ASTM B231/B231M-23 PDF

Overview

ASTM B231/B231M-23 is the internationally recognized standard specification for concentric-lay-stranded Aluminum 1350 conductors, published by ASTM International. This standard defines the construction, classification, and essential requirements for bare concentric-lay-stranded aluminum conductors comprised of Aluminum 1350-H19, 1350-H16 or -H26, 1350-H14 or -H24, and 1350-H142 or -H242 alloys. These conductors are widely used in electrical power transmission and distribution systems due to their high conductivity and favorable strength-to-weight ratio.

Key Topics

• Conductor Construction

  • Specifies bare conductors with a central round wire, surrounded by one or more helically laid layers of wires for flexibility and mechanical integrity.
  • The conductors are classified by their mechanical application and need for flexibility:
    • Class AA: Used for bare overhead lines.
    • Class A: Intended for covered conductors or applications needing more flexibility than Class AA.
    • Class B: Designed for insulation with materials like rubber or cloth or where further flexibility is needed.
    • Classes C and D: Used for applications requiring even greater flexibility.

• Material Requirements

  • Conductors must use Aluminum 1350 alloy with specific temper designations (mechanical hardness).
  • For Classes AA and A, the default temper is 1350-H19, unless otherwise specified.
  • Conformance with industry alloy and temper designations is required.

• Stranding Configuration

  • The standard defines the direction and length of wire lay (helical wrapping) for various classes.
  • Right-hand lay for Classes AA and A; left-hand for others unless specified.
  • Successive layers may have reversed lay direction for mechanical strength.

• Performance and Testing

  • Rated minimum strengths are based on the sum of the strengths of individual wires, accounting for conductor class.
  • Density, resistivity, and temperature values are standardized in SI units.
  • Electrical resistance is standardized and must not exceed maximum allowed values.
  • Detailed requirements are specified for mechanical and electrical testing, packaging, and marking.

Applications

• Overhead Transmission Lines: Bare Class AA conductors are optimized for outdoor, overhead power transmission lines due to their excellent conductivity and robustness.
• Insulated Power Cables: Class A, B, C, and D conductors are used in insulated and covered cables, serving urban infrastructures, power distribution networks, and industrial applications.
• Utility and Industrial Use: Due to their flexibility options and reliability, these aluminum conductors are used in substation connections, utility grids, and various large-scale industrial projects.
• Compatibility: Aluminum 1350 conductors are designed for general electrical purposes and are compatible with global standards for both metric and inch-pound unit systems.

Related Standards

• ASTM B230/B230M: Specification for Aluminum 1350–H19 Wire for Electrical Purposes; details requirements for wire used to manufacture stranded conductors under B231/B231M.
• ASTM B609/B609M: Covers aluminum 1350 round wire in annealed and intermediate tempers for electrical purposes.
• ASTM B682: Describes standard metric sizes for electrical conductors.
• ANSI H35.1/H35.1M: System for alloy and temper designation for aluminum.
• ASTM B193: Test method for measuring resistivity of electrical conductor materials.
• ASTM B263: Test method for determining the cross-sectional area of stranded conductors.

By following ASTM B231/B231M-23, manufacturers, engineers, and utilities ensure that concentric-lay-stranded Aluminum 1350 conductors meet the necessary performance, safety, and compatibility requirements for modern electrical grids. This standard supports reliable power transmission and distribution infrastructure, meeting both national and international expectations for quality and interoperability.