T/F: maximum sag in stringing condition

FALSE.

The sag at stringing lies between the sags of the two extreme design conditions. It is never larger than both of them.

• Toughest condition (lowest temperature, maximum wind, ice if any): tension is at its maximum, $T = \text{UTS}/\text{FS}$. The effective weight $W_1=\sqrt{(w_c+w_i)^2+w_w^2}$ is also at its maximum. The resulting sag is inclined and is used for checking strength.
• Easiest condition (highest temperature, still air, no ice): the conductor is at its longest and tension is lowest. This gives the maximum vertical sag, which fixes the ground clearance and the tower height.
• Stringing condition (normal erection temperature, about 20–30°C, no wind, no ice): the temperature is below the easiest-condition temperature. The conductor is therefore shorter and tighter, so

$$D_{\text{stringing}} = \frac{w_c L^2}{8T_{\text{str}}} < D_{\text{easiest}} = \frac{w_c L^2}{8T_{\text{easiest}}}$$

because $T_{\text{str}} > T_{\text{easiest}}$ for the same weight $w_c$.

Example: for a 300 m span of a 462.6 mm² ACSR conductor, the toughest-condition sag is about 9.9 m and the stringing sag at 25°C is about 8.8 m. So the stringing sag is the smaller one.

The stringing sag is found from the change-of-state (stringing) equation, starting from the toughest condition. The conductor is pulled to this sag during erection so that the line meets its limits at the two extremes.