8
Time-travel records are taken on the
pole nearest the operating mecha-
nism to avoid the inconsistencies due
to linkage vibration and slack in the
remote phases.
pole nearest the operating mecha-
nism to avoid the inconsistencies due
to linkage vibration and slack in the
remote phases.
5.3. INTERNAL INSPECTION GUIDE-
LINES.- An internal inspection should
include all items listed for an external
inspection, plus the breaker tanks or
contact heads should be opened and the
contacts nd interrupting parts should be
inspected. These guidelines are not
intended to be a complete list of breaker
maintenance but are intended to provide
an idea of the scope of each inspection.
LINES.- An internal inspection should
include all items listed for an external
inspection, plus the breaker tanks or
contact heads should be opened and the
contacts nd interrupting parts should be
inspected. These guidelines are not
intended to be a complete list of breaker
maintenance but are intended to provide
an idea of the scope of each inspection.
A specific checklist should be developed
in the field for each type of inspection for
each circuit breaker maintained.
in the field for each type of inspection for
each circuit breaker maintained.
5.4. TYPICAL INTERNAL BREAKER
PROBLEMS.- The following difficulties
should be looked for during internal
breaker inspections:
PROBLEMS.- The following difficulties
should be looked for during internal
breaker inspections:
a. Tendency for keys, bolts (espe-
cially fiber), cotter pins, etc, to come
loose.
cially fiber), cotter pins, etc, to come
loose.
b. Tendency for wood operating rods,
supports, or guides to come loose
from clamps or mountings.
supports, or guides to come loose
from clamps or mountings.
c. Tendency for carbon or sludge to
form and accumulate in interrupter or
on bushings.
form and accumulate in interrupter or
on bushings.
d. Tendency for interrupter to flash
over and rupture static shield or resis-
tor.
over and rupture static shield or resis-
tor.
e. Tendency for interrupter parts or
barriers to burn or erode.
barriers to burn or erode.
f. Tendency for bushing gaskets to
leak moisture into breaker insulating
material.
leak moisture into breaker insulating
material.
Fortunately, these difficulties are most
likely to appear early in the use of a
breaker and would be disclosed by the
early internal inspections. As unsatis-
factory internal conditions are corrected
and after one or two inspections show the
internal conditions to be satisfactory, the
frequency of internal inspections may
safely be decreased.
likely to appear early in the use of a
breaker and would be disclosed by the
early internal inspections. As unsatis-
factory internal conditions are corrected
and after one or two inspections show the
internal conditions to be satisfactory, the
frequency of internal inspections may
safely be decreased.
5.5.
I N F L U E N C E O F D U T Y
IMPOSED.-
IMPOSED.-
5.5.1. Influence of light duty.- Internal
inspection of a circuit breaker which
has had no interruption duty or
switching since the previous
inspection will not be particularly
beneficial although it will not be a total
loss. If the breaker has been
energized, but open, erosion in the
form or irregular grooves (called
tracking) on the inner surface of the
interrupter or shields may appear due
to electrostatic charging current. This
is usually aggravated by a deposit of
carbon sludge which has previously
been generated by some interrupting
operation. If the breaker has
remained closed and carrying current,
evidence of heating of the contacts
may be found if the contact surfaces
were not clean, have oxidized, or if
the contact pressure was improper.
Any shrinkage and loosening of wood
or fiber parts (due to loss of absorbed
moisture into the dry oil) will take
place following erection, whether the
breaker is operated or not.
Mechanical operation, however, will
make any loosening more evident. It
is worthwhile to deliberately impose
several switching operations on the
breaker before inspection if possible.
If this is impossible, some additional
inspection of a circuit breaker which
has had no interruption duty or
switching since the previous
inspection will not be particularly
beneficial although it will not be a total
loss. If the breaker has been
energized, but open, erosion in the
form or irregular grooves (called
tracking) on the inner surface of the
interrupter or shields may appear due
to electrostatic charging current. This
is usually aggravated by a deposit of
carbon sludge which has previously
been generated by some interrupting
operation. If the breaker has
remained closed and carrying current,
evidence of heating of the contacts
may be found if the contact surfaces
were not clean, have oxidized, or if
the contact pressure was improper.
Any shrinkage and loosening of wood
or fiber parts (due to loss of absorbed
moisture into the dry oil) will take
place following erection, whether the
breaker is operated or not.
Mechanical operation, however, will
make any loosening more evident. It
is worthwhile to deliberately impose
several switching operations on the
breaker before inspection if possible.
If this is impossible, some additional
(FIST 3-16 1/92)