Record low inertia in the Nordic power system

The lowest inertia in metering history was measured in the Nordic power system on Sunday 13 June between 2 pm and 3 pm.

Inertia is needed in the power system in order to maintain the balance between electricity production and consumption in the event of sudden faults at power plants and in transmission connections. During times of low inertia, a fault at a large electricity production unit or in the direct current transmission link may cause a larger than normal instantaneous frequency deviation. The frequency deviation must not become too large so as not to compromise the security of the power system.

Inertia is typically at its lowest when there are few conventional power plants connected to the power system, there is considerable wind and solar power, and electricity imports via high-voltage direct current transmission links are high. Situations of low inertia typically occur during the summer season.

On Sunday 13 June, a situation arose in the Nordic power system in which many nuclear power units were undergoing annual maintenance at the same time, electricity imports via HVDC transmission links were high, and a large amount of wind power was being generated. These factors contributed to the development of low inertia. The inertia measured between 2 pm and 3 pm was 110 GWs, with inertia typically varying between 120 GWs and 280 GWs.

Nordic transmission system operators have prepared for situations of low inertia by procuring Fast Frequency Reserve, as a result of which the situation did not pose a risk to the security of the power system.

Situations of even lower inertia are expected to occur in the future, and more frequently than before. The reason for this particularly rests in the increase in the share of wind and solar power in electricity production.

Read more about inertia and the Fast Frequency Reserve on the Fingrid website


Further information:
Senior Vice President Reima Päivinen, Fingrid, tel. +358 30 395 5160
Expert Mikko Kuivaniemi, Fingrid, tel. +358 30 395 5188