Transmission system operator Fingrid Oyj has developed a transmission line tower, in cooperation with design agency Muotohiomo Oy, for use in fields. The objective was to devise a new type of double-circuit tower for 400-kV and 110-kV transmission lines that would minimize the disadvantage inflicted on agriculture, improve occupational safety, and facilitate soil preparation and cultivation.

The height of the tower is in the same range as that of a conventional 400-kV tower, where the upper crossarm is at a height of 31 m to 35 m (102 ft to 115 ft). The most notable difference between the field tower and conventional tower types is that the field tower has no supporting guy wires. Agricultural machinery can be operated more freely near the new tower than in the vicinity of conventional guyed towers. Many common agricultural machines can run under the tower, because the space under the tower is 7 m (23 ft) in the longitudinal direction and 14 m (46 m) in the cross direction.

Protective structures surrounding the legs of the new tower prevent potential collisions with the legs. In this way, soil can be worked quite close to the tower. Since the new towers have no guys, weeding problems in the surroundings are reduced.

The foundations of the tower are composed of two prefabricated concrete sections joined together. Each part weighs 3 tonnes (3.3 tons). The four-legged tower is anchored to the ground using foundations of 24 tonnes (26.4 tons). Separate concreting work is not required, but the entire foundation is built as prefabricated constructions.

The field towers primarily will be used in the construction of new transmission lines. They also can be erected on existing lines in conjunction with the replacement of a line or its towers. The field tower is used on the 400-kV transmission line between the Ulvila Substation in Pori and the Kristinestad Substation in Kristiinankaupunki in Western Finland. However, conventional structures are used for most of the transmission line route, because the line primarily runs in forest.

When completed in 2014, the 115-km (71-mile) power line will replace the technically outdated transmission network in the region. In Western Finland, preparations also must be made for an increase in electric transmission needs. Electricity consumption has grown particularly rapidly in the Vaasa, Kristiinankaupunki and Seinäjoki regions. The project will achieve significant savings in the form of reduced loss energy.

The transmission line between Pori and Kristiinankaupunki is part of the long-term development plan of the Finnish transmission grid, making preparations for integrating new electricity generation capacity (wind and nuclear power) to the grid. Consequently, Fingrid's capital expenditure has grown significantly and will total more than 260 million euros this year.

Fingrid intends to build 3,000 km (1,864 miles) of new transmission lines and about 30 substations. Approximately 90% of the new transmission lines will be built in existing rights-of-ways or parallel with them, which will reduce the inconvenience inflicted on landowners.

For more information, visit www.fingrid.fi.