A three-phase synchronous generator is connected to a step-up 3¢ transformer T1, which isconnected to a 60 km transmission line. At the far end of the line, a step-down transformerbank T2 is connected. The secondary of T2 supplies two synchronous motor loads M1 andM2. The ratings of the equipment are as follows:10 MVA,12 MVA, 13.8/138 kV,12 MVA,4 MVA,3 MVA,X = 30%,X = 10%,X = 9%,X = 25%,X = 30%,X = 0.3 2/kmGen:13.8 kV,wyedelta-wyewye-deltaT1:138/12 kV,12 kV,12 kV,138 kV,T2:M1:wyeM2:wye%3|T-line:(a) Draw the per-phase equivalent circuit of the system showing all reactances inand the base voltages used at various parts of the network. Choose the generator ratingsas bases in the generator circuit.perunit(b) For a three-phase fault on the low-voltage terminals of transformer T2, calculate thesteady-state short-circuit current magnitude in amperes supplied by the generator as-suming that all internal voltages are 1.020° pu. Ignore the motor contributions to thefault current for now.

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A three-phase synchronous generator is connected to a step-up 3¢ transformer T1, which is connected to a 60 km transmission line. At the far end of the line, a step-down transformer bank T2 is connected. The secondary of T2 supplies two synchronous motor loads M1 and M2. The ratings of the equipment are as follows: 10 MVA, 13.8 kV, 12 MVA, 13.8/138 kV, 138/12 kV, 12 kV, 12 kV, 138 kV, X = 30%, X = 10%, X = 9%, X = 25%, X = 30%, X = 0.3 N/km Gen: wye T1: T2: M1: 12 MVA, 4 MVA, 3 MVA, delta-wye wye-delta wye M2: wye T-line: %3| (a) Draw the per-phase equivalent circuit of the system showing all reactances in and the base voltages used at various parts of the network. Choose the generator ratings as bases in the generator circuit. per unit (b) For a three-phase fault on the low-voltage terminals of transformer T2, calculate the steady-state short-circuit current magnitude in amperes supplied by the generator as- suming that all internal voltages are 1.0° pu. Ignore the motor contributions to the fault current for now.

A three-phase synchronous generator is connected to a step-up 3¢ transformer T1, which is connected to a 60 km transmission line. At the far end of the line, a step-down transformer bank T2 is connected. The secondary of T2 supplies two synchronous motor loads M1 and M2. The ratings of the equipment are as follows: 10 MVA, 13.8 kV, 12 MVA, 13.8/138 kV, 138/12 kV, 12 kV, 12 kV, 138 kV, X = 30%, X = 10%, X = 9%, X = 25%, X = 30%, X = 0.3 N/km Gen: wye T1: T2: M1: 12 MVA, 4 MVA, 3 MVA, delta-wye wye-delta wye M2: wye T-line: %3| (a) Draw the per-phase equivalent circuit of the system showing all reactances in and the base voltages used at various parts of the network. Choose the generator ratings as bases in the generator circuit. per unit (b) For a three-phase fault on the low-voltage terminals of transformer T2, calculate the steady-state short-circuit current magnitude in amperes supplied by the generator as- suming that all internal voltages are 1.0° pu. Ignore the motor contributions to the fault current for now.

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 3.48P: With the same transformer banks as in Problem 3.47, Figure 3.41 shows the oneline diagram of a...

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Consider the single-line diagram of the power system shown in Figure 3.38. Equipment ratings are Generator 1: 1000MVA,18kV,X=0.2perunit Generator 2: 1000MVA,18kV,X=0.2p.u. Synchronous motor 3: 1500MVA,20kV,X=0.2p.u. Three-phase -Y transformers T1,T2,T3,T4,: 1000MVA,500kV,Y/20kV,X=0.1p.u. Three-phase YY transformer T5: 1500MVA,500kV,Y/20kVY,X=0.1p.u. Neglecting resistance, transformer phase shift, and magnetizing reactance, draw the equivalent reactance diagram. Use a base of 100 MA and 500 kV for the 50-ohm line. Determine the per-unit reactances.
Consider the single-Line diagram of a power system shown in Figure 3.42 with equipment ratings given: Generator G1: 50MVA,13.2kV,x=0.15p.u. Generator G2: 20MVA,13.8kV,x=0.15p.u. Three-phase -Y transformer T1: 80MVA,13.2/165YkV,X=0.1p.u. Three-phase Y- transformer T2: 40MVA,165Y/13.8kV,X=0.1p.u. Load: 40MVA,0.8PFlagging,operatingat150kV Choose a base of 100 MVA for the system and 132-kV base in the transmission-line circuit. Let the load be modeled as a parallel combination of resistance and inductance. Neglect transformer phase shifts. Draw a per-phase equivalent circuit of the system showing all impedances in per unit.
With the same transformer banks as in Problem 3.47, Figure 3.41 shows the oneline diagram of a generator, a step-up transformer bank, a transmission line, a stepown transformer bank, and an impedan load. The generator terminal voltage is 15 kV (line-to-line). (a) Draw the per-phase equivalent circuit, aounting for phase shifts for positive-sequence operation. (b) By choosing the line-to-neutral generator terminal voltage as the reference, determine the magnitudes of the generator current, transmiss ion-line current, load current, and line-to-line load voltage. Also, find the three-phase complex power delivered to the load.
The motors M1andM2 of Problem 3.45 have inputs of 120 and 60 MW, respectively, at 13.2 kV, and both operate at unity power factor. Determine the generator terminal voltage and voltage regulation of the line. Neglect transformer phase shifts.
Three single-phase two-winding transformers, each rated 25MVA,34.5/13.8kV, are connected to form a three-phase bank. Balanced positive-suence voltages are applied to the high-voltage terminals, and a balanced, resistive Y load connected to the low-voltage terminals absorbs 75 MW at 13.8 kV. If one of the single-phase transformers is removed (resulting in an open connection) and the balanced load is simultaneously reduced to 43.3 MW (57.7 of the original value), determine (a) the load voltages Va,Vb, and Vc; (b) load currents Ia,Ib, and Ic; and (c) the MVA supplied by each of the remaining two transformers. Are balanced voltages still applied to the load? Is the open transformer overloaded?
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.
An infinite bus, which is a constant voltage source, is connected to the primary of the three-winding transformer of Problem 3.53. A 7.5-MVA,13.2-kV synchronous motor with a sub transient reactance of 0.2 per unit is connected to the transformer secondary. A5-MW,2.3-kV three-phase resistive load is connected to the tertiary Choosing a base of 66 kV and 15 MVA in the primary, draw the impedance diagram of the system showing per-unit impedances. Neglect transformer exciting current, phase shifts, and all resistances except the resistive load.
Determine the positive- and negative-sequence phase shifts for the three- phase transformers shown in Figure 3.36.
Reconsider Problem 3.64 with the change that now Tb includes both a transformer of the same turns ratio as Ta and a regulating transformer with a 4 phase shift. On the base of Ta, the impedance of the two comp onents of Tb is jO.1 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 pors.
For the power system in Problem 3.41, the synchronous motor absorbs 1500 MW at 0.8 power factor leading with the bus 3 voltage at 18 kV. Determine the bus I and bus 2 voltages in kV Assume that generators I and 2 deliver equal real powers and equal reactive powers. Also assume a balanced three-phase system with positive-sequence sources.
How many transformers are needed to make an open-delta connection?
The ratings of a three-phase three-winding transformer are Primary(1): Y connected 66kV,15MVA Secondary (2): Y connected, 13.2kV,10MVA Tertiary (3): A connected, 2.3kV,5MVA Neglecting winding resistances and exciting current, the per-unit leakage reactances are X12=0.08 on a 15-MVA,66-kV base X13=0.10 on a 15-MVA,66-kV base X23=0.09 on a 10-MVA,13.2-kV base (a) Determine the per-unit reactances X1,X2,X3 of the equivalent circuit on a 15-MVA,66-kV base at the primary terminals. (b) Purely resistive loads of 7.5 MW at 13.2 kV and 5 MW at 2.3kV are connected to the secondary and tertiary sides of the transformer, respectively. Draw the per- unit impedance diagram, showing the per-unit impedances on a 15-MVA,66-kV base at the primary terminals.