Always verify your installation against the specific national wiring regulations applicable in your country (e.g., NEC in the US, BS 7671 in the UK, AS/NZS 3000 in Australasia), as local amendments may impose stricter requirements than the general IEC standards.
Based on Table 54.7 of IEC 60364-5-54 (simplified). Always verify with local regulations and fault current calculations. earth conductor size table
The tables above apply to circuit protective conductors (the ground wire inside your cables). However, the (the wire connecting your consumer unit/switchboard to the ground rod/plate outside) has different requirements. The tables above apply to circuit protective conductors
An earth conductor size table, also known as an earthing conductor size table or grounding conductor size table, is a reference chart used to determine the minimum size of an earth conductor (also known as a grounding conductor or earthing lead) required for electrical safety. NEC in the US