50. Buchholz relays are used for transformers of ratings above
A. 100 kV
B. 200 kV
C. 500 kV
D. 41000 kV

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51. The power factor of the arc in a circuit breaker is
A. zero leading
B. zero lagging
C. unity
D. any value from zero to unity

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52. A high speed circuit breaker can complete its operation in
A. 2 to 3 cycles
B. 3 to 8 cycles
C. 6 to 12 cycles
D. 10 to 20 cycles

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53. Plug setting of a relay can be altered by varying
A. number of ampere-turns
B. air gap of magnetic path
C. adjustable back up stop
D. none of these

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54. Various power system faults in increasing order of severity are
A. P.U. Xeq
B. Base MVA x P.U. Xeq Base MVA
C. (P.U. Xeq)2
D. none of these

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55. Which of following are used to reduce short circuit fault currents
A. reactors
B. resistors
C. capacitors
D. parallel combination of all these

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56. Pilot wire protection is basically used for the protection of
A. transmission lines
B. alternators
C. switch gears
D. transformers

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