Short-circuit current calculation: a comparison between methods of IEC and ANSI standards using dynamic simulation as reference

An essential issue concerning short-circuit studies is about how precise short-circuit calculations should be. Simplified procedures have been proposed for many years by International Committees to provide reference methods for manual computation and for the use of rated, rather than operating, equipment data. Recently, dynamic programs have been used to accurately simulate short-circuit currents. Two widely adopted international standards (ANSI/IEEE C37.010.1979 and IEC 909 Standards) are investigated in this paper for comparing and pointing out the most significant differences in methodologies, assumptions, computed currents, and results. An outline of the two standards is presented and a detailed comparison is carried out. The procedures of the two standards are applied to a test network proposed in the IEC 909 Standard. Results of calculations by the two standards are compared using the results of a transient study performed by the EMTP simulation program as a reference basis