What are the grounding requirements for a LV installation energized from a 100 kVA generator?

[Dvhez]

This is a 230/400 V diesel generator (QAS 100 - 100 kVA). Which standard specify a ground grid resistance value of reference for this kind of installation (isolated)? I was reading IEEE 142 and 4.1.3 "Recommended acceptable values" specify:

"Resistances in the 1 ohm and 5 ohm range are generally found suitable for industrial plants substations and buildings and large commercial installations"

However, I understand that this apply for a installation which is connected to the distribution system. But what would be the value for the case where the system is energized only from a diesel generator?

Thanks!

 

[waross]

This will be a local code issue.
Generally the same grounding as would be required for a similar grid supplied service will be acceptable.
ie: What grounding does your code specify for a 150 Amp service at 400 Volts?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[EricElec]

not sure on the answer, but the logic would be something like this:
Depending on soil conditions, achieving 1 - 5 ohms would not be that easy.
Place a ground loop connected to the transformer at 2 points, 3ft offset for buried loop, add a ground rod / inspection well at one corner and test, add more ground rods if required to achieve desired R value.

 

[waross]

"Resistances in the 1 ohm and 5 ohm range are generally found suitable for industrial plants substations and buildings and large commercial installations"

100 KVA is none of the above.
Fault current will be measured in hundreds of Amps rather than tens of thousands of Amps.

Bill
--------------------
"Why not the best?"
Jimmy Carter