Discussion on “protective reactances in large power stations” (Lyman, Rossman and Perry), New York, February 25, 1914. (see proceedings for February, 1914)

Philip Torchio: The authors have assumed that the generators have 10 per cent internal reactance, and some of the curves have been figured on that percentage. Although there may be modern machines that are being designed with the object of high internal reactance in view which have an internal reactance as high as stated, the great majority, or practically all of the machines in central stations at the present time, have internal reactances considerably smaller than 10 per cent. On 25-cycle machines the internal reactance will be 5 per cent or less. In such cases if you had assumed 5 per pent internal generator reactance, the figures and curves presented would have been considerably different and would have shown that there is little gain in installing bus reactances in excess of 12 to 15 per cent.