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Solid Dielectrics, 2004. ICSD 2004. Proceedings of the 2004 IEEE International Conference on

Date 5-9 July 2004

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  • Study on mechanism and characteristics of dielectric breakdown in polyimide film

    Publication Year: 2004 , Page(s): 908 - 911 Vol.2
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB) |  | HTML iconHTML  

    IGBT pulse width modulation (PWM) inverter driven induction motors for adjustable speed applications have been widely used since their introduction. However, the use of PWM variable frequency traction motor can lead to premature failure of the winding insulation, which most often occurs due to breakdown of the interturn insulation. In order to investigate the mechanism and characteristics of dielectric breakdown in a new kind of polyimide film, which is used as primary insulation in PWM inverter-fed traction motor, an experimental activity has been carried out on specimen according to applications in locomotives. The effect of different types of defects has been studied through several groups of breakdown test. Furthermore, fine texture of the breakdown part based on energy spectrum analysis and stereoscan photograph is analyzed; finally, the characterization and mechanism of the dielectric breakdown are presented. View full abstract»

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  • Optical and electrical investigation of dielectric gel behavior under high electrical field

    Publication Year: 2004 , Page(s): 912 - 915 Vol.2
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    Today, high voltage power semiconductors such as IGBTs, are being developed. As the voltage is increased, local electric fields applied to dielectric materials also increase. Local deterioration of dielectric materials due to partial discharges (PD) may appear and affect the reliability of the whole component. The usual way to detect PD's under ac voltage via electrical measurements is no longer applicable with the pulsed voltage wave shape encountered in power semiconductor applications. This paper presents investigations carried out with optical measurements of PD's in silicone gels, in a typical IGBT module structure. In addition, a very faint light emission is detected below the PD inception voltage. This light can presumably be attributed to an electroluminescence phenomena, such as previously reported in solids or aromatic liquids, and can constitute a non destructive technique that allows to detect the existence of local high fields in the gel. View full abstract»

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  • The impact of nanocomposite formulations on electrical voltage endurance

    Publication Year: 2004 , Page(s): 832 - 835 Vol.2
    Cited by:  Papers (24)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB) |  | HTML iconHTML  

    Previous work in which a conventional micron-sized filler was replaced by nanomaterials in an epoxy matrix has shown significant, and encouraging enhancements in the electric strength of the composites. The advantages gained were associated with the mitigation of Maxwell-Wagner polarization and the internal associated space charge, and an optimum particulate loading established. This contribution seeks to extend the previous work, by examining the electrical voltage endurance and partial discharge in a divergent field geometry. The voltage endurance tests demonstrate that significant improvements in endurance are also indicated. Similar results are seen in the partial discharge measurements. In order to gain a mechanistic understanding, the same electrode configuration has also been subjected to electroluminescence experiments in which both the steady-state and temporally-resolved light emission has been compared in these materials. Changes in the magnitude and onset field of the emission suggest that both the enhanced scattering of the nanocomposite and the mitigation of internal charge play a pivotal role in the enhanced voltage endurance obtained. Microscopy, dielectric spectroscopy and free volume measurements are also introduced to provide insight into the possible underlying mechanisms involved. View full abstract»

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  • Effective permittivity of random inhomogeneous media

    Publication Year: 2004 , Page(s): 571 - 574 Vol.2
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    We present a computational study for precise calculations of the effective (bulk) permittivity of two-phase lossless disordered composite media. The method is based on: (i) a finite-element description of composites in which both the host and the randomly distributed inclusions are isotropic phases, and (ii) an ordinary Monte Carlo sampling. We describe an algorithm which permits to generate distributions of hard circular disks made of a lossless dielectric (permittivity ε2) randomly placed in a plane made of a lossless homogeneous dielectric (permittivity ε1) at different surface fractions. Numerical examples are presented to connect the macroscopic property such as the effective permittivity to microstructural characteristics such as the radial distribution function. In addition, several approximate effective medium theories, exact bounds and exact dilute limit are used to test and validate the finite element algorithm. View full abstract»

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  • Development of CNT-polysiloxane composites for spacecraft applications

    Publication Year: 2004 , Page(s): 955 - 958 Vol.2
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    In geostationary orbit, thermal control coatings are exposed to a continuous bombardment of electrical particles, which have the capability to charge the external surface of the satellite. The accumulation of implanted charges leads to differences of potential between many parts of the satellite and can induce electrostatic discharges, which are detrimental to electronic equipment. To prevent this, coatings should have normalized characteristics like surface resistivity lower than 109 Ω/□ and bulk resistivity lower than 109 Ω.m. The Materials and Coatings Laboratory of the Thermal Control Service of the CNES Toulouse Space Centre has already developed low cost cold coatings called solar reflectors (SR) to replace current space coating named optical surface reflectors (OSR) and second surface mirrors (SSM). SR have been qualified only for low earth orbit applications because they do not evacuate space charges. Today the laboratory is looking for a solution to be able to use SR in geostationary orbit. This paper describes the effects of the incorporation of carbon nanotubes (CNTs) in a polysiloxane matrix, on thermo-optical and electrical properties. View full abstract»

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  • Corona ageing tests of RTV and RTV nanocomposite materials

    Publication Year: 2004 , Page(s): 804 - 807 Vol.2
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (333 KB) |  | HTML iconHTML  

    Silicone rubber insulating materials are superior to conventional porcelain materials, whose special water repellency and transfer of water repellency is favorable in power industry. However, two points are concerned in its application, and these are long-term reliability and lack of methods to assess their long-term performance. Corona and arc are important factors that induce degradation of RTV insulating materials during operation. Nanomaterials are used to modify the properties of RTV silicone rubber. Corona aging tests have been conducted, and the results of water repellency and IR analyses show that these nanomaterials can markedly improve its corona aging performance. View full abstract»

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  • Fuzzy systems for simulation and prediction of the residual life of insulating materials for electrical machines windings

    Publication Year: 2004 , Page(s): 542 - 545 Vol.2
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    Nowadays, the perspective diagnostic methods not only evaluate the current insulation condition, but also forecast the certain prognoses of the life of insulating material under the specified operational conditions. This contribution undertakes both simulation and prediction of the residual life of the Relanex insulating material for electrical rotating machine windings. In case of simulation, the current condition of insulating material based on the input data is determined. In case of prediction, the insulation condition in the future time k+1 is predicted based on the input quantities in the times k, k-1, k-2, etc. Prediction means forecasting an output quantity in future based on the N values of this quantity and/or the other quantities measured in the past. By means of the diagnostic quantities Ba (the quantity is proportional to the effective activation energy of polarization effects), Bv (the quantity is proportional to the effective activation energy of conductive effects) and Uk (the quantity is proportional to critical voltage) and by using a fuzzy method in the form of fuzzy models and predictors, we can determine breakdown voltage. This approach determines either the current condition of insulating material, taking into account electric strength, or the life prognosis of this material. To simulate and predict a magnitude of breakdown voltage, the Sugeno type fuzzy system was applied, especially for easy setting input parameters. According to the input quantity matrix (i.e., Ba, Bv, and Uk) measured at the Relanex insulating material samples, and according to a consecutive training phase, it is possible to simulate and predict the values of breakdown voltage Ups. The values can be compared to the real measured values of breakdown voltage Up. The evaluation of the fuzzy system quality is performed on the basis of relative and absolute errors. View full abstract»

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  • Laboratory tests for spacecraft charging and discharging: from Hertz, Millikan and de Broglie to today's questions

    Publication Year: 2004
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (279 KB) |  | HTML iconHTML  

    Hertz (1887) generated reasonably narrow-band radio frequency oscillations in metal dipoles using air discharges between the dipole elements. Nearly 50 years later technologists working with high voltage particle accelerators and gamma-irradiators noticed arc-discharge trees entirely inside solid insulating dielectrics (glass) stimulated by irradiation alone, without applied voltage. B. Gross et al. performed an early scientific study of the phenomena and related the onset of internal discharges to the quantity, in coulombs, of irradiation charge stopped inside the dielectric and held there for long time periods. Recent international studies have related the charge-induced electric field strength in the dielectric to the propagation of the internal discharge tree. When it exits a surface of the dielectric into vacuum, gas from the tree provides a conductive path across the vacuum. Higher conductivity is produced by higher quantities of gas. Whereas Hertz air arcs were low impedance, ≪70 Ohms, generating resonant responses, the irradiated unbiased dielectric arcs appear to be high-impedance, low-Q, phenomena. Recent researches address practical questions for spacecraft subjected to space radiations: (1) How many discharge trees are initiated in the dielectric per unit time? (2) How much electric current is conducted as a function of time? (3) What is the charge decay time constant in the dielectric? (4) Over spacecraft lifetimes, how is the charge distributed in the dielectric? (5) How does the initial dielectric discharge evolve to short out a HV power system? (6) How can discharges propagate along the vacuum surface of a dielectric? (7) How does the discharge current distribute among spacecraft electronic circuits. (8) Can a discharge burn out sensitive electronic devices and how can this be prevented?. View full abstract»

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  • Specificity of proton effects on polymers

    Publication Year: 2004 , Page(s): 972 - 975 Vol.2
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    Protons affect the polymers mainly through scission and crosslinking of macromolecule chains. Ionization processes at proton non-elastic scattering define these effects. One of the most important problems of radiation physics and chemistry of polymers is dependence of radiation effects on polymers on the kind of ionizing radiation or the LET problem. Analysis of such dependence for protons and some other kinds of radiation is presented. A detailed examination of 100 MeV proton collisions in polyethyleneterephtalate (PETP, trade mark Mylar) on the base of the sample heat conductivity behavior revealed an important role of atom displacements resulting from elastic nuclear scattering of low energy ions. Such damage of polymer molecules was not obtained for other examined types of radiation, in particular, for recoil nuclei at reactor neutron irradiation and for 60Co-gamma radiation. View full abstract»

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  • Compressive strength of FRP for insulator

    Publication Year: 2004 , Page(s): 812 - 815 Vol.2
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    FRP has been used much for core materials of insulator. FRP consists of fiber and plastics (resin and binder). The fiber contributes strength to FRP. The fiber orientation in FRP has a great effect on the strength of FRP because the strength of FRP mainly depends on the strength of fiber. The direction of applied stress of FRP is different from the kinds of insulators. In this study, inner part of FRP rod was made unidirectionally by pultrusion method and outer part of FRP rod was made by filament winding method. Compressive strength and stress of FRP rods were simulated according to the winding orientation of glass fiber. Simulated value and real evaluated compressive strength were compared each other. View full abstract»

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  • Study by simulation of the electric field within dielectric environments

    Publication Year: 2004 , Page(s): 594 - 597 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB) |  | HTML iconHTML  

    Our work consists to develop a computer code based on charge simulation method and to apply it for the calculation of the electrostatic field in important and complex geometries containing several homogeneous mediums. In particular calculation of the field with axial symmetry, the analytical example is a geometry stem plan, the plan representing a heterogeneous ground of variable conductivity. View full abstract»

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  • Finite element analysis of bipolar corona

    Publication Year: 2004 , Page(s): 538 - 541 Vol.2
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    This paper aims at analysis of the bipolar corona in two conductors-to-plane configuration. The physical model is based on the Poisson and continuity equations. The model employs an iterative technique, wherein the finite element method is used to compute electric field structure for an assumed charge density distribution, and the method of characteristics is used to compute charge density structure for an assumed electric field distribution. A linear biased probe is used to measure, at the ground plane, current density and electric field during the bipolar corona. The computed values are in good agreement with the experimental data. View full abstract»

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  • Determination of conductivity parameters of dielectrics used in space applications

    Publication Year: 2004 , Page(s): 936 - 939 Vol.2
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (397 KB) |  | HTML iconHTML  

    This paper presents a method for the determination of the conductivity of dielectric materials under radiation environments typical of those found in the Van Allen belts. Particular significance is given to the effects of both temperature and dose rate and their effects on the conductivity of dielectrics. The beginnings of the study are presented here with electron irradiations of ∼1 mm thick samples of FEP teflon and FR-4 epoxy glass. Irradiations were performed in the QinetiQ relativistic electron environment facility (REEF) which utilises a 90Sr β emitting source. Results for both materials clearly illustrate the expected dependence of charging rates on temperature. Using a model of internal charging and measurements of surface potential during charging, the dose rate and temperature dependences of conductivity were calculated for each material. Provisional results of these calculations are presented in this paper. View full abstract»

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  • An assessment of ageing of oxide varistors exposed to pulse hazards using dielectric spectroscopy

    Publication Year: 2004 , Page(s): 727 - 730 Vol.2
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (377 KB) |  | HTML iconHTML  

    The common use of zinc oxide varistors has brought about qualitative changes in the overvoltage protection of electronic and electric power equipment. This is due to the special properties of ZnO varistors, mainly the high current-voltage characteristic nonlinearity and the capacity to withstand strong current surges. In service conditions varistors are exposed to the sustained action of constant or variable voltage or momentary overvoltage pulses. As a result varistors may undergo degradation reflected in changes in their current-voltage characteristics. The changes are manifested in an increase in leakage current and are limited to a highly thermally activated low-current region where the performance of the varistor is determined by the parameters of the potential barriers. Thus one can conclude that the degradation is a result of processes leading to the movement of ions and the deformation of the potential barriers. Therefore, dielectric spectroscopy (testing of the dielectric response in a wide frequency band) could be useful for the investigation of degradation changes, and so this method is proposed in this paper. View full abstract»

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  • Effects of particle size and amount of Al(OH)3 on silicone rubber for insulator

    Publication Year: 2004 , Page(s): 808 - 811 Vol.2
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (478 KB) |  | HTML iconHTML  

    Silicone rubber has very excellent chemical stability and hydrophobicity. Silicone rubber has been used very much for housing materials of polymer insulator. Al(OH)3 is added to the silicone rubber for improvement of its resistance against surface discharge. Hydrophobicity recovery properties and arc resistance of silicone rubber could be different by the amount and particle size of Al(OH)3. In this paper, Al(OH)3 with different particle size was added to the silicone rubber during compounding. Silicone rubber was deteriorated by a corona treatment. Hydrophobicity recovery rate after corona treatment and arc resistance of silicone rubber were investigated. Hydrophobicity recovery rate of silicone rubber was evaluated by the measurement of contact angle. Arc resistance was evaluated by measuring weight loss of silicone rubber after arc resistance test. It was observed that the hydrophobicity recovery rate and arc resistance of silicone rubber were different according to different particle size and amount of Al(OH)3. View full abstract»

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  • Simulation of PD location method in oil based on UHF and ultrasonic phased array receiving theory

    Publication Year: 2004 , Page(s): o590 - o593 Vol.2
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    In this paper, a new partial discharge location method based on UHF and ultrasonic phased array receiving theory is presented. The plane sensor is consisted of two phased receiving arrays, which respectively receive UHF and ultrasonic signals emitted by the same partial discharge source. Regarding the time point of signal detected by the UHF phased receiving array as time benchmark, the time delay of ultrasonic signals received by acoustic phased receiving array can be obtained and the distance between PD source and the sensor can be calculated, then the PD dimensional position can be found out using the azimuth and elevation angle at which the phased receiving arrays scan. Because PD sources of different space positions lead to different space angles of beam combination, which represent corresponding maximum PD signals, and to different time benchmark compared to the same sampling initial point and different time delay, the locating of multiple PD sources can be reached. Several examples of PD in oil are simulated using this novel location method and the results indicate the method can exactly locate the PD in oil and solve the location of multiple PD sources. View full abstract»

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  • Ab-initio investigation of a short range order and ionic conductivity in the La-Li-TiO3 system

    Publication Year: 2004 , Page(s): 607 - 610 Vol.2
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    We have used ab-initio FLAPW method for the investigation of atomic and electronic structure of La0.5Li0.5TiO3 compound. We have carried out the set of total energy calculations with different Li atom location. It was determined that in this compound, a tetragonal crystal structure in which La atoms are alternated with Li atoms is energetically efficient. It is shown that a total energy minimum has been reached when Li atoms are centered on the faces of the cube formed by Ti atoms. We have derived a new formula describing lanthanum-lithium ionic conductors: La(23-x)/Li3x3(1-x)TiO3. Dependence of the number of lithium vacancies on La and Li concentration for different ordering of these atoms was determined. We have determined possible Li atoms diffusion ways, and calculated the energy barriers too. View full abstract»

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  • Modeling dielectrics and ferroelectrics combining local field calculations and Monte-Carlo steps

    Publication Year: 2004 , Page(s): 509 - 512 Vol.2
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    It is investigated which dielectric and ferroelectric properties can be understood if the dipole-dipole interactions in solids are considered. To this aim a combination of local field calculations and Monte-Carlo (MC) steps is employed taking into account a deterministic and a stochastic contribution. The dipole systems under consideration with up to 2000 dipoles are embedded between electrodes. The ensembles consist of permanent dipoles fluctuating thermally activated in double well potentials and/or induced dipoles. At each dipole the local field is calculated. The moment of an induced dipole is proportional to the field, and the direction of a permanent dipole is determined by a field weighted random MC step (importance sampling). View full abstract»

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  • The use of neural networks for the life prediction of insulating material of electric rotating machines

    Publication Year: 2004 , Page(s): 546 - 549 Vol.2
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    The life of the insulating systems of electric rotating machines is strongly dependent upon electrical and thermal features of the insulating material used. The subject of the diagnostic prediction is to specify the condition of insulation used. At present days, the most popular prediction tools are the methods of artificial intelligence, and one method is the neural networks. This paper is concentrated on the use of neural networks in the life prediction of Relanex insulating material that is applied as insulation of electrical machine windings. In this case the condition of insulating in a time step k+1 is predicated from input quantity in time steps k, k-1, k-2, etc. Anyway the prediction means forecasting of quantity in future from N previous measurement this or other quantities in the past. The first part of the paper describes the use of artificial neural networks which forecast the life of insulating material for windings in electric rotating, the description of train and test data and setting of neural network for prediction. The second part shows the simulation of insulating material behavior with neural networks. Tables evaluate the application of this tool for the solution of the problems investigated. We have used the above-mentioned neural networks for the prediction of insulating materials that were programmed in Matlab 6 environment. View full abstract»

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  • Neural networks in prediction of accelerated thermal ageing effect on oil/paper insulation tensile strength

    Publication Year: 2004 , Page(s): 575 - 577 Vol.2
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (290 KB) |  | HTML iconHTML  

    The ageing process of insulation can be monitored by several properties measurements, which need long test period to have a complete database to predict the dielectric behaviour of the HV insulation. The main purpose of insulation monitoring is to limit stoppage of electric service by giving the information on dielectric deterioration leading to a failure of HV equipment. Prediction of transformer oil/paper thermal ageing may help considerably to improve its maintenance. When the oil is in contact with paper, the BDV of oil shows increasing trend for short period. View full abstract»

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  • Electrostatic behaviour of materials in a charging space environment

    Publication Year: 2004 , Page(s): 917 - 927 Vol.2
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (966 KB) |  | HTML iconHTML  

    Electrostatics is one of the major concerns of spacecraft technology. Space is filled with hot and low-density plasma building up high differential voltages resulting in electrostatic discharges, sometimes causing an anomalous behavior of spacecraft electronics. The interaction of the satellite with its environment induces a static charge of the various materials which it is made of. The flow and the evacuation of the charges would require a conductive satellite. Unfortunately, the reality is different and satellites are covered with dielectric materials highly resistant for thermo-optic specific purpose. It is resulting in an absolute charge value of the structure of the satellite and in a differential charge built-up between its components that can be at the origin of electrostatic discharges which consequences can end up in the loss of the satellite itself. Typical anomalies are reviewed; it is shown how they can be recognized as consequences of environmental induces discharges. The distribution of charges over different parts of the spacecraft is depending of ambient conditions: plasma temperature and density and sun illumination. Surface and internal charging are possible; they result in dielectric or metal arcing discharges. Understanding of charging phenomena allows us to define mitigation techniques by controlling charging, electromagnetic interference. Finally, we end with the presentation of what it is done in France and in Europe though activities in the domain of space environment in order to take into account problems in a more general context. View full abstract»

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  • PD characterization using short duration Fourier transform of acoustic emission signals

    Publication Year: 2004 , Page(s): 695 - 698 Vol.2
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (391 KB) |  | HTML iconHTML  

    The frequency spectrum of acoustic emission signals obtained using short duration Fourier transform as the artificial neural network input parameter has been investigated. The acoustic spectrum is not significantly influenced by applied electric stresses compared with (φ-q-n patterns or statistical operators such as skewness and kurtosis. A feed forward neural network using the back propagation algorithm was initially applied to characterize acoustic emission signals produced from different shapes of void within a polyethylene dielectric. It was then used to discriminate between the background noise and acoustic emission signals produced by void discharges or treeing discharges. The obtained identification results for the different experimental arrangements are encouraging. View full abstract»

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  • Effect of temperature on electroactive films of cellular polypropylene

    Publication Year: 2004 , Page(s): 784 - 787 Vol.2
    Cited by:  Papers (1)
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    We report the effect of temperature on the magnitude of the d33 coefficient of cellular polypropylene films. We have also measured the short-circuit, thermally-stimulated-current from poled samples as well as the dependence of complex capacitance on temperature at frequencies around the thickness-mode resonance. We conclude that the thermal stability of the piezo properties depend on both the electrical and mechanical properties of the material. View full abstract»

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  • Identification of electrical tree growth in insulation systems by fuzzy logic techniques based on partial discharge acquisition

    Publication Year: 2004 , Page(s): 661 - 664 Vol.2
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (454 KB) |  | HTML iconHTML  

    Aim of this paper is to validate the effectiveness of an artificial intelligence technique devised for tree diagnosis in solid insulation systems. For this purpose, electrical and optical partial discharge (PD) measurements were carried out on specimens containing treed regions of different typologies ("bush" and "branch"). The results obtained by the above-mentioned diagnostic procedure were checked on the basis of the tree typology. View full abstract»

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  • Characterization of partial discharge processes - what parameters work best?

    Publication Year: 2004 , Page(s): 636 - 639 Vol.2
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (359 KB) |  | HTML iconHTML  

    This paper discusses and compares different methods to analyse partial discharge data sets, starting with 'simple' frequency distributions of different parameters derived from the externally applied voltage and pulse height distributions extracted from the data set as a whole. In addition sequence correlated data such as e.g., voltage sequences or sequences of voltage changes or time differences between consecutive discharges and 'combined parameters' are also discussed. View full abstract»

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