7
Table I - Maximum Contact Resistance
Air circuit breakers Oil circuit breakers
kV
Amperes
Microhms
kV
Amperes
Microhms
5-15
600
1200
2000
2000
100
50
50
50
7.2-15
600
1200
2000
4000
2000
4000
300
150
150
75
40
40
23-24
46
69
69
All
All
All
600
1200
2000
2000
500
700
500
500
100
700
500
500
100
115-230
All
800
h. Measure contact resistance. As
long as no foreign material is present,
the contact resistance of high-pres-
sure, butt-type contacts is practically
independent of surface condition.
Nevertheless, measurement of the
electrical resistance between external
bushing terminals of each pole may
be regarded as the final "proof of the
pudding." Any abnormal increase in
the resistance of this circuit may be
an indication of foreign material in
contacts, contact loose in support,
loose jumper, or loose bushing
connection. Any one of these may
cause localized heating and
deterioration. The amount of heat
above normal may be readily
calculated from the increase in
resistance and the current.
long as no foreign material is present,
the contact resistance of high-pres-
sure, butt-type contacts is practically
independent of surface condition.
Nevertheless, measurement of the
electrical resistance between external
bushing terminals of each pole may
be regarded as the final "proof of the
pudding." Any abnormal increase in
the resistance of this circuit may be
an indication of foreign material in
contacts, contact loose in support,
loose jumper, or loose bushing
connection. Any one of these may
cause localized heating and
deterioration. The amount of heat
above normal may be readily
calculated from the increase in
resistance and the current.
Resistance of the main contact cir-
cuits can be most conveniently
measured with a portable double
bridge (Kelvin) or a "Ducter." The
breaker contacts should not be
opened during this test because of
possible damage to the test equip-
ment.
cuits can be most conveniently
measured with a portable double
bridge (Kelvin) or a "Ducter." The
breaker contacts should not be
opened during this test because of
possible damage to the test equip-
ment.
resistances for typical classes of
breakers.
breakers.
I. Make time-travel or motion-analyzer
records. Circuit breaker motion an-
alyzers are portable devices designed
to monitor the operation of power
circuit breakers which permit
mechanical coupling of the motion an-
alyzer to the circuit breaker operating
rod. These include high-voltage and
extra- high-voltage dead tank and SF
records. Circuit breaker motion an-
alyzers are portable devices designed
to monitor the operation of power
circuit breakers which permit
mechanical coupling of the motion an-
alyzer to the circuit breaker operating
rod. These include high-voltage and
extra- high-voltage dead tank and SF
6
breakers and low-voltage air and vac-
uum circuit breakers. Motion
analyzers can provide graphic records
of close or open initiation signals,
contact closing or opening time with
respect to initiation signals, contact
movement and velocity, and contact
bounce or rebound. The records
obtained not only indicated when
mechanical difficulties are present but
also help isolate the cause of the
difficulties. It is preferable to obtain a
motion-analyzer record on a breaker
when it is first installed. This will
provide a master record which can be
filed and used for comparison with
future maintenance checks. Tripping
and closing voltages should be re-
corded on the master record so
subsequent tests can be performed
under comparable conditions.
uum circuit breakers. Motion
analyzers can provide graphic records
of close or open initiation signals,
contact closing or opening time with
respect to initiation signals, contact
movement and velocity, and contact
bounce or rebound. The records
obtained not only indicated when
mechanical difficulties are present but
also help isolate the cause of the
difficulties. It is preferable to obtain a
motion-analyzer record on a breaker
when it is first installed. This will
provide a master record which can be
filed and used for comparison with
future maintenance checks. Tripping
and closing voltages should be re-
corded on the master record so
subsequent tests can be performed
under comparable conditions.
(FIST 3-16 1/92)