76. A long overhead transmission line is terminated by its characteristic impedance. Under this operating condition, the ratio of the voltage to the current at different points along the line will
(a) progressively increase from the sending-end to the receiving end
(b) progresively increase from the receiving end to the sending-end
(c) remain the same at the two ends, but be higher between the two ends being maximumat the centre of the line
(d) remain the same at all points
Ans: b
77. For a transmission line with negligible losses, the lagging reactive power (VAR) delivered at Ihe receiving end, for a given receiving end voltage, is directly proportional to the
(a) square of the line voltage drop
(b) line voltage drop
(c) line inductive reactance
(d) line capacitive reactance
Ans: b
78. Corona loss can be reduced by the use of hollow conductors because
(a) the current density is reduced
(b) the eddy current in the conductor is eliminated
(c) for a given cross-section, the radius of the conductor is increased
(d) of better ventilation in the conductor
Ans: d
79. The insulation of modern EHV lines is designed based on
(a) the lightning voltage
(b) corona
(c) radio interface
(d) switching voltage
Ans: d
80. Shunt conapenBation in an EHV line is “Bed
(a) improve stability
(b) reduce fault level
(c) improve the voltage profile
(d) subsitute for synchronous phase modifier
Ans: d
81. In a 3-core extra-high voltage cable, a metallic screen around each core¬i,..ulation i. provided to
(a) facilitate heat dissipation
(b) give mechanical strength
(c) obtain radial electric stress
(d) obtain longtiudinal electric stress
Ans: c
82. The aingle pbase line of 280 V and 3 pha.e line of 400 V which feed different domestic circuit. and induetrial loade represent
(a) primary distribution
(b) secondary distribution
(c) secondary transmission
(d) none of the above
Ans: b
83. The transmission line feeding power on either side of the main transmission line i. called
(a) Secondary distribution
(b) Secondary transmission
(c) Primary transmission
(d) Primary distribution
Ans: b
84. Series capacitive compensation on 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: d
85. At a particular unbalanced node, the real powers specified are Leaving the node : 20 Mw, 25 Mw, Entering the node: 60 Mw, 30 MW. The balance power will be
(a) 30 MW leaving the node
(b) 45 MW leaving the node
(c) 45 MW entering the node
(d) 22.5MW entering the node and 22.5 MW leaving the node
Ans: b
86. When a d.c source is switched is purely inductive, the current response is
(a) an exponentially rising curve
(b) an exponentially decaying curve
(c) a straight line passing through the origin
(d) a straight line off-set from the origin
Ans: c
87. If transformer frequency is changed from 60 Hz, to 60 Hz the ratio of eddy current loss 60 Hz to 50 Hz, at constant voltage will be
(a) 5/6
(b) 25/36
(c) 6/5
(d) 1.0
Ans: d
88. In load flow analysis, the load connected at a bUs is represented as
(a) constant current drawn from the bus
(b) constant impedance connected at the bus
(c) voltage and frequency dependent source at the bus
(d) constant real and reactive drawn from the bus
Ans: d
89. If the reference bUB is changed in two load flow runs with same Bystena data and power obtained for reference bur taken a. specified P and Q in the latter run
(a) the system losses will be unchanged but complex bus voltage will change
(b) the system losses will be changed but complex bus voltages remain unchanged
(c) the system losses as well be as complex bus voltage will change
(d) the system losses as well be as complex bus voltage will unchange
Ans: a
90. A square matrix is called singular if its
(a) determina is unity
(b) determinant is zero
(c) determinant is infinity
(d) rank is unity
Ans: b
91. Gauss-Seidel iterative method can be used for solving a set of
(a) linear differential equations only
(b) linear algebraic equation only
(c) both linear and nonlinear algebraic equations
(d) both linear and nonlinear differential equations
Ans: b
92. Pure inductive circuit takes power (reactive) from the a.c. line when
(a) both applied voltage and current rise
(b) both applied voltage anti current decrease
(c) applied voltage decreases but current Increases
(d) none of these
Ans: b
93. An alternator has a phase sequence of RYB for itB phase voltage. In case offield current is reversed, the phase sequence will become
(a) RBY
(b) RYB
(c) YRB
(d) none of these
Ans: b
94. An alternator has a phase sequence of RYB for its phase voltage. In case the direetior of rotation of alternator is reversed, the phase sequence will become
(a) RBY
(b) RYB
(c) YRB
(d) none of these
Ans: a
95. A synchronous generator connected to an infinite bUB delivers power at a lag p.r. If its excitation is increased
(a) the terminal voltage increases
(b) voltage angle 8 increases
(c) current delivered increases
(d) all of the above
Ans: c
96. A synchronous motor connected to an infinite bUB takes power at a lag p.f. If its excitation is increased
(a) the terminal voltage increases
(b) the load angle increases
(c) the p.f. of motor increases
(d) all of the above
Ans: c
97. A star-conneted 440 V, 50 Hz alternator has per phase synchronous reactance of 10 n. It supplies a bal anced capacitive load current of 20 A, as shown in per phase equivalent circuit of the given figure. It is desirable to have zero voltage regulation. The load power factor should be
(a) 0.82
(b) 0.47
(c) 0.39
(d) 0.92
Ans: a
98. A 10k VA, 400 V/200 V single phase transformer with 10 % impedance draws a steady short circuit line current of
(a) 50 A
(b) 150 A
(c) 250 A
(d) 350 A
Ans: b
99. The percentage resistance and percentage reactance of a 10 kVA, 400 V/200 V, 3-phase transformer are 2% and 10% respectively. If the constant losses in the machine are 1 %, the maximum possible percentage efficiency of the transformer is
(a) 98.32
(b) 97.25
(c) 96.85
(d) 96.12
Ans: c
100. The voltage of CI generator and an infinite bus are given as O.92LIO 0 and 1.0L’O 0 respectively. The active power will flow from
(a) generator to infinite bus
(b) infinite bus to generator
(c) the data is insufficient to judge
(d) none of the above
Ans: a
101. In case ora 3 phase short circuit in a system the power fed into the system is
(a) mostly reactive
(b) mostly active
(c) active and reactive both equal
(d) reactive only
Ans: a
102. With the help of a reactive compensator it is possible to have
(u) constant voltage opei ation only
(b) unity p.f. operation only
(c) both constant voltage and unity p.f.
(d) either constant voltage or unity p.f.
Ans: d
103. For a long uncompensated line the limit to the line loading is governed by
(a) thermal limit
(b) voltage drop
(c) stability limit
(d) corona loss
Ans: c
104. A shunt reactor at 100 MVAr is operated at 98% of its rated voltage and at 96% of its rated frequency. The reactive power absorbed by the reactor is
(a) 98 MVAr
(b) 104.02 MVAr
(c) 96.04 MVAr
(d) 100.04 MVAr
Ans: d
105. A 100 kVA transformer has 4% impedance and 50 k VA transformer has 3% impedance when they are operated in parallel, which 6 transformer will reacb full load first
(a) 3%
(b) 4%
(c) data is insufficient
(d) none of the above
Ans: a