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Figure 3: Use of extension rails for
removal of circuit breaker not at floor level
shows the two extension rails inserted
into the fixed rails within the cell. The rails
engage locking pins in the fixed rails to
secure them in position. The photo shows
use of the extension rails in a lower cell
installed above floor level. The procedure
is similar for an upper circuit breaker cell.
5. Depress and hold down the circuit breaker
racking latch release handle and pull the
circuit breaker out from the DISCONNECT
position. The circuit breaker can now be
removed from the cubicle and rolled out
onto the two extension rails.
6. Remove the circuit breaker from the two
extension rails using the approved
Siemens circuit breaker lifting device or
Siemens lifting sling and a suitable crane.
7. Lift the two extension rails and withdraw
them from the switchgear.
8. For arc-resistant type GM-SG-AR
switchgear, return the covers that allow
the circuit breaker to roll out of the cell to
their original position. Close the circuit
breaker compartment door and secure all
latches.
Type GMSG vacuum circuit breakers weigh
between 430 and 930 lbs (195-422 kg)
depending upon ratings. The circuit breaker
can be moved using a properly rated crane
and lift sling. A lift sling can be attached to
the circuit breaker, and then used to hoist the
circuit breaker vertically clear of the extension
rails. When clear, remove the rails and lower
the circuit breaker to the floor.
Heavy weight.
Can result in death, serious injury or property damage.
Do not transport a circuit breaker using a lift truck with the lift truck in
the raised position.
Racking crank engagement procedure
A crank for racking the circuit breaker is
provided as a standard accessory. Racking a
circuit breaker can be accomplished with the
drawout compartment front door open (for
type GM-SG non-arc-resistant switchgear) or
through a small opening (or window) in the
front door, with the door closed.
The racking crank consists of an offset handle
with a custom socket assembly welded to the
end. The socket end of the crank is designed
to engage the shoulder of the racking-
mechanism shaft and remain engaged during
racking with spring plungers. The plungers
operate in a manner similar to the retainers of
an ordinary mechanic's socket wrench.
The portion of the racking-mechanism shaft
visible is cylindrical, and the shoulder of the
racking-mechanism shaft is hidden by a
shroud until the engagement procedure
starts. The square socket-end of the crank will
only engage the shoulder of the shaft if it is
aligned properly.
The suggested procedure to engage the
racking mechanism is as follows:
1. The circuit breaker must be OPEN. (The
racking shroud cannot be moved if the
circuit breaker is CLOSED.)
Figure 2: Type GMSG vacuum circuit
breaker racking
Figure 3: Use of extension rails for
removal of circuit breaker not at
floor level
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