Sökning: "corona"

Visar resultat 1 - 5 av 96 avhandlingar innehållade ordet corona.

  1. 1. Electrical Charges on Polymeric Insulator Surfaces and their Impact on Withstand Performance

    Författare :Sarath Kumara; Chalmers University of Technology; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; impulse corona; Surface charge; impulse flashover voltage; corona charging; streamer criterion; surface potential decay; charge relaxation;

    Sammanfattning : Use of polymeric materials for high voltage outdoor insulation systems is increasing continuously. Insulating polymers gradually replace traditional materials like porcelain and glass and become dominant at ultra high voltages, e.g., in 1000 kV ac and 800 kV dc overhead power transmissions, which are presently being developed. LÄS MER

  2. 2. The coronal heating problem

    Författare :Boris V. Gudiksen; Göran Scharmer; James Klimchuk; Stockholms universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Solen; Corona; Magneto hydro dynamik; Astronomy and astrophysics; Astronomi och astrofysik;

    Sammanfattning : The heating of the solar corona has been investigated during four of decades and several mechanisms able to produce heating have been proposed. It has until now not been possible to produce quantitative estimates that would establish any of these heating mechanism as the most important in the solar corona. LÄS MER

  3. 3. Loss and recovery of hydrophobicity of polydimethylsiloxane after exposure to electrical discharges

    Författare :Henrik Hillborg; KTH; []
    Nyckelord :silicone rubber; polydimethysiloxane; dydrophobicity; corona; air-plasma; oxygen-plasma; surface characterisation;

    Sammanfattning : Silicone rubber based on polydimethylsiloxane is used ashigh voltage outdoor insulation, due to its ability to preservethe hydrophobic surface properties during service and evenregain hydrophobicity after exposure to electrical discharges.The underlying processes for the hydrophobic recovery arediffusion of low molar mass siloxanes from the bulk to thesurface and reorientation by conformational changes ofmolecules in the surface region. LÄS MER

  4. 4. Microwave Breakdown in Inhomogeneous Fields

    Författare :Joel Rasch; Chalmers University of Technology; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; corona; inhomogeneous fields; Microwave breakdown; multipactor;

    Sammanfattning : Microwave breakdown continues to be a risk in many applications involving the transmission and reception of microwave frequency signals. Satellite communication is especially interesting from the research point of view because of the extreme costs, and limited testing possibilities. LÄS MER

  5. 5. Partial Discharges at Repetitive Rapidly Changing Voltages

    Författare :Elisabeth Lindell; Chalmers University of Technology; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; high dV dt; oil paper insulation.; repetitive voltages; short rise time; partial discharge measuring techniques; twisted pair; square-like voltages; corona; Partial discharges PDs ;

    Sammanfattning : Electrical insulation can today be exposed to voltages having considerably higherfrequency components than the conventional power frequency AC 50 Hz or 60 Hz,for example due to the increased use of power electronics in power systems. Thishas in a number of cases caused unexpected behaviour, including failures. LÄS MER