TM
5-811-1/AFJMAN
32-1080
which can be tedious and time-consuming. Conduc-
loaded tensions and sags for conductors which
were initially strung to the sags of table 6-2. Sags
tor manufacturers have computer programs which
have been developed to perform these calculations.
are a maximum at the indicated loading condi-
tions. Tensions will be less at higher temperatures
The assumed value of 2.06 feet of sag and 3,350
pounds tension are different from the values given
when wind and ice loads do not apply (final
unloaded conditions).
in table 6-3 where the values listed are 2.4 feet of
sag and 2,870 pounds tension. The variation re-
(3) Unusual loading conditions. The NESC
sults because of elastic creep; however, the varia-
stipulates loading and installation requirements
tion in values of about 15 percent, in this case,
for normal conditions, as shown in table 6-3;
provides a more conservative design or an addi-
however, many areas will be subjected to climatic
tional safety factor.
conditions much more severe than those listed, in
resepct to both wind and ice loads. In these
e. Conductors for Air Force installations.
instances, a complete analysis will be required to
(1) Minor extensions to systems using copper
determine acceptable sagging versus strength. An
conductors shall be made with copper.
example of an aerial conductor strength analysis is
(2) Major extensions to existing systems and
given in figure 6-1. Pole line analyses will be
new systems shall be of bare hard drawn copper,
provided and will show calculations for pole
aluminum, or steel reinforced aluminum.
strengths, guying, span length, and sags. This type
(3) Self-supporting aerial cable with insulated
of calculation requires making an assumption (in
cable lashed to the neutral messenger or individ-
this case that conductor sag equal 2.06 feet) and
ual insulated cables supported from the messenger
then checking the validity of the assumption,
with insulated spacers may be utilized if approved
Table 6-3. Final Loaded Tensions for 200-Foot Spans,
6-4
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