Figure 4-30.Mounted distribution cutout with expulsion
Figure 4-31.Distribution cutouts installed for transformer
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
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.