When you open an official PDF copy of the IEC 949 standard, the document is typically structured into the following critical sections:
: This is the counterpart for higher voltage systems, covering short-circuit temperature limits for cables with rated voltages from 6 kV up to 30 kV . It explicitly states that calculations of the admissible short-circuit current should be performed in accordance with IEC 60949.
IEC 60949 remains a cornerstone of electrical safety engineering. By providing a method to accurately calculate thermally permissible short-circuit currents, it empowers professionals to design cable systems that are both safe and economically optimized. Its accounting for non-adiabatic heating effects offers a more nuanced and realistic picture of cable behavior under fault conditions.
Where:
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Calculation of thermally permissible short-circuit currents, taking into account non-adiabatic heating effects. Key Methodology: The standard uses a three-step process:
) : A factor is calculated to account for the specific heat dissipation into the cable's insulation and surroundings. Find the Permissible Current (
| | Resistivity (ρ) at 20°C (Ω·m) | Specific Heat Capacity (c) (J/(kg·K)) | Melting Point (°C) | | :--- | :--- | :--- | :--- | | Copper | ( 1.72 \times 10^-8 ) | 385 | 1083 | | Aluminum | ( 2.65 \times 10^-8 ) | 900 | 660 |
): Step-by-step breakdown of how to compute heat loss for specific configurations, including: Conductors in direct contact with insulation. Structural screens, metallic sheaths, and armouring wires. Bundled vs. isolated conductors. When you open an official PDF copy of
IEC 60949 is not just a theoretical document; it is a practical tool used by leading manufacturers and design engineers worldwide.
Verifying that cable screens, sheaths, and conductors do not melt during a fault.
The core feature for any IEC 949/60949 PDF tool is the calculation of the permissible short-circuit current using the formula
Determine a correction variable based on the physical properties and dimensions of the adjacent layers (e.g., insulation, bedding, or sheaths) to account for heat escaping out of the conductor. By providing a method to accurately calculate thermally
The PDF provides tables and coefficients (insulation thermal resistivity, specific heat of materials) to calculate a larger permissible current than the adiabatic method would allow.
: Provides regional access to the standard for various markets. sample calculation
Calculate the standard baseline .