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Q2:The synchronous generator in Figure is operating at rated MVA, 0.95 p.f. lagging and at 5% above rated voltage when a bolted three-phase short circuit occurs at bus 2. Calculate the per-unit values of (a) sub transient fault current; (b) sub transient generator and motor currents, neglecting prefault current; (c) subtransient generator and motor currents including prefault current using subtransent internal voltages of the machine, and (d) find the rupturing capacity of circuit breakers at bus 1 and bus 2. [25] Generator G: 100 MVA, 13.8 kV, X" = 0.15 Transformer T1: 100 MVA, 13.8 kV ? / 138 kV Y, X = 0.10 Line: Xline = 20 ? Transformer T2: 100 MVA, 138 kV Y / 13.8 kV ?, X = 0.10 Motor M: 100 MVA, 13.8 kV, X" = 0.20

          Q2:The synchronous generator in Figure is operating at rated MVA, 0.95 p.f. lagging and at 5% above rated voltage when a bolted three-phase short circuit occurs at bus 2. Calculate the per-unit values of (a) sub transient fault current; (b) sub transient generator and motor currents, neglecting prefault current; (c) subtransient generator and motor currents including prefault current using subtransent internal voltages of the machine, and (d) find the rupturing capacity of circuit breakers at bus 1 and bus 2. [25]

Generator G: 100 MVA, 13.8 kV, X" = 0.15
Transformer T1: 100 MVA, 13.8 kV ? / 138 kV Y, X = 0.10
Line: Xline = 20 ?
Transformer T2: 100 MVA, 138 kV Y / 13.8 kV ?, X = 0.10
Motor M: 100 MVA, 13.8 kV, X" = 0.20

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Q2:The synchronous generator in Figure is operating at rated MVA, 0.95 p.f. lagging and at 5% above rated voltage when a bolted three-phase short circuit occurs at bus 2. Calculate the per-unit values of (a) sub transient fault current; (b) sub transient generator and motor currents, neglecting prefault current; (c) subtransient generator and motor currents including prefault current using subtransent internal voltages of the machine, and (d) find the rupturing capacity of circuit breakers at bus 1 and bus 2. [25]

Generator G: 100 MVA, 13.8 kV, X" = 0.15
Transformer T1: 100 MVA, 13.8 kV ? / 138 kV Y, X = 0.10
Line: Xline = 20 ?
Transformer T2: 100 MVA, 138 kV Y / 13.8 kV ?, X = 0.10
Motor M: 100 MVA, 13.8 kV, X" = 0.20

Added by Lorena N.

University Physics with Modern Physics

Hugh D. Young 14th Edition

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Solved by Expert Madhur L

07/24/2023

Step 1

The per-unit impedance is given by: Z = V^2 / S where Z is the per-unit impedance, V is the rated voltage, and S is the rated MVA. Given that the generator is operating at 5% above rated voltage, the voltage is: V = 1.05 * rated voltage Substituting the given Show more…

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The synchronous generator in Figure is operating at rated MVA, 0.95 p.f. lagging and 5% above rated voltage when a bolted three-phase short circuit occurs at bus 2. Calculate the per-unit values of (a) subtransient fault current; (b) subtransient generator and motor currents, neglecting prefault current; (c) subtransient generator and motor currents including prefault current using subtransient internal voltages of the machine; and (d) find the rupturing capacity of circuit breakers at bus 1 and bus 2.

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