Standard Specification for Concentric-Lay-Stranded Aluminum Conductors, Aluminum-Clad Steel Reinforced (ACSR/AW) for use as bare overhead electrical conductors in transmission and distribution lines, particularly in corrosion-demanding environments.
ASTM B549 covers concentric-lay-stranded conductors made from round aluminum 1350-H19 extra-hard wires stranded around an aluminum-clad steel (AW) core, for use as bare overhead transmission and primary/secondary distribution conductors.
ACSR/AW is structurally identical to conventional ACSR (ASTM B232), except the galvanized steel core is replaced with an aluminum-clad steel (AW) core. This substitution virtually eliminates galvanic corrosion between the aluminum outer wires and the steel core, making ACSR/AW the preferred conductor for coastal, marine, salt-fog, and industrially polluted environments where standard ACSR suffers accelerated core degradation. The conductor is available in two classes: Class AA (standard Al/steel ratio) and Class A (higher steel content for greater mechanical strength).
ACSR/AW is a composite concentric-lay-stranded conductor. The aluminum-clad steel core provides mechanical strength and corrosion resistance, while the extra-hard 1350-H19 aluminum outer layers carry the electrical current. Both components contribute to the rated breaking strength.
High-strength steel wire with a minimum 10% aluminum cladding by cross-sectional area, bonded metallurgically to the steel. The aluminum cladding provides a galvanic barrier that prevents corrosion between the steel core and aluminum outer wires. Complies with ASTM B502.
Round extra-hard (H19 temper) aluminum 1350 alloy wires concentrically stranded around the AW core. Identical geometry to standard ACSR. Common stranding configurations: 6/1, 26/7, 30/7, 54/7, 54/19 (Al/AW wire counts).
The rated breaking strength is the aggregate of the aluminum wire component and the AW steel core component. The steel core contribution is calculated as a defined percentage based on the number of aluminum-clad steel wire layers.
Electric-butt welds, cold-pressure welds, and electric-butt cold-upset welds are permitted in individual aluminum wires prior to stranding. No joints are permitted in completed conductor sections.
Representative sizes from ASTM B549 Table 1 (Class AA). Bird codeword designations are shared with standard ACSR, as conductor geometry is identical. DC resistance corrected to 20 °C.
| Codeword | Size (kcmil) | Stranding (Al/AW) | Nom. OD (in.) | RBS (lbs) | DC Resist. (Ω/1000 ft @ 20 °C) |
|---|---|---|---|---|---|
| SWAN/AW | 4 AWG | 6/1 | 0.250 | 1,780 | 0.3917 |
| PARTRIDGE/AW | 266.8 | 26/7 | 0.642 | 13,900 | 0.0640 |
| HAWK/AW | 477 | 26/7 | 0.858 | 22,400 | 0.0357 |
| DRAKE/AW | 795 | 26/7 | 1.108 | 34,500 | 0.0213 |
| CARDINAL/AW | 954 | 54/7 | 1.196 | 38,400 | 0.01769 |
| LAPWING/AW | 1,590 | 45/7 | 1.502 | 53,100 | 0.01058 |
| CHUKAR/AW | 1,780 | 84/19 | 1.602 | 60,800 | 0.00943 |
ASTM B549 requires the following tests, conducted on individual wires before stranding and on the completed conductor:
ACSR/AW per ASTM B549 is the industry-standard solution for transmission and distribution lines in coastal, salt-fog, industrial, and tropical environments where conventional ACSR experiences accelerated galvanic and oxidative corrosion of the galvanized steel core. The metallurgically bonded aluminum cladding on each steel wire creates a continuous, self-healing galvanic barrier that prevents electrolytic attack at the aluminum-steel interface — eliminating the principal failure mode of standard ACSR in aggressive climates. Because conductor geometry is identical to ACSR, reconductoring projects require no changes to hardware, insulators, or tower attachment points.
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