With an earth-fault loop tester. The maximum values should be:
TN-S: 0.8 ohms
TN-C-S: 0.35 ohms
TT: 20 ohms
If you have a TN-S or TN-C-S (PME) supply you can also ask your DNO for the Ze value, as the supply earth is their responsibility.
Anyway - I thought it was the integrity of the earthing circuit within your installation which concerned you, not your Ze? It's your R1 + R2 you need to be worrying about....
TN-S: 0.8 ohms
TN-C-S: 0.35 ohms
TT: 20 ohms
If you have a TN-S or TN-C-S (PME) supply you can also ask your DNO for the Ze value, as the supply earth is their responsibility.
Anyway - I thought it was the integrity of the earthing circuit within your installation which concerned you, not your Ze? It's your R1 + R2 you need to be worrying about....
