A Fourbus system is shown in figure 1 1For the system shown

A Four-bus system is shown in figure 1.

1,For the system shown in Fig. 1, form the Z_bususing the building algorithm. Determine the voltages at all the buses when the load at bus 3 draws a current of j0.8 p.u.

2, From the solution of part 1, draw the Thevenin equivalent circuit at bus 3 ands use it to determine the current drawn by a capacitor of reactance -j7.5 p.u. connected between bus 3 and reference. Calculate the voltage changes and the new voltages at each of the buses due to the capacitor.

3, Modify the Z_bus in part 1, by adding a new bus connected to bus 3 through an impedance of j0.3 pu.

4, Modify the Z_bus determined in part 1, by adding a new line of an impedance j0.5 pu between buses 1 and 4.

5, Modify the Z_bus determined in part 1, to reflect removal of the line connected between buses 1 and 3

Solution

Computer application for power systems is one of the many technologies undergoing rapid evolution. In the operation of a power system, the most often-used simulation tools are Load flow, Short Circuit and Dynamics Programs. The first short circuit or fault problem was solved by a Gauss-Siedel load flow type in 1955. Then came the bus impedance matrix, which matured by axes discarding technique to solve large systems. For several decades, short circuit calculation was computed using the elements of the bus impedance matrix. Despite the variety of applications of Zbus, in power system analysis, like fault analysis, contingency analysis, detection of over loaded lines, etc., the use of Zbus matrix has been constrained principally to mainframe computers because of the computational burden and large memory requirement.
Conventional methods to form Zbus matrix i.e., Inversion of Ybus matrix and Building algorithm method have large computational burden. Therefore, a new Zbus matrix building algorithm, deriving from the concepts of the circuit analysis, traditional Zbus matrix building technique, is proposed in this dissertation work. The new method is systematic, effective and programmable. The proposed method is tested on different IEEE test systems (IEEE 14, 30, 39, 57, 118 and 300 bus systems). Moreover, detailed analysis and results of a detailed Zbus matrix formation of IEEE 39 bus system and IEEE 300 bus systems are provided. Results are obtained using MATLAB 7.1. It has been proved that the proposed method can be used for large systems