IEEJ Transactions on Power and Energy
Online ISSN : 1348-8147
Print ISSN : 0385-4213
ISSN-L : 0385-4213
Volume 138 , Issue 12
Showing 1-13 articles out of 13 articles from the selected issue
  • Shinya Sekizaki, Takuya Yamasaki, Ichiro Nishizaki, Tomohiro Hayashida ...
    2018 Volume 138 Issue 12 Pages 925-938
    Published: December 01, 2018
    Released: December 01, 2018

    This paper develops a novel, effective, and practical decision aid tool for distribution system operators based on a many-objective evolutionary algorithm. Since the distribution network reconfiguration problem in the real world has many objectives including discrete objectives, non-convexity, and severe constraints, the distribution system operators have difficulty in finding a preferred solution by him/her with little effort. To realize an efficient decision making in such a complicated optimization problem, providing alternatives with him/her to be chosen among them is one of practical approaches from the viewpoint of the multi-objective optimization approach. In order to find well-diversified Pareto optimal solutions for the many-objective optimization problem with an unknown Pareto front, we propose novel algorithms specialized for the distribution system reconfiguration problem integrated with a promising many-objective evolutionary algorithm, i.e., non-dominated sorting genetic algorithm III (NSGA-III). The proposed method enables the distribution system operators to find Pareto optimal solutions within a practical computational time and also choose the most preferred solution among them. The developed algorithm is validated using a realistic distribution system model with many nodes, switches including remote switches, and SVRs on multiple feeders.

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  • Hideo Hashimoto, Koh Hashiguchi, Hideki Fukui, Yusaku Ono, Mika Nakato ...
    2018 Volume 138 Issue 12 Pages 939-947
    Published: December 01, 2018
    Released: December 01, 2018

    A biofilm of micro-organisms such as bacteria including Legionella, fungi and algae can sometimes grow very rapidly in the spraying water of cooling tower, and can reduce the heat transfer rate of the cooling tower. Bacterial growth can be reduced or prevented by ozone sterilization method effectively. In application of ozone to cooling system of transformer, it is necessary to control ozone concentration for both sterilizing bacteria and suppressing corrosion during 30 years operation. For this purpose, we used heat exchanger model in which sub ppm ozone containing water was flowed through surface part of Cu tube and Cu fin for three month. We verified that Cu corrosion resistance allows thirty years operation and appropriate ozone concentration was effective to sterilization of micro-organisms including genus Legionella. We also used cooling system model including tower spraying in which sub ppm ozone containing water was flowed and circulated. We clarified ozone dissolution and consumption characteristic of transformer cooling system. We proposed optimum operation mode of ozone supplying as intermittent or continuous ozone supply with high sterilizasion effect according to the seasonal temperature change.

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  • Hisayuki Ohara, Yoshiharu Shumuta
    2018 Volume 138 Issue 12 Pages 948-956
    Published: December 01, 2018
    Released: December 01, 2018

    The purpose of the paper is to clarify the deterioration characteristics of the insulating coating for electrical wire. In order to make a database for the mechanical strength and insulation performance of the insulating coating installed in actual field, existing removal insulating wires are randomly selected and tested based on JIS testing standards. Based on the developed database, the relationships among the mount of insolation, the period of service, and the deterioration performance of the insulating coating are analyzed using appropriate hypothesis testing. As a result, the standard deterioration characteristics with aging are quantified for each insulation coating type of electric wire.

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