EEE40007
Power System Operation and Control
Test 1, Semester 2, 2023
Test 1 Questions
QUESTION 1 (15 MARKS)
Shown above is a 3-bus power system. The system parameters are given below, with all the impedance values in per unit of their respective power rating.
Generators 1 and 2: 100MVA, 20 kV, X1 = X2 = 0.20, X0 = 0.05
Transformers T1: 100 MVA, 20 ∆ / 345 Y kV, X = 0.05
Transformers T2: 100 MVA, 20 Y / 345 Y kV, X = 0.05
Transmission line: X1 = X2 = 0.10, X0 = 0.30
The system is unloaded with bus voltages 1.0 per unit.
1) Choose 100MVA as the power base and 345 kV as the voltage base in the transmission line. Find the positive, negative and zero sequence networks. Indicate clearly the per unit values of the impedances in the sequence networks. [3 Marks]
2) Find the sequence bus admittance matrices Ybus0 , Ybus1 and Ybus2, and the sequence bus impedance matrices Zbus0, Zbus1 and Zbus2 . [4 Marks]
3) For a bolted double-line-to-ground fault at bus 3, use the sequence bus impedance matrices obtained in 2) to find [8 Marks]
a) the phase currents Ia, Ib and Ic at bus 3 in actual value,
b) the respective contributions of generator 2 and generator 1 to the zero sequence component of the fault current in per unit value,
c) the phase voltages Va, Vb and Vc at bus 3 in per unit value, and
d) the phase voltages Va, Vb and Vc at bus 2 in per unit value.