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Dielectrics and Electrical Insulation, IEEE Transactions on

Issue 5 • Date Oct. 2004

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Displaying Results 1 - 23 of 23
  • Impact of corona on the long-term performance of nonceramic insulators

    Page(s): 913 - 915
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    This work discusses with the impact of corona on the long-term performance of nonceramic insulators. The aging mechanism of insulating materials and the partial discharges measurement (PD) on insulating materials is also discussed. In this measurement the rise of surface temperature of some solid insulating materials during activity of corona in point-dielectric-plain electrode arrangement by means of noncontact infrared (IR) measuring system. As the method measures the mean temperature of the sample surface, it is important to keep the diameter of the measuring target, in a given electrode arrangement, as small as possible. The smallest spot diameter of the sensor was 2.5 mm. The measurements made in the same electrode arrangements but with another IR camera proved that the spot diameter is even smaller than 2.5 mm. It means that the actual surface temperature is higher than indicated one. View full abstract»

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  • Modification of electrical properties and performance of EVA and PP insulation through nanostructure by organophilic silicates

    Page(s): 754 - 762
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1778 KB) |  | HTML iconHTML  

    Nanostructured materials are attracting increased interest and applications. Exciting perspectives may be offered by electrical insulation. Polymeric nanofilled materials may find new and/or upgraded applications in the electrical and electronic industry, replacing conventional insulation to provide improved performances in electrical apparatus, as regards, e.g., reliability, environmental compatibility and power rating. This paper shows that electrical properties of nanocomposite insulating materials for DC applications, specifically space charge, conductivity and breakdown voltage, can improve significantly with respect to the basis, unfilled materials. Reference is made to two polymeric materials, i.e. poly(ethylene-covinylacetate) (EVA) and polypropylene (PP), that are widely used as electrical insulation, e.g. for cables and capacitors. The nanofiller consists of an organophilic layered silicate, specifically an extra-pure synthetic fluorohectorite modified by means of interlayer exchange of sodium cations for protonated octadecylamine NH3+ (ODA), in a weight concentration of maximum 6%. In both materials the space charge accumulation rate as a function of applied electric field is significantly reduced, while the electrical conductivity is raised. The breakdown voltage can increase for the nanofilled materials. View full abstract»

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  • Polymer nanocomposites as dielectrics and electrical insulation-perspectives for processing technologies, material characterization and future applications

    Page(s): 763 - 784
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1799 KB) |  | HTML iconHTML  

    Polymer nanocomposites are defined as polymers in which small amounts of nanometer size fillers are homogeneously dispersed by only several weight percentages. Addition of just a few weight percent of the nanofillers has profound impact on the physical, chemical, mechanical and electrical properties of polymers. Such change is often favorable for engineering purpose. This nanocomposite technology has emerged from the field of engineering plastics, and potentially expanded its application to structural materials, coatings, and packaging to medical/biomedical products, and electronic and photonic devices. Recently these 'hi-tech' materials with excellent properties have begun to attract research people in the field of dielectrics and electrical insulation. Since new properties are brought about from the interactions of nanofillers with polymer matrices, mesoscopic properties are expected to come out, which would be interesting to both scientists and engineers. Improved characteristics are. expected as dielectrics and electrical insulation. Several interesting results to indicate the foreseeable future have been revealed, some of which are described on materials and processing in the paper together with basic concepts and future direction. View full abstract»

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  • Electrical properties and morphology of polyethylene produced with a novel catalyst

    Page(s): 881 - 890
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3817 KB) |  | HTML iconHTML  

    In this paper electrical properties of a novel linear low-density polyethylene synthesized with a catalyst, developed by our unique technique, were measured. It was found that this polyethylene had a higher volume resistivity, a higher breakdown strength and less spacer charge accumulation than conventional high-pressure low-density polyethylene and linear low-density polyethylene. We also measured electrical properties of blends of the new polyethylene and the conventional low-density polyethylene and found that the blends which contained up to 90 wt% of the low-density polyethylene had nearly the same value as the new polyethylene. The morphologies of the polyethylene were observed by using transmission electron microscope (TEM) and found that the blends kept the characteristics shown in the new polyethylene up to 90 wt% of the low-density polyethylene content. The relationship between morphology and electrical properties is discussed and comparison is made between the new polyethylene with those of the conventional low-density polyethylenes. View full abstract»

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  • Monolayer dielectrics and generation of Maxwell-displacement current and optical second harmonics

    Page(s): 785 - 796
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (992 KB) |  | HTML iconHTML  

    Optical second harmonic generation (SHG) and Maxwell displacement current (MDC) spectroscopy for the exploration of the dielectric polarization phenomena in organic monolayer film are described. It is shown that MDC and SHG are generated from the monolayers due to their noncentrosymmetric structure; the spontaneous polarization and the nonlinear polarization are the main contributions to the MDC and SHG, respectively. The developed MDC measurement coupled with the SHG measurement are shown to be helpful for the study of the orientation order and the phase transition of the monolayers, and thus helpful for the understanding of surface polarization phenomena. In order to show the effect of the SHG-MDC spectroscopy, the dielectric polarization of organic monolayer with C-symmetry is theoretically analyzed with a simple rod-like model. The spontaneous and nonlinear polarization induced in this modeled monolayer system is expressed in orientational order parameters defined by the thermodynamic averages of Legendre polynomials of the orientation angle. The experiments on the SHG and MDCs of mesogenic liquid crystal (LC) monolayers of 4'n-octyl-4-cyanobiphenyl (8CB) on the air-water interface are shown. Finally, piezoelectric effect and flexoelectric effect in monolayers are briefly discussed. View full abstract»

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  • Interfaces are the dominant feature of dielectrics at the nanometric level

    Page(s): 739 - 753
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1179 KB) |  | HTML iconHTML  

    It is argued that the behavior of dielectric particles as they shrink in size through micrometric to nanometric scales will be increasingly dominated by the properties of their interfaces with the environment. The various interatomic and intermolecular forces that determine the structure of these interfaces are reviewed with special emphasis on their electrical nature. A number of situations in which passive and dynamic dielectric properties are traceable to nanometric interfacial properties are considered. It is also demonstrated that such interfaces are nanometric electromechanical (NEM) systems which acting collectively also explain piezoelectricity in macroscopic systems. Interfaces are naturally nanometric entities and must have a major role in the future development of nanotechnology. Their ubiquitous employment in living systems is noted and comparison suggests synergistic opportunities. View full abstract»

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  • Environmental factors affecting DC resistance to tracking of polyethylene

    Page(s): 911 - 912
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (193 KB) |  | HTML iconHTML  

    This paper discusses the environmental factors affecting DC resistance to tracking of polyethylene. The voltage, as determined under the conditions specified in the following, which will cause failure with the application of 50 drops of electrolyte, is used as a measure of the susceptibility of the material to tracking, it is called the CTI (contaminant tracking index). A tracking test was set up to investigate dc and ac tracking resistance of epoxy resin, phenolic resin and polycarbonate by IEC 112. The test solution was with 0.1 % ammonium chloride NH4Cl in deionized water, giving a resistivity of approximately 4Ωm at 23°C. A droplet was applied at intervals to keep up the discharge between the two electrodes. Epoxy and phenolic resins are tracking type materials. View full abstract»

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  • Analytical processing of online monitored dissipation factor based on morphological filter

    Page(s): 840 - 846
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (530 KB) |  | HTML iconHTML  

    Analyzing the trend of the on-line monitored dielectric dissipation factor (tan δ) series is a very effective method to diagnose the insulation fault of high voltage apparatus. However, due to the influence of environmental temperature, humidity and field noise interference, etc., the series is too nonstationary to observe its trend directly. In this paper, the problem of a trend-extracting method through relative comparison is briefly pointed out. Based on the analysis of the regularity of the practical tan δ series, a trend model of the series is then built. Since the variation regularity of the real insulation condition is different from that of all influential factors, another trend-extracting method by using the filter is put forward. The morphological filter is introduced to extract the trend of the tan δ series. To verify the effectiveness of the morphological filter, the median filter and wavelet transform are employed to process a simulated tan δ series. The results by the morphological filter are more stationary and smoother than those obtained by other methods. Finally, morphological filters with the structure element in different width are employed to analyze a practical tan δ series. The results show that the influences of different factors can be effectively removed. View full abstract»

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  • Dielectrics and nanotechnology

    Page(s): 737 - 738
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    First Page of the Article
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  • The future of nanodielectrics in the electrical power industry

    Page(s): 797 - 807
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2011 KB) |  | HTML iconHTML  

    While specialty applications of nanotechnology in the photonics and electronics areas have seen a tremendous growth in the past several years, the use of nanodielectrics in the electrical industry (high power density and high voltage) has not shown the same level of activity. In addition to a review of nanodielectrics, we discuss in this paper, our perspective on the current status, development needs and future potential to build or engineer nanostructured materials for dielectric applications in the electrical power industry. Short and long-term future research and development needs are considered from the point of view of industrial applications. View full abstract»

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  • Fluid circulation in an enclosure generated by electrohydrodynamic conduction phenomenon

    Page(s): 899 - 910
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    Fluid circulation/mixing inside an enclosure, nonmechanically, is of significant importance in various applications. This study investigates, theoretically, the circulation of an isothermal dielectric liquid 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. The EHD induced flow, based on the conduction phenomenon, is associated with the process of dissociation of the neutral electrolytic species and recombination of the generated ions. The charges generated by dissociation are redistributed in the region by the applied electric field resulting in heterocharge layers in the immediate vicinity of the electrodes. The Coulombic attraction between a given electrode and the charges within the corresponding heterocharge layer induces a fluid motion near that electrode. With a proper electrode design, a significant flow circulation/mixing can be achieved within an enclosure based on the conduction phenomenon. View full abstract»

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  • Insulator surface charge accumulation under impulse voltage

    Page(s): 847 - 854
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    The surface charge distribution under impulse voltage is measured using a static capacitance probe. A probe with very small charge leakage is designed. The condition of surface charge accumulation under impulse voltage is analyzed, and it is concluded that micro discharges in the gas near the insulator surface such as the corona caused by free and fixed metal particles is usually a prerequisite condition. The dynamic equation describing the relationship between surface charge density and the applied voltage is established, and the process of surface charge accumulation under impulse voltage is analyzed. Theoretical analysis and experimental results show that the decrease of wave front time of the impulse voltage can result in an increase of surface charge accumulation. A GIS spacer is used to investigate the influence of charge accumulation on the flashover characteristics. It is shown that the 50% impulse flashover voltage can be reduced by 23.4%, and the lower limit of the V-t characteristics can be lowered drastically if the polarity of the surface charge is opposite to that of the applied voltage. View full abstract»

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  • Pulsed electro-acoustic technique applied to in-situ measurement of charge distribution in electron-irradiated polymers

    Page(s): 891 - 898
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    Dielectric materials are frequently used in satellite structures for substantial savings in weight. Their dielectric nature and the effect of different forms of radiation encountered in space combine to accumulate electrical charges resulting in the occurrence of electrostatic discharges which cause harmful interference with the electronic parts of the satellite, leading to its malfunction or to a total loss of equipment control. Therefore, the behavior of dielectrics under irradiation must be investigated before being used in space. A pulsed electroacoustic (PEA) device was mounted in an irradiation chamber to monitor the spatial distribution of electrons implanted into polymer films during electronic irradiation. Internal charge accumulation was clearly identified. Penetration depth versus energy was double checked by comparing PEA with surface potential data. View full abstract»

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  • Introductory remarks on nanodielectrics

    Page(s): 808 - 818
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    The neologism nanotechnology exists today and is attracting a considerable amount of interest and activity. It is complex in nature with multiple ramifications. It has a vast scope and in fact includes older as well as newer concepts. At this point in time, a greater focus on the field status and impact on new materials, especially dielectrics and their insulating properties, would certainly be desirable. A personal view is thus being presented here, with a tentative definition of the concept of nanodielectrics being offered at the end. View full abstract»

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  • Electrical performance of ice-covered insulators at high altitudes

    Page(s): 870 - 880
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1679 KB) |  | HTML iconHTML  

    This paper presents results on the flashover of ice-covered insulators at low air pressure. The flashover performance of two different types of insulators covered with polluted ice was experimentally determined and the effects of several determining factors, such as the air pressure, ice severity, and pollution rate, were discussed. Based on the laboratory investigations, a mathematical model for predicting the critical flashover voltage of ice-covered insulators at low air pressure was established. There is optimal agreement between the calculated and experimental results. View full abstract»

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  • Partial discharge on-line monitoring for HV cable systems using electro-optic modulators

    Page(s): 861 - 869
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1115 KB) |  | HTML iconHTML  

    A technique for the remote inspection and monitoring of partial discharge (PD) activity using an optical network is described. The network uses a LiNbO3, modulator to modulate the intensity of the transmitted laser light approximately proportional to the voltage applied across the modulator. The laser light is transmitted along an optical fibre and measured remotely by a high-speed optical receiver. A capacitive coupler has been used to detect partial discharge activity and act as the modulator's input voltage source. The electro-optic modulator is passive and does not require a power supply at the site of the PD detection sensor. The system has the additional advantages of being immune to electromagnetic interference, having very little signal transmission attenuation, with good sensitivity, compact size, as well as being convenient to use and safe. Both simulation experiments and practical PD tests on two cable systems have indicated that the optical system provides a feasible remote PD monitoring technique for high voltage cable systems. View full abstract»

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  • Surface degradation of polyamide nanocomposites caused by partial discharges using IEC (b) electrodes

    Page(s): 833 - 839
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    Partial discharge (PD) degradation of polyamide both without nanoscale fillers (nanofillers) and with 2,4 and 5 wt% additions of nanofillers was investigated. Such materials were subjected to PDs using the IEC (b) electrodes for evaluation. Comparisons were made as to the surface roughness observed by scanning electron microscopy and atomic force microscopy. It was found that the change in the surface roughness is far smaller in specimens with nanofillers than those without nanofillers, and that the 2 wt% addition is sufficient for improvement of the surface roughness. Furthermore, it was elucidated that the difference of surface roughness of the degraded area due to PDs among the specimens originates from the difference in their crystalline structures. These results indicate that polyamide nanocomposite is more resistance to PDs than polyamide without nanofillers. View full abstract»

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  • Effective permittivity of nanocomposite powder compacts

    Page(s): 819 - 832
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    Advances in nanotechnology have led to a variety of new materials with strong potential applications to microwave and millimeter-wave components, e.g. dispersions of nanoscale particles, nanoparticle-filled polymers, self-assembled nanolattices of magnetic particles. More specifically, the properties of nanocomposites can be tailored for operation as insulators, ferro- and ferrimagnetic materials, highly conductive materials as well, for specific applications. In this study, we have investigated the electromagnetic response at microwave frequencies, using frequency domain network analysis, of cold-pressed powder compacts made of Ni, γ-Fe2O3, Co, and ZnO nanosized powders. Effective complex permittivities of composites over the frequency range (100 MHz-10 GHz) as a function of composition were studied. Within the frequency range of measurements the real and imaginary parts of the effective permittivity of nanocomposites exhibit spectra which can be analytically well represented by power laws. The associated power law exponents, which are similar for the real and imaginary parts of the permittivity, are in the range 0.05-0.20 in agreement with data in the published literature. The dependences of the effective permittivity vs. composition are compared to those obtained from the effective medium theory of Bruggeman, which is found not to be adequate for all nanocomposites studied. View full abstract»

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  • Assessment of dielectric behavior of recycled/virgin high density polyethylene blends

    Page(s): 855 - 860
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (473 KB) |  | HTML iconHTML  

    In this work, high density polyethylene (HDPE) incorporation in virgin resin was assessed as to its electrical performance with the use of volumetric resistivity, dielectric strength, and stress tracking measurements. HDPE post-consumer packaging was collected and submitted to a basic process of plastic recovering: washing, grinding, and drying. Formulations containing 0, 25, 50, 75, and 100% of recycled material in the virgin resin were reprocessed by extrusion and injection molding with stabilization. Dielectric strength test results were analyzed by the statistical distribution of Weibull, and the maximum likelihood method. The degree of crystallinity was measured by X-ray diffraction. Atomic absorption spectroscopy was also done to identify metallic residue present in the samples. From the results analyzed, it can be concluded that the HDPE derived from post-consumer packaging can be considered in electrical insulation systems for low voltage (up to 600 V) containing as much as 75% incorporated virgin resin. View full abstract»

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  • [Front cover - Conference on Electrical Insulation and Dielectric Phenomena Digest of Literature on Dielectrics]

    Page(s): 01
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    Freely Available from IEEE
  • IEEE Dielectrics and Electrical Insulation Society

    Page(s): 2
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    Freely Available from IEEE
  • IEEE Dielectrics and Electrical Insulation Society

    Page(s): 916
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    Freely Available from IEEE
  • CEIDP - Conference on Electrical Insulation and Dielectric Phenomena

    Page(s): 917
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    Freely Available from IEEE

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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Reuben Hackam