It seems that the Federal government is finally taking this threat seriously.
On September 12, 2012, Joseph McClelland, Director, Office of Electric Reliability, Federal Energy Regulatory Commission, testified before the House Committee on Homeland Security, Subcommittee on Emerging Threats, Cybersecurity, and Science and Technology. His testimony was about the consequences of an EMP (Electro Magnetic Pulse) event, either naturally occurring, or man-made.
See the testimony transcript here, on the Federal Energy Regulatory Commission site:
On the forth page of the testimony, under the heading of "Physical Security and Other Threats to Reliability", is an excellent summary of the three types of EMP events that can cause instability on the electric grid:
1. Man-made EMP event, used as a weapon.
2. EMP event caused by lightening.
3. EMP event caused by solar activity (solar flares)
Electrical disruptions caused by lightening are already well mitigated by industry, but there's virtually no commercial or wide-spread protection against man-made or solar EMP events.
Interestingly enough, mitigation against solar EMP events is also effective against man-made EMP events.
I'm not much of an "End Of The World" person, but out of all of the disaster scenarios, a catastrophic, EMP induced, power outage is the most likely and realistic wide-spread disaster.
On September 1,2 & 3, 1859, the largest recorded geomagnetic storm in recorded history occurred, following a massive solar flare and coronal mass ejection (CME).
There were virtually no electronics in 1859 except telegraph systems. Telegraph pylons and wires, all over the country, threw sparks and telegraph paper spontaneously caught fire. Telegraph operators reported that their systems continued to send and receive messages, AFTER they were disconnected from power supplies. Aurora borealis sightings were reported as far south as the Caribbean.
This was known as the Carrington Event, named after Richard Carrington, the astronomer that observed and reported the massive solar flares. Look it up.
More recently, on March 13, 1989, a severe geomagnetic storm caused the collapse of the Hydro-Québec power grid - in a matter of seconds - as protective electronic relays tripped, in a cascading sequence of events.
Six million people were left without power for nine hours.
Another recent event, on Valentines Day 2011, solar flares caused disruption to radio communications and GPS signals for airplanes on long-distance flights.
An EMP event today, as big as the Carrington Event, could cause a massive power outage across more than 50% of the continental US.
The U.S. Air Force Research Laboratory determined the eastern half of the U.S. is particularly vulnerable, because the power infrastructure is highly interconnected, so failures could easily cascade into a wide-spread catastrophic power outage. Large cities could be without power for a week, a month, or a year, with economic losses between $1 to $2 trillion, with recovery times from 4 to 10 years.