Showing papers in "IEEE Transactions on Electrical Insulation in 1986"
TL;DR: In this article, the authors present a review of previous research in SF6 decomposition relating to the operation of gas-insulated switchgears, gas-instrained transmission lines, and electrostatic accelerators.
Abstract: The increasing application of SF6 as an insulating gas has led to many studies on SF6 decomposition in gas-insulated equipment. In the presence-of an electric arc, spark or corona, SF6 decomposes to a wide variety of chemically active products which possess completely different properties from SF6. The accumulation of these decomposition products in the equipment has caused concerns regarding personnel safety and material compatibility problems. This paper reviews previous research in SF6 decomposition relating to the operation of gas-insulated switchgears, gas-insulated transmission lines, and electrostatic accelerators. Results on the qualitative and quantitative determination of the by-products and their formation ion rates in various modes of electrical discharges are summarized. The mechanisms leading to the formation of transient and stable products are described. In particular, the influence of discharge energies and impurities on the formation of SOF2 and SO2F2, the two dominant stable by-products, is discussed. The effects of the by-products on personnel safety and equipment ent dielectric integrity are presented. The application of SF6 gas analysis as a tool for diagnosing the internal condition of gas-insulated equipment is assessed. Based on the results of many phenomenological observations, future research activities are suggested to address the issues of safety, compatibility and equipment aging. More fundamental studies on electron, ion, and neutral reaction rates in an SF6 discharge are required to gain a better understanding of the decompositon mechanisms and the influence of the products on equipment operation.
328 citations
TL;DR: A review of surface flashover with primary emphasis on the understanding of physical processes leading to discharge initiation and insulator flashover under high voltage excitation is presented in this article, where the authors suggest a physical explanation for the observed phenomena, including ionization, surface charging, partial discharges, optical activity and gas/dielectric interactions.
Abstract: Surface flashover in compressed-gas insulated systems is a much studied, but poorly explained phenomenon. In this paper we review the literature of surface flashover with primary emphasis on the understanding of physical processes leading to discharge initiation and insulator flashover under high voltage excitation. The flashover models presently in vogue will first be discussed, followed by the results of some recent experiments which are likely to have an impact on further modeling. Included in this context are phenomena such as ionization, surface charging, partial discharges, optical activity, and gas/dielectric interactions. Finally, the influence of system parameters such as insulator size, shape, surface condition, triple junction geometry, voltage waveform, gas formulation and particle contamination are discussed with regard to their effect on the flashover characteristics. Mechanisms are suggested in an effort to provide a physical explanation for the observed phenomena. Although the physics of the discharge initiation and propagation processes are presently not well understood, and the present models only account for a few of the mechanisms known to be important in the discharge development, all the work points to an interaction between the spacer and the various electron/photon processes in the surrounding gas volume. This interaction has not been accounted for in the discharge models proposed to date. Further modeling work should incorporate these interactions and the intrinsic properties of the dielectric ric which are related to these interactions. More basic research is suggested to provide a better understanding of the physics of the discharge initiation and breakdown phenomena.
163 citations
Abstract: A new set-up, using a video camera, allowing easy and economical access to the velocity distribution of streamers is presented. Our study focuses on the behavior of negative streamers in a variety of liquids, either pure or containing ionic or non-ionic additives, in point-plane geometry. The propagation velocity distribution has always a more or less marked minimum, whatever the polarity and the shape of the streamer (bush-like or filamentary). Such a velocity distribution is similar to that of the field on a growing conducting sphere. There is generally a very close correlation between the shape and the velocity: the higher the velocity the more filamentary the streamer. This is still the case even when in the same liquid we have either subsonic or supersonic velocity. It is shown that the positive transient currents are also in favor of the model of the conducting sphere and not of a unique conducting filament even though there is evidence that the streamer is filamentary. Some of the theoretical models of streamer propagation already proposed are appraised, in particular that of Devins et al. which is thought to be the most accurate in describing experimental results. As concerns the initiation phase, the time lag until the appearance nce of the streamer dec, reases sharply when voltage is increased. This time lag also depends on space charge phenomena. Initiation voltages are always higher with positive polarity than for negative polarity for a series of tested simple or industrial liquids.
157 citations
TL;DR: In this article, a new CIGRE electrode is recommended to assess the resistance of insulating materials against internal partial discharge (PD) pulses, and the skewness of the profile of a PD pulse train can be used to check whether insulation is treed or not.
Abstract: Partial discharge (PD) pulses are considered to be generated after application of overvoltage across a cavity. Their magnitude is proportional to the n-th power of overvoltage. It decreases with an increase in cavity space and moisture content. Very long time lags for PD inception, such as even a day, was confirmed. This phenomenon is associated with PD's statistical time lag in the number of free electrons in the gas (O2, N2). Oxygen and nitrogen exhibit their distinctive features. Nitrogen and moisture generate swarming micro PD pulses, while oxygen causes large PD pulses. Nitrogen PD tends to produce local degradation, i.e., pits, while oxygen PD contributed to uniform erosion. Oxygen is presumed to be almost all consumed in a closed cavity by PD at its early stage, leaving nitrogen, moisture and other gases behind to facilitate swarming micro PD to take place. Pits are followed by treeing. A new measure, i.e., the skewness of the profile of a PD pulse train can be used to check whether insulation is treed or not. A new CIGRE electrode is highly recommended to assess the resistance of insulating materials against internal PD.
147 citations
TL;DR: In this article, the formation of decomposition by-products produced by electrical spark discharges in SF6 has been investigated by quadrupole mass spectrometry and the amount of SF4 formed was measured by "in situ" detection, utilizing a threshold technique for monitoring the SF4 ion (SF+3) in an SF6 background.
Abstract: The formation of decomposition by-products produced by electrical spark discharges in SF6 has been investigated by quadrupole mass spectrometry. The by-product SF4 was found to be a precursor to many of the long-lived decomposition by-products identified (SOF2, HF, SO2, and SiF4). The amount of SF4 formed was measured by "in situ" detection, utilizing a "threshold" technique for monitoring the SF4 ion (SF+3) in an SF6 background. The rate constant for the hydrolysis of SF4 was measured (at 350 K) and found to be ~2×10-19 cm3s-1. In addition to moisture, the effects of SiO2 and electrode material have been briefly examined. Quantification of the amounts of long-lived by-products of spark discharge in SF6 yielded the following ranking: SOF2 > SOF4 > SiF4 > S02F2 > SO2. The energy and pressure dependences in the ranges of 0.5 to 14.5 J/spark and 40 to 233 kPa respectively, of the amounts of the various by - products were examined.
128 citations
TL;DR: A very elegant technique to generate this pressure wave involves the use of a short-duration laser pulse as discussed by the authors, which acts as a virtual probe sensitive to charge, field or potential.
Abstract: When an electric field is applied to an insulating material three basic processes can take place: the dipoles tend to rotate, ions migrate and space charge can be injected at the interfaces, depending on such parameters as temperature or applied electric field. For many years, a direct analysis was impossible since the experimentally observable variables gave only an average of what was taking place in the samples under study. Many methods were developed over the years combining available measuring techniques with theoretical hypotheses. They led to phenomenological descriptions but it appeared that a direct measurement of space charge or polarization distributions in the materials would be a way for understanding the physical processes involved. In this paper we will present the evolution of these methods and will describe on which at present seems the most promising. It uses the propagation in the sample of a pressure wave which acts as a virtual probe sensitive to charge, field or potential. A very elegant technique to generate this pressure wave involves the use of a short-duration laser pulse. It will be shown how this can find applications in a very large number of areas. Examples will be given in such different fields as electrets, HV insulation, and transducer materials.
119 citations
TL;DR: In this article, a computer-aided measurement system has enabled novel interpretation of partial discharge (PD) signals, and the authors take into consideration voltage phase-angle at which each PD pulse takes place, and consequently need simultaneous measurement of the pulse height q and the phase angle?.
Abstract: A computer-aided measurement system has enabled novel interpretation of partial discharge (PD) signals. We take into consideration voltage phase-angle at which each PD pulse takes place, and consequently need simultaneous measurement of the pulse height q and the phase angle ?. According to the analysis of PD pulse signals, close relation between PD pulse signals and insulation degradation or defects was found. New PD characteristics such as 4-q distribution profile (average pulse height versus phase angle) can detect the growth of electrical trees in insulation caused by PDs. The skewness of the ?-q distribution was found to be a good measure for insulation degradation by PDs and for electrical trees. The skewness of the ? -q distribution was found to be an indicator of the shape of a void in which PDs occur. A skewness plane or an S-plane is proposed to monitor electrical treeing degradation. Furthermore, an effective noise reduction system is devised for practical b application of the new profile for insulation diagnostics.
114 citations
TL;DR: In this article, the roles of structure and local order especially for polymeric electrets and the influence of ionic and polar impurities in determining the magnitude, life-time, and transport of charges in electret materials are outlined.
Abstract: Interfaces and surfaces are always part of an electret structure and frequently, if not invariably, exert a controlling influence on their properties. Although classical featureless models ahve often been used to describe the behavior, especially where contact to metal electrodes is involved, the situation is much more complex. The nature of interfaces and contacts and of charge transfer across them is reviewed using the concepts of modern molecular electronics and electrochemistry. The effect of blocking and non-blocking conditions and the special behavior at free surfaces is considered. The roles of structure and local order especially for polymeric electrets and the influence of ionic and polar impurities in determining the magnitude, life-time, and transport of charges in electret materials will be outlined.
68 citations
TL;DR: In this paper, the performance of polymeric insulating materials for outdoor insulation -high temperature vulcanized (HTV) silicone rubber, ethylene-propylene rubber (EPR) and epoxy resins with a commonly used inorganic filler, alumina trihydrate, under salt-fog conditions is investigated.
Abstract: This paper describes the performance of the widely used polymeric insulating materials for outdoor insulation - high temperature vulcanized (HTV) silicone rubber, ethylene-propylene rubber (EPR) and epoxy resins with a commonly used inorganic filler, alumina trihydrate, under salt-fog conditions. The role of the filler and the effect of the filler concentration in imparting track resistance to the materials is investigated. Various methods to describe the surface aging of polymer materials such as the peak and the average of the leakage current, the cumulative charge, the weight loss and the flashover voltage have been investigated. The results show that at moderate concentrations of filler, 105 to 130 parts per hundred (pph) of polymer, there is little difference in the performance of silicone rubber and EPR materials. At low concentrations of filler (30 pph), the EPR samples track whereas the silicone rubber samples erode. The epoxy materials exhibit inferior properties when compared to silicone rubber and EPR. The results also indicate that monitoring the weight loss, the reduction of the flashover voltage, and the peak of the leakage current are better methods to characterize aging of insulators than the average of the leakage current or the cumulative charge.
65 citations
TL;DR: In this paper, the typical research studies done by such institutes are outlined in detail, and some typical typical studies are discussed in detail in the paper "Radiation effects on polymeric insulators".
Abstract: Radiation effects on polymeric insulators have been studied actively in Japan by several universities and by national research institutes such as the Japan Atomic Energy Research Institute (JAERI), as well as by several manufacturing companies. Some typical research studies done by such institutes are outlined lined in this paper.
51 citations
TL;DR: In this article, the formation of space charges in the insulating material has become a significant problem during the production and usage of HV dc power cables with plastic insulating materials.
Abstract: During the production and usage of HV dc power cables with plastic insulating materials, formation of space charges in the insulating material has become a significant problem. Many studies on the formation of space charge in insulating materials have been conducted and these past and current Japanese studies are reviewed in this paper.
TL;DR: In this paper, the status of insulation diagnosis for rotating machine insulation in Japan is described, and deterioration judgement criteria, diagnostic methods under development and monitoring methods are presented for rotating machines.
Abstract: In recent years it is strongly required to have high reliability in rotating machines On the stator windings, many kinds of non-destructive tests can be used to check their deterioration or to estimate their life This section describes the status of insulation diagnosis for rotating machine insulation in Japan These are (1) deterioration judgement criteria, (2) diagnostic methods under development and (3) monitoring methods
TL;DR: In this paper, the polarization reversal and the ferroelectric hysteresis loop have been studied for copolymers of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) with 47.2, 63.0, 70.7, and 86.8 mo1% TrFE content, respectively.
Abstract: The polarization reversal and the ferroelectric hysteresis loop have been studiedfor copolymers of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) with 47.2, 63.0, 70.7, and 86.8 mo1% TrFE at high electric fields of up to 100 MVm-1 and at frequencies of 5 to 100 mHz over a wide range of temperatures. The copolymers exhibited two current peaks associated with the polarization processes at different field intensities: one at a higher field Eh was due to the polarization reversal; the other at a lower field E? occurred in the opposite polarity at high temperature, indicating the depolarization process. These two current peaks were related with a double hysteresis loop in the copolymers. As the temperature was lowered, the field E? decreased crossing zero and changed in the polarization field. The temperature T? at which E? reduced to zero was 321, 277, 253, and 239 K for 47.2, 63.0, 70.7, and 86.8 mo1% TrFE content, respectively. It is suggested that the crystalline form associated with the ferroelectric polarization in these copolymers is slightly different above and below the temperature T?.
TL;DR: The literature on anomalous currents in polymers has been assembled as mentioned in this paper, and the effects have been classified into isothermal decay reversals, reversals in thermally stimulated depolarization, abnormal charging curves, oscillations, and other effects.
Abstract: The literature on anomalous currents in polymers has been assembled. The effects have been classified into isothermal decay reversals, reversals in thermally stimulated depolarization, abnormal charging curves, oscillations, and other effects. It has not been possible to identify the conditions which lead to unusual behavior, owing to the disparate nature of the available experimental work. The models for these effects include space charge relaxation with detrapping, ionic drift and temperature dependence of the dielectric permittivity. Each model explains a large part of the effects within its range of applicability. However, several of the charge transport models are based on inconsistent assumptions, and invoke blocking effects at electrodes, for which there is little independent confirmation. It is noted that many of the experiments may be vitiated by artefacts such as imperfect conditioning and inadequate time delays for equilibration. It is recommended that careful sample preparation, rigorous tests of conditioning, and monitoring of charge location should be routinely employed.
TL;DR: In this article, it was shown that at low voltages the emitted light, which is mostly in the visible spectral range, is not immediately harmful to the insulator and that at high voltages that the emitted UV radiation would include more energetic and intense ultraviolet (UV) radiation and this UV could cause rapid degradation of the polymer and give rise to an electrical tree.
Abstract: Based on charge transfer mechanisms at the polymer interface, it is bhown that the injected charges are responsible for the light emitted during tree initiation in LDPE subjected to highly divergent fields. Light was not only detected d in degassed specimens as reported by other workers, but also in air-impregnated (normal) specimens as well as in those impregnated with other gases. The photoemission characteristics of degassed specimens were found to be different from all others and probably are due to radiation from electron-hole recombination. In all other specimens a combination of this and other radiative phenomena could be responsible. It is proposed that at low voltages the emitted light, which is mostly in the visible spectral range, is not immediately harmful to the insulator. It is only at high voltages that the emitted light would include more energetic and intense ultraviolet (UV) radiation and this UV could cause rapid degradation of the polymer and give rise to an electrical tree.
TL;DR: In this article, the authors found that the orientation of the amorphous phase causes a pronounced decrease observed both in ionic conduction and in dielectric loss in non-oriented PP films.
Abstract: BO-PP films have fairly different morphologies to those of non-oriented PP films. These morphological differences were found to originate from the orientation of the crystalline and amorphous phases. The orientation of the amorphous phase causes a pronounced decrease observed both in ionic conduction and in dielectric loss. Two types of BO-PP films were found to have fairly different morphologies: the tubular type seems to exhibit a network structure made of oriented crystalline zones which are linked with slightly entangled amorphous chains, while the tenter type shows a spherulite-deformed structure made of a highly oriented cyrstalline phase connected with elongated and highly oriented amorphous chains. Despite their dissimilar structures, the two BO-PP films studies were found to have generally the same dielectric behavior except for the activation energy of the conduction and the dielectric relaxation processes.
TL;DR: In this paper, the field nonuniformity factor for hemispherically capped rod-plane gaps is computed and two simple expressions for gaps with the ratio of gap length to rod radius ranging from 1 to 500 are presented.
Abstract: This communication compiles published computed data of the field nonuniformity factor for hemispherically capped rod-plane gaps, and presents two simple expressions for gaps with the ratio of gap length to rod radius ranging from 1 to 500.
TL;DR: In this paper, the authors applied the pressure wave propagation (PWP) method to the study of HV insulators, such as low density polyethylene (LDPE) used for HV cables.
Abstract: In the field of electrical insulation, polymers are progressively replacing formerly used materials. When such an insulator is subjected to a voltage gradient, an internal space charge and a polarization develop, eventually reducing the apparent electrical strength of the material. We have applied the pressure wave propagation (PWP) method to the study of HV insulators, such as low density polyethylene (LDPE) used for HV cables. The spatial charge distribution is successively measured in samples subjected to various processes. The influence of additives in the development of a space charge under electric stress is directly shown. We have also observed that the nature of the electrode-iinsulator interface strongly affects the charge distribution throughout the insulator, and that charge injection from these interfaces occurs at much lower applied voltage gradients than previously assumed. The evolution in time of the charge distribution in samples submitted to voltage gradients, at 20 and 700C, is studied. These results show that an equilibrium is reached, from which the life expectancy of materials and cables can be evaluated.
TL;DR: In this paper, experimentally determined fractional separation functions of different types of electret filters are presented for the particle size range from 10 nm to 10, um at a filter face velocity of 10 cm/s.
Abstract: Deep-bed electret filters are used to separate small solid or liquid particles from gas flows. Compared with conventional deep-bed filters of similiar pressure loss, they operate with substantially higher collection efficiencies. During the course of filtration, however, the electrical charges of the deposited particles neutralize the electret fibers, temporarily decreasing the collection efficiency. In this paper, experimentally determined fractional separation functions of different types of electret filters are presented for the particle size range from 10 nm to 10 , um at a filter face velocity of 10 cm/s. The initial efficiencies are compared to that of a conventional (glass fiber) filter and also to those of the electret filters in discharged state. The results of long-term filtration experiments show that a complex time-dependent behavior exists for different filter materials. Furthermore, two experimental methods are presented and discussed which determine the charge characteristics of single electret fibers.
TL;DR: In this paper, laser-induced pressure pulses (LIPP's) of < 500 ps duration have been used to measure the ultrasonic attenuation in fluoroethylenepropylene (FEP), polyethyleneterephthalate (PETP) and polyimide(PI) as well as the charge, polarization, and piezoelectricity profiles in the thickness direction of polyvinylidenefluoride (PVDF) and FEP electrets with a resolution of 1 to 2?m.
Abstract: Laser-induced pressure pulses (LIPP's) of < 500 ps duration have been used to measure the ultrasonic attenuation in fluoroethylenepropylene (FEP), polyethyleneterephthalate (PETP) and polyimide(PI) as well as the charge, polarization, and piezoelectricity profiles in the thickness direction of polyvinylidenefluoride (PVDF) and FEP electrets with a resolution of 1 to 2 ?m. Measurements on PVDF, obtained during and after poling, reveal a uniform polarization profile for samples poled at room temperature and a nonuniform polarization, concentrated near the positive electrode, for samples poled at elevated temperatures. In FEP, charges injected by electron beams are stored close to the CSDA range while negative carriers deposited by corona discharges or liquid-contact electrodes are trapped at, or close to, the surface.
TL;DR: In this article, the infrared spectra of polyvinylidene fluoride (PVDF) and barium titanate (BaTiO3) and various proportions of composite were studied.
Abstract: Polyvinylidene fluoride (PVDF) and barium titanate were mixed in different weight fractions, and the infrared spectra of PVDF (pure) and various proportions of composite were studied. The absorption peak amplitudes corresponding to the a form of PVDF have been significantly reduced, absorption peak amplitudes corresponding to the s form of PVDF have been slightly affected, and the absorption peak amplitudes corresponding to the ? form of PVDF have been considerably increased. The composite with 70% wt. of BaTiO3 has a high dielectric permittivity and pyroelectric coefficient.
TL;DR: In this article, the authors describe a procedure for HV insulating system design which combines the classical approach of changing the distances between system elements with optimization of their contours, which is improved by cubic spline expansion for surface charge density.
Abstract: This-paper describes a procedure for HV insulating system design which combines the classical approach of changing the distances between system elements with optimization of their contours. An integral equation technique for solving electric fields, which is improved by cubic spline expansion for surface charge density, is applied in this procedure. In the contour optimization technique an additional step is introduced: smooth approximation of a corrected contour by circular arcs. This step allows a relatively simple geometrical description of a corrected contour. The application of the procedure is illustrated by practical examples.
TL;DR: The Metal Oxide Surge Arrestor (MOSA) as discussed by the authors is a metal oxide surge-arrester that consists of ZnO non-linear elements and has been taking the place of the conventional gapped arresters on a world-wide scale.
Abstract: The MOSA (Metal Oxide Surge Arrestor) comprising ZnO non-linear elements has been taking the place of the conventional gapped arresters on a world-wide scale. The ZnO non-linear element was developed in Japan and the application for the surge arrester was also established in Japan for the first time. Since the first completion of MOSA in 1975, many improvements have been made in the characteristics of the ZnO element, such as life characteristics, nonlinearity, and energy absorption capability. Especially the improvement of life characteristics against continuous ac voltage stress has been significant. In the design of MOSA, thermal stability should be studied carefully in addition to the characteristics of the ZnO element itself. This paper outlines the development of MOSA, the basic characteristics of the ZnO element, and its application as MOSA.
TL;DR: In this paper, the authors studied the electric stress distribution within dielectric cavities using the finite element numerical technique and found that the amount of stress enchancement and the electric field distribution within the cavities are significantly influenced by the dielectrics permittivity, the dimensions of the cavity, the number of cavities in series, the cavity orientation, and the shape of the electrodes.
Abstract: Electric stress distribution within dielectric cavities are studied using the finite-element numerical technique. The results indicate that the electric stress is enhanced within a gas-filled cavity embedded in the dielectric. The amount of stress enchancement and the electric field distribution within the dielectric are significantly influenced by the dielectric permittivity, the dimensions of the cavity, the number of cavities in series within the dielectric gap, the cavity orientation, the dielectric thickness (electrode spacing), the contour of the edge of the electrodes, and the presence of floating electrodes near electrode edges. The effect of various parameters on the stress distribution within a dielectric is important in the design, fabrication, and testing of devices made of multi-layered dielectric/electrode film structures.
TL;DR: In this paper, a tetrafluoroethylene-perfluoroalkylvinylether copolymer membrane is used to separate H2 CO, CH4, C2H2, C 2H4, and C2HO6 from transformer oil.
Abstract: A diagnostic apparatus for detecting gases dissolved in transformer oil is described, in which a tetrafluoroethylene-perfluoroalkylvinylether copolymer membrane is used to separate H2 CO, CH4, C2H2, C2H4, and C2H6 from the oil. These gases are detected with a new gas detector, which consists of a catalytic gas sensor and a gas chromatograph using air as the carrier gas. Using the gas concentration, the apparatus automatically determines whether a transformer is operating normally or not and, in the latter case, what kind of fault may have occurred. By the above diagnostic apparatus, a transformer could be diagnosed simply and inexpensively. This apparatus should prove useful for identifying what kind of fault may have occurred.
TL;DR: In this paper, the authors present the most significant results of multi-year research carried out in order to evaluate the thermal endurance properties of insulating materials and propose new procedures which allow a single thermal endurance graph to be obtained, even when many properties are measured to evaluate aging.
Abstract: This paper presents the most significant results of multiyear research carried out in order to evaluate the thermal endurance properties of insulating materials. The thermal life model, proposed by Dakin, has been analyzed and compared with the experimental data; the importance of the selection of properties and their end points (failure criteria) on the shape and location of the thermal endurance graph, has been emphasized and new procedures have been proposed which allow a single thermal endurance graph to be obtained (even when many properties are measured to evaluate aging) and lower test temperatures to be used (without prolonging the test time). By these procedures a reliable and objective value of the temperature index can be determined even though the thermal endurance graph is not linear; this is particularly useful for comparing insulating materials. The experimental results reported in the paper are pertinent to thermosetting and composite materials, which have been exhaustively investigated.
Journal Article•
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TL;DR: In this article, the authors present topics in power capacitor advancement and a technical overview of power capacitors used today in Japan, including improvements and developments of dielectric materials and their applications, including improvement of insulating oils, development of new insulating oil, and introduction of polypropylene films.
Abstract: About 50 years have now passed since the time when mineral oil impregnated capacitors of high reliability became economically available, and during which power capacitors have undergone great strides of progress and advancement in dielectric properties, reliability, increase of capacitance, reduction of size and weight, etc. These owe much to the improvements and developments of dielectric materials and their applications, including improvement of insulating oils, development of new insulating oils, and introduction of polypropylene films. This paper presents topics in power capacitor advancement and a technical overview of power capacitors used today in Japan.
TL;DR: In this article, the authors describe aspects of research on dielectrics and electrets carried out by the author over the last 50 years, in an attempt to show the systematics of its development and logical relation between its successive steps.
Abstract: Part 1 of this paper describes aspects of research on dielectrics and electrets carried out by the author over the last 50 years, in an attempt to show the systematics of its development and logical relation between its successive steps. Starting with dielectric absorption, it covers open-circuit behavior of dielectrics, thermally stimulated currents, Paschen breakdown and its effects on the performance of the inductionplate method, and the superposition of free surface charge and dielectric volume polarization. The two-charge theory appears as the result of a straightforward application of the basic charge-and-field equations of electrostatics, without the introduction of a specific model. Theoretical results are developed on the basis of simple experiments, most of them performed with Carnauba wax. Part 2 reviews theoretical aspects of isothermal and thermally activated dielectric relaxation. It includes the theory of the dielectric relaxation function and its interpretation in terms of distributions of natural frequencies or of activation energies, establishment of universal expressions for the relaxation function related with the theory of cooperative processes, theories based on the diffusion equation and normal modes, and the failure of the theory of equivalence during thermally stimulated transients.
TL;DR: In this paper, the effects of collision ionization on high-field conduction and the pre-breakdown current due to the thermal breakdown are described in regard to pre breakdown currents.
Abstract: Electrical conduction as well as breakdown in insulating polymers has been extensively investigated for these decades by many authors in Japan. This report deals only with several recent topics because of space limitations. They are (1) per-breakdown currents, (2) interfacial phenomena, (3) effects of polymer structures and impurities and (4) behavior of ions at electrodes. The effects of collision ionization on high-field conduction and the pre-breakdown current due to the thermal breakdown are described in regard to pre-breakdown currents. Interfacial phenomena are concerned with the barrier height for electron (or hole) injection, carrier injection from the corona electrode and the behavior of carriers at polymer interfaces. The effects of chemical and physical structures of polymers and impurities upon electrical conduction have also attracted much attention recently. The electrochemical reaction and the effect of ionic space charge are concerned with behavior of ions at electrodes.
TL;DR: In this paper, the results of water treeing aging tests on miniature crosslinked polyethylene cables were presented, where the cables were immersed in water and subjected to HV at frequencies of 600, 400, and 1000 Hz.
Abstract: This paper presents results of water treeing aging tests on miniature crosslinked polyethylene cables. To produce the water trees, the cables were immersed in water and subjected to HV at frequencies of 600, 400, and 1000 Hz. The times to breakdown and ac ramp breakdown voltages after preset times of aging were measured. The effect of temperature cycling was also examined. The ac ramp voltage was found to be a good indicator of the severity of water tree degradation at room temperature as the time to breakdown distributions correlated well with a reduction in the ac ramp breakdown voltage. Temperature cycling of the cables increased the number and the lengths of bow-tie trees compared to room temperature aged cables but decreased the number of vented trees. Correlation between ramp breakdown voltages and times to breakdown was poor for temperature-cycled cables. Microscopic examinations of some of the breakdown channels and possible causes of the different mechanisms of breakdown as the final stage of aging are discussed.