Ramping means change in power flow (or power generation) from one time unit to the next.
In the day-ahead and intraday markets, all trading across many of the HVDC cables is subject to a ramping restriction of 600 MW. The restrictions imply that trade plans on all HVDC connections cannot be changed with more than 600 MW from one hour to the next. This restriction is put on each of the cables individually.
Handling of ramping restrictions in the day-ahead price calculation
The HVDC connections listed below are all subject to specific ramping restrictions. The restrictions have been imposed by the national transmission system operators Svenska Kraftnät, Energinet.dk and Statnett.
When carrying out the ramping in the day-ahead market, the PCR calculation system Euphemia aims at minimizing the influence of the ramping on the buyers' and sellers' economic gain, and the ramping is furthermore handled as an optimization over the 24 hours involved in the price calculation.
Ramping restrictions are also handled on day-shifts by including information about the flow in the last hour from the previous day in the calculation. The ramping restriction between the Nordic synchronous system and the Continent (UCTE) is imposed separately on the DC links listed below.
In addition there is also a joint restriction for the KontiSkan and Skagerrak. The ramping restriction sets a limit on the total incoming/outgoing power flow from Jutland on the two connections combined, which is due to the internal grid limitations on Jutland, called Cut B.
|Name of connection||Connection points|
|Estlink||FI <-> EE|
The reasons for ramping restrictions
When imposing the ramping restrictions the Nordic transmission system operators have stated that frequent large changes in production and flow in fully loaded corridors in the grid make it more difficult to control the frequency. The transmission system operators are therefore imposing the ramping restrictions on HVDC connections in order to reduce risks that might threaten the security of supply.
Without restricting the maximum change of flow per hour (ramping) on interconnectors, very large ancillary services and operational reserves would be needed to handle imbalances within the operative hours.