Patent ID: 8410773

Claim:
A surge current detection device that is provided on a conductor connected to a protection element for protecting a piece of equipment to be protected from a surge current penetrated into said conductor, and that is adapted to detect the penetration of the surge current into the conductor, which device comprises: a magnetic flux concentration section that concentrates a magnetic flux, which defines a magnetic field generated by the surge current penetrated into said conductor, in a given detection area at a high density; and a ferromagnetic material sheet disposed over said detection area, wherein said ferromagnetic material sheet comprises: a sheet member having a rear surface and a front surface and disposed over said detection area so that the rear surface thereof is applied to said detection area; a recording layer provided on the front surface of the said sheet member and including a plurality of microcapsules, each of which contains a suitable liquid, and a plurality of magnetic particles suspended in said liquid, an orientation state of the magnetic particles varying according to the concentrated magnetic flux, whereby a penetration state of the surge current can be recorded and erased in said recording layer; and a transparent protective film covering said recording layer so that a recording state and an erasing state in said recording layer can be visually recognized.