In the above system, the three-phase fault MVA at bus 3 is

82.55 MVA
85.11 MVA
170.91 MVA
181.82 MVA

Correct answer: 181.82 MVA

Solution

For a balanced three-phase fault, only the positive-sequence network is used. The equivalent reactance seen from bus 3 is obtained from the per-unit network, and the fault level is then $S_{fault}=S_{base}/X_{th}$. This gives 181.82 MVA.

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