Fault Current Calculation Online

( I_f = 1.0 / 0.09 = 11.11 , \textpu )

[ I_base = \frac10 \times 10^6\sqrt3 \times 13.8 \times 10^3 = 418.4 , \textA ] [ I_f = 11.11 \times 418.4 = 4648 , \textA \quad (\textsymmetrical RMS) ] fault current calculation

[ Z_util = \fracS_baseS_sc = \frac101000 = 0.01 , \textpu ] ( I_f = 1

[ I_f = \fracV_thZ_th ] where ( V_th ) is the prefault voltage at the fault point (usually 1.0 pu), and ( Z_th ) is the Thevenin equivalent impedance seen from the fault point (resistance + reactance). In high-voltage systems, resistance is often neglected, giving: resistance is often neglected

( Z_Tx = 0.08 , \textpu ) (already on 10 MVA base).