Quantcast Section V- Miscellaneous Devices

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
 
  
 


TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
Table 8-2. Troubleshooting chart for power circuit breakers (continued)
Remedy
Trouble
Cause
(4) Adjust operation of the cutoff switch to
(4) Cutoff switch operating too soon.
delay cutoff so as to allow the circuit breaker
to close fully.
(5) Cutoff switch operating too late, causing
(5) Readjust to reduce power at the end of the
the circuit breaker to bounce open.
stroke, and eliminate bounce.
(6) Insufficient control voltage (of an electri-
(6) Provide the following:
Failure to close or to latch closed
(a) Install larger wires; improve contacts at
cally operated circuit breaker) caused by:
(con't)
(a) Too much drop in leads
connections.
(b) On ac control-poor regulation.
(b) Install larger control transformer. Check
(c) On dc control-battery not fully charged
rectifier, and be sure it is delivering adequate
or in poor condition.
dc voltage from adequate ac supply.
(c) Give battery a sustaining charge, or re-
pair according to instructions by the battery
manufacturer.
(7) Blown fuse in control circuit, faulty con-
(7) Replace blown fuse; repair faulty connec-
tion or broken wire; dress or replace damaged
nection or broken wire in control circuit,
damaged or dirty contacts on control switch
contacts or clean dirty contacts in control
(electrically operated circuit breaker)
switch.
Section V-MISCELLANEOUS DEVICES
8-18. Circuit switchers.
a. Operation. Keep a record of counter readings,
settings, and sequence of operation, in addition to
Circuit switchers employ SF, puffer-type interrupt-
normal maintenance and test data.
ers for switching and protection of transformers,
(1) Reclosing after operation to lockout. First
lines, cables, and capacitor banks, and have fault-
make a complete visual inspection of the recloser for
interrupting ratings suitable for use in protecting
evidence of external damage, such as broken or
medium- to heavily-loaded transformers. They are
cracked bushings, or thrown oil. Only after inspec-
used for voltage levels of 34.5 kv and up as an
tion indicates that everything is in order and there
intermediate protective step between less costly
is positive evidence that the fault has been removed
fused switch combinations and more expensive cir-
may the unit be closed again.
cuit breakers. Models are available with and with-
(2) Cold-load pickup. Excessive currents can
out integral disconnect switches. Operation of cir-
occur on circuit re-energization and cause operation
cuit switchers is initiated by manually operating
of the recloser to lockout. Such currents should be
the switch; by remote supervisory control equip-
eliminated by following specific operating instruc-
ment; or by relays that automatically sense prede-
tions provided dependent upon the cause of the ex-
termined system or equipment conditions or electri-
cessive current.
cal failures (faults). Maintenance should use the
(a) Inrush currents associated with motor
appropriate requirements for switches and SF, in-
starting, transformers, and the like can cause exces-
terrupters.
sive currents. The duration of this component of
cold-load pickup is quite short, a matter of several
8-19. Automatic circuit reclosers.
cycles.
Automatic circuit reclosers are self-contained de-
(b) An increase in the load values relative to
vices for interrupting and automatically reclosing
the previous load values due to loss of diversity of
an alternating current circuit during the fault con-
cycling loads (electric heating, air conditioners) can
cause excessive currents. The ratio of the post inter-
ditions. Reclosers are provided with a predeter-
ruption load to pre-interruption load varies with the
mined sequence of opening and reclosing, followed
length of interruption, but can be as high as two.
by resetting, hold closed, or lockout. They can be
This effect may cause excessive currents to persist
used on single-phase or three-phase circuits. Some
for tens of minutes.
circuit breakers are provided with reclosing relays
(c) Where cold loads cannot be picked up,
and other devices, which act in the same manner as
circuits may be sectionalized to disconnect part of
automatic circuit reclosers. Reclosers may be insu-
the load, or reclosers may be bypassed temporarily.
lated with oil or operate with vacuum or SF, gas
Nonseries coil reclosers may have special control
bottles, similar to circuit breakers. They may be
provisions to allow for the inrush component of cold-
magnetically or electronically operated:
8-14





 


Privacy Statement - Copyright Information. - Contact Us

Integrated Publishing, Inc.