TS Mocktest 2021-7

1. Which of the following circuit breakers normally we can find in a 220kV/132kV substation

A. Vacuum circuit breaker
B. Air break circuit breaker
C. Minimum oil circuit breaker
D. SF6 circuit breaker

Answer : SF6 circuit breaker
Explanation:-

2. A lightning arrester provides

A. A low impedance path between line and ground during normal operation and lightning
B. A high impedance path between line and ground during normal operation and lightning
C. A high impedance path between line and ground during lightning and low impedance path during normal operation
D. A low impedance path between line and ground during lightning and high impedance path during normal operation

Answer : A low impedance path between line and ground during lightning and high impedance path during normal operation
Explanation:-

3. In a large building, there are 15 bulbs of 40 W, 5 bulbs of 100 W, 5 fans of 80 W and 1 heater of 1 kW. The voltage of the electric mains is 220 V. The minimum capacity of the main fuse of the building will be

A. 8 A
B. 10 A
C. 12 A
D. 14 A

Answer : 12 A
Explanation:-
The total load of building is (15*40)+(5*100)+(5*80)+(1*1000)=600+500+400+1000==2500 W
Current=Power/Voltage=2500/220=11.3A====12 A

4. Ring main distribution is preferred to a radial system because

A. Voltage drop in the feeder is less and supply is more reliable
B. Voltage drop in the feeder is less and power factor is high
C. Power factor is high and supply is more reliable
D. Power factor is high and system is less expensive

Answer : Voltage drop in the feeder is less and supply is more reliable
Explanation:-

5. If the height of the transmission towers is changed, which of the following parameters is likely to change

A. Resistance
B. Inductance
C. Capacitance
D. Conductance

Answer : Capacitance
Explanation:-

6. The insulators used on 220 kV transmission line are of

A. Suspension type
B. Pin type
C. Shackle type
D. Cone type

Answer : Suspension type
Explanation:-

7. Ferranti effect on long overhead line is experienced when it is

A. lightly loaded
B. on full load at unity pf
C. on full load at 0.8 pf lag
D. on any load

Answer : lightly loaded
Explanation:-

8. Hundred percent string efficiency means

A. one of the insulator discs shorted
B. zero potential across each disc
C. Equal potential across each insulator disc
D. one of the insulator discs open circuited

Answer : Equal potential across each insulator disc
Explanation:-

9. Transposition of transmission line is done to

A. reduce line loss
B. reduce skin effect
C. balance line voltage drop
D. reduce corona

Answer : balance line voltage drop
Explanation:-

10. The insulation resistance of a cable of length 10 km is 1 M ohm, its resistance of 50 Km length will be

A. 1M Ohm
B. 5 M Ohm
C. 0.2 M Ohm
D. 0.5 M Ohm

Answer : 0.2 M Ohm
Explanation:- The Insulation resistance is inversly proportional to the length, for the 50Km length the insulation resistance is decreased by a factor of 5 so 1/5=0.2 Mohm