The Design of the New $\pm 525 \text{kV}$ HVDC Overhead Line Tower for the Crossing of PO River

The Hypergrid project, presented for the first time by the italian TSO in the 2023 Grid Development Plan, foresees the construction of new <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 525 \text{kV}$</tex> dc overhead lines (OHLs) to replace the existing 400 kV ac OHLs. One of the first overhead lines to be implemented is the Milano-Montalto link. This connection will consist of an undersea cable from Montalto to La Spezia and an overhead line from La Spezia to Milano. This line presents specific challenges, such as crossing the Tuscan-Emilian Apennines, where intense rime ice phenomena occur, and crossing the Po River. Regarding the latter, it was necessary to design a special tower to enable the crossing of the Po River. The considerable height of the tower (about 120 meters), the great span length and the high rated voltage require specific design choices to ensure an acceptable lightning fault rate and adequate clearances. The paper describes the constraints and studies conducted to achieve a sustainable design of the infrastructure.