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A fault occurs at point F of the system in the figure. Calculate the sub-transient current in phase c of machine 1, assuming that the currents before the fault are zero. Both machines have a nominal capacity of 1200 kVA, 480 V, with reactances X”=X2= 11% and X0 = 3.5%. The nominal capacity of each three-phase transformer is 1200 kVA, 480 V Δ/ 2400 V and with reactances X1=X2=X0= 6%. Transmission line reactances are X1=X2=22% and X0 = 35% on a 1200 kVA, 2400 V basis. Neutral grounding reactor reactances are 8% on a kVA and kV basis. of the machines.
a) Calculate the fault current if a ground fault occurs in phase a,
b) The fault current if it is a line-to-line fault
c) the voltage in phase b and c for the line-to-ground fault in phase a .
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