MindTap Engineering, 1 term (6 months) Printed Access Card for Glover/Overbye/Sarma's Power System Analysis and Design, 6th
6th Edition
ISBN: 9781305636323
Author: Glover, J. Duncan, Overbye, Thomas, Sarma, Mulukutla S.
Publisher: Cengage Learning
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Textbook Question
Chapter 3, Problem 3.35P
Consider a bank of this single-phase two-winding transformers whose high-voltage terminals are connected to a three-phase,
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Three transformers, e ach rated 25 MVA, 38. 1 /3.81 kV, are connected Star – Delta
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Consider a bank of three single-phase two-winding transformers whose high-voltage terminals are connected to a three-phase, 13.8-kV feeder. The low-voltage terminals are connected to a three-phase substation load rated 2.0 MVA and 2.5 kV. Determine the required voltage, current, and MVA ratings of both windings of each transformer, when the high-voltage/low-voltage windings are connected (a) Y–D, (b) D–Y, (c) Y–Y, and (d) D–D.
Two 11,000/2,200-V, 1-phase transformers are connected in parallel to supply a total load of 200 at 0.8 p.f. lagging at 2,200 V. One transformer has an equivalent resistance of 0.4 ohms and equivalent reactance of 0.8 ohms referred to the low-voltage side. The other has equivalent resistance of 0.1 ohms and a reactance of 0.3 ohms. Determine the current and power supplied by each transformer.
Chapter 3 Solutions
MindTap Engineering, 1 term (6 months) Printed Access Card for Glover/Overbye/Sarma's Power System Analysis and Design, 6th
Ch. 3 - The Ohms law for the magnetic circuit states that...Ch. 3 - For an ideal transformer, the efficiency is (a) 0...Ch. 3 - For an ideal 2-winding transformer, the...Ch. 3 - An ideal transformer has no real or reactive power...Ch. 3 - For an ideal 2-winding transformer, an impedance...Ch. 3 - Consider Figure 3.4. For an ideal phase-shifting...Ch. 3 - Consider Figure 3.5. Match the following, those on...Ch. 3 - The units of admittance, conductance, and...Ch. 3 - Match the following: (i) Hysteresis loss (a) Can...Ch. 3 - For large power transformers rated more than 500...
Ch. 3 - For a short-circuit test on a 2-winding...Ch. 3 - The per-unit quantity is always dimensionless. (a)...Ch. 3 - Consider the adopted per-unit system for the...Ch. 3 - The ideal transformer windings are eliminated from...Ch. 3 - To convert a per-unit impedance from old to new...Ch. 3 - In developing per-unit circuits of systems such as...Ch. 3 - Prob. 3.17MCQCh. 3 - Prob. 3.18MCQCh. 3 - With the American Standard notation, in either a...Ch. 3 - Prob. 3.20MCQCh. 3 - In order to avoid difficulties with third-harmonic...Ch. 3 - Does an open connection permit balanced...Ch. 3 - Does an open- operation, the kVA rating compared...Ch. 3 - It is stated that (i) balanced three-phase...Ch. 3 - In developing per-unit equivalent circuits for...Ch. 3 - In per-unit equivalent circuits of practical...Ch. 3 - Prob. 3.27MCQCh. 3 - Prob. 3.28MCQCh. 3 - For developing per-unit equivalent circuits of...Ch. 3 - Prob. 3.30MCQCh. 3 - Prob. 3.31MCQCh. 3 - Prob. 3.32MCQCh. 3 - The direct electrical connection of the windings...Ch. 3 - Consider Figure 3.25 of the text for a transformer...Ch. 3 - (a) An ideal single-phase two-winding transformer...Ch. 3 - An ideal transformer with N1=1000andN2=250 is...Ch. 3 - Consider an ideal transformer with...Ch. 3 - A single-phase 100-kVA,2400/240-volt,60-Hz...Ch. 3 - Prob. 3.5PCh. 3 - Prob. 3.6PCh. 3 - Consider a source of voltage v(t)=102sin(2t)V,...Ch. 3 - Prob. 3.8PCh. 3 - Prob. 3.9PCh. 3 - A single-phase step-down transformer is rated...Ch. 3 - For the transformer in Problem 3.10. The...Ch. 3 - Prob. 3.12PCh. 3 - A single-phase 50-kVA,2400/240-volt,60-Hz...Ch. 3 - A single-phase 50-kVA,2400/240-volt,60-Hz...Ch. 3 - Rework Problem 3.14 if the transformer is...Ch. 3 - A single-phase, 50-kVA,2400/240-V,60-Hz...Ch. 3 - The transformer of Problem 3.16 is supplying a...Ch. 3 - Using the transformer ratings as base quantities,...Ch. 3 - Using the transformer ratings as base quantities....Ch. 3 - Using base values of 20 kVA and 115 volts in zone...Ch. 3 - Prob. 3.21PCh. 3 - A balanced Y-connected voltage source with...Ch. 3 - Figure 3.32 shows the oneline diagram of a...Ch. 3 - For Problem 3.18, the motor operates at full load,...Ch. 3 - Consider a single-phase electric system shown in...Ch. 3 - A bank of three single-phase transformers, each...Ch. 3 - A three-phase transformer is rated...Ch. 3 - For the system shown in Figure 3.34. draw an...Ch. 3 - Consider three ideal single-phase transformers...Ch. 3 - Reconsider Problem 3.29. If Va,VbandVc are a...Ch. 3 - Prob. 3.31PCh. 3 - Determine the positive- and negative-sequence...Ch. 3 - Consider the three single-phase two-winding...Ch. 3 - Three single-phase, two-winding transformers, each...Ch. 3 - Consider a bank of this single-phase two-winding...Ch. 3 - Three single-phase two-winding transformers, each...Ch. 3 - Three single-phase two-winding transformers, each...Ch. 3 - Consider a three-phase generator rated...Ch. 3 - The leakage reactance of a three-phase,...Ch. 3 - Prob. 3.40PCh. 3 - Consider the single-line diagram of the power...Ch. 3 - For the power system in Problem 3.41, the...Ch. 3 - Three single-phase transformers, each rated...Ch. 3 - A 130-MVA,13.2-kV three-phase generator, which has...Ch. 3 - Figure 3.39 shows a oneline diagram of a system in...Ch. 3 - The motors M1andM2 of Problem 3.45 have inputs of...Ch. 3 - Consider the oneline diagram shown in Figure 3.40....Ch. 3 - With the same transformer banks as in Problem...Ch. 3 - Consider the single-Line diagram of a power system...Ch. 3 - A single-phase three-winding transformer has the...Ch. 3 - The ratings of a three-phase three-winding...Ch. 3 - Prob. 3.52PCh. 3 - The ratings of a three-phase, three-winding...Ch. 3 - An infinite bus, which is a constant voltage...Ch. 3 - A single-phase l0-kVA,2300/230-volt,60-Hz...Ch. 3 - Three single-phase two-winding transformers, each...Ch. 3 - A two-winding single-phase transformer rated...Ch. 3 - A single-phase two-winding transformer rated...Ch. 3 - Prob. 3.59PCh. 3 - PowerWorid Simulator case Problem 3_60 duplicates...Ch. 3 - Rework Example 3.12 for a+10 tap, providing a 10...Ch. 3 - A 23/230-kV step-up transformer feeds a...Ch. 3 - The per-unit equivalent circuit of two...Ch. 3 - Reconsider Problem 3.64 with the change that now...Ch. 3 - What are the advantages of correctly specifying a...Ch. 3 - Why is it important to reduce the moisture within...Ch. 3 - What should be the focus of transformer preventive...
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- Three single-phase, two-winding transformers, each rated 450MVA,20kV/288.7kV, with leakage reactance Xeq=0.10perunit, are connected to form a three-phase bank. The high-voltage windings are connected in Y with a solidly grounded neutral. Draw the per-unit equivalent circuit if the low-voltage windings are connected (a) in with American standard phase shift or (b) in Y with an open neutral. Use the transformer ratings as base quantities. Winding resistances and exciting current are neglected.arrow_forwardThree single-phase two-winding transformers, each rated 25MVA,54.2/5.42kV, are connected to form a three-phase Y- bank with a balanced Y-connected resistive load of 0.6 per phase on the low-voltage side. By choosing a base of 75 MVA (three phase) and 94 kV (line-to-line) for the high-voltage side of the transformer bank, specify the base quantities for the low-voltage side. Determine the per-unit resistance of the load on the base for the low-voltage side. Then determine the load resistance RL in ohms referred to the high-voltage side and the per-unit value of this load resistance on the chosen base.arrow_forwardIn per-unit equivalent circuits of practical three-phase transformers, under balanced thr-phase operation, in which of the following connect ions would a phase-shifting transformer come up? (a) Y-Y (b) Y- (c) -arrow_forward
- A bank of three single-phase transformers, each rated 30MVA,38.1/3.81kV, are connected in Y- with a balanced load of three 1, Y-connected resistors. Choosing a base of 90MVA,66kV for the high-voltage side of the three-phase transformer. spify the base for the low-voltage side. Compute the per-unit resistance of the load on the base for the low-voltage side. Also, determine the load resistance in ohms referred to the high-voltage side and the per-unit value on the chosen base.arrow_forwardIn developing per-unit circuits of systems such as the one shown in Figure 3.10. when moving across a transformer, the voltage base is changed in proportion to the transformer voltage ratings. (a) True (b) Falsearrow_forwardThe ideal transformer windings are eliminated from the per-unit equivalent circuit of a transformer. (a) True (b) Falsearrow_forward
- 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.arrow_forwardFor a short-circuit test on a 2-winding transformer, with one winding shorted, can you apply the rated voltage on the other winding? (a) Yes (b) Noarrow_forwardA single-phase, 50-kVA,2400/240-V,60-Hz distribution transformer has the following parameters: Resistance of the 2400-V winding: R1=0.75 Resistance of the 240-V winding: R2=0.0075 Leakage reactance of the 2400-V winding: X1=1.0 Leakage reactance of the 240-V winding: X2=0.01 Exciting admittance on the 240-V side =0.003j0.02S (a) Draw the equivalent circuit referred to the high-voltage side of the transformer. (b) Draw the equivalent circuit referred to the low-voltage side of the transformer. Show the numerical values of impedances on the equivalent circuits.arrow_forward
- 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.arrow_forwardConsider 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.arrow_forwardA single-phase l0-kVA,2300/230-volt,60-Hz two-winding distribution transformer is connected as an autotransformer to step up the voltage from 2300 to 2530 volts (a) Draw a schematic diagram of this arrangement, showing all voltages and currents when delivering full load at rated voltage. (b) Find the permissible kVA rating of the autotransformer if the winding currents and voltages are not to exceed the rated values as a two-winding transformer. How much of this kVA rating is transformed by magnetic induction? (C) The following data are obtained from tests carried out on the transformer when it is connected as a two-winding transformer: Open-circuit test with the low-voltage terminals excited: Applied voltage =230V, input current =0.45A, input power =70W. Short-circuit test with the high-voltage terminals excited: Applied voltage =120, input current =4.5A, input power =240W. Based on the data, compute the efficiency of the autotransformer corresponding to full load, rated voltage, and 0.8 power factor lagging. Comment on why the efficiency is higher as an autotransformer than as a two-winding transformer.arrow_forward
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