Solved: A single-line diagram of a four-bus system is

Chapter , Problem 9.55

(choose chapter or problem)

A single-line diagram of a four-bus system is shown in Figure 9.27. Equipment ratings and per-unit reactances are given as follows. Machines 1 and 2: 100 MVA 20 kV X1 _ X2 _ 0:2 X0 _ 0:04 Xn _ 0:05 Transformers T1 and T2: 100 MVA 20D=345Y kV X1 _ X2 _ X0 _ 0:08 On a base of 100 MVA and 345 kV in the zone of the transmission line, the series reactances of the transmission line are X1 _ X2 _ 0:15 and X0 _ 0:5 per unit. (a) Draw each of the sequence networks and determine the bus impedance matrix for each of them. (b) Assume the system to be operating at nominal system voltage without prefault currents, when a bolted line-to-line fault occurs at bus 3. Compute the fault current, the line-to-line voltages at the faulted bus, and the line-to-line voltages at the terminals of machine 2. (c) Assume the system to be operating at nominal systemvoltage without prefault currents, when a bolted double-line-to-ground fault occurs at the terminals of machine 2. Compute the fault current and the line-to-line voltages at the faulted bus.