Frequency containment reserve FCR

What it is (precise)

SOGL Article 3(2)(6) defines FCR by its job — containing frequency after an imbalance — and Article 3(2)(114) names the surrounding process, the frequency containment process (FCP). Restoring frequency is a different class: frequency restoration reserves (FRR) under Article 3(2)(7), backed by replacement reserves (RR) under Article 3(2)(8).

The clock matters as much as the definition. Article 3(2)(112) measures the FCR full activation time from the occurrence of the reference incident to the corresponding full activation of the FCR. The aFRR and mFRR full activation times are measured from a setpoint change instead, so the three headline numbers in this family sit on different stopwatches and cannot be compared directly.

Article 154(1) is the binding hook: each reserve connecting TSO shall ensure that the FCR fulfils the properties listed for its synchronous area in the Table of Annex V. That table is per synchronous area, and the rows differ. FCR full activation time is 30 s in Continental Europe, 10 s in Great Britain, 15 s in Ireland and Northern Ireland, and 30 s in the Nordic area only when system frequency is outside the standard frequency range.

FCR full activation frequency deviation is ±200 mHz in Continental Europe, ±500 mHz in Great Britain and in the Nordic area, and ±500 mHz dynamic or ±1 000 mHz static in Ireland and Northern Ireland. Quote the row, never the table.

Why it matters in a real grid-scale project

The synchronous area you connect in moves the qualification target by a factor of three. A design that fully activates in 30 seconds meets the Continental Europe row and fails Great Britain's 10 s. It also changes the trigger: ±200 mHz in Continental Europe against ±500 mHz in Great Britain and the Nordic area, which sets the droop slope the power plant controller has to implement.

None of this is discretionary — Article 154(1) puts the obligation on the reserve connecting TSO, and the TSO passes it through to you at prequalification. Put the synchronous area on the first page of the functional specification, before anyone sizes anything.

FCR is sold per MW but sized in MWh. The reserve must stay activated as long as the frequency deviation persists, so the binding design question is endurance, not speed — a modern power conversion system is far faster than any of these windows.

The Nordic requirements make this explicit: any providing entity whose reservoir is smaller than two hours of continuous full activation is classed as limited energy reservoir (LER), which covers essentially every grid battery, and LER entities must show minimum endurance of 20 minutes for FCR-D and 60 minutes for FCR-N. That is roughly 0.33 MWh per MW for FCR-D and 1 MWh per MW for FCR-N, the latter in both directions, so it constrains charging headroom as well as discharge energy.

Typical values and standards

The SOGL Annex V rows are the ones to memorise, always with the synchronous area attached: Continental Europe 30 s and ±200 mHz; Great Britain 10 s and ±500 mHz; Ireland and Northern Ireland 15 s, with ±500 mHz dynamic and ±1 000 mHz static FCR; Nordic ±500 mHz, with the 30 s figure applying only outside the standard frequency range.

The standard frequency ranges themselves come from Annex III Table 1 — ±50 mHz in Continental Europe, ±200 mHz in Great Britain and in Ireland and Northern Ireland, ±100 mHz in the Nordic area. So the Nordic 30 s condition bites outside 49.9–50.1 Hz, which is where the FCR-D products live.

The Nordic products are defined in the joint technical requirements for the Nordic synchronous area (Version 1.1, 28 March 2025, published under the ENTSO-E imprint and developed by Energinet, Fingrid, Statnett and Svenska kraftnät).

Three products can be provided independently: FCR-N across 49.9–50.1 Hz, FCR-D upwards across 49.9–49.5 Hz, and FCR-D downwards across 50.1–50.5 Hz, each activated close to proportionally to the frequency control error in steady state. Table 1 fixes the end points: FCR-D upward reaches 100 % activation at f ≤ 49.5 Hz and zero at f ≥ 49.9 Hz; FCR-N runs from 100 % negative at f ≥ 50.1 Hz through zero at 50 Hz to 100 % positive at f ≤ 49.9 Hz.

Speed for Nordic FCR-D is written as a power criterion and an energy criterion at the same instant, 7.5 seconds after the frequency ramp starts: |ΔP7.5s| ≥ 0.86 · ΔPss and |E7.5s| ≥ 3.2 s · ΔPss, where ΔPss is the steady-state response. These requirements entered into force on 1 September 2023 and replaced older wording of the 50 % in 5 s, 100 % in 30 s type. The energy criterion is the one that catches converters with a slow start — a unit can reach 86 % of steady state at 7.5 s and still fail on delivered energy if the front of the ramp is lazy.

How it shows up in specs, studies and contracts

Contractually, FCR reaches you through the connecting TSO's terms rather than through the regulation. Fingrid, for example, publishes terms and conditions for FCR providers whose Appendix 2 states the purpose split plainly: FCR-D aims to contain frequency to at least 49.5 Hz once it leaves the 49.9–50.1 Hz normal range, while FCR-N aims to keep frequency inside that range.

Read the TSO document and the Nordic technical requirements together — the first tells you what you are paid to do, the second tells you the test the plant has to pass, including the LER classification that drives energy sizing.

In the market layer, the Electricity Balancing Guideline (Regulation (EU) 2017/2195) splits what you sell into balancing capacity — a volume of reserve you have agreed to hold and bid — and balancing energy, the energy actually used.

Article 1(1) repays close reading: the guideline establishes common principles for the procurement and settlement of FCR, FRR and RR, but the common activation methodology it creates covers FRR and RR only. FCR has no counterpart to the PICASSO and MARI activation platforms created under that methodology: activation stays a synchronous-area matter under SOGL, and how FCR capacity is procured is set by the connecting TSO's arrangements.

Common pitfalls

The expensive one is quoting 30 seconds as the European FCR activation time. It is the Continental Europe row of SOGL Annex V. Great Britain is 10 s, Ireland and Northern Ireland 15 s, and the Nordic 30 s applies only when frequency is outside the standard frequency range. A specification that says FCR full activation in 30 s per SOGL, without naming a synchronous area, is under-specified — and it will be read as compliant by a procurement team with no way to know better. Name the area every time the number is written down.

Second, legacy Nordic figures. The commonly cited claim that FCR-N is fully activated within 3 minutes does not appear in the current Nordic technical requirements (Version 1.1, 28 March 2025); treat it as a pre-2023 requirement unless you can re-source it. Third, endurance: the 15-minute hold in the Nordic document is the non-LER test, and sizing a battery to it is wrong. Batteries land in the LER regime, where the governing figures are 20 minutes for FCR-D and 60 minutes for FCR-N — for FCR-N that is four times the energy a 15-minute reading would give you.