Lessons Learned

Analysis of Misoperations of Protection Schemes in the Nordic Grid - 1st of December 2005

On the 1st of December 15:02 (CET) a fault on a 420 kV breaker at the Swedish Porjus power plant correctly triggered the breaker failure protection, and the 420 kV busbar at Porjus power plant was disconnected. This led to the remaining power transfer corridor out of northern Scandinavia getting overloaded. The overloading should have led to instantaneous triggering of a system protection scheme to limit the damage. However the system protection scheme did not work as intended. The malfunction of the system protection scheme led to two major islands in the Norwegian grid, and 2450 MW of generation, disconnecting from the Nordic grid.


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