Evolving transmission gridField tower – economical transmission of electricity
2The design of the fieldtower intends to render thearable landscape airy andhence reduce the landscapedrawbacks of an electricitytransmission line.
12New tower for fieldsto facilitate cultivationFingrid has devised a new type of transmissionline tower, which is based on landowners’ andfarmers’ needs and wishes.The tower referred to as a field tower makesmore arable land available for cultivation andfacilitates the tillage of soil. The most noticeabledifference between the traditional tower types andthe field tower is that the field tower has no guywires; the tower is self-supporting. When workingon the field, it is no longer necessary to go aroundthe guys and look out for them.3One tower– two transmission linesIn a field tower, a 400 kilovolt transmission lineruns at the top and a 110 kilovolt line beneath it.There is a safety distance of 11 metres betweenthe conductors.The height of the tower is in the same range asthat of a conventional 400 kilovolt tower, where theupper crossarm is at a height of 31, 33 or 35 metres.The tower spacing is 300 to 450 metres.The field towers are primarily used in the constructionof new transmission lines. They can alsobe erected on existing lines in conjunction with thereplacement of a line or some its towers. The fieldtowers are made of galvanised steel. They can bepainted with a desired colour. The service life of thetowers is 80 to 100 years.
4The new field towerstands firmly on four legs,without guy wires whichimpede farming work.
Accessibilityand safetyAgricultural machinery can be operated morefreely near the new tower than in the vicinity ofconventional guyed towers. The most commonharrows, plant protection equipment and combineharvesters can run under the tower, since the spaceunder the tower is 7 metres in the longitudinaldirection and 14 metres in the cross direction of thetransmission line.Protective structures surrounding the legs of thetower prevent potential collisions with the legs. Inthis way, soil can be worked quite close to the tower.The lower structures of the new field tower aremuch more visible than the guys in the conventionaltowers. This also reduces the risk of collisions whenoperating machines.5Since the new towers have no guys, weedingproblems in the surroundings are also significantlyreduced.
6The structure and design ofthe field tower are devised towithstand decades of stress.The towers must be designedto accommodate winds andother demanding weatherconditions; in the winter aconsiderable ice load mayaccumulate on the lines.
Strength of steelon a concrete baseThe field tower stands firmly on four legs. Thefoundations of the tower are composed of twoprefabricated concrete sections joined together.This stabilises the tower structure. Separateconcreting work is not required, but the entirefoundation is built as prefabricated constructions.Each part of the foundation weighs 3 tonnes.In other words, the four-legged tower is anchoredto the ground using concrete foundations of 24tonnes.The tower is fastened to the four pillar elementsby means of anchor bolts. The mountingto the foundations and the loading of the towerhave been tested by the Tampere University ofTechnology. The tower with its base weighs almost40 tonnes. There are a total of 17 conductors onthe tower: 9 phase conductors in the 400 kilovoltline and 6 in the 110 kilovolt line. There also 2overhead ground wires. The heaviest of these isthe 400 kilovolt conductor, which weighs 2 kilosper metre.The material efficiency of the foundations andsteel structure is also an environmental asset. Thework stages related to the erection and maintenanceof the towers have been minimised, and thegoal is to schedule them at times when they causeleast harm to the farmer.The functioning, durability andsafety of the field tower have beensecured through a variety of tests.The test assembly of the towerrevealed that the details certainlyfit into place.Harmony of shapein the landscapeFingrid is an international trailblazer in combininghigh-quality industrial design and technicalconstructions. Special-design towers intended forbuilt-up areas and delicate landscapes are prominentexamples of the company’s approach whichrespects the environment. The oldest of these socalledlandscape towers date from the 1990s.The field tower carries on the same open-mindedapproach which has also attained internationalacclaim.The new tower is transparent and airy. It has alesser impact on the landscape than the traditionallattice design. This is of importance when thereare many towers in an arable landscape.Fingrid’s partners in the design of the newtower type have comprised the design agencyMuotohiomo Oy, Empower Oy which specialises inconsulting services in the energy industry, and theconcrete producer Betroc Oy.7
Powering Finland.FINGRID OYJLäkkisepäntie 21, P.O. Box 530, FI-00101 Helsinki, Finland | Telephone +358 30 395 5000 | Fax +358 30 395 5196 | www.fingrid.fi