G. Knight et H. Sieling, COMPARISON OF ANSI AND IEC 909 SHORT-CIRCUIT CURRENT CALCULATION PROCEDURES, IEEE transactions on industry applications, 29(3), 1993, pp. 625-630
Although ANSI fault calculation methods are designed to determine a va
lue to compare with the equipment ratings, the IEC 909 Standard presen
ts a method that inherently more accurately models the fault currents
that flow. The IEC method requires significantly more complex modeling
of the power system fault contributions than ANSI requires. By unders
tanding the calculation differences, the difference in equipment ratin
gs becomes more insightful.