Category: Power Systems Objective Questions

250+ TOP MCQs on Inductance of a Single-Phase Two-Wire Line – 1 and Answers

Power Systems Multiple Choice Questions on “Inductance of a Single-Phase Two-Wire Line – 1”.

1. Effect of earth is considered insignificant while calculating the inductance of a single phase transmission line.
A. True
B. False

Answer: A
Clarification: The earth’s magnetic symmetry does not affect the inductance of the line.

2. Effect of earth’s presence on the magnetic field geometry is _________________
A. significant
B. insignificant
C. cannot be said
D. none of the mentioned

Answer: A
Clarification: This is because the relative permeability of earth is about the same as that of air and its electrical conductivity is relatively small.

3. The inductance of the transmission line is do not contain effect of earth electric field geometry while the capacitances contain.
A. True
B. False

Answer: A
Clarification: It is true as the earth’s magnetic field symmetry is insignificant to the inductance while the electric field symmetry is.

4. The end effect information is included in the inductance of a transmission line.
A. True
B. False

Answer: B
Clarification: Since TL is infinitely long, the end effects are ignored and they are not a part of the inductance formula.

5. The number of the strands included in the stranded cables while implementing a similar cable equivalent of single strand should be ________
A. 3x2-3x+1
B. 2x2-3x+1
C. 3x2-2x+1
D. 3x2-x+1

Answer: A
Clarification: It is 3x2-3x+1.

6. The overall diameter of a stranded conductor if ‘x’ is the number of layers and each layer has a diameter ‘d’ will be
A. (2x-1)d
B. (3x-1)d
C. (6x-3)d
D. (2x+1)d

Answer: A
Clarification: It is given by (2x-1)d.

7. _______ conductors are the latest trend of the extra high voltage lines.
A. Bundled
B. Parallel
C. ACSR
D. Bundled or ACSR

Answer: A
Clarification: The bundled ACSR conductors have corona free characteristics and they have good tensile strength.

8. A 10 MVA, 11 kV alternator has positive, negative and zero sequence reactance of 25%, 40%,10% respectively. The resistance that must be placed in the neutral such that zero sequence of fault current for a single phase to ground fault will not exceed the rated line current in ohms is
A. 2.66 Ω
B. 1.66 Ω
C. 12.1 Ω
D. 0.22 Ω

Answer: A

250+ TOP MCQs on Geometric Mean Distance and Geometric Mean Radius – 2 and Answers

Power Systems Quiz on “Geometric Mean Distance and Geometric Mean Radius – 2”.

1. The power transmission capability of bipolar lines is approximately ____________
A. same as that of 3-ph single circuit line
B. same as that of 3-ph double circuit line
C. twice to that of 3-ph single circuit line
D. half to that of 3-ph single circuit line

Answer: A
Clarification: Power transmission by bipolar dc line is same as that three phase single line transmission.

2. HVDC system has charging current but no skin effect while transferring the power through it.
A. True
B. False

Answer: B
Clarification: Skin effect as well as the charging effect, both are absent in dc transmission system.

3. As depicted in the figure, the power will be transferred in the system from A to B by a HVDC link as shown in the figure. The voltages are indicated in the figure and I >0, then _______
A. Vab<0, Vcd<0, Vab>Vcd
B. Vab<0, Vcd>0, Vab<Vcd
C. Vab>0, Vcd<0, Vab>Vcd
D. Vab>0, Vcd>0, Vab>Vcd

Answer: D
Clarification: The given situation is such as the current is more than zero, so a positive current will flow from higher voltage to lower voltage.

4. As depicted in the figure, the power is transferred in the system from B to A by a HVDC link as shown in the figure. The voltages are indicated in the figure and I <0, then ______
A. Vab<0, Vcd<0, Vab>Vcd
B. Vab<0, Vcd>0, Vab<Vcd
C. Vab>0, Vcd>0, Vab<Vcd
D. Vab>0, Vcd>0, Vab>Vcd

Answer: C
Clarification: The given situation is such as the current is less than zero, so a positive current will flow from higher voltage to lower voltage i.e. from cd to ab.

5. A dc line carries as compared to ac line _____________
A. more power
B. less power
C. same power
D. can’t be decided

Answer: A
Clarification: A dc line carries more power as compared to ac line.

6. Back to back HVDC is used to ___________
A. increase the transmission capability
B. decrease line losses
C. provide a stable connection
D. reduce the voltage drop

Answer: C
Clarification: Back to Back connection in HVDC will provide a stable connection.

7. HVDC transmission would require which of the following equipment’s?
(i) Pulse converter
(ii) AC filter
(iii) DC filter
(iv) DC generator
A. (i)
B. (i), (ii)
C. (ii), (iv)
D. (i), (iii)

Answer: A
Clarification: Only pulse converter is needed by HVDC transmission system.

8. As compared with the HVAC lines, dc transmission system is free from ___________
A. inductance
B. capacitance
C. phase displacement
D. all of the mentioned

Answer: D
Clarification: All the factors which involve frequency will be absent in dc system as in f= 0 in dc.

9. Mostly the high voltage transmission is provided by overhead lines due to _____________
A. low cost
B. low losses
C. easy installation
D. all of the mentioned

Answer: A
Clarification: Due to economic criteria, the high voltage transmission is done by overhead lines.

10. Consider the below statements and choose the most appropriate.
(i) Guy wire is galvanised.
(ii) Guy wire should possess high conductivity.
(iii) At installation it makes an angle of 40-60 degrees with earth.
A. (i), (ii) and (iii) are true
B. Only (i) and (ii) are true
C. (ii) and (iii) are true
D. (i) and (iii) are true

Answer: A
Clarification: All the statements about the guy wire are true.

250+ TOP MCQs on Line Compensation – 1 and Answers

Power Systems Multiple Choice Questions on “Line Compensation – 1”.

1. The instantaneous voltage wave in the long transmission line is a function of _____________
A. time and distance
B. time
C. distance
D. time, distance and reactive inductance

Answer: A
Clarification: It will be a function of time and distance.

2. At any point along the line, the instantaneous voltage is ___________
A. sum of incident and reflected voltage
B. incident voltage
C. sum of incident and refracted voltage
D. twice the incident voltage

Answer: A
Clarification: V(t) = Vincident+Vrefracted.

3. The equation given below is the voltage equation,
Then it is ________________
A. reflected wave receiving to sending end
B. reflected wave sending to receiving end
C. incident wave from receiving end to sending end
D. refracted wave from receiving end to next end

Answer: A
Clarification: From the equation, cos⁡(wt-βx+Ф2), it is clear that the wave is travelling in left to right and the amplitude is reduced, so it’s a reflected wave.

4. When can an incident wave not distinguish between the termination and an infinite continuation of line?
A. When line is terminated by its characteristic impedance
B. When line is terminated by its surge impedance
C. When line is open
D. When line is terminated by its characteristic and surge impedance

Answer: A
Clarification: The characteristic (surge) impedance at the receiving end will cause a confusion for the incident wave.

5. Ferranti effect is more prominent due to ____________
A. line capacitance
B. surge capacitance
C. stray capacitance
D. all of the mentioned

Answer: A
Clarification: Line capacitance causes the no load receiving end voltage to be more than receiving end.

6. The voltage rise happening at the receiving end due to the line charging capacitance has a magnitude of _______________
A. ω2CLl2
B. ω2CLl2/2
C. ω2l2/v2
D. ω2CLl2 and ω2l2/v2

Answer: D

7. The receiving end voltage at the no load will be ____________
A. Vs(1+ w2CLl2)
B. (1+ w2CLl2)
C. Vs/(1+ w2CLl2)
D. Vs

Answer: A

8. If a line is considered with negligible power losses, then the real power transmitted will be proportional to sinδ.
A. True
B. False

Answer: A
Clarification: Pr = |Vs||Vr|(sinδ)/X.

9. If a line is considered with negligible power losses, then the real power transmitted will be proportional to ___________
A. sinδ
B. cosδ
C. δ
D. sin2δ

Answer: A
Clarification: Pr = |Vs||Vr|(sinδ)/X.

10. If a line is considered with negligible power losses, then the reactive power transmitted is proportional to receiving end voltage.
A. True
B. False

Answer: B
Clarification: Its incorrect, Q depends on the voltage drop across the line.

250+ TOP MCQs on Fuel Combustion and Combustion Equipments and Answers

Power Systems Multiple Choice Questions on “Fuel Combustion and Combustion Equipments”.

1. Which of the following is not an advantage of stoker firing?
A. Zero capital investment
B. Greater combustion capacity
C. Uniform feeding of coal into furnance
D. Saving in labour cost
Answer: A
Clarification: Stokers are the mechanical arrangement which is used to feed coals into the furnace. Due to the mechanical equipment combustion capacity increases with uniform feeding of coal of into furnace, also labour cost is reduced. Stoker firing requires installation of mechanical stoker hence, capital investment requires.

2. In case of underfeed stokers fuel is supplied in the furnace _________
A. below the point of air admission
B. above the point of air admission
C. beside the point of air admission
D. by shovels
Answer: A
Clarification: Mechanical stokers are of two types namely underfeed stokers and overfeed stokers. The two differ in manner of feeding of coal below or above the level at which primary air is admitted in the furnace. In case of underfeed stokers fuel is supplied into the furnace below the point of air admission.

3. Which of the following is most advantageous and most widely method of solid fuel firing?
A. Stoker firing
B. Underfeed firing
C. Spreader stoker firing
D. Pulverised fuel firing
Answer: D
Clarification: The advantages of using pulverised fuel outweigh the disadvantages and all the modern power plants uses pulverised fuel firing method. In pulverised fuel firing better combustion is achieved. Pulverization is a means of exposing a large surface area to the action of oxygen and consequently helping the combustion.

4. What is the main disadvantage of spreader stoker?
A. Poor control
B. Difficult operation
C. More unwanted fly ash
D. Dangerous operation
Answer: C
Clarification: In spreader stoker the coal is not fed into the furnace by means of grate. Coal is fed by means of hopper, and function of grade is only to collect and remove the ash out of furnace. Spreader stokers can burn any type of coal from lignite to samianthracite, whether they are free burning or cocking. Their disadvantage is that fly ash is more.

5. Which do you mean by pulverization?
A. Burning of crushed coal
B. Burning of uncrushed coal
C. Crushing of coal into small partials
D. Breaking coal into small particsl
Answer: C
Clarification: Pulverization is crushing of coal into fine particles. This exposes large surface area to the action of oxygen and consequently helps the combustion. Solids fuels can be used in a powderd and burn like oil and gas.

6. What is the amount of air required to burn the pulverised coal?
A. Less than air required to burn lumped coal
B. More than air required to burn lumped coal
C. More than air required to burn lumped coal
D. No air required to burn the lapped coal
Answer: A
Clarification: The surface area of pulverised coal is increased in almost the ratio of 400:1, therefore high rates of combustion are possible. Moreover a smaller quantity of air is required than when the fuel is burnt in lumped form.

7. Capital cost of pulverised fuel firing is less than hand firing.
A. True
B. False
Answer: B
Clarification: Hand firing does not require any capital investment. For pulverised fuel firing separate coal preparation plant is required which makes the installation expensive.

8. What is the main requirement of good coal burner?
A. Minimum operating and maintenance cost
B. Production of uniform flame with complete combustion
C. The burner should be easy to handle and control
D. Attainment of proper designed
Answer: B
Clarification: Main requirement of good coal burner is complete combustion with production of uniform flame. Minimum operating and maintenance cost, simplicity in operation, attainment of proper design all are requirements of complete combustion.

9. Coal burners are employed to fire the pulverised coal along with primary air in the furnace.
A. True
B. False
Answer: A
Clarification: Coal burner’s fire pulverised coal with stream of primary air into the furnace. Secondary air is then admitted separately below the burner, around the burner or elsewhere.

10. Spread stockers can be employed for boiler capacitors of _________
A. 1000 kg/hr – 14000 kg/hr
B. 586 kg/hr – 1086 kg/hr
C. 1500 kg/hr – 40000 kg/hr
D. 70,000 kg/hr – 140,000kg/hr
Answer: D
Clarification: In spreader stoker coal is fed from the coal hopper into the path of the rotor by means of a conveyor and rotor throws the coal into the furnace. Grate collects the ash and moves it out of the furnace.

.

250+ TOP MCQs on Inductance of a Single-Phase Two-Wire Line – 2 and Answers

Power Systems Interview Questions on “Inductance of a Single-Phase Two-Wire Line – 2”.

1. A 10 MVA, 11 kV alternators has positive, negative and zero sequence reactance of 25%, 40%, 10% respectively. The resistance that must be placed in the neutral such that zero sequence of fault current for a single phase to ground fault will not exceed the rated line current in pu is ______
A. 0.22
B. 0.11
C. 0.16
D. 0.97

Answer: A

2. A 10 MVA, 11 kV alternator has positive, negative and zero sequence reactance of 25%, 40%, 10% respectively. The resistance that must be placed in the neutral such that fault current for a single phase to ground fault will not exceed the rated line current in pu is _____________
A. 0.97
B. 0.22
C. 0.87
D. 0.45

Answer: A

3. A 10 MVA, 11 kV alternator has positive, negative and zero sequence reactance of 25%, 40%, 10% respectively. The resistance that must be placed in the neutral such that fault current for a single phase to ground fault will not exceed the rated line current in ohms is __________
A. 11.7
B. 12.8
C. 2.66
D. 5.2

Answer: A

4. (I) Unsymmetrical spacing configurations cause the line interference.
(II) Unsymmetrical spacing causes the voltage induction in the communication lines.
A. (I) and (II) are valid
B. Only (I) is valid
C. Only (II) is valid
D. Both are invalid

Answer: A
Clarification: Both the statements are correct as the unsymmetrical spacing causes the unbalanced voltage generation.

5. (I) Unsymmetrical spacing configurations cause the line interference.
(II) Unsymmetrical spacing causes the voltage induction in the communication lines.
The above problems can be eliminated by ________
A. transposition
B. parallel lines
C. three phase
D. all of the mentioned

Answer: A
Clarification: Transposition meaning exchange of conductors will cause the net voltage induced in the other lines to be zero as the net inductance remains constant.

6.Transposition is the mean to balance ____________
A. Inductance
B. Voltage
C. Current
D. All of the mentioned

Answer: A
Clarification: Transposition primarily balances the inductances in the line thus causing a constant inductance throughout the line.

7. Over the length of one transposition cycle of a power line, the total flux linkages of a nearby telephone line are zero for the unbalanced three phase currents.
A. True
B. False

Answer: B
Clarification: For an unbalanced supply, there will be non zero flux zero flux linkages in the telephone lines.

8. Over the length of one transposition cycle of a power line, the total flux linkages of a nearby telephone line are zero for the balanced three phase currents.
A. The above statement is valid
B. The above statement is invalid
C. It can’t be concluded
D. The above statement is valid for all conditions.

Answer: A
Clarification: Its valid only with balanced systems.

250+ TOP MCQs on Effect of Synchronous Machine Excitation – 1 and Answers

Power Systems Multiple Choice Questions on “Effect of Synchronous Machine Excitation – 1”.

1. The synchronous machine is operating at a normal condition at the generating system, then the angle between rotor axis and the stator magnetic axis is _____________
A. Load angle
B. Power factor angle
C. Impedance angle
D. None of the mentioned

Answer: A

2. The angle shown in the figure depends on which of the following given options?
A. Loading of the system
B. Power factor
C. Operating frequency
D. Power factor, operating frequency, loading of the system

Answer: A
Clarification: Load angle depends on the loading of the system, as the load in added or decreased, the synchronous machine will accelerate or decelerate with respect to stator field.

3. Swing equation is very famous for describing the relation between the ___________
A. rotor motion and stator field
B. stator and rotor field
C. load angle and rotor field
D. moment of inertia and rotor motion

Answer: A
Clarification: Swing equation describes the relative motion between rotor load angle with respect to stator field as a function of time.

4. Swing equation which describes the relative motion of the rotor of the machine, is a __________
A. linear and second-order differential equation
B. non linear and second-order differential equation
C. non linear and first-order differential equation
D. non linear and hyperbolic equation

Answer: B

5. A variation in the power transfer had been observed at the generating station while power exchange process due to ______ and is known as ______
A. swing of the machine, inertial response
B. sub synchronism, hunting
C. sub synchronism, inertial response
D. swing of the machine, falling out of the rotor

Answer: A
Clarification: The power exchange between the mechanical rotor and the electrical grid due to the swing of the rotor is called inertial response.

6. Why the angle δ, rotor angle is famously called as the load angle in the equation of rotor dynamics?
A. Due to power exchange is a function of δ
B. Because it dictates the reactive power compensation
C. Due to load variations
D. No dependency on the load dynamics

Answer: A
Clarification: Rotor angle is the emf angle and power is a function of it.

7. The transient stability and the steady state stability of a power transmission system ________
A. maintain synchronism between machine and tie lines at all the circumstances
B. maintains frequency exactly at 50 Hz
C. maintain voltage regulation precisely
D. all of the mentioned

Answer: A
Clarification: Transient stability and steady state stability maintain synchronism between the generating station and tie line.

8. We can say a system is stable at steady state is not affected by ____________
A. line losses
B. line reactance
C. generator reactance
D. excitation of alternators

Answer: A
Clarification: Line losses do not affect the stability limit of the system.

9. The transient instabilities can occur in a system by ___________
A. Sudden load changes
B. Switching operation
C. Faults
D. Suddenn load changes, switching operation and faults

Answer: D
Clarification: All the mentioned factors affect the transient stability of a system.

10. Post a three phase fault that occurs in a system, then its transient stability can be examined using ___________
A. solution of swing equation
B. equal area criterion
C. solution of swing equation and equal area criterion
D. solution of swing equation or equal area criterion

Answer: A
Clarification: Swing equation provides the rotor dynamics at the transient conditions.