Group A

Breakdown phenomena: Breakdown of gaseous medium, mechanism of charge
multiplication, secondary emission, Townsend theory, Streamer theory, Paschens law,
corona, effect of polarity of voltage on corona and breakdown process.
Breakdown of solid: Intrinsic breakdown, thermal breakdown, electro-mechanical
breakdown, streamer breakdown.
Breakdown of liquid: Breakdown of commercial liquid, cavitation theory, bubble theory,
suspended particle theory.
Insulating materials. Properties of traditional insulating materials, SF^, vacuum, air,
insulating oils, ceramics, epoxy resins, PVC, PTFF, PMMC, fibre glass, polyethylene.
Insulation resistance. Tacking index. Electrical and mechanical properties of insulators used
in transmission line. Different types of line insulators. String efficiency, bushings, general
design approach of bushing.
Cables: Different types of cables. Paper insulated cables, XLPE cables, gas-filled cables,
technology and principles. Generation of travelling waves in transmission lines, reflection
and transmission constants.
Power system grounding: Solid grounding, resistance grounding, reactance grounding,
grounding through earthing transformer, resonant grounding.

Group B

Voltage surges: Lightning phenomena, lightning induced overvoltage, direct stroke, indirect stroke-Protection of power stations and sub-stations and transmission line against direct strokes.
Protection of electrical apparatus against travelling waves. Lightning arrestors—expulsion
type, valve type, magnetic blow-out type and metal oxide type.
Insulation co-ordination: Determination of the line insulation, basic impulse level and
insulation level of substation equipment. Selection of lightning arrester. Establishment of
impulse withstand level. Overvoltage due to switching. Reduction of switching overvoltage.
Generation of high voltage and current in high voltage laboratory. Generation of high AC,
DC and impulse voltage. Generation of high impulse current, impulse generator, testing
transformer, source resonant circuit.
Non-destructive testing of- materials and electrical apparatus. Measurement of DC resistivity,
measurement of dielectric constant and loss factors, partial discharge measurement.
Preventive testing of insulation: High voltage testing of insulators, bushings, cables and
transformers. High voltage testing of surge diverters.


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