Costs study of 69- to 345-kv overhead power-transmission systems

ABOUT 25 years ago when the highest transmission voltage in this country was approximately 160 kv, Silver analyzed the possibilities of 220-kv power transmission in a paper presented to the Institute.¹ Since then numerous 230-kv lines have been built, and in one case a 287-kv transmission line was constructed. In the meantime the question of power supply from local and distant steam-power stations, or from distant hydro-electric stations, was quite active, and papers on this subject were written by Fortescue,² Fowle,³ and Funk⁴ in this country, and by Rüdenberg⁵ and Vögeli⁶ in Europe. In every case the authors estimated the costs of transmission lines of various voltages and mileages, frequently making liberal assumptions and simplifications, especially in regard to line design and system-stability requirements. Until now, however, there has been no generally accepted view as to the economics of transmission lines at very high voltages, and particularly as to the relationship between the voltage, the block of power transmitted, and the transmission distance as these affect the total cost of the project. In view of this, and because of postwar construction projects and coming developments in the art of power transmission (such as d-c transmission), it seems appropriate that a cost study of a variety of transmission projects be made on a more or less uniform basis, with similar standards of requirements applied in all cases.