Reserves and balancing power

Electricity production must be equal to electricity consumption at all times. The balance between production and consumption is indicated by the frequency of the electricity grid which has a nominal value of 50.0 Hz. The market operators plan and balance their consumption and production in advance, but in practice there are deviations during each hour. To balance these deviations, Fingrid procures different kinds of reserves from reserve markets. Reserves are power plants and consumption resources which either increase or decrease their electric power according to the need of the power system.

Reserve obligations and procurement sources

In the joint Nordic system (Finland, Sweden, Norway and East Denmark), the obligations for maintaining reserves have been agreed in System Operation Agreement between the Nordic Transmission System Operators (TSOs).

Total of 600 MW of Frequency Containment Reserve for Normal operation (FCR-N) is constantly maintained for the frequency regulation of the normal state. A jointly maintained reserve is divided annually between the Nordic TSOs in relation to the total consumption in each country.
 
Frequency Containment Reserve for Disturbances (FCR-D) is maintained to the extent that the power system can withstand, for example, disconnection of a large production unit without the steady state frequency deviation exceeding 0.5 Hz. Reserve maintained in the whole system is set weekly to correspond to the greatest individual fault in the system, reduced by self-regulation of load in the system (200 MW). In a normal situation, a total of 1,200 MW of Frequency Containment Reserve for Disturbances is maintained in the joint Nordic system.

It has been agreed that up to 300 MW of Automatic Frequency Restoration Reserve (aFRR) is maintained in predefined morning and evening hours in the Nordic countries in 2017. Country-specific obligations have been divided between the Nordic TSOs in relation to the annual consumption.

Furthermore, each TSO maintains Manual Frequency Restoration Reserve (mFRR) to cover the dimensioning fault in its own area.

The TSO of each country procures its share of reserves as it considers best. In order to meet reserve obligations, trade can be done between countries. Part of reserves must be maintained nationally, so that the frequency can also be maintained in situations of island operation. In normal situation, a maximum of 1/3 of the obligations for frequency containment reserves can be purchased from other Nordic countries.

Fingrid's reserve obligations and procurement sources in 2017: 

Reserve product

Obligation

Procurement channel

Maximum contracted capacity

Frequency Containment Reserve for Normal Operation (FCR-N)​

about 140 MW

Yearly market

Hourly market

Other Nordic countries

Vyborg DC link

Estonia, Estlink 1 & 2 ​

72,6 MW

124 MW

-

90 MW

35 MW​

Frequency Containment Reserve for Disturbances
(​FCR-D)

220–265 MW

​Yearly market

Hourly market

Other Nordic countries

435 MW

​595 MW

-

Automatic Frequency Restoration Reserve (aFRR)

70 MW (certain morning and evening hours only)

​Hourly market

Sweden

-

-

Manual Frequency Restoration Reserve (mFRR)

880–1100 MW

Balancing energy and balancing capacity markets

Fingrid's reserve power plants

Leasing reserve power plants

-

 

935 MW​

 

299 MW

Covering of costs

Fingrid covers the maintenance costs of reserves with a grid network tariff and payments collected in balance services. The costs of the balancing power market are covered by imbalance power.

Reserve products

Reserves are divided into three groups based on their purpose:

  1. Frequency Containment Reserves (FCR) are used for the constant control of frequency.
  2. The purpose of Frequency Restoration Reserves (FRR) is to return the frequency to its normal range (49.9 - 50.1 Hz) and to release activated Frequency Containment Reserves back into use. 
  3. Replacement Reserves (RR) release activated Frequency Restoration Reserves back to a state of readiness in case of new disturbances. (Not used in the Nordic power system)

 

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