Quantcast Fuse maintenance

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TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
c. Replacing fuses on capacitor installations.
(4) Check fo r any missing or damaged hard-
Fuses used on capacitors should not be removed or
ware, such as nuts, bolts, washers, and pins.
replaced by hand, unless due precautions are taken
(5) Clean and polish contact surfaces of clips
beforehand to discharge and ground the capacitors
and ferrules that are corroded or oxidized.
in accordance with chapter 13, section II. The entire
(6) Tighten all 1 oose connections and check to
capacitor bank should be disconnected and
see if the fuse clips exert sufficient pressure to
grounded while replacing the fuses, unless the fuse
maintain good contact.
link or its mounting, or both, can be removed safely
(7) Fuses that show signs of deterioration, such
and completely from the circuit using hot line tools.
as loose connections, discoloration, or damaged cas-
d. Replacing of vented fuses. Vented fuses being
ing should normally be replaced.
replaced within this venting area should be
deenergized during replacement. Vented fuses, op-
b. Periodic inspection of fuse links in distribution
erable from outside their vented area, may be re-
cutouts. These fuse links may require periodic in-
placed without deenergizing the circuit, but the use
spections, since corrosion of the lower terminal of
of hearing protectors is recommended.
the fuse link (generally a flexible cable) at the lower
e. Replacing of current-limiting nonvented type.
open-end of the fuse holder may cause breakage or
Careless handling of these inherently fragile fuses
melting at this point, rather than in the current-
may result in damage. When damage is suspected,
responsive element. Link-break cutouts are particu-
the fuse should not be used.
larly susceptible since their link-break mechanisms
f. Expendable cap cutouts. Do not install a
impose a mechanical strain on fuses.
nonexpendable cap on an expendable cap cutout
c. Inspection of distribution oil fuse cutouts. In
because of the resulting reduction of the expendable
addition to applicable general inspection require-
cap cutout's interrupting capability.
ments, the following items should be included:
8-8. Fuse maintenance.
(1) Sample insulating oil periodically and test
for dielectric breakdown strength. Cutouts that ex-
The frequency of fuse inspection and maintenance
must be determined based on the environmental
perience regular load-break or fuse-interrupting
conditions at the fuse location. Periodically inspect
duty should have their oil tested on a more frequent
fuses which have not blown after a long period of
time to guard against oxidation. Contact clips and
(2) Nonvented distribution oil fuse cutouts gen-
ferrules (fuse terminals) can be covered with a spe-
erally incorporate insulating materials in the fuse
cial noncorrosive conductive lubricant. Before fuses
carriers that may be damaged dielectrically by ex-
are removed or installed, the fuse holders must be
cessive exposure to moisture or to a humid atmo-
disconnected from the power source.
sphere. Keep the cutout sealed so that components
a. Fuses in general. The following procedures
and oil are protected from any contaminating expo-
should be standard for all fuses:
(1) Inspect the fuse unit and renewable ele-
(3) Fuse elements are generally not inter-
ment (if the fuse is a renewable type) for corrosion,
changeable, and any substitution for the manufac-
tracking, and dirt. Replace those units that indicate
turer's fuses may seriously affect the interrupting
deteriorated condition.
characteristics of the device.
(2) Inspect fuse holder insulators for dirt, dust,
salt deposit, and the like, which can cause flashover.
(4) Examine cutouts for any evidence of oil
Also look for cracks or burn marks on insulators.
leakage, and maintain the prescribed oil level.
(3) For vented expulsion-type fuses, inspect the
(5) Check moveable bearing gasket surfaces,
seal on the expulsion chamber to ensure that no
yoke compression, and interlocking features for sat-
moisture has entered the interrupting chamber of
isfactory operation.
the fuse.
8-9. Switch usage.
some predetermined current overload. This function
is provided by a fuse in series with a switch.
Switches are used to open or close circuits that may
a. Operation. Switches can be controlled manu-
or may not be energized. If used for opening ener-
ally by the lineman at the switch location, or by
gized circuits, the switch contact construction must
control signals (initiated either manually or auto-
be capable of interrupting the current flow.
matically) to operate electric, hydraulic, or pneu-
Switches do not open the circuit automatically on


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