Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductors, Coated-Steel Supported (ACSS/TW)

B857-14: Standard Specification for Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductors, Coated-Steel Supported (ACSS/TW)

In the critical domain of overhead electrical transmission, the reliability and efficiency of conductors are paramount. For engineers and designers tasked with specifying these essential components, understanding the nuances of advanced conductor technologies is key. ASTM B857-14 provides an authoritative framework for a specific type of high-performance conductor, offering proven solutions for demanding power transmission applications.

What is B857-14?

ASTM B857-14 is the industry-leading standard that defines the requirements for Shaped Wire Compact Concentric-Lay-Stranded Aluminum Conductors, Coated-Steel Supported (ACSS/TW). Developed by ASTM International, this comprehensive specification ensures the quality, performance, and consistency of these specialized conductors used in overhead electrical systems. Its primary purpose is to facilitate the design and procurement of conductors that offer enhanced aluminum cross-sectional area or reduced overall diameter for a given electrical capacity.

Scope & Purpose

This essential standard governs the construction, materials, and performance characteristics of ACSS/TW conductors. It specifically addresses conductors composed of a central core of coated steel wires surrounded by layers of trapezoidal-shaped aluminum wires. The standard outlines methods for sizing and stranding to achieve specific electrical and mechanical properties, ensuring interchangeability with existing conductor types where applicable. It does not cover the installation procedures or the environmental operating conditions, which are typically addressed in separate engineering guidelines.

Who Must Comply?

• • Primary audience: Electrical Engineers, Materials Engineers, Mechanical Engineers, Project Managers, and Field Technicians involved in the design, specification, manufacturing, and installation of overhead power transmission lines.
• • Industries affected: Electrical Power Generation, Transmission, and Distribution; Utility companies; and Manufacturers of electrical conductors.
• • Compliance nature: Voluntary, but widely adopted as a basis for procurement specifications and industry best practices.
• • Enforcement: Compliance is typically verified through material testing, factory inspections, and adherence to contractual specifications by utilities and project owners.

Key Requirements Overview

The standard requires that ACSS/TW conductors be constructed with a core of coated steel wires, providing mechanical strength, and surrounded by carefully layered trapezoidal aluminum wires for electrical conductivity. Professionals must ensure that the aluminum wires are of the specified alloy (typically Aluminum 1350-0) and temper for optimal performance. Key provisions include detailed requirements for the stranding patterns, conductor diameters, and electrical resistance, often tabulated to align with established ACSR and ACSS conductor sizes for ease of selection. The standard also mandates the testing of conductor properties, such as cross-sectional area and tensile strength, to verify compliance with specified performance criteria.

Related Standards & References

ASTM B857-14 works in conjunction with several other ASTM standards. For instance, ASTM B498/B498M and ASTM B500/B500M are crucial for specifying the requirements of the coated steel core wires, ensuring their compatibility and durability. Furthermore, ASTM B609/B609M provides specifications for the aluminum wires themselves, detailing their properties and quality. These complementary standards collectively ensure the integrity and performance of the final ACSS/TW conductor assembly.