論文 - MAY THIN KHAING
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M. T. Khaing, N. Hirose, T. Sakoda, K. Kubo, T. Anjiki, T. Chiba
Journal of Electrostatics 140 2026年3月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Electrostatics
ZnO surge arrester with a spark gap has been employed to reduce electrical failures due to lightning strikes. The discharge time lag commonly occurs in a spark gap due to unstable discharge characteristics. In this study, a new electrode configuration with main and auxiliary electrodes is proposed to make sparkover stable. V-t characteristics and optical emissions of impulse discharge are observed. The auxiliary electrodes generate impulse corona discharge, which emits ultraviolet (UV) ray at the edges of them. Electrons optically released from negative ions in the air between main electrodes make the discharge time lag and its standard deviation small.
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Partial discharge behavior in epoxy resin including insulation paper 査読あり
S. Z. Linn Htet, T. Kondo, T. Miyake, M. T. Khaing, T. Sakoda
Journal of Electrostatics 140 ( 104242 ) 2026年3月
掲載種別：研究論文（学術雑誌）
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Khin M.O., Hirose N., Khaing M.T., Sakoda T., Nakayama Y., Niwa K.
IEEE Transactions on Dielectrics and Electrical Insulation 2026年
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：IEEE Transactions on Dielectrics and Electrical Insulation
Silicone rubber (SiR) is used for housing material of polymer insulators. This study focuses on the temporal variation in the shape of a water droplet on the SiR surface treated by surface discharge (SD). The SD treatment is used as a controlled electrical stress to investigate how the surface condition and the hydrophobicity of SiR change with aging. A 7 μL distilled water droplet is dropped on unused, 18-year-aged, and 20-year-aged specimens, and the contact angles (θ) were recorded for 600 s to obtain θ – t curves. The obtained curve is divided into four stages: primary maintenance, primary reduction, secondary maintenance, and secondary reduction. The unused specimens show a clear plateau in a secondary maintenance stage because low-molecular-weight (LMW) siloxanes may be dispersed from the SiR bulk to the surface and temporarily restore hydrophobicity. In aged specimens, θ decreases continuously without recovery. The continuous droplet observation after the SD treatment is a simple and effective method to evaluate the degradation of SiR.
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Suppression of Transformer Inrush Current by Applying Lower Frequency and Lower Voltage 査読あり
K. Nishijima, M. T. Khaing, T. Sakoda, T. Kamesawa, S. Yamamura, T. Nishimura, K. Terashi
IEEJ Transactions on Power and Energy 145 ( 8 ) 496 - 501 2025年8月
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Ieej Transactions on Power and Energy
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.
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Evaluation of the Degradation Degree of 20-Year-aged Insulator by Using Surface Discharge 査読あり
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年8月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：2025 IEEE 5th International Conference on Electrical Materials and Power Equipment Icempe 2025
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.
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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年8月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：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.
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EVALUATION OF DEGRADATION DEGREE OF ARTIFICIALLY DEGRADED SILICONE RUBBER SURFACE 査読あり
Nakayama Y., Niwa K., Khaing M.T., Sakoda T.
Iet Conference Proceedings 2025 ( 14 ) 1067 - 1071 2025年6月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：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.
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Locating Water-tree Degraded Cable Section by Measuring Residual Charges Induced by Voltage Pulse Wave 査読あり
M.T. Khaing, K. Watanabe, T. Sakoda, T. Takayama, K. Miyazaki
IEEE Transactions on Dielectrics and Electrical Insulation 2025年2月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Evaluation of Degradation Degree on Silicone Rubber by Using Surface Discharge 査読あり
M. T. Khaing, N. Hirose, T. Miyake, T. Sakoda, S. Goto, T. Anjiki, T. Chiba
IEEJ Transaction on Electrical and Electronic Engineering 2025年1月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Diagnosis of Degradation Degree on SiR Surface Used for Insulator by Surface Discharge 査読あり
M. T. Khaing, K. Yoshimura, T. Sakoda, S. Goto, T. Anjiki, T. Chiba, Y. Kasuga
2024 10th International Conference on Condition Monitoring and Diagnosis (CMD) 386 - 389 2024年12月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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Partial Discharge and Electrical Treeing Phenomena Within Two Spherical Voids in Epoxy Resin 査読あり
S.Z.L. Htet, T. Kondo, M.T. Khaing, T. Sakoda, Y. Harada, K. Takei, M. Ikeda, K. Miyazaki
2024 10th International Conference on Condition Monitoring and Diagnosis (CMD) 358 - 361 2024年12月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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Characterization of Surface Discharge Used for Measuring Degradation Degree of Polymer Insulator 査読あり
M. T. Khaing, T. Miyake, T. Sakoda
2024 IEEE 14th International Conference on the Properties and Applications of Dielectric Materials (ICPADM) 254 - 257 2024年11月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Short-Time Fabrication of Degraded Surface on Silicone Rubber Used for Insulators 査読あり
M. T. Khaing, K. Yoshimura, T. Miyake, T. Sakoda, S. Goto, T. Anjiki, T. Chiba, Y. Kasuga
IEEE Transaction on Dielectric and Electrical Insulation 31 ( 2 ) 1054 - 1061 2024年4月
担当区分：責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Evaluation of degradation degree of artificially degraded silicone rubber surface by using surface discharge 査読あり
M. T. Khaing, T. Miyake, T. Sakoda, U. Kanenari, Y. Nishihiro
Journal of Electrostatics 128 2024年3月
担当区分：責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Characteristics of Aged Silicone Rubber Insulators Used in Outdoor for 20 Years 査読あり
M. T. Khaing, K. Yoshimura, T. Miyake, T. Sakoda, U. Kanenari, Y. Nishihiro
IEEJ Transaction on Electrical and Electronic Engineering 19 ( 4 ) 454 - 460 2024年1月
担当区分：責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Formation of Degradation Layer on Silicone Rubber Used for Insulators 査読あり
M. T. Khaing, K. Yoshimura, T. Sakoda, S. Goto, T. Anjiki, T. Chiba, Y. Kasuga
2023 IEEE Electrical Insulation Conference (EIC) 209 - 212 2023年7月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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Degradation Monitoring of Silicone Rubber Used for Insulators 査読あり
M. T. Khaing, K. Yoshimura, T. Sakoda, J. Oasa, S. Higashiyama, Y. Inaoka
9th International Conference on Condition Monitoring and Diagnosis (CMD 2022) in Kitakyushu Japan 382 - 386 2023年1月
担当区分：筆頭著者, 責任著者 掲載種別：研究論文（国際会議プロシーディングス）
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Short-time evaluation technique of degradation degree by surface discharge 査読あり
M. T. Khaing, K. Yoshimura, T. Sakoda, S. Goto, T. Anjiki, T. Chiba, Y. Kasuga
IET Conference Proceedings 2023 ( 46 ) 992 - 996 2023年
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）