Abstract: Methods, systems, and apparatuses are disclosed for reducing geomagnetically-induced currents. The method includes connecting a plurality of switching devices at a neutral grounding connection point of at least one transformer bank. In a system having two terminals, the method includes grounding one transformer bank through a switch so as to reduce geomagnetically induced current. In a system having more than two terminals, the method includes grounding transformer banks through multiple switches, where the reduction is performed independently for each transformer bank. The method further involves determining a switching frequency and a duty cycle based on an evaluation of factors including effectiveness and fault current detection.

Abstract: A transformer assembly comprises at least one transformer having a core. A primary winding is positioned on a first portion, a secondary winding is positioned on a second portion of the core. A neutral winding may be positioned on a third portion of the core. The secondary winding may receive an induced flux produced by an earth surface potential (ESP) via a system ground and/or receive an induced zero sequence flux produced by a non-linear load. The neutral winding may be configured to provide a mitigating flux to the secondary winding. The transformer may also be used as a filter for either GIC or triplen harmonic mitigation. In this case, the primary windings receive the zero sequence current (GIC or triplen harmonics) and the flux may be cancelled in neutral winding such that the zero sequence currents circulate between the zero sequence source and the filter transformer.

Abstract: Methods, systems, and apparatuses are disclosed for reducing geomagnetically-induced currents. The method includes connecting a plurality of switching devices at a neutral grounding connection point of at least one transformer bank. In a system having two terminals, the method includes grounding one transformer bank through a switch so as to reduce geomagnetically induced current. In a system having more than two terminals, the method includes grounding transformer banks through multiple switches, where the reduction is performed independently for each transformer bank. The method further involves determining a switching frequency and a duty cycle based on an evaluation of factors including effectiveness and fault current detection.

Abstract: A transformer assembly comprises at least one transformer having a core. A primary winding is positioned on a first portion, a secondary winding is positioned on a second portion of the core. A neutral winding may be positioned on a third portion of the core. The secondary winding may receive an induced flux produced by an earth surface potential (ESP) via a system ground and/or receive an induced zero sequence flux produced by a non-linear load. The neutral winding may be configured to provide a mitigating flux to the secondary winding. The transformer may also be used as a filter for either GIC or triplen harmonic mitigation. In this case, the primary windings receive the zero sequence current (GIC or triplen harmonics) and the flux may be cancelled in neutral winding such that the zero sequence currents circulate between the zero sequence source and the filter transformer.