研究者詳細 - 大塚　信也

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SF6ガス中のリーダ転移を含む部分放電進展現象の光学計測査読有り

大塚信也,中山裕太,鈴木悠太

電気学会論文誌B（電力・エネルギー部門誌） ( 一般社団法人電気学会 ) 141 ( 2 ) 196 - 206 2021年02月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

This paper described optical phenomena of propagating partial discharges (PDs) including leader transition from streamer discharge in SF6 gas under positive and negative standard lightning impulse voltage. The optical measurement was performed using by special optical instruments like a framing camera composing of three ICCD cameras with optical filters to obtain spatial- or time-resolved spectroscopic images, a streak camera for a streak image or streak spectrum with a spectroscope, and a phot-multiplier tube (PMT) for light emission intensity, together with PD current and applied voltage waveform measurement by controlling the gate timing of the framing and streak cameras. As a result, typical optical properties to understand the leader transition based on stem or precursor mechanism were clarified, and optical features to identify the streamer and the leader discharge as well as the precursor that has not yet led to leader transition were found. These new findings could contribute to better understanding of PD mechanism as well as improvement of PD diagnostics of gas-insulated switchgear.

DOI： 10.1541/ieejpes.141.196

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SF6ガス中部分放電電流パルス波形のピコ秒立ち上がり時間特性とその形成メカニズム査読有り

大塚信也,小坪俊勝

電気学会論文誌A ( 一般社団法人電気学会 ) 141 ( 1 ) 40 - 47 2021年01月

担当区分：筆頭著者記述言語：日本語掲載種別：研究論文（学術雑誌）

This paper described partial discharge (PD) current waveforms in SF gas measured with a super high frequency wideband measurement system (SHF_PDPW system) with changing the electrode system to control the electric field utilization factor in order to statistically clarify the steeped pulse properties of the negative PD current pulses with a few tens picosecond order at the rising part, i.e. the minimum measured rise time was 30ps and the averaged ones were 45ps to 513ps depending on the utilization factor. The formation mechanism of such picosecond steeped rising part was discussed based on ionization process and electron movement in the critical electric filed by taking the influence of electron mobility as well as the frequency properties of the measurement system into consideration. 6

DOI： 10.1541/ieejfms.141.40

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Partial Discharge Detection of Multiple-Narrow Band Antenna under the Radio Communication Noise 査読有り

Bandi T., Ohtsuka S.

IEEJ Transactions on Electrical and Electronic Engineering 16 ( 5 ) 715 - 721 2021年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

The ultra-high frequency (UHF) method is attempted to diagnose the insulation condition of high voltage equipment as detecting partial discharge (PD) – emitted electromagnetic (EM) wave. Although the EM wave caused by PD has broadband, the UHF band includes many communication and broadcasting line spectral frequencies, which can affect PD detection as a noise. The authors have developed the multiple-narrow band (MNB) antenna to detect discharge signals with high resistance against noisy line spectral frequencies. In this paper, the MNB antenna was applied to measure PD in SF gas and compared with a standard wide-band Horn antenna to identify the PD detection ability. Furthermore, the MNB antenna was applied to measure PD signal in SF gas under the artificial and the real communication noise to estimate the noise elimination ability of MNB antenna. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. 6 6

DOI： 10.1002/tee.23351

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FDTD analysis on propagation and TE mode properties of PD-emitted electromagnetic wave in three-phase type GIS with a series arrangement of HVCs 査読有り

Fujimoto T., Ohtsuka S., Shikura T.

IEEJ Transactions on Electrical and Electronic Engineering 16 ( 12 ) 1687 - 1692 2021年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

This article described transverse electric (TE) mode properties of partial discharge-emitted electromagnetic wave propagating in the three-phase type gas insulated switchgear (GIS) with a series arrangement of high voltage conductors that was calculated by finite difference time domain (FDTD) method. In the calculation, comparison of TE mode properties between single and three-phase type GISs as well as discussion on influences of defect position and sensor position were carried out. Also, approximation equation was proposed to obtain the cut-off frequencies of TE modes in the three-phase type GIS. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

DOI： 10.1002/tee.23471

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FDTD analysis on propagation and TE mode properties of PD emitted electromagnetic wave in three phase type GIS with a series arrangement of HV conductors

Tatsuki Fujimoto, Shinya Ohtsuka, Tatsuyuki Shikura

12nd International Workshop on High Voltage Engineering(IWHV2020) ( IEEJ ) 2020年11月

Properties of Developing Tree in Silicone Gel Observed by High Speed Camera and Detection of Emitted Electromagnetic Waves 査読有り国際誌

Yusuke Oishi, Shinya Ohtsuka

The 8th International Conference on Condition Monitoring and Diagnosis 2020(CMD2020) ( IEEE ) 507 2020年10月

Partial Discharge Properties in XLPE Block Sample with Electric Tree Defect and Difference in Charge of PD Properties Observed between IEC60270 and the UHF Method 査読有り

Furuie H., Yamauchi T., Ohtsuka S.

Proceeding - 8th International Conference on Condition Monitoring and Diagnosis, CMD 2020 158 - 161 2020年10月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

2020年10月25日 - 2020年10月28日

XLPE power cables are widely used in the transmission and distribution network and required high reliability for the stable and safety operation in the power system. This paper described partial discharge properties of XLPE block sample with a needle stuck defect, which eventually initiated electric tree by applying ac high voltage, measured with two methods: one is a conventional method followed by IEC60270 standard (IEC method) and the other is the UHF method to measure the emitted electromagnetic waves. In the IEC method, the authors have used PD measurement systems (OMICRON, MPD600) and measured the signals through a high-frequency current transformer, CT, a coupling capacitor unit, CC and an HA antenna with a UHF unit. Applying the system, the phase-resolved PD pattern, and its time change pattern for the XLPE samples were observed. In the UHF method, we used the HA antenna and a MA antenna, and a digital oscilloscope. Using the fast flame function of the oscilloscope, we observed the time change of PD-emitted electromagnetic waves together with the IEC method measurement. As a result, in the IEC method, the observed signals by the CC and CT were identical in PD pattern and the intensity, and their properties changed depending on the sample condition even in the tree initiation condition. However, the remarkable change was not found during the developing tree condition. To investigate this property further, we investigated the properties by the UHF method and compared them together with the PD current waveform measurement. Based on the PD current properties, the advantage of the UHF method and problem of the IEC method were discussed so as to evaluate the PD properties even in the developing tree condition.

DOI： 10.1109/CMD48350.2020.9287248

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Developing of Multiple-narrowband Antenna to Detect Partial Discharge-emitted Signal under Radio Communication Noise Environment 査読有り

Bandi T., Tanaka M., Furuie H., Ohtsuka S.

Proceeding - 8th International Conference on Condition Monitoring and Diagnosis, CMD 2020 154 - 157 2020年10月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Partial discharge (PD) detection is important for high voltage equipment to monitor insulation condition. Ultra-high frequency (UHF) antenna are used as a sensor to detect PD-emitted electromagnetic wave in the UHF band. However, some radio communication and broadcasting signals could affect PD detection as noise, having line spectra. Based on this reason, the authors developed a multiple narrowband (MNB) antenna, which can eliminate the interference of the communication frequencies, selectively. In this paper, PD detection and noise elimination abilities of the MNB antenna are investigated by measuring PD in SF6 gas under the radio communication noise. The measurement results demonstrated that the MNB antenna is suitable to detect PD under the communication noise.

DOI： 10.1109/CMD48350.2020.9287228

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Properties of developing tree in silicone gel observed by high speed camera and detection of emitted electromagnetic waves 査読有り

Oishi Y., Ohtsuka S.

Proceeding - 8th International Conference on Condition Monitoring and Diagnosis, CMD 2020 162 - 165 2020年10月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

We investigated tree development phenomena leading to a breakdown in silicone gel under the non-uniform electric field with a high-speed video camera. As a result, the tree developed stepwise, and its developing speed was similar with that in the silicone oil as subsonic speed. This phenomenon can be explained by that the tree (cavity) formed by discharges was a conductive condition which was supported by the result of electromagnetic waves during the tree development.

DOI： 10.1109/CMD48350.2020.9287285

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A Multiple Narrow Band Antenna for Detection of Discharge-Emitted Electromagnetic Waves for Insulation Diagnostic 査読有り

Bandi T., Ohtsuka S.

IEEJ Transactions on Electrical and Electronic Engineering 15 ( 12 ) 1751 - 1757 2020年09月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. Partial Discharge (PD) detection is an effective tool to diagnose the insulation condition of high voltage (HV) equipment. Among detection methods of PD, the ultra-high frequency (UHF) method is distinguished by high sensitivity and safety operation. However, the UHF band includes many communication and broadcasting line spectral frequencies, which can be interference against the UHF method. From the point of view of the reduction of interferences, the authors proposed the multiple narrow band (MNB) antenna, which can detect PD signals with high sensitivity and eliminate the line spectral noise frequencies. In this paper, a new MNB antenna was evaluated based on fundamental properties and fabricated, then applied to detect discharge signals emitted from breakdown phenomena. The results demonstrated that the fabricated MNB antenna had a good omnidirectional radiation pattern and similar sensitivity with a standard wide-band Horn antenna. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

DOI： 10.1002/tee.23249

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相分離型GIS のような同軸円筒構造体におけるTEモード遮断周波数の近似解と解析解の相違査読有り

大塚信也，四蔵達之

電気学会論文誌B（電力・エネルギー部門誌） ( 電気学会 ) 140 ( 9 ) 687 - 693 2020年09月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

This paper described difference in cutoff frequency of TEm1 modes between the conventional approximate solution followed by the radii of the inner and outer conductors and the analytic solution in the co-axial structure as a single-phase GIS. The analytic solutions were calculated by the Bessel function based on the boundary condition and confirmed the validity by the FD-TD method in the same size structure. As a result, the approximate solution for the TE11 mode is available while the higher modes above TE21 modes are not available when the difference in the inner and outer conductor radii was increased. Thus, a new approximate equation is introduced, which allows us to obtain more precise result rather than the conventional one.

DOI： 10.1541/ieejpes.140.687

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Comparison of partial discharge-emitted electromagnetic waves between CO<inf>2</inf>, dry air, N<inf>2</inf> and SF<inf>6</inf> by using FDTD analysis 査読有り国際誌

Marina Tanaka, Tomoya Shiraishi, Shinya Ohtsuka, Hiroyuki Hama, Kiyoshi Inami, Shigemitsu Okabe, Takashi Yamamoto

Lecture Notes in Electrical Engineering ( International Symposium on High Voltage Engineering (ISH2019) ) 599 LNEE 1295 - 1302 2020年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Hungary Budapest 2019年08月26日 - 2019年08月30日

SF gas has been widely used in the gas-insulated switchgear (GIS) as an insulation gaseous media because of its excellent insulation and arcquenching performances. However, SF gas has the global warming potential (GWP). In view of reducing the environmental impact, researches on the SF alternatives have been carried out. Non-SF gases or gas mixtures using naturalorigin gases and fluorinated gases are highlighted as new SF alternatives, and their dielectric and arc-quenching performances as well as the EHS (Environment Health Safety) aspects are examined. The authors have focused on the natural-origin gases such as CO , dry Air and N for their very low GWP, and investigated not only their insulation performance like partial discharge (PD) inception and breakdown voltages, but also the PD-emitted electromagnetic (EM) wave properties for insulation diagnostics, under the same electrode systems along with SF . In this study, the authors investigated the PD-emitted EM waves for the SF alternatives for CO , dry Air and N and SF with the 5 different types of antennas whose frequency bands were covered from the VHF to UHF bands. The authors also analyzed the gas type and antenna type dependence of the measured PD-emitted EM waves by the FDTD method based on the PD current waveforms. It was clearly shown that the emitted EM wave properties could be understood by the nature of emission of RF signal and PD current shapes depending on the gas type. 6 6 6 6 6 2 2 6 6 2 2 6

DOI： 10.1007/978-3-030-31680-8_124

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Influences and behaviour of a water droplet on breakdown properties in the mineral oil observed by a high-speed camera and a coupled analysis of the electric field and fluid 査読有り

Yamauchi T., Shibata H., Ohtsuka S.

Lecture Notes in Electrical Engineering 599 LNEE 1266 - 1275 2020年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Hungary Budapest 2019年08月26日 - 2019年08月30日

Power transformers insulated with papers and insulation oil are needed to pay an attention to water content because it is known that breakdown and partial discharge inception voltages (BDV and PDIV) could be decreased as which the water content increased. Since there is a saturation level of water content in the oil, water droplets could appear if the content level exceeded the saturation one. There are many researches on the influences of water content in the insulation oil on the PDIV or BDV as well as the movement and deformation of a water droplet under the uniform or quasi-uniform electric field. However, relationship between the water droplet behavior and breakdown phenomena under the non-uniform electric field has not been made clear. The purpose of this study is to clarify the influences and behavior of a water droplet in the mineral oil on breakdown properties. From this point of view, the authors investigated influences of the water droplet on BDV, and how the water droplet could lead to breakdown in view of its movement and deformation by the observation with a high-speed video camera. As a result, the breakdown occurred several times at once and the BDV and the breakdown path were influenced by the existence of the water droplet. Furthermore, the movement and deformation of the water droplet under the non-uniform electric filed were analyzed as a coupled analysis and compared with the high-speed camera results.

DOI： 10.1007/978-3-030-31680-8_121

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Breakdown light emission spectrum of mineral oil including a water droplet observed with a spectroscope and optical sensors attached with a colour filter 査読有り

Shibata H., Yamauchi T., Yoshida K., Ohtsuka S.

Lecture Notes in Electrical Engineering 599 LNEE 983 - 990 2020年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

It is well known that breakdown (BD) and partial discharge (PD) inception voltages in mineral oil could be decreased as which water content increased. The authors have investigated influences of water content in the mineral oil on the PD and BD properties, together with the movement and deformation of a water droplet leading to BD by a high-speed video camera. In this study, the author investigated light emission properties of the mineral oil at BD observed by the high-speed video camera and a spectroscope with taking influences of the water droplet into consideration. The BD took place intermittently many times at once in the same path that was formed along with the enlarging water droplet. At this time, changes of the light emission color in the BD path was clearly observed, which seemed to correspond to optical wavelengths (colors) of line spectra of hydrogen; Hα, Hβ and Hγ, as well as band spectra of molecules related to C and CH system. In order to confirm these spectra, the authors observed the wavelengths with the spectroscope during the BDs. Also, the authors constructed a new optical measurement system with photo-multiplier tubes (PMTs) that were attached with a color filter to enable to selectively measure the time-change of the spectrum intensity. These results are expected to become a basic data and would be applied to the condition monitoring of oil-insulated high voltage apparatus such as power transformers and bushings.

DOI： 10.1007/978-3-030-31680-8_95

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Spectroscopic Techniques to Evaluate an Ignitable Spark from a CFRP Specimen with a Fastener Under the Lightning Strike Test 査読有り国際誌

Shinya Ohtsuka, Shouichi Kamoda, Kou Tokumasu, Takayuki Nishi

International Conference on Lightning and Static Electricity（ICOLSE）2019 No.88 2019年09月

Relationship Between Spark Direction and Carbon Fiber Direction from a Fastener Jointed CFRP structure 査読有り国際誌

K. Tokumasu, T. Yamauchi, Y. Oisi, S. Ohtsuka, T. Nishi

International Conference on Lightning and Static Electricity（ICOLSE）2019 No.90 2019年09月

Breakdown Light Emission Spectrum of Mineral Oil Including a Water Droplet Observed with a Spectroscope and Optical Sensors Attached with a Color Filter 査読有り国際誌

Hiroki Shibata, Tatsuhiro Yamauchi, Keisuke Yoshida, Shinya Ohtsuka

Proceedings of the 21st International Symposium on High Voltage Engineering ( 935 ) 2019年08月

Construction of the SHF Test Apparatus to Measure the Partial Discharge Current Waveforms in the Practical Operation Conditions of Power Transformer and Application to Influence of BTA Addition 査読有り国際誌

Shibata H., Kotsubo T., Yamauchi T., Ohtsuka S.

2018 IEEE Electrical Insulation Conference, EIC 2018 182 - 185 2018年10月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2018 IEEE. Insulation diagnosis and partial discharge (PD) test have been performed from the viewpoint of operational reliability and quality evaluation of high-voltage electrical power apparatus. The Ultra high frequency (UHF) method that measures the PD-emitted electromagnetic (EM) waves with UHF band (0.3-3 GHz) components is known as one of powerful methods of insulation diagnosis based on PD detection for highvoltage electrical power apparatus. To improve the UHF method, accurate measurement of PD current pulse is quite important because the PD current is a radiation source of the EM wave. Therefore, we have developed the SHF-PDPW (super high frequency wideband PD current pulse waveform measurement) system that enables us to obtain accurately waveforms up to SHF band (3-30 GHz). Using this system, we have investigated PD characteristics such as PD current pulse waveforms in mineral oil used as insulation oil for transformer. As a result, this system could observe the PD phenomena which were a few tens picoseconds order rise time, i.e. undetectable ones in the conventional measurement band. It is necessary to investigate the insulation oil considering practical operation conditions such as degassing, oil temperature change, generation of the combustible gas by discharge and heating oil, addition of additives like 1,2,3-benzotriazole (BTA) and so on, in order to improve the operation method and the reliability of it. In this study, we constructed the new experimental system which could investigate PD properties under the practical conditions of the power transformer. Then, as a first step, we investigated influence of BTA additive on PD characteristics of insulation oil measured by the SHF-PDPW system. BTA has been widely used in transformer oil in Japan. The BTA addition was specified in the Japanese standard (JIS C 2320) in 1988 in order to decrease electrostatic charging. As a result, it could be confirmed that the usefulness of developed experimental system and the influence of BTA additive on PD characteristics.

DOI： 10.1109/EIC.2018.8481039