Are we talking about the grounding electrode conductor, or equipment grounding conductors here.
The size of grounding electrode conductors is based on the size of the largest ungrounded service conductor. Equipment grounding conductors are sized based on the rating of the overcurrent protective device ahead of the conductors. In the case of upsizing branch circuits and feeders to allow for voltage drop, yes the equipment grounding conductor must also be increased by the same percentage. For grounding electrode conductors see table 250-66
[This message has been edited by macmikeman (edited 08-17-2006).]
