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Circuit Breaker Position
Circuit Breaker Ground Connection
A sliding contact multiple finger assembly for grounding the
circuit breaker frame is mounted underneath the breaker truck
frame, as shown in Figure 34. This assembly engages the
ground bar mounted in the cell and maintains a solid ground
contact with a continuous wipe through all positions. The contact
is broken when the breaker passes the DISCONNECT position
while being removed from the cell.
Shutter Operation
Two shutter operating levers, one on each side of the breaker
cell, are driven down by the engagement of the wheels on the
circuit breaker frame. This opens the shutters as the circuit
breaker is moved into the CONNECT position and allows the
shutters to close when the circuit breaker is withdrawn. The
shutters are fully closed with the breaker in the TEST position.
Figure 35. MOC and TOC Switches (cover removed for photo)
38
Courtesy of NationalSwitchgear.com
Breaker Installation and Removal
Type GMI Vacuum Circuit Breakers are normally shipped
installed in the switchgear cells. They are normally shipped with
their primary contacts open and the closing springs discharged.
However, before racking of a circuit breaker or performing any
inspection or maintenance, verify that the circuit breaker is
open with closing springs discharged. Refer to instruction
manual SG-3268 for information on installation, maintenance,
and handling of these circuit breakers.
De-Energizing Control Power to Circuit Breaker
Locate the control power disconnect device associated with
the circuit breaker. This disconnect (typically, a pullout type
fuse holder) is normally located on the secondary device panel
inside the circuit breaker cell. Removal of the fuse holder de-
energizes control power to the circuit breaker in the respective
switchgear cell. In some switchgear assemblies, a molded
case circuit breaker is used in lieu of the pullout type fuse
TOC
holder. Opening this circuit breaker accomplishes the same
Switch
result: control power is disconnected.
Actuator
Spring Discharge Check
TOC
Perform the Spring Discharge Check before inserting or
Switch
removing the circuit breaker from the switchgear. Refer to
Connections
Figure 36.
The spring discharge check consists of simply performing the
following tasks in the order given. This check assures that
both the tripping and closing springs are fully discharged.
MOC
Switch
Connections
Figure 36. Front Panel Controls of GMI Circuit Breaker
MOC
Switch
Actuator
1595-95
Open-Closed
Indicator
Charged-
Discharged
Indicator
Manual
Close
Manual
Trip
1574-95
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