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A 50 Hz synchronous generator is initially connected to a long lossless transmission line which is open circuited at the receiving end. With the field voltage held constant, the generator is disconnected from the transmission line. Which of the following may be said about the steady state terminal voltage and field current of the generator?

A 50 Hz synchronous generator is initially connected to a long lossless transmission line which is open circuited at the receiving end. With the field voltage held constant, the generator is disconnected from the transmission line. Which of the following may be said about the steady state terminal voltage and field current of the generator? Correct Answer The magnitude of terminal voltage decreases, and the field current does not change.

A long transmission line under no-load conditions behaves as the capacitive load. The effect of armature current is purely magnetization. When the alternator is disconnected, there is no magnetizing effect. So the terminal voltage decreases with the same field current.

Explanation:

When the generator is connected to an open-circuit transmission line, the line draws a charging current, therefore Vt > Eg.

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But, when the generator is disconnected from the line, no charging current is delivered by the generator, i.e.,

Ic = 0 ⇒ Vt = Eg.

So, the terminal voltage decreases.

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