The Loadability of Overhead Transmission Lines—Part II: Analysis of Double-Circuits and Overall Comparison

This is the second part of an investigation aimed at providing a thorough technical comparison between traditional and alternative overhead power transmission lines based on the loadability characteristics. The previous Part I outlined and applied the fundamentals of the loadability analysis to three comparable single-circuit lines. In Part II, the analysis is broadened to three comparable double-circuit lines: traditional three-phase ac double-circuit lines (assumed as the reference system for the comparison) and bipolar HVDC lines and nonconventional combined ac-dc lines. As in Part I, the loadability analysis takes into account thermal limits, voltage drop, power losses, and - when feasible - steady state and transient stability. Part II also performs an overall comparison among the different systems in single-circuit and double-circuit configuration to draw final conclusions.