80+ Power Quality and Management Solved MCQs

These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .

Take a Test

1.	Non-sinusoidal waveforms are made of
A.	different sinusoidal waveforms
B.	fundamental and even harmonics
C.	fundamental and odd harmonics
D.	even and odd harmonics only
Answer» A. different sinusoidal waveforms

discuss

2.	The positive and negative halves of a complex wave are symmetrical when
A.	it contains even harmonics
B.	phase difference between even harmonics and fundamentals is 0 or it
C.	it contains odd harmonics
D.	phase difference between even harmonics and fundamental is either n/2 or 3n/2
Answer» C. it contains odd harmonics

discuss

3.	The rms value of the complex voltage given by v = 161i sin cot + 12 Ari sin Rot is
A.	20 Ari
B.	20
C.	28
D.	192
Answer» B. 20

discuss

4.	In a 3-phase system,the harmonic has negative phase sequence of RBY.
A.	9
B.	13
C.	5
D.	15
Answer» C. 5

discuss

5.	Two complex waves will have the same wave-shape if
A.	they contain the same harmonics
B.	ratio of corresponding harmonics to their respective fundamentals is the same
C.	harmonics are similarly spaced with respect to their fundamental
D.	they have all of the above
Answer» D. they have all of the above

discuss

6.	The trigonometric Fourier series for a complex wave will contain positive cosine terms only when
A.	it contains even harmonics
B.	its two half-cycles are symmetrical
C.	its value is zero at 0= n/2, 3n/2 etc.
D.	its value is zero at 0= n, 2n etc.
Answer» C. its value is zero at 0= n/2, 3n/2 etc.

discuss

7.	Tansient disturbance is produced in a circuit whenever
A.	it is suddenly connected or discon nected from the supply
B.	it is shorted
C.	its applied voltage is changed suddenly
D.	all of the above
Answer» D. all of the above

discuss

8.	There are no transients in pure resistive circuits because they
A.	offer high resistance
B.	obey Ohm's law
C.	have no stored energy
D.	are linear circuits
Answer» C. have no stored energy

discuss

9.	Transient current in electrical circuits are associated with
A.	inductors
B.	capacitors
C.	resistors
D.	both (a) and (b)
Answer» D. both (a) and (b)

discuss

10.	The transients which are produced due to sudden but energetic changes from one steady state of a circuit to another are called transients.
A.	initiation
B.	transition
C.	relaxation
D.	subsidence
Answer» B. transition

discuss

11.	In an R-L circuit connected to an alternating sinusoidal voltage, size of transient current primarily depends on
A.	the instant in the voltage cycle at which circuit is closed
B.	the peak value of the steady-state current
C.	the circuit impedance
D.	the voltage frequency
Answer» A. the instant in the voltage cycle at which circuit is closed

discuss

12.	Double-energy transients are produced in circuits consisting of
A.	two or more resistors
B.	resistance and inductance
C.	resistance and capacitance
D.	resistance, inductance and capacitance
Answer» D. resistance, inductance and capacitance

discuss

13.	The transient current in a loss-free L-C circuit when excited from an ac source is a/an sine wave.
A.	over-damped
B.	undamped
C.	under-damped
D.	critically damped
Answer» B. undamped

discuss

14.	Transient current in an R-L-C circuit is oscillatory when
A.	R =0
B.	R> 2f-17
C.	R <2
D.	R =2
Answer» C. R <2

discuss

15.	For measuring positive, negative and zero sequence voltages in a system, the reference is taken as :
A.	Neutral of the system only
B.	Ground only
C.	For zero sequence neutral and for positive and negative the ground
D.	None of the above
Answer» D. None of the above

discuss

16.	The most economic load on an underground cable is :
A.	Greater than its surge loading
B.	Less thart the surge loading
C.	Equal to the surge loading
D.	None of the above is necessary
Answer» B. Less thart the surge loading

discuss

17.	In case of a 3-phase short circuit is a system, the power fed into the system is :
A.	Mostly reactive
B.	Mostly active
C.	Active and reactive both equal
D.	Reactive only
Answer» A. Mostly reactive

discuss

18.	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
Answer» C. Above resonance frequency

discuss

19.	A generator is connected to a synchronous motor. From stability point of view it is preferable to have :
A.	Generator neutral reactance grounded and motor neutral resistance grounded
B.	Generator and motor neutrals resistance grounded
C.	Generator and motor neutrals reactance grounded
D.	Generator neutral resistance and motor neutral reactace grounded
Answer» D. Generator neutral resistance and motor neutral reactace grounded

discuss

20.	The positive sequency component of voltage at the point of fault is zero when it is a :
A.	3-phase fault
B.	L-L fault
C.	L-L-G fault
D.	L-G fault
Answer» C. L-L-G fault

discuss

21.	Tick out the correct statement :
A.	The negative and zero sequence voltages are maximum at the fault point and decreases towards the neutral
B.	The negative and zero sequence voltages are minimum at the fault point and increase towards the neutral
C.	The negative sequence is maximum and zero sequence minimum at the fault point and decrease and increase respectively towards the neutral.
D.	None of the above
Answer» D. None of the above

discuss

22.	The order of the lightning discharge current is :
A.	10,000 amp
B.	100 amp
C.	1 amp
D.	1 microampere
Answer» A. 10,000 amp

discuss

23.	The magnetising-inrush-current in a transformer is rich in :
A.	3rd harmonics
B.	5th harmonics
C.	7th harmonics
D.	2nd harmonics
Answer» C. 7th harmonics

discuss

24.	The in-rush current of a transformer at no load is maximum if the supply voltage is switched on
A.	At zero voltage value
B.	At peak voltage value
C.	At V/2 value
D.	At ,6 /2V value
Answer» A. At zero voltage value

discuss

25.	Pure inductive circuit takes power (reactive) from the a.c. line when
A.	both applied voltage and current rise
B.	both applied voltage and current decrease
C.	applied voltage decreases but current increases
D.	(a) and (b)
Answer» C. applied voltage decreases but current increases

discuss

26.	With 100% series compensation of lines
A.	the circuit is series resonant at power frequency
B.	low transient voltage
C.	high transient current
D.	(a) and (b)
Answer» D. (a) and (b)

discuss

27.	In a pure LC parallel circuit under resonance condition, current drawn from the supply mains is
A.	very large
B.	V ,FTE
C.	V /11-j
D.	Zero
Answer» D. Zero

discuss

28.	A lightning arrestor connected between the line and earth in a power system
A.	protects the terminal equipment against travelling surges
B.	protects the transmission line against lightning stroke
C.	suppresses high frequency oscillations in the line
D.	reflects back the travelling wave approaching it
Answer» A. protects the terminal equipment against travelling surges

discuss

29.	Lightning arresters are used in power systems to protect electrical equipments against
A.	direct strokes of lightning
B.	power frequency overvoltages
C.	overvoltages due to indirect lightning stroke
D.	overcurrents due to lightning stroke
Answer» A. direct strokes of lightning

discuss

30.	Consider the following statements : The transient stability of the power system under unbalanced fault conditions can be effectively improved by 1. Excitation control 2. phase-shifting transformer 3. single-pole switching of circuit breakers 4. increasing the turbine input. Of these statements
A.	1 and 2 are correct
B.	2 and 3 are correct
C.	3 and 4 are correct
D.	1 and 3 are correct
Answer» C. 3 and 4 are correct

discuss

31.	One current transformer (CT) is mounted over a 3-phase 3-core cable with its sheath and armour removed from the portion covered by the CT. An ammeter placed in the CT secondary would measure
A.	the positive sequence current
B.	the negative sequence current
C.	the zero sequence current
D.	three times the zero sequence
Answer» D. three times the zero sequence

discuss

32.	Earth wire on EHV overhead transmission line is provided to protect the line against
A.	lightning surge
B.	switching surge
C.	excessive fault voltages
D.	corona effect
Answer» A. lightning surge

discuss

33.	The velocity of travelling wave through a cable of relative permittivity 9 is
A.	9 x 108 m/s
B.	3 x 108 m/s
C.	108 m/s
D.	2 x 108 ms
Answer» C. 108 m/s

discuss

34.	A wave-trap is used at the termination of a HVAC overhead line to a station switchyard to
A.	prevent the transformer magnetising harritonics from reaching the overhead line
B.	damp the incoming surge waves from the overhead lines
C.	attenuate sub-harmonic oscillations
D.	provide for carrier communication
Answer» D. provide for carrier communication

discuss

35.	Shunt compensation in an EHV line is used to improve
A.	stability and fault level
B.	fault level and voltage profile
C.	voltage profile and stability
D.	stability, fault level and voltage profile
Answer» B. fault level and voltage profile

discuss

36.	The principal information obtained from load flow studies in a power system are 1. magnitude and phase angle of the voltage at each bus. 2. reactive and real power flows in each of lines. 3. total power loss in the network. 4. Transient stability limit of the system Select the correct answer from the codes given below :
A.	I and 2
B.	3 and 4
C.	1,2 and 3
D.	2 and 4
Answer» C. 1,2 and 3

discuss

37.	While rising and while falling, if a wave is symmetrical, it contains
A.	even harmonics in addition to fundamental
B.	odd harmonics in addition to fundamental
C.	(b) both odd and even harmonics in addition to fundamental
D.	none of the above
Answer» B. odd harmonics in addition to fundamental

discuss

38.	While rising and falling if a wave is not symmetrical, it contains
A.	even harmonics in addition to fundamental
B.	odd harmonics in addition to fundamental
C.	both odd and even harmonics in additions to fundamental
D.	none of the above
Answer» A. even harmonics in addition to fundamental

discuss

39.	The main reason for generation of harmonics in a transformer could be
A.	fluctuating load
B.	poor insulation
C.	mechanical vibrations
D.	saturation of core
Answer» D. saturation of core

discuss

40.	Harmonics in transformer result in
A.	increased core losses
B.	increased 12R losses
C.	magnetic interference with communication circuits
D.	all of the above
Answer» D. all of the above

discuss

41.	Which fractional pitch will eliminate the seventh harmonic from the voltage waveform of an alternator?
A.	6/7
B.	7/8
C.	5/6
D.	None of the above
Answer» A. 6/7

discuss

42.	Most of the power quality problems are related to ______
A.	Transmission Issue
B.	Grounding Issue
C.	Distribution Issue
D.	all of the above
Answer» B. Grounding Issue

discuss

43.	Which of the following is not considered as good power quality voltage
A.	Power Supply is more compared to demand
B.	Constant sine wave
C.	Constant Velocity
D.	Constant RMS Value unchanged with time
Answer» A. Power Supply is more compared to demand

discuss

44.	Lightening and Tree striking on a live conductor is an example________ Power Quality issue.
A.	Voltage Sag
B.	Voltage Swell
C.	Interruption
D.	Surge
Answer» B. Voltage Swell

discuss

45.	Interruption is
A.	complete loss of power
B.	complete loss of voltage
C.	complete loss of current
D.	all the above
Answer» B. complete loss of voltage

discuss

46.	The Transients in the power system occurs for
A.	less than two complete cycles
B.	exact two complete cycles
C.	less than one complete cycles
D.	exact one complete cycles
Answer» C. less than one complete cycles

discuss

47.	The most common cause of long interruption is ______
A.	Faults
B.	Outages
C.	Both (a) & (b)
D.	none of the above
Answer» C. Both (a) & (b)

discuss

48.	Outage is the
A.	Removal of Primary Component
B.	(b) No Power Generation
C.	Transmission Faults
D.	(d) None of the above
Answer» A. Removal of Primary Component

discuss

49.	Single Phase Tripping is generally used in _________________.
A.	Transmission System
B.	Distribution System
C.	Low Voltage System
D.	Generation System
Answer» A. Transmission System

discuss ⁽¹⁾

50.	The Short Interruptions occurs for
A.	Less than two complete cycles
B.	exact two complete cycles
C.	less than one complete cycles
D.	exact one complete cycles
Answer» C. less than one complete cycles

discuss

80+ Power Quality and Management Solved MCQs

Non-sinusoidal waveforms are made of

The positive and negative halves of a complex wave are symmetrical when

The rms value of the complex voltage given by v = 161i sin cot + 12 Ari sin Rot is

In a 3-phase system,the harmonic has negative phase sequence of RBY.

Two complex waves will have the same wave-shape if

The trigonometric Fourier series for a complex wave will contain positive cosine terms only when

Tansient disturbance is produced in a circuit whenever

There are no transients in pure resistive circuits because they

Transient current in electrical circuits are associated with

The transients which are produced due to sudden but energetic changes from one steady state of a circuit to another are called transients.

In an R-L circuit connected to an alternating sinusoidal voltage, size of transient current primarily depends on

Double-energy transients are produced in circuits consisting of

The transient current in a loss-free L-C circuit when excited from an ac source is a/an sine wave.

Transient current in an R-L-C circuit is oscillatory when

For measuring positive, negative and zero sequence voltages in a system, the reference is taken as :

The most economic load on an underground cable is :

In case of a 3-phase short circuit is a system, the power fed into the system is :

An RLC series circuit remains predominantly inductive :

A generator is connected to a synchronous motor. From stability point of view it is preferable to have :

The positive sequency component of voltage at the point of fault is zero when it is a :

Tick out the correct statement :

The order of the lightning discharge current is :

The magnetising-inrush-current in a transformer is rich in :

The in-rush current of a transformer at no load is maximum if the supply voltage is switched on

Pure inductive circuit takes power (reactive) from the a.c. line when

With 100% series compensation of lines

In a pure LC parallel circuit under resonance condition, current drawn from the supply mains is

A lightning arrestor connected between the line and earth in a power system

Lightning arresters are used in power systems to protect electrical equipments against

Consider the following statements : The transient stability of the power system under unbalanced fault conditions can be effectively improved by 1. Excitation control 2. phase-shifting transformer 3. single-pole switching of circuit breakers 4. increasing the turbine input. Of these statements

One current transformer (CT) is mounted over a 3-phase 3-core cable with its sheath and armour removed from the portion covered by the CT. An ammeter placed in the CT secondary would measure

Earth wire on EHV overhead transmission line is provided to protect the line against

The velocity of travelling wave through a cable of relative permittivity 9 is

A wave-trap is used at the termination of a HVAC overhead line to a station switchyard to

Shunt compensation in an EHV line is used to improve

While rising and while falling, if a wave is symmetrical, it contains

While rising and falling if a wave is not symmetrical, it contains

The main reason for generation of harmonics in a transformer could be

Harmonics in transformer result in

Which fractional pitch will eliminate the seventh harmonic from the voltage waveform of an alternator?

Most of the power quality problems are related to ______

Which of the following is not considered as good power quality voltage

Lightening and Tree striking on a live conductor is an example________ Power Quality issue.

Interruption is

The Transients in the power system occurs for

The most common cause of long interruption is ______

Outage is the

Single Phase Tripping is generally used in _________________.

The Short Interruptions occurs for

Consider the following statements : The transient stability of the power system under unbalanced fault conditions can be effectively improved by
1. Excitation control
2. phase-shifting transformer
3. single-pole switching of circuit breakers
4. increasing the turbine input. Of these statements