EE2028– Power Quality

UNIT I
INTRODUCTION TO POWER QUALITY
PART – A
1. What is Power Quality?
2. How can Power Quality problems be detected?
3. What are Harmonics?
4. What are the various power quality issues?
5. Classify power quality events in long duration events and shout duration events.
6. Differentiate between sag and swell.
7. Mention the types of sag.
8. What are the causes of sags?
9. Define Waveform Distortion.
10. What are the components of waveform distortion?
11. Define Total harmonic distortion and mention the formula used to calculate THD.
12. Define Total Demand Distortion (TDD).
13. Define for the following terms :( i) DC offset, (ii) Inter harmonics, (iii) Voltage Flicker
14. List any four standards available in power quality.
PART – B
1. (a)What are the major power quality issues? Explain in detail (8)
(b)Define power quality? Explain the reasons for increased concern in power quality. (8)
2. Explain the various types of power quality disturbances and impacts of powerquality. (16)
3. (a) Discuss the following characteristics of power quality events
(i) Short duration variations.
(ii) Long duration variations. (8)
(b)Discuss in detail about transients. (8)
4. Discuss in detail about sags and swells. (16)
5. Explain for the following related with Power quality.
(i) Voltage imbalance (ii) Under voltage (ii) Over voltage (iv) Frequency variation (16)
6. Define waveform distortion? Explain the waveform distortion categories. (16)
7. What is harmonics? Explain harmonic distortion with relevant waveforms (16)
8. Explain the following:
(i)Total harmonic distortion (ii) Total demand distortion (16)
9. (a)Write the various IEEE and IEC power quality standards. (8)
(b)Explain the following event based disturbances:
(i)Dip
(ii)Swell
(iii)Transients (8)
Explain about the events described in the curve. (16)
11. With a waveform sketch, explain the terms
(i) Voltage sag
(ii) Voltage interruption
(iii)Voltage swells.
(iv) Sag with harmonics. (16)
12. Explain the following steady state disturbances.
(i)Magnitude (ii) Unbalance (iii) Harmonics (iv) Flicker. (16)

UNIT II
VOLTAGE SAGS AND INTERRUPTIONS
PART-A
1. What is Voltage Sag?
2. What are the causes of sag?
3. What are three levels of possible solutions to voltage sag and momentaryinterruption problems?
4. List some IEEE Standards Associated with Voltage Sags.
5. What are the sources of sags and Interruption?
6. Name the different motor starting methods.
7. Name any four types of sag mitigation devices.
8. Define active series compensation devices.
9. What is the main function of DSTATCOM?

PART-B
1. (a)Discuss the sources of sags and interruption (8)
(b)Discuss in detail about the sag performance evaluation indices. (8)
2. What is the need of estimating sag performance? Explain the different methods of estimating
voltage sag performance. (16)
3. (a)Explain the sag performance evaluation methods. (8)
(b)Explain the various causes and effects of voltage sags. (8)
4. Explain the following causes of sags.
(i)Voltage sag due to motor sag
(ii)Voltage sag due to single line to ground fault.
(iii) Voltage sags due to transformer energizing. (16)
5. What are the different voltage sag mitigation techniques? Explain in details. (16)
6. (a) Explain the principle of DVR operation used for sag mitigation. (8)
(b)Discuss in detail about the active series compensator. (8)
7. (a) Explain the operation of distributed static compensator (DSTATCOM)used for sag
mitigation. (8)
(b)Explain the solid state transfer switch with the transfer operation. (8)
8. (a) Explain the procedure for estimating the sag severity indices. (8)
(b)Mention the standards associated with the voltage sag. (8)
9. Explain the system adapted to estimate the severity of the sag occurred due to various sources.(16)
10. Explain the following sag mitigation techniques.
(i) Static UPS with minimal energy storage
(ii) Backup storage energy supply
(iii) Flywheel with UPS system. (16)
11. Discuss about estimating the cost of voltage sag events. (16)

UNIT III
OVERVOLTAGES
PART-A
1. Define transient over voltages.
2. Define voltage magnification phenomena?
3. Give the various aspects of equipment specific design and protection issues for the capacitor
switching transients.
4. What are the various Causes of over voltages?
5. What is the need of surge arrestors?
6. What is metal-oxide surge-arrester?
7. What is the role of surge arrestor on shielded and unshielded transmission line?
8. Define lightning phenomena.
9. What is Ferro resonance?
10. Give the cable life equation as a function of impulses.
11. What is the need of Computer analysis tools for transient studies?
12. Give any two analysis examples available in PSCAD/EMTDC?
PART-B
1. What are transient over voltages? Explain the different types of transient over voltages. (16)
2. (a) Draw the CBEMA curve for transient over voltages and explain. (8)
(b) Explain the problems associated with Ferro resonance. (8)
3. (a) What are the different sources of transient over voltages? Discuss the capacitor switching
transient. (8)
(b)What are the important concerns for capacitor bank switching? (8)
4. Define lightning? Discuss in detail about the over voltages due to lightning and the problems
associated with it. (16)
5. (a) Explain in detail the mechanism of lightning. (8)
(b)Explain the phenomena of Ferro resonance. (8)
6. Draw the standardized waveform of the lightning induced voltage. Discuss about the wave
shape of the lightning current. (16)
7. (a) What is the need for protection against over voltages? What are the basic principles of over
voltages protection of load equipments? (8)
(b)Explain in detail about various methods to mitigate voltage swells. (8)
8. (a) Explain in detail about the surge arrestors and surge suppressors. (8)
(b)What are the advantages of surge arrestors? Discuss about the application module. (8)
9. Explain the following:
(i) Low pass filters.
(ii) Power conditioners.
(iii)Surge filters. (16)
10.(a)Explain about the underground cable system protection. (8)
(b)Explain in detail about the protection of transformers. (8)
11 (a) what are the various lightning protection of over voltage lines? Explain them. (8)
(b)Explain the use of PSCAD in analyzing the Power quality. (8)
12.(a)What are the advantages of computer analysis tools? Discuss about PSCAD and EMTP  For transient studies. (8)
UNIT IV
HARMONICS
PART-A
1. Define Harmonics.
2. Define true power factor.

4. What is voltage and current distortion?
5. What is total harmonic distortion?
6. What is total demand distortion?
7. Mention the harmonic effects on devices and loads.
8. Mention the harmonic sources from industrial loads.
9. State the different types of inverters.
10. What is Variable Voltage Inverter?
11. What are the objectives of IEEE standard?
12. What are the applications of active filters?
13.Give at least two IEC standards for EMC.
14. What is the need of filtering in harmonic studies?
PART-B
1. Explain briefly about fundamentals of harmonics generation and waveform distortion. (16)
harmonic studies. (8)
(b) Explain the concept of harmonic phenomena under the presence of harmonic
3. Explain the following terms.
(i)Harmonic distortion
(ii)Current distortion
(iii)Voltage distortion (16)
4. (i)What are the two indices used in Power system? Explain about it briefly. (8)
(ii) Give the power definitions under non sinusoidal conditions. Explain briefly. (8)
5. (a).Explain briefly about various harmonic characterization on power systems. (8)
(b).Explain briefly about the phenomena of how current distortion affects the voltage distortion under the presence of harmonics. (8)
6. (a) What are the general causes of harmonics in power systems. (8)
(b)What are the various causes of harmonics in distribution power system. (8)
7. (a) List the various effects of equipments due to harmonics. Explain briefly. (8)
(b)Explain the harmonic effects on power system equipments briefly. (8)
8. (a) What are the various classifications of harmonic sources and explain briefly about it. (8)
(b) Explain Harmonic source Identification Procedure for two source systems. (8)
9. Explain for the following:
(i) Harmonic sources from commercial loads.
(ii) Harmonic sources from industrial loads.
(iii) Harmonic sources from residential loads. (16)
10. (a) What is the need of locating harmonic sources? (8)
(b)How will you find the harmonic sources from point of common coupling? Give the identification procedure on the basis of voltage indices. (8)
11.(a).Explain the power system response characteristics under the presence of harmonics. (8)
(b).What is the need of IEEE standards used in harmonic studies.? Give their philosophy
and objective of these standards. (8)
12. Define for the following terms related with IEEE standards.
(i)SCR (ii) Load current (iii) Short circuit current (iv)Total harmonic distortion
(v)Total demand distortion (v) PCC (16)
UNIT V
POWER QUALITY MONITORING
PART – A
1. What are the importances of power quality monitoring?
2. What are the monitoring objectives?
3. What are the requirements of monitoring for a voltage regulation and unbalance?
4. What are the requirements of monitoring for a harmonic distortion?
5. What are the Characteristics of power line monitors?
6. What is the use of oscilloscope?
7. What is Spectrum analyzer?
8. What is FFT (or) digital technique used for harmonic analysis?
9. What is tracking generator?
10. What is the purpose of SVC?
11. Mention the three elements of power quality measurement.
12. What kind of power quality parameter do we want to measure?
13. List the advantages of automatic power quality monitoring system.
14. Classify the power quality monitoring.
15. What are the basic categories of power quality instruments?
16. What is flicker meter?
17. What is meant by power quality monitoring?
18. What are the specifications of power quality measuring equipments?
19. What are the necessary measurements to be made to know about the power quality of a product?
20. What is meant by online power quality monitoring?
21. What is the need for FFT Spectrum analyzer in power quality analyzers?
PART-B
1. (a)Explain Proactive monitoring. (8)
(b)Discuss in detail about the selection of power quality monitoring sites. (8)
2. Bring out the significance of Power quality monitoring. What is the important power quality
monitoring objectives.? (16)
3. (a) Bring out the important characteristics of power quality variations. (8)
(b)Explain the steps involved in power quality monitoring. What are the information from
monitoring site surveys. (8)
4. Write short notes on power quality measurement system.
What are the characteristics of power quality measurement equipments? (16)
5. Explain the harmonic analyzer and disturbance analyzer. (16)
6. (a) Explain in detail about Flicker meter. (8)
(b) Application of expert system for power quality monitoring. (8)
7. What are the various instruments used for power quality measurements?
What are the factors to be considered when selecting the instruments? (16)
8. Discuss in detail about the instruments used for analyzing non sinusoidal voltage and currents. (16)
9. (a)Explain the modern power quality monitors. (8)
(b)Draw and explain the functional structure of expert systems. (8)
10. Draw the block diagram of advanced power quality monitoring systems. Explain it. (16)