雷撃のモデルとしてのIG電流の地中伝播の特性を磁化から探る

抄録

In our previous studies, we showed that the remanent magnetization of the material could analyze the lightning current at the ground. In this study, using IG (Impulse Generator) current as a model of lightning, we investigated the underground propagation of the IG current from the remanent magnetization. For this purpose, we dug a square hole with a side length of 80 cm and depth of 13 cm, and placed in it the magnetic samples prepared using sea sand. After injecting an IG current of 530 A underground, the magnetization of these samples was measured.
The directional distribution of magnetization successfully analyzed the circular magnetic field induced by the IG current and its transit point. Then, the underground path of IG current was determined to a depth of 12 cm. The path of current inclined by approximately 9° from the vertical direction, which may be attributed to the earth conductor being located east of the experimental area. As the relational expression between the intensity of magnetization and the distance from the IG current, an inverse square relation was applied besides the area near the transit point of the current.
From the results in this study, we conclude that the method using remanent magnetization is useful to elucidate the polarity, intensity and path of both the IG and lightning current underground. Further, the method of using remanent magnetization as a record of lightning current may contribute to the development of an effective earth conductor for limiting damage caused by lightning.