Probably larger than that. If they’re 200m from the transformer, 400A service requires (3) 1000kcmil cables per leg. 100m drops it to (3) 350kcmil which is stil

Probably larger than that. If they’re 200m from the transformer, 400A service requires (3) 1000kcmil cables per leg. 100m drops it to (3) 350kcmil which is still pretty beefy