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Replacing overhead power lines with underground cables, slowly but surely

Work to replace overhead power lines with underground cables has been slow in Finland, but news agency STT reports that things are looking to pick up in this area, thanks to new legislation.

Fingridin voimalinjoja Ylikkälässä.
Finngrid power lines in Ylikkälä. Image: Fingrid

Seasonal storms pummel Finland with increasing regularity, downing overhead power lines and causing large-scale blackouts that sometimes last for several days. Taking a cue from Sweden, Finland changed its legislation to ensure better supply security a few years ago, and Finland's Energy Authority forecasts investments in underground cables will soon begin in earnest.

The authority estimates that 19 percent of the country's medium-voltage network and 42 percent of the low-voltage network runs underground, leaving the rest to be carried by overhead power lines. Efforts to replace overhead lines with underground cables have only made about one percentage point of progress every year, even though putting the lines out of the reach of falling trees and wet snow improves supply security considerably.

According to the national power grid operator Finngrid, the use of underground cables is limited because they are prohibitively expensive due to the long transmission distances. The buried cables also restrict land use in the areas where they are installed.

New legal limits on power outages

The Energy Authority's objective is to eventually put 47 percent of the medium-voltage network and 65 percent of the low-voltage network below ground by the year 2029.

A 2013 reform of the electricity market act defines limits on maximum allowed interruptions in service. The new law states that snow and storms cannot knock out power for more than six hours in urban areas and 36 hours in rural locations. By 2019, 50 percent of customers must fall within the scope of the outage limits, rising to 75 percent in 2023, and 100 percent by 2028.

"The new law only came into effect in 2013, and the power companies are slowly setting their investment plans to comply with it in motion. Our developmental forecasts give us reason to believe that we will reach the objectives," says the Energy Authority's director Veli-Pekka Saajo.

Last year Finland's energy companies invested 850 million euros in distribution networks, a project that is expected to cost several billion euros before all is said and done.

Large regional differences

As Finland embarks on this significant infrastructure project, it is taking a lot of its cues from Sweden, where a similar supply security reform kicked off a large-scale underground cabling wave after destructive storms downed power lines throughout the country in 2005 and 2007.

The challenge is most acute for companies that operate in areas with difficult terrain and haven't started to lay underground cables at all, most of which are concentrated in eastern and northern Finland and Ostrobothnia.

At the end of 2015, differences between Finland's electricity companies in this area were pronounced. For example, only 14.6 percent of North Karelia's PKS Sähkönsiirto's and 22.7 percent of eastern Järvi-Suomen Energia's low-voltage grid was underground, compared with Caruna's 39 percent rate in southern and western Finland and Helen's 97.7 percent coverage in Helsinki.

Saajo says the Energy Authority has gone through the development plans for the coming years with all of Finland's power companies. He reports that negotiations have successfully overcome compliance problems to date, so the authority hasn't had to resort to tough tactics.

"We've received three applications for transition period extensions," he says.

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