Connecting an earth wire to distribution board
basically the earth path provides a low resitance path for safety and if supplier has supplied an earth already in the incoming supply should be sufficient . RCD protection monitors live /neutral and will trip when unbalanced ..connecting an earth spike to earth terminal if instalation already earthed makeslittle to no difference as it is the loop resistance path that is imporatant and a local electricain should be able to carry out a loop impedence (z) test to confirm path is fine.