psabits withanswers

8/3/2019 psabits withanswers

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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

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