絶縁診断技術の高度化
 [研究背景] ガス絶縁開閉装置(GIS)内部に金属異物が混入すると，金属異物先端の電界集中により部分放電(PD)が発生し，特に立上りの急峻なサージ電圧等が侵入した場合，絶縁破壊（BD）に至る可能性がある．そのため，通常運転時においてGIS内部の絶縁状態を高精度に診断する技術の確立が求められている．内部絶縁状態は金属異物のサイズ・形状や存在箇所に大きく依存するため，そのリスクを正確に判断するためには，これらを識別することが必要であるが，その方法は十分に確立されていないのが現状である．以上の背景より，本研究室では，実規模GISに金属異物をセットし，部分放電を測定することにより，金属異物のサイズ・形状，存在位置を識別する技術の確立を目指し研究をすすめている． PD電流パルス波形には放電の発生・進展に関する物理情報が含まれているため，PD電流パルス波形から得られる各種パラメータを解析することにより，PDメカニズムについて検討を行うことができる．本研究室の開発した，PD電流パルス波形を高速・高精度に測定・解析できるPD電流パルス波形解析法(PD-CPWA)を駆使し，交流電圧印加時におけるPD電流パルス波形をnsオーダーで計測し，電流値，立上り峻度di/dt，立上り時間tr，立下り時間tf などの時間推移について解析している．なお，測定感度は世界トップクラスの0.1pCである． また，PDはUHF帯の電磁波を放射する性質があり，現地におけるGISのPD検出にはこのUHF電磁波を測定するUHF法が一般的に用いられている．しかし，UHF法により得られるデータとPD現象との相関は未解明であるため，PD-CPWAにより蓄積したデータを活用するには両者の相関関係を明らかにする必要がある．そこで本研究室では，UHF法によるUHF電磁波測定とPD-CPWAによるPD電流測定を同時に行うことにより，PD電流とUHF電磁波の関係の明確化を行っている． 現在行っている主な研究を以下に示す． (1)金属異物（ガス中，固体絶縁物沿面）のサイズ・箇所がPD特性に与える影響の解明 (2)PD電流とUHF帯電磁波の相関関係およびGIS中電磁波伝搬特性の解明 (3)固体絶縁物沿面付着金属異物の放電発生メカニズムの解明 [学術論文] (7) H.Okubo, N.Hayakawa "A Novel Technique for Partial Discharge and Breakdown Investigation Based on Current Pulse Waveform Analysis" IEEE Trans. on Dielectrics and Electrical Insulation Vol.12, No.4, pp.736-744, 2005 (6) H.Okubo, N.Hayakawa, A.Matsushita "The Relationship Between Partial Discharge Current Pulse Waveforms and Physical Mechanisms" IEEE Electrical Insulation Magazine, Vol.18, No.3, pp.38-45, 2002 (5) 渋谷，早川，大久保 "N2/SF6混合ガス中におけるインパルス沿面放電進展メカニズム" 電学論B, Vol.121, No.4, pp.455-460, 2001 (4) 斎藤，高橋，早川，川北，大久保 "0.1Hz超低周波(VLF)交流高電圧印加時におけるGIS内金属異物挙動と絶縁破壊特性" 電学論B, Vol.121, No.3, pp.364-370, 2001 (3) N.Hayakawa, Y.Ishida, H.Nishiguchi, M.Hikita, H.Okubo "Mechanism of Impulse Creepage Discharge Propagation on Charged Dielectrics Surface in SF6 Gas" Trans. IEE of Japan, Vol.116-B, No.5, pp.600-606, 1996 (2) M.Hikita, Y.Ishida, N.Hayakawa, Y.Kito, H.Okubo "Creepage Discharge Propagation on Charged Dielectric Surface in SF6 Gas and Its Optical Observation" Trans. IEE of Japan, Vol.115-B, No.2, pp.180-186, 1995 (1) H.Okubo, M.Kanegami, M.Hikita "Creepage Discharge Propagation in Air and SF6 Gas Influenced by Surface Charge on Solid Dielectrics" IEEE Transaction on Dielectrics and Electrical Insulation, Vol.1, No.2, pp.294-304, 1994 [発表実績] (25) M. Asai, K. Nishizawa, N. Hayakawa, F. Endo, M. Yoshida, K. Uchida, H. Okubo "Detail Analysis of Particle-Initiated Partial Discharges in SF6 Gas for Condition Monitoring of GIS" 16th International Symposium on High Voltage Engineering, D-11, 2009 (24) H. Okubo, K. Nishizawa, T. Okusu, N. Hayakawa, F. Endo, M. Yoshida, K. Uchida, "Partial Discharge Detection Techniques under the Condition of Metallic Particle Adhering to Solid Spacer in SF6" Annual Report Conference on Electrical Insulation Dielectric Phenomena, 5A-06, 2008 (23) K. Nishizawa, T. Okusu, H. Kojima, N. Hayakawa, F. Endo, M. Yoshida, K. Uchida, H. Okubo "Particle Size Identification in GIS by Ultra High Speed Measurement of Partial Discharge" International Conference on Condition Monitoring and Diagnosis, D2-13, 2008 (22) N. Hayakawa, T. Okusu, K. Nishizawa, H. Kojima, F. Endo, M. Yoshida, K. Uchida, H. Okubo "Dependence of Partial Discharge Characteristics at Spacer Surface on Particle Size in SF6 Gas International Conference on Condition Monitoring and Diagnosis, A1-04, 2008 (21) T. Okusu, D. E. Mansour, K. Nishizawa, N. Hayakawa, F. Endo, M. Yoshida, T. Ogawa, H. Okubo "High Speed Measurement and Analysis of Partial Discharge Pulses in SF6 Gas Insulation System" International Symposium on EcoTopia Science 07, H04-02, 2007 (20) F. Endo, T. Okusu, K. Nishizawa, N. Hayakawa, M. Yoshida, T. Ogawa, H. Okubo "High Speed Measurement and Analysis of Partial Discharge Pulses in SF6 Gas Insulation System" 15th International Symposium on High Voltage Engineering, T7-152, 2007 (19) N. Hayakawa, Y. Sugimori, H. Okubo "Partial Discharge Current Pulse Waveform Analysis (PD-CPWA) Based on PD Mechanisms in Solid and Gas Media" International Symposium on Electrical Insulating Materials, pp.812-815, 2005 (18) H.Okubo, S.Watanabe, N.Hayakawa and T.Kumai "Insulation Degradation Mechanism of Epoxy Spacer Samples for GIS" Gaseous Dielectrics X, pp.353-360, Greece, 2004. (17) N.Hayakawa, S.Watanabe, T.Kumai, H.Okubo "Partial Discharge Characteristics Leading to Breakdown of GIS Spacer Samples with Degraded Insulation Performance" 7th Intnl. Conf. on Properties and Applications of Dielectric Materials, Nagoya Japan, 2003 (16) H.Okubo, Y.Okamoto, N.Hayakawa, T.Hoshino, S.Matsumoto "Partial Discharge Characteristics by Metallic Particle on Solid Insulator in GIS" International Symposium on High Voltage Engineering, p.332, 2003 (15) S.Watanabe, N.Hayakawa, T.Kumai, H.Okubo "Partial Discharge Characteristics of Long-Term Operated 550kV GCB Epoxy Spacer" 2002 Annual Report, Conference on Electrical Insulation and Dielectric Phenomena, pp.462-465, Mexico, 2002 (14) Y.Okamoto, N.Hayakawa, T.Hoshino, S.Matsumoto, H.Okubo "Influence of Solid Insulator and Metallic Particles on Partial Discharge Characteristics in GIS" 14th Int. Conf. on Gas Discharges and thier Applications, pp.192-195, 2002 (13) H.Okubo, A.Matsushita, S.Watanabe, N.Hayakawa, T.Kumai "Investigation of Electrical Insulation Diagnosis of Solid Insulators in GIS by Partial Discharge Current Pulse Waveform Analysis (PD-CPWA)" 2002 IEEE/PES T&D Yokohama, pp.925-930, Japan, 2002 (12) H.Okubo, A.Matsushita, N.Hayakawa "Selective Partial Discharge Measurement Technique for HV Electric Power Equipment" International Electrical Insulation Conference(INSUCON), pp.218-224, Germany, 2002 (11) A.Matsushita, K.Kato, N.Hayakawa, K,Kawakita, H.Okubo "Partial Discharge Current Pulse Waveform Analysis (CPWA) for Electrical Insulation Diagnosis of Solid Insulators in GIS" 2001 Annual Report, Conference on Electrical Insulation and Dielectric Phenomena, pp.348-351, Canada, 2001 (10) N.Hayakawa, K.Kato, K.Kawakita, H.Okubo "Metallic Particle Motion and Breakdown Characteristics in GIS with 0.1Hz Very Low Frequency (VLF) High Voltage Application International Symposium on High Voltage Engineering, Vol.4, pp.445-448, 2001 (9) H.Okubo, D.Shibutani, N.Hayakawa "Step Propagation Mechanism of Impulse Creepage Discharge in N2/SF6 Gas Mixtures" Gaseous Dielectrics IX, pp.339-344, 2001 (8) A.Matsushita, D.Shibutani, K.Kato, N.Hayakawa, K,Kawakita, H.Okubo "Time Transition of Partial Discharge Characteristics and Current Pulse Waveforms on Epoxy Surface in SF6 Gas" International Symposium on High Voltage Engineering, pp.360-363, India, 2001 (7) H.Okubo, T.Takahashi, N.Hayakawa, H.Saitoh, K.Morita, T.Kikkawa "Metallic Particle Behavior and Breakdown Characteristics in N2/SF6 Gas Mixture GIS" 13th Int. Conf. on Gas Discharges and thier Applications, pp.446-449, 2000 (6) N.Hayakawa, D.Shibutani, H.Okubo "Impulse Creepage Discharge Propagation Characteristics on Solid Dielectrics in N2/SF6 Gas Mixtures" 13th Int. Conf. on Gas Discharges and thier Applications, pp.299-302, 2000 (5) H.Okubo, T.Yoshida, N.Hayakawa "Propagation Characteristics of Impulse Creepage Discharge in N2/SF6 Gas Mixture" ,International Symposium on High Voltage Engineering, pp.188-191, 1999 (4) N.Hayakawa, T.Yoshida, H.Okubo "Creepage Discharge Propagation Characteristics in N2/SF6 and air/SF6 Gas Mixtures" Int. Workshop on High Volt. Eng., SP-99-19/HV-99-19, pp.97-102, 1999 (3) T.Yoshida, K.Kato, N.Hayakawa, H.Okubo "Impulse Creepage Discharge Propagation Characteristics and Mechanisms in SF6 Gas and Gan Mixture" Fourth Workshop & Conference on EHV Technology, pp1-5, 1998 (2) H.Okubo, Y.Ishida, H.Nishiguchi, N.Hayakawa, M.Hikita, Y.Kito "Mechanism of Step-Wise Propagation of Positive Impulse Creepage Discharge in SF6 Gas under the Influence of Negative Surface charging on Dielectrics" 11th Int. Conf. on Gas Discharges and thier Applications, pp.288-291, 1995 (1) M.Hikita, Y.Ishida, N.Hayakawa, Y.Kito, H.Okubo "Creepage Discharge Propagation on Charged Surface in SF6 Gas and its Optical Observation" IEE of Japan Power & Energy, No.142, pp.239-244, 1994. |