type built on a suitable framework of structural steel, or by an equivalent
approved method, which shall provide a self-supporting and stable
structure. Metal-enclosed switchgear construction consisting of ribbed
side sheets and fabricated framework which is functionally equivalent to
the structural steel framework specified will be acceptable. The framework
and structure shall be sufficiently rigid to withstand operation of the
equipment or any stresses due to short circuits. Each shipping assembly
shall also be sufficiently rigid, with the addition of temporary members if
required, to withstand handling during shipment and installation.
2.5.2.2
Enclosure
The enclosure shall be made of selected smooth sheet steel panels, suitably
supported. Doors and panels used to support instruments and other devices
and barriers between compartments shall not be less than No. 11 MSG.
Exposed panels on the front and ends of the enclosure shall be bent angle
or channel edges with all corner seams welded and ground smooth, or shall
be the manufacturer's equivalent construction as approved. The front
outside surfaces shall not be drilled or welded for the purpose of
attaching wires or mounting devices if such holes or fastenings will be
visible from the front.
2.5.2.3
Drawout Circuit Breaker
Each drawout type circuit breaker shall be completely enclosed in a metal
compartment. Access to the circuit breakers shall be provided through
hinged steel doors. Access to instrument and relay wiring, instrument
transformers and fuses, shall also be through hinged doors. All hinged
doors shall have bent angle or channel edges, invisible hinges and suitable
latches or fastenings. Access to bus compartments shall be through
removable bolted panels, cover plates or hinged doors.
2.5.2.4
Ventilating Opening
Ventilating openings shall be provided as required and shall preferably be
of the grille type. All ventilating openings shall be provided with
corrosion-resistant insect-proof screens on the inside.
2.5.2.5
Foundations
Continuous channel iron foundations, complete with bolts and drilled holes
for grouting and anchoring to the floor, shall be furnished by the
Contractor for the complete length (front and rear) of each [substation]
[switchgear assembly]. Channel construction and drilling shall be as
required for mounting the equipment. The channels shall be designed for
flat mounting and maximum channel depth shall be 63 mm 2-1/2 inches. The
foundation channels shall be placed on top of the floor, fastened in place,
and then filled with grout. Additional channel or substantial metal trim
shall be provided flush with the end panels to completely enclose the bases
across the ends of the equipment assemblies where exposed to view.
2.5.3
Buses and Connections
a. The buses in each main bus section shall have a continuous
current-carrying capacity of not less than [1,200] [1,600] [2,000]
[3,000] amperes without exceeding the temperature limits specified in [
IEEE C37.20.1][IEEE C37.20.2][IEEE C37.20.3]. The buses shall have
mechanical and thermal capacities coordinated with the interrupting
rating of the power supply circuit breakers. Bus bars shall be of
SECTION 16404A
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