Equipment ratings for the five-bus power system shown in Figure 7.15 are as follows:

A three-phase short circuit occurs at bus 5, where the prefault voltage is $15kV$. Prefault load current is neglected.

(a) Draw the positive-sequence reactance diagram in per unit on a $100-MVA,15-kV$ base in the zone of generator G2. Determine

(b) the Thévenin equivalent at the fault,

(c) the subtransient fault current in per unit and in kA rms,

(d) contributions to the fault from generator G2 and from transformer T2.

Transcribed Image Text:

Generator Gl: Generator G2: Transformer Tl: Transformer T2: Each 138-kV line: 50 MVA, 12 kV, X" = 0.2 per unit 100 MVA, 15 kV, X"= 0.2 per unit 50 MVA, 10 kV Y/138 kV Y, X = 0.10 per unit 100 MVA, 15 kV A/138 kV Y, X = 0.10 per unit X = 40 2.