In the network calculation, there are two main parameter that need to solved. There are Ys and Z We could determine Zas by first finding You and then inverting it but this is not convenient for large scale system. Fortunately, formulation of Zeus using a direct buikdong algorithm is a straightforward process and we called this procedure as Zsus building algorthm. By using this algorithm, determine Zs for the network shown in Figure $4$ and aft impedances are in per unit.