The dimensioning fault in the Finnish power system has increased to 1300 MW

The power system shall continuously withstand a single largest fault i.e. dimensioning fault. In the Finnish power system the dimensioning fault has been 865 MW, which is the size of one Olkiluoto nuclear unit. In Olkiluoto nuclear power plants there has been made a plant modification to electrical protection to ensure nuclear safety, which has changed the behavior of the power plants during grid failures. The Olkiluoto units will reduce their output for a short period after short circuits in the adjacent power grid. Within approximately one minute the output of the units is again back to nearly normal. This has caused an increase of the dimensioning fault of Finland to 1100 -1300 MW depending on the operational situation on Finnish south-western coast area. As a consequence of this import capacity from Sweden to Finland has been decreased 100 - 300 MW respectively. Prevailing import capacity is thus 1750 - 1950 MW.  This will not affect the export capacities from Finland to Sweden. The exact capacities will be updated daily according to the operational situation and will be published on NordPool  Spot web page . TVO, the owner of the Olkiluoto nuclear plants, is together with Fingrid investigating actions, which will enable return to the previous level of dimensioning fault.    Further information: 
Timo Kaukonen, puh.+358 30 395 4228, +358 40 545 2124
Reima Päivinen, puh. +358 30 395 5160, +358 40 556 2662