Given a conventional single-phase transformer is converted to a step-up autotransformer asshown in Figure 1.a) If three single phase autotransformers of this kind are connected in Y - Y connection, as tohandle 2000KVA from a 12.6kV distribution line to a 13.8kV distribution line, calculate theapparent power that must the windings of each autotransformer can handle.b) Compare the apparent power calculated in (b) with the per phase apparent power. Are theyequal? If not, where the rest of power goes? Justify your answer by showing the how the restof power being calculated.c) Now if one of the autotransformers was to reconnected as an conventional transformer,calculate its voltages, currents and apparent power ratings. VseV,N,N,(=N,e)Vc( =NJConventional transformerStep up autotransformerFigure 1 Conversion of a conventional transformer to a step-up autotransformerNote:1 = primary currentz = secondary currentV, = primary voltageV2 = secondary voltageVc = primary coil voltageVee = secondary coil voltageIc = primary coil currentIse = secondary coil currentNc = primary coil turnsNge = secondary coil turnsNp = primary total turnsNg = secondary total turns

Solution- a) Since 3 phase, 200 KVA so single phase or apparent power of each windings,…

iven a conventional single-phase transformer is converted to a step-up autotransformer as shown in Figure 1. a) If three single phase autotransformers of this kind are connected in Y Y connection, as to handle 2000k VA from a 12.6kV distribution line to a 13.8kV distribution line, calculate the apparent power that must the windings of each autotransformer can handle. b) Compare the apparent power calculated in (b) with the per phase apparent power. Are they equal? If not, where the rest of power goes? Justify your answer by showing the how the rest of power being calculated.

iven a conventional single-phase transformer is converted to a step-up autotransformer as shown in Figure 1. a) If three single phase autotransformers of this kind are connected in Y Y connection, as to handle 2000k VA from a 12.6kV distribution line to a 13.8kV distribution line, calculate the apparent power that must the windings of each autotransformer can handle. b) Compare the apparent power calculated in (b) with the per phase apparent power. Are they equal? If not, where the rest of power goes? Justify your answer by showing the how the rest of power being calculated.

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 3.58P: A single-phase two-winding transformer rated 90MVA,80/120kV is to be connected as an autotransformer...

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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.
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Three 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.
A single-phase two-winding transformer rated 90MVA,80/120kV is to be connected as an autotransformer rated 80/200kV. Assume that the transformer is ideal. (a) Draw a schematic diagram of the ideal transformer connected as an autotransformer. showing the voltages, currents, and dot notation for polarity. (b) Determine 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 the kA rating is transferred by magnetic induction?
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A single-phase 50-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down transformer at the load end of a 2400-volt feeder whose series impedance is (1.0+j2.0) ohm. The equivalent series impedance of the transformer is (1.0+j2.5) ohms referred to the high-voltage (primary) side. The transformer is delivering rated load at a 0.8 power factor lagging and at a rated secondary voltage. Neglecting the transformer exciting current, determine (a) the voltage at the transformer primary terminals, (b) the voltage at the sending end of the feeder, and (c) the real and reactive power delivered to the sending end of the feeder.
Consider a bank of this 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-, (b) -Y, (c) Y-Y, and (d) -.
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.
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