電気光学Kerr効果による変圧器油浸モデルの電界分布測定に関する研究
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[研究背景]

 変圧器の内部絶縁は絶縁油とプレスボード(PB)の複合絶縁系から構成されている.また,機器の冷却効率を向上させるために,機器内部では絶縁油が強制流動されている.このとき,絶縁油とPBとの摩擦によって静電気的な帯電,いわゆる流動帯電が生じることが知られている.この現象により機器内部の電界分布が変歪し,絶縁能力の低下,さらには絶縁油中やPB沿面における放電の原因になる可能性が指摘されている.
 本研究では,電気光学Kerr効果を用いて油中電界分布の直接測定を行っている.この測定法では,油中の電界分布を乱すことなく非接触に測定することが可能である.現在,油中電界を0.1kV/cm という高感度で測定している.さらに,絶縁油を流動させ,流動帯電を模擬した状態での電界測定も行っている.これらの測定結果より,PB上の蓄積電荷や油中の空間電荷について,油中電荷挙動という観点から定量的な把握を行っている.これまでの研究により,油中電界分布の時間推移特性,温度特性,極性反転特性,流動帯電特性などを明らかにした.
 また近年,環境への配慮や防災の観点から,これまでの鉱油に替わり,環境低負荷なパームヤシ脂肪酸エステル(PFAE)や,引火点が高いシリコーン油が注目されている.PFAEは高い生分解性,低粘度,高引火点,高誘電率であり,またシリコーン油は,高誘電率,環境低負荷,PFAEより高い引火点を持つなどの特徴がある.これら絶縁油の変圧器用絶縁油としての本格的な実用化のため,油中電界分布,時間推移特性,極性反転特性などを明らかにし,油中電荷の基礎特性を把握した.



[学術論文]
(6) K. Kato, T. Nara, F. Endo, A. Yamazaki, H. Koide, Y. Hatta, T. Hikosaka and H. Okubo
"Space Charge Behavior in Palm Oil Fatty Acid Ester (PFAE) by Electro-optic Field Measurement" IEEE Transactions on Dielectrics and Electrical Insulation

(5) K.Nakamura, K.Kato, H.Koide, Y.Hatta, H.Okubo
"Fundamental Property of Electric Field in Rapeseed Ester Oil based on Kerr Electro-Optic Measurement" IEEE Transactions on Dielectrics and Electrical Insulation, Vol.13, pp.601-607, No.3, (2006)

(4) H.Okubo, M.Wakamatsu, N.Inoue, K.Kato, H.Koide
"Charge behavior in flowing oil in oil/pressboard insulation system by electro-optic field measurement", IEEE Transactions on Dielectrics and Electrical Insulation , Vol.10, pp.956-962, No.6, (2003)

(3) M.Wakamatsu, K.Kato, N.Inoue, H.Koide, H.Okubo
"DC field measurement in oil/pressboard composite insulation system by electro-optic Kerr effect", IEEE Transactions on Dielectrics and Electrical Insulation, Vol.10, pp.942-947, No.6, (2003)

(2) N.Inoue, M.Wakamatsu, K.Kato, R.Shimizu, Y.Nakagami, H.Okubo
"Charge accumulation mechanism in oil / pressboard composite insulation system based on optical measurement of electric field", IEEE Transactions on Dielectrics and Electrical Insulation, Vol.10, pp.491-497, No.3, (2003)

(1)
加藤, 澤田, 羽柴, 匹田, 大久保
"
光学的測定による変圧器油/プレスボード複合系電界分布の直流極性反転特性に対する検討", 電学論B, Vol.120, No.6, pp.844-850 (2000)


[発表実績]
(13) T. Nara, K. Kato, F. Endo and H. Okubo
"Study on Dielectric Breakdown at DC polarity reversal in oil / Pressboard-composite Insulation System", 2009 IEEE Conference on Electrical Insulation and Dielectric Phenomena, Virginia Beach, USA (2009)

(12) K. Kato and H. Okubo,
"Charge Behavior and Field Measurement Techniques in Different Kinds of Insulating Oil for Power Transformers", 16th International Conference on Dielectric Liquids, Poitiers, France (2008)

(11) S.Yamamoto, T.Nara, K.Kato, H.Koide, K.Fujii and H.Okubo
"Kerr Electro-Optic Measurement of Electric Field Distribution Rapeseed Ester Oil and Pressboard Composite System", 16th International Conference on Dielectric Liquids, Poitiers, France (2008)

(10) F.Endo, S.Yamamoto, T.Sadakane, A.Yamagishi, K.Miyagi and H.Okubo
"Analysis of Gasses Generated by Electrical Discharges in Low Viscosity Silicone Oil" 2008 International Conference on Condition Monitoring and Diagnosis, Beijing, China (2008)

(9) T.Sadakane, S.Yamamoto, K.Kato, F.Endo A.Yamagishi, K.Miyagi and H.Okubo
"Kerr Electro-Optic Measurement of Electric Field Distribution in Silicone Liquid Insulation Systems for Transformer", 15th International Symposium on High Voltage Engineering, Ljubljana, Slovenia (2007)

(8) S.Yamamoto, K.Kato, F.Endo, Y.Hatta, H.Koide and H.Okubo
"Kerr Electro-Optic Field Measurement in Palm Oil Fatty Acid Ester Transformer Insulation System", International Symposium on EcoTopia Science, Nagoya, Japan (2007)

(7) S.Yamamoto, K.Kato, F.Endo, Y.Hatta, H.Koide and H.Okubo
"Kerr Electro-Optic Field Measurement in Palm Oil Fatty Acid Ester Transformer Insulation System", 2007 IEEE Conference on Electrical Insulation and Dielectric Phenomena, Vancouver, Canada (2007)

(6) K.Nakamura, K.Kato, H.Koide, K.Fujii and H.Okubo
"Kerr Electro-Optic Measurement of Electric Field Distribution Rapeseed Ester Oil and Pressboard Composite System", 15th International Conference on Dielectric Liquid, Coimbra, Portugal (2005)

(5) M.Wakamatsu, K.Kato, H.Koide and H.Okubo
"The effects of insulator structure and insulating oil to charge accumulation in oil-immersed transformers", 7th International Conference on Properties and Applications of Dielectric Materials, (2003)


(4) K.Kato, M.Wakamatsu, N.Inoue, R.Shimizu, Y.Nakagami, H.Iwai and H.Okubo
"Space charge model in oil/pressboard insulation system by electro-optic field measurement", 14th ICDL, Graz, Austria (2002)

(3) N.Inoue, M.Wakamatsu, K.Kato, R.Shimizu, Y.Nakagami, H.Iwai and H.Okubo
"Investigation of charge behavior at oil pressboard interface in flowing oil by electro-optic field measurement", 14th ICDL, Graz, Austria (2002)

(2) N.Inoue, K.Kato, R.Shimizu, Y.Nakagami, H.Iwai and H.Okubo
"Mechanism of charge accumulation at flowing oil/pressboard interface based on optical measurement of electric field", IEEE CEIDP, Kitchner, Canada, No.7C-2 (2001)

(1) Y.Hashiba, K.Kato, R.Shimizu, Y.Nakagami, H.Iwai and H.Okubo
"Investigation of charge behavior in flowing transformer oil / pressboard composite insulation system by electro-optic field measurement", IEEE IAS Annual Meeting, Rome, Italy, Vol.2, pp.732-738 (2000)


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