This article provides a comprehensive overview of what the IEC 949 standard contains, why it is vital for cable sizing, and how to correctly access and utilize the for your projects.
Find the for a specific material like lead or steel? Compare this to IEC 60287 (steady-state ratings)? iec 949 pdf
: First, the "adiabatic" short-circuit current is calculated. This assumes the fault is so fast that no heat escapes the conductor, leading to a conservative, "worst-case" thermal estimate. This article provides a comprehensive overview of what
IAD=K⋅St⋅ln(θf+βθi+β)cap I sub cap A cap D end-sub equals the fraction with numerator cap K center dot cap S and denominator the square root of t end-root end-fraction center dot the square root of l n open paren the fraction with numerator theta sub f plus beta and denominator theta sub i plus beta end-fraction close paren end-root IADcap I sub cap A cap D end-sub is the permissible adiabatic short-circuit current (A). is the cross-sectional area of the conductor ( mm2m m squared is the duration of the short-circuit (s). is the material constant. θitheta sub i is the initial temperature before the fault ( ∘Craised to the composed with power cap C θftheta sub f is the final permissible temperature after the fault ( ∘Craised to the composed with power cap C : First, the "adiabatic" short-circuit current is calculated
: A specific factor is then calculated to account for heat dissipation into adjacent materials, such as cable insulation or surrounding soil.