Blocking Device Placement for Mitigating the Effects of Geomagnetically Induced Currents

Geomagnetically induced currents (GICs) can cause half cycle saturation of transformers and consequently affect the power grid with harmonics and reactive power losses. To effectively mitigate the negative GIC impacts in large-scale power systems, the present paper considers the problem of placing blocking devices in transformer neutrals. The placement problem of multiple blocking devices is first considered by analytically quantifying the associated reactive power losses. A linear sensitivity analysis is further provided for the case of blocking a single transformer, and it has been observed that the effects of blocking transformer neutral currents to be mostly local. This motivates us to propose the scheme that selects multiple substations to block all high voltage level transformers therein, based on a linearized approximation model. The effectiveness of such scheme has been demonstrated using both a 20-bus GIC test case and a realistically sized larger power system.