relay (51N)† sees all of the ground current and can be set without regard for load current. As
the grounding impedance increases, the fault current decreases and it becomes more difficult to
set a current-type relay. The lower the relay pickup, the higher is its burden on the CT and the
more difficult it is to distinguish between ground faults and normal third harmonic unbalance. This
unbalanced current that flows in the neutral can be as much as 10–15% of the rated current. Other
spurious ground current may flow due to unbalances in the primary system. The total false ground