There isn't a single "standard" size, as it depends on the specific project. However, common sizes are measured in cross-sectional area (mm²) and include:

• For medium-load distribution: Conductors in the 50mm² to 100mm² range are frequently used. These sizes provide a good balance of current capacity and mechanical strength for typical distribution lines.

• For high-load distribution and sub-transmission: For applications that require more power transfer, such as feeding a large industrial area, sizes in the 120mm² to 200mm² range are common.

• For heavy-duty applications: For very long spans or heavy current loads, sizes can go up to 300mm² or even larger.

The exact size is always specified by an engineer based on the line's design parameters.