Olkiluoto 3 mixed up the calculations – This is why the border between Finland and Sweden is limited

The electricity market has wondered why the construction of the 800 megawatt Aurora line increased the power of the border connection between northern Sweden and Finland to only 1,900 megawatts, when it was 1,500 megawatts before the Olkiluoto 3 nuclear power plant. When you add the capacity of the new line directly on top of the old one with margins, you can get a capacity figure of up to 2400 megawatts.

In this case, the grid company Fingrid opens the meaning of the power line to Kauppalehti.

Fingrid shoots down the highest expectations

Fingrid’s unit manager Mikko Piironen according to the highest capacity calculation is wrong, because 1,500 megawatts was based on a situation where the Olkiluoto 3 nuclear power plant was not yet operating or was running at low capacity.

With Olkiluoto out of the game, two lines had the opportunity to transfer more electricity from Sweden, because the power increase in the event of a system failure would have been smaller and the lines could withstand more transmission capacity.

When Olkiluoto 3 was operating, the transmission capacity was lowered to 1,200 megawatts, because it was necessary to prepare for a large power spike in the event of a fault situation at Olkiluoto 3.

When Olkiluoto 3 is in use, the system must always be ready for a power drop of 1300 megawatts. A drop would trigger a large transfer elsewhere, and the system must not be overloaded. The network must always withstand the largest single failure.

According to Fingrid, 1,200 megawatts is the correct comparison figure for the current assessment.

The supervisory authority The Energy Agency wholesale market unit manager Jarno Lamponen illustrates: “You always have to be prepared for one of them to go off, so in practice the technical capacity of two people is left.”

Technical capacity

Those with a keen eye can notice that 1900 megawatts is not the full capacity even now, but there is still a margin of safety on top of that, which was increased from 100 megawatts to 200 megawatts in November in connection with the commissioning of Aurora.

A margin of safety is needed so that fluctuations in the transmission power do not lead to exceeding the permitted transmission power.

Piironen says that the safety margin was increased primarily due to the increase in weather-dependent production and the faster fluctuations that occur in the electricity system today.

The calculation method is complicated

In the past, capacity was calculated only in terms of individual lines of cross-border connections. Currently, the factors limiting capacity are calculated according to the flow-based calculation, which takes into account the entire Nordic electricity market area’s electricity network, including the situation in Sweden, more widely than before.

“Now that the capacity is strengthened at the border, the bottleneck can move to another place,” Piironen illustrates.

Piironen says that the capacity of the border connection is no longer necessarily limiting in all situations, but the limiting factor can be the internal network of Finland or Sweden.

Olkiluoto is still the biggest factor, which means that Fingrid has to prepare for the electricity grid to withstand Olkiluoto 3 leaving the grid. There are other failure scenarios: failure of a parallel transmission connection from another network, such as restrictions from Sweden.

In the slide presentation of the Electricity Market Committee, it was reported in December that the driving situation of Olkiluoto 3 no longer has a direct connection with the import capacity. Even in the new calculation, Olkiluoto has not disappeared.

The load can be unevenly distributed among the three wires, because their power transmissions can be different from each other. This may lead to the fact that the capacity given to the market will be lower in the new calculation to ensure operational security.

Possibly an increase in capacity in the future

Investigations into a possible increase in capacity in the future are being initiated, Piironen says.

The Swedish grid company Swedish power grid has indicated that they are currently making investments in northern Sweden, says Piironen. With these, it may be possible to offer the border connection more capacity for use in the future.

I hope within one to two years we will see if the capacity can be increased, says Piironen.

Fingrid’s principle is to always provide the market with the maximum amount of capacity that can be provided reliably, says Piironen.

The minimum amount from EU regulation for electricity transmission capacity is 70 percent. The Energy Agency supervises the realization of this. The agency has confirmed the methods for calculating transmission capacity.

Safety first

The Aurora line brought more transmission capacity, which evens out price spikes.

A transmission connection that increases supply in weak moments is a positive thing for the Finnish electricity market.

Margins of safety are likely to have some price effect, however, as not all supply can be provided, so as not to risk and overload the system.

If there is a transfer restriction between cheap Sweden and more expensive Finland, it will probably increase the price in Finland, and vice versa if Finland is cheaper.

If you think about it in a more fine-tuned way, you can think about whether some kind of weighing needs to be done here between reliability of use and price effects.

Jarno Lamponen, unit manager of the Energy Agency, says that reliability of operation is something that is ensured, and the market operates within the limits of transmission capacities. There is no weighing in that regard. According to him, the grid company must not take extra risk due to the price effect.

The collapse of the power grid is the biggest threat to protect against.