EX-702-C High Voltage Engineering - Dec 2025 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. 7 Marks
   aExplain the concept of High Voltage (HV) technology. Discuss its significance in modern power systems and mention the different voltage levels classified under HV, EHV, and UHV.
   How to answer

   • Define High Voltage technology and its voltage range
   • Significance in transmission, insulation, testing and reliability of modern power systems
   • Classification thresholds for HV, EHV, UHV with typical kV levels
   • Examples of equipment/systems at each level
2. 7 Marks
   bDescribe the major applications of High Voltage (HV) technology in electrical and industrial fields. Highlight both power and non-power applications.
   How to answer

   • Define HV technology applications scope
   • Power applications: transmission, substations, testing, insulation
   • Non-power applications: medical, industrial, research
   • Highlight comparison of power vs non-power uses
3. 7 Marks
   aWhat is the need for generating high voltages in a laboratory environment? Describe different purposes and testing scenarios where HV generation is essential.
   How to answer

   • Need for HV generation for testing insulation and equipment
   • Purposes: type tests, routine tests, research
   • Testing scenarios: AC, DC, impulse withstand
   • Safety and design validation role of HV lab
4. 7 Marks
   bDescribe the primary and secondary ionization processes in gaseous dielectrics. How do these processes contribute to the breakdown of gases?
   How to answer

   • Define primary ionization: impact, photoionization
   • Define secondary ionization: secondary emission, photoemission
   • Townsend alpha, gamma coefficients role
   • How avalanche leads to breakdown
5. 7 Marks
   aDescribe the streamer mechanism of breakdown in non-uniform fields. How does it improve upon the Townsend theory in explaining practical gaseous breakdown?
   How to answer

   • Define streamer mechanism and non-uniform field condition
   • Steps: avalanche, space charge, photoionization, streamer propagation
   • Comparison with Townsend theory limitations
   • Why streamer explains practical/long-gap breakdown
6. 7 Marks
   bState and derive Paschen's law. Discuss the significance of the Paschen minimum and its practical implications for high voltage equipment design.
   How to answer

   • State Paschen's law: Vb as function of pd
   • Derivation from Townsend breakdown criterion
   • Explanation of Paschen minimum from curve
   • Practical implications for design, clearances, GIS
7. 7 Marks
   aExplain the principle of operation of a series resonant circuit used in high voltage testing. Derive the condition for resonance.
   How to answer

   • Circuit configuration of series resonant test system
   • Principle of voltage magnification at resonance
   • Derivation of resonance condition $X_L = X_C$ / $f_0 = 1/(2\pi\sqrt{LC})$
   • Advantages for HV testing of large capacitive loads
8. 7 Marks
   bDescribe the construction and working of the Cockcroft-Walton high voltage DC generator. List its advantages and limitations.
   How to answer

   • Circuit diagram of Cockcroft-Walton multiplier stages
   • Working: charging and voltage doubling per stage
   • Advantages: high DC, low ripple, compact
   • Limitations: voltage drop, poor regulation, load sensitivity
9. 7 Marks
   aExplain the triggering of an impulse generator using a three-electrode gap arrangement. Why is this method preferred? https://www.rgpvonline.com
   How to answer

   • Three-electrode gap arrangement and trigger pulse
   • Sequence of spark gap firing for impulse generation
   • Need for controlled simultaneous triggering
   • Reasons for preference: low jitter, reliability
10. 7 Marks
    bExplain the methods and instruments used for measuring surge currents. What challenges are encountered in measuring surge currents in high-voltage systems?
    How to answer

    • Methods: shunts, Rogowski coil, Hall sensors, CTs
    • Instruments for high magnitude fast transients
    • Challenges: bandwidth, saturation, EMI, isolation
    • Safety and calibration issues in HV systems
11. 7 Marks
    aDiscuss the working principle of potential dividers and compare the advantages and disadvantages of resistance dividers, capacitance dividers, and mixed RC potential dividers.
    How to answer

    • Working principle of potential dividers for HV scaling
    • Resistance divider: pros/cons
    • Capacitance and mixed RC divider: pros/cons
    • Comparison table for AC/DC/impulse suitability
12. 7 Marks
    bDiscuss the principle, construction, and operation of a standard sphere gap for measuring HV AC, DC, and impulse voltages. What are the main factors that influence the measurements?
    How to answer

    • Principle of sphere gap breakdown voltage measurement
    • Construction: spheres, gap adjustment, standards
    • Operation for AC, DC, impulse peak measurement
    • Factors: polarity, humidity, dust, nearby objects, irradiation
13. 7 Marks
    aWhat is a circuit breaker? Describe the short-circuit test and dielectric test performed on circuit breakers and their objectives.
    How to answer

    • Define circuit breaker and its function
    • Short-circuit test: procedure and objective
    • Dielectric test: procedure and objective
    • Importance for rating verification and safety
14. 7 Marks
    bWhat is an insulator in power systems? Describe the following tests conducted on insulators : * Mechanical Strength test * Puncture voltage test Why are these tests necessary?
    How to answer

    • Define insulator in power systems
    • Mechanical strength test procedure and purpose
    • Puncture voltage test procedure and purpose
    • Necessity for reliability and safety
15. 14 Marks
    Write a short note on any two :

    1. (a))Power transformer
    2. (b))Electrostatic voltmeter
    3. (c))Construction and working of a Tesla coil
    4. (d))Statistical and formative time lags in electrical breakdown
    How to answer

    • Select any two topics from (a)-(d)
    • For each: definition/construction, principle/working, key points
    • Relevant diagram/formula where applicable
    • Applications and significance in HV engineering