General planning of the power cable connection

During general planning, a route and construction plan for the 400 kV power cable connection, an expropriation plan for the right of use to the 400 kV cable route, an extension of the Länsisalmi substation, the Vanhakaupunki substation and a route study for transformer transport will be planned.

The aim is to complete the general planning phase in 2022 for a construction agreement and final investment decisions by the parties.

Project details
Project type: Underground cable
Project state: General planning phase
Location: Helsinki, Vantaa
Length: About 12 km, depending on the final route selection


Ramboll Finland Oy has been chosen in May 2021 as the consulting company used for the general planning.

Parviainen Arkkitehdit Oy has been chosen in April 2021 for substation architectural and structural planning.

Further information:

400 kV power cable connection

A power cable connection will be constructed between the Länsisalmi substation and the Vanhakaupunki substation. The transmission capacity of the cable link will be approximately 1,000 MW and the project is prepared to implement a structural reservation for a double circuit.

The general planning phase of the cable link will decide the final cable route from the routes examined in the environmental study, which are presented below. The route length will be about 12 km, depending on the final route selection. Right of use to the cable route will be acquired through an expropriation procedure.


The cable will be installed underground and where the urban environment will limit the construction area width, a supported excavation method will be used. In the supported method the width of the bottom of the cable excavation is a couple of metres (image of the left). In a spacious environment, the cable can be built as a ramped excavation (image on the right).


Länsisalmi substation

General planning includes planning of the extension of the current gas-insulated switchgear (GIS) plant of the Länsisalmi substation in Vantaa (in the images below) by at least one bay. In addition to the yard to be extended, the switchgear already has a space reservation for a double circuit.

The power cable will generate reactive power, which reduces the transmission capacity of the cable and primary equipment of substations and increases their voltage and power losses.  The reactive power generated by the cable will be tentatively compensated at the Länsisalmi substation by a 400 kV reactor connected to the cable and by 20 kV reactor plants connected to the tertiaries of the transformers.

Länsisalmen sähköasema webresoluutiokuvia (ID 10646).jpg



Vanhakaupunki substation

General planning includes planning of the construction of the new Vanhakaupunki 400/110/20 kV substation in Viikinmäki, Helsinki.

The switchgear will be implemented as a gas-insulated switchgear (GIS) plant and the structure is a duplex structure. The design of the switchgear is prepared for the construction of a double circuit. In addition to the GIS plant, at least one new main transformer will be acquired for the substation.

The image below illustrates the location of the Vanhakaupunki transformer substation near the Lahti Highway and the Vanhankaupunginkoski rapids. The substation will be located next to Helen Electricity Network's current Viikinmäki substation.


Transformer transport route

General planning will ensure the final transport route of the main transformer of the new Vanhakaupunki transformer substation. The transformer will be transported from Vuosaari Harbour by land to Viikinmäki. The transport route has received a preliminary decision from the Centre for Economic Development, Transport and the Environment. The preliminary transformer transport route is shown in the image below.


A platform will be used for the transformer's road transport. Below is an illustrative example of a transformer on a platform.




Fingrid Oyj

Risto Ryynänen

Project Director 
tel. +358 30 395 5219

Jussi Rantanen

Project Manager (cable connection)
tel. +358 30 395 5274

Jarmo Henttinen

Project Manager (substations)
tel.+358 30 395 4280

e-mail addresses:


General planning consulting company Ramboll Finland Oy

Martti Maljanen

Project Manager
tel.+358 50 361 7736


Architectural planning Parviainen Arkkitehdit Oy

Bratislav Toskovic

tel.+358 50 589 6913