The standard doesn't just define sizes; it sets strict limits on: Maximum Resistance
A single wire used for fixed installations where rigidity is acceptable. It offers the lowest resistance and cost.
If you need a specific piece of information from the standard, I can help you find it.g., 2.5 mm2m m squared mm2m m squared
This is the core requirement. For instance, a 10 mm² Class 2 copper conductor must not exceed a resistance of 1.83 Ω/km .