Surface discharge is one of the main phenomena in the fault of electric apparatus, but is not cleared yet. The electric field measurement in and around a corona streamer while the surface discharge creeps is greatly helpful for analyzing it. There is optical measurement technique for electric fields by using Pockels crystal, and an optical waveguide technique has been successfully introduced to miniaturize the sensors. The electric field measurement just under the surface discharge is tried with the optical waveguide Pockels sensor installed on a PMMA plate and output signals according to its development are obtained.

View full abstract

The discharge characteristics of a ring dielectric line surface wave processing plasma (RDL-SWP) apparatus have been studied on the basis of numerical simulations and experimental measurements. For the simulation of an electromagnetic wave in the RDL-SWP, the three-dimensional computer code has been developed for a cylindrical plasma chamber configuration with the Cartesian coordinates that facilitate the simulation in a rectangular wave guide placed on the chamber. The finite difference time domain (FDTD) method is used in this code to calculate Maxwell equations. Experimentally, for Ar gas the distributions of electron density and electron temperature were measured using a movable single probe and the optical emission patterns were observed. It was found that the peak points of the distributions of the electron density are nearly the same points where the optical intense emission takes place. For the distributions of the bulk plasma with the density higher than the cut-off density, the effect of the diffusion seems to be more dominant than the localization of surface plasma produced by the surface wave. By the comparison between the results of simulation and those of experiments, the applicability and the limitation of the plasma model with a fixed uniform electron density is evaluated.

View full abstract

A new estimation method of partial discharge onset conditions in gas around a triple junction is proposed. The availability of the method based on the Paschen curve and the potential distribution along interface between a solid insulator and gas is confirmed experimentally in atmospheric air at room temperature. The partial discharge onset conditions in air and SF₆ gas under different pressures at room temperature and in cryogenic nitrogen and helium gases at saturated temperatures under atmospheric pressure are estimated. The partial discharge intensity is discussed on the basis of the proposed method.

View full abstract

This paper proposes a new numerical deconvolution algorithm, which has advantage in speed over other two techniques. In the paper, three basic algorithms have been examined to analyse standard lightning impulse voltage from the given output response and unit step response of a measuring system. Full and front-chopped impulses are assumed as an input voltage. The numerically reconstructed inputs are compared with the analytical impulses. The proposed fast method, not precise enough under certain circumstances, is studied a cause of its error and its algorithm is modified to avoid cancellation error. The modified deconvolution method has been tested in possible circumstances and proven most accurate amongst three.

View full abstract

This paper presents the fundamental surge phenomenon when a step voltage is applied to a horizontal line above the ground which has branch feeders. We study line current and voltage at joint with the moment method that calculates electromagnetic field in frequency domain. It is widely noted that the current reflection factor changes to a third at the junction of same three lines in conventional transmission line theory based on TEM wave, and the stepwise current reflected appears overlapping to the incident current. On the other hand, the reflected current from the joint shows the inductive characteristic or the capacitive one depending on the angle between lines, which varies gradually and not stepwise in our numerical analysis considering TM wave. The time characteristic of the voltage at joint depends on the angles also, and the peak voltage is slightly large compared with the voltage by the transmission line theory. These phenomena are caused by the electromagnetic coupling between the main line and branch lines. In addition to the computer simulations, we measured the currents in the miniaturized model lines and the results make the validity of our analysis clear about changes of the reflected current depending on the angles.

View full abstract

This paper propose a method which stereoscopic image is easily observable. It can present the stereoscopic image by holographic screen is attached on a usual display of incoherent light source, such as the monitor of personal computers or televisions. In order to realize this purpose, we think that the screen which combine a holographic optical element and a Venetian blind is effective. The authors describe the principle of this stereoscopic display and the design procedures of Venetian blind and holographic optical element, and examine that they play an important part in stereoscopy. We examined Bragg conditions for a 3-dimensional system recording HOE, and analyzed reconstraction characteristic of the holographic optical element.

View full abstract

Exhaust gas treatment technologies by non-thermal plasmas have been investigated so far, however the mutual comparison of these technologies has not always been done in the papers. One of the reasons is that there are no proper standards for comparison on both application and performances. This paper is discussing applicability of the processes and also the way of comparison of NO_x removal performances. The important issues are that R-W(=P/(Q·Co)) curve and R-η curve are very adequate as comparison standards. Items that have to be considered at application are also described.

View full abstract

The hydrogen barrier effect of SrRuO₃(SRO) top electrode in SrBi₂Ta₂O₉(SBT) ferroelectric capacitors was investigated. Both the SRO(270nm) and SBT(250nm) thin films were prepared by pulsed laser deposition. The remnant polarization of SRO/SBT/Pt capacitor was kept to be 8 μ C/cm² after 3%H₂/He treatment even at 400°C for 10min. Moreover, after annealing at 200°C for 10min in 3%H₂, the remnant polarization during 10¹⁰ switching cycles was nearly constant. These results indicate that the SRO top electrode works as a hydrogen barrier. In case of Pt/SBT/Pt capacitor, x-ray diffraction peaks of SBT thin films disappeared after the H₂ treatment even at 200°C for 20 hours. On the other hard, deffraction peak intensities of both SRO and SBT thin films in SRO/SBT/Pt capacitor remained the same after H₂ treatment. The SRO top electrode is very attractive for highly integrated ferroelectrice nonvolatile memory applications.

View full abstract

Zinc oxide (ZnO) having a wide direct band gap of 3.37 eV at room temperature (RT) may be a new potential candidate for optoelectronic devices such as ultraviolet (UV) laser, blue light-emitting diode and phosphorescent display. We have studied the ZnO thin films deposited by pulsed laser ablation (PLA) method. In order to prepare high quality ZnO thin films, the spectroscopic properties of the plasma plume produced during film deposition were investigated to correlate the properties of the deposited film with plasma characteristics. Furthermore, we have deposited the ZnO thin films at various deposition conditions such as ambient oxygen gas pressure, substrate material and substrate temperature. We have investigated the effect of deposition conditions on structural and optical properties of the ZnO thin films. X-ray diffraction, atomic force microscopy, UV-visible photometry and photoluminescence measurements were used to characterize the grown films. The ZnO thin films deposited at ambient oxygen gas pressure of 5 mTorr and substrate temperature of 550°C showed highly c-axis (002) orientation. The ZnO thin film deposited on Al₂O₃ (0001) at these deposition conditions provided the UV stimulated emission around 395 nm.

View full abstract

Dissolved water in insulating liquid had been regarded as a kind of impurities that deteriorates electrical property. Recently, the state and the behavior of water molecules in liquid were measured by IR method. And it comes to be able to be analyzed where water molecules bond with dielectric molecule and how many molecules gather around polar base, among the alkyl chain. In the case of transformer oil, which almost consists of saturated hydrocarbon, oxidation products gradually increase by aging during the practical use. And oxidation compounds include the polar base such as carbonyl base and ketonic base. When water dissolves in such oil, water molecules interact with those polar base and form water cluster, which can make conductivity increase. In this paper, partially oxide hydrocarbon was mixed in saturated hydrocarbon. And the effect of water cluster around the ketonic base on the conductivity was discussed. As a result, when the ratio of oxide compounds was less than 10%, conductivity didn’t increase with increase of water. But the ratio became over 10%, specific water cluster increase conductivity. It was appeared hat the specific cluster consist of water molecules gather around one ketonic base.

View full abstract

We propose an algorithm of analytical measurement which can separate conductive and dry-band arc components of leakage current flowing on the surface of polymer insulating materials according to the waveform distortion considered. The waveform distortion gives useful information to distinguish discharge types and evaluate the degree of degradation of the polymer surface. We have also developed a measurement system capable of separating the leakage current into the two components. We confirmed effectiveness of the measurement system by applying it to an artificial aging test based on Rotating Wheel Dip Test method.

View full abstract