Transmission Line MCQ

1. An 11 kV, 3-phase transmission line has a resistance of 1.5 Ω and reactance of 4 Ω per phase. The efficiency of the line when supplying the load of 4 MW at 0.8 lagging power factor is nearly

  1. 99%
  2. 95%
  3. 92%
  4. 90%
Answer. c

2. At what power factor will a lossless line with a reactance of 0.6 pu exhibit zero regulation given that the sending end voltage is 1.0 pu?

  1. 0.800 lead
  2. 0.800 lag
  3. Unity p.f.
  4. 0.954 lead
Answer. d

3. The time interval needed for a surge to travel to the end of a 600 Km long overhead transmission line is

  1. 6 s
  2. 2 s
  3. 20 ms
  4. 2 ms
Answer. d

4. An extra high voltage transmission line of length 300 km can be approximated by a lossless line having propagation constant β = 0.00127 rad/km. The percentage ratio of line length to wavelength will nearly be

  1. 19%
  2. 24%
  3. 6%
  4. 12%
Answer. c

5. Consider a transmission line. The sending end voltage and current are expressed in terms of receiving end voltage and current for the network as

Vs = AVR + BIR


where A, B, C and D are generalized circuit constants.

The condition for symmetry for the network is

  1. A=D
  2. A=C
  3. B=D
  4. B=C
Answer. a

6. Which of the following is the demerit of a ‘constant voltage transmission system’?

  1. Increase of short-circuit current of the system
  2. Availability of steady voltage at all loads at the line terminals
  3. Possibility of better protection for the line due to possible use of higher terminal reactances
  4. Improvement of power factor at times of moderate and heavy loads
  5. Possibility of carrying increased power for a given conductor size in case of long-distance heavy power transmission
Answer. a

7. The square root of the ratio of line impedance and shunt admittance is called the

  1. surge impedance of the line
  2. the conductance of the line
  3. regulation of the line
  4. none of the above
Answer. a

8. The phenomenon of rising in voltage at the receiving end of the open-circuited or lightly loaded line is called the

  1. Seeback effect
  2. Ferranti effect
  3. Raman effect
  4. None of the above
Answer. b

9. 310 km line is considered as

  1. a long line
  2. a medium line
  3. a short line
  4. any of the above
Answer. a

10. Which of the following are the constants of the transmission lines?

  1. Resistance
  2. Inductance
  3. Capacitance
  4. All of the above
Answer. d
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