TM
5-811-1/AFJMAN
32-1080
CHAPTER 6
AERIAL DISTRIBUTION LINES
6-1 General.
will include provisions for raptor protection in
accordance with Federal and state laws. Consult
Aerial lines will be provided in all areas as
REA Bulletin 61-10, "Protection of Bald and
established in chapter 5. In order to use the same
Golden Eagles from Powerlines." The requirement
poles for both aerial distribution and roadway
for wooden cross-arm braces should be verified for
lighting and to avoid interference with possible
each state and land area in accordance with the
future projects, consideration will be given to
Bald Eagle Protection Act of 1940 (16 U.S.C. 688
installing pole lines adjacent to roadways.
et seq.) as amended; the Endangered Species Act of
a. Symbols and codes. For uniformity, symbols
1973 (87 Stat. 1064); and Migratory Bird Treaty of
will comply with ANSI Y32.9. Installation will
1918 (16 U.S.C. 703 et seq.) as amended. Sources
comply with the requirements of the NESC for
include the Bureau of Land Management, U.S.
Grade B construction and the NEC as required.
Department of the Interior and Federal, state and
The loading district will be that applying to the
local land management or wildlife conservation
location of the installation as required by the
agencies.
NESC. Where state safety rules are predominantly
accepted, such rules may be used provided they
6-3. Conductors.
are at least as stringent as those of the NESC.
b. Circuit configurations. Typical circuit configu-
a. Sizes. Where possible, conductor sizes will be
rations and details are provided later in this
limited to a maximum of No. 4/0 AWG copper or
chapter as a general guide in the design. In
equivalent aluminum. Conductor sizes above No.
addition, publications of the Rural Electrification
4/0 AWG copper or equivalent aluminum will be
Administration (REA) will be helpful.
justified by an economic analysis of the alterna-
c. Other conditions. Service conditions are cov-
tives (such as additional circuits or a higher
ered in chapter 1. Special items such as overhead
distribution or sub-transmission voltage). The eco-
grounding conductors, grounding, and surge pro-
nomical minimum conductor size for circuits serv-
tection are covered in chapter 9. Other conditions
ing administrative, support and housing areas is
will follow the guidelines established by the
No. 2 AWG hard down copper or equivalent
aluminum. For small, isolated loads a minimum
NESC, the REA, or the local utility as applicable.
size of No. 6 AWG copper or equivalent aluminum
6-2. Installation Considerations.
will be used.
b. Material. Aluminum conductor steel rein-
Design of span lengths for aerial lines will be
based on such factors as conductor sizes, conductor
forced (ACSR), aluminum alloys, or hard-drawn
loadings (conductor weight, wind loading, and ice
copper (CU) may be used for medium-voltage lines.
Low-voltage conductors may be of aluminum alloys
loading), and load density. Rural area design will
be predicated on the most economical span length
with ACSR messengers or of copper. However, the
selection of copper or aluminum will be justified
for the terrain, NESC loading area, conductor size
based upon an analysis using life, environmental,
and strength, functional use, and the requirements
of joint-use communication lines. Designs for areas
and cost factors.
(1) Type of aluminum alloys. In their stan-
such as military base housing, administration,
dards and data publications, the Aluminum Asso-
maintenance, and support areas will consider area
functional use, span length for the terrain, NESC
ciation recognizes three alloys of aluminum as
suitable for electric conductors. All-aluminum-
loading area, conductor size and strength, and the
conductors, formerly known as hard-drawn alumi-
requirements of joint-use communication lines,
num or EC grade are now designated as alloy
street and area lighting. Distribution criteria for
1350-H19 and the acronym to be used will be
ammunition plant or process facilities will be
AAC. This alloy with a 61 percent copper conduc-
based on all of the above and include the require-
tivity is not a preferred type because of the alloy's
ments of AMCR-385-100. No more than two
low inherent tensile strength. The intermediate
medium-voltage circuits will be installed on one
strength (5005-H19), alloy will not be used since
pole. Switches to facilitate the transfer of load will
the conductivity is only one percent greater than
be provided where circuitry makes this provision
t h e high-strength alloy. The high-strength
economically justifiable. Pole line configuration
6-1
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