Power System(Transmission & Distribution)-01

A to Z Technique's Solutions - July 03, 2020

Power System(Transmission & Distribution)-01:

1) The generating voltage and frequency in Bangladesh is about?

a. 11 kV and 60 Hz
b. 11 kV and 50 Hz
c. 220 kV and 60 Hz
d. 220 kV and 50 Hz

2) Which type of system is generally adopted for the generation and transmission of electrical power?

a. 3 phase 4 wire
b. 2 phase 3 wire
c. 3 phase 3 wire
d. None of these

3) The rated voltage of a 3 phase power system is given by ____________.

a. rms peak voltage
b. Peak phase voltage
c. rms line to line voltage
d. Peak line to line voltage

4) Which of these systems uses the 3 phase 4 wire system?

a. Primary distribution
b. Secondary distribution
c. Primary transmission
d. Secondary transmission

5) With the same maximum voltage to earth, which among the following AC systems with 0.8 pf will need more copper compared to 2 wire system?

a. Single phase, 2 wire
b. Single phase, 3 wire
c. Three phase, 3 wire
d. Three phase, 4 wire

6) In transmission system, the weight of copper used is proportional to

a. Square of voltage
b. Voltage
c. 1 / (square of voltage)
d. 1 / voltage

7) Greater the power factor the ________________ is the volume of copper required.

a. Greater
b. Smaller
c. Both are equal
d. Depending of the level of transmission

8) Line efficiency increases for ________ transmission voltages.

a. Higher
b. Lower
c. Both (a) and (b)
d. None of these

9) The most important disadvantage of using the high voltage for transmission is

a. The increased cost of insulating the conductors.
b. The increased cost of transformers, switchgear and the other terminal apparatus.
c. Both (a) and (b)
d. There is a reduction in the corona loss.

10) The most suitable practical value of primary distribution is?

a. 66 kV
b. 6.6 kV
c. 230 V/ 400 V
d. 22 kV

11) What is the main drawback of overhead system over underground system?

a. Surge problem
b. High initial cost
c. Higher charging current
d. Underground system is more flexible than overhead system

12) For the same conductor length, same amount of power, same losses and maximum voltage to earth, which system requires minimum conductor area?

a. 3 wire ac
b. 2 wire ac
c. 2 wire dc
d. Single phase

13)What is the highest possible transmission voltage in Bnagladesh?

a. 230kV
b. 66 kV
c. 132 kV
d. 400 kV

14) What is the main reason for using the high voltage for the long distance power transmission?

a. Reduction in the transmission losses
b. Reduction in the time of transmission
c. Increase in system reliability
d. None of these

15) The volume of copper required in case of three wire two phase ac systems is how many times to that of two wired dc system?

a. 2/cos²φ
b. 1/2 cos²φ
c. 1.457/ cos²φ
d. 6/1.457 cos²φ

16) The volume of copper required in case of four wire two phase ac systems is how many times to that of two wired dc system?

a. 2/cos²φ
b. 1/2 cos²φ
c. 1.457/ cos²φ
d. 6/1.457 cos²φ

17) By increasing the transmission voltage double of its original value, the same power can be despatched keeping the line losses _______________.

a. Equal to its original value.
b. Half of its original value.
c. Double the original value.
d. One - fourth of the original value.

18) Which among these is/are the fundamental economical principles that influence/s the design of transmission lines?

a. Economic choice of conductor size.
b. Economic choice of transmission voltage.
c. Both (a) and (b)
d. Economic choice of transmission line length.

19) The most economical area of conductor is that for which the total annual cost of transmission line is minimum. Which law states this?

a. Lenz’s law
b. Kelvin’s law
c. Faraday’s law
d. Ohm’s law

20) The account of interest and depreciation on the capital cost of complete installation of transmission line is denoted by which factor?

a. Annual charge on capital outlay
b. Annual cost of energy wasted
c. Both (a) and (b)
d. Neither of these

21) The annual charge is given by

a. P₁ + P₂ / a
b. (P₁ + P₂) * a
c. P₁ + P₂ * a
d. P₁ * a + P₂