Peak demand and/or warm temperatures can cause a long span of transmission to sag by an additional __________.

• A. 25-30 feet
• B. 20-25 feet
• C. 1-5 feet
• D. 10-20 feet

Answer: (D)

When a transmission line heats up, it expands. Peak demand and warm temperatures raise the conductor temperature, which reduces the tension and allows the line to drop more between towers. For long spans, this thermal expansion translates into a noticeable extra sag. In practice, the extra sag you’ll see on long transmission spans under hot conditions is typically in the range of about ten to twenty feet.

The other ranges are less consistent with how long spans behave under heat: too little sag (1–5 feet) wouldn’t reflect the significant expansion from warmth, while larger reaches like twenty-five or thirty feet would push the line well beyond normal design margins except in extreme cases. Engineers design for these conditions using sag-tension relationships so clearance is maintained across temperature variations.