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Connecting a type D battery storage system to the transmission grid

For type D battery storage (at least 30 MW or a connection point of 110 kV or above), Fingrid is involved from the start, and the requirements affect equipment choices before purchase agreements are signed. We handle the technical whole, from stage 0 studies to the final operational notification, so the battery starts earning as quickly as possible.

Discuss your projectType B battery storage

Division of work in our projects

Elpartner

Components and automation equipment

Components and automation equipment for power distribution and transmission are designed and ordered through Elpartner:

  • Transformers and transformer substations: MV step-up transformers and main transformers
  • Switchgear
  • Automation equipment
Greencontrol

Control and SJV requirements

Power plant controllers and everything related to control and SJV requirements through our sister company Greencontrol.

Check before signing purchase agreements

In a type D project, grid code requirements are largely settled by the equipment choices. If one of these is missed at the ordering stage, fixing it later is slow and expensive.

  • Grid forming (GFM): SJV2024 requires it from type C and D energy storage. Make sure the inverter supplier has delivered it before.
  • The new HVRT requirement, and protection that does not trip during LVRT/HVRT events or voltage and frequency dips.
  • Reactive power capacity at the connection point and active power priority in the normal voltage range.
  • Interaction between the power plant controller and the inverters: communication and protocol delays affect the control response.
  • Remote controllability and prioritisation of controls between the network operator, equipment supplier and aggregator.
  • Where needed, point-on-wave controlled switching, on-load tap changers for the main transformers, and disturbance and swing recorders.
  • Telecommunications and cybersecurity, including NCER requirements and the reliability of reserve provision.
  • Fingrid
  • Connectee
  • Network operator and connectee
  • Elpartner or Greencontrol involved
Part 1

Connection and baseline data

Fingrid is involved from the start.

  1. Connection enquiry, zoning and permits

    Connectee

    The connection enquiry is made in Oma Fingrid, and zoning and permits for the project are started.

  2. Connection agreement enquiry

    Network operator and connectee

    Fingrid’s connection agreement enquiry practice for energy storage, if it applies to the area.

    Note: Some areas have temporary connection restrictions for energy storage.

  3. Design baseline data from Fingrid

    Fingrid

    Project-specific grid data: fault currents, SCR, VCSCR and ESCR values and hazardous voltages (vikavirrat@fingrid.fi), and specific study requirements (SJV2024 chapter 5, gridcompliance@fingrid.fi).

    Greencontrol: Project data needed for the requests (items 1.1–1.12 of the stage 0 questionnaire).

Part 2

Stage 0 before equipment selection

The requirements affect equipment choices before purchase agreements are signed.

  1. Stage 0 questionnaire and supplier answers

    Connectee

    The type D questionnaire in Fingrid’s VJV/SJV2024 start tool is reviewed with the project’s experts: control philosophy and power plant controller, main transformers, protection (LVRT/HVRT), disturbance recorders, grid forming, remote controllability, and telecommunications and cybersecurity.

    Elpartner: Equipment-related items: main transformers and switchgear, and the answers from equipment suppliers.

    Greencontrol: Control philosophy, power plant controller (GC-PPC-D), protection, RTU, communications and the other items related to control and SJV requirements.

  2. Stage 0 kick-off meeting

    Fingrid

    Meeting with Fingrid and the network operator at the connection point. The questionnaire is updated and kept as the meeting log, and the next steps are agreed.

    Elpartner: Taking part as the equipment expert.

    Greencontrol: Taking part as the control and SJV requirements expert.

  3. Energy storage stage 0 studies

    Connectee

    Required studies, for example anti-islanding (EVY) studies. SJV2024 requires grid forming capability from type C and D energy storage.

    Greencontrol: PSS/E and PSCAD models of the controller with project-specific parameters.

Part 3

Agreement, procurement and stage 1

Equipment is ordered and stage 1 material is delivered on time.

  1. Connection agreement

    Network operator and connectee

    Connection agreement with the network operator at the connection point.

  2. Equipment orders

    Connectee

    Equipment is ordered according to the principles agreed in stage 0.

    Note: Ask equipment suppliers for simulation models already at the tender stage, and check the model versions Fingrid requires (PSS/E v36, PSCAD).

    Elpartner: Main transformers, MV step-up transformers, transformer substations, switchgear and automation equipment and, where needed, point-on-wave controlled switching with Vizimax SynchroTeq relays.

    Greencontrol: Power plant controller (GC-PPC-D).

  3. Stage 1 kick-off meeting

    Fingrid

    Stage 1 is started with Fingrid.

  4. Project in Oma Fingrid

    Network operator and connectee

    The network operator at the connection point opens the Oma Fingrid project to which the design data is submitted.

  5. Stage 1 documentation and models

    Connectee

    The design data in SJV tables 7.1 and 7.2 and validated PSS/E and PSCAD models are submitted to Oma Fingrid.

    Note: The material must be submitted 6 months before the interim operational notification (ION).

    Elpartner: Equipment documentation.

    Greencontrol: Controller models and SJV documentation.

Part 4

Connection and start of production

The plant is connected and production starts.

  1. Switching and energisation (EON)

    Fingrid

    Switching is agreed with Fingrid, and the plant is energised (EON).

    Note: Switching must be agreed at least 21 days before EON.

  2. Stage 1 complete (ION) – production starts

    Fingrid

    The interim operational notification (ION) is issued and production can start.

    Note: While the ION is valid, mFRR reserves can be provided without the final operational notification.

Part 5

Tests, reserves and final approval

The plant is verified and reserve operation starts.

  1. VJV/SJV test programme and review

    Connectee

    The test programme is prepared and reviewed before testing.

    Note: The test programme must be submitted about 2 months before the tests.

    Greencontrol: Preparing the test programme.

  2. VJV/SJV tests

    Connectee

    The commissioning tests in chapter 15 of SJV2024 are performed and checked.

    Note: The tests must be done within 9 months of the ION.

    Greencontrol: Testing and reporting.

  3. Reserve tests

    Connectee

    mFRR tests can be done while the ION is valid. FFR, FCR and aFRR tests also require the network operator to have checked the commissioning test results (except tests replaced by continuous monitoring).

    Note: If changes are needed after a later review, the regulation tests may have to be repeated.

    Greencontrol: Reserve tests and integration with the aggregator’s system.

  4. Test approval – reserve operation can start

    Fingrid

    Fingrid approves the VJV/SJV tests and reserve operation can start.

  5. Stage 2 documentation and models

    Connectee

    Models and documentation updated after the tests are submitted.

    Note: Stage 2 material must be submitted within 12 months of the ION.

    Greencontrol: Updated controller models and SJV documentation.

  6. Final operational notification (FON)

    Fingrid

    The project is verified and the final operational notification is issued.

    Note: The FON must be obtained within 18 months of the ION.

Remember changes too: if an existing plant is modified, for example its controller is replaced or reparameterised, Fingrid must be asked to assess the impact of the change.

Based on Fingrid’s type D VJV/SJV2024 process, Fingrid’s VJV/SJV2024 start tool and its guidance on prerequisites for reserve market participation (5 October 2026). This description is meant to give an overview. The exact and current requirements are always in the official requirements of Fingrid and the network operator at the connection point (YLE, VJV, SJV, KJV). Updated 10/2026.

Fingrid materials: VJV/SJV2024 start tool (xlsx) and Prerequisites for reserve market participation (pdf, in Finnish).

Planning a battery storage project?

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