Early Warning of Lightning Strokes to Power Apparatus Viewed from Time Transition of Electric Field Distribution on the Ground under Thundercloud

本项目取得的成果概括为以下七项：1.在位于金泽北方郊区的Kahoku-gata和位于名古屋西郊的Kisozaki内的几个地点同时观测了地面电场强度。2.本文提出了一种根据观测资料推测冬季雷暴云下电场区域分布的图解法。3.在记录的点放电电流波形上发现的大脉冲分量被确定为与闪电放电相关的大电场变化。4.本文将东北地区冬季61次自然闪电的地面电场区域分布存入我们的数据库。当Kahoku-gata总面积的30%以上被负电场强度所占据时，可能会发生许多不同极性的自然闪电放电。5.准确的中风位置是由双四分之一的VTR观测11个云-地自然闪光。这些都击中了距离地面上电场的正区和负区之间的边界约1公里的位置。6.名古屋附近的夏季闪电放电只发生在下午，而金泽附近的冬季闪电放电则发生在白天和夜间。7.根据研制的节电型空间电场仪记录，冬季强雷暴云下，地面附近产生几nC/m^3量级的电场，它随地面电场的增减有一定的时滞。在10米高的垂直棒电极上，靠近电极顶部的空间电场比同高度的空间电场减小一半左右。

Obtained results in this project are summarized as the following seven items ; 1. Simultaneous observation of the electric field intensity on the ground have been performed at several sites inside Kahoku-gata, a reclaimed land located in the northern suburbs of Kanazawa in winter, and Kisozaki, a reclaimed land in the western suburbs of Nagoya in summer. 2. A graphical method was developed to presume regional distribution of the electric field under the winter thundercloud on the basis of observed records. 3. Large pulsive components found on recorded waveforms of the point discharge current were identified as the large electric field change associated with lightning discharges. 4. The regional distribution of the electric field on the ground were stored in our data-base with respect to 61 natural lightnings in winter around Kahoku-gata. A number of natural lightning discharges with different polarities may occur when more than 30% of the total area of Kahoku-gata is occupied by the negative intensity of the electric field. 5. The accurate stroke locations were determined by the double-quarter VTR observations with respect to eleven cloud-to-ground natural flashes. These have struck positions within distance of about 1 km from the boundary between the positive and the negative areas of the electric field on the ground. 6. The summer lightning discharge around Nagoya only occurs in the afternoon, but the.winter one around Kanazawa occurs in day and night. 7. According to the records obtained by a developed battery-saving type Space-electric-field meter, order of a few nC/m^3 is produced around ground under the strong thundercloud in winter and it changes with a certain time lag with increasing or decreasing of the electric field on the ground. The space electric field close to the top of a vertical rod electrode, 10m high, is reduced to about half compared with that of the same height.