A comparison of ANSI-based and dynamically rigorous short-circuit current calculation procedures

Standards and procedures used in the application of power circuit breakers are correlated according to short-circuit current, both as prescribed by the empirically based ANSI (American National Standards Institute) standards and using a dynamically rigorous procedure. The correlation is made in order to determine the degree of accuracy of the simplified empirical ANSI calculation procedure, which is composed of short-circuit calculation techniques of the predigital computer era. With the use of modern computer capabilities, a greater degree of accuracy is possible in determining the limits of these standards and methods. A brief qualitative comparison of the procedures promulgated in the two methods is presented. Their correlation is further tested by carrying out a short-circuit calculation on a specific industrial system design. The study results are tabulated and reviewed to identify their unique characteristics. The broad conclusion is that the ANSI short-circuit values are higher and hence more conservative than the more dynamic rigorously calculated values.<>