Sag is the vertical distance between the lowest point of a conductor and the straight line connecting its two support points (towers or poles). Tension is the horizontal pulling force exerted on the conductor.

The relationship between sag and tension is inversely proportional. This means:

• As the tension on a conductor increases, the conductor becomes tighter, and the sag decreases.

• As the tension on a conductor decreases, the conductor becomes looser, and the sag increases.

This relationship is a direct consequence of the conductor's weight acting as a distributed load. The conductor's shape under its own weight is a catenary curve, which for shorter spans, can be approximated as a parabola. The fundamental formula for sag (S) is:

S=8TWL2

Where:

• W = Weight of the conductor per unit length

• L = Span length (distance between supports)

• T = Horizontal tension of the conductor

This formula clearly shows that sag (S) is inversely proportional to tension (T).