Aims

The course is designed to provide the students with the basic principles of High Voltage Engineering and to deepen their knowledge on the scientific principles behind the instruments and techniques used in the subject under consideration. During the course the students will have the opportunity to perform laboratory experiments using the high voltage facilities (Voltage up to 1 MV and currents reaching 200 kA) of the division for electricity and Lightning research. The course is a must if the students plan to pursue a carrier in industry either as a production engineer or as a researcher.

Content

Physics of electrical discharges: Ionisation, decay and cathode processes in air, Penning effect, breakdown in vacuum, break down in low pressures, Townsends mechanism, breakdown at high pressures, corona, streamer discharges, transition from streamer to arc, lightning discharge, resistance of spark channels, spark gaps, Time lags, breakdown under impulse conditions, breakdown mechanisms in liquids, breakdown mechanisms in solids.

Insulation co-ordination: Lightning impulse test voltage characteristics, Switching impulse test voltage characteristics, the gap factor, basic insulation level, statistical approach to insulation co-ordination, measurement of 50% breakdown probability, risk of failure, statistical safety factor, breakdown voltage correction for temperature, pressure and humidity.

Generation of high voltages and currents: Lightning impulses, Switching impulses, Generation of impulse voltages - single stage generators, multistage generators, Marx generator, circuit efficiency factor, shape efficiency factor , Generation of DC voltages - AC to DC conversion, Rectifier circuits, voltage doubler, cascade circuits, Van de Graff generator, Generation of AC voltages - single stage transformer, cascade transformer, resonant transformer, requirements of transformers in wet and pollution tests, Generation of high currents - current impulses used in testing air-crafts.

Measurement of high voltages and currents: Peak voltage measurements by spark gaps - sphere gaps, effects of nearby earthed objects, effects of humidity, effects of irradiation, effects of dust particles, uniform field gaps, rod gaps, Electrostatic Voltmeters, Resistive voltage dividers, Capacitive voltage dividers, Field mills, Rogowski coil, Coaxial shunt.

Instruction

Lectures and Laboratory work.

Assessment

Written examination at the end of the course. The laboratory work is compulsory.