Faculty Profiles - KOJIMA Hiroki

Presentations -

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電力系統最適運用システム（IGMS）による機器の更新時期を考慮した最適潮流制御

篠田康生，小島寛樹，早川直樹，花井正広，大久保仁

平成24年電気学会電力・エネルギー部門大会

部分放電メカニズムに基づくGIS中金属異物形状同定手法

小島寛樹，鈴木隆文，早川直樹，花井正広，大久保仁

平成24年電気学会電力・エネルギー部門大会

超電導限流ケーブル（SFCLC）の運転温度を考慮した限流特性の評価

大澤岳士，小島寛樹，早川直樹，花井正広，大久保仁

平成24年電気学会電力・エネルギー部門大会

超電導電力機器におけるサブクール液体窒素の電気絶縁性能

西町誠一郎，小島寛樹，早川直樹，花井正広，大久保仁

平成24年電気学会電力・エネルギー部門大会

Conditioning Characteristics of Multi-Gap Electrode System in Vacuum International conference

H. Kojima, Y. Otake, R. Nishimura, N. Hayakawa, K. Hasegawa, H. Saito, Y. Noda, H. Okubo

25th International Symposium on Discharges and Electrical Insulation in Vacuum 2012.9.3 Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences

Event date： 2012.9

Language：English Presentation type：Oral presentation (general)

Venue：Tomsk Country：Russian Federation

In order to clarify the characteristics of spark conditioning carried out in parallel at several parts of electrodes, we carried out conditioning experiment to use a multi-gap electrode system with multi-rod electrodes. As a result, we found that 50% breakdown voltage after conditioning saturation differed in the multi-gap electrode system from in a single gap electrode system. In addition, we found the different process to enhance the breakdown voltage in each electrode, by comparison to the single gap electrode system. © 2012 IEEE.

DOI： 10.1109/DEIV.2012.6412439

Scopus

Other Link： https://www.webofscience.com/wos/woscc/full-record/WOS:000315985400006

Development Process of Impulse Surface Discharge in Vacuum International conference

Y. Nakano, H. Kojima, N. Hayakawa, K. Tsuchiya, H. Okubo

25th International Symposium on Discharges and Electrical Insulation in Vacuum 2012.9.4 Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences

Event date： 2012.9

Language：English Presentation type：Poster presentation

Venue：Tomsk Country：Russian Federation

We investigated the charge activity on alumina dielectrics in the development process of impulse surface discharge in vacuum. We clarified the charge activity in pre-discharge stage by ultra-high speed and high sensitivity measurement. We also measured the fast-framing images of surface flashover propagation synchronously with current waveforms. We found that the charge activities are classified into three stages, i.e. (I) pre-discharge, (II) surface flashover initiation, and (III) expansion, in the development process of surface discharge in vacuum. © 2012 IEEE.

DOI： 10.1109/DEIV.2012.6412467

Scopus

Other Link： https://www.webofscience.com/wos/woscc/full-record/WOS:000315985400034

Charge Behavior and Partial Discharge Characteristics on Alumina Insulation under AC Voltage Application in Vacuum International conference

H. Kojima, M. Ishida, N. Hayakawa, M. Hanai, M. Homma, T. Shioiri, H. Okubo

25th International Symposium on Discharges and Electrical Insulation in Vacuum 2012.9.4 Institute of High Current Electronics, Siberian Branch of the Russian Academy of Sciences

Event date： 2012.9

Language：English Presentation type：Poster presentation

Venue：Tomsk Country：Russian Federation

The charge behavior and partial discharge characteristics, which is not breakdown but has a potential to lead breakdown, at solid-composite system in vacuum can be a critical issue to be investigated, under ac operating voltage application. We investigate the partial discharge along an insulator surface in vacuum under AC voltage application by the measurement of the charging and the light emission. Under sudden AC high voltage application, the partial discharge along the alumina surface occurred at the peak voltage of the negative polarity. The partial discharge was initiated near the rod electrode and spread out over the whole alumina surface. By the analysis of electric field, the partial discharge and subsequent charging behavior on the alumina surface under AC voltage application was verified to be dominated by the distortion of electric field due to the negative charges accumulated on the alumina surface, and this distortion occurs at the period of decrease of negative applied voltage. © 2012 IEEE.

DOI： 10.1109/DEIV.2012.6412452

Scopus

Other Link： https://www.webofscience.com/wos/woscc/full-record/WOS:000315985400019

Introduction Effect of Superconducting Power Flow Controller and Fault Current Limiter (SPFCL) in an Electric Power System

N. Hayakawa, X. Mao, H. Kojima, M. Hanai, N. Kashima, S. Nagaya, S. Sugimoto, H. Okubo

2012.6.22

Charge Behavior in Palm Fatty Acid Ester Oil (PFAE) / Pressboard Composite Insulation System under Voltage Application International conference

H. Kojima, N. Hayakawa, K. Kato, H. Okubo, K. Kawanishi, H. Koide

2012 IEEE International Symposium on Electrical Insulation 2012.6.12 IEEE Dielectrics and Electrical Insulation Society

Event date： 2012.6

Language：English Presentation type：Oral presentation (general)

Venue：San Juan Country：Puerto Rico

Palm Fatty Acid Ester Oil (PFAE) is one of the most promising environment-friendly biodegradable insulating oils for transformers. PFAE has significant advantages compared to other vegetable origin insulating oils and mineral oil, e.g. not only good insulation performance, high permittivity and high moisture tolerance, but also excellent cooling ability due to low kinematic viscosity, high thermal and chemical stability and high productivity. However, since the molecular content of PFAE is quite different from mineral oil, the fundamental charge behavior in PFAE has not been clarified yet. To clarify the temporal and spatial charge behavior in PFAE, we directly measured the electric field in oil duct model with PFAE / pressboard (PB) composite insulation system under dc voltage application and charged flow condition by using Kerr electrooptic field measurement technique. By the comparison of electric field and charge behavior characteristics with fresh and degraded mineral oil, we revealed that the essential mechanism of charge behavior is similar, but the difference in temporal and spatial characteristics is attributed to the higher intrinsic ion density and higher permittivity of PFAE than that of mineral oil.

DOI： 10.1109/ELINSL.2012.6251502

Scopus

CiNii Research

Other Link： https://www.webofscience.com/wos/woscc/full-record/WOS:000309221800085

真空中平行平板電極系におけるインパルスコンディショニングのギャップ長依存性

西村亮岐，小島寛樹，早川直樹，大久保仁

平成24年電気学会全国大会