Power system MCQ's

1.What is the line to earth capacitance value of the short transmission line. 

A) Low 
B) Medium 
C) High
D) Negligible 

2.Out of the following types of energy sources, which is non-renewable?

A) Solar energy
B) Wind energy
C) Coal
D) Biomass

3. The presence of earth in case of overhead lines?

A) Increase the capacitance 
B) Decrease the capacitance 
C) Increase the inductance
D) Decrease the inductance

4. The self-inductance of a long cylindrical conductor due to its internal flux linkages is 1 kH/m. If the diameter of the conductor is doubled, then the self-inductance of the conductor due to its internal flux linkages would be?

A) 0.5 kH/m
B) 1 kH/m
C) 1.414kH/m
D)  4kH/m

5.A bundled conductor line compared to a single conductor line (with same conductor cross-sectional area and same mean distance between conductors) has Self GMD, Mutual GMD and Inductance/phase?

A) Lower, nearly same and higher
B) Higher, lower and nearly same
C) Higher, nearly same and lower
D) Lower, higher and higher

6. What is the value of charging current in short transmission lines?

A) Less than medium transmission lines
B) Equal to medium transmission lines
C) More than medium transmission lines
D) More than long transmission lines

7. For a three phase transmission line, the conductors are spaced horizontally with spacing between adjacent conductors equal to‘d’. If the conductors are rearranged to form an equilateral triangle of side‘d’, then 

A) The line capacitance and inductance both increase
B) The line capacitance and inductance both decrease
C) The line inductance increases while the capacitance decreases
D) The line inductance decreases while the capacitance increases

geometric mean distance,

8. The given figure represents :

A) ultra-long transmission line
B) short transmission line
C) long transmission line
D) medium transmission line

9. In Nominal-T configuration of medium transmission line, the shunt capacitance is assumed to be :

A) concentrated at the middle of the line 
B) concentrated at the sending end of the line 
C) distributed equally throughout the length 
D) concentrated at the receiving end of the line

Explanation: In Nomial-T model of transmission line, the whole shunt capacitance of line is assumed to be lumped at the middle of the line.

10.The leakage current in the transmission lines is referred to as the . 

A) radiation 
B) resistance 
C) polarisation 
D) conductance 

11.The characteristic impedance of a lossless transmission line necessarily is. 

A) Purely imaginary 
B) Zero 
C) Complex
D) Pure real

ANSWER= (D) Pure real
Explaination:- 

12.Consider the following statements :

The characteristic impedance of a transmission line can increase with the increase in

1. Resistance per unit length

2. Conductance per unit length

3. Capacitance per unit length

4. Inductance per unit length?

A) 1&2
B) 2&3
C) 1&4
D) 2&4

ANSWER= (C) 1&4
Explanation: 

13.When will the effective resistance of a conductor be the same as ohmic resistance ?

A) When current is uniformly distributed in the conductor cross-section
B) When current is in true sine wave form 
C) When voltage is low 
D) When power factor is unity

14.The inductance of single phase two wire power transmission line per km gets doubled when the distance between the?

A) wires is doubled 
B) wires is increased as square of the original distance 
C) wires is increased four times
D) wires is halved

As per given in question,Let distance between conductors is D' when inductance gets doubled

 

15. The characteristic impedance of a transmission line with impedance and admittance of 25 and 16, respectively, is ?

A) 1.76
B) 1
C) 1.25
D) 0.72

ANSWER= (C) 1.25
Explanation:Given that, impedance (ZOC) = 25

Admittance (YSC) = 16

Characteristic impedance

16. It is given that for a system, the equivalent radius of each conductor is 'x'. Find the equivalent radius or self-GMD (geometric mean distance) of four bundled conductor apart by a distance 'a' from their centers

A) 1.024x1/2a3/4
B) 2.024x1/4a3/2
C) 1.024x1/4a3/4
D) 2.024x1/2a3/4

ANSWER=(C)1.024x1/4a3/4
Explanation: 

17. Which of the two generalized constants of a transmission line are equal?

A) A and B
B) B and C
C) C and D
D) A and D

ANSWER= (D)A and D
Explanation: In symmetrical networks the impedance remains same,

 A = D and AD- BC = 1

These two conditions hold in a transmission line.

18. The_________causes a real power loss in the conductor of the transmission lines.

A) Inductance 
B) Series resistance 
C) Capacitance 
D) Shunt conductance 

ANSWER= (B) series resistance 

 Explanation:The series resistance causes a real power loss in the conductor of the transmission line. Due to the resistance in the transmission line I2R loss (Ohmic) loss is highest in transmission line.

Power loss = I2R

19. In describing the transmission parameters

A) The input voltage and current are express in terms of output voltage and current
B) The input voltage and output voltage are express in terms of output current and input current 
C) The input voltage and output current are express in terms of input current and output voltage 
D) None of the above 

ANSWER= (A)  The input voltage and current are express in terms of output voltage and current
Explanation:In describing the transmission parameters the input voltage and current are express in terms of output voltage and current.

Where,

Vs = Sending end voltage (input voltage)

Is= Sending end current (input current)

vr= Receiving end voltage (output voltage)

Ir = Receiving end current (output current)

A, B, C and D are the constant also known as the transmission parameters or chain parameters.

20. The presence of earth in case of overhead lines?

A) Increase the capacitance 
B) Decrease the capacitance 
C) Increase the inductance
D) Decrease the inductance

ANSWER= (A)  Increase the capacitance
Explanation: As the earth is considered to be an infinite source of electrons, the presence of overhead lines causes charge carrier to be separated by a dielectric(air), causing an increase in capacitance.