Modernisation of the Imatra–Huutokoski transmission line, which ensures electricity transmission between South Savo and South Karelia

The original 110 kV Imatra–Huutokoski power line, which was commissioned in 1934, has reached the end of its service life. A new transmission line will guarantee Fingrid’s transmission reliability in the South Savo region and boost the main grid’s electricity transmission capacity in South Karelia under various operating circumstances.

A new transmission line will be built over a distance of approximately 130 kilometres. There are a total of 11 Fingrid customer connections along the Imatra–Huutokoski transmission line. At these connection points, distribution system operators transmit electricity from the transmission line to end-users. The improvements to the electricity network are being planned and implemented in close cooperation with these electricity distribution system operators in the region. The work is demanding, and it requires good planning. The project will result in a more reliable network for the region, and transmission reliability will remain strong long into the future.

Challenging project divided into two parts

The project is divided into construction sections A and B. The contractor in section A (Imatra–Puumala) is TMV Line Oy, and Destia Ltd will work on section B (Puumala–Aittasuo).

The customer connections will make the transmission line construction phase more challenging, as transmission outage during construction must be carefully planned so as to minimise the electricity transmission disruptions affecting customers. “Transmission outages are challenging because they momentarily reduce system security in the region. In general, a section of the line that is not in use can be replaced without disrupting the electricity supply. However, when a section is taken out of use, the network becomes more susceptible to unforeseeable faults, such as disruptions due to lightning strikes. Customers may experience brief power cuts as a consequence of disruptions,” says Petri Hentunen, a specialist in operational planning at Fingrid.

The project will be completed in 2023 rather than autumn 2022 as originally scheduled. “Challenges are a part of project work, but there have been a lot of them in this project entity. However, the impacts of the coronavirus pandemic have not significantly affected the progress of this project, except for some minor delays in material deliveries,” says Tommi Olsson, Project Manager at Fingrid. Overall, the network reinforcements will cost Fingrid approximately EUR 24 million.

Ordinary households will barely notice the network construction work or the outages that take place while work is underway. Households can prepare themselves for the possibility of brief power cuts by reading the guidelines provided by local electricity distribution companies concerning power cuts. Outages are always temporary. When the new transmission lines are completed, they will strengthen the network and further improve the reliability of electricity distribution in the region.

Additional information:

Section A, Imatra–Puumala

Tommi Raussi, Fingrid Oyj, Project Manager
tel. +358 30 395 5173

Section B, Puumala–Aittasuo

Tommi Olsson, Fingrid Oyj, Project Manager
tel. +358 30 395 4151