MIL-HDBK-1004/2A
5.4.1
Structure-Mounted Equipment. Structure-mounted equipment should be
used for voltages above 35 kV. The use of modern low-profile metal structures
with tubular type or H-beam supports is considered the most desirable design.
The conventional lattice-type structure is unattractive in appearance, more
difficult to maintain, and more vulnerable to the twisting forces from heavy
winds (see Figure 5).
5.4.2
Transformers. Primary unit substations require less land space, are
visually less objectionable, and because of the integrated transformer to
secondary connection, are more reliable than separate substation transformers
and secondary protective devices.
5.4.3
Connection to Primary Distribution Lines. An underground connection
from the station to aerial lines should be provided when distribution voltage
is 35 kV or less. An underground line not only provides aesthetic enhancement
but reduces vulnerability to lightning or other weather or man-produced
interruptions.
5.5
Substation Considerations. Consider the effects that the actual
site electrical configuration, type of incoming and outgoing switching, need
for supporting structures and surge protection, type of transformers, and
control features have on a substation layout.
5.5.1
Site Effects. In the design of a substation, consider the following
factors:
a) Architectural requirements; landscaping.
b) Exposure conditions; for example, at the seashore or in other
corrosion-producing atmospheres.
c) Physical conditions such as snow or ice, sandstorms, altitude,
and lack of rainfall.
d) Adjacent terrain and installations affect landscaping layout and
noise treatment. Utilize the influence of the direction of prevailing winds
on sound propagation to minimize noise exposure (refer to NAVFAC DM-1.03).
Electric Configuration. Determine the electrical configuration with
5.5.2
the respect to provisions for adequate station capacity plus supply and feeder
circuit conditions. Consider supply circuit requirements for the following
conditions:
a)
single or multiple supply,
b)
supply circuit voltage and phases,
c)
overhead or underground supply required, and
d)
primary switching.
For feeder or load circuits, determine the following conditions:
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