In this utility system the morning load increases smoothly over the course of 2 hours by 400 MW (or 12%), but includes rapid short-term ramps of ±50 MW. Some OECD countries may have a different mechanism or use a different terminology, but the principle is common to all TSOs. Frequency containment reserves are operating reserves necessary for constant containment of frequency deviations (fluctuations) from nominal value in order to constantly maintain the power balance in the whole synchronously interconnected system.6 Activation of these reserves results in a restored power balance at a frequency deviating from nominal value. Operating reserves of this category are usually activated automatically and locally.