ABSTRACT
American National Standards Institute (ANSI) methods of short-circuit calculations are used all over North America, and are accepted in many other countries. These standards have been around for a much longer time than any other standard in the world. The International Electrotechnical Commission (IEC) [1] standard for a short-circuit calculation was published in 1988, which is now revised [2], and the calculation procedures according to IEC are discussed in Chapter 11. A Verband der Elektrotechnik (VDE) [3] (Deutsche Electrotechnische Kommission) standard has been around since 1971. There has been a thrust for analog methods too. Nevertheless, for all equipment manufactured and applied in the USA industry, ANSI/Institute of Electrical and Electronics Engineers (IEEE) standards prevail. Most foreign equipment for use in the USA market has been assigned ANSI ratings. We will confine our discussions to ANSI/IEEE symmetrical rating basis of the circuit breakers. The USA is the only country that rates the circuit breakers on symmetrical current basis. The interpretations, theory, and concepts governing short-circuit calculations according to the latest ANSI/IEEE standards are discussed with illustrative examples.
