2. An over-excited synchronous machine delivers reactive power to a transmis- si

Question

2. An over-excited synchronous machine delivers reactive power to a transmis- sion line. Explain this statement and what is meant by the term "over-excited". 3. An under-excited synchronous machine absorbs reactive power from a trans- mission line. Explain this statement, and what is meant by the term "under- excited" 4. A 200 kilometer, 300 kV, 50 Hz transmission line has a reactance of 0,4 n per kilometer and a distributed capacitance of 400 000 n per kilometer. Draw an equivalent circuit of the line per phase. Calculate the line current per phase at the sender end when the receiver is open. What is the reactive power supplied to the sender? 5. A 150 MW generator having a nominal voltage of 12 kv and a synchronous reactance of 4 n is connected to the transmission line of Question 4 via a step-up transformer having a ratio of 12 kV/300 kv. lf the excitation voltage Eo

Explanation / Answer

1. In this case the DC voltage provides more excitation than required so it accomodates that extra flux by setting flux in opposite direction with the help of AC supply .

2.In this case, DC supply is not enough to produce the required flux so AC supply will act upon to aid DC to produce required flux.

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