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• JunaidAhmad

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Figure 1 shows a single-line diagram of a five-bus power system. Input data are given in Tables 1, 2 and 3. As shown in table 1, bus 1, to which a generator is connected, is the swing bus. Bus 3, to which a generator and a load are connected, is a voltage controlled bus. Buses 2, 4 and 5 are load buses. Note that the loads at buses 2 and 3 are inductive since Q2 = -QL2 = -2.8 and –QL3 = -0.4 are negative.

(a) For each bus k, determine which of the variables Vk, δk, Pk and Qk are input data and which are unknowns. Also compute the elements of the second row of Ybus. The input data and unknowns are listed in Table 4. For bus 1, the swing bus P1 and Q1 are unknowns. For bus 3, a voltage-controlled bus, Q3 and δ3 are unknowns. For buses 2, 4 and 5 load buses V2, V4, V5 and δk2, δk4, δ5 are unknowns. (b) Double the impedance on the line from bus 2 to bus 5. Determine the new value for the second row of Ybus. (c) Determine the dimension of the Jacobian matrix (Table 5) for the power system as shown in Figure 1 as per data of Question 2 (a). Also calculate ΔP2(0) in Step 1 and J124(0) in step 2 of the first Newton-Raphson iteration. Assume zero initial phase angles and 1.0 per-unit initial voltage magnitudes (except V3 = 1.05)

Figure 1: Single-line diagram for Question 2