IEC 60888:1987

Applies to zinc-coated steel wires used in the construction and/or
reinforcement of conductors for overhead power transmission
purposes, and is intended to cover all wires used in construction
where the individual wire diameters, including coating, are in the
range of 1.25 mm to 5.50 mm.
Three grades of steel are included to reflect the needs of
conductor users: regular steel, high strength steel and extra high
strength steel.
Two classes of coating represented by minimum zinc mass per unit
area are included: Class 1 and Class 2.