Inertia of the Nordic power system


Inertia is the ability of a power system to oppose changes in frequency due to resistance provided by the kinetic energy of rotating masses connected to the system. During times of low inertia, large sudden power imbalance, for example due to a sudden disconnection of a large production unit, causes large instantaneous frequency deviation. Whereas during times of high inertia, the instantaneous frequency deviation is small. The Nordic transmission system operators estimate the kinetic energy of the Nordic power system (Finland, Sweden, Norway, eastern Denmark) using the real-time telemetry of individual generators.

The data represents the total kinetic energy of the Nordic power system as the behavior of frequency is primarily influenced by the total kinetic energy of the system. The kinetic energy of the Nordic power system typically varies between 120 GWs and 280 GWs. When the kinetic energy is close to 130 –140 GWs, the Nordic transmission system operators may need to perform remedial actions like limit the largest possible power imbalance caused by a single fault. This is done to prevent the instantaneous frequency deviation from becoming too large.

More information on inertia is available in the Fingrid magazine.


Minna Laasonen

Senior Expert
tel. +358 30 395 5293

Mikko Kuivaniemi

tel. +358 30 395 5188