The goal of this paper is to develop a technical comparison among different possible solutions for overhead transmission lines. These include both traditional and innovative solutions: the former are usual three-phase AC lines and HVDC lines, the latter are four-phase AC lines and combined AC-DC lines. Starting from a technical-economical comparison between aerial standard three-phase AC and innovative four-phase AC lines, which has been already developed, this paper first illustrates the main characteristics of the four considered solutions, pointing out the technical advantages provided by each one. Secondly, the paper performs a more detailed comparison based on a probabilistic analysis of the transient stability performances of the considered alternatives.
