Figure 4-30. - Mounted distribution cutout with expulsion fuse.

Figure 4-31. - Distribution cutouts installed for transformer bank switching.

transformers, capacitors, cable circuits, and sectionalizing points on overhead circuits (fig. 4-31). Enclosed, open, and open-link cutouts are used for different distribution circuit applications. Cutouts normally use an expulsion fuse. An expulsion fuse operates to isolate a fault or overload from a circuit. The arc from the fault current erodes the fuse holder tube producing a gas that blasts the arc out through the fuse tube vent(s) thereby isolating the circuit.

The mechanical differences between enclosed, open, and open-link cutouts are in their external appearance and methods of operation. Enclosed cutouts have terminals, fuse clips, and fuse holders mounted completely within an insulating enclosure. Open cutouts, as the name indicates, have these parts completely exposed.

The construction of the cutout fuse holder can pro- vide for non-dropout or dropout operation. Some of the fuses are manufactured to provide indication that the fuse is blown; other fuses may have an expendable cap.

ENCLOSED DISTRIBUTION CUTOUT. - In an enclosed distribution fuse cutout the fuse clips and fuse holder are mounted completely within an enclosure. A typical enclosed cutout, as shown in figure 4-32, has a porcelain housing and a hinged door supporting the fuse holder. The fuse holder is a hollow vulcanized-fiber expulsion tube. The fuse link is placed inside the tube and connects with the upper and lower line terminals when the door is closed. When the

Figure 4-32. - Enclosed primary cutout assembly.