Installing 60Kva generator.

[Ian1981]

It is the neutral to earth link, it is the link which references the neutral to the general mass of earth.
And yes it is not a TT system, it is a TNS system which you are creating.

200ohm is not the value we would use on a TT arrangement, that is a misinterpreted suggestion from the regulations on what may be a limit of stability in some situations.

The resistance of the installation electrode should be as low as practicable a value of exceeding 200 ohms may not be stable
Table 41.5 note 2 bs7671.
200ohms is the adopted figure used I would say!
If you want to be percise it is RA x Idelta N equal to or less than 50v which I'm sure you know this.
If I'm incorrect about the earth neutral link then hey I stand corrected

 

[Ian1981]

The resistance of the installation electrode should be as low as practicable a value of exceeding 200 ohms may not be stable
Table 41.5 note 2 bs7671.
200ohms is the adopted figure used I would say!
If you want to be percise it is RA x Idelta N equal to or less than 50v which I'm sure you know this.
If I'm incorrect about the earth neutral link then hey I stand corrected

When using an rcd for fault protection purposes

 

[davesparks]

The resistance of the installation electrode should be as low as practicable a value of exceeding 200 ohms may not be stable
Table 41.5 note 2 bs7671.
200ohms is the adopted figure used I would say!
If you want to be percise it is RA x Idelta N equal to or less than 50v which I'm sure you know this.
If I'm incorrect about the earth neutral link then hey I stand corrected

'May not be stable' that does not mean that it is a suggested value, maximum value or even that a value less than it is stable.
'As low as practicable' does not mean that you are aiming for a particular value, it means getting it as low as you practically can, which in most cases is a lot less than 200 ohms.

I do know about that calculation, but there are more factors to consider, for example if you read the instructions for a Schneider rcbo they state a maximum Zs for the protected circuit of 100ohms.

the generator as supplied will have a link which connects the star point of the alternator to the case of the generator, this is not a neutral to earth link as there is no connection to earth and it for small an IT supply. By connecting the star point to the general mass of earth it can be turned in to a TNS supply.

 

[Ian1981]

'May not be stable' that does not mean that it is a suggested value, maximum value or even that a value less than it is stable.
'As low as practicable' does not mean that you are aiming for a particular value, it means getting it as low as you practically can, which in most cases is a lot less than 200 ohms.

I do know about that calculation, but there are more factors to consider, for example if you read the instructions for a Schneider rcbo they state a maximum Zs for the protected circuit of 100ohms.

the generator as supplied will have a link which connects the star point of the alternator to the case of the generator, this is not a neutral to earth link as there is no connection to earth and it for small an IT supply. By connecting the star point to the general mass of earth it can be turned in to a TNS supply.

The 'calculation ' is from bs 7671 RA sum of resistance of electrode and associated cpc stating that the total resistance x by say a 30mA rcd cannot be greater than the recommended 50v touch voltage.
Ideally get the electrode as low as possible i never said there was a magic number to aim for other than what is recommended in the on suite guide, the NICEIC guidance for installations upto 100amps guide and note 2 from bs 7671.

Never seen rcbo instructions for Schneider rcbos I'll have to take your word on that tho it maybe the manufacturers guidance I fail to see if the resistance is greater than 100bohms has got to do with it as the max zs associated with an 30mA rcbo would be 1667 ohms!
Unless the rcbo won't work over 100 ohms in which case remind me never to use Schneider!

 

[PEG]

This thread has gone AWOL from the OP's original ask...