Analysis and Application of IEC 949: A Framework for Calculating Thermally Permissible Short-Circuit Currents in Cables

This paper provides a comprehensive review of (now superseded by IEC 60949 ), the international standard governing the calculation of thermally permissible short-circuit currents in electric cables. The paper explores the theoretical basis of the standard, focusing on the adiabatic heating model used to determine the maximum current a cable conductor can withstand before sustaining irreversible insulation damage. It details the mathematical formulation, the critical parameters involved—such as initial and final temperatures and conductor materials—and discusses the practical implications for electrical system design, specifically in the selection of cable sizes and protective devices.