What must be assured is that in the case of concrete demand for tertiary control reserve from the system operator, the corresponding volumes can be fed into or extracted from the grid of the balance area APG.
APCS provides suppliers with an Internet-based bidding platform for placing bids. The bids are binding for the respective bidders. Bids must be placed by the latest at 16:00 hrs for the following day, before Saturdays, Sundays and official holidays until and including the next workday (except for Saturday).
The bids are separated by APCS and ranked by buy and sell volumes in accordance with the prices quoted (Merit Order List). Bids for tertiary control reserve must be placed in blocks of four hours for the time intervals 0:00 to 4:00 hrs, 4:00 to 8:00 hrs, 8:00 to 12:00 hrs, 12:00 to 16:00 hrs, 16:00 to 20:00 hrs, and 20:00 to 24:00 hrs. Depending on the bidder and period of the bid, a bid may be placed for between 10 MW and 50 MW (variable in 1 MW intervals) as a block for each of the above listed time intervals. Additional bids by the same bidder for the same time interval must be placed for volumes of between 25 MW ad 50 MW (variable in 1 MW intervals). The bids per block must be placed at fixed prices.
The Merit Order List prepared by APCS is sent to the system operator who then calls the required feed-in or extraction of tertiary control reserve from the bidders in accordance with the Merit Order List.
The following diagram illustrates the flows of tertiary control reserve:
