2006 European Grid Split
What Happened
A cruise ship called the Norwegian Pearl needed to pass under a high-voltage power line crossing the Ems River in northern Germany. To make room, the operator switched off the line -- a routine procedure they had done before. But this time, the rest of the grid was already under stress from heavy wind power flowing south. (continue below)
When a control room operator tried to fix the growing overloads by changing a switch at a substation, it had the opposite effect. Within 15 seconds, a chain reaction of automatic safety shutoffs split the entire European grid into three separate islands. Around 15 million households lost power, and wind turbines disconnected themselves -- making the problem worse.
Operators resynchronized the grid within 38 minutes, and full normal operations returned about two hours later. No one was hurt, but it was the worst disturbance in European grid history.
Timeline
Root Cause
N-1 security criterion violated. The grid must be able to survive the loss of any single element. After the power line was disconnected for the ship, the remaining system had no safety margin left. A last-minute schedule change (from 1:00 AM to 10:00 PM) prevented neighboring grid operators from running a proper joint security analysis. No single control room had a complete picture of the pan-European grid state.