La Spezia-Vignole is an old but critical transmission line that connect the North-West region with the center and South of Italy. This 113km long 400kV line is split in 65km twin bundle and 48km single bundle. The single bundle conductor is used on the region with extreme ice loading (up to 16kg/m) however this caused a bottle neck on the line reducing the power transmission capacity. For this reason in 2011 Terna published a tender for design, test, supply and installation of a new single bundle conductor with ampacity more than 2300 A.
The current single bundle conductor was an Hollow type ACSR conductor Ø50mm.
De Angeli Prodotti developed a tailor made solution using an innovative Ø49mm High Temperature All Aluminium Alloy Conductor.
The solution combines the simplicity and reliability of a standard design with the high performance of AT2 special aluminium alloy, giving a conductor with a similar diameter (important for the corona) higher mechanical strength (+5%), lower weight (-2%), lower electrical resistance (-22%) and allowing an ampacity increase up to 2700 A (+52%) in Winter condition and 2440 A (+72%) in Summer condition.
Furthermore the conductor thanks to its very low electrical resistance enables more than 26% line losses reduction.The conductor properties have been widely tested (tensile strength, stress-strain, thermal resistance, creep, fatigue and self-damping) with excellent results and a final on field installation test proved the feasibility and the ease of use. Thanks to the positive result the installation has been approved and the line will be renewed with the new conductor during 2014 and 2015, in partnership with the installer company RODA spa.
Figure 1. Picture of real Ice loading condition on TERNA 400kV La Spezia-Vignole overhead line
The conductor Ø49mm AAAC AT2 developed by De Angeli Prodotti successfully replaced the Hollow type ACSR on 400kV single bundle electrical 400kV line giving an ampacity increase of more than 50%. This helped to solve the problem of congestion of the Italian power grid.