The standard provides formulas based on the physical properties of the conductor and insulation. The primary calculation revolves around the . The formula requires several inputs:
The standard uses the following fundamental equation for adiabatic conditions: iec 949 pdf
$$ J₀ = \fracIS = \frac143.2\sqrtt ; \textA/mm² $$ The standard provides formulas based on the physical
Meeting international safety requirements for high-voltage power installations. Material Selection: Using material-specific constants ( ) and temperature factors ( ) for copper, aluminum, lead, and steel. Where to Get the Document iec 949 pdf
Traditional calculations assume all heat generated by a short-circuit is trapped within the conductor for the duration of the fault (typically up to 5 seconds). This is a conservative "worst-case" scenario. Non-Adiabatic Factor:
: For longer short-circuit durations, this method accounts for the heat absorbed by the surrounding cable components (insulation, sheaths, or bedding). This allows for a more accurate—and often higher—current rating than the adiabatic method. Key Technical Sections