Power Systems Questions on “Inductance of Composite Conductor Lines – 2”.
1. For a transmission line under study of failure analysis, it is observed that the current at the receiving end is same as that of the sending end, then what can be concluded about the nature of the transmission line?
A. It is short TL
B. It is medium TL
C. It is long TL
D. Current is always same at the receiving end and the sending end.
Answer: A
Clarification: It is a short transmission line as the capacitance considered is zero and so the line charging current is also zero.
2. A single phase 50 hz, generator supplies an inductive load of 5 MW at a power factor of 0.8 lagging using OHTL over 20 km. The resistance and reactance are 0.39Ω and 3.96 Ω. The voltage at receiving station is maintained at 10 KV. The sending end voltage is ______
A. 11.68 kV
B. 7.62 kV
C. 14.4 kV
D. 12.2 kV
Answer: A
Clarification: Current, I = 5000/(10*0.8)
=625 A
Vs = |Vr|+|I|*(RcosФr + XsinФr)
= 10000+625(0.39*0.8+3.96*0.6)
= 11.68kV.
3. When the frequency of the system is increased, the charging MVAR of a system will __________
A. increase
B. decrease
C. remain constant
D. cannot be said
Answer: A
Clarification: Increasing the frequency decreases the reactance and thus charging current increases and so the MVAR.
4.Taking a case study for the long line under no load condition, the receiving end voltage is ____________
A. more than the sending-end voltage
B. less than the sending-end voltage
C. equal to the sending-end voltage
D. it will not be affected by the loading
Answer: A
Clarification: Due to Ferranti effect, the voltage will be more at receiving end in a LTL.
5. While given receiving-end voltage for a long transmission line, the sending-end voltage is more than the actual is found out using _____________
A. Nominal-pi method
B. Nominal-T method
C. Load end capacitance method
D. Any of the mentioned
Answer: A
Clarification: In the nominal pi method, the losses are minimum.