From the pdf…..
For example, a 10 kiloton weapon detonated at 30 kilometers over the U.S. Eastern Grid would
generate a HEMP field over about 600 kilometers in radius, much smaller than the Eastern Grid.
But the national electric grid being aged, over-taxed with demand, and often operating on the verge
of failure, is capable of blackouts that put 50 million people into the dark because of cascading
failures from a tree branch (like the Great Northeast Blackout of 2003), the entire Eastern Grid
would certainly be plunged into a protracted blackout from such an HEMP attack. The U.S. cannot
survive without the Eastern Grid which generates 75 percent of the nation's electricity and supports
most of the national population.36