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# The one-line diagram of a three-bus power system is shown in Figure 4. All impedances are...

The one-line diagram of a three-bus power system is shown in Figure 4. All impedances are
expressed in per unit on a common MVA base. All resistances and shunt capacitances are
neglected. Information on each component in this system is given below:
• Each generator is represented by an emf
behind the sub-transient reactance of j0.045
and their neutrals are connected to the
ground.
• Line 1-2 has reactance of j0.88
• Line 2-3 has reactance of j0.65
• Line 1-3 has reactance of j0.4
• The generators are operating on no load at
their rated voltage (1.02 per unit) with their
emf in phase.
a) Construct the bus impedance matrix by adding one impedance element at a time and
using the matrix elimination technique, when needed.
b) Consider, a three-phase fault, which occur sequentially at bus 1, 2 and 3 through a fault
impedance of Zf=j0.20 per unit. Find the bus location at which fault current in per unit is
the most severe.
c) Determine the healthy bus voltages for the fault location at bus 3.
A second line is built between Bus 1 and Bus 2 with an impedance of j0.88.
d) Repeat Questions (a), (b) and (c) for the new power systems.
e) Compare the bus matrix in this case with the original bus matrix. What is the implication
of introducing the second transmission line between bus 1 and bus 2?
Figure 4

Figure 4

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