A 50-kVA 13.8-kV/208-V (rms, line-line) ∆ − Y three-phase distribution transformer has a per unit resistance of 1 percent and a per-unit reactance of 0.07 pu. Neglect the excitation branch elements, and answer the following questions. (a) What is the transformer’s phase impedance referred to the high-voltage side? Calculate it in Ω. (b) Calculate this transformer’s voltage regulation using the calculated high-side impedance in Ω if it supplies a full load at 0.866 PF lagging. (c) Calculate this transformer’s voltage regulation under the same conditions, using the per-unit system. (d) Calculate this transformer’s efficiency in percent if it supplies a full load at 0.866 PF lagging.

A 50-kVA 13.8-kV/208-V (rms, line-line) ∆ − Y three-phase distribution transformer has a per unit resistance of 1 percent and a per-unit reactance of 0.07 pu. Neglect the excitation branch elements, and answer the following questions. (a) What is the transformer’s phase impedance referred to the high-voltage side? Calculate it in Ω. (b) Calculate this transformer’s voltage regulation using the calculated high-side impedance in Ω if it supplies a full load at 0.866 PF lagging. (c) Calculate this transformer’s voltage regulation under the same conditions, using the per-unit system. (d) Calculate this transformer’s efficiency in percent if it supplies a full load at 0.866 PF lagging.

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 3.4P: A single-phase 100-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down...

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PowerWorid Simulator case Problem 3_60 duplicates Example 3.13 except that a resistance term of 0.06 per unit has been added to the transformer and 0.05 per unit to the transmission line. Since the system is no longer lossless, a field showing the real power losses has also been added to the oneline. With the LTC tap fixed at 1.05, plot the real power losses as the phase shift angle is varied from 10 to +10 degrees. What value of phase shift minimizes the system losses?
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