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Having dynamic energy storage as an add-on to SVC Light gives the possibility to control both active and reactive power at the point of connection, hence, a possibility to virtually instantly change the operating point within the four-quadrant power area. Fingrid Oyj, the Finnish Transmission System Operator measured the grid frequency during 11 different weeks distributed over a year. These frequency measurements have been analyzed with the purpose of designing suitable battery storage for frequency regulation. A separate power of 500 kW and a state-of-charge (SOC) control loop are needed in order to keep the average SOC level around 50 %. The implementation of a frequency deadband and a SOC control loop maintains the battery within a reasonable SOC band and minimizes the impact of the cycling operation on battery life.