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Siemens 38-3AH3 38 kV Instruction Manual page 49

Vacuum circuit breaker
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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 curve shown in Figure 41: Typical
vacuum interrupter contact curve on page
48 is offered as a guide to life expectancy.
Maintenance
Vacuum-interrupter mechanical check
Refer to Figure 42: Lower pole support
with insulated coupler, Figure 43: Primary
contact CLOSED and insulated coupler
DISCONNECTED and Figure 44: CLOSED
primary contact forced OPEN by manual
pressure on page 49, Figure 45: Contact-
resistance test of the primary contacts on
page 52 and Figure 46: 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 42: 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 43: 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 44: 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).
48.6
48.0
Figure 42: Lower pole support with
insulated coupler
48.6
48.0
Figure 43: Primary contact CLOSED and
insulated coupler DISCONNECTED
Figure 44: CLOSED primary contact
forced OPEN by manual pressure
49

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