小島 寛樹 (コジマ ヒロキ)

Breakdown Charge Dependence of Counter Electrode Material Adhesion and Dielectric Strength after Spark Conditioning in Vacuum
N. Kita,H. Kojima,N. Hayakawa,H. Fukuda,K. Yamamura,K. Nagatake
IEEE Transactions on Dielectrics and Electrical Insulation 30(6) 2592-2598 2023年12月 Spark conditioning is an effective method of increasing the dielectric strength in vacuum. In this a... [査読有り]

コンデンサ形計器用変圧器の期待寿命評価方法および部分放電進展特性
永木雄也,林恭平,小島寛樹,吉田昌展,大谷彰,早川直樹
電気学会論文誌Ｂ（電力・エネルギー部門誌） 143(10) 559-566 2023年10月 Aged CVTs have been often used in substations, but the expected lifetime of CVTs is unclear, so that... [査読有り]

Electric Field Grading and Discharge Inception Voltage Improvement on HVDC GIS/GIL Spacer with Permittivity and Conductivity Graded Materials (ε/σ-FGM)
Rachmawati,H. Kojima,K. Kato,N. Zebouchi,N. Hayakawa
IEEE Transactions on Dielectrics and Electrical Insulation 29(5) 1811-1817 2022年10月 Functionally graded materials (FGM) application with graded permittivity and conductivity is promisi... [査読有り]

Melting and Generation of Micro-Protrusions on Cathode Surface during Spark Conditioning Process in Vacuum
N. Kita,F. Kondo,H. Kojima,N. Hayakawa,H. Fukuda,K. Yamamura
IEEE Transactions on Dielectrics and Electrical Insulation 29(3) 1160-1166 2022年06月 Spark conditioning is an effective method to increase the dielectric strength in vacuum by melting a... [査読有り]

Volume Effect of Dynamic Breakdown Strength in Liquid Nitrogen under Transient Bubble Disturbance for Resistive Superconducting Fault Current Limiters
N. Hayakawa,Y. Mori,H. Kojima
IEEE Transactions on Dielectrics and Electrical Insulation 29(1) 264-269 2022年02月 Liquid nitrogen (LN2) is indispensable as the cooling and electrical insulating materials for high-t... [査読有り]

Breakdown Characteristics of Cone-type ε-FGM Spacer for Gas Insulated Switchgears
Y. Miyazaki,H. Kojima,H. Masui,H. Mitsudome,H. Yanase,K. Okamoto,K. Watanabe,K. Kato,N. Hayakawa
電気学会論文誌Ａ（基礎・材料・共通部門誌） 141(10) 546-551 2021年10月 Gas insulated switchgears (GIS) are required to be downsized for the cost reduction, global warming ... [査読有り] [依頼有り]

Alternative Test Method of Internal Arcing for Replacing SF#D6#DR by Air in SF#D6#DR-Insulated Power Equipment
M. Kotari,M. Iwata,H. Kojima,N. Hayakawa
Engineering Research Express 3(3) 2021年09月 To develop an alternative test method of internal arcing for replacing sulfur hexafluoride (SF6) by ... [査読有り]

Dielectric Characteristics of Liquid Nitrogen/Synthetic Paper Composite Insulation System for Extra High Voltage HTS Cable
N. Hayakawa,Y. Yamakami,T. Masuda,H. Kojima
IEEE Transactions on Applied Superconductivity 31(5) 2021年08月 For extra-high-voltage high-temperature superconducting (HTS) cables, not only high electrical insul... [査読有り]

Time Transition of Activated Conductivity Distribution in Air and Charge Accumulation in Air-solid Composite Insulation Systems under DC Partial Discharge
R. Nakane,H. Kojima,N. Hayakawa
IEEE Transactions on Dielectrics and Electrical Insulation 28(3) 822-828 2021年06月 In this study, charge behavior in gas and on solid insulator due to DC partial discharge (DC-PD) is ... [査読有り]

Electric Field Simulation of Permittivity and Conductivity Graded Materials (ε/σ-FGM) for HVDC GIS Spacers
Rachmawati,H. Kojima,N. Hayakawa,K. Kato,N. Zebouchi
IEEE Transactions on Dielectrics and Electrical Insulation 28(2) 736-744 2021年04月 This paper discusses the application of the novel technology - functionally graded material (FGM), w... [査読有り]

Development of Insulation System to Prevent Local Carbonization inside Stator Core of a Product Inverter-fed Motor
Y. Yoshitake,H. Kojima,Y. Kasai,S. Maruyama,H. Kojima,N. Hayakawa
電気学会論文誌Ａ（基礎・材料・共通部門誌） 141(4) 260-268 2021年04月 A new phenomenon, called “local carbonization” inside a stator core was detected as a unique precurs... [査読有り]

Reshaping of Micro-morphology Feature in Electrode Surface under Conditioning by Lightning Impulse Voltage in Vacuum Gaps
H. Ma,G. Li,Z. Liu,Y. Geng,J. Wang,H. Kojima
IEEE Transactions on Dielectrics and Electrical Insulation 27(6) 2056-2063 2020年12月 The objective of this paper is to determine the reshaping of the micro-morphology feature in both th... [査読有り]

Partial Discharge Inception Voltage under Inverter Surge Voltage Considering Interactive Effects of Environmental Factors
T. Kaji,H. Asai,T. Nozu,H. Kojima,N. Hayakawa
電気学会論文誌Ａ（基礎・材料・共通部門誌） 140(7) 349-356 2020年07月 Effects of environmental factors on partial discharge inception voltage (PDIV) under inverter surge ... [査読有り]

Quench-induced Dynamic Breakdown Characteristics of HTS Pancake Coil Model for Resistive SFCL
N. Hayakawa,M. Mimbu,Y. Mori,H. Kojima,S. Isojima,M. Kuwata
Journal of Physics: Conference Series 1559(1) 2020年06月 Quench-induced dynamic breakdown (BD) characteristics of LN2 under transient bubble disturbance at t... [査読有り]

Fault Current Limitation Coordination of Multiple SFCLs in IEEE 14-Bus Test System
N. Hayakawa,Y. Mori,H. Kojima
Journal of Physics: Conference Series 1559(1) 2020年06月 We have proposed the concept of "fault current limitation coordination" of multiple superconducting ... [査読有り]

インバータ駆動機におけるカーボン遊離現象の基礎検討
吉武勇一郎,小島啓明,笠井友樹,丸山正一,小島寛樹,早川直樹
電気学会論文誌Ａ（基礎・材料・共通部門誌） 140(1) 40-47 2020年01月 "Carbonization" were detected as the precursor phenomena on the insulation burning of rotating machi... [査読有り]

Resin Injection Behavior in Process of Manufacturing Insulation Spacer with Permittivity Gradient Using Computational Fluid Dynamics
T. Imai,Y. Hoshina,H. Kojima,N. Hayakawa
IEEE Transactions on Dielectrics and Electrical Insulation 26(5) 1669-1677 2019年10月 The advent of new technology for designing insulation materials with desired properties stimulates o... [査読有り]

Comparison of Permittivity Gradient in Resin Injected and Simulated Cone-Shaped Spacers
T. Imai,M. Takeuchi,Y. Hoshina,H. Kojima,N. Hayakawa
IEEE Transactions on Dielectrics and Electrical Insulation 26(5) 1678-1685 2019年10月 Functionally graded materials are at the cutting edge of material technology. They will enable high ... [査読有り]

Dynamic Breakdown Characteristics of Pancake Coil Model for Resistive-Type Superconducting Fault Current Limiters
N. Hayakawa,M. Mimbu,H. Kojima,S. Isojima,M. Kuwata
IEEE Transactions on Applied Superconductivity 29(5) 1-6 2019年08月 Toward the reliable and rational insulation design of resistive-type superconducting fault current l... [査読有り]

インバータサージ電圧下における巻線の部分放電開始電圧に及ぼす温度および湿度の複合的影響
梶武文,浅井洋光,小島寛樹,早川直樹
電気学会論文誌Ａ（基礎・材料・共通部門誌） 139(1) 30-37 2019年01月 We investigated the combined effect of temperature and humidity on partial discharge inception volta... [査読有り]

Simulation on Discharge Inception Voltage Improvement of GIS Spacer with Permittivity Graded Materials (epsilon-FGM) Using Flexible Mixture Casting Method
N. Hayakawa,Y. Miyaji,H. Kojima,K. Kato
IEEE Transactions on Dielectrics and Electrical Insulation 25(4) 1318-1323 2018年08月 For electric field grading in GIS spacers, the application of functionally graded materials (FGM) wi... [査読有り]

Fault Current Limitation Coordination in Electric Power Grid with Superconducting Fault Current Limiters
Naoki Hayakawa,Yuya Maeno,Hiroki Kojima
IEEE Transactions on Applied Superconductivity 28(4) 2018年06月 This paper proposes the concept of 'fault current limitation coordination' in a future electric powe... [査読有り]

Volume Effect of Dynamic Breakdown Strength in LN2 for Insulation Design of Resistive Superconducting Fault Current Limiters
Naoki Hayakawa,Kazuki Ishida,Masataka Mimbu,Hiroki Kojima,Shigeki Isojima,Minoru Kuwata
IEEE Transactions on Applied Superconductivity 28(4) 2018年06月 Toward the practical and rational insulation design of a resistive superconducting fault current lim... [査読有り]

誘電率傾斜機能材料（ε-FGM）を用いたGISスペーサモデルの作製とSF₆ガス中絶縁破壊電圧の理論的推定
宮路仁崇,小島寛樹,加藤克巳,早川直樹
電気学会論文誌A（基礎・材料・共通部門誌） 138(4) 155-162 2018年 For the relaxation and optimization of electric field distribution around Gas insulated switchgear (... [査読有り]

Improvement Mechanism of AC Breakdown Voltage of Insulating Oil with Dispersed Nanoparticles
Hiroki Kojima,Takafumi Kondo,Masahiro Hanai,Naoki Hayakawa
Electronics and Communications in Japan 100(12) 69-75 2017年12月 We investigated the fundamental insulation characteristics of insulating oil with dispersed nanopart...

Discharge Pattern Discrimination in Vacuum Interrupter with Non-contact Measurement of Shield Potential
Fei Kong,Hiroki Kojima,Naoki Hayakawa,Toshinori Kimura,Mitsuru Tsukima
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 24(5) 3265-3269 2017年10月 Vacuum interrupter has a composite insulation system. When an internal insulation fails, the dischar... [査読有り]

Discharge Pattern Discrimination for Composite Insulation System in Vacuum
Fei Kong,Hiroki Kojima,Toshinori Kimura,Mitsuru Tsukima,Naoki Hayakawa
Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) 200(3) 3-12 2017年08月 In order to develop higher-voltage vacuum circuit breakers (VCBs), the investigation of discharge ph... [依頼有り]

Optimum Breakdown Charge for Maximum Dielectric Strength in Spark Conditioning in Vacuum under a Non-uniform Electric Field
H. Kojima,T. Takahashi,N. Hayakawa,K. Hasegawa,M. Sakaki
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 24(4) 2660-2665 2017年08月 Spark conditioning is an effective method of increasing the dielectric strength in vacuum. In this p... [査読有り]

Electrical Insulation Characteristics and Mechanisms of Low Dielectric Loss Materials for High-Voltage HTS Cables
Naoki Hayakawa,Kazuki Ishida,Tatsuya Matsuoka,Hiroki Kojima
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27(4) 2017年06月 Toward the practical development of high-voltage high-temperature superconducting (HTS) cables, high... [査読有り]

Breakdown Characteristics and Mechanisms of Liquid Nitrogen Under Transient Thermal Stress for Superconducting Fault Current Limiters
Naoki Hayakawa,Tatsuya Matsuoka,Hiroki Kojima,Shigeki Isojima,Minoru Kuwata
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27(4) 2017年06月 We have been investigating the electrical breakdown (BD) characteristics of liquid nitrogen (LN2) wi... [査読有り]

Calculation Model for Predicting Partial-discharge Inception Voltage in a Non-uniform Air Gap while Considering the Effect of Humidity
Toshiaki Rokunohe,Tatsuro Kato,Hiroki Kojima,Naoki Hayakawa,Hitoshi Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 24(2) 1123-1130 2017年04月 A calculation model for predicting the inception of partial discharge (PD) in a non-uniform air gap ... [査読有り]

Reduction Method of Fluctuation in Partial Discharge Inception Voltage for Inverter-Fed Rectangular Wire Motors
T. Wakimoto,H. Kojima,N. Hayakawa
Electrical Engineering in Japan 198(2) 3-10 2017年01月 [依頼有り]

ナノ粒子添加による絶縁油の交流絶縁破壊電圧向上メカニズム
小島寛樹,近藤貴文,花井正広,早川直樹
電気学会論文誌A（基礎・材料・共通部門誌） 137(2) 101-106 2017年 We investigated the fundamental insulation characteristics of insulating oil with dispersed nanopart... [査読有り]

Measurement and Evaluation of Partial Discharge Inception Voltage for Enameled Rectangular Wires under AC Voltage
Toru Wakimoto,Hiroki Kojima,Naoki Hayakawa
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 23(6) 3566-3574 2016年12月 Recently, the market for EVs (Electric vehicles) and HEVs (Hybrid electric vehicles) has been expand... [査読有り]

Dependence of Spark Conditioning on Breakdown Charge and Electrode Material under a Non-Uniform Electric Field in Vacuum
H. Kojima,T. Takahashi,N. Hayakawa,K. Hasegawa,H. Saito,M. Sakaki
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 23(5) 3224-3230 2016年10月 Spark conditioning is an effective method for improving dielectric strength in vacuum. In this paper... [査読有り]

Pressure Dependence and Size Effect of LN2 Breakdown Characteristics Under Transient Thermal Stress
N. Hayakawa,T. Matsuoka,K. Ishida,H. Kojima,S. Isojima,M. Kuwata
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 26(3) 2016年04月 Electrical insulation of liquid nitrogen (LN2) for a high-temperature superconducting (HTS) power ap... [査読有り]

Discharge Characteristics of Composite Insulation System with Floating Electrode and Solid Insulator in Vacuum
Fei Kong,Yusuke Nakano,Hiroki Kojima,Naoki Hayakawa,Toshinori Kimura,Mitsuru Tsukima
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 23(2) 1219-1225 2016年04月 For the development of vacuum interrupters for their higher voltage application in power transmissio... [査読有り]

Discharge Characteristics for Various Discharge Patterns under Negative Lightning Impulse Voltage in Vacuum
Fei Kong,Yusuke Nakano,Hiroki Kojima,Naoki Hayakawa,Toshinori Kimura,Mitsuru Tsukima
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 23(2) 813-818 2016年04月 In order to develop higher voltage vacuum interrupters (VIs), electrical insulation performances in ... [査読有り]

Control and Suppression of Impulse Surface Flashover in Vacuum Based on Discharge Development Mechanisms
Yusuke Nakano,Hiroki Kojima,Shinsuke Iitsuka,Kenji Tsuchiya,Naoki Hayakawa
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 23(1) 35-42 2016年02月 Surface discharge on solid insulator in vacuum is one of the significant issues for the development ... [査読有り]

Analysis of Conditioning and Damaging Process in Vacuum based on Breakdown Probability Distribution
H. Kojima,Y. Otake,T. Takahashi,N. Hayakawa,K. Hasegawa,H. Saito,M. Sakaki
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 23(1) 43-48 2016年02月 For the enhancement of insulation strength in vacuum, spark conditioning is an important and effecti... [査読有り]

Classification of Impulse Breakdown Mechanisms under Non-uniform Electric Field in Air
Hiroki Kojima,Katsuki Hotta,Takuya Kitamura,Naoki Hayakawa,Atsushi Otake,Kinya Kobayashi,Tatsuro Kato,Toshiaki Rokunohe,Hitoshi Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 23(1) 194-201 2016年02月 To clarify the breakdown mechanism and the conditions leading to the breakdown under non-uniform ele... [査読有り]

Fabrication and Simulation of Permittivity Graded Materials for Electric Field Grading of Gas Insulated Power Apparatus
Naoki Hayakawa,Junya Ishiguro,Hiroki Kojima,Katsumi Kato,Hitoshi Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 23(1) 547-554 2016年02月 An innovation for the higher performance and reliability of electric power apparatus can be brought ... [査読有り]

平角線モータにおける部分放電開始電圧のばらつき低減方法
脇本亨,小島寛樹,早川直樹
電気学会論文誌A（基礎・材料・共通部門誌） 136(3) 121-127 2016年 We investigated the decisive factors which affect partial discharge inception voltage (PDIV) fluctua... [査読有り]

真空中沿面フラッシオーバ進展過程における絶縁物上過渡帯電存在時の実効的2次電子放出係数
中野裕介,小島寛樹,土屋賢治,早川直樹
電気学会論文誌A（基礎・材料・共通部門誌） 136(3) 128-134 2016年 Based on the mechanism of surface flashover development in vacuum, we have investigated that the sur... [査読有り]

真空中の複合絶縁系における放電パターンの識別
孔飛,小島寛樹,木村俊則,月間満,早川直樹
電気学会論文誌A（基礎・材料・共通部門誌） 136(9) 594-602 2016年 In order to develop higher-voltage vacuum circuit breakers (VCB), the investigation of discharge phe... [査読有り]

Transient Charging Characteristics in Surface Flashover Development Process due to Explosive Electron Emission in Vacuum
Yusuke Nakano,Hiroki Kojima,Kenji Tsuchiya,Naoki Hayakawa
Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) 193(2) 10-17 2015年11月 For the development of higher voltage vacuum circuit breakers and vacuum interrupters, surface disch... [依頼有り]

Size Effect on Breakdown Strength in Sub-cooled Liquid Nitrogen for Superconducting Power Apparatus
Naoki Hayakawa,Seiichiro Nishimachi,Hiroki Kojima,Hitoshi Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 22(5) 2565-2571 2015年10月 Toward the practical and rational insulation design of high temperature superconducting power appara... [査読有り]

Impulse Surface Flashover Development Associated with Transient Charging by Explosive Electron Emission in Vacuum
Yusuke Nakano,Hiroki Kojima,Kenji Tsuchiya,Naoki Hayakawa
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 22(4) 2390-2397 2015年08月 Surface discharge on solid insulator in vacuum, which is one of the most significant issues under hi... [査読有り]

Quench-Induced Dynamic Breakdown Characteristics of LN2 and LN2/PPLP Composite Electrical Insulation System for Superconducting Power Apparatus
N. Hayakawa,T. Matsuoka,S. Nishimachi,H. Kojima
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 25(3) 2015年06月 In HTS power apparatus, quench due to the fault current generates dynamic electrical/thermal combine... [査読有り]

Fault Current Limitation Coordination in Power Transmission System With Superconducting Fault Current Limiting Cables (SFCLC)
Hiroki Kojima,Takeshi Osawa,Naoki Hayakawa
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 25(3) 2015年06月 We investigate a Superconducting Fault Current Limiting Cable (SFCLC), which is an HTS cable with fa... [査読有り]

Power flow control and maintenance strategy of transformers in transmission and distribution systems
Hiroki Kojima,Koki Fukaya,Naoki Hayakawa,Masahiro Hanai,Hitoshi Okubo
IEEJ Transactions on Power and Energy 135(5) 316-321 2015年05月 Transmission and distribution (T& D) systems for electric power are assembled with a large amount... [査読有り]

真空中における突発的電子放出に起因する沿面フラッシオーバ進展過程の過渡帯電特性
中野裕介,小島寛樹,土屋賢治,早川直樹
電気学会論文誌A（基礎・材料・共通部門誌） 134(11) 578-584 2014年11月 For the development of higher voltage vacuum circuit breakers (VCB) and vacuum interrupters (VI), su... [査読有り]

Development of a partial discharge inception calculation model of a nonuniform air gap considering the effect of humidity
Norihito Yanagita,Tatsuro Kato,Toshiaki Rokunohe,Takeshi Iwata,Hiroki Kojima,Naoki Hayakawa,Hitoshi Okubo
Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) 186(3) 1017-1023 2014年02月 Insulation design employing discharge simulation based on physics phenomena is used in designing ele... [依頼有り]

Pre-discharge and Flashover Characteristics of Impulse Surface Discharge in Vacuum
Yusuke Nakano,Hiroki Kojima,Naoki Hayakawa,Kenji Tsuchiya,Hitoshi Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 21(1) 403-410 2014年02月 Surface discharge on solid insulators is one of the significant issues in the development of vacuum ... [査読有り]

Technique for Discriminating the Type of PD in SF6 Gas Using the UHF Method and the PD Current with a Metallic Particle
Masahiro Hanai,Hiroki Kojima,Naoki Hayakawa,Ryunosuke Mizuno,Hitoshi Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 21(1) 88-95 2014年02月 The relationship between the PD current pulse waveform at the PD source and the radiated electromagn... [査読有り]

Influence of longitudinal temperature distribution on current limiting function of Superconducting Fault Current Limiting Cable (SFCLC)
H. Kojima,T. Osawa,N. Hayakawa,M. Hanai,H. Okubo
Journal of Physics: Conference Series 507(3) 2014年 We have proposed a Superconducting Fault Current Limiting Cable (SFCLC), which is an HTS cable with ... [査読有り]

Integration of Asset Management and Smart Grid with Intelligent Grid Management System
M. Hanai,H. Kojima,N. Hayakawa,K. Shinoda,H. Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 20(6) 2195-2202 2013年12月 Electric power transmission and distribution (T and D) systems are composed of a great deal of aged ... [査読有り]

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
電気学会論文誌B（電力・エネルギー部門誌） 133(1) 114-120 2013年 A metallic particle defect seriously degrades an insulation performance of gas insulated switchgear ... [査読有り]

Physical mechanisms of partial discharges at nitrogen filled delamination in epoxy cast resin power apparatus
Diaa-Eldin A. Mansour,Hiroki Kojima,Naoki Hayakawa,Masahiro Hanai,Hitoshi Okubo
IEEE Transactions on Dielectrics and Electrical Insulation 20(2) 454-461 2013年 For proper insulation design of epoxy cast resin power apparatus such as molded transformers, it is ... [査読有り]

Feasibility study of superconducting power flow controller and fault current limiter (SPFCL)
N. Hayakawa,X. Mao,H. Kojima,M. Hanai,H. Okubo,N. Kashima,S. Nagaya,S. Sugimoto
IEEE Transactions on Applied Superconductivity 23(3) 2013年 A superconducting power flow controller and fault current limiter is proposed in this paper, which c... [査読有り]

Feasibility Study on a High-Temperature Superconducting Fault-Current-Limiting Cable (SFCLC) Using Flux-Flow Resistance
Hiroki Kojima,Fumihiko Kato,Naoki Hayakawa,Masahiro Hanai,Hitoshi Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 22(2) 2012年04月 We propose a high-temperature superconducting fault-current-limiting cable (SFCLC), which is a high-... [査読有り]

Conditioning Mechanism of Cu-Cr Electrode Based on Electrode Surface State under Impulse Voltage Application in Vacuum
Hiroki Kojima,Naoki Hayakawa,Ryouki Nishimura,Hitoshi Okubo,Hiromasa Sato,Hitoshi Saito,Yasushi Noda
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 18(6) 2108-2114 2011年12月 Because of high insulation performance and environmental-friendliness, vacuum is attracting consider... [査読有り]

Development Process of Impulse Surface Flashover on Alumina Dielectrics in Vacuum
Hiroki Kojima,Naoki Hayakawa,Tsugunari Ishida,Hitoshi Okubo,Kenji Tsuchiya
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 18(3) 918-923 2011年06月 For higher electrical insulation performance of vacuum circuit breakers (VCB), the surface insulatio... [査読有り]

Analysis of Current Limiting and Recovery Characteristics of Superconducting Fault Current Limiting Transformer (SFCLT) With YBCO Coated Conductors
N. Hayakawa,T. Kito,H. Kojima,M. Hanai,H. Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21(3) 1422-1425 2011年06月 Superconducting Fault Current Limiting Transformer (SFCLT) is expected to function as superconductin... [査読有り]

Current Limiting and Recovery Characteristics of 2 MVA Class Superconducting Fault Current Limiting Transformer (SFCLT)
Hiroki Kojima,Masashi Kotari,Toyoaki Kito,Naoki Hayakawa,Masahiro Hanai,Hitoshi Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21(3) 1401-1404 2011年06月 We have been developing Superconducting Fault Current Limiting Transformer (SFCLT) with the function... [査読有り]

Progress in Development of Superconducting Fault Current Limiting Transformer (SFCLT)
Naoki Hayakawa,Hiroki Kojima,Masahiro Hanai,Hitoshi Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21(3) 1397-1400 2011年06月 We have been developing Superconducting Fault Current Limiting Transformer (SFCLT), which has multif... [査読有り]

Evaluation of UHF Method for Partial Discharge Measurement by Simultaneous Observation of UHF Signal and Current Pulse Waveforms
M. Yoshida,H. Kojima,N. Hayakawa,F. Endo,H. Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 18(2) 425-431 2011年04月 The partial discharge - current pulse waveform analyzing (PD-CPWA) system can measure partial discha... [査読有り]

部分放電の時系列測定によるGIS内部の欠陥状態識別
吉田昌展,鈴木啓介,小島寛樹,早川直樹,花井正広,大久保仁
電気学会論文誌B（電力・エネルギー部門誌） 131(11) 4-911 2011年 To maintain the insulation reliability on gas insulated switchgear (GIS), several partial discharge ... [査読有り]

湿度の影響を考慮した気中不平等ギャップにおける部分放電開始計算モデルの開発
柳田憲史,加藤達朗,六戸敏昭,岩田健,小島寛樹,早川直樹,大久保仁
電気学会論文誌A（基礎・材料・共通部門誌） 131(12) 1017-1023 2011年 Insulation design with discharge simulation based on physics phenomena is used in designing electric... [査読有り]

Partial Discharges and Associated Mechanisms for Micro Gap Delamination at Epoxy Spacer in GIS
Diaa-Eldin A. Mansour,Hiroki Kojima,Naoki Hayakawa,Fumihiro Endo,Hitoshi Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 17(3) 855-861 2010年06月 For accurate detection and diagnosis of Partial Discharges (PDs) in Gas Insulated Switchgears (GISs)... [査読有り]

Charge Accumulation Effects on Time Transition of Partial Discharge Activity at GIS Spacer Defects
Diaa-Eldin A. Mansour,Kanako Nishizawa,Hiroki Kojima,Naoki Hayakawa,Fumihiro Endo,Hitoshi Okubo
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 17(1) 247-255 2010年02月 The partial discharge (PD) measurements are considered as the most important tool for condition moni... [査読有り]

Partial discharge activities under AC/impulse superimposed voltage in LN2/polypropylene laminated paper insulation system for HTS cables
N. Hayakawa,R. Yamaguchi,Y. Ukai,H. Kojima,F. Endo,H. Okubo
Journal of Physics: Conference Series 234(3) 2010年 This paper discusses electrical insulation characteristics of high temperature superconducting (HTS)... [査読有り]

真空中インパルス電圧印加時における電極間微小電流発生メカニズムの検討
青木圭太,安川英明,小島寛樹,本間三孝,塩入哲,大久保仁
電気学会論文誌A（基礎・材料・共通部門誌） 130(9) 1-786 2010年 Small discharge not to accompany breakdown can occur under high electric field in vacuum, however th... [査読有り]

Surface charge accumulation and partial discharge activity for small gaps of electrode/epoxy interface in sf6 gas
Diaa-Eldin A. Mansour,Hiroki Kojima,Naoki Hayakawa,Fumihiro Endo,Hitoshi Okubo
IEEE Transactions on Dielectrics and Electrical Insulation 16(4) 1150-1157 2009年08月 The electrical insulation reliability of solid spacers in Gas Insulated Switchgears (GISs) is an imp... [査読有り]

Dynamic Thermal Characteristics of HTS Coil for Conduction-Cooled SMES
Hiroki Kojima,Xin Chen,Naoki Hayakawa,Fumihiro Endo,Hitoshi Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 19(3) 2036-2039 2009年06月 In this paper, we investigate the thermal runaway characteristics of a BSCCO HTS single pancake coil... [査読有り]

Current Limiting Characteristics of Parallel-Connected Coated Conductors for High-Tc Superconducting Fault Current Limiting Transformer (HTc-SFCLT)
Koki Omura,Hiroki Kojima,Naoki Hayakawa,Fumihiro Endo,Mathias Noe,Hitoshi Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 19(3) 1880-1883 2009年06月 We have been developing Superconducting Fault Current Limiting Transformer (SFCLT) as a superconduct... [査読有り]

Partial discharge activity in electrical insulation for high temperature superconducting (HTS) cables
H. Okubo,H. Kojima,F. Endo,K. Sahara,R. Yamaguchi,N. Hayakawa
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 15(3) 647-654 2008年06月 This paper discusses electrical insulation characteristics of liquid nitrogen (LN2) / polypropylene ... [査読有り]

Self-recovery characteristics of high-Tc superconducting fault current limiting transformer (HTc-SFCLT) with 2G coated conductors
H. Kojima,S. Ito,N. Hayakawa,F. Endo,M. Noe,H. Okubo
Journal of Physics: Conference Series 97(1) 2008年02月 We have been developing Superconducting Fault Current Limiting Transformer (SFCLT) with both functio... [査読有り]

Quench-induced partial discharge characteristics of HTS cables
N. Hayakawa,S. Ueyama,H. Kojima,F. Endo,Y. Ashibe,T. Masuda,M. Hirose
Journal of Physics: Conference Series 97(1) 2008年02月 This paper discusses the partial discharge (PD) characteristics of HTS cables under quench condition... [査読有り]

Breakdown characteristics of N2O gas mixtures for quasi-uniform electric field under lightning impulse voltage
Hiroki Kojima,Osamu Kinoshita,Naoki Hayakawa,Fumihiro Endo,Hitoshi Okubo,Masanobu Yoshida,Tatsuya Ogawa
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION 14(6) 1492-1497 2007年12月 From the viewpoint of mitigating global warming by SF6 gas, this paper discusses breakdown (BD) char... [査読有り]

Thermal runaway characteristics of Bi2212 coil for conduction-cooled SMES
Hiroki Kojima,Naoki Hayakawa,Shinki Noguchi,Fumihiro Endo,Naoki Hirano,Shigeo Nagaya,Hitoshi Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17(2) 1959-1962 2007年06月 In this paper, we investigated the thermal runaway characteristics of a conduction-cooled Bi2212 HTS... [査読有り]

High-Tc superconducting fault current limiting transformer (HTc-SFCLT) with 2G coated conductors
H. Okubo,C. Kurupakorn,S. Ito,H. Kojima,N. Hayakawa,F. Endo,M. Noe
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17(2) 1768-1771 2007年06月 We developed a 3-phase, 100 kVA, 6600 V/210 V high temperature Superconducting Fault Current Limitin... [査読有り]

Electrical insulation characteristics of HTS cables under quench-induced thermal stress condition
N. Hayakawa,S. Ueyama,H. Kojima,F. Endo,T. Masuda,M. Hirose
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17(2) 1660-1663 2007年06月 This paper discusses the electrical insulation characteristics of high temperature superconducting (... [査読有り]

Electrical and thermal characteristics of Bi2212/Ag HTS coils for conduction-cooled SMES
N. Hayakawa,S. Noguchi,C. Kurupakorn,H. Kojima,F. Endo,N. Hirano,S. Nagaya,H. Okubo
Journal of Physics: Conference Series 43(1) 813-816 2006年06月 In this paper, we investigated the electrical and thermal performance of conduction-cooled Bi2212/Ag... [査読有り]

Simulation of electrical and thermal behavior of high temperature superconducting fault current limiting transformer (HTc-SFCLT)
C. Kurupakorn,H. Kojima,N. Hayakawa,F. Endo,N. Kashima,S. Nagaya,M. Noe,H. Okubo
Journal of Physics: Conference Series 43(1) 950-953 2006年06月 Superconducting Fault Current Limiting Transformer (SFCLT) is expected to perform functions both of ... [査読有り]

N₂O混合ガスの絶縁特性におけるシナジズム効果
早川直樹,木下修,小島寛樹,遠藤奎将,吉田昌展,小川達也,大久保仁
電気学会論文誌B（電力・エネルギー部門誌） 126(11) 1164-1170 2006年 SF6ガスは，その高い絶縁性能から，ガス絶縁開閉装置（GIS）やガス絶縁送電線（GIL）をはじめとする高電圧電力機器の絶縁媒体として広く利用されている．しかし，地球温暖化などの地球環境問題が表面化し，... [査読有り]

Dielectric characteristics of HTS cables based on partial discharge measurement
N Hayakawa,M Nagino,H Kojima,M Goto,T Takahashi,K Yasuda,H Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 15(2) 1802-1805 2005年06月 We have discussed dielectric characteristics of liquid nitrogen (LN2)/polypropylene (PP) laminated p... [査読有り]

Recovery characteristics after current limitation of high temperature superconducting fault current limiting transformer (HTc-SFCLT)
C Kurupakorn,H Kojima,N Hayakawa,M Goto,N Kashima,S Nagaya,M Noe,KP Juengst,H Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 15(2) 1859-1862 2005年06月 Superconducting Fault Current Limiting Transformer (SFCLT) is one of the promising superconducting p... [査読有り]

Temperature dependence of critical current at 4.2 K-55K of conduction-cooled Bi2212/Ag wires for SMES
H Kojima,S Noguchi,C Kurupakorn,N Hayakawa,M Goto,N Hirano,S Nagaya,H Okubo
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 15(2) 2550-2553 2005年06月 In this paper, fundamental characteristics of conduction-cooled Bi2212/Ag wires and coils for HTS SM... [査読有り]

Formation of Deep Potential Well and its Structural Transition in Small Tokamak Device
Y. Fukuzawa,H. Kojima,T. Okada,N. Ohno,S. Takamura
Europhysics Conference Abstracts 28G 2004年07月

Formation and Dynamics of Very Deep Negative Potential Well in the Small Tokamak Device CSTN-IV
H. Kojima,Y. Fukuzawa,T. Manabe,S. Takamura,T. Okada,N. Ohno
Czechoslovak Journal of Physics 53(10) 895-902 2003年10月 We achieved a potential well more than fifty times deeper than the plasma electron temperature, down... [査読有り]

Structural Dynamics of Deep Negative Potential Well Formation in Small Tokamak Device CSTN-IV
H. Kojima,Y. Fukuzawa,T. Manabe,N. Ohno,S. Takamura
Europhysics Conference Abstracts 27A 2003年09月

Spatiotemporal Behavior of Hydrogen Recycling due to the Rotating Magnetic Field
H. Kojima,S. Takamura
Japanese Journal of Applied Physics 42(9A) 5797-5798-5798 2003年09月 A rotating helical magnetic field (RHF) moderates the toroidal nonuniformity of plasma particle flux... [査読有り]

Effects of Rotating Helical Magnetic Field on Inhomogeneities of Hydrogen Recycling in a Tokamak Discharge.
H. Kojima,S. Takamura
Japanese Journal of Applied Physics 41(11A) 6557-6562 2002年11月 A rotating helical magnetic field (RHF) makes an effective recycling wall area increase so that the ... [査読有り]

Characteristics of Local Helical Coil System for Dynamic Ergodic Divertor
Y. Kikuchi,H. Kojima,T. Taniyama,M. Toyoda,Y. Uesugi,S. Takamura
Electrical Engineering in Japan 139(1) 16-23 2002年04月 Heat and particle flux control is one of the most important and difficult problems in steady-state f... [依頼有り]

Effects of Dynamic Island Formations on Rotating Helical Magnetic Field Penetration into the Tokamak Plasma
Y. Kikuchi,H. Kojima,T. Taniyama,M. Toyoda,Y. Uesugi,S. Takamura
Europhysics Conference Abstracts 25A 2001年12月

Toroidal Dependence of Hydrogen Recycling Property with Helical Magnetic Perturbation in Long Time Discharge
H. Kojima,S. Takamura
Europhysics Conference Abstracts 25A 2001年12月

動的エルゴディックダイバータ実験に用いる局所ヘリカルコイル系の特性評価
菊池祐介,小島寛樹,谷山智則,豊田光洋,上杉喜彦,高村秀一
電気学会論文誌A（基礎・材料・共通部門誌） 121(3) 249-255 2001年03月 Heat and particle flux control is one of the most important and difficult problems in steady state f... [査読有り]

Penetration Process of the Externally Applied Rotating Helical Field into the Tokamak Plasma
M. Kobayashi,H. Kojima,S. Takamura
Europhysics Conference Abstracts 24B 2001年01月

Research Tokamak System with Multimode Discharges Using Inverter Power Supply
H. Kojima,M. Kobayashi,K. Tashiro,M. Takagi,S. Takamura
Electrical Engineering in Japan 133(4) 2000年12月 [依頼有り]