3. A three-phase Y-Y transformer is rated at 25 MVA, 13.8-kV:69-kV and has a single-phaseequivalent series impedance 62 + j388 mΩ referred to the low-voltage winding.a. A three-phase short circuit is applied to the low-voltage winding. Calculate the voltage applied to thehigh-voltage winding which will result in rated current into the short circuit.b. The short circuit is removed and a three-phase load is connected to the low-voltage winding. Withrated voltage applied to the high-voltage winding, the input power to the transformer is observed tobe 18 MW at 0.75 power-factor lagging. Calculate the line-line terminal voltage at the load. 3. A three-phase Y-Y transformer is rated at 25 MVA, 13.8-kV:69-kV and has a single-phaseequivalent series impedance 62 + j388 m2 referred to the low-voltage winding.a. A three-phase short circuit is applied to the low-voltage winding. Calculate the voltage applied to thehigh-voltage winding which will result in rated current into the short circuit.b. The short circuit is removed and a three-phase load is connected to the low-voltage winding. Withrated voltage applied to the high-voltage winding, the input power to the transformer is observed tobe 18 MW at 0.75 power-factor lagging. Calculate the line-line terminal voltage at the load.

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A three-phase Y-Y transformer is rated at 25 MVA, 13.8-kV:69-kV and has a single-phase equivalent series impedance 62 + j388 mΩ referred to the low-voltage winding. a. A three-phase short circuit is applied to the low-voltage winding. Calculate the voltage applied to the high-voltage winding which will result in rated current into the short circuit. b. The short circuit is removed and a three-phase load is connected to the low-voltage winding. With

A three-phase Y-Y transformer is rated at 25 MVA, 13.8-kV:69-kV and has a single-phase equivalent series impedance 62 + j388 mΩ referred to the low-voltage winding. a. A three-phase short circuit is applied to the low-voltage winding. Calculate the voltage applied to the high-voltage winding which will result in rated current into the short circuit. b. The short circuit is removed and a three-phase load is connected to the low-voltage winding. With

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 3.34P: Three single-phase, two-winding transformers, each rated 450MVA,20kV/288.7kV, with leakage reactance...

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For developing per-unit equivalent circuits of single-phase three-winding transformer, a common Sbase is selected for all three windings and voltage bases are selected in proportion to the rated voltage of the windings (a) True (b) False
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In 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) False
For 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) No
The ideal transformer windings are eliminated from the per-unit equivalent circuit of a transformer. (a) True (b) False
In 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) -
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.
An ideal transformer has no real or reactive power loss. (a) True (b) False
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For an ideal 2-winding transformer, the ampere-turns of the primary winding, N1I1 is equal to the ampere-turns of the secondary winding, N2I2 (a) True (b) False
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) -.
With the American Standard notation, in either a Y-or-Y transformer, positive- sequen quantities on the high-voltage side shall lead their corresponding quantities on the low-voltage side by 30. (a) True (b) False