A three-phase 50 Hz, 200 MVA, 220/66 kV transformer has a clock number of Yd11. The transformer winding resistances are 2.0 N and 0.12 N, and the leakage reactances are 10 N 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) Calculat
A three-phase 50 Hz, 200 MVA, 220/66 kV transformer has a clock number of Yd11. The transformer winding resistances are 2.0 N and 0.12 N, and the leakage reactances are 10 N 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) Calculat
Introductory Circuit Analysis (13th Edition)
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Chapter1: Introduction
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Three-Phase Transformers
Three-segment transformers are a type of transformer used to transform voltages of electrical systems into three ranges. Two type transformers are shell-type transformer and core type transformer. In brief, it could be described because of the exquisite kinds of configurations.
Transformer
Ever since electricity has been created, people have started using it in its entirety. We see many types of Transformers in the neighborhoods. Some are smaller in size and some are very large. They are used according to their requirements. Many of us have seen the electrical transformer but they do not know what work they are engaged in.
Question
![QUESTION TWOo
A three-phase 50 Hz, 200 MVA, 220/66 kV transformer has a clock number of Yd11. The
transformer winding resistances are 2.0 N and 0.12 N, and the leakage reactances are 10 N 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 1.6 MW.
(e) Suggest the most suitable method of cooling this transformer and explain how the suggested
method works.
() Why are most power transformers and distribution transformers' tanks oil-filled?
To increase the supply capacity, the transformer described above is connected in parallel with a
three-phase, 50 Hz, 120 MVA, 220/66 kV transformer with clock number Yd11.
(g) Determine the winding resistances and leakage reactances of the second transformer
referred to the high-voltage side, that will result in the two transformers sharing the load
proportionally to the apparent power ratings of the two transformers.
(h) What conditions should be met before two or more transformers are connected in parallel.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F5aea65da-032c-4646-ab74-c0eb3075ea35%2Fc0d3dfbc-467b-4da2-812d-e7d398edda20%2Fl0sbno_processed.jpeg&w=3840&q=75)
Transcribed Image Text:QUESTION TWOo
A three-phase 50 Hz, 200 MVA, 220/66 kV transformer has a clock number of Yd11. The
transformer winding resistances are 2.0 N and 0.12 N, and the leakage reactances are 10 N 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 1.6 MW.
(e) Suggest the most suitable method of cooling this transformer and explain how the suggested
method works.
() Why are most power transformers and distribution transformers' tanks oil-filled?
To increase the supply capacity, the transformer described above is connected in parallel with a
three-phase, 50 Hz, 120 MVA, 220/66 kV transformer with clock number Yd11.
(g) Determine the winding resistances and leakage reactances of the second transformer
referred to the high-voltage side, that will result in the two transformers sharing the load
proportionally to the apparent power ratings of the two transformers.
(h) What conditions should be met before two or more transformers are connected in parallel.
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