Papers - SAKODA Tatsuya
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Effective Measurement of Elastic Waves due to Partial Discharges in Oil-immersed Transformer Reviewed
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.
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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.
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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.
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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
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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
<p>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.</p>
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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. -
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)
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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)
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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
<p>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 O<sub>3</sub> don’t contribute to the sterilization. High energy electrons, and radicals such as O and OH play an essential role for the sterilization.</p>
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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
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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.
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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.
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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)
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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)
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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.
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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)
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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)
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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)
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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)