57. Which of the following carrier frequency is used in a carrier current protection scheme?
A. 500 kHz to 5lcHz
B. 5 kHz to 50 kHz
C. 50 kHz to 500 kHz
D. 500 kHz to 5 MHz

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58. The problem of stability occurs in
A. dc lines only
B. ac lines only
C. both dc and ac lines
D. none of these

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59. Which of the following condition causes transient iqrstability in power system?
A. short circuit
B. switchng operations on the line
C. loss of excitation in a generator
D. all of these

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60. Between the power house and consumer, there are usually a number of transformation and switching stations. These are called
A. transformer stations
B. intermediate stations
C. substations
D. switch gears

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61. The condition necessary for transient stability is
A. j58 2(Ps ? Pe) d&0 o
B. 12 2(Ps ? P e)d6=0
C.2(Ps ? Pe )20
D.r s e d=0

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62. Modern trend in rail electrification in India is to use which of the following supply system
A. 25 kV, 50 Hz
B. 15 kV, 50 Hz
C. 6 kV, 50 Hz
D. 6 kV, dc

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63. Tractive force Fa needed to accelerate a train of effective mass M for providing acceleration a is given by
A. Fa = 277.8 Ma (N)
B. Fa = 277.8 Ma (kg)
C. Fa = Ma (N)
D. Fa = Ma (kg)

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