Definition and Power Quality Issues — MCQs – EE

1. The term power quality refers to:
(A) The degree to which the voltage, current, and frequency conform to standard values
(B) The amount of power consumed by a load
(C) The generation capacity of a power station
(D) The power factor of the system

2. Poor power quality results in:
(A) Malfunctioning or damage to electrical equipment
(B) Reduced system voltage only
(C) Increased transmission capacity
(D) Improved efficiency

3. The main indicators of power quality are:
(A) Voltage, current, frequency, and waveform
(B) Resistance, inductance, and capacitance
(C) Temperature and pressure
(D) Load and speed

4. A voltage sag (dip) is defined as:
(A) A short-duration reduction in RMS voltage
(B) A permanent reduction in voltage
(C) A total loss of voltage
(D) An increase in RMS voltage

5. A voltage swell is defined as:
(A) A short-duration increase in RMS voltage
(B) A steady reduction in current
(C) A voltage imbalance
(D) A power outage

6. The most common cause of voltage sag is:
(A) Starting of large motors or short circuits
(B) Overvoltage conditions
(C) Frequency fluctuation
(D) Grounding faults

7. A voltage interruption occurs when:
(A) Voltage drops to zero for a period of time
(B) Current increases suddenly
(C) Frequency remains constant
(D) Voltage exceeds the rated limit

8. Harmonics are caused mainly by:
(A) Non-linear electrical loads
(B) Purely resistive loads
(C) Balanced three-phase systems
(D) Transformers under no-load

9. Examples of non-linear loads include:
(A) Variable frequency drives, computers, and UPS systems
(B) Incandescent lamps
(C) Induction motors
(D) Heaters

10. Total Harmonic Distortion (THD) quantifies:
(A) The total amount of harmonic distortion in voltage or current
(B) The efficiency of the power system
(C) The frequency stability
(D) The phase angle difference

11. A voltage flicker is:
(A) Rapid and repetitive changes in voltage magnitude
(B) Long-term voltage imbalance
(C) A type of harmonic distortion
(D) A frequency deviation

12. Transients are:
(A) Short-duration, high-frequency voltage or current disturbances
(B) Long-term voltage sags
(C) Frequency deviations
(D) Load fluctuations

13. The most common cause of transients is:
(A) Switching or lightning surges
(B) Overcurrent
(C) Grounding
(D) Voltage unbalance

14. Voltage unbalance occurs when:
(A) The magnitudes or phase angles of three-phase voltages are unequal
(B) The system operates at low voltage
(C) Power factor is high
(D) Frequency increases

15. Frequency variation occurs when:
(A) There is an imbalance between generation and load demand
(B) Transmission line resistance changes
(C) The load power factor changes
(D) The system operates under unity power factor

16. The ideal power supply should have:
(A) Constant voltage, frequency, and sinusoidal waveform
(B) Variable frequency and voltage
(C) High harmonic distortion
(D) Constant current and zero voltage

17. The effect of poor power quality on motors is:
(A) Overheating and reduced efficiency
(B) Increased torque
(C) Reduced mechanical vibration
(D) Higher power factor

18. Poor power quality can cause computers and PLCs to:
(A) Malfunction or reset
(B) Increase performance
(C) Operate faster
(D) Consume less energy

19. Overvoltage can cause:
(A) Insulation failure or equipment damage
(B) Reduced losses
(C) Higher efficiency
(D) Stable operation

20. Undervoltage conditions result in:
(A) Reduced torque in motors and poor performance
(B) Improved insulation life
(C) Increased voltage stability
(D) Higher power factor

21. Harmonics mainly affect:
(A) Transformers, cables, and capacitors
(B) Mechanical systems
(C) Lighting systems only
(D) Relays

22. Excessive THD can lead to:
(A) Overheating and overloading of neutral conductors
(B) Improved voltage regulation
(C) Reduced current losses
(D) Enhanced insulation life

23. Power factor correction capacitors may worsen power quality if:
(A) Resonance occurs with system inductance
(B) Connected at unity power factor
(C) Installed at distribution end
(D) Operated below rated voltage

24. Interharmonics are:
(A) Frequencies that are not integer multiples of the fundamental frequency
(B) DC components
(C) Even multiples of 60 Hz
(D) Noise below the fundamental

25. The most sensitive equipment to power quality disturbances is:
(A) Electronic and computer-based devices
(B) Induction motors
(C) Transformers
(D) Heaters

26. Notching in voltage waveform occurs due to:
(A) Commutation in power electronic converters
(B) Magnetic saturation
(C) Frequency variation
(D) Resistive heating

27. Poor grounding systems can lead to:
(A) Increased voltage fluctuations and noise
(B) Improved harmonic performance
(C) Better voltage regulation
(D) Reduced transients

28. Surge protectors are used to mitigate:
(A) Voltage spikes and transients
(B) Frequency deviations
(C) Voltage dips
(D) Harmonic currents

29. IEEE Standard 1159 provides guidelines for:
(A) Power quality monitoring and definitions
(B) Transmission line design
(C) Grounding methods
(D) Load flow studies

30. The main goal of addressing power quality issues is to:
(A) Ensure reliable, efficient, and disturbance-free operation of electrical systems
(B) Reduce installation cost only
(C) Increase voltage levels
(D) Eliminate the need for grounding