EX-702-C High Voltage Engineering - Nov 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. 7 Marks
   aDiscuss advantages and limitations of high transmission voltage transmission.
   How to answer

   • Define high transmission voltage levels and purpose
   • List advantages: reduced current, losses, voltage drop, efficiency
   • List limitations: insulation, corona, safety, cost, equipment rating
   • Conclude with trade-off
2. 7 Marks
   bHow does a breakdown voltage discharge happen in a deep vacuum? What makes arcing inside it?
   How to answer

   • Define vacuum breakdown vs gas breakdown
   • Describe field emission and particle mechanisms in deep vacuum
   • Explain development of discharge and arcing
   • Factors causing arcing: electrodes, microparticles, outgassing
3. 7 Marks
   aExplain the partial discharge tests on High-Voltage Cables. How is a fault in the Insulation located in this test?
   How to answer

   • Define partial discharge in cables
   • Describe test circuit and procedure for HV cables
   • Explain detection and measurement method
   • Explain fault location in insulation from test results
4. 7 Marks
   bDefine Townsend's first and second ionization coefficients. How is the condition for breakdown obtained in a Townsend discharge?
   How to answer

   • Define Townsend first ionization coefficient alpha
   • Define Townsend second ionization coefficient gamma
   • Derive current growth equation
   • Obtain breakdown condition gamma*(exp(alpha*d)-1)=1
5. 7 Marks
   aA Tesla coil creates high frequency and high voltage. Why does this allow current to flow in objects that are near the coil?
   How to answer

   • Define Tesla coil operation: resonance, high frequency high voltage
   • Explain electromagnetic induction and capacitive coupling
   • Explain why nearby objects pick up current
   • Role of high frequency in reducing skin effect impedance
6. 7 Marks
   bWhat is the difference between a high voltage test and an insulation resistance test whereas both are basically insulation tests?
   How to answer

   • Define high voltage test purpose and voltage levels
   • Define insulation resistance test purpose and method
   • Compare on voltage, purpose, destructiveness
   • Conclude both are insulation tests with different objectives
7. 7 Marks
   aWhat is the principle of a sphere gap for measurement of high voltages? Explain how the sphere gap can be used to measure the peak value of voltages. What are the parameters and factors that influence such voltage measurement?
   How to answer

   • State sphere gap breakdown principle
   • Explain setup for peak voltage measurement
   • List procedure and calibration with gap-spacing tables
   • Discuss influencing parameters: spacing, diameter, humidity, polarity
8. 7 Marks
   bWith the help of a suitable diagram, describe the principle of operation of the generating voltmeter used for measuring high DC voltages.
   How to answer

   • Show schematic of generating voltmeter with rotating vanes
   • Explain electrostatic induction and charge generation
   • Derive relation of generated current to DC voltage
   • State advantages and limitations
9. 7 Marks
   aWhat are the conditions to be satisfied by a potential divider to be used for impulse work?
   How to answer

   • Define potential divider for impulse measurements
   • List requirements: ratio stability, bandwidth, loading
   • Explain stray capacitance and inductance effects
   • Conditions for faithful impulse reproduction
10. 7 Marks
    bMention the different electrical tests done on isolators and circuit breakers.
    How to answer

    • List power frequency and impulse tests on isolators
    • List tests on circuit breakers: dielectric, temperature rise, breaking
    • Brief purpose of each electrical test
    • Standards reference
11. 7 Marks
    aHow are insulators tested to determine flash-over voltages?
    How to answer

    • Define flash-over voltage of insulators
    • Describe dry and wet flash-over test procedure
    • Explain test setup and voltage application
    • Criteria for determination of flash-over value
12. 7 Marks
    bWhat is high voltage test? Why do transformers have high voltage tests?
    How to answer

    • Define high voltage test
    • Explain purpose: verify insulation strength
    • Explain why transformers need HV tests: windings, bushings
    • List types of HV tests on transformers
13. 7 Marks
    aHow many pouring methods are there for a motor coil insulating paint?
    How to answer

    • Define motor coil insulating paint impregnation
    • List pouring/dipping methods
    • Brief procedure of each method
    • Purpose of void-free insulation
14. 7 Marks
    bWhat do you understand by "intrinsic strength" of solid dielectric? How does breakdown occur due to electrons in a solid dielectric?
    How to answer

    • Define intrinsic strength of solid dielectric
    • Explain electronic breakdown theory
    • Describe electron avalanche and lattice interaction
    • Factors affecting intrinsic breakdown
15. 7 Marks
    aWhat is the method of control tripping of impulse generator? Why triggering is required in an impulse generator?
    How to answer

    • Define impulse generator and need for synchronized firing
    • Describe controlled tripping methods: trigatron, three-electrode gap
    • Explain why triggering is required for timing and reproducibility
    • Waveform control aspects
16. 7 Marks
    bWhat do you understand by Surge current measurement, Cavity breakdown, Paschen's law? Explain each.
    How to answer

    • Define surge current measurement method
    • Explain cavity breakdown in solid insulation
    • State Paschen's law and its curve
    • Explain each with formula and application