The goal of this paper is assessing the economic
feasibility of four-phase AC overhead connections, i.e. the
real chance that such lines have of being competitive with
commonly-used solutions for power transmission. For this
reason, the paper illustrates an economical comparison
among innovative 325 kV four-phase ac lines, traditional
400 kV three-phase ac lines and increasingly-popular 500
kV HVDC lines. These systems are considered firstly in
single-circuit and secondly in double-circuit overhead
arrangement. The comparison is based on the main cost
items that characterize these lines, namely investment costs,
energy losses costs and reliability-related costs. The
uncertainty of the relevant parameters, particularly
significant as far as innovative four-phase ac lines are
concerned, is also discussed.
