Neutral Grounding Resistor Sizing: Current, Rating and Detection
Wired White v3 Size an NGR from fault current or assess an existing resistor. Check 3·I_c0, hot-current detection, short-time energy and relay grading—and compare with 400 A.
#protection coordination
Wired White v3 
Overcurrent Relay Coordination Calculator: IEEE & IEC TCC
Wired White v3 Plot IEEE and IEC relay curves with CT ratios, instantaneous trips and user fuse points. Screen grading margins and find a candidate upstream time dial and pickup interval.