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Geomagnetic Disturbances (GMDs), Geomagnetic induced currents (GICs), and their impacts on bulk power systems have been of interest to power engineers since the 1960s. However, interest has been heightened recently, and articles in The Wall Street Journal, National Geographic, and IEEE Spectrum have predicted widespread transformer failures and prolonged global power outages. While these articles provide thought-provoking perspectives, they have not offered a scientific and engineering analysis of the many complex issues that determine power system impacts. The purpose of this article is to: provide a technical review of GMDs/GICs, with emphasis on impacts to the power grid and power transformers review detection and measurement of GMDs/GICs and how information is communicated to grid operators discuss various approaches to mitigate the potential impacts on power systems describe industry efforts for technological advancement to address GIC issues.