| 摘要 |
A protection element (e.g., an arrester) protects a piece of equipment to be protected, from surge currents line terminals and an earth terminal. Surge current detection devices are provided on respective conductors connected to the arrester. Each of the surge current detection devices is to detect the surge current penetrated into a conductor for a short period of time, and includes a magnetic flux concentration member by which a magnetic flux produced by the penetrated surge current is concentrated in a given detection area at a high density, and a ferromagnetic material sheet positioned on the given detection area. The ferromagnetic material sheet includes a recording layer which is able to record and erase the penetration state of the surge current. A plurality of microcapsules are arranged in the recording layer, and each of the microcapsules contains a suitable liquid, and a plurality of magnetic particles suspended in the suitable liquid. An orientation state of the magnetic particles is varied by the concentrated magnetic flux, and can be visually recognized.
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