電気学会論文誌A(基礎・材料・共通部門誌)
Online ISSN : 1347-5533
Print ISSN : 0385-4205
ISSN-L : 0385-4205
127 巻, 1 号
選択された号の論文の14件中1~14を表示しています
Special Issue on Technology 2007 : Reviews & Forecasts
Special Issue Review
Special Issue Paper
  • Rudi Kurnianto, Yoshinobu Murakami, Masayuki Nagao, Naohiro Hozumi, Yo ...
    2007 年 127 巻 1 号 p. 29-34
    発行日: 2007年
    公開日: 2007/04/01
    ジャーナル フリー
    A nano-composite material of magnesium oxide (MgO) added to a low-density polyethylene (LDPE) was subjected to electrical tree breakdown investigation. The LDPE without nano-fillers was lower in breakdown voltage than the LDPE added with nano-fillers. The breakdown voltage was increased by increase of nano-filler concentrations in LDPE. This result much coincided with the result on tree inception voltage which was increased when the concentration of filler in LDPE was increased. It is considered that fillers would create such an obstruction to the tree bridging the counter electrode. However, even the tree had bridged the plate electrode; the breakdown was not always immediately to occur. There would be so-called time-lag between “bridging” and “final breakdown”. The time-lag to breakdown was increased with the nano-filler concentrations in LDPE. It is considered that the polymer nano-composites are more resistive against partial discharges than their base material.
Paper
  • Mahmudul Kabir, Masafumi Suzuki, Noboru Yoshimura
    2007 年 127 巻 1 号 p. 35-40
    発行日: 2007年
    公開日: 2007/04/01
    ジャーナル フリー
    Noise absorbing process of Zinc Oxide (ZnO) varistors was analyzed by using equivalent circuit of the sample varistors. Equivalent circuit for the ZnO varistor was proposed by considering the microstructure of a special type of varistor made for the experimental purpose. We considered every grain between the internal electrodes and made an equivalent circuit. The circuit's parameters were determined by PSpice circuit simulator. We regarded a portion of the internal electrode and made a uniform model with a non-uniform model. A dc motor was connected with these models in parallel to investigate the effects of the non-uniformity of the ZnO grains in noise absorbing characteristics of a varistor. Comparing to the uniform model, resonance occurred in the non-uniform model while absorbing noise, and thus the absorption of noise of the model was deteriorated. Transient current was calculated for each grains of these models to investigate the effect the deterioration of noise absorbing characteristics. Localized current was found in the non-uniform model when resonance occurred to absorb transient voltage from our calculations.
  • Hisashi Ishikawa, Katsumi Hattori, Ichiro Takahashi, Yoichi Noda, Tosh ...
    2007 年 127 巻 1 号 p. 41-47
    発行日: 2007年
    公開日: 2007/04/01
    ジャーナル フリー
    The variations of geoelectrical potential differences in Hakuba area, Nagano Prefecture, Japan have been investigated. The noises originated from the DC-driven trains were found to contaminate the natural geoelectrical potential data. The most intense influence of trains occurred when the train was running nearby measuring dipoles. The gradient of the potential was deflected towards the railways and/or the position of the train, exhibiting a certain correlation between the power supply data at substation and the geoelectrical potential data at measuring sites. Extracting the high correlation part (r > 0.7), “idealized” train noise can be computed by the least square method. The reduction of train noise by more than 60 % was achieved by subtracting the idealized noise from observed data.
feedback
Top