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Electrical close and trip check
(control power required)
A check of the circuit breaker control circuits
is performed while the unit is still connected
to the switchgear by the split- plug jumper.
This check is made with the circuit breaker
energized by control power from the
switchgear.
1. Once the circuit breaker springs are
charged, move the switchgear-mounted
close/trip switch to the close position.
There should be both the sound of the
circuit breaker closing and indication the
circuit breaker contacts are CLOSED by the
main contact status indicator.
2. As soon as the circuit breaker has closed,
the automatic spring-charging process is
repeated.
3. After a satisfactory close operation is
verified, move the switchgear-mounted
close/trip switch to the trip position, or
send a trip command from a protective
relay. Verify by both sound and contact
position that the contacts are open.
Completion of these checks demonstrates
satisfactory operation of auxiliary
switches, internal protective relays and
solenoids.
Spring-charging motor checks
No additional checks of the spring-charging
motor are necessary.
Vacuum interrupter
The life expectancy of a vacuum interrupter is
a function of the number of interruptions and
magnitude of current interrupted.
A vacuum interrupter must also be replaced
at 10,000 mechanical operations or when the
contacts have been eroded beyond allowed
limits.
Vacuum interrupter replacement procedures
are detailed in the following maintenance
instructions.
The curves shown in Figures 37: Typical
vacuum interrupter contact life curves
beginning on page 45 are offered as a guide
to life expectancy. Table 3: Typical vacuum
interrupter contact life and stroke on page 44.
Vacuum-interrupter mechanical check
Refer to Figure 38: Lower pole support with
insulated coupler, Figure 39: Primary contact
closed and insulated coupler disconnected
and Figure 40: Closed primary contact forced
open by manual pressure, Figure 41: Contact-
resistance test of the primary contacts on
page 52 and Figure 42: Vacuum interrupter
replacement illustration on page 56.
Before putting the circuit breaker into service,
or if a vacuum interrupter is suspected of
leaking as a result of mechanical damage,
perform a vacuum-integrity check either
mechanically as described in this section, or
alternatively, electrically using a high-
potential test set as described in the next
section.
Open and isolate the circuit breaker and
detach the insulated coupler (48.0) from
lever (48.6) (refer to Figure 38: Lower pole
support with insulated coupler).
The atmospheric pressure will force the
moving contact of a hermetically-sealed
interrupter into the CLOSED position, causing
lever (48.6) to move into the position shown
in Figure 39: Primary contact closed and
insulated coupler disconnected.
A vacuum interrupter may be assumed to be
intact if it shows the following characteristics:
1. An appreciable closing force has to be
overcome when lever (48.6) is moved to
the OPEN position by hand (refer to Figure
40: Closed primary contact forced open
by manual pressure).
2. When the lever is released, it must
automatically return to the CLOSED
position with an audible sound as the
contacts touch.
After vacuum-integrity check, reconnect the
lever (48.6) to the insulated coupler (48.0).
48.0
48.0
Insulated coupler
48.6
Lever
Figure 38: Lower pole support with
insulated coupler
48.0
48.0
Insulated coupler
48.6
Lever
Figure 39: Primary contact closed
and insulated coupler disconnected
Figure 40: Closed primary contact
forced open by manual pressure
48.6
48.6
49
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