MCQs on Switchgear and Protection

Power System MCQs

1. For an arcing fault where the arc resistance is significant, an impedance or admittance relay will____.

a. The reach will depend on the arcing resistance and may under reach or over reach

b. The reach of relay is unaffected

c. Under reach

d. Over reach

2. Kick fuses are used across relay coils to prevent relay operation during______.

a. Bolted faults

b. Line to ground faults

c. Inrush current of transformers when they are energized

d. Heavy external faults

3. There is a problem of high transient over voltages while interrupting______.

a. Capacitive currents

b. Inductive currents

c. Heavy short circuit current

d. (a) or (c)

4. The most suitable circuit breaker for voltages above 220 kV is_______.

a. Oil CB

b. Air blast CB

c. SF₆ CB

d. Vacuum CB

5. Pilot relaying schemes are used for protection of______.

a. Instrument transformers

b. Transmission lines

c. Transformers

d. Bus bars

6. High synchronous reactance is preferred in the present day alternators because one can have______.

a. High voltage regulation with load

b. Reduced transient currents

c. Reduced harmonic currents

d. Reduced sub-transient currents

7. Current chopping is due to_____.

a. Interruption of unity power factor loads

b. Interruption of low inductive currents

c. Interruption of bolted faults

d. Interruption of heavy capacitive currents

8. The relay most likely to maloperate during power swing is______.

a. Reactance relay

b. Mho relay

c. Impedance relay

d. Both (a) and (c)

9. For protection of short lines against ground faults where arc resistance is comparable to the impedance of the line, the preferred relay is______.

a. Overcurrent relay

b. Admittance relay

c. Reactance relay

d. Impedance relay

10. Current chopping is minimum in case of_______.

a. ABCB

b. SF₆ CB

c. Oil CB

d. Vacuum CB

11. Reactor switching is done with____.

a. Minimum oil circuit breaker

b. SF₆ circuit breaker

c. Vacuum circuit breaker

d. Air blast circuit breaker