Three bare conductors, three constructions
Overhead distribution and sub-transmission lines use bare conductors stranded from aluminium wires, and buyers meet three families. ACSR (aluminium conductor, steel reinforced) has a core of galvanised steel wires - a single wire in 6/1 designs, seven wires in 26/7 and 54/7 designs - surrounded by layers of hard-drawn 1350-H19 aluminium wire. AAC is all-aluminium, stranded from 1350-H19 wire alone in concentric layers. AAAC is stranded entirely from 6201-T81 aluminium alloy wire, with no steel at all.
The aluminium carries nearly all the current in every family; the differences are strength, weight and corrosion behaviour. Steel adds tensile strength so the conductor can hold long spans between poles or towers, without adding much conductivity, because steel conducts poorly compared with aluminium. The 6201-T81 alloy carries more strength than pure aluminium at the same cross-section, which is why AAAC can hold useful spans on its own. Which family a line uses is the designer's call, made from span, sag, tension and environment. The buyer's job is to translate that call into an enquiry a factory can quote exactly, and that is what the rest of this post equips you to do.
What the steel core changes
Strength is the reason ACSR exists, and the key subtlety is that the same aluminium cross-section can be paired with different amounts of steel. At the 336.4 kcmil aluminium level, public datasheets list an 18/1 construction with a rated breaking load around 38.6 kN, a 26/7 construction around 62.7 kN and a 30/7 construction around 76.9 kN - more than double from one stranding to the next, with identical aluminium content. An enquiry that says only "336.4 kcmil ACSR" therefore does not define a product; the stranding has to be stated next to the size.
Weight and sag follow the same logic. Steel is denser than aluminium, so a heavier core at the same aluminium area means a heavier conductor and different sag-tension behaviour, which the line designer absorbs into the pole and tower design. DC resistance, by contrast, changes little across strandings of the same aluminium area, because almost all of the current flows in the aluminium layers; datasheet values are calculated from the aluminium content and confirmed by test. Our overhead bare conductors page shows the reference construction in cross-section, and the metals behind these families are compared on the conductor materials page.
Reference values from public datasheets
The reference model used on this site is an ACSR 6/1 of the Turkey class, a small distribution size: aluminium area about 13.3 mm2 (26.2 kcmil), aluminium and steel wires both 1.68 mm, overall diameter 5.03 mm, weight about 53.7 kg/km, DC resistance 2.10 ohm/km at 20 C, and a rated breaking load of about 5.29 kN. Mid-range and large constructions scale up quickly, as the table shows. All values are reference figures from public datasheets, framed here for comparison; the datasheet of the ordered construction governs every commitment.
| Class | Stranding | Aluminium area | Wire dia (mm) | OD (mm) | Weight (kg/km) | DC at 20 C (ohm/km) | Breaking load (kN) |
|---|---|---|---|---|---|---|---|
| Turkey | 6/1 | 26.2 kcmil (approx. 13.3 mm2) | 1.68 | 5.03 | 53.7 | 2.10 | approx. 5.29 |
| Linnet | 26/7 | 336.4 kcmil (approx. 170.5 mm2) | 2.89 alu, 2.25 steel | 18.3 | 688.5 | 0.166 | approx. 62.7 |
| Crow | 54/7 | 715.5 kcmil (approx. 362 mm2) | 2.92 | 26.3 | 1,371 | 0.0801 | approx. 117 |
Read the table for what it shows about families rather than as procurement numbers: resistance falls as the aluminium area grows, weight climbs faster than diameter, and breaking load depends on the steel share as much as on size.
Codenames, kcmil and EN 50182 designations
US-market conductors are ordered by aluminium size in kcmil, the stranding, and a codename: the 6/1 conductor above is the Turkey class, 336.4 kcmil in 26/7 is the Linnet class, and 715.5 kcmil in 54/7 is the Crow class. One kcmil is about 0.507 mm2, and converting on the spot matters whenever an enquiry crosses markets, as explained in our post on AWG and mm2 conversion. European projects usually name the same conductors by the BS EN 50182 designation instead, which spells out material, strength class and stranding: the Crow construction appears as 363-A1/S1A-54/7, where A1 is hard-drawn aluminium and S1A is standard-strength class A zinc coated steel. The standards behind the families are ASTM B230 for aluminium wire, B231 for AAC, B232 for ACSR and B398 and B399 for the 6201 alloy wire and stranded conductor, alongside IEC 61089 for round wire concentric lay overhead conductors.
Corrosion, grease and the coastal case for AAAC
Atmosphere decides the alloy question. Near coasts and in heavy industrial air, moisture and pollutants attack the zinc coating that protects ACSR's steel core, and a corroded core is the classic failure mode of steel-reinforced conductors in aggressive environments. AAAC removes the problem at the source: with no steel, there is nothing to rust, and corrosion resistance is the main reason 6201-T81 alloy is specified for coastal routes even though its conductivity per mm2 is lower than EC-grade aluminium. Where ACSR is kept, plants offer corrosion protection options: grease applied to the steel core only, or grease over the complete conductor, together with the zinc coating class agreed per order. In benign inland air with short spans, AAC is often the simplest and most economical choice, because it carries no steel and no alloy premium.
Packing and the enquiry that gets quoted right
Small sizes ship on reels or in coils - the Turkey class is commonly listed at around 5,400 ft per coil - while larger constructions travel on wooden reels, with reel diameters from 60 to 96 in common in published packaging tables. Reel length and gross weight drive freight cost and site handling, so they belong in the first enquiry, as covered on our packaging and drums page.
A quotation-ready enquiry for bare conductor names five things:
- Construction and codename: for example ACSR 26/7, 336.4 kcmil, Linnet class - or the EN 50182 designation.
- Standard: ASTM B232 for ACSR, B231 for AAC, B399 for AAAC, or BS EN 50182 for European projects.
- Protection: zinc coating class, and the grease option if required.
- Quantity and packing: total length, length per reel or coil, and any site limits on reel weight.
- Documents: the test certificate expected, typically DC resistance and breaking load records, referenced to the shipment.
Send the enquiry through the quote form and the desk returns a written datasheet to confirm before any plant books material; typical minimums and lead times are set out on the MOQ and lead time page.