A 100-year Geoelectric Hazard Analysis for the U.S. High-Voltage Power Grid

Abstract:

The U.S. power grid is susceptible to geomagnetically induced currents (GICs) induced by magnetic storms. The GICs result from the complex interplay between the inducing magnetic field and the electrically resistive solid Earth. To calculate historical geoelectric fields and induced voltages on transmission lines, we combine 31-years of geomagnetic field data with 1,079 long-period magnetotelluric survey sites covering about 2/3 of the contiguous U.S. We identify 84 large magnetic storms (using the Kp and Dst indices) and calculate peak geoelectric fields and voltages during each storm. Using these peak values, we then statistically extrapolate the 31-year history to estimate once-per-century geoelectric hazards that could plausibly be realized in the U.S. high-voltage power grid. The once-per-century geoelectric hazards span 3 orders of magnitude from 0.02 V/km at a site in Idaho to a maximum of 27.2 V/km at a site in Maine, with nearly 30% of the surveyed land area exceeding 1 V/km. High geoelectric hazard regions are concentrated in regions of high surface impedance, primarily in the northern Midwest and Eastern United States. This work underscores the important role of the solid-Earth in affecting geoelectric hazards. Work of this type can also be facilitated by a new Data Portal developed at the University of Colorado’s Space Weather Technology Research and Education Center (SWx TREC).