1) Explain the advantages of using per-unit in power system 2) Explain how, it was useful in Question1 and Question 2 Question 1In the system shown below, the generator is ideal (Xç = 0) and the magnitude ofthe load bus voltage, V. is to be held at 11 kV. Working on a system base of 25MVA and a base voltage of 10 kV at the load side:a) Draw the single-phase equivalent pu reactance diagram.b) Calculate the current I load in per unitc) Calculate the current I generator in Ad) Calculate the Power in VA generated, consumed and lostTransformer 120 MVA15KV: 60 kVX= 5%Transformer 220 MVA50 kV: 11 kVX = 6%LineX= 200LoadS= 12 MVApf = 0.85 lagVT1VT2VL Question 2.Given the single line diagram of a three phase balanced system.1) Find the per-unit equivalent diagram, using Sbase=25MVA and Vbase Gen=13.2KV.2) Find the voltage at the generator end in KV if the voltage at the load terminalis 12kV full load and pf of 0.9.GENERATORTRANSFORMERTRANSPORMERмотOR15,000 KVA13.0 kV3EX" = 15 percentLINEX = 65 0мотоя13.8kV10,000 kVA25,000 kVA25,000 kVA25,000 kVA 3-phase13.0 kV13.2/69 kV13.2/69 kVX" = 15 percentX" = 15 percentXL = 15 percentXL = 15 percent

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1) Explain the advantages of using per-unit in power system

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 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.
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.
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.
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

A synchronous generator is rated 645 MVA, 24 kV, 0.9 pf lagging. It has a synchronous reactance 1.2 . The generator is feeding full load at 0.9 pf lagging at rated voltage. Calculate: (a) Excitation emf (E,) and power angle & (b) Reictive power drawn by the load Carry out calculations in pu form and convert the result to actual values.
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.
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
6. A 3 phase fault occurs at point F as shown in figure. Determine the critical clearing anglefor the system. The generator is delivering 1.0 p.u power under prefault conditio
There is a three-phase system such that the phase current in the generator, lines and charging phase is the same. The phase voltage in the generator must be 1000 [V] with clockwise sequence. The connected load must be such that the phase current in each load is 10 [A] and its power factor is 0.97 “lagging”. a) Determine phase currents in the generator, lines and phase in the load
b) Two synchronous generators, G2 and G2, are connected parallelly supplying a load. Generator G1 has a no-load frequency of 50.5 Hz and a slope of 300 MW/Hz. Generator G2 has a no-load frequency of 50.2 Hz and a slope of 500 MW/Hz. The load consumes 250 MW real power. (1) At what frequency does this system operate, and how much power is supplied by each of the two generators? (ii) An additional 100 MW load is added to this power system. What is the new system frequency, and how much power do G1 and G2 supply? (iii) The governor set point of G2 is changed to control system frequency back to 50 Hz. Determine the G2 governor set point.
A 3-phase star connected, 1500 kVA, 13 kV alternator has an armature resistance of 0.9 ohm and a synchronous reactance of 8.0 ohms. When carrying rated load voltage, calculate the generated voltage per phase at loads of I.) Unity P.F. ii.) 0.8 lagging P.F. iii.) 0.8 leading P.F. iv.) calculate the voltage regulation for each load and determine best regulation.
L-type equivalent circuit and parameters for a continuous sinusoidal phase of a 5.5 kW, 1450 rpm, line voltage 220 V and frequency 50 Hz star-connected 3-phase ASM, ignoring core (iron) losses given as follows: R1=0.21 Ohm, R2=0.18 Ohm, X1=X2=0.66 Ohm and Xm=9.9 Ohm How many times the rated current will the inrush current be when the ASM is started directly?