To reduce the damages of electric apparatus stroked by surge current and lightning, it is important to grasp the path and magnitude of surge currents. But many normal current instruments are disqualified because of sudden phenomenon in the unspecified place. Magnetic material samples settled near current path preserve remanence magnetized by surge current. The new system for measuring remanence of rock enables to measure low-level remanence of bonded magnetic samples and to estimate the properties of inrush current. We experimentally considered the relationship between remanence and exciting current, and discusses the fusibility of estimating surge current.

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