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Symbols - Fault Calculations

 C  voltage factor (IEC 60909)
 If  required through fault rating [kA]
 Ik

 steady state fault level [kA]
   Ik or Ik3                 - three phase fault
   Ik1                        - phase to earth (or phase to neutral) fault
   Ik2                        - phase to phase fault
   Ik2E or IkE2E          - phase to phase to earth fault

 I''k  initial symmetrical fault current kA
  I''k , I''k2 , I''k1 , I''k2 , I''k2E , I''kE2E        - as above
Irm  rated current of any motor A
 Isc min  minimum fault level [kA]
 Isc max  maximum fault level [kA]
 k  adiabatic equation factor
 pu

 per unit quantities
  Ibase         - per unit current base
  Pbase        - per unit power base
  Vbase        - per unit voltage base
  Ybase        - per unit admittance base
  Zbase        - per unit impedance base
  Zpu          - per unit impedance
  Z%          - per unit percentage impedance

 1,2, 3  symmetrical components
    Ua , Ub , Uc     - system voltages [V]
    U1 , U2 , U3     - symmetrical voltages [V]
    Z(1)                 - positive sequence impedance [Ω]
    Z(2)                 - negative sequence impedance [Ω]
    Z(0)                 - zero sequence impedance (Ω)
 t  earth fault duration [s]
 Z0  earth fault impedance [Ω]
 Zs  earth fault loop impedance [Ω]

 

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