Impact of Olkiluoto 3 on transmission capacity given to electricity market between Finland and Sweden on northern interconnections
Olkiluoto 3 nuclear power plant is after commissioning the largest power plant in Finland and Fingrid is prepared for the disturbance of the unit all the time. The deficit in Finland arisen during the disturbance will be covered mainly by automatic regulated electricity from Northern Sweden through 400 kilovolt AC-interconnections. This will be implemented by reserving part of the transmission capacity on northern interconnection for the nuclear power plant trip. When the largest unit in Finland increases in size, 300 megawatt more of the import capacity has to be reserved. The increase of plant size does not have impact to the export capacity.
OL3 system protection has been implemented to limit the impact of Olkiluoto 3 on the electricity system. OL3 system protection limits the impact of a sudden loss of Olkiluoto 3 power production to 1300 megawatt.
The import capacity given to electricity market depends in the future on Olkiluoto 3 nuclear power plant electricity generation. When Olkiluoto 3 produces electricity with full power, i.e. around 1600 megawatt, the transmission capacity from Northern Sweden to Finland is at the maximum 1200 megawatt, but if the Olkiluoto 3 generation is below 1000 megawatt, the transmission capacity from Northern Sweden to Finland is at the maximum 1500 megawatt.
Principles for determining and publishing the transmission capacity
Fingrid gives to the electricity market the maximum transmission capacity at FI-SE1 interconnection for each operational situation and publish market messages of the capacity changes. Depending on the situation, Fingrid updates both day-ahead and intraday transmission capacities.
The change of FI-SE1 day ahead transmission capacity is always based on Olkiluoto 3 market information and the estimated rate of change of Olkiluoto 3 production.
The FI-SE1 intraday transmission capacities are determined based on Olkiluoto 3 market messages, Olkiluoto 3 production schedules and possible other information about the operational situation of the main grid.
Examples of the changes of the transmission capacity
Example 1: Olkiluoto 3 electricity production is at least 1000 megawatt and it disconnects unexpectedly from the main grid due to, for example, a disturbance.
Fingrid publishes market message and increases the intraday transmission capacity at FI-SE1 interconnector immediately after the disturbance. Market messages and the transmission capacities are updated based on Olkiluoto 3 market messages.
Esimerkki 2: Olkiluoto 3 connects to the grid and increases its production to at least 1000 megawatt.
Fingrid reduces the transmission capacity at FI-SE1 interconnector based on Olkiluoto 3 market messages. FI-SE1 transmission capacity is reduced since Olkiluoto 3 production reaches 1000 megawatt. If this time is not given in Olkiluoto 3 market messages, Fingrid will estimate the time by applying the estimated rate of change of Olkiluoto 3 power production.
Example 3: Olkiluoto 3 market messages states that the available capacity of the power plant is below 1000 megawatt due to, for example, a fault or revision.
Fingrid increases the transmission capacity at FI-SE1 based on the Olkiluoto 3 market messages. The transmission capacity is increased since Olkiluoto 3 production is below 1000 megawatt.
Example 4: Olkiluoto 3 production is below 1000 megawatt but there are no market messages concerning the reduced capacity.
The Olkiluoto 3 market messages about the available production capacity (at least 1000 megawatt) are still effective. Fingrid will increase the intraday transmission capacity of FI-SE1 interconnector based on Olkiluoto 3 production schedules and other information about the operational situation of the main grid. Fingrid publishes market messages about the transmission capacity changes. Fingrid will not increase the day ahead transmission capacity of the FI-SE1 interconnector.
Timo Kaukonen, Fingrid Oyj.
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