Figure 4-33 shows an open types of distribution cutout being closed. Distribution cutouts are used with installations of transformers, capacitors, cable circuits, and sectionalizing points on overhead circuits.
An enclosed distribution fuse cutout is one in which the fuse clips and fuse holder are mounted completely within an enclosure (fig. 4-34, view A). A typical enclosed cutout 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 fuse blows or melts because of excessive current passing through it, the resultant arc attacks the walls of the fiber tube, producing a gas that blows out the arc. The melting of the fusible element of some cutouts causes the door to drop open, signaling to the lineman that the fuse has blown.
Cutout This type of cutout differs from the open cutout in that it does not use the fiber expulsion tube (fig. 4-34, view B). The fuse link is supported by spring terminal contacts. An arc-confining tube surrounds the fusible element of the link. During fault clearing, the spring contacts provide link separation and arc stretching. The arc-confining tube is incorporated as part of the fuse link.
Open cutouts are similar to the enclosed types, except that the housing is omitted (fig. 4-34, view C). The open type is made for 100- or 200-amp operation. Some cutouts can be up rated from 100 to 200 amps by using a fuse tube rated for 200-amp operation.
Figure 4-33. - Distribution cutout.Continue Reading