2 3 T j500 j500 ΔΥ YA j502 2 Figure 2. Power System Network for Problem 2
Equipment ratings for the four-bus power system shown in Figure 2 are as follows:
Generator 1: 500 MVA, 13.8 kV, X" = 0.20 pu
Generator 2: 750 MVA, 18 kV. X" = 0.18 pu
Generator 3: 1000 MVA, 20 kV. X" = 0.17 pu
Transformer Tl: 500 MVA, 13.8/500 kV, X = 0.12 pU
Transformer T2: 750 MVA, 18/500 kV. X = 0.10 pu
Transformer T3: 1000 MVA. 20/500 kV. X = 0.10 pU
A three-phase short circuit occurs at bus 1, where the prefault voltage is 525 kV. Prefault current is neglected. Use 1000 MVA, 20 kV base in the zone of generator 3. By
Thevenin's and Superposition approach, determine the following:
a) subtransient fault current in amperes
b) contributions to the fault current from the generators in amperes
c) voltage at bus 2 during fault in kV
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