Electrical cables sag primarily due to a combination of physical forces and environmental conditions. The main factors are:

• Gravity and Conductor Weight: The most fundamental reason for sag is the cable's own weight, which pulls it downward between support structures, forming a catenary curve.

• Temperature Variations: This is a crucial factor. As temperatures increase, the cable material (like aluminum or copper) expands, increasing its length and consequently, the sag. Conversely, in cold weather, the cable contracts, reducing the sag and increasing the tension.

• Mechanical Loads: External forces such as wind, ice, or snow can add significant weight and pressure to the cables, increasing the sag. Heavy ice accumulation is a common cause of excessive sag and conductor failure.

• Span Length: The distance between two support structures (poles or towers) is directly proportional to the sag. Longer spans result in greater sag.

• Tension: The tension applied to the cable during installation is inversely proportional to the sag. Higher tension results in less sag, but it also increases mechanical stress on the conductor and support structures.