How does the high-speed fuse operate? The four visuals show the sequential stages of the fuse operation that include: normal, pre-arcing, arcing, and operated. The copper strip is an example of the fuse element, and the circles in between are restrictions (also called bridges) that are designed for current flow. During normal conditions, the electric current flows through these element bridges or restrictions, generating heat. The fuse element will continue to carry the current as intended, so long as there is a balance in heat transfer the heat generated equals the heat dissipated. During an overcurrent condition, the element bridges heat up faster than the fuse can dissipate it. The bridges start to melt open and arc. The sand surrounding the fuse elements quickly quenches the arcs, restricting the flow of overcurrent and effectively interrupting the fault condition.