Earthing and supply in Hartlepool

[Spark123]

Zs must not be measured with the bonding disconnected.
Ze must be measured in isolation, i.e. with the bonding and the exposed conductive parts disconnected to remove any parallel paths. The installation must be isolated whilst this test is carried out and the means of earthing reconnected before the system is energized.
What is the Ze (or Ra) of the electrode?

 

[FingRinal]

Aye, but what about the external parallel paths???

 

[Spark123]

You mean all the parallel paths via the general mass of earth back to the DNO transformer which needs to in itself be bonded to the general mass of earth with a maximum impedance of 21 ohms iirc?
As you get away from the pool around the earth electrode the I don't believe the other parallel paths have a massive effect on the overall reading.

 

[FingRinal]

I suppose you think it's a nice straight line from rod to rod?

 

[Spark123]

Not in the slightest!
Pleanty of different routes of conductance through different types of materials and paths.

 

[FingRinal]

Finally...

 

[Spark123]

Yep, I just don't belive a simple lead pipe can give such a low reading via the general mass of earth. It is more likely connected via MPBs in another premises directly to the transformer via a TN system.
So do we rely on this which may be incidentally connected to a TN system or use the earth electrode?
Is an earth electrode going to give a Ze of less than 0.3 ohms on its own?