How to size earth conductor of three phase generator

[ronpoh]

75kva 3phase
Maxcurrent per phase 108A
Outgoing feeders from genset 4C 35mmsq cable + 16mmsq CPC

Earth conductor from genset earth point to earth electrode = 50mmsq

Question: why 50mmsq? Isnt 16mmsq sufficient since cpcs are sized at S/2 half of phase conductors. Are earth conductors to earth roads sized differently?

 

[old_sparky_RE]

Yes they are. If I've read your question correctly then Table 54.1....... Min CSA of a burried earthing conductor.

16mm if protected against corrosion and not protected against mechanical damage
50mm if no protection at all for earthing conductor (bare copper cable/tape)

 

[Farmelectrics]

Question has the earthing for a generator got to be separate from the building earth

 

[Knobhead]

Is this a standby generator or the sole source of supply? If it’s a standby you can not use the DNO’s earth as the generator earth. They can be connected but not be the sole earth point therefore an earth spike is required. This is to protect DNO personnel working on the network. The earth CPC must be sized as above.
Again if it’s a standby the requirements for safe change over must be met.

 

[Engineer54]

Just to add, as it's important to note ....that a 200 ohm Ra on an earth rod(s) that is being used to earth a neutral either on a generator or a Transformer, just ain't gonna cut it. So you can forget using those short 3/8'' spikes...