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Three synchronous generators, each of which is rated to 100 MVA, 11 KV, have an impedance per unit of 0.15. If all three generators are replaced by a single equivalent generator, what will be the effective per unit impedance of each generator?

Three synchronous generators, each of which is rated to 100 MVA, 11 KV, have an impedance per unit of 0.15. If all three generators are replaced by a single equivalent generator, what will be the effective per unit impedance of each generator? Correct Answer 0.05

Using Thevenin's Theorem, Vth = V all the three impedances will be in parallel.

Single line diagram:

Key Points

  1. All generators are connected in parallel to increase current going to the line because all generators are at equal voltages.
  2. Generators are shown with their impedances in a single line diagram.

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