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.