Blocker of geomagnetically induced currents (GIC)

摘要

A device for mitigating Geomagnetically Ground Induced Currents (GIC) flowing from the neutral of a star-connected three-phase power transformer to ground without compromising its basic insulation, operation or integrity. Resistor (R10), of an adaptive non-linear negative volt-ampere characteristic is inserted, from the transformer neutral (N) to ground (G), by opening the ground switch (S1) depending on its DC flow magnitude. Such an insertion to render said induced currents, for any given GMD severity, blocked and inconsequential to the equipment because of (R10) very large resistance prevailing at that condition. Conversely, under a hypothetical and rare simultaneous large power system fault currents, (R10) non-linear negative volt-ampere characteristic becomes very low ohmic and thus an expeditious protective bolted path to ground; all process 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).

主权项

1. A passive external resistive neutral grounding device tapped at the neutral of a star connected three phase winding of a power transformer to protect it by substantially blocking the flow of harmful Ground Induced Currents from a Geomagnetic or Electromagnetic Pulse Disturbance through said transformer without compromising said transformer neutral end insulation operation or integrity.