Histograms of the 30-min maximum of the GIC sum divided by the number of nodes in the Nordic high-voltage power grid for different ranges of |dH/dt|₃₀ at UPS. For example, the upper left plot shows the distribution when |dH/dt|₃₀ varies between 6 and 23 nT/min which correspond to the percentile limits of 90% and 99%, respectively. The total number of 30-min values in 1996–2008 is 227,952. The largest value of GIC₃₀ is 38.9 A.