# POWER SYSTEMS III MCQ TYPE QUESTIONS ❓

This question ❓ is very important regarding your makaut semester examination
This question ❓ is made looking after your university decided MCQ based exam during the pandemic situation

"POWER SYSTEM -III "

### Electrical engineering 4th year student and this question also comes in your compatitave examination like GATE, PSU, & Other gov. And private exam include your state gov. Examination

1.What is the value of Inductive reactance in short transmission lines?
a) More at reciving end
b) More at sending end
c) Uniformly distributed over entire length
d) More in middle of sending end and reciving end

2.Regulation of short transmission lines depends:
a) Only on line resistance
b) Only on line inductance
c) Only on line capacitance
d) On line inductance and line resistance

3.What is the percentage voltage regulation of short transmission line if its sending end and reciving end voltages are 160 KV and 132 KV respectively?
a) 30 %
b) 21.21 %
c) 12.12 %
d) 38.22 %
Explanation: % Voltage Regulation = (Sending end voltage -Reciving end voltage) ÷ Reciving end voltage
= [( 160 – 132 ) × 100] ÷ 132
= 21.21 %.

4. A single phase transmission line is transmitting 1,100 KW power at 11 KV and at unity power fector. If it has a total resistance of 5 Ω, what is the efficiency of the transmission line?
a) 80 %
b) 89.65 %
c) 97.24 %
d) 99.54 %

Explanation: Efficiency (η) = Power delivered ÷ (Power Delivered + line losses)
Line current (I) = P/V
= (1100 × 1000/11000)
= 100 Amp.
Line losses = I2 R
= (100)2 5
= 50 KW
η = [11000/(11000+50)] × 100
= 99.54 %.

5. Voltage regulation of a transmission line should be ________
a) Minimum
b) Maximum
c) Greater than 50 %
d) Less than 50 %

6. Which of the following is correct operating voltage range for medium transmission lines.
a) More than 765 KV
b) More than 400 KV
c) More than 20 KV
d) More than 132 KV
Explanation: Transmission lines having length more than 80 Km and less than 200 Km, operating voltage between 20 KV and 100 KV fall in the category of medium transmission lines.

7. What is the value of the charging current flowing to earth in medium transmission line.
a) Very high
b) Medium
c) Negligible
d) No capacitance

8. Performance analysis of medium transmission line is done ________
a) By reactance diagram
b) By symmetrical component analysis method
c) By neglecting line inductance
d) On per phase basis

9. What is the value of shunt capacitance of medium transmission line?
a) Very high
b) Medium
c) Zero
d) Negligable

10. Series inductance and series resistance of medium transmission lines are taken as:
a) Distributed and Lumped
b) Lumped and Distributed
c) Distributed
d) Lumped

11. Length of long transmission line is more than ___________
a) 80 Km
b) 50 Km
c) 120 Km
d) 200 Km

12. Range of surge impedance for an overhead transmission line is ____________
a) 12 Ω – 144 Ω
b) 40 Ω – 60 Ω
c) 400 Ω – 600 Ω
d) 300 Ω – 900 Ω

13. Range of surge impedance for an underground cables is _____________
a) 12 Ω – 144 Ω
b) 40 Ω – 60 Ω
c) 400 Ω – 600 Ω
d) 300 Ω – 900 Ω

14.  The voltage rating of long transmission line is _________
a) 20 KV to 100 KV
b) Upto 20 KV
c) Above 100 KV
d) 60 KV to 80 KV

15. What is the value of characteristics impedance for loss free transmission line?
a) √(L/C)
b) √(R/C)
c) √(LC)
d) √(C/L)

16. Ferranti effect is not a problem for ________
a) Long Transmission lines
b) Medium Transmission lines
c) Short Transmission lines
d) Transmission line having high
capacitance

17. What happens during the Ferranti effect?
a) Reciving end current becomes more than sending end current
b) Reciving end voltage becomes more than sending end voltage
c) Reciving end power becomes more than sending end power
d) Reciving end frequency becomes more than sending end frequency

18. A transmission line of 200 Km is supplying at 50Hz frequency. What is the percentage rise in voltage at reciving end?
a) 20%
b) 1.2%
c) 2.19%
d) 20.8%
Explanation: Percentage rise in voltage = (ω2 l2 10-8 )/18
Solving this % Vrise = {(2 × Ω × 50) × 2002 × 10-8}/18
= 2.19%.

19. What is the limit within which the consumer’s end terminal voltage should be maintained?
a) ± 9 %
b) ± 10 %
c) ± 5 %
d) ± 6 %

20. Which of the following equipment is not used for voltage control?
a) Tap changing transformer
b) Induction generators
c) Series compensators
d) Synchronous phase modifiers

21. What is the full form of AVR? This term is related to voltage control?
a) Automatic Voltage Rectifier
b) Actuated Voltage Rectifier
c) Automatic Voltage Rectifier
d) Automatic Voltage Regulator

22. In a synchronous generator for how much time subtransient period of symmetrical short circuit current lasts?
a) For 200 Cycles
b) For 500 Cycles
c) For 30 Cycles
d) For 2 Cycles

23. What is the phase current in phase Y and in phase B out of R-Y-B when sudden short circuit to all three phases occurs at no load? It is given that after fault current in phase R is equal (Vm Sin ωt)
a) Y = Vm Sin(ωt +60°) & B = VmSin(ωt +120°)
b)Y=vmSin(ωt+120°) &B=VmSin(ωt+240°)
c) Y = Vm Sin(ωt +240°) & B = Vm Sin(ωt +120°)
d) Y = Vm Sin(ωt +90°) & B = Vm Sin(ωt -90°)

24. Which of the following reactance is eliminated first in synchronous generator just after the symmetrical fault?
a) Leakage reactance
b) Damper winding reactance
c) Armature winding reactance
d) Field winding reactance

25. The maximum power delivered to the load for short transmission line is at
a) β=α
b) β>α
c) β=δ
d) β>δ

26. For a given power system, its zero and maximum regulation will occur at the impedance angle of
a) 45
b) 90
c) 0
d) 60

27. The charging currents due to shunt admittance can be neglected for ______ transmission line?
a) short
b) long
c) medium
d) all of the mentioned

28. A three phase transformer has a name plate details of 30 MVA and voltage rating of 230Y kV/69∆ kV with a leakage reactance of 10% and the transformer connection via wye-delta. Taking a base of 230 kV on the high voltage side, turns ratio of the windings is
a) 2
b) 1.5
c) 6
d) 4
Explanation: n= VHV/VLV = (230/√3)/69=1.92 =2

29. A 200 bus power system has 160 PQ bus. For achieving a load flow solution by N-R in polar coordinates, the minimum number of simultaneous equation to be solved is ___________
a) 359
b) 329
c) 360
d) 320
Explanation: Total buses = 200
PQ buses = 160
PV buses = 200-160 = 40
Slack bus = 1
Total number of equation = (40-1)*1 + (160*2) = 359

30. A 400 V, 50 Hz three phase balanced source ripples to a star connected load whose rating is S(=300+j400) kVA. The rating of the delta connected capacitor bank needed to bring p.f. to 0.9 lagging is _______ KVAR.
a) 254.7
b) 25.4
c) 84.9
d) 284.5
Explanation: Qc = P[tanθ1 – tanθ2] =300[(4/3) – cos-10.9] = 254.72 kVAR.