Grid connection solution
The electricity system security and usability are always affected by a grid connection solution. When planning a grid connection for our customer we evaluate system security, transmission capacity and electricity safety of the main grid to promote a good quality solution. Equally important we consider environmental issues as well as the impact on the total cost of the planned solution. The grid connection solution is planned and agreed with our customer on a case-by-case basis.
A new connection may not unreasonably weaken the main grid's usability and that of other customers’ connections. The protection of the connecting network is done by our customer in accordance with the connection solution principles.
The parties pay for the costs of the planning of their own network and for the costs of subsequent construction, operation and maintenance of the connection.
Connection to a substation (switchyard connection)
A switchyard connection means a connection to a 400 kV, 220 kV or 110 kV switchyard of the main grid network. If planned connections locate close to a switchyard, these will be directly connected to a switchyard instead of a power transmission line.
Table: Grid connection to a substation
|Connection solution||Connecting power|
|400 kV switchyard||More than (200-) 250 MVA|
|110 kV or 220 kV switchyard||Less than (200-) 250 MVA|
Based on our company project time window we estimate the planning and construction of a new switchyard to take 24 months.
Connection to a 110 kV power transmission line
Due to the geographical distances in Finland, the lines for the power transmission are long and the substation are far apart. Consequently, connection solutions to 110 kV power lines are also possible when transmission capacity of the main grid and other technical terms and conditions are first taken into account. A power line connection means a branch line or a substation connection with a fixed or a switching device solution connecting to a 110 kV power line of the main grid.
The maximum power of a transformer that can be connected to a 110 kV power transmission line is 25 MVA. 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. A maximum of 5 MVA of electricity production can be connected to a power line with the exception of a maximum of 25 MVA wind power generation which short-circuit current fed is limited to 1.2 times the rated current of the power plant.
Table: Grid connection to a 110 kV power transmission line
|Connection solution||Maximum power of transformer||Maximum power of generator|
|110 kV power line connection||25 MVA
|5 MVA (25 MVA*)|
* Only if the short-circuit current fed by the power plant is a maximum of 1.2 times the rated current of the power plant.