51. Series capacitive compensation in EHV transmission lines is used to
(a) reduce the line loading
(b) improve the stability of the system
(c) reduce the voltage profile
(d) improve the protection of the line
Ans: b
52. A lossless radial tranemission line with surge impedance loading
(a) takes negative VAr at sending end and zero VAr at receiving end
(b) takes positive VAr at sending end and zero VAr at receiving end
(c) has flat voltage profile and unity power factor at all points along it
(d) has sending end voltage higher than receiving end voltage and unity power factor at sending end
Ans: a
53. The X:R ratio of 220 kV line as compared to 400 kV line is
(a) greater
(b) smaller
(c) equal
(d) it could be anything
Ans: b
54. If a line is 100 % series compensated it may result into series resonance at power frequency of
(a) 50 Hz
(c) 150 Hz
(b) 100 Hz
(d) none of the above
Ans: a
55. A 60 Hz, 320 km loesless line has Bending end voltage 1.0 p.u, The receiving end voltage on no load is
(a) 1.1 p.u.
(b) 1.088 p.u.
(c) 1.116 p.u.
(d) none of the above
Ans: b
56. With 100 % series compensation of line.
(a) the circuit is series resonant at power frequency
(b) low transient voltage
(c) high transient current
(d) both (a) and (c)
Ans: d
57. For certain geometry and operating voltage of the uncompensated transmission line, the ratio of power transfer capability to the surge inpedance loading with increase in length
(a) increases
(b) remains unchanged
(c) decreases
(d) uncertain
Ans: c
58. The effect of series capacitance compensation is
(a) to decrease the virtual surge impedance
(b) to decrease the effective length of the line
(c) to increase virtual surge impedance loading
(d) all of the above
Ans: d
59. For a long uncompensatedline the limit to the line loading ill governed by
(a) thermal limit
(b) voltage drop
(c) stability limit
(d) corona loss
Ans: c
60. For any fixed degree of inductive shunt compensation, additional series capacitive compensation
(a) increase the effective length of line
(b) increase virtual surge impedance line
(c) decrease virtual surge impedance loading of the line
(d) none of the above
Ans: d
61. With 100 % inductive shunt compensation, the voltage profile is flat for
(a) 100 % loading of line
(b) 50 % loading of line
(c) zero loading of line
(d) none of the above
Ans: c
62. A loss less line terminated with its surge impedance has
(a) flat voltage profile
(b) transmission line angle is greater than actual length of line
(c) transmission line agnle is less than the actual length
(d) both (a) and (b) above
Ans: a
63. For reducing tower footing resistance it is better to Use
(a) chemical and ground rods only
(b) chemical and counterpoise only
(c) ground rod and counterpoise only
(d) chemical, ground rods and counterpoise
Ans: c
64. An RLC series. circuit remains predominantly inductive
(a) at resonance frequency
(b) below resonance frequency
(c) above resonance frequency
(d) at the lower half power frequency
Ans: c
65. The corona loss on a particular system at 50 Hz is 1 kw/phase per km. The corona loss on the same system with supply frequency 25 Hz will be
(a) 1 kW/phase/km
(b) 0.5 kW/phase/km
(c) 0.667 kW/phase/km
(d) none of the above
Ans: c
66. A voltage of 1000 kV is applied to an overhead line with its receiving end open. If the surge impedance of the line is 500 ohm, then the total surge power in the line
(a) 2000 MW
(b) 500 MW
(c) 2 MW
(d) 0.5 MW
Ans: a
67. The main criterion for selection of the size of a distribution for a radial distribution system is
(a) voltage drop
(b) corona loss
(c) temperature rise
(d) capital cost
Ans: a
68. If an induction machine is run at above synchromous speed, it acts as
(a) a synchronous motor
(b) an indcution generator
(c) an inductor motor
(d) none of the above
Ans: b
69. The low voltage winding of a 400/230 V, 1-phase, 50 Hz transformer is to be connected to a 25 Hz, the supply voltage should be
(a) 230 V
(b) 460 V
(c) 115 V
(d) 65 V
Ans: c
70. Corona losses are minimized when
(a) conductors size is reduced
(b) smooth conductor is reduced
(c) sharp points are provided in the line hardware
(d) current density in conductors is reduced
Ans: b
71. The order of the sub-harmonic during SSR for 50 Hz nornal frequency is
(a) 25 Hz
(b) 16 2/3 Hz
(c) 10 HZ
(d) none of the above
Ans: d
72. The non-uniform distribution of voltage across the units in a string of suspention type insulators is due to
(a) unequal self-capacitance of the units
(b) non-uniform distance of separation of the units from the tower body
(c) the existence of stray capacitance between the metallic junctions of the units and the tower body
(d) non-uniform distance between the cross-arm and the units
Ans: c
73. Whenever the conductors are dead-ended of there is a change in the direction of transmission line, the insulator. used are of the
(a) pin type
(b) suspension type
(c) strain type
(d) shackle type
Ans: c
74. The time taken for a surge to travel a 600 km long overhead transmission line is
(a) 6s
(b) 1s
(c) 0.02s
(d) 0.002s
Ans: d
75. The function of the earth wire in an extra high voltage line is to
(a) prevent earth fault
(b) provide a safety measure for any high-flying object
(c) provide a shield to the phase con-ductors from direct lightning stroke
(d) provide mechanical strength to the towers
Ans: c