Faculty Profiles - KOJIMA Hiroki

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高温超電導限流変圧器（HTc-SFCLT）用YBCO並列導体の限流特性

大村弘輝，伊藤智志，小島寛樹，早川直樹，遠藤奎将，大久保仁

平成20年電気学会全国大会

電力システムの総合経済性を考慮した変圧器の最適保守方法

金光正樹，塩見僚，小島寛樹，早川直樹，遠藤奎将，大久保仁

平成20年電気学会全国大会

SF₆ガス中における金属異物の部分放電電流パルスおよび電磁波特性に関する検討

西澤佳奈子，大楠崇司，小島寛樹，早川直樹，遠藤奎将，吉田昌展，内田克己，大久保仁

平成20年電気学会全国大会

SF₆ガス中リーダ放電進展に及ぼす解離生成物の影響

吉田聡，細井勇佑，小島寛樹，早川直樹，遠藤奎将，大久保仁

平成20年電気学会全国大会

Novel Measurement and Analysis System for Investigation of Partial Discharge Mechanism in SF₆ Gas International conference

H. Kojima, N. Hayakawa, F. Endo, H. Okubo

12th International Middle-East Power System Conference 2008.3.13 South Valley University

Event date： 2008.3

Language：English Presentation type：Oral presentation (general)

Venue：Aswan Country：Egypt

An understanding of mechanism of partial discharge (PD) in SF6 gas is critical for diagnosis of PD in electric power equipment and contributes to the optimization of the design of electric power applications. However, for complexity of PD characteristics under non-uniform electric field, the mechanism of PD in SF6 is not comprehended enough. For this reason, we aim to reveal the PD mechanism by measuring current waveform, propagation characteristics and light emission of PD in SF6 gas and analyzing these data. For this purpose, we have developed excellent measurement and analysis techniques. For an analysis of PD under ac voltage application, not only PD waveforms but also PD propagation property is essential. We have constructed partial discharge current pulse waveform analysis (PD-CPWA) system. This system has enabled us to observe PD current sequentially at high speed and analyze the propagation of PD current pulse statistically. By the application of PD-CPWA system to diagnosis of PD activity due to the metallic particle in SF6, we could identify the particle type and size. On the other hand, for an analysis of PD under impulse voltage application, an ultra high-speed PD measurement by various methods is extremely important. In order to investigate the impulse PD mechanism spatially and temporally, the simultaneous measurement of current and light emission intensity waveforms, streak and still light emission images and temporal evolution of spectrum of PD light emission have been carried out. By using this synchronous ultra-high speed PD measurement system, we revealed the change of light emission from decomposition products depending on the step propagation of leader discharge. © 2008 IEEE.

DOI： 10.1109/MEPCON.2008.4562383

Scopus

Other Link： https://www.webofscience.com/wos/woscc/full-record/WOS:000259262500089

Comparison of Partial Discharge Characteristics for Different Defect Types in SF₆ Gas Insulation System International conference

D. A. Mansour, T. Okusu, K. Nishizawa, H. Kojima, N. Hayakawa, F. Endo, H. Okubo

12th International Middle-East Power System Conference 2008.3.13 South Valley University

Event date： 2008.3

Language：English Presentation type：Oral presentation (general)

Venue：Aswan Country：Egypt

The high reliability, less maintenance and compact size of Gas Insulated Switchgears (GISs) have made them the primary choice for many utilities. However, sometimes insulation defects inside GIS can be a serious threat to safe operation of GIS and can lead to costly disruption of supply. As insulation failure usually starts with partial discharge (PD) activity, this paper investigates the differences in PD characteristics in SF6 gas among different types of defects. The defect types considered in this study are particles in a gas gap, particles adhered on a spacer surface and spacer/electrode detachment. Different experiments were made for sequential PD measurements using the system of PD-Current Pulse Waveform Analysis (PD-CPWA). The PD phase characteristics, PD pulse number and PD current were analyzed for the different defect types. Also the ratio of voltage increment to phase increment at the next PD pulse appearance (Δu/ΔΦ pattern) was obtained and compared for each defect type. Experimental results show that correct identification of defects can be achieved based on considered PD characteristics. © 2008 IEEE.

DOI： 10.1109/MEPCON.2008.4562335

Scopus

Other Link： https://www.webofscience.com/wos/woscc/full-record/WOS:000259262500041

機器信頼性に基づく電力システムの保守・運用の最適化

金光正樹，塩見僚，小島寛樹，早川直樹，遠藤奎将，大久保仁

電気学会誘電・絶縁材料/電線・ケーブル合同研究会 2008.2.19 電気学会誘電・絶縁材料/電線・ケーブル技術委員会

Variation of Light Emission Spectrum Depending on Partial Discharge Propagation in SF₆ Gas

S. Yoshida, H. Kojima, N. Hayakawa, F. Endo, H. Okubo

2007.11.26

Self-recovery Characteristics of High-Tc Superconducting Fault Current Limiting Transformer (HTc-SFCLT) with 2G Coated Conductors International coauthorship

S. Ito, H. Kojima, N. Hayakawa, F. Endo, M. Noe, H. Okubo

International Symposium on EcoTopia Science 2007

Optimum Operation and Maintenance of Power Grid Based on Equipment Diagnoses

M. Kanamitsu, H. Kojima, N. Hayakawa, F. Endo, H. Okubo

International Symposium on EcoTopia Science 2007

超高速PD測定によるGIS内異物サイズの識別

西澤佳奈子，大楠崇司，小島寛樹，早川直樹，遠藤奎将，吉田昌展，内田克己，大久保仁

2007年放電学会年次大会

SF₆ガス中部分放電におけるリーダ進展と発光スペクトルの関係

吉田聡，小島寛樹，早川直樹，遠藤奎将，大久保仁

2007年放電学会年次大会

高温超電導限流変圧器（2G HTc-SFCLT）における故障除去後の超電導復帰過程

伊藤智志，小島寛樹，早川直樹，遠藤奎将，大久保仁

平成19年度電気関係学会東海支部連合大会

電力システムにおける機器故障率の送配電コストに及ぼす影響

金光正樹，小島寛樹，早川直樹，遠藤奎将，大久保仁

平成19年度電気関係学会東海支部連合大会

SF₆ガス中部分放電におけるストリーマ/リーダ転移と発光エネルギーとの相関特性

吉田聡，小島寛樹，早川直樹，遠藤奎将，大久保仁

平成19年度電気関係学会東海支部連合大会

実規模高温超電導ケーブルにおける部分放電開始電界の体積効果

山口竜太郎，小島寛樹，早川直樹，遠藤奎将，大久保仁

平成19年度電気関係学会東海支部連合大会

Self-recovery Characteristics of High-Tc Superconducting Fault Current Limiting Transformer (HTc-SFCLT) with 2G Coated Conductors International coauthorship International conference

H. Kojima, S. Itoh, N. Hayakawa, F. Endo, M. Noe, H. Okubo

8th European Conference on Applied Superconductivity

Quench-induced Partial Discharge Characteristics of HTS Cables International conference

N. Hayakawa, S. Ueyama, H. Kojima, F. Endo, Y. Ashibe, T. Masuda, M. Hirose

8th European Conference on Applied Superconductivity

機器統合型交直変換器用変圧器における電気絶縁設計に関する検討

小島寛樹，中野哲太郎，遠藤奎将，大久保仁

平成19年電気学会電力・エネルギー部門大会

実規模高温超電導ケーブルにおける部分放電開始特性

山口竜太郎，小島寛樹，早川直樹，遠藤奎将，大久保仁

平成19年電気学会電力・エネルギー部門大会

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