A forced-fusion fuse has a casing, a heat generating material within the casing, a resistance wire for inducing a heat generation reaction to occur in the heat generating material, and a fusion member that is fused by the generation of heat from the heat generating material. When some damage or other has been caused to a wire harness or there is the fear that an impairment will occur therein as when the wire harness has been slight short-circuited, some abnormality or other has occurred in a load connected to the wire harness, or an automobile has collided with another automobile, the sensor unit senses this to thereby output an abnormality detection signal. A controller, upon receipt of the abnormality detection signal, causes the generation of heat in the resistance wire of the forced-fusion fuse. A heat generation reaction is induced, by the generation of heat in the resistance wire, to occur in the heat generating material, whereby the fusion member is fused by the heat generated from the heat generating material.