Standard Specification for Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductors, Coated-Steel Supported (ACSS/TW) for use as overhead electrical conductors in transmission and distribution lines.
ASTM B857 covers shaped (trapezoidal) wire compact concentric-lay-stranded aluminum conductors with a coated steel core, designated ACSS/TW, intended for use as bare overhead electrical conductors in transmission and distribution applications.
The trapezoidal wire profile allows a higher aluminum fill factor within the same outer diameter as a conventional round-wire conductor, resulting in either greater current-carrying capacity at the same diameter, or a smaller diameter at the same cross-sectional area, compared to standard ACSS. Two design options are specified: equal area (smaller OD than ACSS) and equal diameter (greater aluminum area than ACSS).
ACSS/TW is a non-homogeneous composite conductor. Coated steel strands form the central core carrying the majority of the mechanical load, while one or more layers of trapezoidal-shaped, fully annealed aluminum 1350-O wires are stranded concentrically around the core.
Round high-strength steel wires coated with Galfan® (Zn–5% Al alloy), Class A zinc, or aluminum cladding. Carries the majority of mechanical tensile load. Single or multiple wire configurations per ASTM B498 or B606.
One or more concentric layers of shaped (trapezoidal cross-section) aluminum 1350-O wires, fully annealed for maximum sag performance. The trapezoidal shape increases packing efficiency versus round-wire stranding.
Fully annealed ("O" temper) aluminum 1350 alloy with minimum 63% IACS electrical conductivity. The soft temper prevents long-term creep-induced sag increase, as mechanical load transfers to the steel core.
Electric-butt welds, cold-pressure welds, and electric-butt cold-upset welds may be made in individual aluminum wires during the stranding process.
Representative codeword sizes from ASTM B857-22 Table 1. Equal-area design (same aluminum cross-section as equivalent ACSS/ACSR Class AA). Actual dimensions may vary slightly between manufacturers.
| Codeword | Size (kcmil) | Al Strands | Nom. OD (mm) | Nom. Mass (kg/km) |
|---|---|---|---|---|
| ORIOLE | 336.4 | 16 | 17.60 | 807 |
| HAWK | 477 | 18 | 20.07 | 976 |
| DRAKE | 795 | 20 | 25.65 | 1,624 |
| CARDINAL | 954 | 20 | 27.43 | 1,822 |
| GRACKLE | 1,192.5 | 38 | 31.12 | 2,278 |
| LAPWING | 1,590 | 36 | 34.49 | 2,664 |
| SANTEE | 2,627.3 | 64 | 44.71 | 4,557 |
ASTM B857 mandates the following tests to verify conductor performance:
ACSS/TW is widely adopted for reconductoring projects where existing tower and foundation structures must be retained. Because ACSS/TW operates at up to 250 °C without strength loss, it allows a significant increase in line ampacity without requiring structural upgrades, new right-of-way, or rebuilding towers. The equal-area design delivers the same current capacity as a conventional ACSS at a reduced diameter, lowering wind and ice loads on existing structures.
Official Standards & References
Direct from the factory floor in Henan, China — we manufacture ACSR conductors to ASTM, IEC, BS, and other standards for utility and EPC projects.
Henan Zhong Dong Cable Co., Ltd.
3,000,000+ km annual output · Serving 50+ countries
Share your project specs and quantity — our senior engineer will reply with a verified quote within 24 hours.
🔒 Your inquiry stays confidential. We never share contact info with third parties.
