MCQ on Switchgear and Protection – 4

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 1. Arc in a circuit breaker is interrupted at
(A) zero current.
(B) maximum current.
(C) minimum voltage.
(D) maximum voltage.

 2. Induction cup relay operates when there is changes in
(A) voltage.
(B) current.
(C) impedance.
(D) all of the above.

 3. The arcing contacts in a circuit breaker are generally made of
(A) lead tin alloy.
(B) copper tungsten alloy.
(C) electrolytic copper.
(D) aluminium alloy.

 4. The operating time of a fuse is nearly
(A) 1 sec.
(B) 0.5 sec.
(C) 1.8 sec.
(D) 0.002 sec.

 5. The operating time of a circuit breaker is nearly
(A) 0.004 sec.
(B) 1.04 sec.
(C) 0.02 sec.
(D) 0.2 sec.

 6. The application of a Volt/Hertz relay is in
(A) over excited protection.
(B) backup protection.
(C) over voltage protection.
(D) anti motoring protection.

 7. The shape of the disc of an induction disc relay is
(A) square.
(B) spiral.
(C) circular.
(D) elliptical.

 8. The breaking capacity of a fuse is
(A) zero.
(B) small.
(C) high.
(D) infinite.

 9. In a thermal relay, a bi-metal strip consists of two metal strips having different
(A) thermal conductivity.
(B) efficient of expansion.
(C) specific heat.
(D) all of the above.

 10. Differential relay are used to protect the equipment against
(A) external faults.
(B) over current.
(C) reverse current .
(D) internal faults.

 11. Distance Protection Scheme is used for the protection of
(A) motor.
(B) transformer.
(C) alternator.
(D) overhead line.

 12. In transmission lines, the capacitance as compared to inductance is
(A) very small.
(B) very large .
(C) equal.
(D) double.

 13. Shunt compensation in an EHV line is used to improve
(A) stability and fault level.
(B) fault level and voltage profile.
(C) voltage profile and stability.
(D) stability, fault level and voltage profile.

 14. Thermal relays are used for protection of motor against over-current owing to
(A) short-circuits.
(B) earth fault.
(C) heavy load.
(D) All of the above.

 15. Which of the following circuit breaker preferred for high voltage and low current interruption ?
(A) oil CB.
(B) Vacuum CB.
(C) Air blast CB.
(D) Any of these.

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