Coordination of Lightning Arresters and Current-Limiting Fuses

When a current-limiting fuse operates to interrupt a high fault current, it must necessarily generate a high resistance quickly to provide current-limiting action. The rapid increase in resistance produces a high arc voltage across the fuse. This arc voltage will normally exceed the peak circuit voltage, with the maximum usually occurring within one millisecond after the fuse melts. At this moment, a large amount of energy may be stored in the circuit inductance. If at that instant, the fuse voltage is sufficient to spark over a lightning arrester, much of the stored energy may be dissipated by the arrester. This can produce a very severe operating duty for the arrester and in some cases cause its destruction. This paper describes the problem and touches upon the variables involved in coordinating arresters and current-limiting fuses.