Joslyn Manufacturing Co.

G & W Electric Specialty Company

Howard E Swanson

Steven P Hensley

Joseph C Osterhout

William R Rueth, Jr

Alex Demetzensky

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.

Secondary surge arrester with isolating and indicating features

A spring contact assembly for an electrical switch is disclosed which permits the spring contacts and switch to withstand high close-into-fault current levels without adversely affecting the switch's continuous current rating during normal operation. The spring contact assembly includes a pair of spring contacts supported in opposed relation on a support fork, each spring contact having a symmetrical corrugated surface presenting a plurality of line contact surfaces to a contact bar when the spring contacts are brought into operative engagement with the contact bar, each spring contact further being supported in a manner to bias the corrugated contact surfaces against the contact bar. A protective shield may be provided for each spring contact to protect it from arc erosion.

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Chicago, IL, United States of America

Howard E Swanson