Siemens GMSG Instruction Manual page 34

Vacuum interrupter/operator
Trip-latch lever
Trip-pushrod cam
Enclosure rear
Interlock levers
Figure 31: Closed circuit breaker interlock mechanism in stored-energy mechanism
34
Close-latch lever
Closing-spring release cam
Normal operating position
Trip-free pushrod
Retaining rings
Spring-dump tube
Figure 29: Circuit breaker
compartment up to 50 kA shown on
page 30 shows the racking
mechanism located on the floor in
the center of the circuit breaker
compartment. Note the two "wing-
like" elements that project from the
right side of the racking mechanism.
The CLOSED circuit breaker interlock
plunger, when down (circuit breaker
CLOSED), falls behind the front wing
in the TEST position and behind the
rear wing in the CONNECT position.
The wings are coupled to the
element of the racking mechanism
that shrouds the racking screw. This
shroud must be moved rearward to
insert the racking-crank socket in
order to engage the racking shaft.
With the plunger down (circuit
breaker CLOSED), the wings and
shroud cannot be moved and thus
racking is blocked.
B. Trip-free interlock
Figure 28: Circuit breaker interlocks
and ground disconnect on page 29
shows the automatic closing spring
energy released (spring dump) and
trip-free interlock. This interlock is a
plunger with a roller on the lower
end. The plunger roller tracks the
shape of the cam profiles on the
racking mechanism in the
switchgear (refer to Figure 29:
Circuit breaker compartment up to
50 kA shown on page 30).
The spring dump cam profile on the
racking mechanism raises the spring
dump/trip-free interlock upon
insertion of the circuit breaker into
the compartment, or upon
withdrawal from the compartment.
The interlock is raised at about the
time the front wheels pass over the
cubicle sill. It allows the spring dump
interlock to be in the reset (lowest)
position at all other times.
The trip-free cam profile on the
racking mechanism allows the
spring dump/trip-free racking
interlock to be in the lowest position
(reset) only when the circuit breaker
is in the TEST or the CONNECT
position. Thus, during racking, the
trip-free/spring dump interlock is
held in an elevated condition except
when the circuit breaker reaches the
TEST or the CONNECT position. The
circuit breaker can be closed only
when the interlock position is down,
and will trip if the plunger is
moved up.