NESC Ice-and-Wind District Loading on a Conductor

Starts from its resultant weight per foot under the governing load case, and that case is not the bare conductor. NESC defines three loading districts, each a combination of radial ice, wind pressure, temperature, and a constant adder, and building that resultant is four steps of arithmetic done wrong more often than it is done. THE ICE IS AN ANNULUS, not a coating of the bare diameter, so its weight goes as the difference of squares -- which means the ice load on a small conductor is proportionally far worse than on a large one. Half an inch of radial ice on a 1.1 in conductor nearly doubles its weight; the same half inch on a 0.4 in neutral more than triples it, and that is why the light conductors come down first. The wind then acts on the ICED diameter rather than the bare one, and the two are combined as a VECTOR because they act at right angles. Last comes the constant, a flat adder to the resultant -- 0.30, 0.20, and 0.05 lb/ft for Heavy, Medium, and Light -- which is not physics but a deliberate margin, and it matters most on the light conductors where it is a large fraction of the total. Run ACSR Drake through all three and the Heavy district loads it at 2.30 times its bare weight, Medium at 1.65, and Light at 1.30 -- and the Light case has no ice at all, so that entire 30% is the wind vector and the constant. Feed the resultant rather than the bare weight into the change-of-state calculation and every tension and sag downstream changes by that factor. The district values are entered by selection here and are the NESC district definitions cited by name, not a reproduction of the code's tables; the district that applies is a matter of geography and of the edition the jurisdiction has adopted, and a utility may specify heavier loading than its district requires. This builds one combined load case on one conductor. It does not select the district, apply the overload capacity factors that the grade of construction requires, or evaluate the extreme-wind and extreme-ice-with-concurrent-wind cases that NESC requires separately for taller structures and that can govern instead. It does not model ice shedding, unbalanced ice between spans, or the longitudinal loads either produces, and it does not address galloping, which is an ice-and-wind phenomenon this arithmetic says nothing about. It does not compute a sag, a tension, or a structure load. The applicable NESC edition and its district map, the utility's construction standards, and a qualified line designer govern.

iced diameter = bare + 2 x radial ice; ice weight per foot = (pi/4)(iced^2 - bare^2)/144 x 57.3 lb/cu ft; vertical = bare weight + ice weight; horizontal = wind pressure x iced diameter / 12; resultant = sqrt(vertical^2 + horizontal^2) + k.

The NESC district loading combination CITED BY NAME, not reproduced: the Heavy, Medium, and Light district values (0.50/0.25/0.00 in radial ice, 4/4/9 psf, k of 0.30/0.20/0.05 lb/ft, at 0/15/30 degF) are the district definitions, and which district applies is geography and the adopted edition. Overload capacity factors and the separate extreme-wind and extreme-ice cases are NOT applied. The applicable NESC edition, the utility's construction standards, and a qualified line designer govern.

Geometry and a vector sum on a conductor's own published diameter and weight; no district map is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: bare_diameter_in, bare_weight_lb_per_ft, district, custom_ice_in, custom_wind_psf, custom_k_lb_per_ft, custom_temp_f, iced_diameter_in, ice_weight_lb_per_ft, vertical_lb_per_ft, horizontal_lb_per_ft, resultant_lb_per_ft, ratio_to_bare

• District values are cited, not a code reproduction which district applies is geography and the adopted editionthe applicable NESC edition
• Overload capacity factors are NOT applied nor the separate extreme-wind and extreme-ice casesthe applicable NESC edition
• Ice shedding and unbalanced ice excluded as are galloping and the longitudinal loads they produceoverhead line practice