24
3 . s w I TC h G e a r D e s C r I p T I o N
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. 3.22
on the next page.
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 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. 3.22
—
Fig. 3.22
Main breaker
arrangement
2
1
3
