If you obtain the official IEC 949 PDF, you will find detailed mathematical models. The most critical takeaway is the modification of the standard short-circuit temperature rise formula.
The International Electrotechnical Commission (IEC) published IEC 949, a guide on planning and implementation of industrial automation and control systems (IACS). This standard provides guidance on the planning, design, implementation, and operation of IACS. iec 949 pdf
You can find the standard and its latest amendments through official channels: IEC 60949:1988 - European Standards If you obtain the official IEC 949 PDF,
: For conductors with cross-sectional areas less than 10mm210 m m squared , the increase in permissible current can be significant. This standard provides guidance on the planning, design,
The standard formerly known as (now integrated into IEC 60949 ) provides the calculation methods for determining the thermally permissible short-circuit currents for electrical cables. It is primarily used to ensure that a cable’s conductor, screen, or sheath can withstand the rapid heat rise during a fault without exceeding its temperature limits. Core Content of IEC 60949