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Description / Abstract:
This guide covers three-phase unit substations for step-down
operation in the range of 112.5 kVA or greater at primary voltages
of 601 V through 38 kV
This guide does not cover the following installations:
a) Substations in which the transformer section includes
load-tap-changing equipment.
b) Substations in which the transformer section is described and
defined as "network," "subway," "vault," or "underground" in IEEE
Std C57.12.24™ [B14] and IEEE Std C57.12.40™ [B18].
c) Substations in which the transformer section is described and
defined as "pad-mounted" in ANSI C57.12.22 and IEEE Std C57.12.27™
[B16].
d) Gas-insulated substations as described in IEEE Std C37.122™
[B13].
e) Rectifier-type substations.
f) Mobile unit substations.
g) Installations in ships, watercraft, railway rolling stock,
aircraft, or automotive vehicles.
h) Installations for mines.
i) Installations of railways for generation, transformation,
transmission, or distribution of power used exclusively for
operation of rolling stock, or for installations used exclusively
for signaling and railway communication purposes.
j) Installations of communication equipment that is under the
exclusive control of communication utilities, located outdoors or
in building spaces used exclusively for such installations.
k) Installations under the exclusive control of electric
utilities for the purpose of communication, or metering; or for the
generation, control, transformation, transmission, and distribution
of electric energy located in buildings used exclusively by
utilities for such purposes or located outdoors on property owned
or leased by the utility or on public highways, streets, roads,
etc; or outdoors by established rights on private property.
Purpose
The guide is intended for use as the basis for the coordination
of equipment in unit substations by assisting in the selection of
components. A variety of designs for unit substations are possible
using various combinations of incoming sections, transformer
sections, outgoing sections, and transition sections.
It is intended that the incoming, outgoing, transformer, and
transition sections included in a unit substation shall meet the
basic requirements of applicable industry standards for those
sections. In addition, this guide provides suggested requirements
when used as part of a unit substation.