8. A three-phase 50 Hz, 200 MVA, 220/66 kV transformer has a clock number of Yd11. The transformer winding resistances are 2.0 A and 0.12 0, and the leakage reactances are 10 A and 0.6 N for the high voltage side and low voltage side respectively. (a) Sketch the phase voltage phasor diagrams for the high-voltage side and low-voltage side of the transformer and from the phasor diagrams obtain its connection diagram. (b) Calculate the per-unit impedance of the transformer referred to the high-voltage side. (c) Calculate the full-load copper losses of this transformer. (d) Calculate the efficiency of the transformer when it supplies 90% of full-load at a power factor of 0.85 lagging, if the core losses are equal to 3 MW.

8. A three-phase 50 Hz, 200 MVA, 220/66 kV transformer has a clock number of Yd11. The transformer winding resistances are 2.0 A and 0.12 0, and the leakage reactances are 10 A and 0.6 N for the high voltage side and low voltage side respectively. (a) Sketch the phase voltage phasor diagrams for the high-voltage side and low-voltage side of the transformer and from the phasor diagrams obtain its connection diagram. (b) Calculate the per-unit impedance of the transformer referred to the high-voltage side. (c) Calculate the full-load copper losses of this transformer. (d) Calculate the efficiency of the transformer when it supplies 90% of full-load at a power factor of 0.85 lagging, if the core losses are equal to 3 MW.

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 3.9P

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