The situation began on 18 July when a current transformer at Fingrid’s Olkiluoto substation was damaged and caused a fire. During the resulting fire and substation repair work, both of Olkiluoto’s nuclear power plant units 1 and 2 were disconnected from the grid.
In the morning of 19 July, Fingrid issued a warning that domestic electricity production and import might not be sufficient to cover electricity consumption and that an electricity shortage situation was possible.
Balancing assistance from producers, consumers and neighbouring countries
The disturbances caused voltage dips extensively in the main and distribution grids. Olkiluoto 1 was without 400 kV main grid voltage for some 24 hours and Olkiluoto 2 for more than 39 hours.
Fingrid started up a reserve power plant for about one hour when the Olkiluoto 1 nuclear power plant unit connection to the main grid was interrupted.Electricity producers and consumers participated actively in balancing the situation and additional electricity was obtained from neighbouring countries. Olkiluoto 1 was reconnected to the main grid late in the evening on 19 July and Olkiluoto 2 just after 7 am on 20 July, which is when the situation returned to normal.
Repairs were completed quickly. According to existing plans, the A switchyard will be completely replaced by a new switchyard next year.
Categories describe electricity shortage levels
Three-step scale for electricity shortage
Situations related to managing electricity shortages are divided into three levels based on severity:
Electricity shortage possible
When domestic production and imports are not expected to be sufficient to cover electricity consumption within the next few hours or 24-hour period. Fingrid may have to start up reserve power plants to the extent that Fingrid is no longer able to maintain a sufficient amount of fast disturbance reserve (= increase of production or decrease of consumption which can be activated within 15 minutes) in Finland.
Serious risk of electricity shortage
When all of the electricity production available in Finland is in use and it is not possible to import more electricity from neighbouring countries. Fingrid has had to start up reserve power plants to secure the electricity supply to the extent that Fingrid is no longer able to maintain a sufficient amount of fast disturbance reserve in Finland.
An electricity shortage is considered to have occurred when electricity production and imports are not enough to cover consumption and some electricity consumption has to be switched off. Distribution system operators switch off consumption according to instructions from Fingrid so that power outages last no more than two hours and outages are not targeted at society’s key functions.
Prior to the Olkiluoto case in July, Fingrid had used the first stage of the electricity shortage procedure five times during the 2000s. Four of these cases occurred in the period of 19–20 January 2006 as a result of extremely cold temperatures throughout the country. The first stage was used for the fifth time on 5 January 2008 when Olkiluoto 2 went off the grid.