1 System Operation

The System Operation Guideline

The Commission Regulation (EU) 2017/1485 of 2 August 2017 establishing a guideline on electricity transmission system operation (SOGL) sets out harmonised rules on how to ensure system security through efficient grid operation in a variable renewables paradigm.
The implementation of the SOGL and the related methodologies entails several challenging tasks for TSOs at the pan-European, synchronous area and regional levels. Work at the pan-European level is facilitated by ENTSO-E, whereas synchronous areas’ activities are decided by TSOs in the respective regional groups. The following SOGL implementation activities were carried out in 2021:
SOGL deliverables in 2021Key documents and dates
Art. 75.1:Methodology for coordinating operational security analysis14 Jun 2021:ACER approval2 of the amendment
Art. 76.1:Italy North TSOs’ common provisions for regional operational security coordination10 Jun – 11 Jul 2021:Public consultation
20 Dec 2021:NRA approval of the amended proposal
Art. 141.2:All TSOs’ proposal for amending the determination of LFC blocks for the Synchronous Area Continental Europe with regard to LFC Area Denmark West22 Feb – 21 Mar 2021:Public consultation
Each TSO submitted proposal separately to respective NRA
Art. 156.10:Nordic TSOs' proposal on minimum activation period to be ensured by FCR providers14 Dec 2020 – 25 Jan 2021:Public consultation
Dec 2021:Submission to relevant NRAs
Art. 156.11:All Continental Europe TSOs’ proposal for the definition of a minimum activation time period required for limited energy reservoirs to remain available during alert state7 Oct 2021:Submission to relevant NRAs
3 Aug – 12 Sep 2021:Public consultation
Art. 137.3-4:Nordic TSOs’ proposal for ramping restrictions for active power output21 Jan – 22 Feb 2021:Public consultation
Feb 2021:NRAs approval

Table 1 – SO GL implementation activities in 2021

2 ACER approved the Proposal subject to the amendments set out in Annex I to Decision 07/2021

In addition, on 15 December 2021 ENTSO-E published the first biennial progress report on the development of the Probabilistic Risk Assessment methodology pursuant to the methodology for coordinating operational security analysis (hereafter CSAM), specifically Article 44 (1) and 44 (2).

Last but not least, ENTSO-E launched an Active Library which provides public information regarding specific SOGL Articles that are to be implemented at national level such as the field of data exchange (SO GL Article 40.6) and load frequency control (related agreements and information on frequency quality).

ENTSO-E provided regular updates to stakeholders on these topics and other system operation issues via the System Operation European Stakeholders Committee.

Implementation monitoring

Between July and September 2021, ENTSO-E released three important annual implementation monitoring reports: the Annual Report on Incident Classification Scale (ICS) 2020 (Art. 15 SOGL), the Annual Report on Load-Frequency Control 2020 (Art. 16 SOGL) and the all TSOs’ scenario definition and scenario description for the year 2022 (Art. 65 SOGL). Moreover, the publication of the 2021 Biennial Progress Report on Operational Probabilistic Coordinated Security Assessment and Risk Management of December 2021 provided a view on TSOs’ progress on the development of the Probabilistic Risk Assessment Methodology (PRA)3 to be completed by 2027.

3 The PRA allows TSOs to assess the probability, and subsequently the impact, of the failure of the power system, in order to establish the operational security limits.

Key dates & documents

15 July 2021: Publication of the All TSOs’ scenario definition and scenario description for the year 2022

30 Sep 2021: Publication of the Incident Classification Scale 2020 annual report

30 Sep 2021: Publication of the Load-Frequency Control Annual Report 2020

12 Dec 2020: Publication of the 2021 Biennial PRA Report

The Emergency and Restoration Code

The Emergency and Restoration Network Code (NC ER) sets out harmonised rules on how to deal with emergency situations and restore the system as efficiently and as quickly as possible. It entered into force on 18 December 2017 and is primarily subject to implementation at a national or TSO level. Implementation should be completed by December 2022 (Art. 55 NC ER). In 2021, ENTSO-E has monitored the national implementation of the network code (Art. 52.1 NC ER). The implementation of the NC ER was also discussed with stakeholders during meetings of the System Operation European Stakeholder Committee that took place in 2021.

Every semester, ENTSO-E provided an overview of the national implementation of the Emergency & Restoration Network Code to ACER and NRAs via the System Operation Coordination Group.

Key dates & documents

15 July 2021: Publication of the “Final report on the separation of the Continental Europe power system on 8 January 2021”

12 Nov 2021: Publication of the “Factual Report on the Separation of the Continental Europe Synchronous Area on 24 July 2021”

6 Dec 2021: Publication of the “Frequency stability in long-term scenarios and relevant requirements” study

Frequency stability

Following the separation of the Continental Europe Synchronous Area of 8 January 2021, the Expert Panel4 issued its final report in July 2021. The report includes a comprehensive analytical overview of the incident and proposes 22 recommendations to prevent and mitigate the consequences of similar future events In November 2021, the ENTSO-E Task Force published the Factual Report on the Continental Europe Synchronous Area Separation that took place on 24 July 2021. It contains the timeline of events and includes the assessment of the incident based on the ICS Methodology.

The Factual Report will serve as the basis for further investigation by an Expert Panel which, according to the ICS Methodology, shall prepare a Final Report to be published in 2022. In December 2021, ENTSO-E published a study assessing the impact of the reduction of inertia on the frequency stability of the Continental Europe synchronous area. Based on the TYNDP2018 long-term scenarios and market studies, the report investigates – under a set of assumptions – a very large set of possible combinations of system split cases between market nodes in the synchronous area of Continental Europe.

4 The Expert Panel was composed of representatives of the affected TSOs, ENTSO-E, regional security coordinators (RSCs), national regulators and ACER, and was established on 4 March 2021 to carry out the investigation in accordance with the SOGL and the ICS Methodology.

Common Grid Models

The CGM is a pan-European cooperation programme that enables European electricity TSOs to seamlessly share operational planning data through a secure digital and communications network infrastructure. The legal basis for CGM is found in three of the Network Codes: the SOGL (Art. 64), the CACM Regulation (Art. 17) and the FCA Regulation (Art. 18). CGM is a prerequisite for several services harmonised in the Network Codes, including coordinated capacity calculation, operational security analysis, outage planning coordination and adequacy analysis.

A CGM compiles the Individual Grid Model (IGM) of each TSO, covering timeframes from one year before real time to one hour before real time. TSOs’ IGMs, after following a quality assessment and pan-European alignment process, are picked up by RSCs, who merge them into a pan-European CGM and feed the merged CGM back into the system.

Achievements and Challenges

The CGM Programme was mandated to establish the CGM Build Process among ENTSO-E, TSOs and RSCs. CGM went live on 8 December 2021, delivering a full data exchange system and IT infrastructure, comprising:

  • The Physical Communication Network (PCN), a pan-­European private communications network
  • The Operational Planning Data Environment (OPDE), a data exchange platform enabling IGMs and CGMs to be shared between TSOs and RSCs
  • Definition of a standardised structure for IGMs and CGMs
  • Validation rules required to ensure the completeness and quality of IGMs and CGMs
  • Systems required to combine IGMs into a CGM, via RSCs.
Key dates & documents

8 Dec 2021: CGM go-live

ENTSO-E Awareness System

The EAS provides a real-time pan-European view of the state of transmission systems. All TSOs input a number of measurements including frequency and cross-border exchange. These measurements are then merged to provide an overall European view of each TSO on the platform.

ENTSO-E has been monitoring the maintenance of the EAS to ensure its continuous operations within TSO business Service-Level Agreements (SLAs).

The following evolutions were introduced during 2021: improvements in Generation map, addition of EAS on-line data quality check, accession of TEIAS, introduction of a security plan for EAS, study report on the evolution of EAS integrating the recommendations of the technical report on 8 January 2021 system split, and the start of the Wide Area Monitoring System (WAMS) integration into the EAS project.

Regional Coordination

Cooperation at the regional level is a key building block for ensuring security of supply and implementing the internal energy market. The development of intermittent generation and increased interconnections render regional coordination among TSOs more important than ever.

ENTSO-E supports regional tasks by providing a platform for coordinating regional deliverables which affect neighbouring regions and where addressing the matter at the pan-European level is more efficient than doing so bilaterally.

Key dates & documents

26 July 2021: Publication of the Annual Report on Regional Coordination Assessment

RSCs are entities owned and appointed by TSOs to fulfil six tasks: security analysis, capacity calculation, outage coordination, adequacy forecast, emergency and restoration planning, and the CGM creation. The SOGL formalised the role of the RSCs and made it legally binding for TSOs to procure at least the five core tasks from one of the RSCs. Through their recommendations to TSOs, RSCs contribute to increasing efficiency in system operation; minimising the risks of wide-area events such as brownouts or blackouts; and lowering costs through ensuring the maximised availability of transmission capacity to market participants.

SEleNe CC announced the official start of services provision to its stakeholders in June 2021. Moreover, to fulfil the monitoring obligations stemming from Art. 17 SOGL, in July 2021 ENTSO-E published its Annual Report on Regional Coordination Assessment. It contains key-performance indicators for the services provided by the RSCs.

Figure 1 – RSC map

Regional Coordination in the Clean Energy Package

The CEP establishes an enhanced framework for regional cooperation through the establishment of Regional Coordination Centres (RCCs). Art. 35 of Regulation (EU) 2019/943 (the “Electricity Regulation”) requires that TSOs of System Operation Regions (SORs) develop a proposal for the establishment of the RCCs of their region. These should be operational by 1 July 2022 and will replace existing RSCs, adding new tasks for the RCCs5.

ACER and ENTSO-E have continued their exchange on the definition of the SORs in 2021. The latest ACER Decision No 13/2021 was published in October 2021. In 2022 the exchange will continue in order to determine a final definition of the SORs taking into account all technical and legal aspects in the best suitable way.

During 2021, ENTSO-E supported the transition from RSCs to RCCs and worked on the proposals for new RCC tasks according to Art. 37 of the Electricity Regulation and consulted with stakeholders.

5 Article 37 of the Electricity Regulation mentions 10 new tasks in addition to the ones provided for by SOGL and the NC ER as adopted on the basis of Regulation 714/2009.

Key dates & documents

19 Oct 2021: ACER Decision regarding the definition of the SORs

13 Jul – 10 Sep 2021: Public consultation on the Proposal for Regional Coordination Centre Post-Operation and Post-Disturbances Analysis and Reporting Methodology

6 Oct – 19 Nov 2021: Public consultation on the proposal for Regional Coordination Centre Training and Certification methodology

Other regional developments

ENTSO-E is ensuring the IT operations and evolutions of Outage Planning Coordination (OPC) and Short-Term Adequacy Assessment Process (STA) pan-European IT Tools. The OPC pan-European IT Tool, live since end of March 2020, allows five RSCs and 38 TSOs to coordinate outage planning on a weekly basis. Based on generation and demand forecasts provided by all ENTSO-E Member TSOs, the STA pan-European IT tool, launched in May 2020, enables RSCs and TSOs to perform daily calculations which identify adequacy levels for the week ahead.

In 2021, ENTSO-E coordinated with RSCs and TSOs over the implementation of major evolutions on OPC and STA Pan European tools covering the following new legally mandated features: introduction of High Voltage Direct Current Connections (HVDC) and generation tripping in STA forecasts, relevant asset outage coordination, generation outages integration from ENTSO-E Transparency Platform.

Tasks for Synchronous Areas

Depending on the specific arrangements within each Regional Group corresponding to Synchronous Areas (SAs), ENTSO-E supports on an ad-hoc basis or serves the Region on a continuous basis. ENTSO-E supports the Regional Group Continental Europe with implementation processes, as well as the synchronisation project between the Baltic TSOs and the SA Continental Europe and also the synchronisation project between Ukraine/Moldova and the SA Continental Europe.

In addition, work continues on the coordination of short- and long-term measures to mitigate the frequency deviations in Continental Europe, notably the deterministic frequency deviations related to the change of scheduling programmes at the early morning and late evening hours.

The vast majority of the System Operation tasks aim to improve operations and secure electricity supply by enhancing forecast, planning and regional coordination to cope with higher and higher volumes of variable RES and with the gradual phase out of conventional power plant in the system. This is key to achieving a carbon-neutral European energy system by 2050.


ENTSO-E Annual Report 2021

This Annual Report covers the period January to December 2021. It focuses on the legal mandates given to ENTSO-E and on the Pan European All TSOs tasks, facilitated by ENTSO-E. The activities covered in this report were performed thanks to the 42 members of ENTSO-E who provide its financial resources and whose staff provides expertise to the Association.


  1. System Operation
  2. Market
  3. System Development
  4. Transparency Regulation
  5. Research, Development and Innovation
  6. Cybersecurity, Interoperability and Data
  7. TSO–DSO partnership and demand side flexibility
Download Full Report (PDF, 10 Mb)