Switchgear Protections

31. If the fault occurs near the impedance relay, the VII ratio will be

1. constant for all distances
2. lower than that of if fault occurs away from the relay
3. higher than that of if fault occurs away from the relay
4. none of the above

View answer

32. In a circuit breaker the basic problem is to

1. maintain the arc
2. extinguish the arc
3. transmit large power
4. emit the ionizing electrons

View answer

33. In order that current should flow without causing excessive heating or voltage drop, the relay contacts should

1. have low contact resistance
2. be clean and smooth
3. be of sufficient size and proper shape
4. have all above properties

View answer

34. In Railway applications _________ circuit breaker is used.

1. SFe
2. bulk oil
3. minimum oil
4. air break

View answer

35. Induction cup relay is operated due to changes in

1. current
2. voltage
3. impedance
4. all of the above

View answer

36. Insulation resistance of high voltage circuit breakers is more than

1. 1 mega ohms
2. 10 mega ohms
3. 100 mega ohms
4. 500 mega ohms

View answer

37. Interruption of large currents by relay requires

1. arc suppressing blow out coils
2. wide separation of the opened contacts
3. high speed opening of contacts
4. all of the above

View answer

38. Ionization in circuit breaker is facilitated by

1. high temperature
2. increase of mean free path
3. increasing field strength
4. all of the above

View answer

39. Large internal faults are protected by

1. merz price percentage differential protection
2. mho and ohm relays
3. horn gaps and temperature relays
4. earth fault and positive sequence relays

View answer

40. Magnetic circuit breaker has _________ trip action.

1. delayed
2. instantaneous
3. both of the above
4. none of the above

View answer