By Topic

Dielectrics and Electrical Insulation, IEEE Transactions on

Issue 6 • Date Dec. 1996

Filter Results

Displaying Results 1 - 21 of 21
  • Author Index 1996

    Publication Year: 1996 , Page(s): 867 - 872
    Save to Project icon | Request Permissions | PDF file iconPDF (678 KB)  
    Freely Available from IEEE
  • Subject index 1996

    Publication Year: 1996 , Page(s): 874 - 887
    Save to Project icon | Request Permissions | PDF file iconPDF (1330 KB)  
    Freely Available from IEEE
  • Evidence of strong correlation between space-charge buildup and breakdown in cable insulation

    Publication Year: 1996 , Page(s): 778 - 783
    Cited by:  Papers (62)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    Many processes have been considered over the years to explain the origin of breakdown in cable insulation. Such effects as space charge build-up, tree growth, charge injection, etc. have all been discussed. Various techniques are now available to measure, in a nondestructive way, space charge distributions in insulators. These techniques, for instance the pressure wave propagation (PWP) method, can be used under applied electric stress and thus make it possible to follow the development of space charge in selected regions of the insulators. In this paper we present new evidence linking space charge buildup, tree growth and breakdown in XLPE. We have used the PWP method to monitor the charge distribution as a function of time under dc stress in high insulating thickness cable. We show that for certain insulation systems the space charge buildup can increases the local field to a value which is more than 8× the applied electric field, leading to breakdown. Post-mortem analysis followed by optical microscopy shows the presence of electrical trees, the breakdown channel being centered on one of them. The study of space charge evolution in practical insulations permits an understanding of the role of space charge in dc breakdowns. This understanding enables the development of technologies to suppress this effect and hence realize practical dc XLPE transmission cables View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The breakdown mechanism of a mid-plane triggered spark gap trigatron

    Publication Year: 1996 , Page(s): 843 - 848
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    A mid-plane triggered spark gap trigatron prototype with adjustable main gap distance and replaceable trigger electrode was constructed and experimentally investigated. The electric parameter measurements, the luminosity measurements and the streak image converter camera were used to study the breakdown mechanism. Electric field distribution in the gap was calculated for the trigatron static and dynamic conditions. The experimental results and analysis show that the space charge around the trigger electrode plays an important role in the breakdown process. Because of the ultra violet irradiation and the existing discharge channel of the first gap segment breakdown, the second gap segment breakdown is much faster. For a mid-plane triggered spark gap trigatron, the optimization of the electric field distribution under dynamic condition can increase the dynamic triggering range appreciably View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The influence of crystalline morphology on the growth of water trees in PE

    Publication Year: 1996 , Page(s): 849 - 858
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1612 KB)  

    A small amount of phenolphthalein, acting as a nucleating agent, was added to low density polyethylene (LDPE) to modify the size and number of spherulites. The crystalline morphology was observed and analyzed with the aid of a chemical etching method. It was found that the growth of water trees is faster in LDPE samples in which spherulites are larger and the number of the spherulites is lower. In contrast, water trees grow more slowly in other LDPE samples in which spherulites are smaller in size and greater in number. On the other hand, three different kinds of additives, weak electrolyte and hydrophilic or hydrophobic substances, were added to the LDPE materials to investigate the influence of typical spherulite boundary regions on the growth of water trees. It was verified experimentally that during the process of crystallization, these three different additives are rejected and finally settled near the spherulite boundaries. Therefore, three kinds of boundary regions with different characteristics are formed. It has been concluded that hydrophillic boundary regions can strongly inhibit the growth of water trees, while the other two boundary regions (weak electrolyte, hydrophobic) have little influence on the water tree growth View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Space charge evolution in dilute binary electrolytes exposed to HV transients

    Publication Year: 1996 , Page(s): 747 - 753
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    Dilute solutions of KCl were investigated with HV transients to determine the effects of electrode reactions on the voltage-current relationship. The resistance seen by the external circuit under transient conditions was a function of bulk conduction processes and space charge near the electrodes. The bulk conductivity of KCl, described by a set of coupled first order differential equations, was reduced to a thermally varying conductivity model. The variation of conductivity with temperature was small enough that space charge effects could be measured. A forced diffusion model was developed to describe the electrode processes with an applied transient voltage and constant temperature View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electrical performance of non-ceramic insulators in artificial contamination tests. Role of resting time

    Publication Year: 1996 , Page(s): 827 - 835
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1148 KB)  

    The paper presents the results of an investigation on the electrical performance of artificially contaminated non-ceramic insulators as a function of resting time. Resting time is defined as the time interval between the application of contamination and start of testing. New (unaged), full scale, 69 kV non-ceramic insulators using different types of silicone rubber and ethylene propylene diene monomer (EPDM) rubber as weathersheds were studied. Their electrical performance was assessed using the clean fog technique. The applied voltage was kept constant throughout the test, while contamination severity and resting time were varied as parameters. The transfer of hydrophobicity through the contamination layer was demonstrated by flashover tests. This was also visually depicted by analyzing samples in a scanning electron microscope. The results show that resting time exerts little influence on the electrical performance of EPDM insulators. However, for silicone rubber insulators, resting time is shown to drastically improve its electrical performance. Experimental evidence indicates that the transfer or recovery process of hydrophobicity in silicone rubber insulators occurs as a progressive superposition of silicone oil layers with time. Thus, the net effect of resting such insulators before tests can be thought of as a gradual reduction of the effective contamination layer thickness. Such a reduction alters the way in which the contaminant layer interacts with external stressing agents, which could impact the insulator's electrical performance in service. In this work, an attempt has been made to identify and quantify the electrically significant changes introduced by a reduction in the effective contamination thickness. It is in the light of this reduced effective contamination layer that we explain how a seemingly wettable silicone rubber insulator is still able to hold the applied voltage without flashover View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Properties of streamers in transformer oil

    Publication Year: 1996 , Page(s): 784 - 791
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    The electrical characteristics of creeping discharges and single creeping streamers in transformer oil first are compared with those of streamers developing in the liquid bulk. The distribution of electric potential along the channel of a single negative creeping streamer is determined using a capacitive probe technique. Then the distribution of the space charge associated with each streamer channel is discussed and the electric field around the channels is estimated. A strong correlation between the mean potential gradient and the capacitance of the streamer channels is found. The different results and considerations tend to support the hypothesis of the same basic physical mechanism for both creeping discharges and streamers developing in the bulk View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermal hysteresis in the permittivity and polarization of lead zirconate titanate/vinylidenefluoride-trifluoroethylene 0-3 composites

    Publication Year: 1996 , Page(s): 800 - 805
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    The permittivities of 70/30 vinylidene fluoride-trifluoroethylene copolymer and lead zirconate titanate/vinylidene fluoride-trifluoroethylene 0-3 composites have been measured at 1 kHz over the temperature range of 20 to 120°C. Thermal hysteresis was observed for the 0-3 composites and abrupt changes in the permittivities occurred at different temperatures upon heating and cooling. Good agreement was found between the measured permittivities and the predictions of the Bruggeman model. Implications of the thermal hysteresis behavior on the poling of 0-3 composites are also discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-resolution PEA charge distribution measurement system

    Publication Year: 1996 , Page(s): 754 - 757
    Cited by:  Papers (54)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The pulsed electroacoustic (PEA) method is widely known to be an excellent method for measuring the space charge distribution that accumulates in thick dielectric materials (1 to 5 mm). We have refined the PEA measurement system for use on thin dielectric materials. With FFT deconvolution to compensate for the frequency characteristics of the piezoelectric sensor, the resolution in the depth direction is improved to ~3 μm. This improved system is thus expected to be useful for the quantitative and nondestructive measurement of the space charge distribution in dielectric films View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Inference of sampling on Weibull representation

    Publication Year: 1996 , Page(s): 806 - 808
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    An easy-to-code algorithm is provided to draw on a Weibull graph the percentile ranges strictly related with the scatter due to sampling View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Prediction of breakdown in SF6 under impulse conditions

    Publication Year: 1996 , Page(s): 836 - 842
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    Prediction of fast transient voltage-induced breakdown in quasi-homogeneous field geometries requires compounding the breakdown probability over time, while taking into account the field-dependent probability of electron detachment. In this paper, a breakdown probability model has been developed to predict the impulse breakdown under quasi-uniform fields, as this is the fundamental condition, the knowledge of which facilitates computation of breakdown probability under more complex conditions. The model will facilitate computation of breakdown probability under more complex conditions. It accounts for the effect of the streamer formation length on the critical volume and the probability of initial electron production by electron detachment from negative ions. The proposed model has been verified through comparison with the measured impulse breakdown probabilities. The predicted breakdown probabilities are in good agreement (±10%) with those measured View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electrical salt-fog performance of XLPE insulation with different levels of CaCO3

    Publication Year: 1996 , Page(s): 817 - 826
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1588 KB)  

    This paper presents a study of the electrical performance of crosslinked polyethylene (XLPE) in salt fog conditions. Specimens of XLPE having 0, 15 and 25% calcium carbonate (CaCO3) filler, a fixed concentration of 2% carbon black and an additional ultraviolet stabilizer were used. The leakage current and the current pulse counts were monitored as a function of time of exposure to combined electrical stress and salt-fog. Both leakage current and current pulse count were found to increase with increasing test time and with increasing filler concentration. The time to failure of the specimens as a function of the filler concentration was found to increase with increasing filler level. The contact angle decreased, and the surface roughness increased with increasing test time in energized salt fog. A SEM study showed that the surface roughness increased with increasing filler levels, giving an independent confirmation of the results obtained from the surface roughness tester. The EDAX study showed that the intensity count of X-ray of calcium on the surface increased after salt-fog test, indicating that CaCO3 was not removed from the surface. Both the SEM and EDAX studies confirmed that the number of CaCO3 particles on the surface increased with increasing filler level. It is suggested this was responsible for the observed larger roughness of the surface, higher resistance to arcing erosion and longer lifetime of XLPE polymer with increasing level of CaCO3 filler View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Pyroelectric properties of linear aromatic polyurethanes

    Publication Year: 1996 , Page(s): 765 - 769
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Two types of aromatic polyurethanes, poly(hexamethylene phenyl dicarbamate) (PUH6) and poly(heptamethylene biphenylene dicarbamate) (PUB7) have been synthesized by the polycondensation method. Structural, pyroelectric and dielectric properties of these polyurethanes were studied. The pyroelectric activity was studied in the temperature range from room temperature to 120°C for poled samples of both polyurethanes. The temperature dependence of the pyroelectric constant of both polyurethanes vanished around their glass transition temperatures. The experimental results given in this paper suggest that the pyroelectric behavior is possibly attributed to orientation of the urethane dipole in the amorphous phase. The pyroelectric coefficients obtained are 13 and 15 μm-2K-1 for the PUH6 and PUB7 samples, respectively View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of BaTiO3 additive and electrode material on space-charge formation in polyethylene. Evidence from thermal step space-charge measurements

    Publication Year: 1996 , Page(s): 743 - 746
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The effects of 5% wt BaTiO3 additive and of electrode material on space charge formation and electric field distribution in low density polyethylene (LDPE) were investigated using a thermal step technique. Space charge was formed at an average dc field of ~28 kV/mm and at 50°C. Results indicate that the addition of BaTiO3 to LDPE has considerably reduced the remanent space charge and electric field and changed their distribution patterns in the doped material when compared with the plain material. It is also shown that the remanent space charge and electric field in plain LDPE are strongly dependent on the type of electrode material View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The effect of field-enhanced injection and dissociation on the conduction of highly-insulating liquids

    Publication Year: 1996 , Page(s): 792 - 799
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    A generalization of the Thomson model to include field-enhanced dissociation in the bulk (the Onsager effect) and unipolar charge injection, without recombination between electrolytic and injected ions, is formulated for nonpolar dielectric liquids. In the case of an autonomous injection of charge, approximate analytical solutions are given for the dissociation and the injection current densities. A comparison with the “exact” numerical solution is done to determine the regions of validity of the approximate solutions. The general case of field-enhanced dissociation and nonautonomous injection also is investigated numerically View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Using the λ function to evaluate probe measurements of charged dielectric surfaces

    Publication Year: 1996 , Page(s): 770 - 777
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    The use of Pedersen's λ function to evaluate electrostatic probe measurements of charged dielectric surfaces is demonstrated. With a knowledge of the probe λ function, the procedure by which this function is employed is developed, and thereafter applied to a set of experimental measurements available in the literature. The values of surface charge density derived are in good agreement with the published data. Through this field-theoretical approach, it is readily shown that areas of charge remote from the probe location can produce a major part of the probe signal. If a circuit-theory approach were adopted to analyze such probe measurements, then as the held features of the probe response cannot be taken into account, a serious misinterpretation of the measurements could arise View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spectral features of the luminescence of PE subjected to various excitation sources

    Publication Year: 1996 , Page(s): 859 - 865
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (652 KB)  

    Electroluminescence (EL) of insulating polymers is now recognized as a warning sign for electrical aging. In order to further understand the emission process, we have compared the luminescence spectra of the same material when the emitting states are created by different excitation sources. Additive free and carbonyl containing low density polyethylene films were used. Light emission was stimulated by photon irradiation in the ultraviolet range (photoluminescence), by the interaction between a cold plasma and the polymer surface leading to a post-discharge emission (plasma induced luminescence), and by the electric field in the absence of any gaseous discharge (EL). Plasma induced luminescence and electroluminescence exhibit similar spectral features in the wavelength range between 500 and 650 nm. It is concluded that the same kind of chromophores is involved in both processes. They could be conjugated groups acting as recombination centers because charges are selectively trapped on these groups. This explains why photoluminescence does not show similar emission features since all the material chromophores are excited upon UV irradiation. Moreover, it is shown that the EL-features are sensitive to structural relaxation of the polymer probably through the interaction between emitting species and the surrounding molecules View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interfacial charge in polyethylene/ethylene vinylacetate laminates

    Publication Year: 1996 , Page(s): 758 - 764
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Space charge formation in polyethylene (PE)/ethylene vinylacetate copolymer (EVA) laminates has been investigated using a pulsed electroacoustic method. The PE shows heterocharge while the EVA shows a broad distribution of positive charge over the sample. The positive charge in EVA decreases with the increase of vinylacetate (VA) content in EVA. Interfacial charge is found in all laminates and remains unchanged by heat treatment at 100°C to 1 h and by coating chemicals such as silicone oil and trimethylolpropane trimethacrylate at the interfaces, This interfacial charge distorts the electric field distribution in the direction of increasing the electric field in the PE layers. The charge distribution in PE/EVA blends has been measured and is explained via the results obtained with the laminates View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Inference of sampling on Weibull parameter estimation

    Publication Year: 1996 , Page(s): 809 - 816
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    The data usable to evaluate the confidence bounds for the Weibull parameter estimates is provided in broad range of values, in the cases of the “mean squares”, “maximum likelihood” and “generalized maximum likelihood” methods. The way to use these results in practice are described in detail. The results are provided in the form of extended Tables for standard use, and in addition in the form of empirical formulae for easy use in computer programs. The extended tabular data also are available on line in the TDEI World wide web pages View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimization of HV electrode systems by neural networks using a new learning method

    Publication Year: 1996 , Page(s): 737 - 742
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    To avoid a large number of iterations, optimization of electrode shapes has been done by artificial neural networks (NN). Two practical examples have been considered, an axisymmetric single-phase GIS bus termination and an axisymmetric transformer shield ring. The shape of the electrodes has been taken as quarter-ellipse or half-ellipse because an ellipse has more flexibility than a circle. For NN, the so-called resilient propagation algorithm, learning faster than the standard back-propagation algorithm, has been employed. The training sets as well as the test sets of NN have been prepared by charge simulation method View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Reuben Hackam