The North Karelian main grid will be reinforced in three phases

Finland will begin to renew the main grid’s 110 kilovolt transmission lines in North Karelia next year. The wooden towers are more than 50 years old and aging. They will be replaced with sturdy steel towers, which can also withstand heavy hoarfrost loads in the winter.

In total, 112 kilometres of transmission lines will be renewed. The first project covers 20 kilometres of old line between Uimaharju and Pamilo. The second involves the renewal of the 53 kilometre stretch of line between Kontiolahti and Uimaharju. During the third phase, the Kontiolahti-Pamilo transmission line, which is 39 kilometres long, will be renewed.

The transmission lines form a triangle located in challenging terrain. The transmission lines run across an area which is marshy in places and which features large differences in elevation.

“Based on experience, we know that ice load builds up on the towers in the winter, which places strain on the towers and overhead ground wires. We’ve taken this into account when designing the structures of the transmission lines. The current wooden towers will be replaced with sturdier steel tubes, and the crossarms for overhead ground wires will be situated higher than normal. The spans between towers will also be shorter than usual,” explains Fingrid’s Senior Project Manager Antti Linna, who is responsible for the construction of the transmission lines.

The new steel towers will not differ in appearance from the main grid’s other transmission line towers.

Investment in future transmission needs

The main grid reinforcement means that the 110 kilovolt transmission lines located in Kontiolahti municipality and areas surrounding the city of Joensuu will better serve the area’s future demand and transmission needs.

In addition to houses, there is a lot of industry in the area, such as Stora Enso’s Uimaharju plants, Vattenfall’s Pamilon power plant, as well as electricity distribution companies Pohjois-Karjalan Sähkö and Caruna.

During project planning and scheduling, Fingrid cooperated with its local customers to find the best solutions to ensure that the contract would have as little impact as possible on the customers’ daily lives.

“Line renewal will cause outages in Fingrid’s grid and changes to customers’ networks. The aim is to keep these outages from manifesting in any way to the area’s residents,” promises Linna.

The first Contract will begin in 2019

General planning of the reinforcement of the North Karelian main grid began last autumn. During general planning, the transmission line is designed and the choice of the transmission line’s route is finalised. The final route and location of towers will be chosen based on terrain surveys.

“The locations of towers along the stretch of line between Uimaharju and Pamilo are already planned and landowners’ feedback has been heard. The round of tendering for this contract will begin in September. According to plans, the Uimaharju-Pamilo transmission line will be built between January and September 2019,” says Linna.

Phase two, which concerns the construction of the Kontiolahti-Uimaharju transmission line, will begin in summer 2019 and is scheduled for completion in 2020. The Kontiolahti-Pamilo transmission line contract, which makes up the last side of the triangle, is expected to be complete in 2022.

Almost all of the main grid’s transmission lines in the North Karelia project are built either along or alongside an existing line. The renewal of the network will involve a widening of the transmission line area along a stretch of around eight kilometres between Kontiolahti and Tarhola.