Power System Protection Objective Questions Answers

1. Isolators are used for disconnecting a circuit when:
a) Line is energised
b) Line is on full load
c) Line carries no current
d) Can be operated under any condition

C

2. Under-voltage relay is mostly used for:
a) Transformer protection
b) Bus-bar protection
c) Motor protection
d) Feeder protection

C

3. Earth fault relays are:
a) Directional relay
b) Non-directional relay
c) Short operate time relay
d) Under voltage relay

A

4. Differential relays are used for the protection of equipments against:
a) Internal faults
b) Over-current
c) Reverse current
d) Reverse power

A

5. Admittance relay is:
a) Non-directional relay
b) Directional relay
c) Differential relay
d) None of the above

B

6. The torque developed in Induction type relay is:
a) Directly proportional to the current
b) Directly proportional to the square of the current
c) Directly proportional to square root of the current
d) Inversely proportional to the current

B

7. Buchholz relay is a:
a) Oil actuating relay
b) Current actuating relay
c) Gas actuating relay
d) Oil temperature-actuating relay

C

8. The relay with inverse time characteristics will operate within:
a) 10 msec
b) 5 to 10 sec
c) 10 to 20 sec
d) above 25 sec

B

9. The operation speed of a relay depends on:
a) Rate of flux buildup
b) Armature core air gap
c) Spring tension
d) All the above

D

10. Which of the following relays has inherent directional characteristics:
a) Mho relay
b) Impedance relay
c) Reactance relay
d) Distance relay

A