Switchgear and Protection : [ ISRO,DRDO,DMRC,SAIL, ODNANCE, HAL, WBSEDCL, RAILWAY & Others competitive]-mcq of switchgear and protections 

1.Outdoor switchgear is generally used for voltage beyond

A. 11 KV
B. 33 KV
C. 66 KV
D. 132 KV

Ans. C

2.The least expensive protection for over current in low-voltage system is

A. Rewirable fuse
B. Isolator
C. Circuit breaker
D. Air-break switch

Ans. A

3.Purpose of backup protection is

A. To increase the speed
B. To increase a reach
C. To leave no blind spot
D. To guard against failure of primary

Ans. D

4.We do not require any protection against prime mover failure in case of

A. Turbo generator sets
B. Hydro generator sets
C. Diesel engine driven alternators
D. Back pressure turbo generators

Ans. A

5.For the protection of stator winding of an alternate against internal fault involving ground the relay used is a

A. Biased differential relay
B. Directional over-current relay
C. Plain impedance relay
D. Buchholz relay

Ans. A

6.For the protection of a large squirrel cage induction motor against single phase normally

A. An over-current relay is used
B. Differential relay is used
C. Directional relay is used
D. Negative sequence current sensitive relay is used

Ans. D

7.The most commonly used method for the protection of three phase feeder is

A. Time graded protection
B. Differential protection
C. Reverse power protection
D. None of the above

Ans. B

8.Which is the pilotless protection method for feeder line ?

A. Differential protection
B. Carrier current protection
C. Time credit protection
D. None of the above

Ans. B

9.Time graded protection of a radial feeder can be achieved by using

A. Definite time relay
B. Inverse time relay
C. Both definite and inverse time relays
D. None of the above

Ans. C

10.  Pilot-wire protection scheme is the most economical and provides high speed relaying for

A. Short length of lines upto 15 km
B. Medium length of lives up to 60 km
C. Long length of lines up to 200 km
D. All of the above

Ans. A

 

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