PME or TT or Both To Caravan Or Outbuilding

[Ian1981]

I'm not sure that it is an acceptable method of measuring Ra, because it does not measure Ra, it measures the earth loop impedance including the earth electrode.

Either way I didn't suggest that it was not an acceptable test method, I asked if this method had been used or if a better method had been used.

If he's made one end tt and disconnected the supply earth then yes he is measuring Ra

That's if he's disconnected it from the pme earthing

 

[davesparks]

If he's made one end tt and disconnected the supply earth then yes he is measuring Ra

That's if he's disconnected it from the pme earthing

No, with a loop impedance tester he will be measuring the combination of Ra and the loop,impedance of the supply.
Ra is the resistance to earth of the earth electrode, it does not include the line conductor.

 

[Ian1981]

No, with a loop impedance tester he will be measuring the combination of Ra and the loop,impedance of the supply.
Ra is the resistance to earth of the earth electrode, it does not include the line conductor.

The earth fault loop impedance tester is connected between line conductor at the source of the installation (not in this case) and the earth electrode, and a test performed.
The impedance reading taken is treated as the electrode resistance.

Taken from GN3
So yes not as accurate as an electrode tester but is the method we can use to obtain Ra

 

[bigspark17]

It is a hard wired static caravan not a caravan park.

ESQCR staturtory reg still aplies, the pme earth cannot be used!

 

[davesparks]

The earth fault loop impedance tester is connected between line conductor at the source of the installation (not in this case) and the earth electrode, and a test performed.
The impedance reading taken is treated as the electrode resistance.

Taken from GN3
So yes not as accurate as an electrode tester but is the method we can use to obtain Ra

You are contradicting yourself.
You say it is treated as the electrode resistance, which is fine, but this does not make it Ra.
Ra is a defined quantity, the method you describe results in an approximation, not a measured value, of Ra.

You might as well be stating that g is 10 or that c is 300,000,000
Both are approximations and not the actual values.

 

[Ian1981]

You are contradicting yourself.
You say it is treated as the electrode resistance, which is fine, but this does not make it Ra.
Ra is a defined quantity, the method you describe results in an approximation, not a measured value, of Ra.

You might as well be stating that g is 10 or that c is 300,000,000
Both are approximations and not the actual values.

Whatever you say dave.........