# Power Systems Questions and Answers – Line Compensation – 1

This set of Power Systems Multiple Choice Questions & Answers (MCQs) focuses on “Line Compensation – 1”.

1. The instantaneous voltage wave in the long transmission line is a function of _____________
a) time and distance
b) time
c) distance
d) time, distance and reactive inductance

Explanation: It will be a function of time and distance.

2. At any point along the line, the instantaneous voltage is ___________
a) sum of incident and reflected voltage
b) incident voltage
c) sum of incident and refracted voltage
d) twice the incident voltage

Explanation: V(t) = Vincident+Vrefracted.

3. The equation given below is the voltage equation,

Then it is ________________
a) reflected wave receiving to sending end
b) reflected wave sending to receiving end
c) incident wave from receiving end to sending end
d) refracted wave from receiving end to next end

Explanation: From the equation, cos⁡(wt-βx+Ф2), it is clear that the wave is travelling in left to right and the amplitude is reduced, so it’s a reflected wave.

4. When can an incident wave not distinguish between the termination and an infinite continuation of line?
a) When line is terminated by its characteristic impedance
b) When line is terminated by its surge impedance
c) When line is open
d) When line is terminated by its characteristic and surge impedance

Explanation: The characteristic (surge) impedance at the receiving end will cause a confusion for the incident wave.

5. Ferranti effect is more prominent due to ____________
a) line capacitance
b) surge capacitance
c) stray capacitance
d) all of the mentioned

Explanation: Line capacitance causes the no load receiving end voltage to be more than receiving end.

6. The voltage rise happening at the receiving end due to the line charging capacitance has a magnitude of _______________
a) ω2CLl2
b) ω2CLl2/2
c) ω2l2/v2
d) ω2CLl2 and ω2l2/v2

Explanation: The circuit diagram for the LTL is

Is= jVswCl
Vr = Vs – Is(jwLl) = Vs + Vsw2CLl2
=Vs(1+ w2CLl2).

7. The receiving end voltage at the no load will be ____________
a) Vs(1+ w2CLl2)
b) (1+ w2CLl2)
c) Vs/(1+ w2CLl2)
d) Vs

Explanation: The circuit diagram for the LTL is

Is= jVswCl
Vr = Vs – Is(jwLl) = Vs + Vsw2CLl2
=Vs(1+ w2CLl2).

8. If a line is considered with negligible power losses, then the real power transmitted will be proportional to sinδ.
a) True
b) False

Explanation: Pr = |Vs||Vr|(sinδ)/X.

9. If a line is considered with negligible power losses, then the real power transmitted will be proportional to ___________
a) sinδ
b) cosδ
c) δ
d) sin2δ

Explanation: Pr = |Vs||Vr|(sinδ)/X.

10. If a line is considered with negligible power losses, then the reactive power transmitted is proportional to receiving end voltage.
a) True
b) False

Explanation: Its incorrect, Q depends on the voltage drop across the line.

Sanfoundry Global Education & Learning Series – Power Systems.

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