High phase order economics: constructing a new transmission line

Due to licensing, environmental laws, customer concerns and tighter transmission corridors, it has become increasingly difficult to build new transmission lines. One alternative to address these problems is the use of six-phase transmission lines. Six-phase transmission lines can provide the same power capacity with a lower phase to phase voltage and smaller, more compact towers as compared to a standard double circuit three-phase line. The geometry of the six-phase compact towers may also aid in the reduction of magnetic fields. This study compares the installation costs of constructing a standard 115 kV double circuit three-phase transmission line to constructing a 66 kV six-phase transmission line to illustrate that the use of six-phase transmission can be a cost effective solution to address some these problems. Both standard and constrained rights-of-way (ROW) are considered. Also the effect of incorporating losses in the evaluation is investigated.