Why is both capacity and linearity testing needed for incrementally regulated resources to deliver FCR?

Linearity tests and capacity tests are two of the requirements that must be met in order to be able to deliver ancillary services. These requirements come from ENTSO-E (European Network of Transmission System Operators for Electricity).

In purely technical terms, capacity tests are carried out to ensure how quickly the reserve is activated and how large a volume can be activated.

Linearity tests are performed to ensure that the partly linear response from the incrementally regulated system is within the set limits.