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When Space Weather Attacks Earth
Lasrick writes "Brad Plumer details the 1859 solar storm known as the Carrington Event. Pretty fascinating stuff: 'At the time, it was a dazzling display of nature. Yet if the same thing happened today, it would be an utter catastrophe...That's not a lurid sci-fi fantasy. It's a sober new assessment by Lloyd's of London, the world's oldest insurance market. The report notes that even a much smaller solar-induced geomagnetic storm in 1989 left 6 million people in Quebec without power for nine hours.'"
The last time someone got wound up about this on Slashdot. And, last time around, I linked the PJM power grid training document on geo-magnetic disturbances. They know about the Carrington Event. They know all about the problem in 1989, which happened on their system and damaged some transformers.
The problem shows up as DC current on long AC lines, because voltage at "ground" differs across points hundreds of miles apart. This can damage transformers. So they have DC current monitoring in place at some key points on their system. Corrective action is taken when "DC measurement of 10 amps or greater measured at Missouri Avenue in Atlantic City and/or Meadow Brook Station near Winchester Virginia". Some long-distance lines have to operate at reduced capacity. Some generating plants are told to reduce output. Others have to crank up to compensate.
Medium sized disturbances of this type happen a few times a year (more at the high point of the sunspot cycle). Only one warning so far this year, on June 29th. April 11, 2010 was the most recent disturbance event that required that action be taken. The warning came in from NOAA's Space Weather Center, and people in power grid control centers (the US has seven) reconfigured the power grid to prepare for it.