2/2012 - Fingrid
2/2012 - Fingrid 2/2012 - Fingrid
PUTTING THETOWERS TO THE TESTFingrid testing its mostcommon tower typesA transmission line tower must be able to withstand considerable loadsin the Finnish conditions. It must stand without breaking in heavy windsand burdened by ice loads accumulated on the structures. To securethis, Fingrid has launched a comprehensive testing programme, whichcovers all the type towers used in the company’s transmission lines.Text by Maria Hallila | Photographs by Ritva LaineThe testing programme is based ona project aiming to put together a“tower family” of Fingrid’s typetowers. It would cover up to 90 per centof the tower types most commonly usedby the company. According to ProjectManager Ritva Laine, the number oftype towers selected in the family isclose to 30.“By having an established basic rangeof towers and by using ready-madeplans, we can intensify and expediteboth the construction of transmissionlines and line maintenance,” she says.Not many testing stationsDuring her career of more than 20years, Ritva Laine has participated inthe testing of 20 or so transmission linetowers. In the past four years the testshave concerned the so-called type towers.The tests for the new towers usedon the overhead line section of the Est-Link 2 transmission interconnection betweenFinland and Estonia have beenconducted under the supervision of ProjectManager Ritva Hauvonen.What makes the testing of the towerscomplicated is the fact that there arenot that many testing stations available.In Europe, there are such facilities onlyin Spain, Italy and Romania, and onlythe one in Romania enables the testingof guyed 400 kilovolt transmission linetowers more than 30 metres in height.Fingrid has had towers tested alsoin China, where the testing station isunique in that it can test towers as highas 140 metres.“The testing station in China is lessfavourable than its European competitorsin terms of logistics. There is nopoint in transporting the towers there,so they are manufactured in China,”Ritva Laine says.She says that this is sometimes standardpractice also with European testingstations. Tubular towers are mostlymanufactured in Finland and transportedto the testing site in parts by road.Ritva Laine and Ritva Hauvonencommend the Romanian testing stationfor service flexibility, activity and responseability. The station has acquirednew equipment and facilities specificallyfor Fingrid’s needs.Efficiency from ITThe strength requirements applied totowers used in the Finnish high-voltagetransmission system are laid down inEuropean transmission line standards.FINGRID 2/2012 | 10
Fingrid’s type towers havepassed the strength testswithout any major problems.The load has been raised to justover 100 per cent of the testload, whereby the steel bendssomewhat in accordance with itscharacteristics.The tests model a range of forces exertedon the towers – for example ice,wind, installation and safety loads – bymeans of pull wires, pulleys and winchesattached to the structures. The testsverify that the strength calculations ofthe tower hold true and that all jointsare correctly designed.Ritva Laine says that it typically takesabout four months for a single tower tobe manufactured, transported, erected,tested and dismantled. The actual testingby the current methods can be carriedout within one working day.Information technology has gained anincreasingly important role in the testingprocess in recent years. “As a result,the testing times are now shorter andthe work stages have become easier.Information technology has also improvedthe manageability and safety ofthe tests,” she adds.The testing programme detects, forexample, if the tower bends too muchat some point. “In such a case, the loadis released automatically, and there isno damage or accident.”Solid structuresThe testing of transmission line towerscomplies with the relevant Europeanstandard. According to Ritva Laine andRitva Hauvonen, Fingrid’s towers havepassed the strength tests without anymajor problems.“There have been slight problems afew times during the tests, but the testshave been completed successfully aftercorrecting these problems,” they say.The testing takes place in stages: theload is first adjusted to 50 per cent andthen gradually to 75, 90, 95 and finallyto 100 per cent of the limit value set forthe capacity of the tower.The testing can continue even afterthe 100 per cent load level has beenreached. “This is not mandatory on thebasis of the standards, but it is a way offinding out what the tower really withstands.The information may be usefulwhen the goal is to optimise materialcost-effectiveness, for example,” RitvaLaine says.After testing, the tower is dismantled,and it is examined whether the deflectionshave remained within the prescribedlimits. A tower that passes thetest is included in Fingrid’s type towerfamily.FINGRID 2/2012 | 11
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<strong>Fingrid</strong>’s type towers havepassed the strength testswithout any major problems.The load has been raised to justover 100 per cent of the testload, whereby the steel bendssomewhat in accordance with itscharacteristics.The tests model a range of forces exertedon the towers – for example ice,wind, installation and safety loads – bymeans of pull wires, pulleys and winchesattached to the structures. The testsverify that the strength calculations ofthe tower hold true and that all jointsare correctly designed.Ritva Laine says that it typically takesabout four months for a single tower tobe manufactured, transported, erected,tested and dismantled. The actual testingby the current methods can be carriedout within one working day.Information technology has gained anincreasingly important role in the testingprocess in recent years. “As a result,the testing times are now shorter andthe work stages have become easier.Information technology has also improvedthe manageability and safety ofthe tests,” she adds.The testing programme detects, forexample, if the tower bends too muchat some point. “In such a case, the loadis released automatically, and there isno damage or accident.”Solid structuresThe testing of transmission line towerscomplies with the relevant Europeanstandard. According to Ritva Laine andRitva Hauvonen, <strong>Fingrid</strong>’s towers havepassed the strength tests without anymajor problems.“There have been slight problems afew times during the tests, but the testshave been completed successfully aftercorrecting these problems,” they say.The testing takes place in stages: theload is first adjusted to 50 per cent andthen gradually to 75, 90, 95 and finallyto 100 per cent of the limit value set forthe capacity of the tower.The testing can continue even afterthe 100 per cent load level has beenreached. “This is not mandatory on thebasis of the standards, but it is a way offinding out what the tower really withstands.The information may be usefulwhen the goal is to optimise materialcost-effectiveness, for example,” RitvaLaine says.After testing, the tower is dismantled,and it is examined whether the deflectionshave remained within the prescribedlimits. A tower that passes thetest is included in <strong>Fingrid</strong>’s type towerfamily.FINGRID 2/<strong>2012</strong> | 11
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