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It is difficult to store large amounts of electrical energy. Consequently the consumption of electrical energy should be equal to the production at any time. Load forecasts are used to coordinate the infeed of power plants.That is why every producer and every load have to be part of a balancing group. The balance responsible party (BRP) is required to ensure that there is no gap between production and consumption in his balancing group. Otherwise frequency deviations emerge and may decrease the system security.

The balance of all balancing groups amount to the system imbalance. It appears in a deviation of forecasted and realised import/export. For using as less balancing energy as possible, the system imbalances of the german TSO get balanced and afterwards minimized in the IGCC (regard the infobox). 50Hertz balances the resulting system imbalance with balancing energy.

It has to be possible to activate control energy immediately. For this reason, the provision of this energy is subject to a call for tenders and laid down in a binding contract with the providers (balancing capacity). No power flows until the provided capacity is actually required and activated (control energy). In order to maintain system balance at all times, the German transmission system operators have defined the different qualities that control energy has to meet.

Primary control reserve (PCR) is the product that can be activated the soonest. Activation is automatic, decentralised and frequency-controlled. The primary control energy provided is not measured and settled. In case of an power plant outage all supplliers of PCR within the european synchronious area activate PCR without an intervention of the TSO. The balancing area with the outage receives the missing energy from the other PCR delivering balancing areas. This results in a system balance deviation.
In case of system balance deviations, the secondary control reserve (SCR) is used. This is a central and automated process (load-frequency controller) controlled by the German transmission system operators. The use of secondary control energy should not only result from the complete failure of installations. Continuously occurring deviations between forecast and actual current are also covered with secondary control energy. If the demand for secondary control reserve is too great or if it does not decrease, tertiary control reserve (TCR) is activated. SCR is then available again. The interaction between the different control reserves and the procurement process are described on regelleistung.net.


Netzregelverbund (NRV)

Grid Control Cooperation (GCC)
Germany has four transmission system operators, which are responsible for the balance between feed-in and offtake of electricity. In the past, this led to situations in which a power surplus in a grid area and a power deficit in another area were balanced independently of one another. Since 1 May 2010, the four transmission system operators work together in the context of the Grid Control Cooperation (GCC). Imbalances are first levelled out in the grid areas themselves and only the total deviations are balanced. This saves control energy and reduces the control reserves that need to be kept, as well as CO2 emissions.

International Grid Control Cooperation (IGCC)
In the past few years, the Grid Control Cooperation was continuously expanded beyond the borders of Germany. Now Denmark, the Netherlands, Switzerland, the Czech Republic, Belgium and Austria are also members of the IGCC. To exchange energy across borders, small transmission capacities are kept in reserve at the borders, but only the free capacities that are still available after intraday trading are used. As a result, less control energy is used. The provision of control reserves, however, is not reduced. Nevertheless, this additional netting saves tens of millions of euros and cuts back CO2 emissions each year.