(Solved): Q1. The single-line diagram of an unloaded power system is shown below. The lengths of the transmis ...

Expert Answer

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To analyze the transient current and voltages during a double-line-to-ground fault, we need to determine the fault current and calculate the voltages in the unfaulted phases.


Let's start by converting the given ratings and impedances to the base of 100 MVA and 154 kV.
Given data:
Base power (Sbase) = 100 MVA
Base voltage (Vbase) = 154 kV
Generator G1:
Rated power (SG1) = 200 MVA
Rated voltage (VG1) = 380 kV
Generator G2:
Rated power (SG2) = 200 MVA
Rated voltage (VG2) = 380 kV
Transformer T1:
Rated power (ST1) = 150 MVA
Primary voltage (VT1_prim) = 380 kV
Secondary voltage (VT1_sec) = 160 kV
Transformer T2, T3:
Rated power (ST2) = 180 MVA
Primary voltage (VT2_prim) = 154 kV
Secondary voltage (VT2_sec) = 10.8 kV
Transmission Line 1:
Length (L1) = r1 = 150 km
Impedance (Z1) = r1 + jx1 = 0.06 ohm/km + j0.36 ohm/km
Transmission Line 2:
Length (L2) = r2 = 100 km
Impedance (Z2) = r2 + jx2 = 0.06 ohm/km + j0.15 ohm/km
Transmission Line 3:
Length (L3) = r3 = 100 km
Impedance (Z3) = r3 + jx3 = 0.06 ohm/km + j0.15 ohm/km