I would like to install a 120/240 volt 100 amp sub panel on a detached garage that is about 200 ft away. I have read that one should strive for a voltage drop of less than 3% and from what I can tell this means I need #2 cu or 1/0 al for the two hot and neutral. What I'm having a hard time determining is if the ground wire to the sub panel needs to be the same size or if it can be smaller. I've read that the ground for a 100 amp sub panel needs to be #8 cu or #6 al but don't I need to take the long distance into account?
I really appreciate any help on this!
Edit: Thank you Harper for pointing out that the 3% rule applies to expected loads, not the supply breaker size. Given my expected use I can probably go with slightly smaller wires for the two hot and nuetral. However I still have the same question about how to size the ground wire.