By Topic

Dielectrics and Electrical Insulation, IEEE Transactions on

Issue 6 • Date Dec. 2001

Filter Results

Displaying Results 1 - 25 of 37
  • A self-organizing fuzzy inference system for electric field optimization of HV electrode systems

    Publication Year: 2001 , Page(s): 995 - 1002
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB) |  | HTML iconHTML  

    Development of efficient methods for optimum design of electrode and insulator contour in a HV apparatus has been an important area of research in the recent past. A self-organizing fuzzy inference system is developed for electrode optimization which is an improved version over traditional iterative approach of optimization and more recent methods employing neural networks. This fuzzy system has been implemented for two practical examples of an axisymmetric single-phase gas-insulated system (GIS) bus termination and a disconnecter switch configuration. Improved electric stress distribution demonstrates the usefulness of the proposed method. A new methodology for automatic generation of the fuzzy rule base from the input-output data set is also proposed in this scheme. This fuzzy system is much simpler and less time consuming to implement compared to other optimization techniques presently available for optimization of HV electrodes. View full abstract»

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

    Publication Year: 2001 , Page(s): 1116 - 1126
    Save to Project icon | Request Permissions | PDF file iconPDF (980 KB)  
    Freely Available from IEEE
  • Subject index

    Publication Year: 2001 , Page(s): 1127 - 1146
    Save to Project icon | Request Permissions | PDF file iconPDF (1898 KB)  
    Freely Available from IEEE
  • Electric field behavior near a contact point in the presence of volume conductivity

    Publication Year: 2001 , Page(s): 930 - 935
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (447 KB) |  | HTML iconHTML  

    The electric field behavior, in particular the field intensification at a contact point, is very important in complex dielectric systems with gaseous or vacuum insulation. The paper describes the electric field behavior at and near a contact point in various arrangements with a zero contact angle when volume conductivity is present in the solid dielectric. Contact conditions are separated into line, point, and surface contact. The effect of volume conductivity is investigated analytically, and numerically by using the boundary element method. The electric field behavior near a contact point principally depends on the absolute value of complex relative permittivity, and volume conductivity usually promotes the field intensification. In the arrangements of point contact or line contact, the position of peak electric field shifts from a contact point when the volume conductivity is higher than a certain value, while in the arrangement of surface contact, the position is usually more or less remote from the contact point, whether volume conductivity is present or not View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electric field criteria for charge packet formation and movement in XLPE

    Publication Year: 2001 , Page(s): 859 - 866
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (767 KB) |  | HTML iconHTML  

    The formation of space charge packets in crosslinked polyethylene (XLPE) tapes from un-aged cable insulation has been studied utilizing the pulsed electroacoustic (PEA) technique. The 150 μm thick sheets were studied under constant applied DC field of 120 kV/mm at a temperature of 20°C for a period of 48 h. After an inception period of ~3.5 h, during which heterocharge accumulates at the anode and increases the local field there, a sequence of positive charge packets was observed to transit the sample starting from near the anode. Calculation of the internal field showed that the packets required a field of ⩾140 kV/mm for their initiation. Reduction of the applied field step-wise from 120 to 80 kV/mm indicated that the charge packet would keep moving as long as the local field at its front was >100 kv/mm, but with a reducing magnitude. A return to an applied field of 120 kV/mm confirmed that the local field required to initiate a new packet was >135 kV/mm. The results are discussed in terms of current theories of charge packet formation. The first packet appears to be a moving front of field ionization. The generation of subsequent packets is governed by the field at the anode and the balance of charge injection and extraction process, which occur there. The nature of the negative charges produced at the ionization front is not clear, but they are unlikely to be electrons View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electrodes and charge injection in low-density polyethylene using the pulsed electroacoustic technique

    Publication Year: 2001 , Page(s): 867 - 873
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (969 KB) |  | HTML iconHTML  

    The effects of electrode materials on space charge formation in low-density polyethylene (LDPE) have been investigated experimentally using the pulsed electroacoustic (PEA) technique. Common electrode materials used in either the laboratory or power cable industry were selected, i.e. aluminum, gold and carbon loaded crosslinked polyethylene (XLPE), and space charge accumulation after the application of high electric stress was monitored. Experimental results demonstrated that charge injection processes take place in all cases once the applied stress has exceeded a threshold. However the amount of charge, and the polarity of the dominant injected charges showed a significant dependence on the electrode materials under the same applied electric stress View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerically established correlation in electrical responses of polymer film capacitors to ac and pulsed voltages

    Publication Year: 2001 , Page(s): 880 - 888
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (846 KB) |  | HTML iconHTML  

    In this paper, an equivalent circuit model is used to simulate electrical responses of metalized polymer film capacitors to either ac voltage or pulsed voltage stresses, in particular electric field induced on the electrode coating surface and power dissipation within the film capacitor. Electrode segmentation patterns are taken into consideration by means of arrays of interconnected lumped surface resistors, and the film capacitance is modeled by a set of shunt capacitors distributed across the length of the capacitor film. Voltage magnitude and waveform characteristics are studied in great detail for their effects on surface electric field and power dissipation. Through numerical examples, surface electric field and dissipated power induced by one type of external stress (ac or pulsed) at one frequency are shown to correlate with those at a different frequency. Further correlation is also established to relate surface field and dissipated power induced by one type stress (e.g. ac) to those by the other (pulsed), provided the waveform. characteristics of the two different stresses are specifically related. These numerically established correlations can permit significant reduction in development time of metalized film capacitors View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Applying a gas mixture containing c-C4F8 as an insulation medium

    Publication Year: 2001 , Page(s): 1075 - 1081
    Cited by:  Papers (18)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (483 KB) |  | HTML iconHTML  

    This paper studies the possibility of applying a gas mixture containing c-C4F8 in the gas insulation of power equipment. Environmental aspects such as global warming potential, ozone depletion potential, recycling loss and toxicity are discussed. Insulation characteristics of gas mixtures such as c-C4F8/N2, c-C4F8/air, and c-C4F8/CO 2 are examined experimentally under a quasi-homogeneous or an inhomogeneous electric field condition. Most of the characteristics are compared with those of SF6/N2, which is now widely studied as the most plausible alternative to pure SF6 for gas insulation. The experimental results, together with the discussion, suggest that gas mixtures containing c-C4F8 are possible substitutes for SF6 and SF6/N2 View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Study of space charge accumulation in polyolefins submitted to ac stress

    Publication Year: 2001 , Page(s): 972 - 984
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1205 KB) |  | HTML iconHTML  

    The aim of the present study was to follow space charge formation under ac field (50 Hz) in polyolefins. The thermal step method was used, and charge accumulation was observed in crosslinked polyethylene (XLPE), very low density polyethylene (VLDPE), isotactic polypropylene (PP) and a PE /PP copolymer, the temperature varying from 45 to 90°C. It was found that the amount of charge accumulated under ac conditions may reach a maximum value at a given temperature, while the highest space charge was found in the polyolefin with the lowest crystallinity ratio. The conduction current characteristics of XLPE specimens show the existence of traps in the polymer at a level deeper than the potential barrier electrode/dielectric, explaining the accumulation of injected charge in the material. The injection and conduction mechanisms observed were interpreted by Schottky and Poole-Frenkel processes and used to explain the maximum accumulation of charge occurring at certain temperatures View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Changes in ECT and dielectric dissipation factor of insulating oils due to aging in oxygen

    Publication Year: 2001 , Page(s): 1048 - 1053
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (403 KB) |  | HTML iconHTML  

    It is believed that the aging of insulating oils affects the electrostatic charging tendency (ECT) and dielectric dissipation factor (tan δ), but there is little hard evidence. We have investigated changes in ECT and tan δ of insulating oils aged with oxygen at elevated temperature. We found that ECT and tan δ increased with aging time. In some oils aged with a small amount of oxygen, ECT and tan δ increased much more than in other oils aged with a large amount of oxygen. In yet other insulating oils, ECT and tan δ showed a peak and then declined. Moreover, it was found that aged insulating oil close to the peak in tan δ is very unstable. This result suggests that the methods of measurements of tan δ of insulating oil prescribed in International Electrotechnical. Commission (IEC) 60247 and Japanese Industrial Standards (JIS) C2101 may be unsatisfactory. The reason is that since in these methods tan δ is measured at elevated temperature (IEC 60247, 90°C and JIS C2101, 80°C), the quality of the insulating oil, especially aged oil, is changed during the measurement, resulting in an incorrect reading View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comparison of dielectric properties determined from a computational approach and experiment for anisotropic and periodic heterostructures

    Publication Year: 2001 , Page(s): 921 - 929
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (817 KB) |  | HTML iconHTML  

    The physics of heterostructures is among the forefront problems in materials science. Composite materials also are attractive from the point of view of technological applications such as current-limiting thermistors, radar absorbers, and electromagnetic shields, because they exhibit a variety of interesting mechanical, electric and magnetic properties with the advantage of much reduced cost and weight. To quantify the dielectric response of anisotropic and periodic heterostructures, consisting of two-component composites arranged in a regular simple cubic lattice, in the quasistatic approximation we use an exact numerical technique which is based on a boundary integral equations solution of the Laplace equation which is solved by using the field calculation package PHI3D. 'Exact' means that the correct properties are computed for the given microstructure and choice of individual component properties because all internal electric multipole interactions contributing to the polarization of the material medium are taken into account. The main goal of this work was to confront these numerical calculations with experimental data. Measurements of the effective complex permittivity were carried out in samples composed of identical aligned inclusions, in the form of circular cylinders, embedded in a polymer matrix and filled either by de-ionized water or air. We test our numerical data for two specific examples, i.e. the parallel and perpendicular orientation of the electric field vector with respect to the principal axis of the circular cylinders. Of particular importance is that our numerical simulation captures reasonably well the observed trend in the experimental data over a wide range of volume fraction of inclusions. The experimental results roughly indicate a significant decrease in the permittivity in the x-y plane over that of the z axis, for inclusions containing de-ionized water, while no anisotropy effect is found for inclusions With air. However, there are quantitative differences between the experiment and calculations. These differences were tentatively ascribed to limitations in the experimental model, i.e. finite size, and air bubbles due to ill-controlled filling of the cylindrical inclusions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reduction of PD in a void by additives of azobenzoic compound in HDPE insulating material

    Publication Year: 2001 , Page(s): 889 - 896
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (698 KB) |  | HTML iconHTML  

    In order to reduce partial discharges (PD) in a void within an organic insulator, the material of the inner wall of the void was modified by additives, i.e. four types of azobenzo materials: azobenzene, p-nitro-azobenzene, p-amino-azobenzene and nitrobenzene-azo-resorcinol. The voids in the insulator specimens have a cylindrical configuration with a diameter of 1 mm diameter and a height of 100 μm. The materials of the top and bottom surfaces of the cylindrical void are high-density polyethylene (HDPE) with additive, prepared by the solution casting method. The specimen was placed between plane electrodes. It was found that the PD for the specimen with additive was reduced to as low as ~20% of that for the specimen without additive when the applied voltage was near the PD inception. The reduction of PD in the voids was observed for all four kinds of additives. The effective additive concentration was between 0.05 and 0.5% wt. The mechanisms for the reduction in PD were discussed, focusing on two factors: prevention against secondary electron emission from the void wall due to the excitation of the additive, and prevention of electron detachment from the void wall due to the charge traps by the additive, which may play significant roles in the reduction of the PD in the voids View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dielectric windows for UHF partial discharge detection

    Publication Year: 2001 , Page(s): 953 - 958
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (582 KB) |  | HTML iconHTML  

    Increasing the permittivity of the propagation medium inside a hollow tube lowers its cut-off frequency, allowing it to transmit a wider range of signal frequencies. This principle is applied to the design of dielectric windows that can be used to facilitate partial discharge (PD) detection at ultra high frequency (UHF) in a HV metalclad plant such as gas-insulated substation (GIS), power transformers and circuit breakers. External UHF couplers mounted on such windows can be removed or replaced without compromising the integrity of the insulation system. By increasing the signal power level incident on a window-mounted external UHF coupler, higher sensitivity to PD can be achieved. The problem is analyzed using waveguide theory and, using GIS as an example, improvements of ≈6 dB are demonstrated by means of coupler sensitivity measurements and experiments using PD sources View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hydrophobicity estimation of HV polymeric insulating materials. Development of a digital image processing method

    Publication Year: 2001 , Page(s): 1098 - 1107
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1139 KB) |  | HTML iconHTML  

    Image analysis of water drop patterns on an inclined flat polymeric insulator surface has been performed in order to find a simple mathematical function that indicates the level of hydrophobicity of the insulator surface. A simple function, given the acronym average of normalized entropies (ANE), seems to correlate well with hydrophobicity as defined by the Swedish Transmission Research Institute (STRI) hydrophobicity classification. It is a composition of three other functions, viz. the standard deviation, the Shannon information entropy and the 'fraction of small differences'. All these are in turn based on the histogram of horizontal nearest-neighbor pixel differences for a given digital greyscale image of a water drop pattern. ANE is fairly independent of illumination intensity (exposure) as well as total gain and offset in a camera system (linear sensor). The experimental results also indicate that ANE is fairly independent of limited changes in the surface inclination, although this needs further investigation. Some of the various pitfalls associated with the photography of water drop patterns and processing of images are identified, together with possible solutions for avoiding them View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Elemental strain and trapped space charge in thermoelectrical aging of insulating materials. Part 1: Elemental strain under thermo-electrical-mechanical stress

    Publication Year: 2001 , Page(s): 959 - 965
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (665 KB) |  | HTML iconHTML  

    The life model proposed previously by the authors ascribes electrothermal aging to the formation and/or enlargement of nanovoids driven by electromechanical energy stored in local concentrations of space charge. In the previous work, the strain associated with the mechanical stress produced by the space charge center was derived using a macroscopic stress-strain relationship. For chain conformation changes on the molecular scale, these macroscopic concepts may no longer be valid. In this paper, we have investigated the possibility that the local strain is an elemental property of the polymer morphology, as suggested by molecular quantum mechanical calculations. The elemental strain has been related to the bulk modulus through the elemental volume of the affected chain section and the number density of contributing centers. In this way an upper bound has been obtained for the elemental strain as a function of these variables. Under the assumption that the charge concentrations are formed by charges trapped in nanovoids, estimates have been obtained for the smallest magnitude of the local field that is able to initiate aging, and these estimates have been correlated with the maximum number of electronic charges that such a void may trap. By doing so, a connection is found between the aging model and experimental space charge densities. This connection is the subject of Part 2 of this paper View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dielectric relaxation modeling in complex polymer systems

    Publication Year: 2001 , Page(s): 936 - 941
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (518 KB) |  | HTML iconHTML  

    The dynamic Monte Carlo WO simulation using algorithms based on the cooperative motion algorithm (CMA) is presented in application to analysis of structure and dynamics of single complex macro-molecules. Linear chains, polymer rings and polymer stars are considered. Relations between details of molecular dynamics in such systems and quantities which can be considered as observable in the dielectric relaxation measurements are presented and discussed in comparison with the existing experimental evidence View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interpretation of short-circuit discharge current in film capacitors based on an equivalent circuit

    Publication Year: 2001 , Page(s): 874 - 879
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (386 KB) |  | HTML iconHTML  

    Misfire phenomena in a discharge circuit composed of a capacitor and thyristor were investigated for operating frequencies to 198 Hz. Misfire was found to occur in polyethylene terephthalate (PET) capacitor circuits at low temperatures, whereas polypropylene (PP) capacitor circuits did not misfire under any conditions. Transient currents in the range 1 mA to 40 A were measured using a digital oscilloscope. A PET capacitor was shown to discharge initially with a given time constant, but subsequently discharge at a lower rate, extending the discharge period. It is this delayed gradual decay that causes misfire, and it is associated with residual charges trapped in the bulk of the PET film. The correlation between the transient discharge current and dielectric dispersion in PET and PP capacitors was investigated over a wide frequency range with the aid of the Debye model for dipolar polarization. It was found that the time dependence of the discharge current is related closely to the broad distribution of dipole relaxation time, with a discrepancy between the discharge current and the dielectric response attributed to charge trapping View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dielectric studies of PVDF crystallization. Application to in-situ monitoring in injection molding

    Publication Year: 2001 , Page(s): 911 - 916
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB) |  | HTML iconHTML  

    In recent years, experimental techniques based on microdielectrometry have presented an attractive and increasing interest for continuous monitoring in a nondestructive way of the advancement of thermoset resin reactions under cure. A new application of this technique has been carried out also for in situ monitoring of thermoplastic crystallization. Therefore, a dynamic rheometer equipped with a dielectric cell, as well as an instrumented slit die, were designed. The crystallization process is depicted by a conductivity drop as well as by the occurrence of a maximum in the real permittivity. The decrease of the specific conductivity results from a modification of the conductive paths whereas the increase in permittivity is due to an interfacial polarization phenomenon between the amorphous phase and the growing crystalline entities. As a second step of development, microdielectrometry has been applied for in situ monitoring of the crystallization of thermoplastics during an injection molding process. The electric sensors were located at the walls of the mold cavity so that an analysis of bulk dielectric properties during the filling, post-filling and the cooling phases could be performed. The dielectric method detailed herein provides a new non-invasive technique and could be applied to a closed-loop control of the injection molding process View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electrical characterization of SiOx and SiNx prepared by PECVD technique on In0.53Ga0.47As

    Publication Year: 2001 , Page(s): 1011 - 1015
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (386 KB) |  | HTML iconHTML  

    We have analyzed the electrical properties of both SiOx on InGaAs and SiNx on InGaAs, by utilizing a metal-insulator-semiconductor (MIS) structure. For improving film or interface quality, both oxide and nitride samples underwent furnace annealing (FA) in hydrogen at various temperatures. From the leakage current and capacitance characterization, we found that the electrical properties of the nitride samples such as leakage current, injected charges, and interface trap density are improved by FA, while on the contrary, the properties of the oxide samples are slightly deteriorated. The optimum annealing temperature for nitride samples is in the temperature range of ~400 to 450°C. Also, by secondary ion mass spectroscopy (SIMS) analysis, we provide evidence of inter-diffusion occurring in the oxide samples after annealing View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Current-field and conductivity-field characteristics of thin layers: the predictions of the Bottger-Bryksin model

    Publication Year: 2001 , Page(s): 1003 - 1006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (286 KB) |  | HTML iconHTML  

    Phonon-assisted hopping of electrons between spatially distinct locations is one of the basic transport mechanisms in solids. In the present contribution compare the current-field, and differential conductivity-field characteristics, calculated within the Bottger-Bryksin model applied to thin layers with spatially nonuniform distributions S(x) of hopping centers. In particular, we consider exponential and bi-exponential spatial distributions of centers, i.e. S(x) ∝ exp(-x/D), and S(x) -∝[exp(-x/D) + exp(-(L x)/D)], where L is the layer thickness, and D the distribution parameter. Although the model allows the calculations for both on-diagonal (energetic) and off-diagonal (positional) disorder, here we discuss only the case of discrete energy level of hopping centers. We show that the Bottger-Bryksin model predicts a strong 'tapping' effect in the case, where the surface densities of hopping centers at both contacts differ significantly. In such cases wide field intervals of negative differential conductivity are expected View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fundamental investigations on some transformer liquids under various outdoor conditions

    Publication Year: 2001 , Page(s): 1040 - 1047
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (730 KB) |  | HTML iconHTML  

    This paper deals with humidity uptake of some transformer liquids and its influence on electrical breakdown. The investigations were performed under some selective outdoor conditions on different insulating liquids, e.g. mineral oil, esters and silicones used in HV transformers. The temperature was set at 23 or 60 °C while the relative air humidity was varied between 20 and 90% to simulate climatic variation. The subject is important in HV transformers with an air breathing system since, even in such transformers where normally the air passes through a dehydrating apparatus with silica gel, a bad run can induce an accident. The scenario considered corresponds to such a defect in the breathing filter system, so that the insulating liquid in the transformer comes into contact with atmospheric humidity. The work presented is in two parts. The first part relates the evolution of the breakdown voltage in terms of the insulating liquid humidity content. The second part describes the evolution of insulating liquid humidity content in terms of surrounding relative air humidity. This evolution is observed during 30 days and the results are discussed regarding the ac electric strength according to International Electrotechnical Commission (IEC) or Verband der Elektrotechnik Elektronik Informationstechnik e.V. (VDE) standards. A correlation between the surrounding relative air humidity, temperature and humidity uptake rate is derived View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Charge carrier trapping in a one-dimensional system

    Publication Year: 2001 , Page(s): 1007 - 1010
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (293 KB) |  | HTML iconHTML  

    Theoretical models for one-dimensional structures, consisting of traps and recombination centers, are considered. The kinetics of trapping and recombination is studied numerically, especially in the case of thermal relaxation phenomena such as thermoluminescence (TL) and thermally stimulated current (TSC). Some peculiarities of TL and TSC are shown, which result from specific spatial arrangement of traps. The possibility of occurrence of an additional 'displacement' peak on TL and TSC measurement curves is predicted. Possible consequences for experimental studies of TL and TSC are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Discharge energy and dc tracking resistance of organic insulating materials

    Publication Year: 2001 , Page(s): 897 - 901
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (390 KB) |  | HTML iconHTML  

    As an evaluation test method for surface insulation degradation of organic insulating materials, the tracking test method is described in IEC Publ.112 as a safe and reliable evaluation. This publication has now been applied to the material selection. Due to the fact that the experimental values of the comparative tracking index (CTI), have wide variations, problems in reliability testing are abundant. In this paper, the correlation is investigated between discharge energy and tracking resistance of organic insulating materials. The test method resembles the IEC Publ.112 method, but with the application of dc voltages. The number of drops to tracking failure was measured with samples of paper based phenolic laminate, polybutylene terephthalate and epoxy resin. Discharge currents were detected when discharge occurred on the sample surface. A Gaussian wavelet analysis was applied to show energy levels of discharge currents. It was found that the tendency of discharge energy on organic insulating materials corresponded to the CTI of dc tracking resistance, and the results were an improvement on the IEC Publ.112 method for grading materials. The tracking resistance of organic insulating materials could be deduced from the discharge energy View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Particles in GIS characterization from acoustic signatures

    Publication Year: 2001 , Page(s): 1064 - 1074
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (925 KB) |  | HTML iconHTML  

    Acoustic techniques are accepted generally for diagnostics of gas-insulated systems (GIS). This paper addresses the problem of risk assessment of moving particles. The main part of the paper gives a general understanding of internal particle movement and excitation of external acoustic signals, leading to signature analysis and simple calculation of characteristics such as mass and length of the particle, and its elevation height in a GIS duct. This is supported by experimental studies of acoustic and electric signals from moving particles. It is shown how partial discharge (PD) at a particle reduces the jumping tendency, and how discharges with time will change when the shape of the particle changes. Experiments on sensor sensitivity and on the coefficient of restitution also have been carried out. The signature analysis and given formulas constitute a good tool for discriminating between harmless and harmful particles, as well as offering a tool for better understanding the particle movement View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Elemental strain and trapped space charge in thermoelectrical aging of insulating materials: life modeling

    Publication Year: 2001 , Page(s): 966 - 971
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (462 KB) |  | HTML iconHTML  

    On the basis of the new concept of elemental strain, used to describe a possible aging process occurring in polymeric materials, the expression for the life model, already proposed in a previous paper, must be modified, taking into account the possibility that the local strain is an elemental property of the polymer morphology, as suggested by molecular quantum calculations. By doing so, a connection can be established between the life model and space charge densities as revealed by experiments. The derivation of this new model and the correlation with analytical measurements is the subject of this paper. Applying this connection to electrical aging and space charge data for the same crosslinked polyethylene (XLPE) material has resulted in a set of material factors that we have demonstrated are both consistent with experiments and also produce physically feasible space charge fields that are capable of driving the proposed aging mechanism to the extent required 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