Connection to the main grid
We implement the main grid connections that our customers need. We ensure that the main grid and the customer networks are compatible. We guarantee the electricity transmission capability at the connection points.
Connection to the main grid progresses in phases. The connections are planned at the early phase in cooperation with the customer. Based on information related to the customer’s connection, we examine the connection possibilities and agree on the connection solution. During the connection planning phase, the customer makes more detailed connection plans according to Fingrid's general connection terms (YLE) and checks them with Fingrid, after which construction can begin. The customer agrees on commissioning of its connection in good time with Fingrid’s operational organisation.
With up-to-date technical information exchange we ensure the best possible and technically safe end result.
Connectivity refers to the technical suitability of the connection to the main grid. In order to determine connectivity, the technical data and conditions of the connection are examined with the customer as early as possible in the project. Careful preparations ensure the technical feasibility of the connection before actual planning begins and prior to the acquisition of any land. A new connection may not unreasonably weaken the usability of the main grid and the connections of other customers. Depending on the connection site and projects being connected, there may be some limitations for connectivity. The volume of the power to be connected also depends on the location of other projects in the same region. Connectivity and main grid capacity are confirmed in the agreement phase.
The connection solution and location are selected by examining different connection possibilities with consideration to main grid system security, transmission capacity, electrical safety and environmental aspects as well as overall costs. If a new connection causes changes in the main grid, this must be taken into account when scheduling the customer’s project. The parties are responsible for the costs of planning related for their respective grids and, later on, for the costs related to construction, use and maintenance of the connection. The connection solution is agreed on a case-by-case basis.
A switchyard connection means a connection to a 400, 220 or 110 kV main grid switchyard. If planned connections are located close to a switchyard, they must be connected directly to the switchyard and not to a transmission line.
Connection solution Connected power
400 kV switchyard 250 MW or more
110 kV or 220 kV switchyard Less than 250 MW
110 kV transmission line connection
In Finland, the geographic transmission distances means that main grid transmission lines are long and switchyards are far apart. As a result, connections to 110 kV transmission line are also permitted after consideration of the available transmission capacity of the transmission line and other technical conditions. A transmission line connection means connecting a branch line or substation to a 110 kV main grid transmission line.
The maximum permitted rated current of a transformer without mechanical ventilation (ONAN) is 25 MVA. By equipping the transformer in question with mechanical ventilation (ONAF), the loading of the transformer up to 30 MW is permitted. A maximum of two transformers can be switched to a single connection point provided that the lower-voltage networks between the two transformers are not joined in parallel.
In general, power plant shall be connected to Fingrid's switchyard circuit breaker bay. if the transmisison capacity permits, small synchronous generators of less than 5 MW or converter connected power plants of up to 30 MW may be connected to the Fingrid's 110 kV transmission line, as long as their short-circuit current fed to the main grid is no more than 1.2 times the rated current of the power plant.
Connection solution Maximum power Maximum power
of a transformer of a generator
110 kV transmission line
connection 25 MVA 5 MW (30 MW*)
* Only if the short-circuit current fed by the power plant is no more than 1.2 times the rated current of the power plant.
The transmission capacity of the transmission line and the regional system security of the main grid must always be verified with the transmission system operator. The necessary grid analyses are always performed with the customer.
Important information on the main grid connection required from the customer is the customer’s contact information, basic information on the connection and a potential location, information on the transformer and branch line, detailed location information, and main grid information (sent by Fingrid to the customer), Power of electricity consumption and/or production of a connection, turbine type and power, connection point location on the map, and the estimated implementation schedule for the project.
If you’re planning a connection to the main grid, please contact our customer service. Please fill in the information in Fingrid's map service (in Finnish).
During the connection planning phase, the customer compiles detailed plans for its connection and delivers them along with the other necessary technical data to Fingrid for review. Planning should be started well in advance in projects where connection requires a transmission line which is constructed by the customer. The information required from the customer in the planning phase are a substation layout and elevation drawing, single line diagram, realisation of energy metering, earthing system, coordinates, information on the transformer and the branch line, information on the relay protection and communication link. To support the customer in planning, Fingrid provides information about the short-circuit current and earth fault current as well as the basic requirements for the protection system. The customer is responsible for the installation work for its substation equipment and the specification of their technical values.
Fingrid is responsible for arranging the energy metering and for providing an energy meter to the substation in question. The customer will reserve space for energy meters and submit to Fingrid’s contact person an energy measuring circuit diagram for the planning of measurements.
The details of main grid connections are agreed in a separate connection agreement that specifies the ownership and obligation boundaries and the connection fees. The prerequisite for signing a connection agreement is that the land-use plan (or decision on the need for planning) required for the project is legally valid, the connection solution meets the technical requirements and any expropriation permit application required for the transmission line has been sent to the authority. Fingrid’s General Connection Terms and Specifications for the Operational Performance of Power Generating Facilities are part of the connection agreement signed with the customer.
The connection agreement takes effect once it has been signed by the contracting parties and the customer has paid the connection fees outlined in the connection agreement. The customer pays the connection fee specified in the agreement upon receiving an invoice from Fingrid.
The connection agreement is valid subject to the condition that the customer’s high-voltage line is constructed within 36 months of the signing of the connection agreement and the connection fee has been paid by the due date on the invoice. The connection agreement is valid until further notice subject to a three-year period of notice. The agreement may be terminated 15 years after its signature at the earliest. The customer must have a valid connection agreement in order to sign a main grid contract.
If the customer’s connection requires construction of a new substation in the main grid, the customer pays the connection fee in the manner outlined in the project agreement.
A project agreement only when necessary
A project agreement is made prior to the connection agreement if Fingrid builds a new substation in the main grid for the needs of a single customer. An agreement can be made when the environmental impact assessments required by the authorities have been completed and the land-use process has been started or a decision concerning the planning solution has been made. The connecting party is responsible for construction costs of the substation in full.
Upon request, Fingrid provides a statement on a possible main grid connection. A statement may be provided when the environmental impact assessments required by the authorities have been completed and the land-use process has been started or a decision concerning the planning solution has been made.
Once the plans have been approved, construction can begin. The customer delivers the project implementation schedule, final documents and electrical values to Fingrid. Agreement concerning electricity transmission outages in the main grid during construction of the connection must be reached as early as possible. The connection need must be reported as early as possible and no later than 21 days before the proposed connection date. The main grid operation specialists who are responsible for the planning of outages and connections will inform the customer of the connection date.
Additionally, it is required that when operating in or in the immediate vicinity of Fingrid's transmission line’s right-of-way, a safety notification must always be filled in the Fingrid Safety Notification service.
Before commissioning, the customer must perform a commissioning inspection on the electrical installation of the connection. Fingrid’s operation specialist will examine the new connection and verify that the connection corresponds to the plans agreed with Fingrid earlier and that the connection can be energised. A protocol of the commissioning inspection is drawn up and sent to the operation specialist.
A period of time is reserved for construction in accordance with the terms of the connection agreement. Agreement concerning electricity transmission outages in the main grid during construction of the connection must be reached as early as possible.
The switching need must be reported as early as possible and no later than 21 days before the proposed switching date. The main grid operation specialists who are responsible for the planning of outages and connections will inform the customer of the switching date. It is the customer's responsibility to make sure that all technical information corresponding to the installations is delivered to the transmission system operator within two months of commissioning.
tel. +358 30 395 5282
tel. +358 30 395 4251
tel. +358 30 395 4199
Expert, Power Plants
tel. +358 30 395 5362
- Connection Agreement
- Connection Agreement Appendix 1
- How to connect to the main grid
- Connecting a 3-winding transformer to a Fingrid 110kV line
- Implementation of Under-frequency Load Shedding in Finland
- Exemplary Design - Under-frequency Load Shedding
- Electricity Quality Report
- Relay protection of the main grid and customer connections