IEEJ Transactions on Fundamentals and Materials
Online ISSN : 1347-5533
Print ISSN : 0385-4205
ISSN-L : 0385-4205
Volume 136, Issue 9
Displaying 1-15 of 15 articles from this issue
Special Issue on the 46th Symposium on Electrical and Electronic Insulating Materials and Applications in Systems
Special Issue Paper
  • Naoshi Hirai, Yoshimichi Ohki
    2016 Volume 136 Issue 9 Pages 553-560
    Published: September 01, 2016
    Released on J-STAGE: September 01, 2016
    JOURNAL FREE ACCESS

    Electric cables play important roles for supplying power and for transmitting information and control signals. Therefore, their degradation may cause a serious problem. Silicone rubber (SiR) is widely used for electrical insulation in safety-related cables in nuclear power plants. In this paper, the ability of locating a degraded portion in a duplex cable insulated with SiR was compared between a system based on frequency domain reflectometry (FDR) being developed by the authors and a commercially available system called line resonance analysis (LIRA). Reflecting the fact that the FDR system can expand the measurement frequency range, FDR shows a higher sensitivity and a better resolution than LIRA. However, both methods cannot detect the degradation of SiR before its further use becomes uncommendable.

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  • Masahiro Sato, Akiko Kumada, Kunihiko Hidaka, Toshiyuki Hirano, Fumito ...
    2016 Volume 136 Issue 9 Pages 561-567
    Published: September 01, 2016
    Released on J-STAGE: September 01, 2016
    JOURNAL FREE ACCESS

    Degradation process of polymers is correlated with space charge, however there remains a lack of understanding of charge transport phenomena. Thus quantitative estimation of carrier mobility has not yet been accomplished. This is bacause, although charge transfer in solids are quantum mechanical, it has not been treated as such. In this research, hole mobility in crystalline polyethylene (PE) is computed by means of first principles calculation. It turns out that hole transfer in PE occurs in a hopping regime rather than a band regime even for crystalline structure without any structural disorders. In crystalline PE, hole hops between localized states that are created by polaronic effect. In addition, it was shown that hole mobilities in oligomers of PE are smaller by several orders of magnitude than those in naphthalene and anthracene, both due to small electronic coupling between molecules and large reorganization energy. Small electronic coupling and large reorganization energy is the result of σ bonded structure of the hole localized state of PE, which is different from π like structure of most organic semiconductor molecules.

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  • Yuichi Murakami, Yuji Muramoto, Noriyuki Shimizu
    2016 Volume 136 Issue 9 Pages 568-573
    Published: September 01, 2016
    Released on J-STAGE: September 01, 2016
    JOURNAL FREE ACCESS

    We have been investigating the sterilization of liquid food by high electric field pulse. The sample was Escherichia coli (JM103) in aqueous solution of L-Serine, L-Alanine, L-Histidine, L-Glutamic acid, D-Glutamic acid, L-Aspartic acid, K2HPO4, or KH2PO4. High voltage pulse (-4.40 kV) was applied to the each sample at room temperature. As results, the survival rates of L-Glutamic acid, D-Glutamic acid, L-Aspartic acid, K2HPO4, or KH2PO4 samples greatly decrease with the number of applied pulses. On the other hand, the survival rates of L-Serine, L-Alanine, or L-Histidine samples slightly decrease. The experimental results suggest that the survival rate of E. coli by high electric field pulse sterilization is governed the anions or negative charges in aqueous solution.

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  • Takefumi Minakawa, Masaaki Ikeda
    2016 Volume 136 Issue 9 Pages 574-579
    Published: September 01, 2016
    Released on J-STAGE: September 01, 2016
    JOURNAL FREE ACCESS

    Safety-related low voltage cables of nuclear power plants are required to perform their safety functions under anticipated environmental conditions over their service life. Elongation-at-break (EAB) has been used as an indicator for evaluating the degradation level of the polymeric insulation of the cables. This paper describes results of measurement of gel fraction, crystallinity from differential scanning calorimetry and infrared absorbance from attenuated total reflectance Fourier transform infrared spectroscopy for commonly used cable insulation types, cross-linked polyethylene, flame-retardant cross-linked polyethylene and flame-retardant ethylene propylene diene rubber, to investigate the correlation between polymeric molecular structure and EAB. The measurements were conducted following accelerated thermal ageing or concurrent thermal and radiation ageing for each insulation type. As a result, infrared absorbance of carboxylic acid for the concurrently aged insulation showed a clear correlation with EAB while gel content and crystallinity were not clearly related.

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  • Tetsuro Tokoro, Masayuki Nagao, Hiroyuki Iwase
    2016 Volume 136 Issue 9 Pages 580-585
    Published: September 01, 2016
    Released on J-STAGE: September 01, 2016
    JOURNAL FREE ACCESS

    Hydrophobicity of the material surface is one of the most valuable properties, and it is also used as one of the deterioration indices of materials. This surface property changes depending on different parameters, such as temperature, surface roughness, measurement time, etc. In this paper, using silicone rubber and concrete as the samples, the effect of parameters to the evaluation of hydrophobic condition is studied. Based on the results of this research, the deterioration condition or the water absorption condition of the material surfaces were quantitatively evaluated more accurately. By using the quantitative evaluation and the diagnostic techniques, these parameters can improve the reliability of the surface condition evaluation of the materials.

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  • Daigo Komesu, Naoya Matsuoka, Masahiro Kozako, Masayuki Hikita
    2016 Volume 136 Issue 9 Pages 586-591
    Published: September 01, 2016
    Released on J-STAGE: September 01, 2016
    JOURNAL FREE ACCESS

    Characteristics of composite materials of epoxy resin and inorganic particle can be improved thanks to alignment of the particle chains. These chains are formed by applying an electric field during curing process. It is important to form the chains so as to obtain the stable quality. Forming the chains is affected by various factors such as gap length between electrodes, applied electric field and specification of particle including size, gravity, permittivity and content. Therefore, the authors established a simulation method of the particles movement in a liquid under AC electric field to elucidate the effects of these parameters on the formation of the chains. This paper reveals the effects of the parameters on particles movement, and comparison of particles movement between the experiment and the simulation.

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Special Issue Letter
Paper
  • Fei Kong, Hiroki Kojima, Toshinori Kimura, Mitsuru Tsukima, Naoki Haya ...
    2016 Volume 136 Issue 9 Pages 594-602
    Published: September 01, 2016
    Released on J-STAGE: September 01, 2016
    JOURNAL FREE ACCESS

    In order to develop higher-voltage vacuum circuit breakers (VCB), the investigation of discharge phenomenon in vacuum is necessary. In vacuum interrupters (VI) with composite insulation systems, the discharge has complex and various patterns at the internal insulation failures. In this paper, based on the discharge development characteristics, we propose a discrimination method for the discharge pattern in vacuum. We measured the applied voltage, anode current, and shield potential waveforms, respectively. From the feature of the measured waveforms, we classified the discharge patterns. Furthermore, based on the relation between discharge development time and discharge path length, we estimated the discharge patterns and discharge path lengths. In addition, we conducted a verification experiment of the discrimination method using a VI model. Experimental results revealed that the estimated discharge patterns and discharge path lengths were consistent with the observed discharge ones and the effectiveness of the discrimination method was confirmed.

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  • Tomoyuki Izutsu, Daisuke Odaka, Takuya Kozai, Marina Komatsu, Yoshimic ...
    2016 Volume 136 Issue 9 Pages 603-608
    Published: September 01, 2016
    Released on J-STAGE: September 01, 2016
    JOURNAL FREE ACCESS

    Overheating during the manufacturing process of a cross-linked polyethylene-insulated cable often induces brownish resin, which may become a starting point of breakdown and water trees. In this study, an XLPE sheet was overheated and cut to many pieces of squares with various sizes from 0.5×0.5 to 10×10 mm2. Then, each piece was sandwiched between two sheets of low-density polyethylene and its absorption intensity was measured at terahertz (THz) frequencies. Furthermore, the spatial distribution of absorption was measured in the form of a two-dimensional image by scanning the sample. As a result, it has become clear that the whole absorption increases in a range from 0.5 to 5.0 THz when the volume of overheated part becomes bigger. Moreover, the distribution of overheated parts can be visualized by the THz absorption imaging.

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Letter
 
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