Ηλεκτρομονωτικά Υλικά
Description
Theory: Gaseous insulating substations, (GIS); Power switches with SF6 or gas mixtures as dielectrics, arc extinction. Environmental effects in the operation of GIS. Vacuum technology: high and ultra high vacuum technology. Vacuum switches in medium voltage applications. Solid insulators for high voltage applications: electrical ceramics and glass, composite glass-resin, polymer insulators, UV induced ageing effects. Dielectrics and nano-dielectrics. Liquid insulators: transformer oil types and quality control by physicochemical methods. Electron transport phenomena across metal-insulator interfaces: field emission, field ionization and mixed thermionic-field emission. Nano-particle contaminants and induced surface conductance. Breakdown mechanisms in the volume of insulators: avalanche effect, radiation induced conductivity, thermally stimulated currents, negative differential conductance. Interfaces, systems with one or two carrier types.
Laboratory exercises: Quadrupole mass spectrometry for the quality control of gaseous dielectrics: application in pristine SF6. Dielectric characterization of solid insulators in frequency domain.