Propagation of IG Current Underground Elucidated by Remanent Magnetization

Summary In our previous studies, we showed that the remanent magnetization of materials could be used to analyze lightning currents at ground level. In this study, using an IG (Impulse Generator) current as a model of lightning, we used remanent magnetization to investigate the underground propagation of IG currents. For this purpose, we dug a square hole with a side length of 80 cm and a depth of 13 cm and placed in it 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 was successfully used to analyze the circular magnetic field induced by the IG current and its transit point. Then the underground path of the IG current was determined to a depth of 12 cm. The current path was inclined by approximately 9° from the vertical direction, which may be attributed to a ground conductor being located east of the experimental area. To relate the magnetization intensity and the distance from the IG current, an inverse square relation was applied outside the area close to the transit point of the current. From the results obtained in this study, we conclude that the method using the remanent magnetization is useful for elucidating the polarity, intensity, and path of both IG and lightning currents underground. Further, the method of using remanent magnetization as a record of lightning currents may contribute to the development of an effective earth conductor for limiting damage caused by lightning. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(4): 1–8, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22484