EX-802-A Power Quality Problems and Mitigation Techniques - May 2023 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 6 Marks
   aWhat are the major Power Quality issues? Explain in detail.
   How to answer

   • Define major power quality issues: sags, swells, interruptions, transients, harmonics, flicker, unbalance
   • Explain characteristics: magnitude, duration, frequency spectrum
   • Discuss effects on equipment and system
2. 8 Marks
   bDefine Power Quality. Explain the reasons for increased concern in power quality.
   How to answer

   • Define power quality as per IEEE
   • Explain increased concern: power electronics loads, sensitive loads, deregulation
   • Discuss economic and technical reasons
3. 7 Marks
   aBriefly explain the Causes of power quality disturbances.
   How to answer

   • List causes: faults, switching, nonlinear loads, lightning, capacitor switching
   • Briefly explain each source
   • Relate to type of disturbance produced
4. 7 Marks
   bWrite short notes on Classification and working of passive series compensation.
   How to answer

   • Define passive series compensation
   • Give classification: series capacitors, reactors
   • Explain working principle and power quality improvement
5. 7 Marks
   aBriefly explain the Operation of DSTATCOM with neat sketch.
   How to answer

   • Define DSTATCOM and its shunt connection
   • Explain operation with VSC and DC link
   • Provide neat sketch showing source, VSC, coupling
6. 7 Marks
   bWhat are the power quality problems due to reactive power component of currents?
   How to answer

   • Define reactive power component of current
   • Explain low power factor, voltage drop, losses
   • Discuss harmonics, overloading and instability issues
7. 7 Marks
   aWhat are the advantages of UPQC?
   How to answer

   • Define UPQC with series and shunt APF
   • List advantages: sag/swell, harmonics, reactive power compensation
   • Mention load and source side benefits
8. 7 Marks
   bHow the UPQC are classified? Explain briefly.
   How to answer

   • Give basis of classification: supply system, converter topology, control
   • Explain single-phase, three-phase, left/right shunt types
   • Brief comparison of types
9. 7 Marks
   aWrite the differences between UPQC and DSTATCOM in operation.
   How to answer

   • Define UPQC and DSTATCOM configurations
   • Compare series vs shunt compensation functions
   • Tabulate differences in operation and mitigation capability
10. 7 Marks
    bExplain about the fundamentals of wave form distortion.
    How to answer

    • Define waveform distortion and harmonics
    • Explain Fourier fundamentals, THD concept
    • Discuss sources and effects of distortion
11. 7 Marks
    aDiscuss about the sources of sags and interruption and Describe the mitigation of voltage sag.
    How to answer

    • Define voltage sag and interruption sources: faults, motor starting
    • Explain mitigation: DVR, UPS, fast transfer
    • Describe control for sag mitigation
12. 7 Marks
    bExplain how the voltage sag performance is estimated?
    How to answer

    • Define sag performance indices: SARFI, magnitude-duration
    • Explain stochastic estimation and monitoring method
    • Discuss calculation steps using fault analysis
13. 6 Marks
    aDefine the following terms:

    1. i)Harmonics
    2. ii)Harmonic indices
    3. iii)Crest factor
    4. iv)TDD
    5. v)THD
    6. vi)Inter harmonics.
    How to answer

    • Define harmonics, harmonic indices, crest factor
    • Define TDD, THD, interharmonics with formulas
    • Give typical values and significance
14. 8 Marks
    bMention the harmonic sources from industrial loads and commercial loads.
    How to answer

    • List industrial loads: drives, rectifiers, arc furnaces
    • List commercial loads: computers, lighting, UPS
    • Mention harmonic order generated by each
15. 14 Marks
    Write short notes on any two of the following:

    1. a)Non linear loads causing power quality problems.
    2. b)Sources of transient over voltages.
    3. c)What are the power quality problems a UPQC can mitigate?
    4. d)Explain the operation of harmonic analyzer.
    How to answer

    • Select any two topics with definition and causes
    • Explain effects and mitigation for each
    • Give examples and neat sketch where relevant