MIL-HDBK-1004/2A
SECTION 5:
SUBSTATIONS
5.1
General Considerations. Substations are categorized in this
handbook by type of system supplied and their physical location. Since there
are many types, substation terminology and layouts are provided for guidance
and to assist in understanding criteria applications.
Table 5
Substation Terminology
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TERM
DEFINITION
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Substation
An assemblage of equipment for purposes other than
generation or utilization, through which electric
energy in bulk is passed for the purpose of switching
or modifying its characteristics.
Unit substation
A substation consisting primarily of one or more trans-
formers which are mechanically and electrically
connected to and coordinated in design with one or more
switchgear or motor control assemblies, or combinations
thereof.
Primary unit
A unit substation in which the low-voltage section is
rated substation
above 1000 volts. See NEMA 201, Primary Unit
Substations.
Secondary unit
A unit substation in which the low-voltage section is
rated substation
1000 volts and below. See NEMA 210, Secondary Unit
Substations.
Articulated unit
A unit substation in which the incoming, transforming
and substation (pri-
outgoing sections are manufactured as one or more
mary or secondary)
subassemblies intended for connection in the field.
Load center (a)
A manufacturer's designation for an articulated
secondary
unit substation with secondary switchgear (also known
as a power center).
Integral trans-
A load center with a secondary panelboard instead of
former load center (a)secondary switchgear.
Pad-mounted
A transformer utilized as part of an underground
compartmental-
distribution system with enclosed compartment(s) for
type transformer
high- and low-voltage cables entering from below and
mounted on a foundation pad.
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(a) Terms not listed in IEEE Standard 100.
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