Handling of ramping restrictions in day-ahead price calculation

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 and Statnett.

Ramping restriction between the Nordic system and the Continent is imposed separately on the links below.

In addition, there is also a joint restriction of 450 MW per market time unit (MTU) for NordLink and NorNed. The ramping restriction sets a limit on the total change of flow on the two connections combined.

Reasons for ramping restrictions

When imposing ramping restrictions, the Nordic transmission system operators have stated that frequent large changes in production and flow in the grid make it more difficult to control the frequency. The transmission system operators are therefore imposing ramping restrictions on HVDC connections in order to reduce risks that might threaten security of supply.

Without restricting the maximum change of flow per MTU (ramping) on interconnectors, very large ancillary services and operational reserves would be needed to handle imbalances within operative MTUs.

Ramping and Loss factors

N2EX/NSL

SDAC

* The ramping value indicated is defined for every 4th MTU, i.e. on MTU 1, 5, 9…, 93 (MTU 97 for DST wintertime). For other MTUs, the ramping is set to 0. Defining non-zero ramping every-fourth-MTU is used by TSOs to only allow a change of flow (ramp) at the hour-shift and not within the hour, thus keeping the flow fixed on the MTUs within the hour. This method is called Quarterly Polarity Reversals Elimination (QPRE). It is a measure to control the number of flows fluctuations (polarity reversals) on the interconnectors, which otherwise could become technically unfeasible and endanger the operation of the interconnector in the long term.

	Timestep	Flow [MW]	Delta [MW]	Ramping [MW]
Example: NorNed	H1-Q4	331		309
	H2-Q1	34.4	-296.6	309
	H2-Q2	343.4	309	309
	H2-Q3	34.4	-309	309

 

	Timestep	Flow [MW]	Delta [MW]	Ramping [MW]
Example: SwePol	H1-Q4	300		0
	H2-Q1	600	300	300
	H2-Q2	600	0	0
	H2-Q3	600		0
	H2-Q4	600	0