GE Industrial Solutions AKD-20 Low Voltage Switchgear - Manuel (Page 22)

AKD-20 Low Voltage Switchgear
Chapter 3. Description
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Fig. 3-17. Auxiliary/transition compartments view of top
section
3-10 Bus Area
The bus area, Fig. 3-18, contains the main horizontal bus and
vertical riser bus bars (1) for the particular section. The vertical
bus bars are supported at the breaker run-ins (2) which are
bolted to the molded bases (3) 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.
1 Vertical riser bus
2. Run-ins to breaker compartment
3. Molded base
4. Run-backs from breaker compartment
5. Short-circuit brace
Fig. 3-18. Bus construction
Busing System
Bus bars are fully tin-plated copper with bolted joints and silver
plating is optional. The standard construction is open bus. A
barrier system (Bus compartmentation) that isolates the main
and vertical bus bars from the cable area is available as an
option. 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 Fig. 3-19.
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 Chapter 4 of this publication.
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.
1. Incoming cable connection
2. Isolation barriers
3. Main horizontal bus connections
Fig. 3-19. Main breaker arrangement
1
3
4
2
5
1
2
3