Q1(a)In Figure Q1(a), four identical 10 MVA, 11 kV, 50 Hz three-phase generators, A, B,C and D, are connected to a 66-kV transmission system through a 6 MVA, 11/66 kVtransformer E. All reactances in per unit are based on their own components' ratings.GeneratorGeneratorGeneratorGeneratorAвD10 MVA10 MVA10 MVA10 MVAXG = 0.12 p.u.XG = 0.12 p.u.Xe = 0.12 p.u.XG = 0.12 p.u.Reactor R11 kV11 kVTransformerE6 MVAXT = 0.03 p.u.66 kVFFigure Q1(a)By using bases of 10 MVA and rated voltages in your calculation, determine:(i)the value of reactor R (in Henry) needed to limit the MVA fault level at F tobe 100 MVA, for a symmetrical fault at F.(ii)the value of short-circuit current (in A) at F due to conditions in (i).

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Q1 (а) In Figure Q1(a), four identical 10 MVA, 11 kV, 50 Hz three-phase generators, A, B, C and D, are connected to a 66-kV transmission system through a 6 MVA, 11/66 kV transformer E. All reactances in per unit are based on their own components' ratings. Generator A Generator в Generator Generator 10 MVA 10 MVA 10 MVA 10 MVA Xa = 0.12 p.u. Xe = 0.12 p.u. Xe = 0.12 p.u. XG = 0.12 p.u. Reactor R 11 kV 11 kV Transformer 6 MVA XT = 0.03 p.u. 66 kV F Figure Q1(a) By using bases of 10 MVA and rated voltages in your calculation, determine: (i) the value of reactor R (in Henry) needed to limit the MVA fault level at F to be 100 MVA, for a symmetrical fault at F. (ii) the value of short-circuit current (in A) at F due to conditions in (i).

Q1 (а) In Figure Q1(a), four identical 10 MVA, 11 kV, 50 Hz three-phase generators, A, B, C and D, are connected to a 66-kV transmission system through a 6 MVA, 11/66 kV transformer E. All reactances in per unit are based on their own components' ratings. Generator A Generator в Generator Generator 10 MVA 10 MVA 10 MVA 10 MVA Xa = 0.12 p.u. Xe = 0.12 p.u. Xe = 0.12 p.u. XG = 0.12 p.u. Reactor R 11 kV 11 kV Transformer 6 MVA XT = 0.03 p.u. 66 kV F Figure Q1(a) By using bases of 10 MVA and rated voltages in your calculation, determine: (i) the value of reactor R (in Henry) needed to limit the MVA fault level at F to be 100 MVA, for a symmetrical fault at F. (ii) the value of short-circuit current (in A) at F due to conditions in (i).

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 3.45P: Figure 3.39 shows a oneline diagram of a system in which the three-phase generator is rated 300 MVA,...

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Equipment ratings for the five-bus power system shown in Figure 7.15 are as follows: Generator G1:Â Â Â Â 50Â MVA,Â 12kV,Â X=0.2 per unit Generator G2: 100Â MVA, 15 kV, X=0.2 per unit Transformer T1: 50 MVA, 10 kV Y/138kVY,X=0.10 per unit Transformer T2: 100 MVA, 15 kV /138kVY,X=0.10 per unit Each 138-kV line: X1=40 A three-phase short circuit occurs at bus 5, where the prefault voltage is 15 kV. Prefault load current is neglected. (a) Draw the positive-sequence reactance diagram in unit on a 100-MVA, 15-kV base in the zone of generator G2. Determine (b) the ThĂ©venin equivalent at the fault, (c) the subtransient fault current in per unit and in kA rms, and (d) contributions to the fault from generator G2 and from transformer T2.
Determine the positive- and negative-sequence phase shifts for the three- phase transformers shown in Figure 3.36.
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.
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?
Figure 3.39 shows a oneline diagram of a system in which the three-phase generator is rated 300 MVA, 20 kV with a subtransient reactance of 0.2 per unit and with its neutral grounded through a 0.4- reactor. The transmission line is 64km long with a cries reactance of 0.5-/km. The three-phase transformer T1 is rated 350MVA.230/20kV with a leakage reactance of 0.1 per unit. Transformer T2 is composed of three single-phase transformers, each rated 100 MVA, 127/13.2kV with a leakage reactance of 0.1 per unit. Two 13.2kV motors M1 and M2 with a subtransient reactance of 0.2 per unit for each motor represent the load. M1 has a rated input of 200 MVA with its neutral grounded through a 0.4- current-limiting reactor, M2 has a rated input of 100 MVA with its neutral not connected to ground. Neglect phase shifts associated with the transformers. Choose the generator rating as base in the generator circuit and draw the positive-sequence reactance diagram showing all reactances in per unit.
How many transformers are needed to make an open-delta connection?
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.
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 a single-phase electric system shown in Figure 3.33. Transformers are rated as follows: XY15MVA,13.8/138kV, leakage reactance 10 YZ15MVA,138/69kV, leakage reactance 8 With the base in circuit Y chosen as 15MVA,138kV determine the per-unit impedance of the 500 resistive load in circuit Z, referred to circuits Z, Y, and X. Neglecting magnetizing currents, transformer resistances, and line impedances, draw the impedance diagram in per unit.
Consider the oneline diagram of a simple power system shown in Figure 9.20. System data in per-unit on a 100-MVA base are given as follows: The neutral of each generator is grounded through a current-limiting reactor of 0.08333 per unit on a 100-MVA base. All transformer neutrals are solidly grounded. The generators are operating no-load at their rated voltages and rated frequency with their ENIFs in phase. Determine the fault current for a balanced three-phase fault at bus 3 through a fault impedance ZF=0.1 per unit on a 100-MVA base. Neglect -Y phase shifts.
Three zones of a single-phase circuit are identified in the figure with a generator voltage specification of 240 V. The zones are connected by the transformers T1 and T2, whose ratings are shown below.Using base values of 30 kVA and 240 volts in zone 1, draw the pu circuit and determine the pu impedance and pu source voltage. Then calculate the load current in pu and in amperes.*Round the final answer to four decimal places, polar form, and label it with the correct units.
Three single-phase two-winding transformers, each rated 3 kVA, 220/110volts, 60 Hz, with a 0.10 per-unit leakage reactance, are connected as athree-phase extended D autotransformer bank, as shown in Figure 3.36 (c).The low-voltage D winding has a 110-volt rating. (a) Draw the positive sequencephasor diagram and show that the high-voltage winding has a479.5-volt rating. (b) A three-phase load connected to the low-voltageterminals absorbs 6 kW at 110 volts and at 0.8 power factor lagging. Drawthe per-unit impedance diagram and calculate the voltage and current atthe high-voltage terminals. Assume positive-sequence operation.