IEC 60228:1966

Specifies standardized nominal cross-section areas from 0.5 mm2 to 2 000 mm2, numbers and diameters of wires and resistance values of conductors in electric cables and flexible cords.
Classifies conductors for:
1) Cables for fixed installations
- Class 1, solid conductors;
- Class 2, stranded conductors.
2) Flexible copper conductors
- Class 5,
- Class 6 (more flexible than Class 5).
Includes table of temperature correction factors kt for conductor resistance to correct the measured resistance at t °C to 20°C.
Does not apply to conductors for telecommunication purposes. Applies to conductors of special design only when stated in the specification for the type of cable. Conductors of special design are, for example. conductors for pressure cables, conductors in extra-flexible welding cables or in special types of flexible cables for having the cores twisted together with unusually short lays. This publication supersedes IEC 180 (1965).
Note: - In this edition, the number of classes of conductors has been reduced from 6 to 4.