Abstract: A countermeasure for mitigating Electromagnetic Pulse E3 (EMP-E3) induced currents flowing through the neutral of a star-connected three-phase power transformer without compromising its neutral end insulation performance. It comprises an external neutral-grounding device; a first linear resistor (R10) is connected from the transformer neutral (N) to ground (G) sized to render said induced currents, for any given EMP-E3 severity, reduced and inconsequential to the equipment operation. Contingently, a second non-linear neutral-grounding resistor (R11) provides a shunting path-to-ground of substantially low resistance, as prevailing by virtue of its non-linearity under large power system fault currents; such a bypass functionality is formulated/designed according to IEEE/ANSI/NEMA recommended insulation coordination guidelines in order to sustain proper protective margins to the equipment neutral basic insulation levels (BIL/BSL).

Abstract: A countermeasure for mitigating Electromagnetic Pulse E3 (EMP-E3) induced currents flowing through the neutral of a star-connected three-phase power transformer without compromising its neutral end insulation performance. It comprises an external neutral-grounding device; a first linear resistor (R10) is connected from the transformer neutral (N) to ground (G) sized to render said induced currents, for any given EMP-E3 severity, reduced and inconsequential to the equipment operation. Contingently, a second non-linear neutral-grounding resistor (R11) provides a shunting path-to-ground of substantially low resistance, as prevailing by virtue of its non-linearity under large power system fault currents; such a bypass functionality is formulated/designed according to IEEE/ANSI/NEMA recommended insulation coordination guidelines in order to sustain proper protective margins to the equipment neutral basic insulation levels (BIL/BSL).