The one-line diagram of a power system is shown in the figure below. A single-line-to- ground (SLG) fault occurs at bus 2. Assume the fault impedance Zj=j0.08 pu. Calculate the fault current (in per unit). 2 M Line X, = X2 = 40 N 1 Xo = 1200 100 MVA 13.8 kV 100 MVA 100 MVA X, = 0.15 X2 = 0.17 X, = 0.05 per unit 138-kV Y/13.8-kV A X = 0.10 per unit 13.8-kVA/138-kVY 100 MVA X = 0.10 per unit 13.8 kV X, = 0.20 X2 = 0.21 0 10

Q2) The single-line diagram of a three-phase power system is shown in the figure below. The inductor connected to Generator 3 neutral has a reactance of 0.05 per unit using generator 3 ratings as base. Use a 1000-MVA, 765-kV base in the zone of line 1-2. Equipment ratings are given as follows: Synchronous generators: G1 1000 MVA 15 kV G2 1000 MVA 15 kV G3 500 MVA 13.8 kV G4 750 MVA 13.8 kV Transformers: T1 1000 MVA T2 1000 MVA T3 500 MVA T4 750 MVA Transmission lines: 1-2 765 kV 1-3 765 kV 2-3 765 kV 15 kV A/765 kV Y 15 kV A/765 kV Y 15 kV Y/765 kV Y 15 kV Y/765 kV Y X = X₂ = 0.18, Xo = 0.07 per unit X=X₂=0.20, Xo = 0.10 per unit X=X₂ = 0.15, Xo = 0.05 per unit X=0.30, X₂ = 0.40, Xo = 0.10 per unit X₁ = 50 2, Xo = 150 2 X₁ = 40 2, Xo = 100 2 X₁ = 40 2, Xo = 100 2 at Line 1-3 Line 1-2 2 X = 0.10 per unit X = 0.10 per unit X = 0.12 per unit X = 0.11 per unit Line 2-3 3 youtly

The 60 mile, 115 kV line GH (Figure P12.8) is operating with the voltages ateach end 30° out of phase when a three-phase fault occurs at 80% of the distance from bus G. This fault has 12 Ω arc resistance. The currents flowing tothe fault are as shown and are in per unit at 100 MVA, 115 kV.d. Determine if the zone 1 mho unit at H set for 90% of the line GH can operate for this fault. Assume that the angle of the mho characteristic is 75°.e. Describe how this three-phase fault can be cleared by the line distance relays.

j0.2 For the following power system the impedance matrix is given below. Initially all bus voltages are 1 pu. Then a three-phase fault occurs at bus (2). j0.25 j0.2 (3) (1) j0.1 : (a) What is the fault current? (2) j0.125 j0.1 (b) What are the post-fault bus voltages? 3. 0.0625 0.02083 0.02083' Zbus 0.02083 0.07044 0.02282 0.02083 0.02282 0.06091