IEC 60228:2004

Overview

IEC 60228:2004 - "Conductors of insulated cables" is an international standard from the IEC (Technical Committee 20) that defines nominal conductor sizes, construction classes and resistance limits for conductors used in electric power cables and cords. The standard covers nominal cross‑sectional areas from 0.5 mm² to 2 500 mm², and includes solid and stranded copper, aluminium and aluminium alloy conductors for fixed installations and flexible copper conductors for cords. It does not apply to telecommunication conductors. Informative annexes provide temperature correction factors for resistance measurement (Annex B) and dimensional guidance for circular conductors (Annex C).

Key topics and technical requirements

• Nominal cross‑sectional areas: Standard sizes and the definition of nominal cross‑sectional area as an identifying value (0.5 mm² – 2 500 mm²).
• Conductor classes: Classification into Class 1 (solid), Class 2 (stranded), Class 5 and 6 (flexible), with intended uses for fixed and flexible cables.
• Materials and mechanical limits: Requirements for plain or metal‑coated annealed copper, aluminium and aluminium alloy conductors; tensile strength limits for solid and stranded aluminium wires where specified.
• Construction rules: Minimum numbers of wires, uniform wire diameters, limits on wire diameter ratios, and guidance on compacted and shaped stranded conductors.
• Electrical resistance: Maximum permissible resistance values measured at 20 °C (detailed in Tables 1–4), including a note that aluminium alloy conductors with the same dimensions as aluminium will have higher resistance (factor guidance provided).
• Testing & measurement: Clause references and Annex A/B for resistance measurement procedures and temperature correction factors.
• Dimensional guidance: Annex C gives recommended dimensional limits for circular conductors and strengthened guidance for compacted stranded copper.

Applications and users

IEC 60228 is a fundamental reference for:

• Cable designers and manufacturers for specifying conductor construction, sizes and resistance.
• Test laboratories and certification bodies verifying compliance with conductor resistance and construction classes.
• Standards committees and procurement/specification writers who reference conductor requirements in cable product standards.
• Electrical engineers and installers who need to match conductor performance (resistance, flexibility) to application requirements.

Note: For specific cable types, applicability is governed by the corresponding cable standard. The standard also includes practical conversion and usage notes (e.g., AWG/kcmil references used in some countries).

Related standards

• IEC 60228 is intended as a base reference for IEC cable product standards developed by IEC TC 20. For selection and full applicability, consult the specific cable type standard referenced by IEC or national regulations.