An ADSS cable on a calm, dry day carries only its own weight. Add a 40 m/s wind gust and 20 mm of radial ice, and the effective load on the cable can increase by 3-5× — pushing the tension beyond the cable’s Maximum Allowable Tension (MAT) if the design didn’t account for these conditions. This guide explains how to calculate wind and ice loads per IEC 60826 and adapt the results to local national standards.
Why Wind and Ice Loading Governs ADSS Design
The bare-cable tension (no wind, no ice) is the starting point for ADSS design — but it’s rarely the governing case. The maximum tension the cable will experience during its 25-year life occurs under combined wind and ice loading, and this is the condition that must remain below the cable’s MAT (typically 40-60% of RTS).
For the tension design methodology, see our MAT calculation guide and sag and tension calculation guide.
Wind Load Calculation per IEC 60826
The wind force on the cable per unit length is:
F_wind = q × G × C_d × D
Where:
- q = dynamic wind pressure = 0.5 × ρ × V² (Pa), where ρ = air density (~1.225 kg/m³ at sea level) and V = reference wind speed (m/s)
- G = gust response factor (typically 1.0-1.3 for ADSS spans under 500m)
- C_d = drag coefficient (~1.0 for smooth cylindrical cables, ~1.2 for iced cables)
- D = cable diameter including ice (meters)
Example: V = 35 m/s, cable diameter = 20 mm (0.02 m):
q = 0.5 × 1.225 × 35² = 750 Pa
F_wind = 750 × 1.1 × 1.0 × 0.02 = 16.5 N/m — this adds to the cable’s self-weight vectorially.
Ice Load Calculation
The weight of ice accretion per meter of cable:
w_ice = ρ_ice × π × t × (D + t) × g
Where:
- ρ_ice = ice density (900 kg/m³ for glaze ice, 500-700 for rime ice)
- t = radial ice thickness (meters) — per IEC 60826 or local meteorological data
- D = cable diameter (meters)
Example: t = 0.015 m (15 mm), D = 0.02 m:
w_ice = 900 × π × 0.015 × (0.02 + 0.015) × 9.81 = 14.6 N/m
Combined Loading
The effective weight under combined wind and ice (the “resultant load”) is the vector sum:
w_eff = √[(w_cable + w_ice)² + F_wind²]
Using the example above: w_cable = 1.5 N/m, w_ice = 14.6 N/m, F_wind = 16.5 N/m
w_eff = √[(1.5 + 14.6)² + 16.5²] = √[259 + 272] = 23.0 N/m
This is 15× the bare cable weight — which is why wind and ice loading governs the design.
For regional design considerations, see our extreme weather design guide.
IEC 60826 vs. National Standards
IEC 60826 provides the international framework for overhead line loading. Many countries adopt it with national modifications:
- NESC (USA): Uses different wind speed maps, ice loading zones (light/medium/heavy), and overload capacity factors than IEC.
- AS/NZS 7000 (Australia/NZ): Regional wind speed maps (Regions A-D) and specific ice loading provisions for alpine areas.
- GB 50545 (China): Uses different return periods for wind speeds and specific ice loading zones defined by provincial meteorological data.
The rule: Always design to the stricter of IEC 60826 and the applicable national standard. A design that passes IEC but fails the national code is not acceptable for local permitting.
Key Takeaways
- Wind and ice loading can increase effective cable weight by 3-15× compared to bare-cable weight. This governs ADSS tension design.
- Calculate wind load using IEC 60826 F_wind = q × G × C_d × D with local wind speed data.
- Calculate ice load using w_ice = ρ_ice × π × t × (D + t) × g with regional ice thickness data.
- Combined loading = vector sum of vertical (weight + ice) and horizontal (wind) forces. Apply this to the sag/tension calculation.
- Design to the stricter of IEC and the applicable national code. Both must be satisfied.
Need Wind and Ice Load Calculations for Your Route?
Send us your span lengths, cable specification, and project location — we’ll run the loading calculations per both IEC 60826 and your local national standard.
Frequently Asked Questions
How do I calculate wind load on ADSS cable?
Use IEC 60826: F_wind = q x G x C_d x D, where q is dynamic wind pressure, G is gust factor, C_d is drag coefficient, and D is cable diameter including ice.
How much does ice loading affect ADSS cable tension?
Ice loading can add 10-15 N/m to the cable weight — 5-10x the bare cable weight for typical ADSS cables.
Which standard should I use for wind and ice loading?
Use IEC 60826 as the international baseline, then verify against your national standard (NESC, AS/NZS, GB). Design to the stricter of the two.
What is the combined loading formula for wind and ice?
w_eff = square root of [(w_cable + w_ice) squared + F_wind squared], representing the vector sum of vertical and horizontal forces.
How do I find wind speed and ice data for my project location?
National meteorological agencies provide wind speed maps and ice loading zones. IEC 60826 provides default values when local data is unavailable.