Determination of the required secondary control reserve and minute reserve

All four German TSOs jointly estimate the secondary control reserve and minute reserve to be maintained for the entire German grid area. This involves a probability-based approach, verified by experts under orders of the Federal Network Agency. The results apply to the entire German control area.

Each quarter, the reserve size for the next quarter is estimated based on the four previous quarters. The following fundamental input values are taken into account.

  • Power plant failures: this value is based on the statistical blackout probability per type of power plant. Only those power stations with a capacity of 100 MW and higher are included.
  • Load fluctuation: the difference between the instantaneous load and feed-in values and their quarter-hourly averages is determined for a representative period at the end of every 2-year cycle and included in the subsequent reserve size calculations (dimensioning).
  • Schedule shifts: the cross-border schedules agreed between the four German control areas and other countries are taken into account, always using the four previous quarters' data to estimate the reserve size for the next quarter.
  • Forecast errors: the quarter-hourly average of the actual control reserve needed in the four German control areas is also used to determine the size of the reserve. This value is composed of the activated secondary control reserve and minute reserve, any necessary additional measures, the energy volumes exchanged within the IGCC framework and the residual balance deviation of the 4 German control areas, e.g. due to insufficient balancing power.

Details on the dimensioning process are available in the 2nd follow-up report on the level of balancing energy required in 2010, published on the Federal Network Agency's website:

Determination of the required primary control reserve

The primary control reserve (PCR) to be maintained under the German grid control cooperation is agreed annually between the transmission system operators (TSOs) of continental Europe. This is based on a total need of ±3000 MW PCR for the synchronous area, divided among the TSOs in proportion to the yearly feed-in.

Detailed information is available in Policy 1 of the ENTSO-E Operation Handbook of the Regional Group Central Europe.

Overview of the historical reasons for changes in the required control reserve as of 2012