Sel SEL-387A - Page 3

Overcurrent Elements Page 3 of 7 20120723
Step 4
Determine the Neutral Inst Overcurrent Trip Level setting.
50NN21P = ________________
Set the 50N element to 50 percent of the maximum ground fault current. Obtain the maximum value from
a system fault study.
For this example, assume a 5,000 A ground fault current.
Step 5
Verify that the Neutral Inst Overcurrent Trip Delay (50NN1D) is set at minimum value of 0.50.
Step 6
Select Group 1 > Set 1 > Winding 2 Elements.
Figure 3 Phase Time-Overcurrent Element Settings
Step 7
Determine the Winding 2 Phase Time Overcurrent Trip Level setting.
51P2P = __________________
Set the phase time-overcurrent element to 150 percent of the continuous rated amperes.
Step 8
Set the Winding 2 Phase TOC Curve Selection to coordinate with the downstream time-overcurrent
protection.
51P2C = __________________