HR: 1340h
AN: AE23A-0830    [Abstracts]
TI: Lightning Observation on the Nikaho-Kogen Wind Farm in Japan
AU: Yokoyama, S
EM: yokoyama@criepi.denken.or.jp
AF: Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka-shi, Kanagawa-Ken, 240-0196 Japan
AU: * Wada, A
EM: jun@criepi.denken.or.jp
AF: Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka-shi, Kanagawa-Ken, 240-0196 Japan
AU: Hirose, T
EM: taichi_hirose@jpower.co.jp
AF: Electric Power Development Co., Ltd., 6-15-1 Ginza, Chuo-Ku, Tokyo, 104-8165 Japan
AB: Wind power is one of the most expected clean energy worldwide. But lightning damages of wind turbines have been reporting in many countries. The upward lightning flashes, which are initiated by the upward leader from the tall structures to the thunderstorms, are often observed in winter in Japan, because the winter thunderstorm height is very low compared to the summer thunderstorm. It is necessary to consider the probability of downward lightning flashes and upward lightning flashes for the windmills in winter. It is well known that positive lightning often occurs in winter. Positive lightning current sometimes have a long duration of several hundreds milliseconds and the total charge exceeds several hundreds coulombs. Positive lightning discharges with a large energy are threat for wind turbine blades. We started to observe the winter lightning on the Nikaho-Kogen wind farm in Akita prefecture in Japan for studying the lightning protection methods of wind turbine blades. The plant consists of fifteen windmills and the maximum height of a windmill is 93m with the power of 1650kw. The lightning observation is as follows: (1) Lightning current measurements using Rogowski coils and coaxial shunt resistors. We developed a new current measurement system for windmills. A Rogowski coil of 0.9 m in diameter was installed around the main shaft and a Rogowski coil of 4 m in diameter was installed at the tower bottom of windmill. (2) Lightning channel measurements with liquid crystal shutter cameras. The camera has a special shutter system to take the picture very quickly. If the strong luminosity like as a lightning stroke, a liquid crystal shutter is open within 5 microseconds. Main observational results are as follows: (1) A positive lightning flash composed of two strokes that a time interval between strokes is 97ms, first stroke peak current is +40.1kA and second stroke peak current is +33.5kA was observed. (2) Many pulse currents of upward leader discharges without return strokes were often measured. Since the upward discharges from the blades occur frequently under the low-altitude winter thunderstorms, there is the possibility of the partial destruction of the blades due to the cumulative stress of the blade materials by the upward discharges
DE: 3324 Lightning
DE: 3304 Atmospheric electricity
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting