Lightning Performance Assessment of the New $\pm 500 \text{kV}$ HVDC Overhead Lines of the Italian Transmission Grid

This work addresses the lightning performance evaluation of the new <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 500 \text{kV}$</tex> HVDC overhead lines of the Italian transmission grid, part of the Hypergrid project, specifically focusing on direct lightning strikes to the pole conductors and the towers/shield wires of the line. The lightning performance evaluation procedures outlined by the international standard IEEE Std 1243 and the technical guidelines of CIGRE TB 63 are employed to estimate the shielding failure flashover and backflashover rate of the line. A comparison is made between different electrogeometric models regarding the shielding efficiency of the overhead line against direct lightning strikes. The results of this study indicate that, due to the relative positioning of the shield wires and pole conductors, forming a negative shielding angle, the shielding failure flashover rate of the line is practically zero. Furthermore, a negligible backflashover rate to the line is deduced for a reasonable range of lightning peak currents, due to the positioning of the underbuilt metallic return conductors, which provide additional protection to the pole conductor in the event of a backflashover scenario.