Page 18
I.B. 70A2580H02
Effective November 2012
5-3.3 CLOSING OPERATION
Figure 5-2
shows the position of the closing cam and
tripping linkage. Note that in Figure 5-2a
in which the
circuit breaker is open and the closing springs are
discharged, the trip “D” shaft and trip latch are in the
unlatched position.
Once charged, the closing springs can be released to
close the circuit breaker by moving the spring release
latch out of the way. This is done electrically or manually
by depressing the spring release lever, which turns the
spring release latch out of the way of the closing stop
roller. The force of the closing spring rotates the cam
shaft through the spring cranks. The closing cam, being
attached to the cam shaft, in turn rotates the pole shaft
through the main link to close the circuit breaker.
In Figure 5-2c
the linkage is shown with the circuit
breaker in the closed position before the closing springs
have been recharged. Interference of the trip “D” shaft
with the trip latch prevents the linkage from collapsing,
and the circuit breaker is held closed.
Figure 5-2d
shows the circuit breaker in the closed
position after the closing springs have been recharged.
Note that the spring charging rotates the closing cam by
one half turn. Since the cam surface in contact with the
main link roller is cylindrical in this region, the spring
charging operation does not affect the mechanism
linkage.
Since the primary contacts are completely enclosed in
the vacuum interrupter and not adjustable in any way, a
“Slow Close” capability is not provided with VCP-Wind
circuit breakers.
5-3.4 TRIPPING OPERATION
When the trip “D” shaft is turned either by the trip button
or trip coil, all links return to the original “open” condition
shown in Figure 5-2a.
5-4 CONTROL SCHEMES
There are two basic control schemes for 38kV VCP-
Wind
circuit breakers, one for DC control and one for
AC control voltages (Figures 5-4 and 5-5).
There may be
different control voltages or more than one tripping
element, but the principal mode of operation is as
follows:
As soon as the control power is applied, the spring
charging motor automatically starts charging the
closing springs. When the springs are charged, the
motor cut off LS1/bb switch turns the motor off. The
circuit breaker may be closed by making the control
switch close (CS/C) contact. Automatically upon
closing of the circuit breaker, the motor starts charging
the closing springs. The circuit breaker may be
tripped any time by making the control switch trip
(CS/T) contact.
Note the position switch (PS 1) contact in the spring
release circuit in the scheme. This contact remains
made while the circuit breaker is being levered
between the TEST and CONNECT positions.
Consequently, it prevents the circuit breaker from
closing automatically, even though the control close
contact (CS/C) may have been made while the circuit
breaker is levered to the CONNECT position.
The position switch (PS2) contact is in the motor
circuit. It prevents the motor from starting until the fully
CONNECT position is reached and the secondary
contacts are firmly engaged.
When the CS/C contact is made, the SR closes the
circuit breaker. If the CS/C contact is maintained after
the circuit breaker closes, the Y relay is picked up.
The Y/a contact seals in Y until CS/C is opened. The
Y/b contact opens the SR circuit, so that even though
the circuit breaker would subsequently open, it could
not be reclosed before CS/C was released and
remade. This is the anti-pump function.
5-4.1 TIMING
The opening and closing times for the circuit breakers
vary depending upon the control voltage and the power
rating. Maximum values for 38kV VCP-Wind circuit
breakers are shown in Table
5.1.
5-4.2 SECONDARY DISCONNECTS
The VCP-Wind drawout circuit breaker control wiring
is arranged to connect two standard 30 point male
plugs with corresponding switchgear compartment
mounted female plugs.
Drawout circuit breakers utilize fixed mounted male
plugs located on the top left portion of the circuit
breaker. The two 30 point plugs are mounted in a
side-by-side arrangement (Figure 5-6).