Details of a Researcher - SAKODA Tatsuya

Suppression of Transformer Inrush Current by Applying Lower Frequency and Lower Voltage Reviewed

Study on Temporal Variation in Shape of Water Droplet on Silicone Rubber Surface Treated by Surface Discharge Reviewed

May oo Khin, Nonoka Hirose, May Thin Khaing, Tatsuya Sakoda, Yoshiki Nakayama, Kota Niwa

IEEE Transactions on Dielectrics and Electrical Insulation 2026.3

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

DOI： 10.1109/TDEI.2026.3677859

Partial discharge behavior in epoxy resin including insulation paper Reviewed

Swe Zin Linn Htet, Takuya Kondo, Takuma Miyake, May Thin Khaing, Tatsuya Sakoda

Journal of Electrostatics 140 1 - 15 2026.3

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

Nishijima Kanta, Khaing May Thin, Sakoda Tatsuya, Kamesawa Tomoyuki, Yamamura Syunichiro, Nishimura Toi, Terashi Kohei

IEEJ Transactions on Power and Energy 145 ( 8 ) 496 - 501 2025.8

Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Inrush current phenomenon of a three-phase transformer is caused by mismatching polarities and absolute values of the initial magnetic flux induced by residual flux remnants in each phase core before the transformer is energized. Because the residual flux is the final value of magnetic flux transients that occur immediately after disconnection, the inrush current can be suppressed by considering the residual flux and controlling the timing of a circuit breaker. However, when a transformer is first energized in the field, the residual flux is unknown.In this study, we apply lower frequency and lower voltage to a transformer system simulating a three-phase transformer and then integrates the transformer voltage by time to digitally calculate and capture the true residual flux. Next, when the transformers are energized, a phase angle control is applied to the timing of a switch to effectively suppress inrush current. As a result, the usefulness of the lower frequency and lower voltage application to suppress inrush current is indicated.

DOI： 10.1541/ieejpes.145.496

Investigation of Partial Discharges in Epoxy Resin with Horizontally and Vertically Aligned Two Voids Reviewed

Linn Htet S.Z., Khaing M.T., Sakoda T., Harada Y., Shibata T., Miyazaki K.

2025 IEEE 5th International Conference on Electrical Materials and Power Equipment Icempe 2025 2025.8

Authorship：Corresponding author Language：English Publishing type：Research paper (international conference proceedings) Publisher：2025 IEEE 5th International Conference on Electrical Materials and Power Equipment Icempe 2025

Partial discharge (PD) activity significantly affects the reliability of insulation systems, with void positioning in epoxy resin playing a critical role in molded transformers. This study investigates the influence of PD in epoxy resin containing two artificial voids (1 mm in diameter) arranged in horizontal and vertical alignments, focusing on PD characteristics, electrical treeing behavior, and breakdown mechanisms. PD activity and electrical tree were monitored using a high-frequency current transformer (HF-CT) sensor and a transient earth voltage (TEV) sensor. The results indicate that void alignment strongly influences PD inception, discharge intensity, and propagation patterns. FFT (Fast Fourier Transform) spectrum analysis revealed distinct differences between the two configurations in vertically and horizontally aligned voids. Furthermore, electrical treeing was observed in the horizontally aligned voids, leading to breakdown. However, in vertically aligned voids, electrical treeing was difficult to detect, and a breakdown occurred suddenly. These findings highlight that void alignment significantly influences PD behavior and breakdown progression, providing valuable insights for improving insulation design and diagnostic techniques in high-voltage applications, contributing to the development of more reliable insulation systems.

DOI： 10.1109/ICEMPE66159.2025.11122978

Evaluation of the Degradation Degree of 20-Year-aged Insulator by Using Surface Discharge Reviewed

Khin M.O., Nonoka H., Khaing M.T., Sakoda T., Nakayama Y., Niwa K.

2025 IEEE 5th International Conference on Electrical Materials and Power Equipment Icempe 2025 2025.8

Polymer insulator wherein silicone rubber (SiR) is used as housing material are exposed to various environmental stresses such as ultraviolet (UV) radiation, high temperatures, and pollution, which can lead to degradation over time. Assessing the degree of this degradation is crucial for the long-term maintenance of polymer insulators. This study proposes a novel technique to evaluate the degradation degree of SiR. To effectively expose PDs to specific locations on the SiR surface, we generated surface discharges (SDs). We compared hydrophobicity recovery times between an unused SiR specimen and aged SiR specimens. Our approach involves analyzing the hydrophobicity recovery time after SD treatment. SD treatment temporarily reduces the surface hydrophobicity of SiR, and by measuring the time required for hydrophobicity to recover, we can assess its degradation. Experiments were conducted on SiR specimens extracted from unused, and 20 -year-aged polymer insulators. The SD treatment was applied for 10s. Following each treatment, the contact angle was measured at 5 -minute intervals. Then, we characterized the physical or chemical damage on SiR specimens after the SD treatment using a scanning electron microscope (SEM), and an attenuated reflection-Fourier transform infrared spectroscopy (ATR FTIR). These findings indicate that the contact angle recovery time after SD treatment serves as a valuable parameter for assessing the degradation degree of SiR insulators.

DOI： 10.1109/ICEMPE66159.2025.11123124

EVALUATION OF DEGRADATION DEGREE OF ARTIFICIALLY DEGRADED SILICONE RUBBER SURFACE Reviewed

Evaluation of Degradation Degree on Silicone Rubber by Using Surface Discharge Reviewed

May Thin Khaing, Nonoka Hirose, Takuma Miyake, Tatsuya Sakoda, Shigehiko Goto, Tomikazu Anjiki, Tomoki Chiba

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING ( 20 ) 998 - 1005 2025.7

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

DOI： 10.1002/tee.24256

Nakayama Y., Niwa K., Khaing M.T., Sakoda T.

Iet Conference Proceedings 2025 ( 14 ) 1067 - 1071 2025.6

Authorship：Corresponding author Language：English Publishing type：Research paper (international conference proceedings) Publisher：Iet Conference Proceedings

Polymer materials such as silicone rubber (SiR) have been used as housing material for insulators in distribution lines, however because polymer insulators are more expensive than porcelain insulators in Japan, their application is still limited. If their price can be reduced, there is potential for the installation of polymer insulators to accelerate. One way to reduce the cost is to improve the materials. Finding optimal alternative materials, requires grasping the extent to which such materials resist degradation during long-term use. In this study, we first propose a method for making degraded surfaces that resemble the surface characteristics of aged insulators. Additionally, we propose a method for evaluating the degree of surface degradation at which surface discharge (SD) is generated for a short time on the SiR surface. These two methods can contribute to the introduction of new materials for polymer insulators.

DOI： 10.1049/icp.2025.1766

Section Locating of Water-Tree Degraded Cable by Measuring Residual Charges Induced by Induced Voltage Pulses Reviewed

Watanabe K., Sakoda T., Takahashi A., Negishi N., Miyazaki K.

Electrical Engineering in Japan English Translation of Denki Gakkai Ronbunshi 218 ( 2 ) 2025.6

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Electrical Engineering in Japan English Translation of Denki Gakkai Ronbunshi

To establish a novel section locating technique for a water-tree degraded 22 kV cross-linked polyethylene (XLPE) cable, that is, included in another undegraded cables, we measured a reflected injection pulse at the impedance mismatch, which is dependent on water trees. The injection pulse was propagated into cables to be measured, and the measured arrival times of reflected pulses containing residual charges due to water trees were varied depending on the locations of water-tree degraded cables. The section locating was achieved by using the arrival time of the reflected pulse.

DOI： 10.1002/eej.23506

Locating Water-tree Degraded Cable Section by Measuring Residual Charges Induced by Voltage Pulse Wave Reviewed

May Thin Khaing, Watanabe Koki, Sakoda Tatsuya, Takayama Toru, Miyazaki Kazunori

IEEE Transactions on Dielectrics and Electrical Insulation 32 ( 5 ) 2915 - 2921 2025.2

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

A residual charge method is useful for measuring water tree in 22-kV crosslinked polyethylene (XLPE) cable systems. However, the conventional residual charge method cannot locate a water-tree degraded cable section because the time-resolved signal response from a water-tree degradation section cannot be obtained. In this study, we inject a sine wave pulse with a frequency of 1 MHz into measuring object cables when ac voltage is applied to the cables to release trapped charges due to the water-tree. We examine to locate a water-tree degraded cable section in 22-kV XLPE cable systems, including water-tree degraded cables and a Y-branch cable joint. The time-resolved residual charges induced by the voltage pulse induced by an injection coil (IJ coil) can locate a water-tree degraded cable section.

DOI： 10.1109/TDEI.2025.3545010

Evaluation of Degradation Degree on Silicone Rubber by Using Surface Discharge Reviewed

Khaing M.T., Hirose N., Miyake T., Sakoda T., Goto S., Anjiki T., Chiba T.

IEEJ Transactions on Electrical and Electronic Engineering 20 ( 7 ) 1 - 8 2025.1

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Electrical and Electronic Engineering

Silicone rubber (SiR) insulators in outdoor may be degraded owing to multiple environmental stresses such as ultraviolet (UV) rays, high temperature and pollution adhesion. Evaluation of the degradation degree of SiR can contribute to the long-term maintenance of SiR insulators. We proposed a novel technique to grasp the degradation degree of SiR. The surface discharge (SD) on the SiR surface temporarily decreased the surface hydrophobicity, and then the hydrophobicity recovery time was evaluated. The SD treatments were performed on SiR specimens cut out from unused, 10 and 20-year-aged SiR insulators, and the treatment time was from 5 to 25 s. After each SD treatment, the contact angle was evaluated at intervals of 10 min. As a result, it was found that the contact angle recovery time increases with the increase of SD treatment time. Also, the contact angle recovery times on 10 and 20-year-aged SiR specimens were longer than that on an unused SiR specimen, i.e. the contact angle recovery time after the SD treatment is useful for investigating the degradation degree. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

DOI： 10.1002/tee.24256

Section Locating of Water-tree Degraded Cable by Measuring Residual Charges Induced by Induced Voltage Pulses Reviewed

Watanabe Koki, Sakoda Tatsuya, Takahashi Akira, Negishi Naoyuki, Miyazaki Kazunori

IEEJ Transactions on Fundamentals and Materials 145 ( 1 ) 23 - 29 2025.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

To establish a novel section locating technique for a water-tree degraded 22 kV cross-linked polyethylene (XLPE) cable that is included in another undegraded cables, we measured a reflected injection pulse at the impedance mismatch which is dependent on water trees. The injection pulse was propagated into cables to be measured, and the measured arrival times of reflected pulses containing residual charges due to water trees were varied depending on the locations of water-tree degraded cables. The section locating was achieved by using arrival time of the reflected pulse.

DOI： 10.1541/ieejfms.145.23

Partial Discharge and Electrical Treeing Phenomena Within Two Spherical Voids in Epoxy Resin Reviewed

Htet S.Z.L., Kondo T., Khaing M.T., Sakoda T., Harada Y., Takei K., Ikeda M., Miyazaki K.

2024 10th International Conference on Condition Monitoring and Diagnosis, CMD 2024 358 - 361 2024.10

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：2024 10th International Conference on Condition Monitoring and Diagnosis, CMD 2024

Partial discharge (PD) and electrical treeing phenomena in an epoxy resin electrode which had two spherical voids and the insulation paper were investigated. The alignment of the two voids was vertical against the applied electric field direction, and experiments with not only two voids of the same size (diameter of 1 mm) but also two voids of different size (diameters of 1 mm and 1.5 mm) were carried out. AC high voltage was applied until the breakdown occurred in the epoxy resin electrode. PD and electrical treeing phenomena were detected by using a high frequency current transformer (HF-CT) sensor, a transient earth voltage (TEV) sensor and an ultra-high frequency (UHF) sensor. We here focused on variations of the number of PDs per unit time and frequency components of detected signals with the elapsed time from the voltage application. As a result, we investigated a unique electrical tree development characteristic which differed in the size of two voids. Although the electrical tree development was temporarily decelerated by the insulation paper, the breakdown suddenly occurred from a point of high electric field in the insulation paper. Additionally, we investigated the temporal variations of the number of PDs which differed in the combination of the void size.

DOI： 10.23919/CMD62064.2024.10766291

Diagnosis of Degradation Degree on SiR Surface Used for Insulator by Surface Discharge Reviewed

Khaing M.T., Miyake T., Sakoda T., Goto S., Anjiki T., Chiba T., Kasuga Y.

2024 10th International Conference on Condition Monitoring and Diagnosis, CMD 2024 386 - 389 2024.10

Authorship：Corresponding author Publishing type：Research paper (scientific journal) Publisher：2024 10th International Conference on Condition Monitoring and Diagnosis, CMD 2024

Silicone rubber (SiR) insulators have been mostly preferred for high-voltage transmission and distribution lines because of their superior hydrophobicity characteristic. Hydrophobicity of SiR insulators may be, however, degraded by multiple stresses and may eventually lead to dry band arcing. Hence, a diagnostic technique of degradation degree on SiR surface will be useful for the long-term maintenance of SiR insulators. In this study, the artificially degraded layers were first made on two SiR surfaces by red clay adhesion, UV irradiation and surface heating. To diagnose the degradation degree on the SiR surface, an unused SiR surface, two artificially degraded SiR surfaces (Sample A (UV, Heating) and Sample B (Heating, UV)) and two aged SiR surfaces (10-year-aged and 20-year-aged) were exposed to a surface discharge (SD) source. The applied voltage and treatment time of SD against the experimental SiR surfaces were 8 kVp-p and 10 s, respectively. After the SD treatment, the hydrophobicity recovery time of each experimental SiR surface was evaluated with the contact angle of a water droplet on the SiR surface. Then, monitoring of water-repellent maintenance (i.e., the contact angle of water droplets on the SiR surface remaining in stable condition) on each experimental SiR surface was also conducted. It was found that the hydrophobicity recovery times and water-repellent change times (duration of contact angle of water droplets on the SiR surface in stable condition) of Sample A (UV, Heating) and Sample B (Heating, UV) were similar to those of 10-year-aged and 20-year-aged SiR surfaces, respectively. Additionally, water-repellent change times of Sample B (Heating, UV) and 20-year-aged SiR surfaces were shorter compared with those of Sample A (UV, Heating) and 10-year-aged SiR surfaces.

DOI： 10.23919/CMD62064.2024.10766183

Characterization of Surface Discharge Used for Measuring Degradation Degree of Polymer Insulator Reviewed

Khaing M.T., Miyake T., Sakoda T.

Proceedings of the IEEE International Conference on Properties and Applications of Dielectric Materials 254 - 257 2024.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of the IEEE International Conference on Properties and Applications of Dielectric Materials

Polymer insulators with silicone rubber (SiR) insulation have unique properties and are installed all over the world. However, due to pollution deposits on the surface, the characteristics of polymer insulators become degraded. We have already investigated that the degradation degree of the polymer insulator can be evaluated by a 20-cycle salt-fog aging test or a surface discharge (SD) treatment. However, the decrease mechanism of the contact angle by such discharge treatment wasn't interpreted in detail. In this study, to characterize SD generated on the surfaces of SiR, we first measured the SD current. The observed maximum SD current did not significantly differ from that obtained during the 20-cycle-salt-fog aging test. In addition, the SD consisted of filamentary discharges. In measurements of optical emissions, emissions with wavelengths of less than 291 nm which can cut C-H bond of SiR weren't observed. Therefore, it is thought that the direct energy transfer from energetic particles with higher energy than the binding energy of C-H changes chemical characteristics and decreases the contact angle on the SiR surface.

DOI： 10.1109/ICPADM61663.2024.10750781

Partial Discharge Behavior Prior to Breakdown in Epoxy Resin Reviewed

Htet S.Z.L., Kondo T., Miyake T., Sakoda T., Nishimura T.

IEEJ Transactions on Electrical and Electronic Engineering 19 ( 12 ) 1927 - 1935 2024.7

Authorship：Corresponding author Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Electrical and Electronic Engineering

To evaluate the deterioration degree of insulation material by monitoring partial discharges (PDs), it is necessary to fully understand the PD behavior prior to breakdown. We performed measurements of temporal variations in the number and magnitude of PDs in a void of epoxy resin. It was found that the number of PDs with larger magnitude is less before breakdown and that there is a decreased tendency of the number and magnitude of PDs with the elapsed time. The tendency is remarkable as the applied electric field is small. Additionally, the time to breakdown becomes short when the scattering of the number of PDs per unit time decreases. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

DOI： 10.1002/tee.24160

Voltage and Current Characteristics of Schottky Barrier Diodes and Rectifier Diodes Exposed to Standard Lightning Impulse Voltage Reviewed

Ko T.Z.W., Torihara R., Sakoda T., Hayashi N.

IEEJ Transactions on Electrical and Electronic Engineering 19 ( 6 ) 1105 - 1112 2024.6

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Electrical and Electronic Engineering

Lightning surges are one of the major reasons of bypass diode (BPD) failure in photovoltaic modules. In this study, standard lightning impulse voltages (SLIVs) were directly applied to Schottky barrier diodes (SKB diodes) and rectifier diodes (PNJ diodes) with different electrical specifications. The critical voltages Vc of SLIV at which the diodes were damaged and the temporal variations of diode current (iD) and voltage (vD) were measured. It was found the iD-vD characteristics can be categorized into a total of eight patterns: four patterns for the forward SLIV application and the four for the reverse SLIV application, regardless of diode types. The measured results imply that the irreversible voltage dip that occurs before the termination of the reverse breakdown contributes significantly to diode damage in the both forward and reverse SLIV applications. SKB diodes exposed to the reverse SLIV are easily damaged at the lowest magnitude of SLIV among all combinations of diode types and SLIV directions. Once a diode has been damaged due to the first SLIV application, the second application of SLIV to the same diode causes remarkable change in the iD-vD characteristic even if the magnitude of the second SLIV is smaller than Vc. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

DOI： 10.1002/tee.24064

Short-time Fabrication of Degraded Surface on Silicone Rubber Used for Insulators Reviewed

Khaing M.T., Yoshimura K., Miyake T., Sakoda T., Goto S., Anjiki T., Chiba T., Kasuga Y.

IEEE Transactions on Dielectrics and Electrical Insulation 31 ( 2 ) 1054 - 1061 2024.4

Publishing type：Research paper (scientific journal) Publisher：IEEE Transactions on Dielectrics and Electrical Insulation

Silicone rubber (SiR) insulators are degraded due to multiple stresses. To develop a degradation diagnostic technique, a lot of aged insulators are required. However, collecting a lot of several decades of used SiR insulators is difficult. Therefore, it is desired to fabricate the degraded SiR surface whose characteristics are similar to those of degraded SiR insulators in outdoor. To grasp characteristics of the degraded SiR surface, we first investigated characteristics of aged SiR insulators. Foreign matters on aged SiR specimens made the contact angle larger, and Si-O, Si-CH3, C-H, and O-H bonds decreased. Next, to fabricate the artificially degraded SiR surface, we proposed a 24 h – fabrication - cycle which consists of a red clay adhesion process, a UV irradiation process, a surface heating process, a heat radiation process, and a surface cleaning process. We evaluated effects of the UV irradiation and the surface heating, and then it was found that a combination of UV irradiation for breaking molecular structure and surface heating for promoting LMW dispersion played an important role in adhering red clay to SiR. The contact angle and the chemical structure on the artificially degraded SiR surface, which was fabricated by UV irradiation for 6 h and surface heating at 20°C or 40°C, were similar to those of a SiR specimen aged 10 years with the hydrophobicity of HC 2.

DOI： 10.1109/TDEI.2023.3329789

Characteristics of Aged Silicone Rubber Insulators Used in Outdoor for 20 Years Reviewed

Khaing M.T., Yoshimura K., Miyake T., Sakoda T., Kanenari U., Nishihiro Y.

Ieej Transactions on Electrical and Electronic Engineering 19 ( 4 ) 454 - 460 2024.4

Publishing type：Research paper (scientific journal) Publisher：Ieej Transactions on Electrical and Electronic Engineering

To collect aged silicone rubber (SiR) insulators with different numbers of years in use, which is for developing a degradation diagnostic system of SiR, is difficult. Therefore, it is desired to make degraded SiR surface which has similar characteristics to the degraded surface in outdoor. To realize the fabrication, we characterized the surfaces of aged SiR specimens cut out from a 22 kV line post insulator used in the coastal area for 20 years. The results showed that to introduce fine particles into the surface is necessary for making degraded surface having the minute surface roughness. Additionally, it was found that to activate the dispersion of LMW with foreign matters is also necessary. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

DOI： 10.1002/tee.23991

Evaluation of degradation degree of artificially degraded silicone rubber surface by using surface discharge Reviewed

Khaing M.T., Miyake T., Sakoda T., Kanenari U., Nishihiro Y.

Journal of Electrostatics 128 2024.3

Publishing type：Research paper (scientific journal) Publisher：Journal of Electrostatics

To establish an evaluation technique of the degradation degree of silicone rubber (SiR) surfaces, we first fabricated artificially degraded SiR surfaces. The fabrication process consisted of 5 steps and a 1-cycle test required 24 h. We fabricated the degraded SiR surfaces by a 1-cycle or a 2-cycle test. Next, the artificially degraded SiR surface was exposed to surface discharge (SD). The hydrophobicity recovery time on artificially degraded SiR surface increased with the increase in SD treatment time. It was found that the degradation degree of the SiR surface can be evaluated by hydrophobicity recovery time after SD treatment.

DOI： 10.1016/j.elstat.2024.103898

Characteristics of Aged Silicone Rubber Insulators Used in Outdoor for 20 Years Reviewed

19 ( 4 ) 454 - 460 2024.1

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

Degradation Monitoring of Silicone Rubber Used for Insulators Reviewed

May Thin Khaing, Kosei Yoshimura, Takuma Miyake, Tatsuya Sakoda, Shigehiko Goto, Tomikazu Anjiki, Tomoki Chiba, and Yasunori Kasuga

23rd Int. Symposium on High Voltage Engineering (ISH) 866 - 870 2023.8

Authorship：Last author Language：English Publishing type：Research paper (international conference proceedings)

Formation of Degradation Layer on Silicone Rubber Used for Insulators Reviewed

Khaing M.T., Yoshimura K., Sakoda T., Goto S., Anjiki T., Chiba T., Kasuga Y.

2023 IEEE Electrical Insulation Conference, EIC 2023 2023.6

Language：English Publishing type：Research paper (international conference proceedings) Publisher：2023 IEEE Electrical Insulation Conference, EIC 2023

Silicone rubber (SiR) insulators have been increasingly used for transmission and distribution systems. However, it is concerned that performance and property of SiR insulator in operation are degraded due to multiple stresses. We now aim to develop a diagnosis technique of degradation degree of SiR insulator exposed to the multiple stresses. In order to investigate the degradation characteristics and establish the diagnosis technique, aged specimens are required. However, it is difficult to collect a lot of aged SiR insulators used for more than several decades. Therefore, we tried to fabricate the artificial degradation surface, which is similar to ones obtained from actual fields. To analyze the surface degradation of actually aged SiR insulators, hydrophobicity class (HC) of 22kV-SiR insulators arranged for 10 and 20 years in coastal areas was first evaluated. Next, considering the multiple stresses, the degradation surface was fabricated by red clay, UV ray irradiation and surface heating. Aged SiR specimens and artificially degraded SiR spmecimens were characterized by using a contact angle meter, a scanning electron microscopy (SEM), and an attenuated total reflectance-Fourier transform infrared spectrometer (ATR-FTIR). The hydrophobicity of artificially degraded SiR specimen can be decreased due to red clay adhesion/ surface pollution on its surface as the similar condition as actually aged SiR specimen. It was also found that Si-O bond, Si-CH3 bond and C-H bond can be controlled by UV irradiation and the heating temperature.

DOI： 10.1109/EIC55835.2023.10177357

Influence of Electric Field and Fillers on Electrical Tree Development in Epoxy Resin Reviewed

Kawaguchi Teppei, Sakoda Tatsuya, Nishimura Takeshi

IEEJ Transactions on Fundamentals and Materials 143 ( 2 ) 46 - 53 2023.2

Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

We investigate the influence of electric field in a void of epoxy resin with fillers on development of electrical trees. Not only observations of pits and electrical trees but also measurements of temporal variations of the number of partial discharges (PDs) and the PD magnitude were carried out. It was found that PDs with several hundred pC can be measurement by a CT sensor until the obvious formation of an electric tree is achieved in the case of epoxy resin without fillers. Additionally, when electric field of the tip of a pit is the almost same as the withstand electric field of the epoxy resin, electrical tree and breakdown occur in a very short time. The development of electrical tree is disturbed by fillers in epoxy resin, and the required time for breakdown is much longer than that of epoxy resin without fillers.

DOI： 10.1541/ieejfms.143.46

Influence of impulse corona discharge on discharge time lag of a surge arrester with a spark gap Reviewed

Sakoda T., Kubo K., Mizutani M., Chiba T., Kasuga Y., Fukano T.

Journal of Electrostatics 121 2023.1

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Electrostatics

ZnO surge arrester with a spark gap is used for reducing electrical failures in power distribution systems of Japan. The high responsiveness, the low residual voltage, and the stable operating voltage are required for the arresters. However, the discharge time lag generally occurs in a spark gap. In this study, measurements of V-t characteristics and observations of optical emissions from impulse corona discharges generated at a newly designed small step edge on an inclined plane of each electrode were carried out. The small step edge made the discharge time lag and the standard deviation small. Based on the results, we indicated that the impulse corona discharge improves the discharge time lag of the sparkover.

DOI： 10.1016/j.elstat.2022.103783

Short-time Evaluation Technique of Degradation Degree by Surface Discharge Reviewed

Khaing M.T., Yoshimura K., Sakoda T., Goto S., Anjiki T., Chiba T., Kasuga Y.

IET Conference Proceedings 2023 ( 46 ) 992 - 996 2023

Publishing type：Research paper (scientific journal) Publisher：IET Conference Proceedings

Silicone rubber (SiR) is being adopted as the housing material for insulators. However, the hydrophobic property and the recovery characteristic might be degraded under multiple stress. As one of the degradation diagnosis techniques for the long-term reliability evaluation of SiR, we have proposed a continuous salt fog test in which 20 - times salt fog aging tests by applying ac voltage for 3 h were repeatedly carried out. However, it takes a much longer time. In this study, we examined a novel technique by using surface discharges (SDs) instead of the previous technique. The SDs were generated on the aged SiR surface for 10 s, and then the hydrophobicity recovery time obtained by measuring the contact angle of a water droplet on the SiR was evaluated. The results indicate a possibility that the hydrophobicity recovery time after the SD treatment can refer to the degradation degree of SiR without causing physical and chemical damage.

DOI： 10.1049/icp.2024.0737

Effect of Supercapacitor on Transient Response of Thermoelectric Generation Systems Reviewed

鳥原亮, 迫田達也, 林則行

宮崎大学工学部紀要 51 69 - 77 2022.11

Language：English Publishing type：Research paper (scientific journal) Publisher：宮崎大学工学部

Thermoelectric generators (TEGs) are being used for the harvesting of wasted thermal energy because the TEG converts the temperature difference into the electrical energy. The purpose of this research is to investigate the transient response of electrical properties for TEG systems when the electric load is connected to them. In this study, two kinds of TEG systems were employed; one installed with only a single thermoelectric module (TEM), and another installed with four TEMs and two DC/DC converters (one converter is to track the MPP of the TEMs, and another converter is to regulate the output voltage). An electric double layer capacitor (EDLC) also called a supercapacitor unit was used to improve the transient performance of the two kinds of TEG systems. A filament electric lamp with a non-linear nature of its resistance was employed to investigate the transient responses of the two TEG systems.
Based on the experimental results, the electrical characteristics (voltage, current and power) are studied, and the transient responses of voltage and current as a function of time are analyzed, and the effect of installing the EDLC to the TEG systems are discussed. It is found that the TEG with only a single TEM has high transient responses of voltage and current, large TEG voltage drop during the transient period. Installation of EDLC to the TEG systems can reduce the transient responses of voltage and current and can also reduce TEG voltage drop during the transient period. It is also found that EDLC increases the maximum power at proper load.

Optimal arrangement of TEV sensors for diagnosing oil-filled transformer Reviewed

Sakoda Tatsuya, Mori Wataru

Memoirs of Faculty of Engineering, University of Miyazaki 51 79 - 81 2022.11

Language：Japanese Publishing type：Research paper (scientific journal)

Development of Detection Technique of Residual-charges by Inductive Current Pulse Reviewed

Effect of Supercapacitor on Transient Response of Thermoelectric Generation Systems

Tin Tin Cho, Ryo Torihara, Tatsuya Sakoda, Noriyuki Hayashi

宮崎大学工学部紀要 ( 51 ) 69 - 77 2022.11

Language：English Publishing type：Research paper (bulletin of university, research institution)

Degradation Monitoring of Silicone Rubber Used for Insulators Reviewed

May Thin Khaing, Kosei Yoshimura, Tatsuya Sakoda, Junki Oasa, Shoichi Higashiyama, and Yuko Inaoka

9th International Conference on Condition Monitoring and Diagnosis 2022 382 - 386 2022.11

Authorship：Corresponding author Language：English Publishing type：Research paper (international conference proceedings)

Nakaguchi Ryusei, Sakoda Tatsuya, Kataoka Tatsuya, Okamoto Dai, Tsuiki Ushio, Futagawa Kazuhiro, Satoh Hideaki

IEEJ Transactions on Fundamentals and Materials 142 ( 7 ) 345 - 346 2022.7

Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

To establish a novel section locating technique of water-tree degraded 22 kV cross - linked polyethylene (XLPE) cable, we measured the injected current pulse with residual - charges due to water trees in a XLPE cable which was used for 27 years and removed after performing residual charge measurement. It was found that the current/voltage pulse injected at a prescribed value of AC voltage may carry residual charges reflecting water tree length.

DOI： 10.1541/ieejfms.142.345

Effective Measurement of Elastic Waves due to Partial Discharges in Oil-immersed Transformer Reviewed

Voltage and Current Characteristics of Schottky Barrier Diodes when Application of Standard Lightning Impulse Voltage Causes Breakdown of Them Reviewed

Tinzar Win ko, May Oo Khin, Ryo Torihara, Tatsuya Sakoda, Noriyuki Hayashi

The International Council on Electrical Engineering Conference 2022 642 - 649 2022.6

Language：English Publishing type：Research paper (international conference proceedings)

Change in V-I Characteristics of Schottky Barrier Diodes when Application of Standard Lightning Impulse Voltage Causes Breakdown of Them Reviewed

Swezin Linnhtet, May Oo Khin, Ryo Torihara, Tatsuya Sakoda, Noriyuki Hayashi

The International Council on Electrical Engineering Conference 2022 635 - 641 2022.6

Language：English Publishing type：Research paper (international conference proceedings)

Mori Wataru, Sakoda Tatsuya, Sato Masaharu, Takei Katsutoshi

IEEJ Transactions on Fundamentals and Materials 142 ( 3 ) 124 - 125 2022.3

Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Based on numerical and experimental analyses of sound pressure distributions owing to partial discharges in oil-immersed transformer, we propose an effective arrangement of acoustic emission sensors. The sensor arrangement at the surface edge of the transformer housing allows us to minimize the required time for diagnosing.

DOI： 10.1541/ieejfms.142.124

On-line PD Monitoring System (PDLOOK) for XLPE Cables Reviewed

Akaiwa S., Miyagawa K., Nakashima T., Sakoda T., Miyake T., Takayama A.

2022 9th International Conference on Condition Monitoring and Diagnosis, CMD 2022 703 - 706 2022

Publishing type：Research paper (scientific journal) Publisher：2022 9th International Conference on Condition Monitoring and Diagnosis, CMD 2022

We have developed a continuous remote monitoring system that can monitor partial discharge (PD) trends for a long period of time, which greatly saves the labor in operating. An Edge terminal uploads a signal obtained from the high frequency CT attached to the power cable to a cloud system. In this process, a PD-like signal is effectively discriminated from a large amount of acquired data by using a noise filtering function. The signal data uploaded on the cloud system is PD-judged by AI, and a learning cycle function improves the AI judgment accuracy.

DOI： 10.23919/CMD54214.2022.9991514

Degradation Monitoring of Silicone Rubber Used for Insulators Reviewed

Khaing M.T., Yoshimura K., Sakoda T., Oasa J., Higashiyama S., Inaoka Y.

2022 9th International Conference on Condition Monitoring and Diagnosis, CMD 2022 382 - 386 2022

Publishing type：Research paper (scientific journal) Publisher：2022 9th International Conference on Condition Monitoring and Diagnosis, CMD 2022

Electrical insulation equipment such as insulators contributes to reduction of electrical fault owing to overvoltage. Polymeric material such as silicone rubber (SiR) is gradually replacing porcelain. However, in Japan the application of polymeric material is limited because there are concerns about the hydrophobicity degradation and the decrease of insulation performance. Therefore, it is important to investigate not only pollution effect on the insulation performance but also the long-term reliability of polymeric material. Additionally, it is desired to establish an easy diagnostic technique which can grasp the degree of degradation of polymeric material. To evaluate the degradation degree of SiR of insulators arranged for a long period of time in the coastal area, we first characterized the surface of aged SiR specimen cut out from a line post insulator arrange for 20 years in the coastal area by using the attenuated total internal reflection Fourier transform infrared spectroscopy (ATR-FTIR). Next, we repeatedly performed a salt fog aging test against SiR specimens. Then, the surface hydrophobicity and the leakage current were evaluated. From the ATR-FTIR analysis, it was found that the reflectance peaks due to Si-CH3 symmetric bending of aged specimen decreases in comparison with those of unused specimen. The continuous salt fog aging test investigated that a required time for recovering hydrophobicity is a good index for degradation diagnosis because the required times for recovering hydrophobicity of SiR used for 20 years are much longer than that of unused SiR.

DOI： 10.23919/CMD54214.2022.9991539

Sterilization of stem-end rot of mango using dielectric barrier discharge and investigation of sterilization factors Reviewed

Nakakoga Y., Tada Y., Sakoda T., Tazawa K., Ichikawa H.

Electronics and Communications in Japan 104 ( 4 ) 2021.12

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Electronics and Communications in Japan

To develop a sterilization method for controlling post-harvest stem-end rot of mango, we examined to sterilize fungi on peduncle by using the dielectric barrier discharge (DBD). Additionally, to investigate the sterilization factors, we performed sterilization against stem-end rot on agar medium by using the DBD generated in air, argon gas, or oxygen gas. It was found that the DBD can sterilize fungi with high probability. Ultra-violet ray and O3 do not contribute to the sterilization. High energy electrons, and radicals such as O and OH play an essential role for the sterilization.

DOI： 10.1002/ecj.12325

Evaluation of Surface Degradation of Silicone Rubber by Continuous Salt-fog Aging Test Reviewed

Adachi Kohei, Miyake Takuma, Sakoda Tatsuya

IEEJ Transactions on Fundamentals and Materials 141 ( 10 ) 590 - 596 2021.10

Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

To evaluate the long-term reliability of polymeric material used for housing material of electric power apparatus, we continuously performed a salt-fog aging test against silicone rubber (SiR) specimens cut out from line post insulators arranged for 10 and 20 years in the coastal area. Then, the surface hydrophobicity and the leakage current were evaluated. The results showed that a required time for recovering hydrophobicity and a discharge ignition time until the leakage current is detectable are good indexes for degradation diagnosis. Especially, the required time for recovering hydrophobicity is useful. The required times for recovering hydrophobicity of SiR used for 10 and 20 years were much longer than that of unused SiR.

DOI： 10.1541/ieejfms.141.590

Dynamic I-V Characteristics of Schottky Diodes and PN Junction Diodes When Lightning Impulse Voltage Is Applied on Them Reviewed

迫田達也

宮崎大学工学部紀要 50 105 - 112 2021.9

Language：English Publishing type：Research paper (scientific journal) Publisher：宮崎大学工学部

The purpose of this study is to assist the operation and maintenance of PV systems by studying the resistive conditions of bypass diode used in PV modules and to develop the diagnosis and on-line monitoring system for small and medium scale PV systems. This paper analyzes the breakdown and non-breakdown
characteristics of Schottky diodes and PN Junction diodes by application of various ranges of voltages by Lightning surge simulator (LSS). In this study, we compare and discuss the numerical data of experimental results obtained under variable voltage applications of LSS are compared for both diodes on the resistive
characteristics after breakdown, waveforms of voltage and current and the behaviors of dynamic curves.
An applied voltage, on which the breakdown of diode takes place and dramatic change in I-V characteristics occurs, is called “critical voltage (Vc)”. From the study, it was observed that the magnitude of critical voltage (Vc) of PN junction diodes is higher than that of Schottky diodes in reverse direction although
there is almost the same in forward direction. The authors are also probing that the possibility of more sensitive monitoring and diagnosis system for the resistive bypass diode in PV system based on numerical simulation results. The great difference of Vc is reflected for the dynamic relationship between voltage and current in reverse biasing for both diodes.

Voltage Profi les on HV Distribution Lines with Various Network Confi gurations and Customers Reviewed

迫田達也

宮崎大学工学部紀要 50 95 - 103 2021.9

Language：English Publishing type：Research paper (scientific journal) Publisher：宮崎大学工学部

Electrical power system reliability is a critical issue for utilities and power loss occurred in transmission and distribution network is a must consideration. Electrical distribution system is the largest portion of network in the electrical power system. There is voltage drop on long HV distribution line (D/L) due to heavy load consumption, absent of voltage regulation, as well as poor power factor collection on long HV D/L. Therefore, phase advancing capacitors (Shunt Capacitor, SCs) are installed in parallel with customer loads for voltage improvement and power factor correction. However, these SCs, sometimes, lead to Ferranti effect, especially at the very lightly loaded condition. Moreover, in recent years, the introduction of photovoltaic power generation systems (PV systems) into HV D/L has developed rapidly and may cause the unacceptable voltage variation on HV D/L.
In this study, a virtual 6.6 kV long distance (20 km) HV D/L without PV system supported from Kyushu Electric Power Company (Qden) in Miyazaki branch, is introduced. In this long distance HV D/L, a 20 MVA transformer, three static voltage regulators (SVRs), and 50 customer loads are included. For very lightly loaded condition, the effects of SCs detachment area on the voltage profiles of HV D/L are numerically investigated and discussed. Moreover, the optimal location is proposed to change the suitable SVR for the purpose of upgrading voltage drop in heavy loaded condition.
Then, voltage profiles of different lengths (20.3 km for long and 8.70 km for short) HV D/Ls with PV system installing SCs at customer’s side and different load capacity are discussed. Furthermore, the conditions of flowing line current on HV D/L with PV system for different load locations are explained with phasor diagram. A program based on the Newton Raphson method was coded for the power flow calculation.

Sterilization of Stem-end Rot of Mango using Dielectric Barrier Discharge and Investigation of Sterilization Factors Reviewed

Dynamic I-V Characteristics of Schottky Diodes and PN Junction Diodes When Lightning Impulse Voltage Is Applied on Them

May Oo KHIN, Ryo TORIHARA , Tatsuya SAKODA, Noriyuki HAYASHI

Memoirs of faculty of engineering university of miyazaki 50 105 - 112 2021.9

Language：English Publishing type：Research paper (bulletin of university, research institution)

Voltage Profiles on HV Distribution Lines with Various Network Configurations and Customers

May Thin KHAING, Tatsuya SAKODA, Noriyuki HAYASHI

Memoirs of faculty of engineering university of miyazaki 50 95 - 104 2021.9

Language：English Publishing type：Research paper (bulletin of university, research institution)

Nakakoga Yuta, Tada Yoichiro, Sakoda Tatsuya, Tazawa Kazutoshi, Ichikawa Hiroyuki

IEEJ Transactions on Fundamentals and Materials 141 ( 6 ) 385 - 390 2021.6

Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

To develop a sterilization method for controlling post-harvest stem-end rot of mango, we examined to sterilize fungi on peduncle by using the dielectric barrier discharge (DBD). Additionally, to investigate the sterilization factors, we performed sterilization against stem-end rot on agar medium by using the DBD generated in air, argon gas or oxygen gas. It was found that the DBD can sterilize fungi with high probability. Ultra-violet ray and O3 don’t contribute to the sterilization. High energy electrons, and radicals such as O and OH play an essential role for the sterilization.

DOI： 10.1541/ieejfms.141.385

Visualization and Diagnosis Method of Defective Photovoltaic String Based on the Temporal Variation Characteristics of String Currents in Generation Mode Reviewed

TORIHARA Ryo, KODAMA Takafumi, TAKENOUCHI Osamu, SAKODA Tatsuya, HAYASHI Noriyuki

Journal of Japan Solar Energy Society 47 ( 3 ) 27 - 36 2021.5

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Solar Energy Society

DOI： 10.24632/jses.47.3_27

Influence of defective bypass diodes on electrical and thermal properties of photovoltaic string and array

Torihara R., Latt N.Z., Khin M.O., Lwin Y.M., Sakoda T., Hayashi N.

IEEE Region 10 Annual International Conference, Proceedings/TENCON 2020-November 1007 - 1012 2020.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEE Region 10 Annual International Conference, Proceedings/TENCON

The intent of this paper is to analyze the power consumption or heat dissipation of defective bypass diode (BPD) at open circuit (OC) and maximum power point (MPP) load conditions when the BPD turns to have resistive behavior in a photovoltaic (PV) string and array. We also analyze the thermal impact of defective BPD in a PV string under different irradiances and cell temperatures. It was observed that the power consumption of defective BPD largely depends on load condition and the thermal impact is more severe in OC condition. It was also observed that the thermal impact of defective BPD is larger under either high irradiance level for the same cell temperature or lower cell temperature on the same irradiance. This study indicates that it is necessary to monitor the heat dissipation of BPDs and to evaluate the electrical properties of the BPDs to realize the reliable PV systems.

DOI： 10.1109/TENCON50793.2020.9293827

On-line PD System and PD Locator for XLPE Cables

Sakoda T., Yamasaki Y., Nakanose S., Hayashi N., Miyake T., Miyagawa K., Kawano W.

Proceeding - 8th International Conference on Condition Monitoring and Diagnosis, CMD 2020 222 - 225 2020.10

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Proceeding - 8th International Conference on Condition Monitoring and Diagnosis, CMD 2020

We constructed an on-line partial discharge (PD) monitoring system (PDOM) with a CT sensor, an analogue-digital converter, and a tablet PC. A sampling frequency for data acquisition is 100 MHz, and we exchange on-site PD data through a cloud system. We successfully measured PDs in the early stage of insulation deterioration of a cross-linked polyethylene (XLPE) cable in a field site. Additionally, following PD detection by using a PDOM, we can locate a PD position by using a PD locator (PDL) system. By locating a PD, we can estimate the actual PD magnitude considering attenuation factor of a high frequency pulse. We show how the PDL system works on a XLPE cable network with time synchronization between two positions by using an injection current pulse. The locating accuracy of the PDL system is evaluated.

DOI： 10.1109/CMD48350.2020.9287182

On-line PD system and PD Locator for XLPE Cables Reviewed

Tatsuya Sakoda, Noriyuki Hayashi, Yuhei Yamasaki, Soichiro Nakanose, Takuma Miyake, Wataru Kawano, Koji Miyagawa

8th International Conference on Condition Monitoring and Diagnosis 1 - 4 2020.10

Language：English Publishing type：Research paper (international conference proceedings)

Affecting Factors to V-t Characteristics of Impulse Discharge Reviewed

Oda Hiroshi, Hazama Issei, Sakoda Tatsuya, Kubo Katsutaka, Mizutani Manabu, Kasuga Yasunori, Fukano Takato

Memoirs of Faculty of Engineering, University of Miyazaki 49 111 - 114 2020.9

Language：Japanese Publishing type：Research paper (scientific journal)

Study on degradation diagnostic method for silicone rubber

Sakoda T., Minami E., Miyake T., Hayashi N., Goto S., Aka Y., Anjiki T., Kasuga Y., Fukano T.

Journal of Electrostatics 107 2020.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Electrostatics

To evaluate the degradation degree of silicone rubber (SiR) of electric power apparatus arranged for a long period of time in the coastal area, we repeatedly performed a salt fog aging test against SiR specimens. Then, the surface hydrophobicity and the leakage current were evaluated. The results showed that a required time for recovering hydrophobicity and a discharge ignition time until the leakage current is detectable are good indexes for degradation diagnosis. Especially, the required time for recovering hydrophobicity is useful.

DOI： 10.1016/j.elstat.2020.103479

Study on Location Accuracy of Partial Discharge Locator for Electric Power Cable Reviewed

Yamashita Katsuya, Sakoda Tatsuya

Memoirs of Faculty of Engineering, University of Miyazaki 49 91 - 94 2020.9

Language：Japanese Publishing type：Research paper (scientific journal)

Sterilization of Stem-end Rot of Mango using Dielectric Barrier Discharge Source and Influence of Operating Gas on sterilization Reviewed

Kinoshita Shunsuke, Tada Yoichiro, Sakoda Tatsuya, Tazawa Kazutoshi, Ichikawa Hiroaki, Ichikawa Hiroyuki

Memoirs of Faculty of Engineering, University of Miyazaki 49 115 - 118 2020.9

Language：Japanese Publishing type：Research paper (scientific journal)

Partial Discharge Characteristics of XLPE Cable with Water Tree Reviewed

Yamashita Katsuya, Sakoda Tatsuya, Yamasaki Yuhei

Memoirs of Faculty of Engineering, University of Miyazaki 49 101 - 104 2020.9

Language：Japanese Publishing type：Research paper (scientific journal)

Characteristics of Partial Discharge in Epoxy Resin with a Void Reviewed

Oda Hiroshi, Sakoda Tatsuya, Aishima Takeru, Nishimura Takeshi

Memoirs of Faculty of Engineering, University of Miyazaki 49 105 - 109 2020.9

Language：Japanese Publishing type：Research paper (scientific journal)

Study on Propagation Characteristics of High Frequency Pulse Current in Electric Power Cable Reviewed

Yamashita Katsuya, Sakoda Tatsuya

Memoirs of Faculty of Engineering, University of Miyazaki 49 95 - 99 2020.9

Language：Japanese Publishing type：Research paper (scientific journal)

Multivariate Analysis Using R for Various Climatic Effects on the Output Performances of CIGS and Multi-Crystalline Si Photovoltaic Systems Installed in Miyazaki, Japan

太田靖之, 迫田達也

宮崎大学工学部紀要 49 119 - 127 2020.9

Language：English Publishing type：Research paper (bulletin of university, research institution) Publisher：宮崎大学工学部

Generally, the performance of a PV system depends not only on its basic technical characteristics but also on the environmental conditions in which they will be set up. Therefore, studying the effects of climatic parameters such as solar irradiance on the plane of array (GPOA), ambient temperature (Ta), relative humidity (RH) and wind speed (νa) on the performance of PV is vital to be able to utilize efficiently solar energy.
The authors have studied the effects of various climatic parameters on the output performances of the two PV systems, 60 kW Copper Indium Gallium Selenide (CIGS) and 50 kW Multi-Crystalline Silicon (MC-Si), which were installed within the campus of University of Miyazaki, Japan. The main objectives of the research are to improve the prediction of the PV systems performance while knowing the climatic parameters of a particular area in which they stand, and also provide a useful dataset for the comparative studies.
The analyses were done by the multiple linear regression analysis (MLR) using the statistical software R. The performances of the two PV systems are in positive proportion to the GPOA and νa, however, as per the values of the slopes of the regression equations, the MC-Si PV system is smaller than the CIGS PV system, attributed to their different module tilt angles and elevations of the PV sites. The performances are in negative proportion to the Ta, but the more sensitivity can be observed in the MC-Si PV system. The RH negatively affected on the MC-Si PV system, although its positive effects can be observed in the CIGS PV system.

Study on Location Accuracy of Partial Discharge Locator for Electric Power Cable

Katsuya YAMASHITA, Tatsuya SAKODA

Memoirs of Faculty of Engineering University of Miyazaki 91 - 94 2020.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Study on Propagation Characteristics of High Frequency Pulse Current in Electric Power Cable

Katsuya YAMASHITA, Tatsuya SAKODA

Memoirs of Faculty of Engineering University of Miyazaki 95 - 100 2020.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Partial Discharge Characteristics of XLPE Cable with Water Tree

Yuhei YAMASAKI, Katsuya YAMASHITA, Tatsuya SAKODA

Memoirs of Faculty of Engineering University of Miyazaki 101 - 104 2020.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Characteristics of Partial Discharge in Epoxy Resin with a Void

Hiroshi ODA, Tatsuya SAKODA, Takeru AISHIMA, Takeshi NISHIMURA

Memoirs of Faculty of Engineering University of Miyazaki 105 - 110 2020.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Affecting Factors to V-t Characteristics of Impulse Discharge

Hiroshi ODA, Issei HAZAMA, Tatsuya SAKODA, Katsutaka KUBO, Manabu MIZUTANI, Yasunori KASUGA, Takato FUKANO

Memoirs of Faculty of Engineering University of Miyazaki 111 - 114 2020.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Sterilization of Stem-end Rot of Mango using Dielectric Barrier Discharge Source and 　Influence of Operating Gas on sterilization

Shunsuke KINOSHITA, Yoichiro TADA, Tatsuya SAKODA, Kazutoshi TAZAWA, Hiroyuki ICHIKAWA

Memoirs of Faculty of Engineering University of Miyazaki 115 - 118 2020.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Multivariate Analysis Using R for Various Climatic Effects on the Output Performances of CIGS and Multi-Crystalline Si Photovoltaic Systems Installed in Miyazaki, Japan

Kyaw Myo WIN, Yasuyuki OTA, Kensuke NISHIOKA, Tatsuya SAKODA, Noriyuki HAYASHI

Memoirs of Faculty of Engineering University of Miyazaki 119 - 128 2020.7

Language：English Publishing type：Research paper (bulletin of university, research institution)

Study on degradation diagnostic method for silicone rubber Reviewed

Tatsuya Sakoda, Eisuke Minami, Takuma Miyake, Noriyuki Hayashi, Shigehiko Goto, Yoshiaki Aka, Tomikazu Anjiki, Yasunori Kasuga, Takato Fukano

Journal of Electrostatics 107 103479-1 - 103479-6 2020.6

Language：English Publishing type：Research paper (scientific journal)

ケーブルにおける部分放電の位置標定技術 Reviewed

山下勝也，三宅琢磨，迫田達也，川野渉, 宮川浩二

電気設備学会論文誌 40 ( 4 ) 14 - 19 2020.4

Language：Japanese Publishing type：Research paper (scientific journal)

架橋ポリエチレンケーブルの防蟻層の遮水効果 Reviewed

黒岩拓真, 迫田達也, 有元慎太郎, 生田昌輝

電気設備学会論文誌 40 ( 3 ) 12 - 13 2020.3

Language：Japanese Publishing type：Research paper (scientific journal)

分岐線路における部分放電電流パルスの伝搬特性 Reviewed

山下勝也, 三宅琢磨, 迫田　達也, 川野渉

電気学会論文誌A 140 ( 2 ) 92 - 97 2020.2

Language：Japanese Publishing type：Research paper (scientific journal)

Study on Water Barrier Effect of Termite preventive Layer of XLPE Cable

Kuroiwa Takuma, Sakoda Tatsuya, Arimoto Shintaro, Ikuta Masateru

The Transactions of the Institute of Electrical Installation Engineers of Japan 40 ( 3 ) 12 - 13 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Installation Engineers of Japan

DOI： 10.14936/tieiej.40.3_12

Propagation Characteristics of Partial Discharge Current Pulse for Branched Line

Yamashita Katsuya, Miyake Takuma, Sakoda Tatsuya, Kawano Wataru

IEEJ Transactions on Fundamentals and Materials 140 ( 2 ) 92 - 97 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

At joint and terminal sections of electric power cables, there is possibility to occur partial discharges (PDs) in defects of insulating materials. Therefore, PD measurement is useful from a viewpoint of assessing insulation deterioration of electric power cables. There are some measurement systems to locate PDs, however, it is quite difficult and complicated in the case where cable lines include branched lines because the PD current pulse separately flows at the branch line. To establish a PD location system, the investigation of propagation characteristics of PD current pulse for branched lines is necessary. Based on EMTP simulations and experiments, we evaluated how a PD current pulse propagates at a Y-branch. The results showed that the separation of a PD current pulse is dependent on frequency component of the PD current pulse and the cable impedance after branching. The frequency components of a PD current pulse, which are higher than the resonant frequency of lines, tend to flow into the longer cable side.

DOI： 10.1541/ieejfms.140.92

Development of Partial Discharge Locator for XLPE Cables using GPS

Yamashita Katsuya, Miyake Takuma, Sakoda Tatsuya, Kawano Wataru, Miyagawa Koji

The Transactions of the Institute of Electrical Installation Engineers of Japan 40 ( 4 ) 14 - 19 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Installation Engineers of Japan

DOI： 10.14936/tieiej.40.4_14

Discharge behavior and dielectric performance of artificially polluted hydrophobic silicone rubber Reviewed

部分放電電流の分岐伝搬特性に関する基礎的検討

山下勝也, 山﨑悠平, 三宅琢磨, 迫田達也, 川野渉

放電・プラズマ・パルスパワー研究会・放電・プラズマ・パルスパワー 2019.10

Language：Japanese Publishing type：Research paper (conference, symposium, etc.)

マンゴー軸腐病の防除手法の検討

多田陽一朗,木之下俊輔,迫田達也,田澤和俊,市川博章

放電・プラズマ・パルスパワー研究会・放電・プラズマ・パルスパワー 2019.10

Language：Japanese Publishing type：Research paper (conference, symposium, etc.)

Electrical characteristics of artificially polluted silicone rubber Reviewed

TAKEZAKI Kento, MIYAKE Takuma, SAKODA Tatsuya, GOTO Shigehiko, AKA Yoshiaki, and ANJIKI Tomikazu

The International Council on Electrical Engineering (ICEE) Conference 2019.7

Language：English Publishing type：Research paper (international conference proceedings)

Propagation Characteristics of Partial Discharge Pulse Current on Branched Line

Katsuya YAMASHITA, Takuma MIYAKE, Tatsuya SAKODA, Wataru KAWANO

MEMOIRS OF FACULTY OF ENGINEERING UNIVERSITY OF MIYAZAKI 99 - 102 2019.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Sterilization of Bacillus Subtilis and measurement of O3 concentration in sterilization device using dielectric barrier discharge

Junichiro TSUCHIDA, Shunsuke KINOSHITA, Tatsuya SAKODA

MEMOIRS OF FACULTY OF ENGINEERING UNIVERSITY OF MIYAZAKI 95 - 98 2019.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Sterilization of Stem-end rot of Mango using a dielectric barrier discharge source

Shunsuke KINOSHITA, Junichiro TSUCHIDA, Tatsuya SAKODA, Kazutoshi TAZAWA, Hiroaki ICHIKAWA

MEMOIRS OF FACULTY OF ENGINEERING UNIVERSITY OF MIYAZAKI 2019.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Study on Location Accuracy of Partial Discharge Locator Reviewed

Katsuya Yamashita, Takuma Miyake, Tatsuya Sakoda, Wataru Kawano

2019 Electrical Insulation Conference 321 - 324 2019.6

Language：English Publishing type：Research paper (international conference proceedings)

Material Temperature Dependence on Behavior of Partial Discharge in Epoxy Resin Reviewed

Tatsuya Sakoda, Mitsuki Kawakone, Noriyuki Hayshi, Makoto Setoguchi, Makoto Setoguchi

2019 Electrical Insulation Conference 205 - 208 2019.6

Language：English Publishing type：Research paper (international conference proceedings)

誘電体バリア放電を用いたマンゴー軸腐病の発病抑制効果 Reviewed

土田潤一郎, 迫田達也, 田澤和俊, 市川博章, 溝口則和, 櫛間義幸

電気学会論文誌Ａ 139 ( 5 ) 279 - 280 2019.5

Language：Japanese Publishing type：Research paper (scientific journal)

Characteristics of underwater plasma with surfactant Reviewed

Hiroki Goto and Tatsuya Sakoda

Electrical Engineering Japan 1 - 7 2018.10

Language：English Publishing type：Research paper (scientific journal)

Long-Term Observation of Ambient Temperature Effects on the Performance of A 60 kW CIGS Solar Power System Installed in Miyazaki Reviewed

Kyaw Myo Win, Ryo Torihara, Shohei Kita, Tetsuya Sakoda, Yasuyuki Ota, Kensuke Nishioka, and Noriyuki Hayashi

Proceedings of TENCON 2018 - 2018 IEEE Region 10 Conference 2018.10

Language：English Publishing type：Research paper (scientific journal)

Examination of Compact and Online Diagnosis Method Based on Temporal Fluctuation of String Currents of Photovoltaic Solar Plant Reviewed

Ryo Torihara, Shohei Kita, Osamu Takenouchi, Tetsuya Sakoda, and Noriyuki Hayashi

Proceedings of TENCON 2018 - 2018 IEEE Region 10 Conference 2018.10

Language：English Publishing type：Research paper (international conference proceedings)

配電用ギャップ付酸化亜鉛形避雷器の放電遅れ現象に関する研究 Reviewed

迫田達也, 堀江響, 武居周, 久保克隆, 水谷学, 深野孝人

電気学会論文誌A 138 ( ９ ) 457 - 462 2018.9

Language：Japanese Publishing type：Research paper (scientific journal)

界面活性剤添加時の水中プラズマ源の特性 Reviewed

後藤弘輝, 迫田達也

電気学会論文誌 A 138 ( 7 ) 355 - 360 2018.7

Language：Japanese Publishing type：Research paper (scientific journal)

CVT ケーブルの劣化位置標定に関する基礎研究

池田佑允, 迫田達也, 佐藤英章, 春山浩, 宮崎和則

宮崎大学工学部紀要 47 143 - 148 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

塩分濃度を変化させた場合のポリマー材料の耐電圧評価

川口翔大, 迫田達也, 阿嘉良昌, 安食富和, 深野孝人

宮崎大学工学部紀要 47 149 - 152 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

界面活性剤添加時における水中プラズマ源の特性の検討

後藤弘輝, 西村豪志, 土田潤一郎, 迫田達也

宮崎大学工学部紀 47 157 - 162 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

変成器内部で生じる部分放電放射電磁波の周波数特性

川小根光輝, 白浜優吾, 中村友哉, 迫田達也

宮崎大学工学部紀要 47 153 - 156 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

配電機器内部で生じた部分放電による放射電磁波特性

白浜優吾, 中村友哉, 川小根光輝, 迫田達也

宮崎大学工学部紀要 47 163 - 166 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

シリコーンゴムの塩害に対する耐汚損特性の検討

田平耕成, 迫田達也, 阿嘉良昌, 安食富和, 深野孝人

宮崎大学工学部紀要 47 167 - 170 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Heガスを利用したプラズマ装置における遷移発光強度の測定と芽胞菌の殺菌

土田潤一郎, 西村豪志, 後藤弘輝, 迫田達也

宮崎大学工学部紀要 47 171 - 174 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

プラグインエルボで発生する沿面放電特性

中村友哉, 川小根光輝, 白浜優吾, 迫田達也

宮崎大学工学部紀要 47 175 - 178 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

塩霧試験におけるポリマー材料の撥水性特性の評価

南英佑, 迫田達也, 阿嘉良昌, 安食富和, 深野孝人

宮崎大学工学部紀要 47 183 - 186 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

配電用直列ギャップ付酸化亜鉛形避雷器のV -t 特性の改善に関する研究

堀江響, 迫田達也, 久保克隆, 水谷学, 深野孝人

宮崎大学工学部紀要 47 187 - 192 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

誘電体バリア放電を利用した殺菌装置における芽胞菌の殺菌

西村豪志, 土田潤一郎, 迫田達也

宮崎大学工学部紀要 47 179 - 182 2018.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Control of Voltage Rise Caused by the Reversed Power Flow in High Voltage Distribution System by Detaching Shunt Capacitors and Optimum Location of PV Power Plan Reviewed

Thin Thin Hlaing, Tatsuya Sakoda, and Noriyuki Hayashi

24th International Conference on Electrical Engineering 178 - 184 2018.6

Language：English Publishing type：Research paper (international conference proceedings)

Comarative Analysis of Optimization Based Tuning Method and Conventional Tuning Method for LFC of Multi-Area Power System Reviewed

Aung Ko Latt, Tatsuya Sakoda, and Noriyuki Hayashi

24th International Conference on Electrical Engineering 228 - 234 2018.6

Language：English Publishing type：Research paper (international conference proceedings)

Development of on-line partial discharge locator for electric power cable Reviewed

Katsuya Yamashita, Souta Watanuki, Takuma Miyake, Tatsuya Sakoda, Wataru Kawano

2018 Electrical Insulation Conference (EIC) 216 - 219 2018.6

Language：English Publishing type：Research paper (international conference proceedings)

Variation in Insulation Performance of Artificially Polluted Silicone Rubber Reviewed

Kento Takezaki, Takuma Miyake, Tatsuya Sakoda, Yoshiaki Aka, Tomikazu Anjiki, Takato Fukano

24th International Conference on Electrical Engineering 1679 - 1684 2018.6

Language：English Publishing type：Research paper (international conference proceedings)

Sakoda T., Tabira K., Miyake T., Hayashi N., Haji K., Aka Y., Anjiki T., Fukano T.

Journal of Electrostatics 93 97 - 103 2018.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Electrostatics

© 2018 Flashover voltage and discharges behavior were investigated with silicone rubber (SiR) polluted with fog, red clay or carbon particles. For a SiR polluted with carbon, partial discharges occur between water droplets and form interspersed dry bands. For a SiR polluted with red clay, the leakage current induces uniform dry bands and dry-band arc discharges. Because flashover occurs through the dry bands, the noticeable difference in flashover voltage between the polluting materials is not seen. The pollution deposit changes the surface state and causes partial discharges which lead large leakage current, however, the partial discharges don't significantly lower insulation performance.

DOI： 10.1016/j.elstat.2018.04.006

Recovery Characteristics of Hydrophobicity and Electrical Property of Polymeric Material Reviewed

Minami Eisuke, Miyake Takuma, Sakoda Tatsuya, Aka Yoshiaki, Anjiki Tomikazu, Fukano Takato

IEEJ Transactions on Fundamentals and Materials 138 ( 3 ) 115 - 116 2018.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

To evaluate the long-term reliability of polymeric material used for electric power apparatus in the coastal area and to establish its insulation diagnosis technique, we evaluated recovery characteristics of hydrophobicity and electrical property of silicone rubber (SiR) by performing a salt fog aging test. As the result, the required times for recovery between the hydrophobicity and the electrical property are different. The time when the leakage current begins to be detectable might be a good index of the deterioration diagnosis.

DOI： 10.1541/ieejfms.138.115

Numerical analysis of I-V characteristics and diode currents of a PV module reflected by partial shadow

Numerical analysis of electrical characteristics of a PV module irradiated by an impulse light flash Reviewed

Cheikh Ibra Wade, Ryo Torihara, Tatsuya Sakoda and Noriyuki Hayashi

Journal of InternatIonal Council on Electrical Engineering, Vol. 8, No. 1, pp. 8-13 (2018.2) 1 ( 8 ) 8 - 13 2018.2

Language：English Publishing type：Research paper (scientific journal)

熱電発電システムにおいて各モジュール間の内部抵抗の違いを考慮した最大出力点追尾の制御手法 Reviewed

奥将俊, 田島大輔, 迫田達也, 林則行, 穂高一条

太陽エネルギー 1 ( 44 ) 79 - 87 2018.1

Language：Japanese Publishing type：Research paper (scientific journal)

Improvement of Discharge Ignition Characteristics of a Surge Arrester with a Spark Gap Reviewed

Hibiki Horie, Tatsuya Sakoda, Katsutaka Kubo, Manabu Mizutani, Takato Fukano

IEEJ Transactions on Fundamentals and Materials 11 ( 137 ) 724 - 729 2017.11

Language：English Publishing type：Research paper (scientific journal)

デシカント空調システムにおける外気の絶対湿度とシステム運転方式との関係

石川敏嗣，藤澤一平，迫田達也，林則之

宮崎大学工学部紀要 46 179 - 184 2017.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

マンゴーに発生する病害の防除を目指したプラズマミスと装置における芽胞菌及び大腸菌の殺菌

西村豪志, 堂園大雅, 後藤弘輝, 富永大, 迫田達也

宮崎大学工学部紀要 46 175 - 178 2017.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

真空遮断器を対象とした部分放電検知の劣化診断技術の開発

朝倉匡俊, 岸本恵修, 三宅琢磨, 迫田達也, 壱岐祐典, 前田健作

宮崎大学工学部紀要 46 133 - 138 2017.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

絶縁体内部で発生する部分放電の劣化特性

平島俊紀，中村友哉，白浜優吾，迫田達也

宮崎大学工学部紀要 46 139 - 142 2017.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

電磁波センサを用いた配電機器内部で生じる部分放電の検出

白浜優吾，平島俊紀，中村友哉，迫田達也

宮崎大学工学部紀要 46 139 - 142 2017.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

交流課電によるポリマー材料の耐電圧特性評価

出口竜也, 迫田達也, 阿嘉義昌, 安食富和, 深野孝人

宮崎大学工学部紀要 46 159 - 163 2017.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

直列ギャップ付ZnO避雷器のV-t特性の改善に関する研究

堀江響, 迫田達也, 久保克隆, 水谷学, 深野孝人

宮崎大学工学部紀要 46 155 - 158 2017.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Numerical Analysis of Electrical Characteristics of a PV Module Irradiated by an Impulse Light Flash Reviewed

CHEIKH IBRA WADE, RYO TORIHARA, TATSUYA SAKODA, NORIYUKI HAYASHI

The International Conference on Electrical Engineering 1 - 4 2017.6

Language：English Publishing type：Research paper (international conference proceedings)

Study on Grasping Partial Discharge Development Using an Acoustic Emission Technique Reviewed

Tatsuya Sakoda, Toshiki Hirashima, Tomoya Nakamura, Yugo Shirahama, Noriyuki Hayashi

The Journal of CPRI 16 ( 3 ) 1 - 6 2017.3

Language：English Publishing type：Research paper (scientific journal)

Wade C., Torihara R., Fukamachi Y., Sakoda T., Hayashi N.

IEEE Region 10 Annual International Conference, Proceedings/TENCON 2642 - 2645 2017.2

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEE Region 10 Annual International Conference, Proceedings/TENCON

© 2016 IEEE. The authors have studied the diagnosis method of PV systems. In this paper, influences of partial shadow reflected partly on PV panels on the electrical characteristics of solar cells are numerically investigated by using the LT Spice simulation. Not only the change in I-V characteristics, but also the change in current and voltage distribution for every cell component are demonstrated and discussed based on the numerical results. It is clearly illustrated that the cell with the lowest transmission of sunlight among the cells concerned dominates the whole characteristics of the PV module. Numerical results obtained from the current simulation will provide basic knowledge when estimating the total I-V characteristics of a whole PV system which composed of multiple PV subsystems having different I-V characteristics with each other.

DOI： 10.1109/TENCON.2016.7848517

Improvement of discharge ignition characteristics of a surge arrester with a spark gap

Horie H., Sakoda T., Kubo K., Mizutani M., Fukano T.

IEEJ Transactions on Power and Energy 137 ( 11 ) 724 - 729 2017

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Power and Energy

© 2017 The Institute of Electrical Engineers of Japan. Surge arrester with a spark gap has been installed for reducing electrical failures in Japanese distribution system. The top and the bottom of a ceramic spacer for sustaining an electrode gap in a surge arrester contact with electrodes, of which the electric field becomes high. Therefore, high electric field region such as the triple junction point becomes a source to supply electrons to a spark-gap. In this study, we made some electrodes with a small step edge on an inclined plane of an electrode. The electric field around the small step edge became high, and we aimed that the small step edge functioned as if it were a triple junction points for a conventional spark gap. Based on measurements of V-t characteristic and the number of electrons per unit time, we investigated that the artificially formed high electric field region lower impulse spark-over voltage and that a spark-over voltage occurs within a duration of 0.4-1.2 μs when a positive impulse voltage of 25-42 kV with 1.2/50 μs is applied. The results will contribute on a further stabilization of discharge and increasing a degree of freedom for design of a spark gap.

DOI： 10.1541/ieejpes.137.724

Chemical Analysis of Casual Elements for Deterioration of Cylindrical EDLC

Yoshitama H., Tashima D., Sakoda T., Hayashi N., Yuhara M., Utsunomiya T.

Electronics and Communications in Japan 99 ( 12 ) 36 - 43 2016.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electronics and Communications in Japan

© 2016 Wiley Periodicals, Inc. Chemical analysis was carried out before and after the constant voltage hold test that was an acceleration deterioration examination to clarify deterioration factors of electric double-layer capacitor (EDLC). The results showed that the stress test slightly caused the increase of internal resistance. It was also confirmed that the range of fluorochemicals was formed on the electrode surface for approximately 10 nm in depth using electron spectroscopy for chemical analysis (ESCA). From the chemical analysis of the electrolyte using an inductively coupling plasma emission analyzer (ICP-OES), it was confirmed that the electrolyte included silicon which is one of the ingredient elements of an electrode and that the increase in holding voltage in the stress test decreased the silicon density in the electrolyte.

DOI： 10.1002/ecj.11911

Plasma Sterilization of Anthrax Pathogen in Water Mist

Chemical Analysis of Casual Elements for Deterioration of Cylindrical EDLC Reviewed

Hiroumu Yoshitama, Daisuke Tashima, Tatsuya Sakoda, Noriyuki Hayashi, Masamitsu Yuhara, Takashi Utsunomiya

Electronics and Communications in Japan 135 ( 12 ) 792 - 798 2016.12

Language：English Publishing type：Research paper (scientific journal)

マンゴー炭疽病菌の分生胞子の殺菌に必要なオゾン濃度および処理時間に関する研究 Reviewed

富永大, 田中聡之, 迫田達也, 溝口則和, 櫛間義幸

電気学会論文誌 A 136 ( 11 ) 726 - 727 2016.11

Language：Japanese Publishing type：Research paper (scientific journal)

Detection of Partial Discharges in Electric Power Equipment using an Electromagnetic Wave Sensor Reviewed

Yugo Shirahama, Toshiki Hirashima, Mitsuki Kawakone, Takuma Miyake, Tatsuya Sakoda

Joint Conference of IWHV2016 & JK2016 on ED&HVE 51 - 54 2016.11

Language：English Publishing type：Research paper (international conference proceedings)

Study on improvement of discharge characteristics of a surge arrester with a spark gap Reviewed

Hibiki Horie, Takuma Miyake, Tatsuya Sakoda, Tatsuya Tokunaga, Katsutaka Kubo, Manabu Mizutani, Takato Fukano

Joint Conference of IWHV2016 & JK2016 on ED&HVE 81 - 85 2016.11

Language：English Publishing type：Research paper (international conference proceedings)

Numerical Analysis of I-V Characteristics and Siode Currents of a PV Module Reflected by Partial Shadow Reviewed

C. I. Wade, R. Torihara, Y. Fukamachi, T. Sakoda, N. Hayashi

2016 IEEE Region 10 Conference (TENCON) 2644 - 2647 2016.11

Language：English Publishing type：Research paper (international conference proceedings)

STERILIZATION OF COLLETOTRICHUM SP. USING A DISCHARGE SOURCE Reviewed

Takeshi Nishimura, Masaru Tominaga, Junichiro Tsuchida, Tatsuya Sakoda, Norikazu Mizoguchi, Yoshiyuki Kushima

The First International Conference on Hybridized Agriculture 40 - 46 2016.10

Language：English Publishing type：Research paper (international conference proceedings)

AE及び電磁波センサを用いた部分放電検出”,宮崎大学工学部紀要

朝倉匡俊, 井平学, 三宅琢磨, 迫田達也, 壱岐祐典, 前田健作

宮崎大学工学部紀要 45 181 - 185 2016.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

絶縁ゴムのトラッキング劣化過程におけるAE信号特性

平島俊紀，白浜優吾，中村友哉，三宅琢磨，迫田達也，緒方貴仁，鎌田文麿，副島通邦

宮崎大学工学部紀要 45 ( 199 ) 204 2016.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

マンゴーに発生する病害にプラズマ処理が与える影響

堂園大雅, 富永大, 迫田達也, 溝口則和, 櫛間義幸

宮崎大学工学部紀要 45 193 - 198 2016.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

ポリマー材料の傾斜角度がポリマー表面の放電特性に与える影響

出口竜也, 枦健一, 三宅琢磨, 迫田達也, 阿嘉良昌, 安食富和, 深野孝人

出宮崎大学工学部紀要 45 187 - 192 2016.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

熱電発電システムにおける開放電圧を用いた最大出力点の探索法 Reviewed

奥将俊，石津智子，田島大輔，迫田達也，林則行，穂高一条

太陽エネルギー 42 ( 4 ) 49 - 55 2016.4

Language：Japanese Publishing type：Research paper (scientific journal)

電力ケーブル接続部に有効な周波数加速劣化試験の基礎的検討 Reviewed

井平学, 平島俊紀, 三宅琢磨, 迫田達也, 中野亮介, 鎌田文麿, 西昌美

電気学会論文誌A 136 ( 3 ) 241 - 242 2016.3

Language：Japanese Publishing type：Research paper (scientific journal)

Tominaga M., Tanaka T., Sakoda T., Mizoguchi N., Kushima Y.

Proceedings - 2015 IIAI 4th International Congress on Advanced Applied Informatics, IIAI-AAI 2015 690 - 694 2016.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Proceedings - 2015 IIAI 4th International Congress on Advanced Applied Informatics, IIAI-AAI 2015

© 2015 IEEE. Miyazaki prefecture in Japan promotes agricultural food industry in recent year. One of the activities is promotion of agricultural and livestock products. However, Miyazaki prefecture is very far from large-scale consumption areas such as Tokyo and Osaka. To keep freshness of agricultural and livestock products during their transport is a serious problem from a viewing of putrefaction due to blight outbreak. Apple Mango has been a very famous and representative product in Miyazaki prefecture and it has successfully continued to make a good profit. However, fruit rot disease such as Anthrax Pathogen after harvest is serious [1] [2] [3]. Therefore, a sterilization technique is strongly required. We here generated the dielectric barrier discharge plasma in water mist, which may possible to sterilize the whole of greengrocery because of its high diffusibility. We examined fungicidal activity against Colletotrichum sp.

DOI： 10.1109/IIAI-AAI.2015.244

Examination of B. Subtilis Spore Sterilization by an Underwater-Ar-Plasma

Hamada Toshiyuki, Mine Taiki, Sakoda Tatsuya

IEEJ Transactions on Fundamentals and Materials 136 ( 1 ) 64 - 65 2016.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Advanced oxidation process (AOP) with hydroxyl radicals (OH) is considered to be useful for sterilization; therefore, we have proposed an underwater plasma source with a porous glass membrane which functioned in bubble supply and the formation of micro-discharges. In this study, we first examined whether B. subtilis spores could be sterilized by the underwater plasma of which operating gas was argon. Next, similar experiment was conducted by using mannitol, and the numbers of colonies were compared. The obtained results showed that OH radicals generated at gas-liquid interface were responsible for the sterilization.

DOI： 10.1541/ieejfms.136.64

Basic Study on Frequency Accelerated Aging Test for Joint Section of XLPE Cable

多孔質膜利用の水中アルゴンプラズマによる芽胞菌殺菌機構の考察 Reviewed

濱田俊之, 峰大樹, 迫田　達也

電気学会論文誌A 136 ( 1 ) 64 - 65 2016.1

Language：Japanese Publishing type：Research paper (scientific journal)

Ihira Manabu, Hirashima Toshiki, Miyake Takuma, Sakoda Tatsuya, Nakano Ryosuke, Kamata Fumimaro, Nishi Masami

The transactions of the Institute of Electrical Engineers of Japan.A 136 ( 3 ) 155 - 156 2016

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

We studied usefulness of a frequency accelerated aging test by paying attention to the number of partial discharge (PD) pulses and the accumulated PD charges per a cycle of frequency of applied voltage. The results shows that a frequency accelerated aging test is useful when the accumulated PD charges per a cycle of frequency of applied voltage with higher than PD inception voltage are the almost same as that at a commercial frequency of 60 Hz. If applied frequency is 1 kHz, an accelerated aging test with 16.6 times faster than that for 60 Hz can be achieved.

DOI： 10.1541/ieejfms.136.155

Study on Ozone Concentration and Process Time Required for Sterilization of Conidiospore of Colletotrichum sp.

Tominaga Masaru, Tanaka Toshiyuki, Sakoda Tatsuya, Mizoguchi Norikazu, Kushima Yoshiyuki

IEEJ Transactions on Fundamentals and Materials 136 ( 11 ) 726 - 727 2016

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

To investigate optimal concentration of O3 and process time for sterilization of conidiospore of Colletotrichum sp., we examined sterilization by using CT (product of concentration and process time) as a sterilization index. The results showed that the usual CT was not be useful for interpreting sterilization.

DOI： 10.1541/ieejfms.136.726

Characteristics of an underwater plasma source with a porous glass membrane

Shiomitsu E., Sakoda T.

Electronics and Communications in Japan 98 ( 12 ) 72 - 79 2015.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electronics and Communications in Japan

© 2015 Wiley Periodicals, Inc. The advanced oxidation process (AOP) with hydroxyl radicals (OH) is considered to be useful for water purification through oxidation; therefore, we proposed an underwater plasma source with a porous glass membrane which performed the functions of bubble supply and the formation of microdischarges. We observed bubble formation and light emission from discharges on the surface of the membrane using a high-speed camera and a spectroscope, respectively. In addition, the dependence of gas pressure on the generation of OH radical and the decomposition of recalcitrant organic matter were examined. The obtained results showed that AOP may be more effective when the operating gas pressure is set higher than a pressure which could form bubbles.

DOI： 10.1002/ecj.11772

Chemical Analysis of Causal Elements for Deterioration of Cylindrical EDLC

Yoshitama Hiromu, Tashima Daisuke, Sakoda Tatsuya, Hayashi Noriyuki, Yuhara Masamitsu, Utsunomiya Takashi

IEEJ Transactions on Fundamentals and Materials 135 ( 12 ) 792 - 798 2015.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Chemical analysis was carried out before and after the constant voltage hold test that was an acceleration deterioration examination to clarify deterioration factors of electric double-layer capacitor (EDLC). The results showed that the stress test slightly caused the increase of internal resistance. It was also confirmed that the range of fluorochemicals was formed on the electrode surface for approximately 10 nm in depth using electron spectroscopy for chemical analysis (ESCA). From the chemical analysis of the electrolyte using an inductively coupling plasma emission analyzer (ICP-OES), it was confirmed that the electrolyte included silicone which is one of the ingredient elements of an electrode and that the increase in holding voltage in the stress test decreased the silicone density in the electrolyte.

DOI： 10.1541/ieejfms.135.792

Basic characteristics of a heat and electricity combined generation system using biomass fuel

化学分析による電気二重層キャパシタの劣化要因の考察 Reviewed

吉玉拓, 田島大輔, 迫田達也, 林則行, 湯原将光, 宇都宮隆

電気学会論文誌A 135 ( 12 ) 792 - 798 2015.12

Language：Japanese Publishing type：Research paper (scientific journal)

Study on Plasma Sterilization of Plant Anthracnose Pathogen in Water Mist Reviewed

Masaru Tominaga, Toshiyuki Tanaka, Tatsuya Sakoda, Norikazu Mizoguchi, Yoshiyuki Kushima

Information Engineering Express, International Institute of Applied Informatics 1 ( 4 ) 11 - 20 2015.12

Language：English Publishing type：Research paper (scientific journal)

Detection and Development of Partial Discharges for Vacuum Circuit Breaker using Electromagnetic Wave Sensors Reviewed

Masatoshi Asakura, Manabu Ihira, Takuma Miyake, Tatsuya Sakoda, Kensaku Maeda, Yusuke Iki

2015 Korea-Japan Joint Symposium on Electrical Discharge and HV Engineering 31 - 34 2015.11

Language：English Publishing type：Research paper (international conference proceedings)

Characteristics of flashover on polluted polymer surface Reviewed

Tatsuya Sakoda, Daichi Yamashita, Tatsuya Deguchi, Takuma Miyake, Noriyuki Hayashi, Kenich Haji, Yoshimasa Aka, Tomikazu Anjiki, and Takato Fukano

2015 Korea-Japan Joint Symposium on Electrical Discharge and HV Engineering 81 - 84 2015.11

Language：English Publishing type：Research paper (international conference proceedings)

触媒層の違いによる固体高分子形燃料電池用MEA の劣化特性

古澤伸仁, 田島大輔, 迫田達也, 林則行

宮崎大学工学部紀要 41 - 47 2015.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

シリコーン材料の劣化特性の評価

陣内雅人, 山下大地, 岩本丈, 三宅琢磨, 迫田達也

宮崎大学工学部紀要 33 - 40 2015.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

柚子を用いた電気二重層キャパシタ用炭素材料の開発

上栗伸仁, 田島大輔, 迫田達也, 林則行

宮崎大学工学部紀要 9 - 12 2015.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

低周波から中間周波における人体内部インピーダンス測定装置の開発

堀晃太郎, 麦谷翔平, 迫田達也, 林則行, 太良尾浩生

宮崎大学工学部紀要 27 - 31 2015.7

Language：Japanese Publishing type：Research paper (bulletin of university, research institution)

Plasma Sterilization of Anthrax Pathogen in Water Mist Reviewed

Masaru Tominaga , Toshiyuki Tanaka , Tatsuya Sakoda , Norikazu Mizoguchi , Yoshiyuki Kushima

2015 IIAI 4th International Congress on Advanced Applied Informatics 690 - 694 2015.7

Language：English Publishing type：Research paper (international conference proceedings)

Influence of Operation Modes of a Cooling Pump on Thermal and Electrical Properties of Thermoelectric Generator System Reviewed

Toshitsugu Ishikawa, Masatoshi Oku, Daisuke Tashima, Tatsuya Sakoda, Noriyuki Hayashi

The International Conference on Electrical Engineering ( 15A-192-FP ) 1 - 4 2015.7

Language：English Publishing type：Research paper (international conference proceedings)

Evaluation of Tracking Deterioration for a Plug in Elbow by an Acoustic Emission Technique Reviewed

Toshiki, Hirashima, Kenta, Miyabe, Tatsuya, Sakoda, Ryosuke, Nakano, Fumimaro, Kamada Masami, Nishi

The International Conference on Electrical Engineering ( 15A-206-FP ) 1 - 4 2015.7

Language：English Publishing type：Research paper (international conference proceedings)

Detection of Partial Discharges for Vacuum Circuit Breaker in Cubicle using Acoustic Emission and Electromagnetic Wave sensors Reviewed

Masatoshi Asakura, Manabu Ihira, Takuma Miyake, Tatsuya Sakoda, Yusuke Iki, Ryuya Kida

The International Conference on Electrical Engineering ( 15A-122-FP ) 1 - 4 2015.7

Language：English Publishing type：Research paper (international conference proceedings)

Influence of Shed Inclination on Discharge Ignition under DC Voltage Application Reviewed

D. Yamashita, T. Miyake, T. Sakoda, Y. Aka, T. Anjiki, and T. Fukano

2015 Asia-Pacific International Conference on Lightning (APL) 569 - 572 2015.6

Language：English Publishing type：Research paper (international conference proceedings)

Observation of Creeping Flashover on ZnO element Reviewed

T. Sakoda and D. Tashima

2015 Asia-Pacific International Conference on Lightning (APL) 693 - 696 2015.6

Language：English Publishing type：Research paper (international conference proceedings)

Development of polymer housed surge arrester applied to D.C. railway systems Reviewed

Y. Aka, T. Fukano, Y. Kasuga, T. Anjiki and T. Sakoda

2015 Asia-Pacific International Conference on Lightning (APL) 137 - 140 2015.6

Language：English Publishing type：Research paper (international conference proceedings)

Detection of Partial Discharge in Cubicle Reviewed

Manabu Ihira, Masatoshi Asakura, Takuma Miyake, Tatsuya Sakoda, Yusuke Iki, Ryuya Kida

The 17th Asian Conference on Electrical Discharge 31-1 - 31-4 2014.12

Language：English Publishing type：Research paper (international conference proceedings)

Sterilization Characteristics of Underwater Plasma Reviewed

Taiki Mine,Taiga Douzono, Tatuya Sakoda, Norikazu Mizoguchi

The 17th Asian Conference on Electrical Discharge 1-1 - 1-4 2014.12

Language：English Publishing type：Research paper (international conference proceedings)

Basic Characteristics of a Heat and Electricity Combined Generation System Using Biomass Fuel Reviewed

Masatoshi Oku, Noriyuki Hayashi, Tatsuya Sakoda, Daisuke Tashima

3rd The International Conference on Renewable Energy Research and Applications 222 - 227 2014.10

Language：English Publishing type：Research paper (international conference proceedings)

Basic Characteristics of a Heat and Electricity Combined Generation System Using Biomass Fuel Reviewed

Masatoshi Oku, Noriyuki Hayashi, Tatsuya Sakoda, Daisuke Tashima

Proceedings of the 3rd International Conference on Renewable Energy Research and Applications 222 - 228 2014.10

Language：English Publishing type：Research paper (international conference proceedings)

電気二重層キャパシタの劣化要因に関する考察 Reviewed

吉玉拓, 春田篤二, 田島大輔, 迫田達也

電気学会論文誌A 134 ( 10 ) 525 - 531 2014.10

Language：Japanese Publishing type：Research paper (scientific journal)

GAS-LIQUID INTERFACIAL DISCHARGE WITH A POROUS GLASS MEMBRANE Reviewed

T. SAKODA and T. MINE

Proceedings of the XXth International Conference on Gas Discharges and their Applications 562 - 565 2014.7

Language：English Publishing type：Research paper (international conference proceedings)

Compensation of output power characteristics of a partly-malfunctioned thermoelectric generator system by using a diode bypass circuit Reviewed

Masatoshi Oku, Daisuke Tashima, Tatsuya Sakoda, Noriyuki Hayashi

Proceedings of International Conference on Electrical Engineering 2014 384 - 389 2014.6

Language：English Publishing type：Research paper (international conference proceedings)

クロスボンド接続を有するケーブルにおける部分放電位置標定法に関する基礎的検討 Reviewed

北島純一, 迫田達也, 渡部清範

電気学会論文誌A 134 ( 6 ) 428 - 429 2014.6

Language：Japanese Publishing type：Research paper (scientific journal)

多孔質ガラス膜を用いた水中放電プラズマ発生装置の特性 Reviewed

塩満栄一, 迫田達也

電気学会論文誌A 134 ( 5 ) 321 - 326 2014.5

Language：Japanese Publishing type：Research paper (scientific journal)

Oku M., Sakoda T., Hayashi N., Tashima D.

3rd International Conference on Renewable Energy Research and Applications, ICRERA 2014 222 - 228 2014.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：3rd International Conference on Renewable Energy Research and Applications, ICRERA 2014

© 2014 IEEE. In this paper, we propose a unique co-generation system including a biomass boiler-using a thermoelectric generator (TEG). The boiler burned biomass fuel derived from a cow dung. In this system, warm water is generated through heat exchange in the boiler, and electricity is generated through the TEG that uses the high temperature of an exhaust gas from the boiler. In this study, the co-generation system was not well optimized, with the result that both the heat exchange efficiency of the biomass boiler and hence, - the amount of electric power generated were very low. However, the study demonstrated that the co-generation system that using the biomass as a heat source, and a TEG as an electric power generator can provide an effective energy source.

DOI： 10.1109/ICRERA.2014.7016560

Basic Study on Partial Discharge Location for Cross-bonding Cables

Kitajima Junichi, Sakoda Tatsuya, Watanabe Kiyonori

IEEJ Transactions on Fundamentals and Materials 134 ( 6 ) 428 - 429 2014

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

To locate partial discharges (PDs) in cross-bonding cables where current pulses due to PDs might be divided, we paid attention to phases of current pulses obtained by six CT sensors arranged at both sides of 3-phase of the cables. The accuracy of PD location, obtained by using time difference between arrival times of current pulses from specified phase, was relatively high even for cross-bonding cables.

DOI： 10.1541/ieejfms.134.428

Characteristics of an Underwater Plasma Source with a Porous Glass Membrane

Shiomitsu Eiichi, Sakoda Tatsuya

IEEJ Transactions on Fundamentals and Materials 134 ( 5 ) 321 - 326 2014

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Advanced oxidation process (AOP) with hydroxyl radicals (OH) is considered to be useful for water purification through oxidation; therefore, we proposed an underwater plasma source with a porous glass membrane which functioned in bubble supply and the formation of micro-discharges. We observed bubble formation and light emission from discharge on the surface of the membrane using a high-speed camera and a spectroscope, respectively. Additionally, dependence of gas pressure on generation of OH radical and decomposition of recalcitrant organic matter were examined. The obtained results showed that AOP might be more effective when the operating gas pressure was set higher than a pressure which could form bubbles.

DOI： 10.1541/ieejfms.134.321

Study on Deterioration Factors of an Electric Double-layer Capacitor

Yoshitama Hiromu, Haruta Atsuji, Tashima Daisuke, Sakoda Tatsuya, Hayashi Noriyuki

IEEJ Transactions on Fundamentals and Materials 134 ( 10 ) 525 - 531 2014

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Electric double-layer capacitors (EDLCs) have the advantages of much longer life and unnecessary maintenance. However, for EDLCs used for a long period, a decrease of electrostatic capacity and an increase in internal resistance are recognized. In this study, in order to clarify the factors responsible for the deterioration of EDLCs used for a long period, chemical analysis was conducted on each component such as an activated carbon electrode and an electrolytes solution. The obtained data were compared with those from a new EDLC. The results showed that long-term use reduced electrostatic capacity about 5% and made internal resistance increase by about 1.7 times. The quantity of oxygen due to surface functional groups of the activated carbon electrode was confirmed using electron spectroscopy for chemical analysis (ESCA). As compared with results obtained from a new EDLC, long-term use made the ratio of O-C=O deriving from carboxyl group (-COOH) to C-C increase 1.2 times. The ratio of C-O deriving from hydroxyl group (-OH) to C-C also increased 1.4 times. In addition, it was found that BET surface area decreased about 40% and that pores whose diameter was in the range between 0.8 to 20 nm disappeared.

DOI： 10.1541/ieejfms.134.525

Influence on Bleaching Characteristics by Different Discharge Form for a Passing Water-type Ozonizer

Shiomitsu Eiichi, Ariyoshi Junya, Fuji Shinsuke, Sakoda Tatsuya, Kijima Junji, Nakashima Hideyuki

IEEJ Transactions on Fundamentals and Materials 133 ( 11 ) 606 - 607 2013.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Advanced oxidation process (AOP) with hydroxyl radicals (OH) is considered to be useful for water purification through oxidation; therefore, we proposed a useful passing water-type ozonizer, which could generate discharges even on the liquid surface. We first observed optical emissions due to the discharges and then confirmed the existence of O and OH radicals. Next, decomposition of Methylene Blue was examined. When the discharge was generated between a glass electrode and liquid, the AOP was achieved. The obtained results also indicated that various decomposition and treatment would be possible by selecting discharge form for our passing water-type ozonizer.

DOI： 10.1541/ieejfms.133.606

Influence of triple-junction on sparkover voltage for a series gap of arrester

通水型オゾナイザの放電形態が脱色特性に与える影響 Reviewed

塩満栄一, 有吉純也, 藤真介, 迫田達也, 貴島純次, 中島秀之

電気学会論文誌A 133 ( 11 ) 606 - 607 2013.11

Language：Japanese Publishing type：Research paper (scientific journal)

Tokunaga T., Nishikawa S., Sakoda T., Fukano T.

2013 IEEE Electrical Insulation Conference, EIC 2013 110 - 113 2013.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：2013 IEEE Electrical Insulation Conference, EIC 2013

Considering the latest development of advanced information society, a stable supply of electric power should be maintained. Lightning surge arrester can contribute to reduce electric failures due to overvoltage from lightning. Since 1970's, zinc oxide (ZnO) element with superior non-linear voltage (V) - current (I) characteristics has been widely installed. Even in Japan, the surge arrester with a series gap has been installed to distribution systems for reducing the electrical failures. As mentioned above, the ZnO element has a superior nonlinearity of V-I characteristic, which can achieve suppress of overvoltage energy. Furthermore, the ZnO surge arrester with a series gap can interrupt the following current, immediately. The surge arrester with a series gap is composed of a simple gap electrode, a ceramic spacer for fixing the gap of the electrodes, and ZnO elements. The upper and the bottom of the ceramic spacer face metallic electrodes; therefore there are triple-junction points between the ceramic spacer, the metallic electrode, and gas. It is well known that electric field strength near the triple-junction point becomes high because of a triple-junction effect. It is also considered that the triple-junction point becomes a source of primary electrons by field emission due to the high electric field. Therefore, the triple-junction effect may influence the discharge characteristics so that the investigation will contribute to the further stable operation of a surge arrester with a series gap. In this study, we carried out experiments concerning how the triple-junction effect influences discharge characteristics such as breakdown voltage and discharge ignition. We first varied the distance between the discharge axis and the triple-junction point and then evaluated the discharge ignition time. Additionally, several ceramic materials with various relative permittivity were used. Based on the results, we evaluated the optimum distance between the discharge axis and the triple-junction point, which would be useful for design of a surge arrester with a series gap. © 2013 IEEE.

DOI： 10.1109/EIC.2013.6554214

Evaluation of Discharge Ignition by Composite Pollution Test with Silicone Rubber

OSHIKAWA Norihito, TOKUNAGA Tatsuya, HONDA Kazufumi, MIYAKE Takuma, SAKODA Tatsuya, ANJIKI Tomikazu

IEEJ Transactions on Fundamentals and Materials 133 ( 4 ) 205 - 210 2013.5

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Application of polymeric materials for electric power apparatus is spreading worldwide. However, the aged deterioration is anxious because of dry band arc discharges generated on the surface of the polymer materials. In this paper, we carried out composite pollution tests and measured the discharge ignition time of silicone rubber. The results showed that there was no large difference in the discharge ignition times obtained between ac and dc voltage applications. Additionally, it was shown that the difference of the discharge ignition was influenced by hygroscopic property of the pollution material.

DOI： 10.1541/ieejfms.133.205

Characteristics of a water plasma source with a porous glass membrane

複合汚損試験によるシリコーンゴム表面上の放電開始時間の評価 Reviewed

押川典仁, 徳永達也, 本田一史, 三宅琢磨,　迫田達也, 安食富和

電気学会論文誌A 133 ( 4 ) 205 - 210 2013.4

Language：Japanese Publishing type：Research paper (scientific journal)

SHIOMITSU Eiichi, KINO Hiroaki, YUJI Syohei, SAKODA Tatsuya, KIJIMA Junji, NAKASHIMA Hideyuki

2013 ( 10 ) 25 - 29 2013.1

Language：Japanese Publishing type：Research paper (scientific journal)

Influence of high electric field near a discharge gap on characteristics of impulse discharge

TOKUNAGA Tatsuya, NISHIKAWA Shinnosuke, SAKODA Tatsuya, FUKANO Takato, CHIBA Tomoki

2013 ( 1 ) 39 - 42 2013.1

Language：Japanese Publishing type：Research paper (scientific journal)

Influence of high electric field near a discharge gap on characteristics of impulse discharge

TOKUNAGA Tatsuya, NISHIKAWA Shinnosuke, SAKODA Tatsuya, FUKANO Takato, CHIBA Tomoki

2013 ( 10 ) 39 - 42 2013.1

Language：Japanese Publishing type：Research paper (scientific journal)

Influence of high electric field near a discharge gap on characteristics of impulse discharge

TOKUNAGA Tatsuya, NISHIKAWA Shinnosuke, SAKODA Tatsuya, FUKANO Takato, CHIBA Tomoki

2013 ( 42 ) 39 - 42 2013.1

Language：Japanese Publishing type：Research paper (scientific journal)

Characteristics of a water plasma source with a porous glass membrane

SHIOMITSU Eiichi, KINO Hiroaki, YUJI Syohei, SAKODA Tatsuya, KIJIMA Junji, NAKASHIMA Hideyuki

2013 ( 1 ) 25 - 29 2013.1

Language：Japanese Publishing type：Research paper (scientific journal)

Characteristics of a water plasma source with a porous glass membrane

SHIOMITSU Eiichi, KINO Hiroaki, YUJI Syohei, SAKODA Tatsuya, KIJIMA Junji, NAKASHIMA Hideyuki

2013 ( 42 ) 25 - 29 2013.1

Language：Japanese Publishing type：Research paper (scientific journal)

Insulation Characteristics of Polymer Insulator Materials with Algaes

電気絶縁機器用ポリマー外被材の直流・交流時の電気的特性の評価 Reviewed

三宅琢磨, 瀬尾裕也, 押川典仁, 迫田達也, 大坪昌久, 安食富和

電気設備学会誌 32 ( 8 ) 594 - 599 2012.12

Language：Japanese Publishing type：Research paper (scientific journal)

微細藻類がポリマーがいし外被材の絶縁特性に与える影響の評価 Reviewed

本田一史, 押川典仁, 三宅琢磨, 迫田達也, 吉田ナオト, 古河征二

電気学会論文誌A 132 ( 11 ) 944 - 950 2012.12

Language：Japanese Publishing type：Research paper (scientific journal)

HONDA Kazufumi, OSHIKAWA Norihito, MIYAKE Takuma, SAKODA Tatsuya, YOSHIDA Naoto, FURUKAWA Seiji

IEEJ Transactions on Fundamentals and Materials 132 ( 11 ) 944 - 950 2012.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

Polymer insulator has some excellent properties such as being lightweight, hydrophobicity, and antiweatherability. However, the polymer material is made from organic matters whereby the aged deterioration due to electric discharges, polluted deposited, and microbes is worrying. In this study, we first investigated existence and kind of microbes on the surface of silicone rubber (SiR) insulators arranged outdoor for 11 years. Next, to investigate how the microbes influence insulation performance of polymeric materials, the salt fog tests were performed on SiR samples with the artificial cultured microbes. The microbes temporally increased the leakage current due to discharges; however, the degradation didn't continue because the discharges rejected the microbes.

DOI： 10.1541/ieejfms.132.944

Frequency Dependence on Etching Characteristics of Silicon using Surface Discharge Plasma

ARIMURA Takuya, HIRANO Keta, HAMADA Toshiyuki, SAKODA Tatsuya

IEEJ Transactions on Fundamentals and Materials 132 ( 4 ) 333 - 334 2012.10

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

We proposed a maskless plasma etching technique for fabrication of front contact grooves on a single crystalline silicon solar cell. In this paper, we evaluated characteristics of silicon etching with various output frequency of ac power source. The etching rate in the direction of the groove width was suppressed while that in the direction of the groove depth increased with increasing output frequency of the power source. Thus, it was found that the increase of output frequency of a power source was effective in the case where the surface discharge plasma was applied to patterning.

DOI： 10.1541/ieejfms.132.333

Maximum Output Power Control using Short-Circuit Current and Open-Circuit Voltage of a Solar Panel

Maximum Output Power Control using Short-Circuit Current and Open-Circuit Voltage of a Solar Panel Reviewed

Takahiro Kato, Takuma Miyake, Daisuke Tashima, Tatsuya Sakoda, Masahisa Otsubo, Mitsuyuki Hombu

Japanese Journal of Applied Physics 10 ( 51 ) 10NF08-1 - 10NF08-4 2012.10

Language：English Publishing type：Research paper (scientific journal)

Takahiro Kato, Takuma Miyake, Daisuke Tashima, Tatsuya Sakoda, Masahisa Otsubo, Mitsuyuki Hombu

Japanese Journal of Applied Physics 51 ( 10 PART 2 ) 1 - 10 2012.10

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1143/JJAP.51.10NF08

Characteristics of powdered activated carbon treated with dielectric barrier discharge for electric double-layer capacitors

Daisuke Tashima, Hiromu Yoshitama, Tatsuya Sakoda, Akihito Okazaki, Takayuki Kawaji

Electrochimica Acta 77 198 - 203 2012.8

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.electacta.2012.05.105

Electrical characteristics obtained by impressing dc/ac voltage to polymeric housing material for electric power apparatus

MIYAKE Takuma, SEO Yuya, OSHIKAWA Norihito, SAKODA Tatsuya, OTSUBO Masahisa, ANJIKI Tomikazu

32 ( 8 ) 594 - 599 2012.8

Language：Japanese Publishing type：Research paper (scientific journal)

Studies on optimal gas supply for a maskless etching system with micro- discharge plasma operated at atmospheric pressure

Characteristics of powdered activated carbon treated with dielectric barrier discharge for electric double-layer capacitors Reviewed

Daisuke Tashima, Hiromu Yoshitama, Tatsuya Sakoda, Akihito Okazaki, Takayuki Kawaji

Electrochimica Acta 77 198 - 203 2012.5

Language：English Publishing type：Research paper (scientific journal)

沿面放電プラズマを用いたSiエッチングの電源周波数依存性 Reviewed

有村拓也, 平野啓太, 濱田俊之, 迫田達也

電気学会論文誌A 132 ( 4 ) 333 - 334 2012.4

Language：Japanese Publishing type：Research paper (scientific journal)

Toshiyuki Hamada, Takuya Arimura, Tatsuya Sakoda

Plasma Chemistry and Plasma Processing 32 ( 2 ) 325 - 332 2012.4

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1007/s11090-011-9343-y

Insulation characteristics of polymer insulator materials with algaes

Studies on optimal gas supply for a maskless etching system with micro- discharge plasma operated at atmospheric pressure Reviewed

Toshiyuki Hamada, Takuya Arimura, Tatsuya Sakoda

Plasma Chemistry and Plasma Processing 32 ( 2 ) 325 - 332 2012.3

Language：English Publishing type：Research paper (scientific journal)

HONDA Kazufumi, OSHIKAWA Norihito, MIYAKE Takuma, SAKODA Tatsuya, OTSUBO Masahisa, FURUKAWA Seiji, TANAKA Kenji

2012 ( 13 ) 37 - 42 2012.1

Language：Japanese Publishing type：Research paper (scientific journal)

Insulation characteristics of polymer insulator materials with algaes

HONDA Kazufumi, OSHIKAWA Norihito, MIYAKE Takuma, SAKODA Tatsuya, OTSUBO Masahisa, FURUKAWA Seiji, TANAKA Kenji

2012 ( 1 ) 37 - 42 2012.1

Language：Japanese Publishing type：Research paper (scientific journal)

Electrical characteristics obtained by impressing dc/ac voltage to polymeric housing material for electric power apparatus

Characteristics of hydrophobicity loss on silicone rubber surface during a dynamic drop test with direct current voltage application Reviewed

Yuya Seo, Norihito Oshikawa, Takuma Miyake, Tatsuya Sakoda, and Tomikazu Anjiki

Nanoscale Research Letters 7 ( 4 ) 1 - 4 2012.1

Language：English Publishing type：Research paper (scientific journal)

Miyake Takuma, Seo Yuya, Oshikawa Norihito, Sakoda Tatsuya, Otsubo Masahisa, Anjiki Tomikazu

The Journal of the Institute 32 ( 8 ) 593 - 599 2012

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Installation Engineers of Japan

Recently,much attention has been paid to polymeric materials used for housing of electric power apparatus. However,because polymeric material is made by organic matters,the aged deterioration is anxious. The lifetime of polymeric material is influenced by environmental conditions such as ultraviolet,acid rain,and polluted deposits. The change of the surface condition of polymeric material causes dry band arc discharges. To understand the long-term reliability of the insulation performance of polymeric materials,a composite pollution test of a liquid silicone rubber (LSR) was performed with dc or ac voltage application. After the test,heavy erosion was confirmed around a cathode electrode when dc voltage was applied. In the case of ac voltage application,heavy erosion was confirmed around a grounding electrode. It was also found that the initiation time of leakage current and cumulative charge depended on the kind of polluted deposits and that the difference of cumulative charge among polluted deposits in the case of dc voltage application was larger than that in the case of ac voltage application.

DOI： 10.14936/ieiej.32.593

Electrochemical Capacitances of Carbon Powder Treated with Dielectric Barrier Discharge

D. Tashima, R. Hirakawa, T. Sakoda and M. Otsubo

IEEE Conference on Electrical Insulation And Dielectric Phenomena 2011 Vol.1 109 - 112 2011.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/CEIDP.2011.6232608

Acoustic Emission Signals due to Several Discharges at a Joint Section of a XLPE cable

NAKAMURA Yuta, HIRANO Keita, KITAJIMA Junichi, SAKODA Tatsuya, KURIHARA Satoshi, KANEKO Koichiro, YARIMITSU Takayoshi

2011 ( 67 ) 81 - 84 2011.11

Language：Japanese Publishing type：Research paper (scientific journal)

Study on the discharge ignition time of Silicone Rubber for a composite polluted test

OSHIKAWA Norihito, SEO Yuya, MIYAKE Takuma, SAKODA Tatsuya, ANJIKI Tomikazu

2011 ( 67 ) 77 - 80 2011.11

Language：Japanese Publishing type：Research paper (scientific journal)

Assessing Long-term Reliability of Polymeric Housing Materials

Electrochemical Capacitances of Carbon Powder Treated with Dielectric Barrier Discharge Reviewed

D. Tashima, R. Hirakawa, T. Sakoda and M. Otsubo

IEEE Conference on Electrical Insulation And Dielectric Phenomena 2011.10

Language：English Publishing type：Research paper (international conference proceedings)

Takuma Miyake, Yuya Seo, Tatsuya Sakoda, Masahisa Otsubo

Institute of Electrical Engineers of Japan Transactions on Power and Energy 131 ( 6 ) 530 - 531 2011.9

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1541/ieejpes.131.530

Three-dimensional localization of partial discharge at joint section of XLPE cable using acoustic emission method combined with LabVIEW analysis

Nainggolan J., Sakoda T., Hayashi N., Kurihara S., Nagasato S., Kaneko K., Yarimitsu T.

European Journal of Scientific Research 59 ( 1 ) 134 - 142 2011.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：European Journal of Scientific Research

Acoustic emission (AE) sensor was used for detection of electric discharges and diagnosing a joint section of T-branch cross-linked polyethylene (XLPE) cable for 22 kV distribution system. From the head of cable joint, three AE sensors were arranged at the cable surface clockwise at 1200 to each other, and each sensor connected to an amplifier unit. Three AE sensors were used to generate three-dimensional calculation. A high voltage electrode was inserted into the joint section of cable, and then high voltage was applied to generate partial discharge (PD). PD current was detected by a Rogowski coil. The AE signal from the amplifier unit was sent to a digital oscilloscope and recorded in a personal computer for further analyses using LabVIEW. The correlation between AE signal and PD current was clarified. The increase of AE signal has the same linear tendency with increasing PD current. Thereafter, estimated three-dimensional PD locations were found around the head part of joint section of XLPE cable. © EuroJournals Publishing, Inc. 2011.

Fabrication of electrode groove on silicon solar cell by high-pressure surface discharge

Assessing Long-term Reliability of Polymeric Housing Materials Reviewed

Takuma Miyake, Yuya Seo, Tatsuya Sakoda, Masahisa Otsubo

Institute of Electrical Engineers of Japan Transactions on Power and Energy 131 ( 6 ) 530 - 531 2011.6

Language：English Publishing type：Research paper (scientific journal)

Hamada T., Arakawa S., Otsubo M., Sakoda T.

Electronics and Communications in Japan 94 ( 4 ) 733 - 739 2011.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electronics and Communications in Japan

We propose a low-cost plasma process technique to fabricate narrower front electrode grooves on a single crystalline silicon solar cell, in which a surface discharge operated at high pressure etches a silicon nitride film 150 nm thick on a silicon layer. Tests showed that the surface discharge could effectively etch the silicon nitride film in a short time; a high etching rate exceeding 3000 nm/min was obtained. Narrow and uniform grooves with a width of less than 70 μm were obtained when the pressure in the chamber, the back electrode length, and the etching time were 152 kPa, 2 mm, and 10 s, respectively. Narrower electrode grooves could be obtained when the back electrode length was short and the pressure was high. © 2011 Wiley Periodicals, Inc.

DOI： 10.1002/ecj.10305

Influence of Temperature on Characteristics of On-line Partial Discharge on Hydrogenerator Stator Windings

HIDAKA Toru, KANEKO Tadamitsu, MIYAKE Takuma, TAKENOUCHI Osamu, HAYASHI Noriyuki, SAKODA Tatuya, OTSUBO Masahisa

2011 ( 15 ) 25 - 28 2011.1

Language：Japanese Publishing type：Research paper (scientific journal)

Comparison of Degradation Phenomena on Silicone Rubbers Eroded by DC and AC Discharges

Daiki Shiibara, Yoshihiro Arata, Tatsuya Sakoda, Masahisa Otsubo, Tomikazu Anjiki

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 1009 - 1012 2010.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1541/ieejfms.130.1009

Etching Characteristics of Fabricated Grooves on Silicon Solar Cell Using Surface Discharge Plasma

Toshiyuki Hamada, Tatsuya Sakoda

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 999 - 1003 2010.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1541/ieejfms.130.999

Proposal of Multi-pass Laser Spectroscopic Technique for Diagnosing Atmospheric Pressure Discharge Plasmas

Tatsuya Sakoda, Mark Bowden

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 1026 - 1030 2010.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1541/ieejfms.130.1026

Studies on Acoustic Emission Signals Detected in an Oil-immersed Pole Transformer

Takuya Yamamoto, Toshihiko Nakashima, Tatsuya Sakoda, Masahisa Otsubo, Satoshi Kurihara, Shinya Nagasato, Takayoshi Yarimitsu

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 1031 - 1036 2010.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1541/ieejfms.130.1031

Relationship between Leakage Current and Pollution Deposits on the Surface of Polymeric Insulator

Takuma Miyake, Yuya Seo, Tatsuya Sakoda, Masahisa Otsubo

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 1037 - 1041 2010.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1541/ieejfms.130.1037

Maskless etching using atmospheric pressure non-thermal surface discharge plasma

Hamada T., Mizumoto T., Arimura T., Sakoda T.

IEEJ Transactions on Fundamentals and Materials 130 ( 10 ) 907 - 912 2010.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Fundamentals and Materials

We proposed and examined a maskless plasma surface patterning technique to fabricate 3 mm pitches of front contact grooves on a single crystalline silicon solar cell, in which the surface discharge operated at atmospheric pressure etched the silicon nitride film of 150 nm thickness on a silicon layer. In addition, we investigated etching characteristics of flat surface silicon and the distribution of electric field in our proposed surface discharge etcher. The electrical field distribution of our proposed surface discharge etcher was concentrated at triple junction points, and its strength electrical field intensity was around 4.0 × 10 6 V/m. Finally, we showed that the surface discharge could effectively etch the silicon nitride film in a 3 mm pitch. © 2010 The Institute of Electrical Engineers of Japan.

Location of Partial Discharge at Joint Section of XLPE Cable using Acoustic Emission Technique

Jannus M. N., T. Nakashima, T. Sakoda, M. Otsubo, S. Kurihara, S. Nagasato, T. Yarimitsu

2010 Annual Report Conference on Electrical Insulation and Dielectric Phenomena 2010 Vol.2 442 - 445 2010.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/CEIDP.2010.5723983

Study on change morphology of ZnO elements by a large impulse current

MIYAZAKI S., SAKODA T., OTSUBO M., MIYAKE T., NAKATA H., KINOSHITA F., YAMAGUCHI H.

電気学会研究会資料. ED, 放電研究会 2010 ( 60 ) 97 - 100 2010.11

Language：Japanese Publishing type：Research paper (scientific journal)

Diagnostics of Insulation Deterioration of Ethylene Propylene Rubber Using an Acoustic Emission Technique

Characteristics of Deteriorated ZnO Elements with Stripe-shaped Destruction Trace Reviewed

S. Miyazaki, T. Sakoda, M. Otsubo, T. Miyake, H. Nakata, F. Kinoshita

15th Asian Conference on Electrical Discharge 74 - 77 2010.11

Language：English Publishing type：Research paper (international conference proceedings)

Characteristics of Deteriorated ZnO Elements with Stripe-shaped Destruction Trace Reviewed

S. Miyazaki, T. Sakoda, M. Otsubo, T. Miyake, H. Nakata, F. Kinoshita

15th Asian Conference on Electrical Discharge 74 - 77 2010.11

Language：English Publishing type：Research paper (international conference proceedings)

Study on Insulation Degradation Difference between AC and DC Applications Reviewed

Takuma Miyake, Yuya Seo, Tatsuya Sakoda, Masahisa Otsubo, Tomikazu Anjiki

15th Asian Conference on Electrical Discharge 62 - 65 2010.11

Language：English Publishing type：Research paper (international conference proceedings)

Investigation of Partial Discharge Location at Joint Section of XLPE Cable Using Acoustic Emission Technique Reviewed

J. M. Nainggolan, Toshihiko Nakashima, Tatsuya Sakoda, Masahisa Otsubo, Satoshi Kurihara, Shinya Nagasato

15th Asian Conference on Electrical Discharge 30 - 33 2010.11

Language：English Publishing type：Research paper (international conference proceedings)

Relationship between Leakage Current and Pollution Deposits on the Surface of Polymeric Insulator Reviewed

Takuma Miyake, Yuya Seo, Tatsuya Sakoda, Masahisa Otsubo

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 1009 - 1012 2010.11

Language：English Publishing type：Research paper (scientific journal)

Comparison of Degradation Phenomena on Silicone Rubbers Eroded by DC and AC Discharges Reviewed

Daiki Shiibara, Yoshihiro Arata, Tatsuya Sakoda, Masahisa Otsubo, Tomikazu Anjiki

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 1009 - 1012 2010.11

Language：English Publishing type：Research paper (scientific journal)

Proposal of Multi-pass Laser Spectroscopic Technique for Diagnosing Atmospheric Pressure Discharge Plasmas Reviewed

Tatsuya Sakoda, Mark Bowden

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 1026 - 1030 2010.11

Language：English Publishing type：Research paper (scientific journal)

Studies on Acoustic Emission Signals Detected in an Oil-immersed Pole Transformer Reviewed

Takuya Yamamoto, Toshihiko Nakashima, Tatsuya Sakoda, Masahisa Otsubo, Satoshi Kurihara, Shinya Nagasato, Takayoshi Yarimitsu

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 1031 - 1036 2010.11

Language：English Publishing type：Research paper (scientific journal)

Etching Characteristics of Fabricated Grooves on Silicon Solar Cell Using Surface Discharge Plasma Reviewed

Toshiyuki Hamada, Tatsuya Sakoda

Institute of Electrical Engineers of Japan Transactions on Electrical and Electronic Engineering 130 ( 11 ) 999 - 1003 2010.11

Language：English Publishing type：Research paper (scientific journal)

大気圧沿面放電プラズマを用いたマスクレスエッチング Reviewed

濱田俊之, 水本貴之, 有村拓也, 迫田達也

電気学会論文誌A 130 ( 10 ) 907 - 912 2010.10

Language：Japanese Publishing type：Research paper (scientific journal)

Location of Partial Discharge at Joint Section of XLPE Cable using Acoustic Emission Technique Reviewed

Jannus M. N., T. Nakashima, T. Sakoda, M. Otsubo, S. Kurihara, S. Nagasato, T. Yarimitsu

2010 Annual Report Conference on Electrical Insulation and Dielectric Phenomena 442 - 445 2010.10

Language：English Publishing type：Research paper (international conference proceedings)

Diagnostics of Insulation Deterioration of Ethylene Propylene Rubber Using an Acoustic Emission Technique Reviewed

Tatsuya Sakoda, Toshihiko Nakashima, Masahisa Otsubo, Satoshi Kurihara, Shinya Nagasato, and Takayoshi Yarimitsu

IEEE Transactions on Dielectrics and Electrical Insulation 17 ( 4 ) 1242 - 1248 2010.8

Language：English Publishing type：Research paper (scientific journal)

Tatsuya Sakoda, Toshihiko Nakashima, Masahisa Otsubo, Satoshi Kurihara, Shinya Nagasato, and Takayoshi Yarimitsu

IEEE Transactions on Dielectrics and Electrical Insulation 17 ( 4 ) 1242 - 1248 2010.8

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/TDEI.2010.5539696

Study on the influence of the composite pollution to the polymeric materials

Development of a grooving system for solar cell Reviewed

Takuya Arimura, Takayuki Mizumoto, Toshiyuki Hamada, and Tatsuya Sakoda

16 th International Conference on Electrical Engineering 2010.7

Language：English Publishing type：Research paper (international conference proceedings)

MIYAKE Takuma, SEO Yuya, KANO Akifumi, SAKODA Tatsuya, OTSUBO Masahisa

2010 ( 34 ) 25 - 28 2010.1

Language：Japanese Publishing type：Research paper (scientific journal)

Study on the influence of the composite pollution to the polymeric materials

MIYAKE Takuma, SEO Yuya, KANO Akifumi, SAKODA Tatsuya, OTSUBO Masahisa

2010 ( 10 ) 25 - 28 2010.1

Language：Japanese Publishing type：Research paper (scientific journal)

Characteristics of Intensity Distribution and Long Term for On-line Measurement Partial Discharge on Hydrogenerator Stator Windings using Acoustic Emission Sensors

KANEKO Tadamitsu, HIDAKA Toru, MIYAKE Takuma, TAKENOUCHI Osamu, SAKODA Tatuya, OTSUBO Masahisa, ANDOU Mitoshi, SUGIHARA Takashi, OIWANE Makoto

2010 ( 34 ) 19 - 24 2010.1

Language：Japanese Publishing type：Research paper (scientific journal)

Characteristics of Intensity Distribution and Long Term for On-line Measurement Partial Discharge on Hydrogenerator Stator Windings using Acoustic Emission Sensors

KANEKO Tadamitsu, HIDAKA Toru, MIYAKE Takuma, TAKENOUCHI Osamu, SAKODA Tatuya, OTSUBO Masahisa, ANDOU Mitoshi, SUGIHARA Takashi, OIWANE Makoto

2010 ( 10 ) 19 - 24 2010.1

Language：Japanese Publishing type：Research paper (scientific journal)

Characteristics of Intensity Distribution and Long Term for On-line Measurement Partial Discharge on Hydrogenerator Stator Windings using Acoustic Emission Sensors

KANEKO Tadamitsu, HIDAKA Toru, MIYAKE Takuma, TAKENOUCHI Osamu, SAKODA Tatuya, OTSUBO Masahisa, ANDOU Mitoshi, SUGIHARA Takashi, OIWANE Makoto

2010 ( 10 ) 19 - 24 2010.1

Language：Japanese Publishing type：Research paper (scientific journal)

Study on the influence of the composite pollution to the polymeric materials

MIYAKE Takuma, SEO Yuya, KANO Akifumi, SAKODA Tatsuya, OTSUBO Masahisa

2010 ( 10 ) 25 - 28 2010.1

Language：Japanese Publishing type：Research paper (scientific journal)

Examination of Maskless Etching Technique Using a Localized Surface Discharge Plasma

HAMADA Toshiyuki, SAKODA Tatsuya, OTSUBO Masahisa

IEEJ transactions on electrical and electronic engineering : official journal of the Institute of Electrical Engineering of Japan / = 電気学会 5 ( 1 ) 115 - 117 2010.1

Language：Japanese Publishing type：Research paper (scientific journal)

Examination of Maskless Etching Technique Using a Localized Surface Discharge Plasma

Examination of Maskless Etching Technique Using a Localized Surface Discharge Plasma Reviewed

Toshiyuki Hamada, Tatsuya Sakoda, Masahisa Otsubo

IEEJ (Institute of Electrical Engineers of Japan) Transactions on Electrical and Electronic Engineering 5 ( 1 ) 115 - 117 2010.1

Language：English Publishing type：Research paper (scientific journal)

Toshiyuki Hamada, Tatsuya Sakoda, Masahisa Otsubo

IEEJ (Institute of Electrical Engineers of Japan) Transactions on Electrical and Electronic Engineering 5 ( 1 ) 115 - 117 2010.1

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1002/tee.20501

Evaluation of a stripe-shaped destruction trace of a zinc oxide element

Miyazaki satoshi, Kobayashi Tatsuya, Sakoda Tatsuya, Otsubo Masahisa, Nakata hidehiro, Kinoshita humihiro

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2010 ( 0 ) 554 - 555 2010

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2010.0.554.0

Studies on Investigation of a Stripe-shaped Destruction Mechanism of a Zinc Oxide Element

SAKODA Tatsuya, MIYAKAWA Yuichiro, MIYAZAKI Satoshi, OTSUBO Masahisa, IKUTA Masateru, YARIMITSU Takayoshi

IEEJ Transactions on Power and Energy 129 ( 12 ) 1593 - 1594 2009.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

To investigate a stripe-shaped destruction mechanism of a ZnO element used for a surge arrester, some breakdown tests were carried out. Applying a large impulse current to a ZnO element, a flashover trace was confirmed at the lateral face of the element. It was found that a trace of a stripe-shaped destruction was formed by a fact that AC current flew through the trace due to the flashover caused by a large impulse current.

DOI： 10.1541/ieejpes.129.1593

Study on Behavior of Sputtered Particles during Surface Discharges

Studies on Non-thermal Atmospheric Pressure Plasma Process Conditions for Groove Formation on Silicon Nitride for Silicon Solar Cells Reviewed

Toshiyuki Hamada, Tatsuya Sakoda and Masahisa Otsubo

Materials Science in Semiconductor Processing 12 ( 3 ) 106 - 112 2009.12

Language：English Publishing type：Research paper (scientific journal)

酸化亜鉛型避雷素子の筋状破壊機構の解明に関する研究 Reviewed

迫田達也, 宮川祐一郎, 宮崎哲司, 大坪昌久, 生田昌輝, 鎗光隆義

電気学会論文誌A 129 ( 12 ) 1593 - 1594 2009.12

Language：Japanese Publishing type：Research paper (scientific journal)

Tatsuya Sakoda

Jpn. J. Appl. Phys 48 ( 10 Part 1 ) 1060031 - 1060034 2009.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1143/JJAP.48.106003

Application of Thermal Analysis for Clarification of Degradation Characteristics of Silicone Rubber Exposed to Partial Arc Discharge

HAJI Kenichi, HIRANO Kimitaka, SAKODA Tatsuya, OTSUBO Masahisa

IEEJ transactions on electrical and electronic engineering : official journal of the Institute of Electrical Engineering of Japan / = 電気学会 4 ( 6 ) 793 - 795 2009.11

Language：Japanese Publishing type：Research paper (scientific journal)

Application of Thermal Analysis to Clarification of Degradation Characteristics of Silicone Rubber Exposed to Partial Arc Discharge

Investigation of Stripe-shaped Destruction Mechanism of ZnO Element Reviewed

S. Miyazaki, T. Sakoda, M. Otsubo, M. Ikuta, and T. Yarimitsu

2009 Korea-Japan Joint Symposium on Electrical Discharge and High Voltage Engineering 318 - 321 2009.11

Language：English Publishing type：Research paper (international conference proceedings)

Location of Partial Discharge at Joint Section of CV Cable Using Acoustic Emission Technique Reviewed

K. Sakamoto, T. Nakashima, T. Sakoda, M. Otsubo, T. Yarimitsu, S. Nagasato, and S. Kurihara

2009 Korea-Japan Joint Symposium on Electrical Discharge and High Voltage Engineering 314 - 317 2009.11

Language：English Publishing type：Research paper (international conference proceedings)

Characteristics of Acoustic Emission Signals Detected in an Oil-immersed Pole Transformer Reviewed

M. Kurose, T. Yamamoto, T. Sakoda, and M. Otsubo

2009 Korea-Japan Joint Symposium on Electrical Discharge and High Voltage Engineering 310 - 313 2009.11

Language：English Publishing type：Research paper (international conference proceedings)

Studies on Etching Characteristics of Fabricated Grooves on Silicon Solar Cell Using Surface Discharge Reviewed

T. Hamada, T. Sakoda, and M. Otsubo

2009 Korea-Japan Joint Symposium on Electrical Discharge and High Voltage Engineering 234 - 237 2009.11

Language：English Publishing type：Research paper (international conference proceedings)

Proposal of Laser Raman Scattering Technique for Measurement of Molecular Density in Atmospheric Pressure Discharge Reviewed

Tatsuya Sakoda and Mark Bowden

2009 Korea-Japan Joint Symposium on Electrical Discharge and High Voltage Engineering 230 - 233 2009.11

Language：English Publishing type：Research paper (international conference proceedings)

Characteristics of Distribution and Intensity for On-line Measurement Partial Discharge on Hydrogenerator Stator Windings using Acoustic Emission Sensors Reviewed

T. Kaneko, T. Hidaka, T. Miyake, M. Otsubo, T. Sakoda, O. Takenouchi, M. Andou

2009 Korea-Japan Joint Symposium on Electrical Discharge and High Voltage Engineering 87 - 90 2009.11

Language：English Publishing type：Research paper (international conference proceedings)

Application of Thermal Analysis to Clarification of Degradation Characteristics of Silicone Rubber Exposed to Partial Arc Discharge Reviewed

Kenich Haji, Kimitaka Hirano, Tatsuya Sakoda, Masahisa Otsubo

IEEJ (Institute of Electrical Engineers of Japan) Trans. on Electrical and Electronic Engineering 4 ( 6 ) 793 - 795 2009.11

Language：English Publishing type：Research paper (scientific journal)

Kenich Haji, Kimitaka Hirano, Tatsuya Sakoda, Masahisa Otsubo

IEEJ (Institute of Electrical Engineers of Japan) Trans. on Electrical and Electronic Engineering 4 ( 6 ) 793 - 795 2009.11

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1002/tee.20483

Thermal Analyses of Silicone Rubber Exposed to Partial Arc Discharges

HAJI Kenichi, HIRANO Kimitaka, SAKODA Tatsuya, OTSUBO Masahisa

The Journal of the Institute of Electrical Installation Engineers of Japan 29 ( 10 ) 865 - 870 2009.10

Language：Japanese Publishing type：Research paper (scientific journal)

Influence of Electrification of Droplet on Hydrophobicity Reduction of Polymer Material during a Dynamic Drop Test

局部アーク放電に曝されたシリコーンゴムの熱解析 Reviewed

枦健一, 平野公孝, 迫田達也, 大坪昌久

電気設備学会論文誌 29 ( 10 ) 865 - 870 2009.10

Language：Japanese Publishing type：Research paper (scientific journal)

Study on Behavior of Sputtered Particles during Surface Discharges Reviewed

Tatsuya Sakoda

Jpn. J. Appl. Phys 48 ( 10 ) 106003-1 - 106003-4 2009.10

Language：English Publishing type：Research paper (scientific journal)

Dynamic Drop Testにおける帯電及び塩分による試料表面の撥水性への影響 Reviewed

椎原大輝, 荒田由浩, 枦健一, 三宅琢磨, 迫田達也, 大坪昌久

電気学会論文誌A 129 ( 9 ) 657 - 663 2009.9

Language：English Publishing type：Research paper (scientific journal)

Ozone Generation Using Micro Barrier Discharge in Water Reviewed

Tatsuya Sakoda, Yoshihisa Matsuda, Seiji Baba

J. Plasma Fusion Res. SERIES 8 623 - 626 2009.8

Language：English Publishing type：Research paper (scientific journal)

Studies on Discharge Mechanism of Micro-plasma Ozonizer Operated in Water Reviewed

Tatsuya Sakoda, Yoshihisa Matsuda, Yuji Tanaka, Seiji Baba, Junji Kijima, and Hideyuki Nakashima

IOA 19th World Congress & Exhibition 12-1-1 - 12-1-4 2009.8

Language：English Publishing type：Research paper (international conference proceedings)

HAJI Kenichi, SHIIBARA Daiki, ARATA Yoshihiro, SAKODA Tatsuya, OTSUBO Masahisa

IEEJ Transactions on Fundamentals and Materials 129 ( 5 ) 386 - 387 2009.7

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

The dynamic drop test was proposed as a method to evaluate hydrophobicity reduction of polymer materials. In this test, the formation change of a water channel was confirmed, and thereafter, the remained droplets and the dropped droplets on the sampled surface were repulsed each other. The distributions of electrification on the droplet and the sample surface were measured. The influence of the electrified droplet on the hydrophobicity reduction was examined. The results showed that the polarity on the sample surface changed by the dropped droplet, leading to the hydrophobicity loss.

DOI： 10.1541/ieejfms.129.386

Plasma Grooving System Using Atmospheric Pressure Surface Discharge Plasma

Studies on Si etching using atmospheric pressure surface discharge plasma Reviewed

T. Hamada, T. Sakoda, and M. Otsubo

Proc. of The 10th International Symposium on Sputtering and Plasma Processes 496 - 499 2009.7

Language：English Publishing type：Research paper (scientific journal)

STUDIES ON ETCHINGS OF SILICON NITRIDE FILMS WITH VARIOUS FILM THICKNESS SILICON SUBSTRATES USING SURFACE DISCHARGE Reviewed

T. Hamada, T. Sakoda, and M. Otsubo

Proceedings of the 4th International Congress on Cold Atmospheric Pressure Plasmas 37 - 40 2009.6

Language：English Publishing type：Research paper (international conference proceedings)

STUDIES ON FORMATION OF ELECTRODE GROOVES FOR SOLAR CELL USING HIGH PRESSURE SURFACE DISCHARGE Reviewed

T. Hamada, T. Sakoda, and M. Otsubo

Proceedings of the 4th International Congress on Cold Atmospheric Pressure Plasmas 33 - 36 2009.6

Language：English Publishing type：Research paper (international conference proceedings)

Toshiyuki Hamada, Tatsuya Sakoda, Masahisa Otsubo

Plasma Chemistry and Plasma Processing 29 ( 3 ) 197 - 204 2009.6

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1007/s11090-009-9170-6

Studies on Non-thermal Atmospheric Pressure Plasma Process Conditions for Groove Formation on Silicon Nitride for Silicon Solar Cells

Toshiyuki Hamada, Tatsuya Sakoda and Masahisa Otsubo

Materials Science in Semiconductor Processing 12 ( 3 ) 106 - 112 2009.6

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.mssp.2009.08.005

Detection of Weak Discharges in a Pole Transformer using an AE Sensor

Dynamic Drop Testにおけるポリマー材料の撥水性低下に及ぼす水滴の帯電の影響 Reviewed

枦健一, 椎原大輝, 荒田由浩, 迫田達也, 大坪昌久

電気学会論文誌A 129 ( 5 ) 386 - 387 2009.5

Language：Japanese Publishing type：Research paper (scientific journal)

Plasma Grooving System Using Atmospheric Pressure Surface Discharge Plasma Reviewed

Toshiyuki Hamada, Tatsuya Sakoda, Masahisa Otsubo

Plasma Chemistry and Plasma Processing 29 197 - 204 2009.5

Language：English Publishing type：Research paper (scientific journal)

Yamamoto Takuya, Kurose Mitsuharu, Sakoda Tatsuya, Otsubo Masahisa, Yarimitsu Takayoshi, Nagasato Shinya, Akaiwa Shigeru

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2009 ( 0 ) 213 - 213 2009

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2009.0.213.0

Characteristics of AE waves in oil immersed pole transformer

Kurose Mitsuharu, Yamamoto Takuya, Sakoda Tatsuya, Otsubo Masahisa, Yarimitsu Takayoshi, Nagasato Shinnya, Akaiwa Shigeru

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2009 ( 0 ) 214 - 214 2009

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2009.0.214.0

Characteristics of On-line and Off-line Partial Discharge for Hydorogenerator Stator Windings with AE Sensor and CT Sensor

I. Maeda, T. Kaneko, O. Takenouchi, T. Miyake, T. Sakoda, M. Otsubo, S. Fukumoto, A. Tokumitsu, T. Kai, M. Ando

Proceedings of 2008 International Symposium on Electrical Insulating Materials 577 - 580 2008.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/ISEIM.2008.4664533

Fundamental research on characteristics of hydrophobicity disappearance of silicone rubber surface in dynamic drop test

Shiibara D., Haji K., Sakoda T., Otsubo M.

Proceedings of the International Symposium on Electrical Insulating Materials 99 - 102 2008.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Proceedings of the International Symposium on Electrical Insulating Materials

A study on the development of deterioration / performance evaluation method for outdoor electric insulation of polymer materials is pushed forward now in the International Council on Large Electric Systems (CIGRE). The small scale docimasy (Dynamic Drop Test) which could evaluate a disappearance characteristic of the hydrophobicity easily was suggested [1] . This test method is to evaluate the loss of hydrophobicity to drop electrically-charged water droplets on the sample surface continuously. We applied this dynamic drop test (DDT) to polymer materials which differ in the amount of Alumina Tri-Hydrate (ATH) filled and investigated factors about the change of hydrophobicity, in which the surface roughness and difference of the quantity of migration of the low molecular weight (LMW) were examined.

DOI： 10.1109/ISEIM.2008.4664506

Influence of Temperature Variation on Characteristics of ZnO Elements

Y. Miyakawa, T. Sokoda, M. Otsubo and M.Ikuta

Proceedings of 2008 International Symposium on Electrical Insulating Materials 119 - 122 2008.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/ISEIM.2008.4664511

Relation Between Leakage Current and NSDD on the Surface of Polymer Insulator

Y. Yamashita, T. Miyake, H. Haji, T. Sakoda, M. Otsubo

roceedings of 2008 International Symposium on Electrical Insulating Materials 103 - 106 2008.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/ISEIM.2008.4664507

Characteristics Evaluation of the Partial Arc Discharge and the Silicone Rubber Surface by Dynamic Drop Test

高気圧沿面放電による太陽電池用電極溝の作製 Reviewed

濱田俊之, 荒川純一, 大坪昌久, 迫田達也

電気学会論文誌A 128-A ( 12 ) 733 - 739 2008.12

Language：English Publishing type：Research paper (scientific journal)

Studies on Erosion of Silicone Rubber Exposed to Partial Arc Discharges Reviewed

Kenich Haji, Yong Zhu, Masahisa Otsubo, Tatsuya Sakoda

Polymer Degradation and Stability 93 ( 12 ) 2214 - 2221 2008.12

Language：English Publishing type：Research paper (scientific journal)

Haji, Kenichi; Shiibara, Daiki; Otsubo, Masahisa, Sakoda Tatsuya, Yoshihiro Arata

2008 Annual Report Conference on Electrical Insulation Dielectric Phenomena 2008 272 - 275 2008.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/CEIDP.2008.4772897

Fabrication of Electrode Groove on Silicon Solar Cell using High-Pressure Surface Discharge

HAMADA Toshiyuki, ARAKAWA Shunichi, OTSUBO Masahisa, SAKODA Tatsuya

IEEJ Transactions on Fundamentals and Materials 128 ( 12 ) 733 - 739 2008.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

We proposed a low-cost plasma process technique to fabricate narrower front electrode grooves on a single crystalline silicon solar cell, in which the surface discharge operated at high-pressure etched the silicon nitride film of 150 nm thickness on a silicon layer. The results showed that the surface discharge could effectively etch the silicon nitride film in a short time and that a high etching rate more than 3000 nm/min was obtained. The narrow and uniform grooves with the width of less than 70 μm were obtained when the pressure in a chamber, the back electrode length and the etching time were 152 kPa, 2 mm and 10 s, respectively. The narrower electrode groove could be obtained when the back electrode length was short and the pressure was high.

DOI： 10.1541/ieejfms.128.733

Studies on Erosion of Silicone Rubber Exposed to Partial Arc Discharges

Kenich Haji, Yong Zhu, Masahisa Otsubo, Tatsuya Sakoda

Polymer Degradation and Stability 93 ( 12 ) 2214 - 2221 2008.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.polymdegradstab.2008.05.025

Studies of Elastic Waves in Ethylene Propylene Rubber Using Acoustic Emission Sensor

Masanori Takaoka, Tatsuya Sakoda, Masahisa Otsubo, Shigeru Akaiwa, Masatoshi Iki, Shigeharu Nakano

IEEE (Institute of Electrical Engineers of Japan) Transaction on Fundamentals and Materials Society 128 ( 10 ) 641 - 646 2008.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1541/ieejfms.128.641

Surface Modification of Carbon Electrode using Argon Plasma

Etching of Silicon Nitride Using Atmospheric Pressure Surface Discharge Plasma Reviewed

T. HAMADA, M. OTSUBO, T. SAKODA

The 7th International Conference on Materials Processing for AMFT7005_1 - 3 2008.11

Language：English Publishing type：Research paper (international conference proceedings)

D. Tashima, A. Sakamoto, M. Taniguchi, T. Sakoda, M. Otsubo

Vacuum 83 ( 3 ) 695 - 698 2008.10

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.vacuum.2008.04.060

Development of Novel Ozonizer Using Micro-Barrier Discharges Formed in Water

Characteristics Evaluation of the Partial Arc Discharge and the Silicone Rubber Surface by Dynamic Drop Test Reviewed

Haji, Kenichi; Shiibara, Daiki; Otsubo, Masahisa, Sakoda Tatsuya, Yoshihiro Arata

2008 Annual Report Conference on Electrical Insulation Dielectric Phenomena 272 - 275 2008.10

Language：English Publishing type：Research paper (international conference proceedings)

Surface Modification of Carbon Electrode using Argon Plasma Reviewed

D. Tashima, A. Sakamoto, M. Taniguchi, T. Sakoda, M. Otsubo

Vacuum 83 ( 3 ) 695 - 698 2008.10

Language：English Publishing type：Research paper (scientific journal)

Development of Novel Ozonizer Using Micro-Barrier Discharges Formed in Water Reviewed

Tatsuya Sakoda, Yoshihisa Matsuda, Seiji Baba

Japanese Journal of Applied Physics 47 ( 10 ) 8030 - 8032 2008.10

Language：English Publishing type：Research paper (scientific journal)

Tatsuya Sakoda, Yoshihisa Matsuda, Seiji Baba

Japanese Journal of Applied Physics 47 ( 10 PART 1 ) 8030 - 8032 2008.10

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1143/JJAP.47.8030

Electrochemical properties of modified carbon electrodes for electric double layer capacitors

Tashima D., Sakamoto A., Taniguchi M., Sakoda T., Otsubo M.

Surface and Coatings Technology 202 ( 22-23 ) 5560 - 5563 2008.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Surface and Coatings Technology

To improve capacitance and energy density of electric double layer capacitors (EDLCs), plasma surface treatments were carried out on surface of activated carbon sheets, and optimal conditions for the treatment were discussed. Operating gas pressure of argon was 20 Pa, and activated carbon sheets were set up so that they were covered with the dc glow discharge at 70 W. Electrochemical properties, including cyclic voltammetry (CV) and cole-cole plot of EDLCs in organic electrolyte, were examined. The results showed that capacitance of the plasma-treated EDLC increased to 11% in comparison with that of untreated one. The enhancement in specific capacitance was mainly attributable to increasing of ratio of surface area of the activated carbon sheets. © 2008.

DOI： 10.1016/j.surfcoat.2008.06.147

Optimization of Convex Electrode Geometry for Surface Discharge used for Fabrication of the Electrode Groove on Solar Cells

T. Hamada, T. Sakoda, M. Otsubo, K. Matsui and K. Nagasawa

Surface & Coating Technology 202 ( 22-23 ) 5405 - 5409 2008.8

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.surfcoat.2008.06.167

Characteristics of On-line Prolonged Partial Discharge on Hydrogenerator using Acoustic and Electrical Measurement Methods

Hiratani Ryuichi, Maeda Ikuya, Kaneko Tadamitsu, Tsuji Toshinori, Takenouchi Osamu, Otsubo Masahisa, Honda Chikahisa, Sakoda Tatsuya, Fukumoto Susumu, Tokumitsu Akihiro, Kai Tosiyasu, Andou Mitoshi

Memoirs of the Faculty of Engineering, Miyazaki University 37 163 - 168 2008.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Miyazaki University

Visualization of sound field with uniform phase distribution using laser beam microphone coupled with computerized tomography method

Tatsuya Sakoda and Yoshito Sonoda

Acoustical Science and Technology 29 ( 4 ) 295 - 299 2008.7

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1250/ast.29.295

The hydrophobicity disappearance characteristic of the silicone rubber surface in Dynamic Drop Test

Optimization of Convex Electrode Geometry for Surface Discharge used for Fabrication of the Electrode Groove on Solar Cells Reviewed

T. Hamada, T. Sakoda, M. Otsubo, K. Matsui and K. Nagasawa

Surface & Coating Technology 202 5405 - 5409 2008.6

Language：English Publishing type：Research paper (scientific journal)

SHIBARA Daiki, HAJI Kenichi, YAMASHITA Youhei, MIYAKE Takuma, SAKOTA Tatsuya, OTSUBO Masahisa

2008 ( 1 ) 29 - 34 2008.1

Language：Japanese Publishing type：Research paper (scientific journal)

Detection of Insulator Electric Discharge Sound from Counts and Cyclic Noise

NISHIDA Keisuke, SAKAMOTO Kouki, TSUJI Toshinori, SAKODA Tatsuya, OTSUBO Masahisa, HONDA Chikahisa

2008 ( 1 ) 41 - 44 2008.1

Language：Japanese Publishing type：Research paper (scientific journal)

Study on leakage current due to pollution deposit

YAMASHITA Youhei, HAZI Keniti, SHIIBARA Daiki, MIYAKE Takuma, SAKODA Tatuya, OTSUBO Masahisa

2008 ( 1 ) 23 - 27 2008.1

Language：Japanese Publishing type：Research paper (scientific journal)

Analyses of detected AE signals due to partial discharges in the insulating rubber

TAKAOKA Masashige, OSHIRO Taishi, HYAKUTA Yasuhisa, SAKODA Tatsuya, OTSUBO Masatoshi, ICHIBA Yasuhiro, YOSHIMITSU Kazuhiro, IKI Masatoshi, NAKANO Shigeharu

2008 ( 1 ) 19 - 22 2008.1

Language：Japanese Publishing type：Research paper (scientific journal)

Relation between Dry Band Arc Discharge Development and Erosion Shape on the Silicon Rubber

Keiich Haji, Yong Zhu, Masahisa Otsubo, Tatsuya Sakoda, Chikahisa Honda

2007 Annual Report Conference on Electrical Insulation and Dielectric Phenomena 2007 Vol.1 312 - 315 2007.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/CEIDP.2007.4451511

Characteristics of On-line Partial Discharge on Hydrogenerator by Hybrid Detection using Acoustic and Electrical Measurement Methods

Fujii Taishi, Hiratani Ryuichi, Toshinori Tsuji, Kaneko Tadamitsu, Takenouchi Osamu, Sakoda Tatsuya, Otsubo Masahisa, Honda Chikahisa, Kai Toshihiro, Fukumoto Susumu, Tokumitsu Akihiro, Andoh Mitoshi

Memoirs of the Faculty of Engineering, Miyazaki University 36 109 - 114 2007.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Miyazaki University

Basic Studies on Development of Ozone Generator using Porous Glass Film

Okamura Takeru, Morimoto Takuma, Miyake Takuma, Sakoda Tatsuya, Baba Seiji

Memoirs of the Faculty of Engineering, Miyazaki University 36 151 - 156 2007.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Miyazaki University

Observation of the MgO Degradation Process Using Laser Induced Fluorescence (2)

IKEDA Kazutaka, TAKAGI Shinya, SAKODA Tatsuya, OTSUBO Masahisa, HONDA Chikahisa

2007 ( 13 ) 1 - 4 2007.1

Language：Japanese Publishing type：Research paper (scientific journal)

The performance evaluation of polymer insulator materials by Dynamic Drop Test

Shiibara Daiki, Haji Kenichi, Miyake Takuma, Sakota Tatsuya, Ohtsubo Masahisa

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 246 - 246 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2007.0.246.0

Behavior of Mg atoms sputtered by the surface discharge on imitative PDP electrode

Takagi Shinya, Tanaka Yuji, Sakota Tatsuya, Honda Chikahisa

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 472 - 472 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2007.0.472.0

Etching of Silicon nitride film Using High Pressure Surface Discharge

Arakawa Shunichi, Hamada Toshiyuki, Rokuta Tomomi, Kondou Ryuuji, Sakoda Tatsuya

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 473 - 473 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2007.0.473.0

Partial Discharge Characteristics of Hydrogenerator Stator Windings and Laboratory Experiments by Electrical and Acoustic Measurement Methods

Maeda Ikuya, Kaneko Masamitsu, Takenouchi Osamu, Sakota Tatsuya, Ohtsubo Masahisa, Honda Chikahisa, Fukumoto Susumu, Tokumitsu Akihiro, Kai Toshiyasu, Ando Yoshitoshi

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 256 - 256 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2007.0.256.0

Development of AE detection system for cable deterioration diagnosis

Takaoka Masashige, Hyakuta Yasuhisa, Ohshiro Taishi, Sakota Tatsuya, Ohtsubo Masahisa, Yoshimitsu Kazuhiro, Iki Masatoshi, Nakano Shigeharu

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 255 - 255 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2007.0.255.0

Reduction of Harmonic Currents and Evaluation of Luminous Efficiency in a Lag type Operating Circuit of a Metal Halide Lamp

kanou Akifumi, Kurozumi Masaaki, Sakota Tatsuya, Otsubo Masahisa

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 249 - 249 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2007.0.249.0

Surface Modification of Carbon Electrode for Electric Double Layer Capacitor using Dielectric Barrier Discharge

Esaki Masatoshi, Takada Shinji, Tashima Daisuke, Sakoda Tatsuya, Otubo Masahisa

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 461 - 461 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2007.0.461.0

Influence of pollution of polymer insulator on Leakage Current in Field Test.

Yamashita Yohei, Haji Kenichi, Shiihara Daiki, Miyake Takuma, Sakota Tatsuya, Otsubo Masahisa

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 146 - 146 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2007.0.146.0

Examination of Discharge Genaration through Micro-Babble in Discharge Gap

Matsuda Yoshihisa, Kido Shintaro, Ikeda Koichiro, Sakota Tatsuya, Baba Seiji, Kukizaki Masato

Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 389 - 389 2007

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu

DOI： 10.11527/jceeek.2007.0.389.0

RF PE-CVD characteristics for the growth of carbon nanotubes in a CH <inf>4</inf>/N<inf>2</inf> mixed gas

Sung Y., Yuji T., Sakoda T.

Proceedings - International Symposium on Discharges and Electrical Insulation in Vacuum, ISDEIV 2 600 - 603 2006.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Proceedings - International Symposium on Discharges and Electrical Insulation in Vacuum, ISDEIV

Characteristics of radio-frequency (RF) plasma-enhanced vapor deposition (PE-CVD) for the growth of carbon nanotubes (CNTs) in a CH,/N 2 mixed gas were investigated through characterization of the prepared CNTs and a numerical simulation. The preparation of the CNTs was performed by the single chamber plasma process where the catalyst sputter deposition using a capacitively coupled plasma (CCP) and the PE-CVD using a inductively coupled plasma were carried out in the same discharge chamber. The plasma chemistry which is useful for optimizing preparation conditions was evaluated using the numerical code which could calculate the temporal evolution of particle densities in the plasma. The results showed the usefulness of the single chamber process system. It was also found that CH4, HCN and C 2 H 6 radicals mainly contributed to the growth of CNTs. © 2006 IEEE.

DOI： 10.1109/DEIV.2006.357373

Monitoring of an MgO Degradation in AC Plasma Display Panel Using Multivariate Analysis Method

Y. M. Sung, K. Ikeda, C. Honda, T. Sakoda

Japanese Journal of Applied Physics 45 ( 10 B ) 8104 - 8108 2006.10

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1143/JJAP.45.8104

Selective Etching of Silicon Nitride Film on Single Crystalline Silicon Solar Cell Using Intensive Surface Discharge

Tatsuya Sakoda, Toshiyuki Hamada, Kunihiro Matsukuma, Hiroki Herai, Kazuo Matsui, Kazuo Nagasawa

Japanese Journal of Applied Physics 45 ( 5 A ) 3992 - 3993 2006.5

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1143/JJAP.45.3992

Plasma treatment on electrode surfaces of bifacial silicon solar cells

T. Sakoda, Y. M. Sung, K. Matsukuma

Solar Energy Materials & Solar Cells 90 ( 7-8 ) 1089 - 1097 2006.5

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.solmat.2005.06.008

Measurement of Low-Frequency Ultrasonic Wave in Water Using Acoustic Fiber Sensor

T. Sakoda, Y. Sonoda

IEEE Trans. on Ultrasonics, Ferroelectrics and Frequency Control 53 ( 4 ) 761 - 766 2006.4

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/TUFFC.2006.1611035

Optimum conditions for ozone formation in a micro dielectric barrier discharge

Y. M. Sung, T. Sakoda

Surface & Coating Technology 197 ( 2-3 ) 148 - 153 2005.7

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.surfcoat.2004.09.031

Additional Plasma Surface Texturing for Single-Crystalline Silicon Solar Cells Using Dielectric Barrier Discharge

Sakoda Tatsuya, Matsukuma Kunihiro, Sung Youl-Moon, Otsubo Kouji, Tahara Minoru, Nakashima Yoshihiro

Japanese Journal of Applied Physics 44 ( 4 ) 1730 - 1731 2005

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：公益社団法人応用物理学会

To reduce the light reflection from surfaces of single-crystalline solar cells, a new surface texturing technique using a dielectric barrier discharge was proposed and examined on wet-textured surfaces of single-crystalline Si substrates. Minute uneven structures were additionally formed on the entire area of a wet-textured surface of pyramid-like shape. When the discharge voltage was 3.5 kV, the reflectance was less than 8% at wavelengths from 400 to 1000 nm and showed a minimum of 5.3% at 520 nm.

DOI： 10.1143/JJAP.44.1730

Activation of electrode surface on silicon solar cell using dielectric barrier discharge

Sakoda T., Matsukuma K., Araki I., Sung Y., Terakawa T., Furukawa K.

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 43 ( 6 A ) 3275 - 3280 2004.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

To yield an activated electrode surface on a silicon solar cell, a surface treatment was examined using a dielectric barrier discharge instead of a wet cleaning technique. After the dry cleaning process using the dielectric barrier discharge, the surface state and the fill factor of the solar cell were evaluated. The results showed that the dielectric barrier discharge plasma could effectively activate the electrode surface of the solar cell in a relatively short time. Additionally, it was found that the surface treatment on finger electrodes played an essential role in the improvement of the fill factor.

Activation of Electrode Surface on Silicon Solar Cell Using Dielectric Barrier Discharge

Sakoda Tatsuya, Matsukuma Kunihiro, Araki Ichiro, Sung Youl-Moon, Terakawa Takeshi, Furukawa Katsuhiko

Japanese Journal of Applied Physics 43 ( 6 ) 3275 - 3280 2004

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：公益社団法人応用物理学会

DOI： 10.1143/JJAP.43.3275

Evaluation of Insulation Performance on Polymeric Surface by a Novel Separation Technique of Leakage Current

M. Otsubo, T. Hashigucchi, C. Honda, O. Takenouchi, T. Sakoda, Y. Hashimoto

IEEE on Dielectrics and Electrical Insulation 10 ( 6 ) 1053 - 1060 2003.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/TDEI.2003.1255783

Transmission and detection of light diffraction signal by low-frequency ultrasonic wave

Sakoda T., Sonoda Y.

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 42 ( 9 A ) 5821 - 5825 2003.9

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

Measurement of low-frequency ultrasonic waves in water was examined by the light diffraction effect of a visible laser beam. This laser beam was much narrower than the ultrasonic wavelength. Characteristics of detected signals agreed well with the theoretical prediction based on Fraunhofer diffraction. As shown in the results, light diffraction waves transmitted through a polarization-maintaining fiber could be detected correctly. The results enable us to construct a novel optical fiber sensor which will be used for the detection of low-frequency ultrasonic waves as well as the transmission of light diffraction signals.

Spatial Distribution of Charged Particles in a Magnetic Neutral Loop Discharge Etcher

Y. M. Sung, T. Sakoda

Surface & Coating Technology 166 ( 2-3 ) 135 - 140 2003.3

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1016/S0257-8972(02)00778-8

Observation of Copper Atoms Behavior in a Vacuum Arc Discharge using Laser Spectroscopy

Y. M.Sung, Y. Hayashi, Y. O. Yirenkyi, M. Otsubo, C. Honda, T. Sakoda

Journal of Vacuum Science & Technology A 21 ( 1 ) 180 - 185 2003.1

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1116/1.1531141

Studies on electron behaviors at downstream region of a neutral loop discharge plasma

T. Sakoda, Y. M. Sung

Journal of Vacuum Science & Technology A 20 ( 6 ) 1964 - 1968 2002.11

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1116/1.1513644

Two-dimensional Modeling and Optimization of a Neutral Loop Discharge Etcher in an Argon Plasma

Y. O. Yirenkyi, Y. M. Sung, M. Otsubo, C. Honda, T. Sakoda

Surface & Coating Technology 149 ( 2-3 ) 185 - 191 2002.1

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1016/S0257-8972(01)01440-2

Investigation of the conditions required for the formation of a magnetic neutral loop discharge plasma

Sakoda T., Okraku-Yirenkyi Y., Sung Y., Otsubo M., Honda C.

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 40 ( 11 ) 6607 - 6612 2001.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

In order to reveal the conditions required for the formation of a neutral loop discharge (NLD) plasma, distributions of excited atoms that are closely related to the distributions of the ionization rates were measured under various discharge conditions. Measurements of the distributions of these excited atoms were performed by laser induced fluorescence spectroscopy and optical emission spectroscopy. It was found that the results of these measurements were consistent with the theoretically predicted dependencies of electron heating on the magnetic field strength, the radio frequency (RF) electric field, and the frequency of the RF source. In addition, it was shown that the effects of electron-neutral collisions and of the finite size of the device set limitations on the formation of the NLD plasma.

Prebreakdown phenomena and formation processes of low-pressure glow discharges in Ar, Ar/N2 and Ar/O2 mixtures

Sakoda T., Okraku-Yirenkyi Y., Sung Y., Otsubo M., Honda C.

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 40 ( 11 ) 6600 - 6606 2001.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

In this research, both the prebreakdown phenomena and the transient processes from the prebreakdown phenomena to the glow discharge in low-pressure Ar gas, Ar/N 2 and Ar/O 2 mixtures were investigated by electrical and optical methods. The prebreakdown phenomenon in the Ar/N 2 mixture was similar to that of Ar gas, and a pulseless component has been observed. The prebreakdown phenomenon in the Ar/O 2 mixture differed from those in the Ar gas and Ar/N 2 mixture, and formed a pulse discharge. Thus, the prebreakdown phenomenon in the Ar gas has been changed to pulse discharge by mixing a small amount of O 2 gas which played an important role in the formation of pulse discharge.

Experiment and Numerical Analyses of Electron Temperature and Density Distribution in a Magnetic Neutral Loop Discharge Plasma

Y. O. Yirenkyi, Y. M. Sung, M. Otsubo, C. Honda, T. Sakoda

Journal of Vacuum Science & Technology A 19 ( 5 ) 2590 - 2595 2001.9

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1116/1.1397467

Diagnostics of transformer oil by elastic waves

Sakoda T., Nieda H., Ando K.

Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) 135 ( 1 ) 1 - 7 2001.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi)

In the diagnostics of oil-immersed transformers, a chemical analysis of generated gases in the oil is generally performed, evaluating the kinds of gases and their quantities. This method, however, involves numerous procedures and is difficult to use in the field to diagnose the deterioration of oil. Considering the current state of the advanced information society, no deterioration in power apparatus should be permitted and the diagnosis of deterioration must be performed reliably while the equipment is energized. Therefore, we attempted to diagnose insulation oil based on analyses of elastic waves produced by a pulse discharge in the oil. This technique uses the behavior of elastic waves in liquid, in which an incident wave causes a high-frequency oscillation component with increasing gas content. In this investigation, elastic waves were detected on the outside surface of an oil tank at gas concentrations of 0 to 10%. The detected waves were analyzed by the fast Fourier transform. It was found that frequency spectra of 400 to 1000 kHz were increasingly evident when the gas concentration in oil was higher than ∼5%. This indicates that our new technique is useful for the diagnostics of oil-immersed transformers using the oscillation behavior of elastic waves produced by bubbles in oil. © 2001 Scripta Technica.

DOI： 10.1002/1520-6416(20010415)135:1<1::AID-EEJ1>3.0.CO;2-L

Characteristics of Elastic waves Caused by Corona Discharges in an Oil Immersed Pole Transformer

T. Sakoda, H. Nieda, K. Ando

IEEE on Dielectrics and Electrical Insulation 8 ( 2 ) 276 - 283 2001.4

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/94.919956

Electric field calculation in composite dielectrics by first-order triangular surface charge method

Sakoda T., Nieda H., Ando K.

Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) 135 ( 1 ) 8 - 14 2001.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi)

This paper proposes a technique for calculating electric fields in composite dielectrics by the first-order triangular surface charge method. The proposed technique utilizes two kinds of triangular elements, namely, conforming and nonconforming elements: these are elements whose charge density is continuous and discontinuous between the neighboring elements, respectively. We basically apply nonconforming elements at the edges of a polyhedral shape where the normal component of electric field cannot be fixed. We have computed the electric field for a spherical or a rectangular solid dielectric in the presence of a uniform field. Comparison shows that the proposed first-order method works better than the zeroth-order one, and that, in particular, the combined use of conforming and nonconforming elements produces the highest accuracy. © 2001 Scripta Technica.

DOI： 10.1002/1520-6416(20010415)135:1<8::AID-EEJ2>3.0.CO;2-Y

Effect of the Metallic Contamination of the Gap-Spacer on the Leakage Current of ZnO Surge Arrester with the Series Gap

FUKANO T., HORIGUCHI T., OTSUBO M., SUNG Y.M., SAKODA T., NIEDA H.

The Journal of the Institute of Electrical Installation Engineers of Japan 20 ( 10 ) 828 - 834 2000.10

Language：Japanese Publishing type：Research paper (scientific journal)

Studies on the optimum condition for the formation of a neutral loop discharge plasma

Y. M. Sung, K. Uchino, K.. Muraoka, T. Sakoda

Journal of Vacuum Science & Technology A 18 ( 5 ) 2149 - 2152 2000.9

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1116/1.1286391

Analysis of acoustic emissions caused by the partial discharge in the insulation oil

Sakoda T., Arita T., Nieda H., Ando K.

IEEE International Conference on Conduction and Breakdown in Dielectric Liquids, ICDL 483 - 486 1999.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEE International Conference on Conduction and Breakdown in Dielectric Liquids, ICDL

In order to diagnose the deterioration of insulation and evaluate its location in oil-filled pole transformer, measurements of elastic waves brought by corona discharges in oil were performed based on an acoustic emission (AE) technique. The detected signals in these measurements were analyzed by means of a fast Fourier transform (FFT) and their properties were discussed theoretically. It was found that the AE signals due to the Lamb waves of symmetrical mode caused in a thin steel tank could be easily recognized by the FFT analyses of initial stages of the detected AE signals. This suggests that the accuracy on location of the AE sources in the transformer would be improved. Also, it was shown that a low pass filter was effective to improve the accuracy of location.

Acoustic emissions caused by the corona discharge in an oil-tank

Sakoda T., Arita T., Nieda H., Otsubo M., Honda C., Ando K.

IEE Conference Publication 5 ( 467 ) 1999.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEE Conference Publication

Measurements of sonic and ultrasonic waves brought by corona discharges were performed based on an acoustic emission (AE) technique, to diagnose the deterioration of insulation and its location in an oil - filled pole transformer. The detected signals in these measurements were analyzed by means of a fast Fourier transform (FFT) and their properties were discussed. It was found that the AE signals due to the Lamb waves caused in a thin steel tank can be easily recognized by the FFT analyses of initial stages of the detected AE signals. This indicates that the accuracy on location of the AE sources in the transformer can be improved. Also, it was shown that a low pass filter was effective to improve the accuracy of location.

Studies of Elastic Waves Caused by Corona Discharges in Oil

T. Sakoda, T. Arita, H. Nieda, K. Ando, M. Otsubo, C. Honda

IEEE on Dielectrics and Electrical Insulation 6 ( 6 ) 825 - 830 1999.12

Language：Japanese Publishing type：Research paper (scientific journal)

DOI： 10.1109/94.822022

Studies of a magnetic neutral loop discharge based on laser diagnostics of electron behavior and atomic processes

Sakoda T., Miyao T., Uchino K., Muraoka K.

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 36 ( 11 ) 6981 - 6985 1997.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

In order to understand plasma formation processes in a neutral loop discharge, measurements of population densities of excited levels of helium atoms were performed using laser induced fluorescence (LIF) spectroscopy. At the same time, profiles of electron density n e and electron temperature T e were measured using Thomson scattering. The results of these measurements were analyzed using a collisional-radiative model of helium atoms in the plasma. It was found that population densities of excited levels of the helium atoms were consistent with the values of n e and T e . This indicates that it is not necessary to consider an existence of a high energy electron component which may be supposed to theoretically exist in addition to the Maxwellian energy distribution function for the bulk of electrons at the measured temperature T e . Also, it was shown that the energy deposition to electrons in the vicinity of the neutral loop plays a essential role in the formation of the neutral loop discharge plasma.

Electron temperature and density profiles in a neutral loop discharge plasma

Sakoda T., Iwamiya H., Uchino K., Muraoka K., Itoh M., Uchida T.

Japanese Journal of Applied Physics, Part 2: Letters 36 ( 1 PART A/B ) 1997.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 2: Letters

Thomson scattering measurements of electron temperature and density in a neutral loop discharge (NLD) plasma were performed in order to reveal electron behavior around the neutral loop. The method yielded unambiguous and reliable results, enabling quantitative analyses of particle balance to be made. The results showed that the electron temperature had a peak on the neutral loop and, in contrast, the electron density had a peak at a position radially inward from the neutral loop. We suggest that charged particles are produced by electron impact ionization of argon atoms on the neutral loop and then flow radially inward. The effect of the magnetic field strength on the NLD plasma formation is also discussed.

Gas Temperature and Cu Vapor Density in an Impulse Discharge (特集:11th International Conference on Gas Discharges and their Applications)

Sakoda Tatsuya, Otsubo Masahisa, Honda Chikahisa, NIEDA Hiroshi

電気学会論文誌. A, 基礎・材料・共通部門誌 = The transactions of the Institute of Electrical Engineers of Japan. A, A publication of Fundamentals and Materials Society 116 ( 11 ) 953 - 958 1996.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：電気学会