Prediction of geomagnetically induced currents (GICs) flowing in Japanese power grid for Carrington-class magnetic storms

Large-amplitude geomagnetically induced currents (GICs) are the natural consequences of the solar-terrestrial connection triggered by solar eruptions. The threat of severe damage of power grids due to the GICs is a major concern, in particular, at high latitudes, but is not well understood as for low-latitude power grids. The purpose of this study is to evaluate the lower limit of the GICs that could flow in the Japanese power grid against a Carrington-class severe magnetic storm. On the basis of the geomagnetic disturbances (GMDs) observed at Colaba, India, during the Carrington event in 1859, we calculated the geoelectric disturbances (GEDs) by a convolution theory, and calculated GICs flowing through transformers at 3 substations in the Japanese extra-high-voltage (500-kV) power grid by a linear combination of the GEDs. The estimated GEDs could reach similar to 2.5 V/km at Kakioka, and the GICs could reach, at least, 89 +/- 30 A near the storm maximum. These values are several times larger than those estimated for the 13-14 March 1989 storm (in which power blackout occurred in Canada), and the 29-31 October 2003 storm (in which power blackout occurred in Sweden). The GICs estimated here are the lower limits, and there is a probability of stronger GICs at other substations. The method introduced here will be immediately applicable for benchmark evaluation of low-latitude GICs against the Carrington-class magnetic storms if one assumes electrical parameters, such as resistance of transmission lines, with sufficient accuracy.