question 1000Kva xmfr 208Y/120V-3ph, 4w secondary the conductors from the xfmr. to the secondary OCPD are indicated to be 8-sets of 500's with a 4/0 ground in each (3/0 required), they land in a single switchboard section with a 3000A circuit breaker from there underground to the main switchboard there are 8-sets of 500's but this time with a 500kcmilm(400kmin required), my question is what is the difference between the line and load side that there is such a dramatic change in ground conductor size??