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Long-term characteristics of XLPE cables |
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| Authors: | Katsuichi Ohata Ginzo Katsuta Zensuke Iwata Yoshio Maruyama Yasuo Sekii Mamoru Kanaoka |
| Affiliation: | 1. The Tokyo Electric Power Co., Inc
Katsuichi Ohata graduated from the Department of Electrical Engineering, Gumma University, and joined the Tokyo Electric Power Co., Inc. He is currently a Deputy Manager of the Transmission and Transformation Facilities Construction Administration Division. He has been engaged mainly in the design, construction and maintenance of underground transmission lines.;2. The Tokyo Electric Power Co., Inc Ginzo Katsuta graduated in 1978 from the Department of Electrical Engineering, Tokyo Denki University. He then joined Tokyo Electric Power Co., Inc. He is a Deputy Manager of the Underground Cable Section of the Engineering Division. He has been engaged mainly in the design, construction and maintenance of underground transmission lines.;3. Furukawa Electric Co., Ltd Zensuke Iwata graduated in 1968 from the Department of Electrical Engineering, the University of Tokyo and joined the Furukawa Electric Co., Ltd. He is currently aGeneral Manager in the Power Engineering Design Department. He has been engaged mainly in research and development on insulation deterioration of XLPE cables as well as large-capacity EHV power cables including cryogenic cables and their accessories. He received the Progress Award of the I.E.E., Japan in 1979 and 1989, served as Board Member of the Tokyo Branch of the I.E.E., Japan in fiscal 1989 and 1990. and a member of the Special Committee in the Electric Power and Energy Section of the I.E.E., Japan. He is now a convenor of CIGRE WG 2 1-06. He is a member of IEEE, and the Low-Temperature Engineering Association.;4. Furukawa Electric Co., Ltd Yoshio Maruyama obtained a Master's degree from the University of Tokyo in 1971 and joined Furukawa Electric Co., Ltd. He is currently a senior researcher at the Chiba Research Laboratory. He is engaged mainly in research and development on plastic-insulated cables and high-voltage measurements.;5. Hitachi Cable, Ltd Yasuo Sekii obtained a Master's degree from the University of Tokyo in 1965 and joined Hitachi Cable, Ltd. He also has a Dr. of Eng. degree. He is currently a Senior Chief Researcher at Power System Laboratory. He has been engaged in research on insulation deterioration of XLPE cables as well as research and development of EHV XLPE cables and joints. He received a Paper Award of the I.E.E., Japan in 1976. He is a member of the Institute of Electronics, Information and Communication Engineers of Japan, and IEEE.;6. Hitachi Cable, Ltd Mamoru Kanaoka obtained a Master's degree from Kobe University and joined Hitachi Cable, Ltd. He is currently a senior researcher at Power System Laboratory. He is engaged mainly in research and development of EHV XLPE cables. |
| Abstract: | To study the long-term characteristics of XLPE cables installed in free air and in water, aging tests were conducted under various testing conditions using XLPE cables with both 3.5 mm and 6 mm insulation. From the Weibull plots of lifetime distribution under the voltage stress EL as the minimum breakdown strength, the minimum value of time to breakdown tL under the constant voltage was estimated. The results of accelerated aging tests of XLPE cables installed in free air demonstrated that the V-t characteristics of XLPE cables could not be described by the conventional inverse power law (t ∝ V?n) with a single constant life exponent n. Based on the microscopic observation of a sliced insulation removed from XLPE cables, it was concluded that bow-tie trees with longer tree length observed in cables tested in water were caused by the moisture from outside, whereas the trees in cables tested in free air were caused by the residual moisture originally existing in the insulation. The breakdown strength of the aged cables tested in water increases through cable drying. However, it does not recover to the original values. |
| Keywords: | XLPE cable insulation characteristics Weibull statistics V-t characteristics life exponent long-term aging test bow-tie tree |