The introduction of the shared call for tenders for FCR has given connecting TSOs a key role to play. A connecting TSO is a TSO in the control area of which the technical units to be marketed by the supplier are connected to the grid, irrespective of the voltage level. The connecting TSO conducts the prequalification procedure procedure for these technical units (e.g. generating units or controllable consumer loads) in its control area and is the sole contracting party of the supplier. If a supplier offers technical units in several control areas, a framework agreement has to be concluded with each respective connecting TSO. A precondition for concluding such a framework agreement is a successful prequalification, whereby the prequalified capacity must at least equal the minimum lot size. The framework agreement is a precondition for taking part in a joint tender for FCR.
The TSO's shared Internet platform www.regelleistung.net has been used to implement the joint call for tenders since 1st December 2007. On this platform, calls for tenders are published, bids are processed, and bidders are informed whether their bids have been accepted or rejected.
The call for tenders for FCR is 'symmetrical', meaning there is no separate call for tenders for positive FCR (additional power) and negative FCR (less power).