curves, the conductor elongation from the initial elongation of 0.062% increases to 0.11%, 0.12%, and
0.15%, respectively. Because of creep elongation, the resulting final sags are greater and the conductor
tension is less than the initial values.
Creep elongation in aluminum conductors is quite predictable as a function of time and obeys a
simple exponential relationship. Thus, the permanent elongation due to creep at everyday tension can be
found for any period of time after initial installation. Creep elongation of copper and steel conductors is
much less and is normally ignored.
Permanent increase in conductor length due to heavy load occurrences cannot be predicted at the time
that a line is built. The reason for this unpredictability is that the occurrence of heavy ice and wind is random.
A heavy ice storm may occur the day after the line is built or may never occur over the life of the line.
14.3.2 Sag-Tension Tables
To illustrate the result of typical sag-tension calculations, refer to Tables 14.4 through14.9showing
initial and final sag-tension data for 795 kcmil-26=7 ACSR ‘‘Drake’’, 795 kcmil-37 strand AAC ‘‘Arbutus’’,
and 795-kcmil Type 16 ‘‘Drake=SDC’’ conductors in NESC light and heavy loading areas for spans of
TABLE 14.4 Sag and Tension Data for 795 kcmil-26=7 ACSR ‘‘Drake’’ Conductor
Span¼600 ft
NESC Heavy
Loading District
Creep isnota factor
Final Initial
Temp, 8 F Ice, in. Wind, lb=ft^2 K, lb=ft
Resultant Weight,
lb=ft Sag, ft Tension, lb Sag, ft Tension, lb
0 0.50 4.00 0.30 2.509 11.14 10153 11.14 10153
5415 Al 5415 Al
4738 St 4738 St
32 0.50 0.00 0.00 2.094 44.54 8185 11.09 8512
3819 Al 4343 Al
4366 St 4169 St
20 0.00 0.00 0.00 1.094 6.68 7372 6.27 7855
3871 Al 4465 Al
3501 St 3390 St
0 0.00 0.00 0.00 1.094 7.56 6517 6.89 7147
3111 Al 3942 Al
3406 St 3205 St
30 0.00 0.00 0.00 1.094 8.98 5490 7.95 6197
2133 Al 3201 Al
3357 St 2996 St
60 0.00 0.00 0.00 1.094 10.44 4725 a 9.12 5402
1321 Al 2526 Al
3404 St 2875 St
90 0.00 0.00 0.00 1.094 11.87 4157 10.36 4759
634 Al 1922 Al
3522 St 2837 St
120 0.00 0.00 0.00 1.094 13.24 3727 11.61 4248
35 Al 1379 Al
3692 St 2869 St
167 0.00 0.00 0.00 1.094 14.29 3456 13.53 3649
0 Al 626 Al
3456 St 3022 St
212 0.00 0.00 0.00 1.094 15.24 3241 15.24 3241
0Al 0Al
3241 St 3239 St
aDesign condition.