The standard follows a specific three-step calculation process to determine the final permissible current: Calculate Adiabatic Current ( cap I sub cap A cap D end-sub
: The resulting figure yields the real-world, optimized permissible short-circuit current .
To perform a calculation manually or set up an engineering software suite (such as ETAP or CYME) according to IEC 949, follow these steps:
) : Apply a modifying multiplier that credits the cable for heat absorbed by adjacent materials.
The standard was originally published in 1988 and updated with . Core Calculation Methodology
: Initial operating temperature immediately before the fault ( ∘Craised to the composed with power C θftheta sub f : Maximum permissible final temperature after the fault ( ∘Craised to the composed with power C
IEC 949 PDF work has numerous applications in the industrial sector, including:
factors buried in the PDF’s tables, he was guessing. And in high-voltage engineering, a guess is just a slow-motion disaster.
The duration of the fault (longer faults allow more heat to escape, increasing the value of Step-by-Step Engineering Workflow