Figure 1 shows a three-phase power system network comprises of synchronous generator, transformers, transmission lines and loads while Table 1 shows the ratings of the components. Using per unit analysis, 100 MVA base and 20 kV as the voltage base at the generator, answer the following questions: T2 TLine Load C Load A Load B Figure 1: A simple power system network. Table 1: The power system component ratings G 90 MVA, 20 kV, XG = 120% T1 80 MVA, 20/132 kV, XTI = 16% T2 80 MVA, 132/11 kV, XT2 = 10% TLine 132 kV, XLine = 18 2 Load A 7 MW +j3 Mvar Load B 30 MW+j 15 Mvar Load C 22 MVA, 0.89 power factor leading (a) Calculate the impedance per-unit values of all independent components based on given conditions.

Figure 1 shows a three-phase power system network comprises of synchronous generator, transformers, transmission lines and loads while Table 1 shows the ratings of the components. Using per unit analysis, 100 MVA base and 20 kV as the voltage base at the generator, answer the following questions: T2 TLine Load C Load A Load B Figure 1: A simple power system network. Table 1: The power system component ratings G 90 MVA, 20 kV, XG = 120% T1 80 MVA, 20/132 kV, XTI = 16% T2 80 MVA, 132/11 kV, XT2 = 10% TLine 132 kV, XLine = 18 2 Load A 7 MW +j3 Mvar Load B 30 MW+j 15 Mvar Load C 22 MVA, 0.89 power factor leading (a) Calculate the impedance per-unit values of all independent components based on given conditions.

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.25P: Consider a single-phase electric system shown in Figure 3.33. Transformers are rated as follows:...

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Consider the oneline diagram shown in Figure 3.40. The three-phase transformer bank is made up of three identical single-phase transformers, each specified by X1=0.24 (on the low-voltage side), negligible resistance and magnetizing current, and turns ratio =N2/N1=10. The transformer bank is delivering 100 MW at 0.8 p.f. lagging to a substation bus whose voltage is 230 kV. (a) Determine the primary current magnitude, primary voltage (line-to-line) magnitude, and the three-phase complex power supplied by the generator. Choose the line-to-neutral voltage at the bus, Va as the reference Account for the phase shift, and assume positive-sequence operation. (b) Find the phase shift between the primary and secondary voltages.
Consider three ideal single-phase transformers (with a voltage gain of ) put together as three-phase bank as shown in Figure 3.35. Assuming positive-sequence voltages for Va,Vb, and Vc find Va,Vb, and VC. in terms of Va,Vb, and Vc, respectively. (a) Would such relationships hold for the line voltages as well? (b) Looking into the current relationships, express IaIb and Ic in terms of IaIb and Ic respectively. (C) Let S and S be the per-phase complex power output and input. respectively. Find S in terms of S.
The per-unit equivalent circuit of two transformers Ta and Tb connected in parallel, with the same nominal voltage ratio and the same reactan of 0.1 per unit on the same base, is shown in Figure 3.43. Transformer Tb has a voltage-magnitude step-up toward the load of 1.05 times that of Ta (that is, the tap on the secondary winding of Tb is set to 1.05). The load is represented by 0.8+j0.6 per unit at a voltage V2=1.0/0 per unit. Determine the complex power in per unit transmitted to the load through each transformer, comment on how the transformers share the real and reactive powers.
Three single-phase two-winding transformers, each rated 3kVA,220/110volts,60Hz, with a 0.10 per-unit leakage reactance, are connected as a three-phase extended autotransformer bank, as shown in Figure 3.36(c). The low-voltage winding has a 110 volt rating. (a) Draw the positive-sequence phasor diagram and show that the high-voltage winding has a 479.5 volt rating. (b) A three-phase load connected to the low-voltage terminals absorbs 6 kW at 110 volts and at 0.8 power factor lagging. Draw the per-unit impedance diagram and calculate the voltage and current at the high-voltage terminals. Assume positive-sequence operation.
An AC three phase distribution system (given in Figure 2), which has end user with balanced three phase (10A) load, is given in the figure. The phase-neutral voltages of the transformers are given as V1=224V, V2=225V, V3=228V and V4=231V respectively. a) Calculate phase-neutral voltage of the bus-bar (B). b) Calculate currents of the transformers (I1, I2, I3 and I4) c) Calculate phase-neutral voltage of the point K while the output of TR3 and TR4 (xy) have been short circuited for a transient time (transformers are still operational) by the line fault.
The one-line diagram of a simple power system is shown in Figure below. The neutral of each generator is grounded through a current-limiting reactor of 0.25/3 per unit on a 100-MVA base. The system data expressed in per unit on a common 100-MVA base is tabulated below. The generators are running on no-load at their rated voltage and rated frequency with their emfs in phase. G Stark Item Base MVA Voltage Rating X' x² 20 kV 20 kV 20/220 kV 20/220 kV 100 0.05 0.15 0.15 0.10 0.10 220 kV 0.125 0.125 0.30 0.15 0.25 025 0.7125 0.15 100 100 0.15 0.05 0.10 0.10 0.10 100 0.10 100 100 Lu La 220 kV 0.15 220 kV 0.35 100 A balanced three-phase fault at bus 3 through a fault impedance Zf= jo.I per unit. The magnitude of the fault current in amperes in phase b for this fault is: Select one: A. 345.3 B. 820.1 C. 312500 3888888 产产
1. A single-phase power system as shown in Figure 1 consists of a 240 V, 60 Hz generator supplying a load, Zod = 8 + j6 Q through a transmission line of impedance, Zne = 0.08 + j0.14 Q. Answer the following questions: (1) transformer, T; and T2. Determine the voltage at the load and transmission line losses without the (ii) Determine the voltage at the load and transmission line losses with the transformer, T, and T2. T1 T2 1:10 10:1 IG Zaine Zioad source Figure 1
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Figure shows a generator connected to a metropolitan system (infinite bus) through highvoltage lines. The numbers on the figure indicate the reactances in p.u. Breakers adjacent to afault on both sides are arranged to clear simultaneously. Determine the critical clearing anglefor the generator for a 3-phase fault at the point P when the generator is delivering 1.0 p.u.power. Assume that the voltage behind transient reactance is 1.2 p.u. for the generator andthat the voltage at the infinite bus is 1.0 p.u.
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