Earth Conductor Sizing (Adiabatic)

Fault Parameters

kA
sec
(Disconnection time of protection device)

Conductor Details

Sizing Results

Fault Energy (I²t) - MA²s
Min Area (Calculated) - mm²
Nearest Standard Size - mm²

*Calculated using the Adiabatic Equation (S = I√t / k). Suitable for disconnection times < 5s.

Technical Notes & Engineering Logic

Variable Definitions

  • If (Fault Current): The RMS value of prospective fault current (kA).
  • t (Time): Operating time of the protective device (seconds).
  • k (Factor): Constant depending on material resistivity, heat capacity, and initial/final temperatures (IEC 60364-5-54).

Formulas

  • Adiabatic Equation: S = (I × √t) / k
  • Energy Let-through: E = I²t (Thermal stress on conductor).
  • Where I is in Amps, t in seconds, S in mm².

Assumptions/Constraints

  • Assumes adiabatic heating (no heat loss to surroundings during fault).
  • Valid for disconnection times t ≤ 5 seconds.
  • Does not account for mechanical strength constraints (e.g., min 2.5mm² for protected mech, 4mm² unprotected).
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