Yoshihide Yokoi

Application of Finite Element Method to Analysis of Induced Current Densities Inside Human Model Exposed to 60-Hz Electric Field

The finite eleiment method(FEM) has been applied bt the analysis of the indiced current densities inside axisyrmtrical h. buman medels. It is assumed in the calculations that those models are made of a biological organism whose corndctivity and permittivity are on the sare order as those of humah body tissues. In the experiments, they are made of wood and insulating material covered with aluminium foil.The finite eleiment method(FEM) has been applied bt the analysis of the indiced current densities inside axisyrmtrical h. buman medels. It is assumed in the calculations that those models are made of a biological organism whose corndctivity and permittivity are on the sare order as those of humah body tissues. In the experiments, they are made of wood and insulating material covered with aluminium foil.

Analysis of 60 Hz magnetic fields near ground level in 187 kV switchyard of a 187/66 kV AC substation

To improve understanding of 60 Hz magnetic field characteristics in AC power substations, a numerical calculation of a 60 Hz magnetic field in the 187 kV switchyard of a 187/66 kV substation in service is conducted by using a simple analytical method. The magnetic field profiles near ground level are calculated for various current conditions, and described in terms of the contour maps of magnetic flux density. Effects of the line and bus current conditions, the bus phasing arrangement, and the line and bus geometrical configuration on the substation magnetic field profiles are also investigated. >

Development of real-time system for simultaneous observation of visual discharges and leakage current on contaminated DC insulators

A novel real-time observation system has been developed. It is capable of simultaneously recording visual partial discharge arcs and leakage currents on insulator surfaces under wet-contaminated conditions during a 2-h test. Since this system uses a video recording system uses a video recording system, the discharges and currents can be reproduced repeatedly even at a slowed-down speed. To permit simultaneous recording and accurate data processing of leakage currents, a personal computer is also employed. It was found that the sampling frequency of 1.0 kHz was satisfactory for the recording of the leakage current. Another function of the computer is to exhibit the contours of insulators to be tested in a dark room so that the locations where the arcs stay can be clearly identified. Tests by the clean fog procedure confirmed the good performance of the system at the time of the design. Some experimental results and the applicability of this system are discussed. >

Analysis of magnetic field profiles in electric blanket users

A theoretical analysis is presented of the magnetic field produced by electric blankets that provide one of the strongest magnetic field exposures among the commonly encountered household sources of power frequency magnetic field. Comparisons between the calculated and measured magnetic fields show that the analytical method based on the Biot-Savart law gives reasonable prediction of magnetic-field exposures associated with an electric blanket use. Experiments with a saline cylinder show that power-frequency magnetic fields penetrate the human body with no significant perturbation, which means that an external current, i.e. a blanket heating element current, is the only source of the magnetic fields in the blanket users body. >

Failure Diagnostic System on Air-Operated Control Valves by Neural Network.

A prototype failure diagnosis system has been developed using neural network technology for the actuator of air-operated valves. Because actual failure data were not easily available, the data of 30 failure patterns were experimentally obtained using more than 10 sensors. The time series of sensor signals are Fourier transformed. The data of the magnitude spectrum, phase difference and others are used as the characteristic parameters in our failure diagnosis. From the data, appropriate information for use in the failure diagnosis was extracted. Furthermore, similarities among the failure characteristics were found by fuzzy clustering and statistical analysis. The new system which we developed consists of plural subnetworks and one main network. Each subnetwork is related to one specific sensor signal, and deals with the magnitude spectra from the sensor signal. The main network makes the final decision according to the outputs from the subnetworks and other data. In our system, the number of network connections can be reduced by approximately 40% without degradation of the recognition capability in comparison with the conventional system which uses only one neural network.

An investigation of DC contamination flashover phenomena of suspension insulators

A description is given of the basic results of an investigation into DC contamination flashover phenomena of suspension insulators. A novel real-time system was developed that was capable of observing the partial discharge arcs visually and the leakage current quantitatively. Insulators were tested and the leakage current was analyzed, with the result that the effectiveness of the system was confirmed.<<ETX>>

Induced Current Density in Foreign Tissue Existing in Homonegeous Tissue of Human Model Exposed to Transmission Line Electric Field

Knowledge of the induced current densities inside humans in electric fields is necessary to predict the possibility of biological effects of electric field on hunans, and to perform the animal tests ,or in vitro experiments. This paper discusses how much the induced currents concentrate in a foreign tissue surrounded by the homogeneous tissue inside a human model.

Selection of Impedances of Glazed Semiconducting Insulators to Prevent Corona Discharge from Insulator String of EHV Transmission Line

A study has been made of how to select the impedances of glazed semiconducting insulators to prevent corona discharges. It is assuned in this paper that the impedances of insulators under discussion are normally distributed about 15 M U . The computer simulation has predicted that, on a 500 kV power line in Japan, a corona-free insulator string can be formed using the insulators whose impedances are restricted between 12 and 18 MT2.