Advertisement
PowerVac
5kV Vertical Lift
®
Chapter 4. Installation
4-6 Stationary Auxiliary Switch
(MOC)
The Stationary Auxiliary Switch is a Mechanism
Operated Contact (MOC) which is an optional
switch mounted in the switchgear cell. When
the breaker has been elevated to the fully con-
nected position, the MOC switch will be actu-
ated whenever the breaker is closed. The MOC
switch is actuated by the plunger mounted on
the top of the breaker mechanism. (Figure 10
Item 1). The MOC switch has a number of "a"
contacts (closed when the breaker is closed and
open when the breaker is open) and "b" con-
tacts (open when the breaker is closed and
closed when the breaker is open).
The following paragraph defines the essential
dimensions relating to the interfacing elements
of the beaker and switchgear, to assure reliable
performance.
The following elements are important factors
which commonly affect the operation of the sta-
tionary auxiliary switch.
Figure 10. MOC switch
Courtesy of NationalSwitchgear.com
1. Plunger travel on the breaker.
2. The gap between the top of the plunger
3. Variations between breakers in the distance
4. Variations in the rotation requirements to
5. Condition of the plunger interlock compo-
6. Elevating mechanism limit switch consis-
7. Break elevating mechanism positive stops.
8. Seismic events.
Some of these elements also affect the other
important interfaces required for reliable opera-
tion of the equipment, such as:
1. Primary disconnect penetration.
2. Secondary coupler penetration.
3. The positive interlock mechanism.
A major goal in the design of switchgear has
always been the interchangeability of breakers.
GE Switchgear has been very successful in
achieving that goal for many years. Analysis of
instruction book adjustments, shop tolerances,
and service advice letters issued in recent years,
however, have demonstrated that tolerances in
switchgear equipment installed and presently
1. Adjustment
operating can result in situations where it is
washer
impossible to meet all adjustments or that an
adjustment is brought into specification and it
2. Operating
causes a problem with another interface.
switch rod
4-7 Stops
3. Plunger
interlock
The stop pins and stop bolts on the elevating
mechanism are emergency mechanical stops
which would come into use only if the upper
elevating motor switch is completely out of ad-
justment or has failed. Elevating against these
stops may be quite audible and the operator
should release the clutch handle immediately,
de-energizing the elevating motor circuit or the
elevating motor circuit protective fuse will open
to protect the motor. The stop bolts should be
set to 3/32" to 1/8" clearance and only changed
or reset after all other elevating adjustments are
made and verified. Figure 6 and 53.
4-8 Ground
A visual check should be made to observe the
ground connection. The ground shoe on the
moveable breaker is designed to have a nomi-
nal engagement of 1-1/2" +1/4" vertically with
the steel and copper spring loaded disconnects
of the ground device in the switchgear.
16
on the breaker and the bottom of the rod
on the stationary auxiliary switch mecha-
nism.
from the underside of the lift rail and the
top of the plunger.
"make" and "break" the stationary auxil-
iary switch contacts.
nents on the breaker.
tency.
Advertisement
