General Order 95
(d) Sag Correction for Temperature
The curves, on chart 7 cover the correction of sags for stringing temperatures other than that for which the sag curves were calculated. These figures cover the normal range of stringing conditions for temperatures at time of stringing, varying between 0 degrees F. and 130 degrees F. and for spans of from 100 feet to 1,000 feet, inclusive, in 100–foot steps, with the exception that the 150–foot span has also been included. They represent average values for each degree F. difference between actual stringing temperature and the temperature for which the curves were calculated, that is 60 degrees F. The corrections for temperatures greater than 60 degrees F. are to be added to the normal sags while the corrections for temperatures less than 60 degrees F. are to be subtracted. The correction for a given difference of temperature from the base value is considered the same whether the stringing temperature is greater or less than the base value.
The use of these corrections may be illustrated by assuming a specific case:
A span of 300 feet - Heavy Loading District. Conductors No. 0 AWG copper, medium–hard–drawn, stranded, bare.
Stringing temperature 80 degrees F.
Minimum normal sag, chart 4 , is 5.30 feet.
Difference between stringing temperature and normal temperature is 20 degrees F.
The ratio for sag divided by span is 0.0177. From the curve on chart 7 , the correction per degree F. for this ratio for a span of 300 feet is 0.024 feet.
The total correction for 20 degrees F. difference is,
20 x 0.024 = 0.48 feet
Then the corrected sag is 5.30 + 0.48 equals 5.78 feet.
If some other span than those covered by specific curves is used, the correction may be obtained by interpolation between curves.