Citadel 2.0 - Instruction Manual - page:
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G E N E R A L C O N S T R U C T I O N
General Construction concept of Citadel vacuum breaker elements
Vacuum circuit breakers consist of a source of mechanical power that in turn operates on an
interrupting medium in this case a vacuum interrupter.
Based on construction needs of the switchgear breaker elements can be fixed mounted or draw-out type.
The Citadel operator mechanism is an energy-storing spring type system with most of the controls
and actuating devices located within the operator mechanism’s enclosure (housing).
Narrow element Citadels (24 inch switchgear type), have primary power pole assemblies that are
fixed to the rear of the operating mechanism housing by a custom three sided molding assembly
that surrounds the vacuum interrupter.
The entire molding is designed to solidly bolt to the rear of the mechanism enclosure. The molded
assembly also provides bolting capabilities to allow primary conductor attachments (runbacks) to the
vacuum interrupter’s upper and lower points of connection These runback bus bars are either hole
punched at their far ends for bolted connections or have movable connectors (which go by more
familiar names of “finger clusters” or “movable primary disconnects”) attached to their far ends for
use in conjunction with its associated draw-out switchgear.
In the case of higher amperage or higher interrupting (36 inch switchgear type) Citadel elements
(3,000 to 5,000 amps; 50kA and 63kA) the pole supports are custom designed stand-off insulators
bolted to metallic heat sink castings. The upper or lower heat sink castings are each designed to
“capture” either their associated vacuum interrupter’s stationary or moving contact assembly side.
See: “Bolt Size and Torque Values” Chart for more detailed hardware and connection information
(pages 107 to 113)
Primary connections (refer to images in page 39)
Item #2 in Figures 12 and 13 illustrates provisions to make up the primary power
connections of a draw-out Citadel. These movable connectors go by more familiar names
such as “finger clusters”, “movable primary disconnects”, “movable primary stabs”. Each
circuit breaker has three upper (one per phase) and three lower (one per phase) primary
disconnect points, providing detachable connections to the main current carrying bus
bars in the switchgear. For fixed mounted circuit breakers, bus bar conductors (or landing
pads) are provided to bolt directly to bus bar.
Inter-Phase barriers (as applicable);
Panels of GPO-3 (red) glass-polyester insulating material are located around the
circuit breaker’s main primary pole assemblies to provide suitable electrical insulation
between the vacuum interrupters and ground plane locations in the cubicle.
