Fault Current Calculation -

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

[ 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: fault current calculation

| Fault Type | Network Connection | |---|---| | SLG | ( Z_1, Z_2, Z_0 ) in series | | L-L | ( Z_1 ) and ( Z_2 ) in parallel (no ( Z_0 )) | | DLG | ( Z_1 ) in series with parallel combination of ( Z_2 ) and ( Z_0 ) | ( Z_Tx = 0

[ Z_util = \fracS_baseS_sc = \frac101000 = 0.01 , \textpu ] ( Z_Tx = 0.08

( Z_th = 0.01 + 0.08 = 0.09 , \textpu )

( S_base = 10 , \textMVA ), ( V_base, HV = 115 , \textkV ), ( V_base, LV = 13.8 , \textkV ).