(1) Opens in drop. The term drop wire refers to a covered twisted pair or parallel twin wires
that run between the premises on which the substation is located, and the cable terminal, or to an open
wire lead nearest the premises and on a public highway. An open in a drop wire can rarely be located by
visual inspection. If possible, loosen the drop wire at the building and drop it to ground level. Because
the drop wire is still connected to the line or cable pair, test along the wire until the fault is located. If
this cannot be done, remove the drop wire from the building and take it to the foot of the pole. Another
method is to remove the drop wire from the pole or cable terminal and draw it to the building. Connect
the ends of the drop wire to another working circuit on the premises, If one is available, and locate the
fault by testing. To locate an open use the procedure in (2) and (3) below.
(2) Opens in bridle wire runs. The term bridle wire run refers to a wire run that is located on
fences or buildings and is supported by rings placed at intervals along the fence or building, which is
located between a cable terminal and the substation location. Bridle wire, because of its lack of tensile
strength, is not designed for spans of more than a few feet. When testing for an open, start at the cable
terminal and test at intervals until the open is located.
(3) Opens in inside wire runs. The term inside wire run refers to the wires that run between
the station protector or connecting terminal at which the outside and inside wires meet and the
substation. Start at the protector or terminal and test at intervals until the open is located.
a. Causes. Shorts commonly are caused by the following--
(1) A drop or bridle wire swinging or rubbing against an object repeatedly, thus damaging or
removing the insulation so that the bared conductors or the pair come into electrical contact. If the
contact is permanent, the condition is referred to as a short. If the contact makes and breaks
intermittently, it is referred to as a swinging short.
(2) A break in the insulation of a drop wire at the drop clamp, with the clamp serving as the
connection between the two conductors.
(3) Water settling on an old deteriorated drop wire and acting as a conductor.
(4) Dirty faceplates on terminal cans that serve as a conductor between two lugs.