研究者詳細 - 小島　寛樹

講演・口頭発表等 - 小島　寛樹

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Multiple Breakdown Induced by Previous Breakdown in Higher Frequency AC Conditioning 国際会議

R. Konagi, H. Kojima, S. Iitsuka, M. Kobayashi, N. Hayakawa

30th International Symposium on Discharge and Electrical Insulation in Vacuum 2023年6月29日 Technical Committee of Electrical Dicharges, Plasma and Pulsed Power, IEEJ

開催年月日： 2023年6月

記述言語：英語会議種別：ポスター発表

開催地：Okinawa 国名：日本国

We have confirmed that the multiple breakdowns (BDs) occur in a half cycle of AC voltage application in the AC conditioning process in vacuum. In previous research, it has been experimentally confirmed that the higher frequency AC conditioning suppresses the multiple BDs and improves the conditioning effect. In this paper, we discuss how the multiple BDs are induced. By the BD light emission images during AC conditioning, we found that the multiple BDs occurred in close to the previous BD position. This suggests that the multiple BDs were induced by the previous BD. Two possible causes of the multiple BDs are investigated: (a) metal vapor generated by the previous BD and (b) metal particles generated by the previous BD. The diffusion time of metal vapor is much shorter than the time interval for the multiple BDs. Therefore, the multiple BDs may not be induced by metal vapor. On the other hand, for particles of 10 μm order in diameter, the time of collision to the counter electrode matches the time interval of the multiple BDs. Particles of the order of 10 μm in diameter were found on the electrode surface after AC conditioning. These results suggest that the multiple BDs were initiated by metal particles generated by the previous BD and do not contribute to protrusion melting, but damage the electrode surface. Therefore, the higher frequency AC conditioning to suppress the multiple or harmful BDs can be promising for AC conditioning process in vacuum.

DOI： 10.23919/ISDEIV55268.2023.10201218

Scopus

CiNii Research

Applicability of Lubricating Oil Insulation in Higher Power Density Motors for Electric Powered Aircraft 国際会議

N. Hayakawa, H. Kamada, H. Kojima, N. Aruga, K. Utatsu, S. Watanabe

22nd IEEE International Conference on Dielectric Liquids 2023年6月27日 IEEE DEIS

開催年月日： 2023年6月

記述言語：英語会議種別：口頭発表（一般）

開催地：Worcester 国名：アメリカ合衆国

Higher power density motors for electric powered aircraft require higher voltage. The authors aim to apply a lubricating oil used for cooling motor windings to an insulating material to improve the dielectric strength of motors. In motor insulation, it is required to prevent the occurrence of partial discharge (PD) and understand the insulating characteristics of the lubricating oil. In this paper, we first measured and compared the breakdown voltage (BDV) of the lubricating oil and mineral oil in a fundamental sphere-sphere electrode system, and discussed the basic breakdown characteristics. The results suggest that the lubricating oil has superior dielectric characteristics to the mineral oil. Next, PD inception voltage (PDIV) of an arrow pair of enamel-coated rectangular wires in the lubricating oil was measured and compared with the estimated PDIV by electric field analysis. As a result, the measured PDIV was generally consistent with the estimated PDIV. Therefore, the lubricating oil insulation is expected to improve the dielectric strength in the motor windings for electric powered aircraft.

DOI： 10.1109/ICDL59152.2023.10209296

Scopus

CiNii Research

多端子直流送電システムの線路故障時における超電導限流器の限流効果および過渡安定度向上効果

村上雅紀，西澤大将，小島寛樹，早川直樹

令和5年電気学会全国大会 2023年3月17日電気学会

電子追跡シミュレーションによる真空中沿面放電の初期進展メカニズム

杉浦拓真，小島寛樹，早川直樹

令和5年電気学会全国大会 2023年3月16日電気学会

電動推進航空機用モータにおける流動潤滑油の部分放電開始特性

鎌田泰任，中澤尚輝，小島寛樹，有賀信雄，卯辰清志，渡邉瞬也，早川直樹

令和5年電気学会全国大会 2023年3月15日電気学会

コンデンサ形計器用変圧器におけるアルミ箔/油浸紙複合絶縁系の部分放電特性

林恭平，永木雄也，小島寛樹，吉田昌展，早川直樹

令和5年電気学会全国大会 2023年3月15日電気学会

真空中コンディショニングの放電電荷量依存性における電極初期表面状態の影響

北直樹，小島寛樹，福田英昭，山村健太，早川直樹

令和5年電気学会全国大会 2023年3月15日電気学会

真空中交流コンディショニングにおける粒子起因による多重絶縁破壊

小名木良太，小島寛樹，飯塚伸介，小林将人，早川直樹

令和5年電気学会全国大会 2023年3月15日電気学会

乾燥空気中におけるコーン型ε-FGMスペーサの絶縁破壊特性

加藤拓夢，杉本遼次，小島寛樹，柳瀬博雅，岡本健次，早川直樹

令和5年電気学会全国大会 2023年3月17日電気学会

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，早川直樹

電気学会静止器研究会 2022年12月15日電気学会静止器技術委員会

Application of TEV Sensors to PD Measurement for Capacitor Voltage Transformers 国際会議

Y. Nagaki, H. Kojima, M. Yoshida, N. Hayakawa

9th International Conference on Condition Monitoring and Diagnosis 2022年11月16日 IEEJ Technical Committee on Dielectrics and Electrical Insulation

開催年月日： 2022年11月

記述言語：英語会議種別：口頭発表（一般）

開催地：Kitakyushu 国名：日本国

This study aims to establish an insulation diagnosis method based on partial discharge (PD) measurement for capacitor voltage transformers (CVTs). Since aged CVTs over 50 years have been used in substations, an insulation diagnosis technique for CVTs is urgently required. Recently, transient earth voltage (TEV) sensors are used as PD detection sensors in transformers. Since the TEV sensors detect leakage electromagnetic waves and ground line currents, the PD signals in CVTs can also be detected by TEV sensors. However, the applicability of a TEV sensor to PD measurement in CVTs has not been verified. In this paper, the applicability of a TEV sensor for PD detection in the actual CVT (24-year-old) is discussed. As the experimental results, it was found that the TEV output has a good correlation with the PD charge over a wide range from 60 pC to 60,000 pC with the correlation coefficient as high as 0.99. Therefore, the TEV sensor is effective as a PD sensor for CVTs.

DOI： 10.23919/CMD54214.2022.9991361

Scopus

その他リンク： https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=iroffice_5964&SrcAuth=WosAPI&KeyUT=WOS:000937794300036&DestLinkType=FullRecord&DestApp=WOS_CPL

Partial Discharge Characteristics of Aluminum Foil/Oil-impregnated Paper Insulation System for Insulation Diagnosis of Capacitor Voltage Transformer 国際会議

K. Hayashi, S. Wakita, Y. Nagaki, H. Kojima, M. Yoshida, N. Hayakawa

9th International Conference on Condition Monitoring and Diagnosis 2022年11月17日 IEEJ Technical Committee on Dielectrics and Electrical Insulation

開催年月日： 2022年11月

記述言語：英語会議種別：ポスター発表

開催地：Kitakyushu 国名：日本国

Capacitor voltage transformers (CVTs) composed of aluminum foil/oil-impregnated paper insulation system have been operated over 30 years in substations. For the condition monitoring and diagnosis of aged CVTs, partial discharge (PD) detection is expected. However, PD characteristics from PD inception and progress to breakdown (BD) have not yet been clarified. Thus, PD characteristics of a fundamental insulation model composed of aluminum foil/oil-impregnated paper insulation systems are discussed in this paper. Experimental results under a fixed applied voltage revealed that PD characteristics can be classified into 3 periods. In Period 1, PD signals were intermittently generated mainly around the peak phase of applied voltage. In Period 2, PD signals were continuously generated around zero crossing (void discharge) to peak phase. In Period 3, PD signals larger than 10,000 pC were generated. Together with the above electrical PD measurement, the optical measurement of PD light emission images, bubble behavior, and their time transmission were also carried out in order to discuss the mechanism of PD progress.

DOI： 10.23919/CMD54214.2022.9991513

Scopus

その他リンク： https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=iroffice_5964&SrcAuth=WosAPI&KeyUT=WOS:000937794300118&DestLinkType=FullRecord&DestApp=WOS_CPL

Discharge Developing Time of Surface Flashover on Solid Dielectrics around Impulse Test Voltage of Vacuum Interrupters 国際会議

R. Watarai, H. Kojima, T. Donen, S. Yamaguchi, N. Hayakawa

9th International Conference on Condition Monitoring and Diagnosis 2022年11月15日 IEEJ Technical Committee on Dielectrics and Electrical Insulation

開催年月日： 2022年11月

記述言語：英語会議種別：ポスター発表

開催地：Kitakyushu 国名：日本国

We have found that the developing time Td of surface flashover on solid dielectrics (alumina) in vacuum is dominated by the propagation time of the conductive channel, which is proportional to the discharge path length and inversely proportional to the square of the discharge inception voltage Vd. Based on the experimental database on Td-Vd characteristics below 30 kV, we have proposed a non-optical diagnostic method for the discharge type and its path length of vacuum interrupters (VI). In this paper, we extend the Td-Vd characteristics up to 100 kV, which is close to the impulse test voltage of VI at 6.6 kV class. Experimental results for different experimental systems and electrode configurations have revealed that at low voltages (Vd < 30 kV), it is possible from the conventional Td-Vd characteristics to identify the flashover discharge path length regardless of the experimental system and electrode configuration. On the other hand, at high voltages (Vd > 40 kV), Td is longer than the expected value based on the conventional Td-Vd characteristics, which may be affected not only by the propagation time of the conductive channel but also by the propagation time of secondary electron avalanche and the developing time of gap discharge.

DOI： 10.23919/CMD54214.2022.9991358

Scopus

その他リンク： https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=iroffice_5964&SrcAuth=WosAPI&KeyUT=WOS:000937794300092&DestLinkType=FullRecord&DestApp=WOS_CPL

異種材料対向電極の真空中コンディショニングにおける放電電荷量と対向電極材料付着の推移

北直樹，小島寛樹，福田英昭，山村健太，早川直樹

令和4年電気学会基礎・材料・共通部門大会 2022年9月13日電気学会基礎・材料・共通部門