Do we have an electrical engineer to comment?
Field strengh decreases by the square of the distance. In addition, the grid is not a perfect antenna and would only absorb a fraction of the EMP pulse. In addition, there are multiple ground safeties designed to take lightening pulses to the ground.
Although I have no doubt an air burst would take out regional power, I’m not sure a N. Korea sized nuke exploding in space has the ability to take out the entire U.S. grid.
Anyone here familiar with the math?
Rise time of lightning is much longer than rise time of a nuke-induced EMP. IIRC. So, breakers designed to protect against lightning might not trip in time to protect against EMP.
I'm an EE, but power grids are not my specialty.