What is sag in overhead lines?

• A. The downward bend of a conductor between supports, caused by weight and temperature
• B. The distance between two adjacent supports
• C. The distance from line to ground
• D. The tension in the line

Answer: (A)

Sag is the vertical droop of an overhead conductor between supports caused by the weight of the conductor and thermal effects. The conductor hangs between towers, forming a downward bend, and this sag increases with temperature as the metal expands and decreases as it cools. This downward bend is what engineers manage to ensure safe clearance.

It’s not the distance between supports—that’s called the span. It’s not the distance from the line to the ground—that’s clearance. It’s not the tension—the force along the line.