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AKD-20 AR / Entellisys AR Low-voltage Switchgear
Section 3. Switchgear Description
Bus Area
DANGER: Electrical arc flash hazard. Personal
protection equipment required. Turn off power to the
equipment before working inside.
The bus area (Figure 3.21) contains the main horizontal bus
and vertical riser bus bars for the particular section. The
vertical bus bars are supported at the breaker run-ins which
are bolted to the molded bases that form the rear wall of the
breaker compartment. The horizontal bus bars are supported
by the power connectors which are bolted to the vertical bus
bars. All bolted supports and connections are accessible from
the rear for maintenance. The bus area is fully isolated from
the breaker, instrument and auxiliary compartments by the
molded bases or glass polyester sheet.
Busing System
Bus bars are fully tin-plated copper with bolted joints and
silver plating is optional. The standard construction is a
barrier system (Bus Compartmentation) that isolates the main
and vertical bus bars from the cable area. All run-backs
(load-side power conductors) from the breaker compartment
to the cable termination area are covered with non-PVC
insulated tubing.
The typical arrangement is shown in Figure 3.22 and Figure
3.24.
The standard bracing is 65,000 amperes, RMS symmetrical.
Bracing for 100,000, 150,000 and 200,000 amperes, RMS
symmetrical is available as an option.
In general, when the switchgear equipment has no more than
four sections or does not exceed 10 feet in length, it will be
shipped as one complete lineup. In such cases, the only field
assembly would be to a close-coupled transformer if, the
switchgear were part of a Load Center Unit Substation. If,
because of shipping and/or handling considerations, the
equipment cannot be handled in one piece, it can be split into
two or more shipping sections at the factory. The individual
shipping splits require both mechanical and electrical
connections between sections to be made in the field.
At these shipping splits, provisions are made for bolting all
buses and making the necessary electrical and mechanical
connections. These are described in SECTION 4 of this
instruction manual.
On main and tie breakers, the bus area is divided into an
upper and lower section by a glass reinforced polyester
isolation barrier. For typical unit substation main circuit
breakers, the upper section contains the incoming line bus.
The lower section of the bus area contains the load side main
bus (protected by the main breaker) which feeds all sections
of the switchgear equipment. Similarly, barriers at tie
breakers isolate the two main bus sections from each other.
17
Courtesy of NationalSwitchgear.com
Figure 3.21 Bus construction
Vertical Riser Bus
(1)
Run-ins to Breaker Compartment
(2)
Short-circuit Brace
(3)
Run-backs from Breaker Compartment
(4)
Molded Base
(5)
Figure 3.22 Main breaker arrangement
Isolation Barrier
(1)
Incoming Cable Connection
(2)
Main Horizontal Bus
(3)
©2016 General Electric. All rights reserved.
DEH-41473
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