# 80+ Power Quality and Management Solved MCQs

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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
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
3.

A. 20 Ari
B. 20
C. 28
D. 192
4.

A. 9
B. 13
C. 5
D. 15
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
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.
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
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
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)
10.

A. initiation
B. transition
C. relaxation
D. subsidence
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
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
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
14.

A. R =0
B. R> 2f-17
C. R <2
D. R =2
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
16.

## The most economic load on an underground cable is :

D. None of the above is necessary
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
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
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
20.

A. 3-phase fault
B. L-L fault
C. L-L-G fault
D. L-G fault
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
22.

A. 10,000 amp
B. 100 amp
C. 1 amp
D. 1 microampere
23.

A. 3rd harmonics
B. 5th harmonics
C. 7th harmonics
D. 2nd harmonics
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
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
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)
27.

A. very large
B. V ,FTE
C. V /11-j
D. Zero
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
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
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
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
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
33.

A. 9 x 108 m/s
B. 3 x 108 m/s
C. 108 m/s
D. 2 x 108 ms
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
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
36.

A. I and 2
B. 3 and 4
C. 1,2 and 3
D. 2 and 4
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
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
39.

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

B. poor insulation
C. mechanical vibrations
D. saturation of core
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
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
42.

## Most of the power quality problems are related to ______

A. Transmission Issue
B. Grounding Issue
C. Distribution Issue
D. all of the above
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
44.

A. Voltage Sag
B. Voltage Swell
C. Interruption
D. Surge
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
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
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)
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
49.

## Single Phase Tripping is generally used in _________________.

A. Transmission System
B. Distribution System
C. Low Voltage System
D. Generation System
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
51.

## The most common way to calculate voltage sag is from ______

A. Average Voltage
B. Peak Voltage
C. RMS Voltage
D. none of the above
52.

## Effect of temperature rise in overhead lines is to

A. Increase Sag Decrease Tension
B. Decrease Sag Increase Tension
C. Increases both
D. Decreases Both
Answer» A. Increase Sag Decrease Tension
53.

## What should be the value of sag for proper operation of overhead transmission line?

A. High
B. Low
C. Neither too low nor too high
D. Anything
Answer» C. Neither too low nor too high
54.

## Voltage dips cannot be caused by which of the following:

A. Switching on of Large Loads
B. Local and Remote faults
D. Capacitive Switching
55.

## Which one of the following cannot be possible with voltage surges:

A. Damaging to insulation
B. Tripping of Sensitive Equipment
C. Flicker in Incandescent Lamps
D. Damage to electronic components
Answer» C. Flicker in Incandescent Lamps
56.

## During sag, power electronic component will trip, this will decrease ______

B. Supply Voltage
D. none of the above
57.

A. Current
B. Voltage
C. Fluctuations
D. Harmonics
58.

## The major cause of voltage sag is

A. Malfunction of primary component
B. Equipment Failure
C. Starting of large Induction Machine
D. All the above
59.

## To obtain a constant current input, a inductor is placed in current source inductor (CSI) in:

A. Parallel
B. Series
C. Both Series and Parallel
D. Not placed at all
60.

A. Constant
B. Not Constant
C. High
D. low
61.

## Reducing the number of short-circuit faults in a system, reduces ______

A. Sag
B. Interruptions
C. Sag & Interruptions
D. none of the above
62.

## Current-limiting fuses are able to clear a fault within one _______.

A. Half cycle
B. full cycle
C. will not clear
D. none of the above
63.

## By implementing changes in the supply system, the severity of the event will__.

A. Reduce
B. Increase
C. Remains the same
D. None of the above
64.

## The main mitigation equipments is___

A. UPS
B. Storage device
C. voltage source converter
D. All the above
65.

## During normal operation, the UPS takes its power from the supply, rectifies the ac voltage to dc and inverts it again to ac with the

A. same frequency and rms value
B. Different frequency and rms value
C. same frequency and different rms value
D. Different frequency and same rms value
Answer» A. same frequency and rms value
66.

## What is the value of transient stability limit?

A. Higher than steady state stability limit
B. Lower than steady state stability limit.
C. Depending upon the severity of load
D. All of these
67.

## By using which component can the transient stability limit of a power system be improved?

A. Series resistance
B. Series capacitor
C. Series inductor
D. Shunt resistance
68.

## What is transient stability limit?

A. The maximum flow of power through a particular point in the power system without loss of stability when small disturbances occur.
B. The maximum power flow possible through a particular component connected in the power system.
C. The maximum flow of power through a particular point in the power system without loss of stability when large and sudden disturbances occur
D. All of these
Answer» C. The maximum flow of power through a particular point in the power system without loss of stability when large and sudden disturbances occur
69.

## Which among the following methods is used for improving the system stability?

A. Increasing the system voltage
B. Reducing the transfer reactance
C. Using high speed circuit breaker
D. All of these
70.

## What is steady state stability limit?

A. The maximum flow of power through a particular point in the power system without loss of stability when small disturbances occur.
B. The maximum power flow possible through a particular component connected in the power system.
C. The maximum flow of power through a particular point in the power system without loss of stability when sudden disturbances occur
D. All of these
Answer» A. The maximum flow of power through a particular point in the power system without loss of stability when small disturbances occur.
71.

## Which among these is a classification of power system stability?

A. Frequency stability
B. Voltage stability
C. Rotor angle stability
D. All of these
72.

## The stability of the power system is not affected by which among these?

A. Generator reactance
B. Line losses
C. Excitation of generators
D. All of these
73.

## What is power system stability?

A. The maximum power flow possible through a particular component connected in the power system.
B. The ability of the power system to regain the state of operating equilibrium point when the system is subjected to any disturbances.
C. It is a phenomenon in which a power system losses its operating equilibrium when subjected to large disturbances.
D. All of these
Answer» B. The ability of the power system to regain the state of operating equilibrium point when the system is subjected to any disturbances.
74.

A. P/Q
B. Q/P
C. P/S
D. S/P
75.

A. 45 degree
B. 60 degree
C. 75 degrees
D. 90 degree
76.

## In a load comprising of resistance and inductance:

C. Both are in phase
D. Any of above
77.

B. Lagging
C. Both of these
D. Any of these
78.

## A circuit having poor power factor will draw:

A. No current
B. Low current
C. Normal current
D. High current
79.

B. Lagging
C. Both of these
D. Any of these
80.

A. 100
B. 200
C. 300
D. 400
81.

## Which of the following statement refer to IEEE definition on power quality?

A. The concept of powering of any electronic equipment in a manner suitable for the equipment.
B. The concept grounding sensitive electronic equipment in a manner suitable for the equipment.
C. The concept of grounding for whatever equipment in a manner suitable for the equipment.
D. The concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment.
Answer» D. The concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment.
82.

## Which of the following explains the reasons for concern with power quality?

A. End-user equipment become more sensitive to power quality due to many microprocessor-based controls
B. The adjustable-speed motor drives helps to reduce harmonic levels
C. Modern load & equipment are less sensitive to power quality variations.
D. Power electronics equipment do not affect the power quality at all.
Answer» A. End-user equipment become more sensitive to power quality due to many microprocessor-based controls
83.

## The following statement describes the effects of poor power quality, EXCEPT

A. Equipment malfunction
B. Increased costs from downtime
C. Premature failure of equipment
D. Reduced maintenance, repair time and expenses
Answer» C. Premature failure of equipment
84.

## Since most of the industrial loads are inductive type, which of the following will help to correct the power factor?

A. Increase lagging reactive current demand of the loads
B. Compensate lagging reactive current by supplying leading reactive current to the power system
C. Compensate leading reactive current by supplying lagging reactive current to the power system
Answer» B. Compensate lagging reactive current by supplying leading reactive current to the power system
85.

## Which of the following is an advantages of power factor correction (PFC)?

A. Electricity bills increased
B. Power consumption reduced
C. Increased heating in equipment
D. Extra kVAr availability from the supply
86.

## Which of the following represents short duration voltage variation?

A. Under Voltage
B. Over Voltage
C. Voltage Outage
D. Voltage Interference
87.

## Which of the following terms describes the transient voltage variation?

A. The duration is within 0.5 s to 30 cycles
B. It can be classify to instantaneous, momentary or temporary
C. It can be solved by using static Var systems
D. It can be caused by lightning, electrostatic discharge or load switching.
Answer» D. It can be caused by lightning, electrostatic discharge or load switching.
88.

## Which of the following terms describes the effects of harmonics to industrial power systems?

A. Disturbance to Electric and Electronic Devices
B. Extra Fault Current
C. Lower Losses
D. Increased costs from downtime
Answer» A. Disturbance to Electric and Electronic Devices