5
the modification or modernization of
old equipment, or the replication of
old equipment under different condi-
tions. The temporary schedule is
required to Correct internal defects
which ordinarily appear in the first
year of service and to correlate
external check procedures with
internal conditions as a basis for more
conservative maintenance program
thereafter. Assuming that a circuit
breaker shows no serious defects at
the early complete inspections and no
heavy interrupting duty is imposed,
the following inspection schedule is
recommended:
old equipment, or the replication of
old equipment under different condi-
tions. The temporary schedule is
required to Correct internal defects
which ordinarily appear in the first
year of service and to correlate
external check procedures with
internal conditions as a basis for more
conservative maintenance program
thereafter. Assuming that a circuit
breaker shows no serious defects at
the early complete inspections and no
heavy interrupting duty is imposed,
the following inspection schedule is
recommended:
6 months after erection
Complete inspection
and adjustment
and adjustment
12 months after
previous inspection
previous inspection
Complete inspection
and adjustment
and adjustment
12 months after
previous inspection
previous inspection
Complete inspection
and adjustment
and adjustment
12 months after
previous inspection
previous inspection
External checks and
inspection; if checks
are satisfactory, no
internal inspection
inspection; if checks
are satisfactory, no
internal inspection
12 months after
previous inspection
previous inspection
Complete inspection
and adjustment
and adjustment
5.1.2. Inspection schedule for existing
breakers.- The inspection schedule
should be based by the interrupting
duty imposed on the breaker. It is
advisable to make a complete internal
inspection after the first severe fault
interruption. If internal conditions are
satisfactory, progressively more fault
interruptions may be allowed before
an internal inspection is made.
Average experience indicates that up
to five fault interruptions are allowable
between inspections on 230 kV and
above circuit breakers, and up to 10
fault interruptions are allowable on cir-
breakers.- The inspection schedule
should be based by the interrupting
duty imposed on the breaker. It is
advisable to make a complete internal
inspection after the first severe fault
interruption. If internal conditions are
satisfactory, progressively more fault
interruptions may be allowed before
an internal inspection is made.
Average experience indicates that up
to five fault interruptions are allowable
between inspections on 230 kV and
above circuit breakers, and up to 10
fault interruptions are allowable on cir-
cuit breakers rated under 230 kV.
Normally, no more than 2 years
should elapse between external in-
spections or 4 years between internal
inspections.
Normally, no more than 2 years
should elapse between external in-
spections or 4 years between internal
inspections.
5.2. EXTERNAL INSPECTION GUIDE-
LINES.- The following items should be
included in an external inspection of a
high-voltage breaker.
LINES.- The following items should be
included in an external inspection of a
high-voltage breaker.
a. Visually inspect PCB externals and
operating mechanism. The tripping
latches should be examined with spe-
cial care since small errors in
adjustments and clearances and
roughness of the latching surfaces
may cause the breaker to fail to latch
properly or increase the force neces-
sary to trip the breaker to such an
extent that electrical tripping will not
always be successful, especially if the
tripping voltage is low. Excessive
"opening" spring pressure can cause
excessive friction at the tripping latch
and should be avoided. Also, some
extra pressure against the tripping
latch may be caused by the electro-
magnetic forces due to flow of heavy
short-circuit currents through the
breaker. Lubrication of the bearing
surfaces of the operating mechanism
should be made as recommended in
the manufacturer's instruction book,
but excessive lubrication should be
avoided as oily surfaces collect dust
and grit and get stiff in cold weather,
resulting in excessive friction.
operating mechanism. The tripping
latches should be examined with spe-
cial care since small errors in
adjustments and clearances and
roughness of the latching surfaces
may cause the breaker to fail to latch
properly or increase the force neces-
sary to trip the breaker to such an
extent that electrical tripping will not
always be successful, especially if the
tripping voltage is low. Excessive
"opening" spring pressure can cause
excessive friction at the tripping latch
and should be avoided. Also, some
extra pressure against the tripping
latch may be caused by the electro-
magnetic forces due to flow of heavy
short-circuit currents through the
breaker. Lubrication of the bearing
surfaces of the operating mechanism
should be made as recommended in
the manufacturer's instruction book,
but excessive lubrication should be
avoided as oily surfaces collect dust
and grit and get stiff in cold weather,
resulting in excessive friction.
b. Check oil dielectric strength and
color for oil breakers. The dielectric
strength must be maintained to pre
vent internal breakdown under voltage
surges and to enable the interrupter
to function properly since its action
color for oil breakers. The dielectric
strength must be maintained to pre
vent internal breakdown under voltage
surges and to enable the interrupter
to function properly since its action
(FIST 3-16 1/92)