Details of a Researcher - SAKODA Tatsuya

Basic Study on Partial Discharge Location for Cross-bonding Cables

Kitajima Junichi, Sakoda Tatsuya, Watanabe Kiyonori

IEEJ Transactions on Fundamentals and Materials 134 ( 6 ) 428 - 429 2014

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

To locate partial discharges (PDs) in cross-bonding cables where current pulses due to PDs might be divided, we paid attention to phases of current pulses obtained by six CT sensors arranged at both sides of 3-phase of the cables. The accuracy of PD location, obtained by using time difference between arrival times of current pulses from specified phase, was relatively high even for cross-bonding cables.

DOI： 10.1541/ieejfms.134.428

Characteristics of an Underwater Plasma Source with a Porous Glass Membrane

Shiomitsu Eiichi, Sakoda Tatsuya

IEEJ Transactions on Fundamentals and Materials 134 ( 5 ) 321 - 326 2014

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Advanced oxidation process (AOP) with hydroxyl radicals (OH) is considered to be useful for water purification through oxidation; therefore, we proposed an underwater plasma source with a porous glass membrane which functioned in bubble supply and the formation of micro-discharges. We observed bubble formation and light emission from discharge on the surface of the membrane using a high-speed camera and a spectroscope, respectively. Additionally, dependence of gas pressure on generation of OH radical and decomposition of recalcitrant organic matter were examined. The obtained results showed that AOP might be more effective when the operating gas pressure was set higher than a pressure which could form bubbles.

DOI： 10.1541/ieejfms.134.321

Study on Deterioration Factors of an Electric Double-layer Capacitor

Yoshitama Hiromu, Haruta Atsuji, Tashima Daisuke, Sakoda Tatsuya, Hayashi Noriyuki

IEEJ Transactions on Fundamentals and Materials 134 ( 10 ) 525 - 531 2014

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Electric double-layer capacitors (EDLCs) have the advantages of much longer life and unnecessary maintenance. However, for EDLCs used for a long period, a decrease of electrostatic capacity and an increase in internal resistance are recognized. In this study, in order to clarify the factors responsible for the deterioration of EDLCs used for a long period, chemical analysis was conducted on each component such as an activated carbon electrode and an electrolytes solution. The obtained data were compared with those from a new EDLC. The results showed that long-term use reduced electrostatic capacity about 5% and made internal resistance increase by about 1.7 times. The quantity of oxygen due to surface functional groups of the activated carbon electrode was confirmed using electron spectroscopy for chemical analysis (ESCA). As compared with results obtained from a new EDLC, long-term use made the ratio of O-C=O deriving from carboxyl group (-COOH) to C-C increase 1.2 times. The ratio of C-O deriving from hydroxyl group (-OH) to C-C also increased 1.4 times. In addition, it was found that BET surface area decreased about 40% and that pores whose diameter was in the range between 0.8 to 20 nm disappeared.

DOI： 10.1541/ieejfms.134.525

Influence on Bleaching Characteristics by Different Discharge Form for a Passing Water-type Ozonizer

Shiomitsu Eiichi, Ariyoshi Junya, Fuji Shinsuke, Sakoda Tatsuya, Kijima Junji, Nakashima Hideyuki

IEEJ Transactions on Fundamentals and Materials 133 ( 11 ) 606 - 607 2013.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Advanced oxidation process (AOP) with hydroxyl radicals (OH) is considered to be useful for water purification through oxidation; therefore, we proposed a useful passing water-type ozonizer, which could generate discharges even on the liquid surface. We first observed optical emissions due to the discharges and then confirmed the existence of O and OH radicals. Next, decomposition of Methylene Blue was examined. When the discharge was generated between a glass electrode and liquid, the AOP was achieved. The obtained results also indicated that various decomposition and treatment would be possible by selecting discharge form for our passing water-type ozonizer.

DOI： 10.1541/ieejfms.133.606

Influence of triple-junction on sparkover voltage for a series gap of arrester

通水型オゾナイザの放電形態が脱色特性に与える影響 Reviewed

塩満栄一, 有吉純也, 藤真介, 迫田達也, 貴島純次, 中島秀之

電気学会論文誌A 133 ( 11 ) 606 - 607 2013.11

Language：Japanese Publishing type：Research paper (scientific journal)

Tokunaga T., Nishikawa S., Sakoda T., Fukano T.

2013 IEEE Electrical Insulation Conference, EIC 2013 110 - 113 2013.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：2013 IEEE Electrical Insulation Conference, EIC 2013

Considering the latest development of advanced information society, a stable supply of electric power should be maintained. Lightning surge arrester can contribute to reduce electric failures due to overvoltage from lightning. Since 1970's, zinc oxide (ZnO) element with superior non-linear voltage (V) - current (I) characteristics has been widely installed. Even in Japan, the surge arrester with a series gap has been installed to distribution systems for reducing the electrical failures. As mentioned above, the ZnO element has a superior nonlinearity of V-I characteristic, which can achieve suppress of overvoltage energy. Furthermore, the ZnO surge arrester with a series gap can interrupt the following current, immediately. The surge arrester with a series gap is composed of a simple gap electrode, a ceramic spacer for fixing the gap of the electrodes, and ZnO elements. The upper and the bottom of the ceramic spacer face metallic electrodes; therefore there are triple-junction points between the ceramic spacer, the metallic electrode, and gas. It is well known that electric field strength near the triple-junction point becomes high because of a triple-junction effect. It is also considered that the triple-junction point becomes a source of primary electrons by field emission due to the high electric field. Therefore, the triple-junction effect may influence the discharge characteristics so that the investigation will contribute to the further stable operation of a surge arrester with a series gap. In this study, we carried out experiments concerning how the triple-junction effect influences discharge characteristics such as breakdown voltage and discharge ignition. We first varied the distance between the discharge axis and the triple-junction point and then evaluated the discharge ignition time. Additionally, several ceramic materials with various relative permittivity were used. Based on the results, we evaluated the optimum distance between the discharge axis and the triple-junction point, which would be useful for design of a surge arrester with a series gap. © 2013 IEEE.

DOI： 10.1109/EIC.2013.6554214

Evaluation of Discharge Ignition by Composite Pollution Test with Silicone Rubber

OSHIKAWA Norihito, TOKUNAGA Tatsuya, HONDA Kazufumi, MIYAKE Takuma, SAKODA Tatsuya, ANJIKI Tomikazu

IEEJ Transactions on Fundamentals and Materials 133 ( 4 ) 205 - 210 2013.5

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Application of polymeric materials for electric power apparatus is spreading worldwide. However, the aged deterioration is anxious because of dry band arc discharges generated on the surface of the polymer materials. In this paper, we carried out composite pollution tests and measured the discharge ignition time of silicone rubber. The results showed that there was no large difference in the discharge ignition times obtained between ac and dc voltage applications. Additionally, it was shown that the difference of the discharge ignition was influenced by hygroscopic property of the pollution material.

DOI： 10.1541/ieejfms.133.205