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JNTU ONLINE EXAMINATIONS [Mid 2 -PSA]
1. A 1000 kVA transformer with 5%reactance will have a reactance of
10% at____1. 1000 kVA base2. 2000 kVA base3. 3000kVA base4. 4000 kVA
2. The p.u. impedance value of analternator corresponding to base
values of 13.2kV and 30MVA is0.2p.u. The p.u. value for the base
values 13.8kV and 50MVA is_______
1.
0.106 p.u.2. 0.206 p.u3. 0.306 p.u4. 0.318 p.u
3. A Transformer has reactance of 4%on a 20 MVA base. For 30 MVA
base reactance is________
1. 6%2. 2.66 %3. 9 %4. 2%
4. The p.u impedance of a line to a 50MVA. 132 kV base is 0.6. The p.uimpedance to a 100 MVA , 132 kV
base will be1. 0.32. 0.63. 1.24. 1.8
5. Base impedance of the power systemis given by
1.2.3.4.
6. If base values are 50 MVA and11kV, the base impedance is______ohms
1. 4.542. 0.223. 274. 1
7. If per unit impedance on 11kV baseis 9 ohms, the p.u impedance on33kV base will be ____ohms
1. 32. 813. 274. 1
8. The correct formula to convert actualimpedance Z ohms to p.u impedanceis
1.2.3.4.
9. In a _______ the components ofpower system are represented by
symbols and the interconnectionbetween them are shown by straight
lines.
1. Single line diagram2. Impedance diagram3. Reactance diagram4. Resistance diagram
10.The positive, negative and zerosequence impedances of a solidlygrounded system under steady state
condition always follow the relations
1. Z1>Z2>Z02. Z1
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12.In a balanced three phase system,negative and zero phase sequence
currents are
1. equal2. zero3.
different4. one
13.For a balanced 3-Phase system the______ is same as positive sequencereactance diagram
1. Single line diagram2. Impedance diagram3. Reactance diagram4. Resistance diagram
14.The per unit quantity is defined as1. Actual /Base2.
(Base) / Actual3. Base / (Actual-1)
4. Base / (Actual-2)15.The operator 'a' rotates the vector in
the anti clock wise direction by1. 9002. 12003. 18004. 3000
16.Which of the following is correct1. 1+a+a2 =02. a+2=13. 1+3=04. 1+2=0
17.Which of the following is correct1. 1+a+a2 =02. a+2=13. 1+3=04. 1+2=0
18.Which of the following is correct1. a2=0.5+j0.8662. a2=-0.5+j0.8663. a2=-0.5-j0.8664. a2=j0.866
19.The positive and negative sequenceimpedance of a transmission line are
1. Equal2. zero3. different4. one
20.The zero sequence impedance ofdifferent elements of power system
is generally1. Equal2. zero3.
different4. one
21.On the occurrence of theunsymmetrical fault which sequencecomponent is always more than the
negative sequence component1. Zero sequence2. positive sequence3. Zero sequence, positive
sequence4. one
22.The zero sequence impedance of anelement in a power system is
generally different from1. Positive sequence impedance2. negative sequence
impedance
3. Positive and negativesequence impedances
4. Positive sequence resistance23.If the percentage reactance of the
system up to the fault point is 20 %and the base kVA is 10000 then the
short circuit kVA is1. 10 MVA2. 20 MVA3. 50 MVA4. 60 MVA
24.The indicative of unsymmetrical inthe system can be
1. the presence of the negativesequence components
2. the presence of positivesequence components
3. the presence of zerosequence components
4. the presence of thenegative and zero sequence
components
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25.For an unbalanced three phasesystem
1. Z2=Z0=infinite2. Z1>Z2>Z03. Z1=Z2=Z0=04.
Z1>Z2
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1. 1:12. 1:23. 1:34. 3:1
37.For a synchronous machine withsolidly grounded neutral1. Z0Z13. Z1=Z2=Z04. Z0>Z2
38.For a synchronous machine withsolidly grounded neutral
1. a L-G fault is more severethan 3-phase fault
2. 3-phase fault is moresevere than L-G fault
3.
both L-G and 3-phase faultshave the same effect
4. 3-phase fault is less severethan L-G fault
39.A double line to ground fault ischaracterized as
1. symmetrical fault2. unsymmetrical fault3. symmetrical voltage4. symmetrical current
40.The method of symmetricalcomponents is used to analyze the
unsymmetrical faults, because1. Un balanced currents2. Un balanced voltages3. Un balanced powers4. Un balanced currents,
voltages and powers
41.The positive sequence voltage(Va1)for a particular fault is zero the
fault is1. LG2. LL3. LLG4. 3- phase
42.The positive sequence component ofvoltage at the point of fault is zerowhen it is
1. Three phase fault2. L-L fault
3. L-L-G fault4. L-G fault
43.The faults can be classified as_______
1. shunt faults2.
series faults3. shunt and series faults
4. open faults44.Shunt type of faults involves
___________ between the
conductors.1. power conductors2. conductors-to-ground3. short circuit4. power conductors,
conductors-to-ground and
short circuit45.Series type of faults is characterizedby decrease in current and ,increase in voltage.
46.Shunt type of faults can be classifiedas _______
1. L-L2. L-L-G3. L-G4. L-L, L-L-G and L-G
47.The example for balanced fault is________.
1. L-L2. L-L-G3. L-G4. 3-;.
48.Series type of faults can be classifiedas _______.
1. Opening of line2. L-L fault3. L-L-G fault4. L-G fault
49.For fault analysis of large powersystems, the most suitable method
isBus impedance method1. Bus admittance method2. Bus current method3. Bus impedance method4. Bus voltage method
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50.The three sequence equations usingthe sequence generated voltages and
the sequence impedances are
1.2.3.4.5.
51.The voltage of the neutral is given byVn=
1. 3Iao Zn2. - 3Iao Zn3. Iao Z4. Iao Zn
52.In case of L-G fault, the threesequence networks are connected in
1. Series2. parallel3. shunt4. series and parallel
53.The analysis of unsymmetrical faultsby symmetrical components method
requires the determination of1. Sequence voltages2. Sequence currents3. Sequence powers4. Sequence voltages ,
Sequence currents and
Sequence powers54.The positive and negative
components of currents through theneutral are
1. zero2. 13. 24. 1.5
55.In case of L-G fault, the expressionfor the current Ia1=
1.2.3.
4.56.The negative and zero sequence
voltages are maximum at ______and
minimum at _____1. fault point , fault point2. neutral point , neutral bus3. fault point , fault bus4. fault point , neutral bus
57.The receiving end voltage is equal tosending end voltage for a loss lessline condition for maximum power is
1. x = 1.732R2. x = 1.414R3. x = 1.732/R4. x = 1.732+R
58.If the torque angle increases withoutlimit, the system is ___
1. stable2. unstable3. marginally stable4. oscillates
59.For L-L fault, the positive-sequenceand negative-sequence networks areconnected in
1. same2. parallel3. opposition4. series
60.In case of L-G fault, the expressionfor the fault current is given by If=
1. 4 Ia12. 2 Ia13. Ia14. 3 Ia1
61.For L-L fault, the zero-sequencecomponent of current is
1. 12. zero3. 1.54. 0.3
62.For L-L fault, the positive-sequencecomponent of voltage is equal to thenegative-sequence component of
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1. voltage2. current3. impedance4. resistance
63.Fast operating CBs improves1.
Steady state stability2. Transient stability
3. Steady state and transientstability
4. load flows64.The angle between relative position
of rotor axis and the stator magnetic
field axis is1. Load angle2. Torque angle3. Load angle or Torque
angle4. Steady state stability65.In a two-machine system , ______
grounding at the sending end and
____ grounding at the receiving endis preferable
1. Resistance, Reactance2. Reactance, Resistance3. Resistance, Resistance4. Reactance, Reactance
66.If the maximum power =50MW, theelectrical power out power for a
torque angle of 600 is _____1. 43.7MW2. 43.4MW3. 43.6MW4. 43.3MW
67.Maximum Steady state limit ofpower system operates with
1.
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75.In terms of system stability point ofview, the star point of the motor is
____ grounded
1.
Reactance2. Reactance3. impedance4. admittance
76.From the stability point of view, thestar point of the generator is ____grounded
1. Reactance2. Reactance3. Resistance& Resistance4. Reactance or Reactance
77.A 12 pole, 300 rpm, 11kV, 3-phasealternator has a stored energy of
5400MJ. Its1. 42. 93. 104. 0.1
78.Two alternator with stored energiesof 1200MJ and 1000MJ are workingis Parallel. Its equivalent inertia
constant for the base 100MVA is (inMJ/MVA)
1. 1202. 2203. 124. 22
79.If the maximum power =50.2MW,The electrical power out power for a
torque angle of 660 is _____1. 43.7MW2. 43.4MW3. 45.86MW4. 15MW
80.Switching of asynchronous loadseffect
1. voltage stability2. frequency stability3. power system stability4. voltage and frequency
stability
81.Loss of synchronism leads to1. system stability2. system unstable3. oscillatory4. marginally stable
82.When a system reaches stable statefollowed by a large disturbance it isreferred to as
1. Steady state stability2. Transient stability3. power system stability4. un stable
83.Classical approach of power systemstability means
1. Simplified model ofsynchronous machine
2.
no voltage regulators3. no dampers4. no booster
84.Which of the following is a smalldisturbance?
1. sudden increase in load2. loss of generation3. switching of transmission
line when initial power
flow is small
4. sudden drop of load85.When a system reaches stable state
followed by a small disturbance it isreferred to as
1. Steady state stability2. Transient stability3. power system stability4. dynamic stability
86.Simplified model of synchronousgenerator is represented by
1. voltage source2. impedance3. voltage source and
impedance in parallel
4. voltage source andimpedance in series
87.Power angle curve shows relationbetween
1. Pm Vs Pe2. PmVs
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3. PeVs 4. PaVs
88.The steady state stability can beimproved by
1. reducing reactance of line2.
increasing excitation3. selecting low impedancemachines
4. reducing reactance of line,increasing excitation and
selecting low impedance
machines
89.For stability the change in w.r.ttime i.e., d/dt=
1. infinite2. one3.
zero4. Pm-Pe
90..When a sudden and largedisturbance occurs, does not
change if rotor runs at1. < synchronous speed2. > synchronous speed3. synchronous speed4. max speed
91.If the input of the generator is morethan the output the torque angle will
1. reduce2. increase3. be constant4. exponential
92.If the input of the motor is more thanthe output the torque angle will
1. reduce2. increase3. be constant4. exponential
93.The loss of synchronism of machineresults variation in
1. frequency2. voltage3. power factor4. frequency and voltage
94.A 12 pole, 3000 rpm, 11kV, 3-phasealternator has a stored energy of
5400MJ. Its inertia is MJ-sec/elec.degrees is
1. 42. 93. 104.
0.195.Equal area criteria can be applicable
to
1. multi machine system2. One machine connected to
infinite bus3. One machine connected to
multi bus system4. One machine connected to
multi machine system96.If the receiving end voltage is equal
to sending end voltage for a loss lessline, the condition for maximum
power is
1.2.3. X=R4.
97.If the torque angle increases withoutlimit the system is
1.
Stable2. unstable3. oscillatory4. marginally stable
98.The solution of swing equation canbe obtained by_____ method
1. point by point2. equal area criterion3. Newton4. gauss method
99.The solution of swing equation givesa graph ______ Vs____1. power , load angle
2. Load angle, power3. Torque angle, time4. time, torque angle
100. The limit of steady state is___ transient stability limit
1. more than
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2. less than3. equal to4. greater than or equal to
101. The addition of synchronousmotor (over excited) at the receiving
end of a line improves ____ stability1. steady state stability2. dynamic stability3. transient stability4. dynamic and transient
102. Compared to shorttransmission line, a long
transmission line with sameoperating voltage will have less
steady state stability limit because____ is high
1.
reactance2. resistance3. current4. admittance
103. A salient pole machine hasrelatively high stability limit during
steady state stability limit because___
1. synchronous powercoefficient is high
2. synchronous powercoefficient is low
3. synchronous powercoefficient constant
4. synchronous powercoefficient is zero
104. The solution of the swingequation can be obtained by ______
method
1. step-step2. equal area3. step-step and equal area4. Newton
105. Fast acting voltage regulatorsincludes____ stability
1. dynamic2. steady state3. transient4. voltage
106. The inertia constant of turboalternator is _____ than hydro
generators
1. less2. more3.
equal4. greater than equal
107. The series capacitor improves1. dynamic stability2. steady state stability3. transient stability4. dynamic and transient
108. If the actual clearing angle isgreater than the critical value, the
system is ____ ,1. Marginally stable2.
Unstable3. Stable
4. Oscillatory109. In point by point method, the
computed swing curve approachesthe true curve, only when the time
interval is------------1. Decreased2. Increased3. Constant4. zero
110. ----- machine stability willhave more than one swing equation.This statement is
1. Multi2. single3. single machine connected to
infinite
4. Infinite111. The swing equation can be
solved by _____ method1. Runge-kutta2. Modified Euler's3. Both Runge-kutta and
Modified Euler's4. Newton
112. The solution of the swingequation gives a graph ______ Vs
_______1. Time Vs torque angle
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2. torque angle Vs angle3. torque angle Vs time4. power Vs time
113. The limit of transient stabilityis _____ the steady state limit { B}
1.
Greater than2. less than3. equal to4. greater than or equal
114. The solution of point by pointmethod adopted to solve the swingequation for
1. Power angle2. critical clearing time3. clearing angle4. clearing time
115.
Equal area criterion can beapplicable to
1. three machine system2. One machine system
connected to infinite bus3. four machine system4. five machine system
116. Multi machine stability willhave ---- than one swing equation.This statement is
1. more2. less3. equal4. infinite
117. Which one of the following isthe swing equation
1. (H/f) (d2/dt2) = Pm-Pe2. (H/f) / (d2/dt2) = Pm+Pe3. (H/f) / (d2/dt2) = PmPe4. (f/H) / (d2/dt2) = Pm-Pe
118. The solution of swingequation gives the graph __ vs __
1. Torque angle, Time2. Time, Torque angle3. Torque angle, Voltage4. Time, Voltage
119. The swing equation describes1. rotation of rotor2. rotating magnetic field3. rotor oscillations
4. rotor speed120. Transient stability of a large
scale power system can be improvedby
1. Increasing system voltage2.
Decreasing system voltage3. increasing resistance
4. increasing reactance121. The swing equation is
1. Md2/dt22. Md2/dt2=Tm-Te3. Md2/dt2=Pm-Pe4. Md2t/d2
122. The swing equation is used todetermine
1. Steady state stability2. Transient stability3. steady state & transient4. dynamic
123. The critical clearing angle ofa SMIB through two transmissionlines can be determined by using
1. single power angle curve2. two power angle curves3. 3 power angle curves4. Pm vs Pe curve
124. Auto reclosing is possible incase of
1. short period faults2. semi permanent faults3. permanent faults4. short period faults & semi
permanent faults
125. The equal area criterion isapplicable only to
1. SMIB2. two machine system3. multi machine system4. SMIB & two machinesystem
126. The swing curve providesinformation of
1. stability2. faulted conditions3. stability & fault conditions4. only stability
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127. The transient stability isdetermined by
1. analytical method2. step by step method3. equal area criterion4.
step by step method orequal area criterion
128. In the equal area criterion ifA2
1. stable2. unstable3. critically stable4. stable or unstable
129. The numerical methods areused to simulate
1. power system stability2.
faulted conditions3. stability & fault conditions
4. only stability130. An alternator is capable of
facing the problem of Hunting. It has1. good steady state stability2. good transient stability3. good dynamic stability4. load speed characteristics
which are dropping
131. The solution of point by pointmethod adopted to solve swing
equation gives
1. critical clearing time2. clearing time3. clearing angle4. clearing angle & time
132. The stability of transmissionline can be improved by using
1. lightning arrestors2. quick acting CB's3. fuses4. slow acting CB's
133. The failure of excitationsystem affects
1. steady state stability2. transient stability3. steady state and transient
stabilities4. dynamic
134. Normally power systemoperates
1.
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1. unstable operation2. stable operation3. marginally stable4. critically stable
141. The auto recloser unit in amodern CB improves ______stability limit
1. transient2. steady state3. dynamic4. steady state & dynamic
142. A generator is connected to asynchronous motor. From stabilitypoint of view the generator neutral is
___ grounded and motor terminal is_____ grounded
1.
resistance, reactance2. reactance, resistanc3. resistance, resistance4. reactance, reactance
143. Two synchronous machineshaving inertia constants M1 and M2
are swing together. The inertiaconstant of the combination is
1.2.3.4.
144. 100MW when transferred asa maximum power, when line
reactance is 1 ohm, the faultincreases the reactance to 4 ohms>
The new value of maximum power is
1. 25MW2. 50 MW3. 75 MW4. 100 MW
145. If two lines in parallel,working as inter connectors, one ofthem switches off the new value of
steady state power will _______because the line transfer reactance
is_____
1. decreases, high
2. decrease, low3. increase, high4. increase, low
146. It is required to improvetransient stability of power system.
Pick out wrong method1. Use auto reclosing fastacting CBs
2. use AVR3. operate heavy machines if
possible
4. reduce reactance147. A synchronous motor of
negligible resistance receiving 25%
of power that it is capable ofreceiving from an infinite bus. If the
load is suddenly doubled, the newpower angle is ____ degrees
1. 3002. 6003. 9004. 1200
148. If the torque angle isincreases infinitely, the system will
show
1. unstable operation2. stable operation3. marginally stable4. critically stable
149. A synchronous motor ofnegligible resistance receiving 25%of power that it is capable of
receiving from an infinite bus. If theload is suddenly doubled, the new
power angle is ____ degrees
1. 3002. 6003. 9004. 1200