Importance

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Abstract

A secondary surge arrester has a line conductor and a ground conductor extending through a casing. A nonlinear voltage dependent resistive element and a fault current limiting fuse are connected between the conductors and are disposed within the casing. The fault current limiting fuse includes a fusible material surrounded by sand. The sand also surrounds the nonlinear voltage dependent resistive element. A heat sensitive material is disposed in close proximity to the fusible material and is viewable through a transparent cover. In the event of a failure of the nonlinear voltage dependent resistive element causing arcing, the fusible material fuses to open the current path between the conductors, and the sand absorbs energy by transforming state. Thus, the fault current limiting fuse limits current flow through the surge arrester and extinguishes the arc within the surge arrester so as to prevent violent fragmentation of the casing. Furthermore, the heat sensitive material changes in response to heat generated during failure of the nonlinear voltage dependent resistive element to indicate the operability of the secondary surge arrester.

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First Claim