Economics of EHV High Phase Order Transmission

The economics of high phase order transmission (six or twelve phase lines) are compared to UHV three phase. The comparisons are developed from optimized line designs, based on realistic lifetime costs. Detailed structure designs were used in the study, with terminal equipment costs included to develop- a breakeven distance beyond which savings in the HPO transmission line offset any increased substation costs. This breakeven distance is typically only a few miles, i. e. much shorter than projected UHV lines. A sensitivity analysis allows the general conclusion to be drawn that high phase order is econocmically compettivei- with UHV. Additional advantages are that the HPO structures are significantly smaller, and the ROW probably significantly narrower.