SWITCHGEAR AND PROTECTION MCQ-1

1. In a circuit breaker the current which exists at the instant of
contact separation is known as....

  *breaking current
  * surge current
  * recovery current
  * re striking current
  * The Right Answer: breaking current

2. Bucholz relay used on..

  * Air cooled transformer
  * oil cooled transformer
  * welding transformer
  * All of above
  * The Right Answer: oil cooled transformer

3. The SF_6 gas is...

  * non poisonous
  * insulating properties
  * non inflammable
  * none of above
  * The Right Answer: non inflammable

4. The rating of a wire is always expressed in

  * Ampere
  * Ampere-volt
  * kW
  * all of above
  * The Right Answer: Ampere

5. Oil immersion of contacts is the method of ...

  * arc prevention
  * de ionization
  * arc dispersion
  * none of above.
  * The Right Answer: arc dispersion

6. Air blast circuit breakers for 400 kV. Power system are designed to
operate in

  * 50 micro seconds
  * 50 milli seconds
  * both A and B
  * none of above
  * The Right Answer: 50 milli seconds

7. Which of the following contact point metals has the highest melting
point ?

  * silver
  * Copper
  * Tungsten
  * Gold
  * The Right Answer: Tungsten

8. HRC fuses are....

  * Holding and Resisting current fuses
  * High Rating fuse
  * High Rupturing Capacity fuse
  * all of above
  * The Right Answer: High Rupturing Capacity fuse

9. A material best suited for manufacturing of fuse wire is...

  * Aluminium
  * Copper
  * silver
  * all of above
  * The Right Answer: silver

10. A fuse is normally a ...

  * voltage limiting device
  * current limiting device
  * power limiting device
  * all of above
  * The Right Answer: current limiting device

11. The basic function of a circuit breaker is to.

  * extinguish the arc
  * arc produce
  * ionize the surrounding air
  * none of above
  * The Right Answer: extinguish the arc

12. A differential relay measures the vector difference between.

  * two voltages
  * two or more similar electrical quantities
  * two current
  * none of above
  * The Right Answer: two or more similar electrical quantities

13. Thermal overload relays are used to protect the motor against over
current due to.

  * heavy load
  * over heat
  * Short Circuit
  * all of above
  * The Right Answer: all of above

14. Breaking capacity of the circuit breaker is usually expressed in.

  * Kilo-Ampere
  * MVA
  * KV
  * kW
  * The Right Answer: MVA

15. Which of the following circuit breakers produce least arc energy?

  * Air blast
  * Oil Circuit breaker
  * Minimum oil
  * None of above
  * The Right Answer: Air blast

16. Which of the following is not a part of the circuit breaker ?

  * conservator
  * Fixed and moving contacts
  * Explosion pot
  * Operating mechanism.
  * The Right Answer: conservator

17. A Merz-price protection is suitable for....

  * Transformer
  * Alternator
  * Motor
  * transmission line
  * The Right Answer: Alternator

18. Which relay is used for transformer protection?

  * Translay relay
  * differential relay
  * buchholz relay
  * none of above.
  * The Right Answer: buchholz relay

19. Which relay is used for feeders ?

  * Translay relay
  * differential relay
  * MHO realy
  * none of above
  * The Right Answer: Translay relay

20. The over-voltage surges in power systems may be caused by...

  * switching
  * lightning
  * resonance
  * all of above
  * The Right Answer: all of above

21. In a circuit breaker the current which exists at the instant of
contact separation is known as

  * breaking current
  * recovery current.
  * surge current.
  * all of above
  * The Right Answer: breaking current

22. Oil immersion of contacts is the method of

  * arc dispersion
  * de ionization
  * arc prevention
  * all of above
  * The Right Answer: arc dispersion

23. The arc voltage produced in the circuit breaker is always...

  * leading the arc current by 90°
  * lagging the arc current by 90° .
  * in phase with arc current
  * none of above
  * The Right Answer: in phase with arc current

24. Sparking occurs when a load is switched off because the circuit has

  * high capacitance
  * high inductance
  * high resistance.
  * all of above
  * The Right Answer: high inductance