1) Figure below shown the schematic diagram of 3-phase radial transmission system. The ratings and reactances of the various components are shown, along with the nominal transformer line voltages. A load of 50 MW at 0.8 p.f. lagging is taken from the 33-kV substation which is to be maintained at 30 kV. It is required to calculate the terminal voltage of the synchronous machine. The line and transformers may be represented by series reactances. The system is three-phase. 11 kV 132 kV 50MVA X = 10% Line j100 132 kV 33 kV 50 MVA X=12% 30kV 50MW 0-8p.f. lagging

1) Figure below shown the schematic diagram of 3-phase radial transmission system. The ratings and reactances of the various components are shown, along with the nominal transformer line voltages. A load of 50 MW at 0.8 p.f. lagging is taken from the 33-kV substation which is to be maintained at 30 kV. It is required to calculate the terminal voltage of the synchronous machine. The line and transformers may be represented by series reactances. The system is three-phase. 11 kV 132 kV 50MVA X = 10% Line j100 132 kV 33 kV 50 MVA X=12% 30kV 50MW 0-8p.f. lagging

Introductory Circuit Analysis (13th Edition)

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...

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No-load operation and short circuit tests were performed on three-phase, 50 Hz 480/220 delta / Y connected transformer. In these testsThe line voltage, line current and three-phase total power have been measured from the high voltage windings and the test results are below.pictures. 100 A DC current when 1.08 V DC voltage from non-transferable software is applied to the low voltage windingshas attracted.Find the single phase equivalent circuit parameters of this transformer.idle test:Voltage: 480V Power:114w current: 0.71Ashort circiut test:V: 10v P: 78w c: 18.3a
Find the elements of the equivalent circuit relative to the secondary of a single-phase transformer. The no-load voltages in the primary and secondarypement are 200 and 400 volts, respectively, with a trend of 50 Hz. The no-load current at 2, 50. Voltage 200 volts is equal to 0.7 amperes, and the cores are equal to 70 watts, 1.25 ohms, respectively, the resistance and reactance of the secondary 0.6, 7... Ohms, respectively. Draw the assigned circle Explaining the values of its elements.
2.2. The figure below shows a radial transmission system with a generator having a per-unit voltage of 1.3 at an angle of 9 degree p.u. The load demand is 47MW at a power factor of 0.96lagging. Use the nameplate values of Transformer 2 as base values and calculate the following: Correct answers to three decimal places : 25..Per unit impedance of transformer and it's angle 26.Per unit voltage of the line and its angle 27.Per unit impedance of the line and its angle. And Reactance of the transmission line when the load consumes full-load (Ω).
2. Given three identical ideal single-phase transformers with each rated at 100KVA and 7kV/3.5kV, they are connected as a three-phase transformer bank. The three-phase transformer has high voltage side connected in delta and the low voltage side is connected in wye. A three-phase 200KVA, wye connected load is connected at the low voltage side of the transformer. Calculate the following: a. Rated line-to-line voltage on each side b. Line current on each side of the transformer
1.a. Separate voltage-regulating units provide voltage-ratio control under load byA. causing different impedance drops in each phase.B. combining voltages from different phases.C. having series transformers in phase with the line-to-neutral voltage.D. exciting transformers having their primaries delta-connected. 1.b. A reactor is sometimes used with an autotransformer toA. limit short-circuit current.B. increase the full-load current.C. provide increased internal impedance.D. decrease the voltage ratio.
The Y/Y connected 3-phase step-up transformer has a rating of 1200 MVA, operating at 33 kV/340 kV and 60 Hz. Its impedance is characterized solely by a reactance of 11.5 percent. Its purpose is to increase the voltage from a generating station in order to supply power to a 340 kV transmission line. Answer the following questions: a) Draw and determine the equivalent circuit of this transformer, per phase, in per-unit. b) Using the per-unit method, determine the generator terminal voltage when the high-voltage (HV) side of the transformer supplies 800 MVA at a power factor of 0.90 with a lagging angle, and the voltage is 360 kV. Hint: Select the nominal voltage as a base voltage, and the nominal power rating as a base power.
A 36/240 V phase transformer, belonging to a phase measured from the no-load (idle) run and short-circuit test. values are given in the table below. High voltage by applying rated voltage to the low voltage winding (The winding ends were left unloaded and the results of the no-load test results were obtained. By applying nominal current to the high voltage windings, the low voltage windings were short-circuited, and the results of the short circuit test were obtained. In direct current test 1 V direct voltage is applied to the low voltage winding, and the transformer draws 500 A direct current. All equivalent Calculate the circuit elements as moved to the low voltage side. Idle run test: Voltage : 36V Power : 68W Current : 2,8A Short circuit test: Voltage : 15V Power : 325W Current : 42,2A
A 10 MVA three phase load is to be served by a three phase transformer at aline voltage of 13.8 kV. The supply side voltage(line-line) is 138 kV. Varioussingle phase transformers are available in the warehouse but all havewindings with voltage ratings under 100 kV and current ratings under 250 A.Is it possible to serve the load using only three single phase transformers? Ifso, specify the three phase connections and the low and high voltage ratingsof the single phase transformers.
The nameplate on a 25-MVA, 60-Hz single-phase transformer indicates that it has a voltage rating of 8.0-kV:78-kV. A short-circuit test from the high-voltage side (low-voltage winding shortcircuited) gives readings of 4.53 kV, 321 A, and 77.5 kW. An open-circuit test is conducted fromthe low-voltage side and the corresponding instrument readings are 8.0 kV, 39.6 A, and 86.2 kW. (a) Calculate the equivalent series impedance of the transformer as referred to the high-voltageterminals.(b) Calculate the equivalent series impedance of the transformer as referred to the low-voltageterminals.(c) Making appropriate approximations, draw a T equivalent circuit for the transformer.(d) Determine the efficiency of the transformer if it is supplying rated load (unity power factor)at rated voltage at its low-voltage terminal
The actual equivalent circuit parameters of a single-phase transformer operating at 220/110 volts are given as follows. R1=0.2 ohm, X1=0.3ohm, RFe=45 kohm, Xm=5 kohm, R2=0.025ohm, X2=0.075 ohm Using the L-equivalent circuit, a) reduce the secondary circuit parameters to the primary b) Since a reduced load of 44.72+j32 ohms is connected on the secondary side, calculate the primary current, the load current, and the total copper losses.
A synchronous generator is connected through a transformer and a transmission line to synchronous motor. The rated voltage and apparent power of the generator serve as the base quantities for this power system. On the system base, the per-unit sub transient reactance of the generator and the motor are 0.15 and 0.40 respectively, the series reactance of the transformer is 0.10, and the series reactance of the transmission line is 0.20. All resistances may be ignored. The generator is supplying rated apparent power and voltage at a power factor of 0.85 lagging when a three-phase synchronous fault occurs at the terminals of the motor. Find the per-unit sub transient current at the fault, in the generator, and in the motor.
A single-phase transformer rated 2400 – 277 V, 50 kVA, 60 Hz is tested with the following results: Open-Circuit Test: 277V, 4.51 A, 735 W. Short-Circuit Test: 51.4V, 19.6 A, 368 W. Determine the followings; 20. The series equivalent impedance referred to the HV side (ohms). 21. The series equivalent impedance in per-unit. 22. The magnetizing branch impedances referred to the LV side (ohms). 23. The magnetizing branch impedance in per-unit. 24. The full-load efficiency (%) when operating a load drawing rated power at rated voltage and unity power factor. 25. The voltage regulation (%) when operating a load drawing rated power at rated voltage and unity power factor.