Haruo Ihori

Electrooptic Measurement of Three-Dimensional Nonuniform Electric Field Mapping in Nitrobenzene

An electrooptic method is useful for measuring electric fields without disturbing them. Our investigations have been concerned with measurements of electric field distribution. Three-dimensional nonuniform electric field distributions were measured in nitrobenzene using the Kerr electrooptic measurement. The field distributions to be measured were produced in a sphere-to-sphere electrode system. The optical system consisted of a He–Ne laser, a polarizer, a quarter-wave plate, an experimental cell, an analyzer, and a photodetector. When a negative high voltage pulse was applied to the electrode system, the light intensity transmitted to the analyzer was measured using the photodetector. Intensity measurements were carried out at many points from θ= 0 to π around the electrode system. From the data obtained, the electric field distribution, i.e., the strength and direction of each electric field vector in the measured plane, was reconstructed using a computed tomography (CT) technique. The measured distributions were compared with the theoretical ones calculated using an analytical method.

Measurement of Nonsymmetrical Electric Field Vector Distribution in Nitrobenzene Using Electrooptic Method

The three-dimensional nonuniform electric field vector distribution was measured in a nonsymmetrical electrode system using the Kerr electrooptic effect with the reconstruction technique modified by computed tomography (CT). The intensity of the light transmitted through a dielectric liquid in nonuniform field was detected at many points on one plane. It was found that the nonuniform electric field in the liquid can be measured three-dimensionally and visualized.

Three-Dimensional Electric Field Vector Measurements in Nitrobenzene Using Kerr Effect

We have been investigating a nonuniform electric field measurement method in dielectric liquids using the Kerr electrooptic effect. Three-dimensional electric field vectors were measured as the first step in determining the three-dimensional nonuniform electric field distributions. The electric field vector to be measured was produced in a pair of inclined parallel-plane electrodes. Negative high-voltage pulses were applied to the electrode system. Nitrobenzene with large Kerr constant was used in the experiments. A He-Ne laser beam passed through nitrobenzene between the electrodes along two different orthogonal directions. The magnitude and the direction of the electric field vector were calculated from the light intensity measured by a photodiode. Maximum errors of measured electric field strength and direction were 9.3% and 4.3°, respectively.

Two-Dimensional Kerr Electrooptic Measurement of Nonuniform Electric Fields by CT Method

It is very difficult to measure nonuniform electric field distributions in insulators. The optical measurements of the electric field were investigated in nitrobenzene using the Kerr effect. A sphere-to-sphere electrode or a sphere-to-plane electrode system was used to produce the nonuniform electric field. A rectangular test cell was made of teflon with two glass windows. A He-Ne laser was used for a light source. The intensity of the light transmitted through the cell was measured with a photodiode. The two-dimensional electric field distribution expressed in absolute value was reconstructed by the computed tomography (CT) method. The measured electric fields were compared with the theoretical one and good agreement was obtained.

Calculation of the Three-Dimensional Field Vectors in Dielectrics

We have developed a culculation method of the applied electric field in a dielectric by measuring the difference in the output light intensity. At present, the direction of each applied field can be calculated when the dielectric is divided into four cells in which the applied fields are the same in intensity but differ in direction. Firstly, this paper shows how to determine the applied field intensity and direction when the electric field is applied to only one dielectric cell. Secondly, the method of numerical calculation of the applied field is described applying the method for one cell to a case where the dielectric is divided into two cells in which the intensity of the applied field is known but the direction is unknown. Finally, by extending the case of two cells, the flow of the numerical analysis and its result are described when the dielectric is divided into four cells under the same conditions as those for the two-cell case.

Electrooptic measurement of non-symmetrical electric field distribution in a dielectric liquid

We carried out the measurement of the three-dimensional nonuniform electric field distribution in a non-symmetrical electrode system. An optical system was composed of a He-Ne laser, a polarizer, a quarter-wave plate, an experimental cell, an analyzer, and a photo-detector. When a negative high voltage pulse was applied to the electrodes system, the light intensity transmitted to the analyzer was measured by the photo-detector. The intensity measurement was carried out at many points in each direction from 0 to /spl pi/. From the obtained data, the electric field distribution was reconstructed with algebraic reconstruction technique (ART) in computed tomography (CT) technique. The measured distribution was interesting.

Development of electrical trees in two- and three-dimensional silicon rubbers

Although electrical trees in silicon rubbers, silicone rubbers have been observed, AC trees have many small branches and thus it is hard to measure it in 3D. In order to observe the patterns of AC trees, two-dimensional sample is used. The development mode of the tree has been classified into three modes; Just after generating the tree, (i) the AC tree has developed straightly. Then the branches has started and (ii) the envelope of the top of the branches has developed coaxially. When one of the branches reached at some point, (iii) that branch developed faster than others and then breakdown occurred. It is known that trees disappear in silicon rubbers after some hours. Trees in twoor three-dimensional silicon rubbers have been compared. Small branches has disappeared after 24 hours in 3-D sample. In 2-D samples, trees did not disappear as ones in 3-D samples.

A 3-D numerical simulation of partial discharge acoustic wave propagation in a model transformer

In this paper, the authors present a three-dimensional numerical simulation of partial discharge (PD) acoustic wave propagation that has been developed to provide time-domain signal representation in a model transformer. The numerical modeling of acoustic PD data is used to support interpretations of laboratory experimental data and to enhance the understanding of acoustic wave propagation in a structure like the power transformer, and hence PD source location in the same. It is intended that an extension of the work presented here, to account for real transformer geometry and also to visualize the propagation of acoustic wave fronts, will later be compared with field results. The three-dimensional wave equation, given by c/sup 2//spl nabla//sup 2/P=/spl part//sup 2/P//spl part/t/sup 2/, where c is the acoustic velocity and P the pressure wave field, defines an initial value problem and describes time evolution. The goal of the numerical code is to track that time evolution with some desired accuracy taking into consideration the boundary conditions that govern the evolution in time of points on the boundary of the spatial region of interest. This is particularly important for the satisfactory modeling of a complex structure like power transformer. In solving the above equation using the finite-difference method, of particular interest are the conditions of numerical stability. In this paper, the authors apply the stability analysis method originally developed by Von Neumann. The simulation results are in agreement with the results obtained from the laboratory experiments.

Evaluation of space charge in liquid dielectric using kerr electrooptic method

In dielectric liquids subjected to a high electric field, space charges are generated due to various reasons, for example, by the injection of charges from electrodes or by ionization of the impurities and molecules. It is necessary to obtain information regarding the electric field and space charge distributions in insulating materials to ensure effective insulation, however, it is very difficult to obtain information regarding space charge in liquid. We have investigated the electric field distributions in liquid dielectrics using the Kerr elctrooptic effect. Recently, the electric field distribution in the order of milli-seconds has been able to be measured. For 1 ms immediately after an applied voltage, it is thought that space charge layer is almost never formed. So, we measured the electric field distribution for 1ms at the applied voltage. Then, after a period of time, we measured again the electric field distribution at the second application of the voltage pulse. If there is a difference between the two, it is considered that it is caused by remnant electric charges. So, we report on the evaluation of the remnant charge in liquid.

Learning effect of composite conducting polymer

Conducting polymers with fractal patterns have been polymerized electrochemically under some conditions. The pattern of neuron-like conducting polymer has been prepared by controlling the polymerization conditions. Furthermore, the network of neuron-like conducting polymer has been prepared. If this kind of conducting polymer has the properties of learning effect and non-linearity, it works as neuron device. In this article, the method for adding the learning effect to the channel of conducting polymer has been investigated. In conducting polymer gels, the dopant easily moves in or out of conducting polymers in some solvents and in this time the gel swells or shrinks. On the other hand, polypyrrole is stable in such solvents. A composite film of polypyrrole and conducting polymer gel, poly(3-hexylthiophene), has been used to suppress the change of shape of conducting polymer gel. The technique of neural network was used as a method of learning effect. A simple network has been used instead of actual complicated conducting polymer network. It was confirmed that the conductivity of the channel network changed for correspondence to a teacher signal flow.