raised, this electric field threshold also increases in order to maintain a certain amount of carrier injection. View full abstract»

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  • Extension of lightning corona sheath model during return stroke

    Page(s): 1383 - 1392
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    A generalized lightning traveling current source return stroke model has been used to examine the characteristics of the lightning channel corona sheath. A model of lightning channel consisting of a charged corona sheath and a narrow, high conducting central core is assumed. The return stroke process is modeled with the positive charge coming from the channel core discharging the negative leader charge in the corona sheath. According to the corona sheath model proposed earlier by Maslowski and Rakov, it consists of three zones, zone 1 (inner zone containing net positive charge), zone 2 (surrounding zone 1 with negative charge and outer zone 3 without charge. We adopted the assumption of a constant electric field inside zone 1 of the corona sheath proved in the experimental research of the corona discharges in a coaxial geometry of Cooray. This assumption seems to be more realistic than the assumption of a uniform corona space charge density used previously in the study of Maslowski and Rakov, Marjanovic and Cvetic, and Tausanovic et al. Based on the measurements of the electric field performed by Miki et al, the conductivity of the channel sheath in zone 1 is calculated. View full abstract»

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  • Surface potential decay characterization of non-woven electret filter media

    Page(s): 1393 - 1400
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    Electric charging of the non-woven electret filter media leads to increased particle collection efficiency. Estimation of the charge state of the media can be done by measuring its surface potential. The aim of this paper is to evaluate the effects of the factors that influence the surface potential decay characteristics of these media: the grid potential of the triode-type corona electrode system employed for the electric charging, the active carbon, the ambient relative humidity and the temperature at which the media are thermally pre-conditioned. The experiments were carried out on two types of samples, one of which includes an active carbon layer between two 400 μm thick layers of non - woven polypropylene fibers, the diameter of each fiber being approximately 20 μm. The results show that the surface potential values increase with the increasing of the electric potential of the grid. Thus, if the grid potential Vg increases from 3 to 10 kV, the surface potential value increases over 3 times. A 20% increase of the surface potential values is also recorded in the case of thermally conditioned samples. The surface potential decreases by roughly 10% in the case of the samples with carbon layer, and by about 20%, and in the case of relative humidity increase from 21% to 80%. View full abstract»

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  • Electrohydrodynamic secondary flow and particle collection efficiency in a one-sided spike-plate type electrostatic precipitator

    Page(s): 1401 - 1407
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    In this work, results of electrohydrodynamic secondary flow and particle collection efficiency measurements in an electrostatic precipitator under positive and negative voltage polarity are presented. The electrostatic precipitator had two plate collecting electrodes and a single spike discharge electrode. The spike tips were only on one side of the discharge electrode, therefore called a one-sided spike electrode. The electrohydrodynamic secondary flow pattern and collection efficiency measurements were carried out for two one-sided spike electrode positions: with the spike tips directed either upstream or downstream the primary flow. The results of the flow pattern measurement showed different flow patterns for different spike tips positions in respect to the primary flow direction. The electrostatic precipitator collection efficiency measurements clearly showed difference in the particle collection for both spike tips positions. Since the other electrostatic precipitator working parameters were the same, it can be concluded that the observed change of the electrohydrodynamic secondary flow was the main reason of the difference in the electrostatic precipitator collection efficiency. View full abstract»

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  • Simulation of surface potential decay of corona char ged polyimide

    Page(s): 1408 - 1415
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    Surface potential decay (SPD) of corona charged polyimide (PI) films has been studied using different initial potentials Vo. It has been noticed that the rate of decay increases with initial charging levels. Surface potential profile over the surface of the PI films and return potential generated after charge neutralization have been also experimentally recorded. In order to analyse and explain the decay behavior, the recorded SPD in PI film has been computer simulated using a numerical model based on charge transport by hopping of injected carriers between localized trapping centers. Three parameters (transit time tT, trapping time τT and mean capture time before release τF) controlling the decay kinetic have been estimated by fitting procedure. The effects of the electric field strength on the transport parameters have been also discussed. View full abstract»

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  • Effect of trapped space charge on mechanical deformation induced by electric field

    Page(s): 1416 - 1422
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    An organic insulating film of polyethylene naphthalene 2,6-dicarboxylate (PEN) was characterized by two complementary techniques: the mechanical deformation of the sample surface, induced by the application of an electric field, was obtained by an image correlation technique named DIC (Digital Image Correlation) and the space charge distributions in the thickness direction were measured by FLIMM (Focused Laser Intensity Modulation Method). The validation of the DIC method, which consists of a following of the successive positions of the surface patterns of the sample, is presented. To validate the algorithms and evaluate the performance of the technique, it was applied to computer-simulated speckle images. In a second step, the experimental system was applied to measure the mechanical deformations of a PEN film previously charged by an electric field in order to have space charge accumulation. This space charge accumulation was quantified by FLIMM. The results show that the mechanical behavior of the sample is modified by the presence of space charge. View full abstract»

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  • Collection efficiency in narrow electrostatic precipitators with a longitudinal or transverse wire electrode

    Page(s): 1423 - 1428
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    Recently narrow electrostatic precipitators (ESPs) have become a subject of interest because of their possible application in diesel engine exhaust systems. In this work, results of particle collection efficiency measurements in narrow electrostatic precipitators for negative and positive dc voltage polarity are presented. The ESP used in this work was a parallelepiped equipped with wire discharge electrode and two collecting plate-electrodes. The experiments were carried out for two discharge electrode positions: longitudinally or transversely to the main flow direction. The obtained results showed that the collection efficiency strongly depends on the discharge electrode position. It is higher in the ESP with longitudinally-to-flow placed discharge electrode. The collection efficiency is also influenced by the EHD secondary flow generated in the ESP. The EHD secondary flow with high migration velocity (y-component of the particle velocity) and low turbulence intensity increase the chance of the particle deposition on the collecting electrodes. View full abstract»

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  • Electrohydrodynamic gas pump with both insulated electrodes driven by dielectric barrier discharge

    Page(s): 1429 - 1432
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    In this paper, we report the use of a surface dielectric barrier discharge (DBD) for the generation of unidirectional flow inside a glass tube, using external ring electrodes. The electrodes were made of thin metal stripes mounted on the external wall of the glass tube and insulated with resin. One of the electrodes was grounded, the other was connected to an AC power supply. The DBD discharge was generated between the electrodes on the internal wall of the glass tube. As a result, pumping of air through the glass tube occurred. The presented discharge geometry is attractive for electrohydrodynamic (EHD) gas pumping since there is no direct contact between the external discharge electrodes and the pumped medium. The flow rate generated by the EHD pump was calculated using the measured flow velocity maps at the outlet of the pump. The flow velocity maps were obtained using 3D Particle Image Velocimetry (PIV) technique. It was found that the increase in frequency of the ac voltage caused an increase of the flow rate generated by the EHD pump. Accordingly, the increase in the flow rate occurred when the distance between the electrodes had been increased. View full abstract»

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  • Electrostatically induced voltage generated in "metal boxes with different volume" measured by spark gap and electromagnetic wave sensor

    Page(s): 1433 - 1438
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    The movement of a charged body, such as a charged human body or a charged device, often causes a malfunction or failure in an electronic apparatus because an induced voltage is generated in a partially opened metal box of the apparatus. We cannot ignore this type of electronic apparatus malfunction when the relative humidity in a room decreases because of the use of an air conditioner. We need to design the electronic apparatus to safely prevent such malfunctions. The induced voltage generated in the metal box must be measured for the safe design of an electronic apparatus. We measure the induced voltage generated in the metal box without electrical connections using a spark gap and an electromagnetic wave sensor. In this paper, we study the relationship between the induced voltages and the volume of the metal boxes. Five metal boxes with different depths are used to vary the volume of the boxes in the experiment. The measured result shows that the induced voltage generated in the metal box is independent of the volume of the metal boxes (the depth of the boxes). Thus, the value of the induced voltage generated in a small metal box is almost the same as that in a big metal box. Therefore, an induced voltage can be generated in a small metal box, such as a tablet device. The result of this study is useful for the safe design of an electronic apparatus to prevent malfunctions and failure of the apparatus. View full abstract»

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  • Numerical calculations of submicron particle removal in a spike-plate electrostatic precipitator

    Page(s): 1439 - 1452
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    A 3D hybrid Finite Element (FE)-Flux Corrected Transport (FCT) numerical algorithm is proposed to evaluate the electrical characteristics of a laboratory scale single stage spikeplate electrostatic precipitator and to predict the collection of submicron particles with diameters in the range of 0.25-1.5 μm. The precipitator consists of two parallel collecting plates with a spiked electrode mounted at the center, parallel to the planes and excited with a high negative dc voltage. The complex interaction between the electric field, fluid dynamics and the particulate flow in this precipitator are taken into account in the simulation. Particles are assumed to be charged by combined field and diffusion charging mechanisms. Motion of submicron particles under electrostatic and aerodynamic forces in turbulent flow is calculated using a Lagrangian-type Discrete Random Walk (DRW) model and User Defined Functions (UDFs) feature of the commercial FLUENT 6.2 software. The electrohydrodynamic secondary flow patterns, particle migration velocity patterns and particle collection efficiencies are examined for three different corona discharge electrode configurations: spikes located only on one side of the electrode with the tips directed either upstream or downstream of the channel, and spikes located on both sides. For a given particle concentration at inlet, the particle deposition rate along the channel and the average charge-to-mass ratios are evaluated for different particle sizes and applied voltages. Finally, the influence of particle concentration on particle collection efficiency for the ESP with spikes on two sides is investigated for -30 kV applied voltage. In selected cases, the numerical results are compared with the existing experimental data. View full abstract»

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  • Laboratories, professional societies, industrial stakes and networks. A contribution to the history of the contemporary research on electrostatics (1950-2000)

    Page(s): 1453 - 1458
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    The birth and development of modern societies and networks in Electrostatics are analyzed, with a focus on the industrial and social needs underpinning these efforts. A particular emphasis is put on the 1965-1980 period when most of the organization of this field has occurred. Key people and industrial issues were identified with the help of a questionnaire sent to senior researchers in the field. The position and visibility of research in Electrostatics are analyzed. View full abstract»

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  • Electrostatic properties of aged fullerene-doped mineral oil

    Page(s): 1459 - 1462
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    In this paper the analysis of the influence of C60 fullerenes on flow electrification of mineral insulating oil during aging is presented. Three sets of samples, one fresh and two aged for 24 h and 96 h were tested for their electrification properties using an improved version of a spinning disk system. The relations between C60 concentration and electrification current were determined for different rotational velocities. It is shown, that C60 may significantly reduce or increase the electrification current in mineral oil, depending on fullerenes concentration. The possible causes of observed behavior are analyzed. View full abstract»

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  • Numerical simulation of the electrical double layer development: physicochemical model at the solid and dielectric liquid interface for laminar flow electrification phenomenon

    Page(s): 1463 - 1475
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    At the solid-liquid interface, a charge zone called the Electrical Double Layer (EDL) appears. It is constituted of two zones of opposite sign, one in the solid and another one in the liquid. When a liquid flows through a pipe, there is a disturbance of the EDL and an axial streaming current is generated. This current is due to the convection of the charges coming from the electrical double layer. In this paper, we present a numerical simulation of the EDL development process in the case of a liquid containing additives or impurities which are partially dissociated into positive and negative ones. We treat the case of laminar flow and an interfacial reaction whose conversion is small compared to the concentration of positive and negative ions in the bulk solution. The boundary conditions are deduced from the kinetics of the wall surface reactions with additives. However, in this paper, the formation of the EDL at the solid-liquid interface is investigated without any flow (static case). Thus, the rate of the wall reaction and the resulting charge concentration in the liquid can be studied. Then, once the equilibrium of physicochemical reaction is reached, convection is forced and the EDL dynamic behavior has been studied (dynamic case). The physicochemical reaction at the solid-liquid interface, the evolution of the space charge density in terms of both the axial coordinates and flow velocity, and the equations of conservation of charge of the liquid species have been implemented to a developed version of "Electricite de France" finite volume CFD tool Code_Saturne, which is designed to solve the Navier- Stokes equations. Finally, the simulation results of the dynamic behavior at different flow rates are compared with the experimental results. View full abstract»

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  • Tribocharging and electrostatic separation of mixed granular solids in fluidized bed devices

    Page(s): 1476 - 1483
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    Granular materials, when fluidized by air or other gaseous medium, acquire electrostatic charge by inter-particle and particle-wall collisions. The effectiveness of particle tribocharging achieved with such fluidization process is crucial for establishing the feasibility of electrostatic separation of mixed granular solid wastes in the recycling industry. The present paper aims at a crude evaluation of the effects of the main factors that influence the efficiency of such a tribocharger, in the presence of an electric field orthogonally oriented to the direction of the fluidization air. The experiments were carried out on binary mixtures taking combinations of two of the three polymeric materials in different tests: (a) virgin polyamide, (b) polycarbonate and (c) polyacetal granules. The variables investigated were the duration of the tribocharging process, the level of the high-voltage applied to the electrode and the composition of the mixture. The analysis of the experimental data revealed the effects of each variable on the mass and the charge of the granules collected at the electrodes. View full abstract»

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  • Dielectric properties of XLPE/Sio2 nanocomposites based on CIGRE WG D1.24 cooperative test results

    Page(s): 1482 - 1517
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    A comprehensive experimental investigation of XLPE and its nanocomposite with fumed silica (SiO2) has been performed by CIGRE Working Group D1.24, in cooperative tests conducted by a number of members; covering materials characterization, real and imaginary permittivity, dc conductivity, space charge formation, dielectric breakdown strength, and partial discharge resistance. The research is unique, since all test samples were prepared by one source, and then evaluated by several expert members and their research organizations. The XLPE used for preparation of the nanocomposites was a standard commercial material used for extruded power cables. The improved XLPE samples, based on nanocomposite formulations with fumed silica, were prepared specifically for this study. Results of the different investigations are summarized in each section; conclusions are given. Overall, several important improvements over unfilled XLPE are confirmed, which augur well for future potential application in the field of extruded HV and EHV cables. Some differences/discrepancies in the data of participants are thought to be the result of instrumental and individual experimental technique differences. View full abstract»

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  • Microstructure and dielectric characterization of micro- nanosize co-filled composite films with high dielectric permittivity

    Page(s): 1518 - 1525
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    Dielectric composite films of the micro-nanosize BaTiO3 (BT) particles embedded into a polyvinylidene fluoride (PVDF) matrix were prepared by using a simple blending and casting processing. Effects of the micro-nanosize cofilled model at different mciro-nanosize volume ratios of BT particles on microstructure and dielectric properties of the composite films were researched. The results show that the nanosize BT particles can be filled into the gaps between the micron-size BT particles so that a tightly stack structure in the BT/PVDF composite film is formed. As a result, the dielectric properties of the composite films with the micro-nanosize BT loading at 40 vol% is higher than these with single nanosize BT loading solely if the interactions between the BT fillers are considered. The maximum values of dielectric permittivity were about 55 because of the superior internal microstructure of composite films when the mciro-nanosize volume ratio of BT particles is close to 1/1. In this case, a remarkable synergistic effect for improving the dielectric properties was also observed. The microstructure and the assumed cofilled model of the composite films would used to explain the experimental results well. View full abstract»

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  • AC breakdown characteristics of epoxy nanocomposites

    Page(s): 1526 - 1534
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    Experiments were conducted to measure the ac breakdown strength of epoxy alumina nanocomposites with different filler loadings of 0.1, 1 and 5 wt%. The experiments were performed as per the ASTM D 149 standard on samples of thickness 0.5 mm, 1 mm and 3 mm in order to study the effect of thickness on the ac breakdown strength of epoxy nanocomposites. In the case of epoxy alumina nanocomposites it was observed that the ac breakdown strength was marginally lower for 0.1 wt% and 1 wt% filler loadings and then increased at 5 wt% filler loading as compared to the unfilled epoxy. The Weibull shape parameter (β) increased with the addition of nanoparticles to epoxy as well as with the increasing sample thickness for all the filler loadings considered. DSC analysis was done to study the material properties at the filler resin interface in order to understand the effect of the filler loading and thereby the influence of the interface on the ac breakdown strength of epoxy nanocomposites. It was also observed that the decrease in ac electric breakdown strength with an increase in sample thickness follows an inverse power-law dependence. In addition, the ac breakdown strength of epoxy silica nanocomposites have also been studied in order to understand the influence of the filler type on the breakdown strength. View full abstract»

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  • A new potential barrier model in epoxy resin nanodielectrics

    Page(s): 1535 - 1543
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    The dielectric constant and the conductivity of epoxy resin nanocomposites exhibit a lower value at slight filler loading compared with the host epoxy resin. The electrical strength has an increase and presents an optimal value at filler loading of 1 wt%. The interaction zone between the nanoparticles and the polymeric matrix is considered as an independent region. Accordingly, a new potential barrier model is proposed. Based on the model, carriers are restrained in the interaction zone when nanoparticle is in an isolated dispersion, leading to a decrease in both mobility and density of carriers. As a result, the conductivity decrease and the electrical strength increase. The restriction of dipole movement in the interaction zone and the increase of free volume are collectively contributed to the reduction of the dielectric constant. With increasing filler loading, the thickness of the interaction zone extends due to the overlap of the interaction zone, even a conductive path occurs when filler loading exceeds the percolation threshold, leading to a great increase in both mobility and density of carriers. Consequently, the conductivity increase and the electrical strength decrease. The increase of the dielectric constant is chiefly ascribed to the particles. View full abstract»

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  • The measurement of very low conductivity and dielectric loss in XLPE cables: a possible method to detect degradation due to thermal aging

    Page(s): 1544 - 1553
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    The dielectric response of crosslinked polyethylene (XLPE) insulated, miniature power cables, extruded with inner and outer semicons, was measured over the frequency range 10-4 to 104 Hz at temperatures from 20 to 100 °C. A dielectric spectrometer was used for the frequency range 10-4 to 10-2 Hz. A bespoke noise-free power supply was constructed and used to measure the dc conductivity and, using a Fourier transform technique, it was also used to measure the very low dielectric tanδ losses encountered at frequencies of 1 to 100 Hz. Tanδ measurements of <;10-5 were found in this frequency range and attributed to a β-mode dielectric relaxation lying above 100 Hz due to motion of chain segments in the amorphous region and an β-mode relaxation lying below 1 Hz window due to twists of chains in the crystal lamellae. The dc conductivity measurements were consistent with those of the dielectric spectrometer and indicate lower dc conductivities in vacuum degassed cables than have been previously reported for XLPE (less than 10-17 S.m-1). The conduction process is thermally activated with an activation energy of approximately 1.1 eV. Higher conductivities were found for non-degassed cables. A transformer ratio bridge was used for measurements in the range 1 to 10 kHz; loss in this region was shown to be due to the series resistance of the semicon layers. Thermal ageing of the cables at 135 °C for 60 days caused significant increases in the conductivity and tanδ and it is considered that such measurements may be a sensitive way of measuring electrical degradation due to thermal aging. View full abstract»

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Aims & Scope

IEEE Transactions on Dielectrics and Electrical Insulation contains topics concerned with dielectric phenomena and measurements with development and characterization of gaseous, vacuum, liquid and solid electrical insulating materials and systems.

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Editor-in-Chief
Reuben Hackam