Switchgear Protections

41. On which of the following effects of electric current a fuse operates?

1. Photoelectric effect
2. Electrostatic effect
3. Heating effect
4. Magnetic effect

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42. On which of the following routine tests are conducted?

1. Oil circuit breakers
2. Air blast circuit breakers
3. Minimum oil circuit breakers
4. All of the above

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43. Over voltage protection is recommended for

1. hydro-electric generators
2. steam turbine generators
3. gas turbine generators
4. all of the above

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44. Overfluxing protection is recommended for

1. distribution transformer
2. generator transformer of the power plant
3. auto-transformer of the power plant
4. station transformer of the power plant

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45. Overheating of relay contacts or contact born out is due to

1. slow making and breaking of load circuit contacts
2. foreign matter on the contact surface
3. too low contact pressure
4. all of the above

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46. Overload relays are of __________ type.

1. induction
2. solid state
3. thermal
4. electromagnetic
5. all above

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47. Protection by fuses is generally not used beyond

1. 20 A
2. 50 A
3. 100 A
4. 200 A

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48. Protective relays are devices that detect abnormal conditions in electrical circuits by measuring

1. current during abnormal condition
2. voltage during abnormal condition
3. constantly the electrical quantities which differ during normal and abnormal conditions
4. none of the above

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49. relay is preferred for phase fault on short transmission line.

1. Induction type
2. Reactance
3. Impedance
4. None of the above

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50. Relays can be designed to respond to changes in

1. resistance, reactance or impedance
2. voltage and current
3. light intensity
4. temperature
5. all above

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