Overhead conductor sag calculator
Pick an ACSR or AAAC code, the span and the tension as a percentage of breaking load. The calculator gives the sag, conductor length in the span and the tension, with an optional wind pressure on the conductor.
Basis
Parabolic approximation D = w·L² / (8·T); conductor mass and breaking load from IS 398 (Parts 2 and 4).
Reference values for planning and comparison. Confirm against the current standard, the purchaser’s specification and the manufacturer’s datasheet before ordering.
ACSR sag (m) at 22 % of breaking load, still air
| Conductor | 60 m span | 100 m | 250 m | 400 m |
|---|---|---|---|---|
| ACSR Rabbit | 0.235 | 0.652 | 4.07 | 10.43 |
| ACSR Raccoon | 0.238 | 0.661 | 4.13 | 10.57 |
| ACSR Dog | 0.244 | 0.678 | 4.23 | 10.84 |
| ACSR Wolf | 0.216 | 0.601 | 3.76 | 9.62 |
| ACSR Panther | 0.218 | 0.605 | 3.78 | 9.68 |
| ACSR Zebra | 0.25 | 0.693 | 4.33 | 11.09 |
| ACSR Moose | 0.251 | 0.698 | 4.36 | 11.16 |
Worked example: Sag of ACSR Dog on a 100 m span
- Weight w = 394 kg/km × 9.81 = 3.86 N/m.
- Tension T = 22 % × 32.4 kN = 7.13 kN.
- Sag D = w L² ÷ 8T = 3.86 × 100² ÷ (8 × 7,128) = 0.678 m.
How is conductor sag calculated?
For level spans up to a few hundred metres, sag D = w × L² / (8 × T), where w is the conductor weight per metre (plus wind, as a resultant), L the span and T the horizontal tension.
What tension is used for sag calculation?
Utilities set it in the line design, commonly as a percentage of the conductor’s breaking load at everyday temperature, with a higher limit under maximum wind. Use the value in your specification.
What is the sag of ACSR Dog on a 100 m span?
At 22 % of its 32.4 kN breaking load (7.13 kN) and 394 kg/km, still air, the sag is about 0.68 m. Temperature and creep change it; the line design decides the stringing chart.