Power Systems Questions and Answers – Inductance of Composite Conductor Lines…

This set of Power Systems Multiple Choice Questions & Answers (MCQs) focuses on “Inductance of Composite Conductor Lines – 2”.

1. Based on the below given phasor diagram, the condition for the zero voltage regulation occurs at ______________
The condition for the zero voltage regulation occurs at OC = OA for phasor diagram
a) OC = OA
b) OC > OA
c) OC = OD
d) DC = AB
View Answer

Answer: a
Explanation: Zero VR occurs when both the emf and the load voltage are equal.

2. In the below given phasor diagram representation, the angle sine(AOD) for the condition of zero voltage regulation will be given by ___________
Find the angle sine(AOD) for the condition of zero voltage regulation
a) \(\frac{IZ}{2Vr}\)
b) \(\frac{2Vr}{IZ}\)
c) \(\frac{2IZ}{Vr}\)
d) None of the mentioned
View Answer

Answer: a
Explanation: Geometrically sin(AOD) = AD/OA = (AC/2)/|Vr|

3. In the phasor diagram representation, the angle (AOD) for the condition of zero voltage regulation will be given by _______________
Find the angle (AOD) for the condition of zero voltage regulation
a) \(\sin^{-1} \left( \frac{IZ}{2Vr} \right)\)
b) \(\cos^{-1} \left( \frac{IZ}{2Vr} \right)\)
c) \(\tan^{-1} (IZ)\)
d) \(\sin^{-1} \left( \frac{IZ}{3Vr} \right)\)
View Answer

Answer: a
Explanation: It is geometrically sin(AOD) = AD/OA = (AC/2)/|Vr|
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4. In the phasor diagram, the angle Фr such that zero voltage regulation occurs at the receiving end of a transmission line for a leading load, is given as __________
Find the angle (AOD) for the condition of zero voltage regulation
a) \(\frac{\pi}{2} – \theta + \sin^{-1} \left( \frac{IZ}{2Vr} \right)\)
b) \(\frac{\pi}{2} + \theta + \sin^{-1} \left( \frac{IZ}{2Vr} \right)\)
c) \(\frac{\pi}{2} – \theta + \cos^{-1} \left( \frac{IZ}{2Vr} \right)\)
d) \(\theta + \sin^{-1} \left( \frac{IZ}{2Vr} \right)\)
View Answer

Answer: a
Explanation: It is geometrically sin(AOD) = AD/OA = (AC/2)/|Vr|.
Then, for the leading load Фr=\(\frac{\pi}{2} – \theta + \sin^{-1} \left( \frac{IZ}{2Vr} \right)\)

5. In the phasor diagram, the angle Фr such that zero voltage regulation occurs at the receiving end of a transmission line for a lagging load, is given as ___________
Find the angle (AOD) for the condition of zero voltage regulation
a) \(\theta + \sin^{-1} \left( \frac{IZ}{2Vr} \right)\)
b) \(\frac{\pi}{2} + \theta + \sin^{-1} \left( \frac{IZ}{2Vr} \right)\)
c) \(\frac{\pi}{2} – \theta + \sin^{-1} \left( \frac{IZ}{2Vr} \right)\)
d) \(\theta + \sin^{-1} \left( \frac{IZ}{2Vr} \right)\)
View Answer

Answer: b
Explanation: For the lagging load, Фr = \(\frac{\pi}{2} + \theta + \sin^{-1} \left( \frac{IZ}{2Vr} \right)\)

6. 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.
View Answer

Answer: a
Explanation: It is a short transmission line as the capacitance considered is zero and so the line charging current is also zero.

7. 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
View Answer

Answer: a
Explanation: 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.

8. 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
View Answer

Answer: a
Explanation: Increasing the frequency decreases the reactance and thus charging current increases and so the MVAR.

9. 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
View Answer

Answer: a
Explanation: Due to Ferranti effect, the voltage will be more at receiving end in a LTL.
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10. 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
View Answer

Answer: a
Explanation: In the nominal pi method, the losses are minimum.

Sanfoundry Global Education & Learning Series – Power Systems.

To practice all areas of Power Systems, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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