Sökning: "Positive leader discharges"

Visar resultat 1 - 5 av 7 avhandlingar innehållade orden Positive leader discharges.

  1. 1. Features of the Electric Fields Generated by Lightning with Special Attention to Positive Ground Flashes

    Författare :Dalina Johari; Vernon Cooray; Mahbubur Rahman; Fridolin Heidler; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; positive ground flashes; preliminary breakdown pulses; multiple-trains PBPs; positive leader; bidirectional leader; negative leader branch; subsequent return strokes; distant lightning; Engineering Science with specialization in Atmospheric Discharges; Teknisk fysik med inriktning mot atmosfäriska urladdningar;

    Sammanfattning : This thesis focuses on the main processes in positive ground flashes and the distant lightning environment for both positive and negative ground flashes. It presents the characteristics of the preliminary breakdown pulses (PBPs), the characteristics of the electric field pulses observed during leader propagation, and the characteristics of the electric fields produced by the first and the subsequent return strokes. LÄS MER

  3. 2. Numerical modelling of positive electrical discharges in long air gaps

    Författare :Oscar Diaz; Vernon Cooray; Raul Montano; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; high voltage techniques; numerical modeling; electrical discharge in gases; streamer mechanism; leader channel; Engineering Science with specialization in Atmospheric Discharges; Teknisk fysik med inriktning mot atmosfäriska urladdningar;

    Sammanfattning : This dissertation deals with research on the numerical modelling of electrical discharges in laboratory long air gaps excited with positive switching impulses. It begins with the preliminary work of several scientists during the last decades, making a detailed analysis of different approaches for modelling all the stages in a full discharge. LÄS MER

  4. 3. On The Initiation of Upward Positive Leader Discharges During Lightning Strikes

    Författare :Marley Becerra; Uppsala universitet; []
    Nyckelord :TECHNOLOGY; TEKNIKVETENSKAP;

    Sammanfattning : .... LÄS MER

  5. 4. Numerical Simulations of Long Spark and Lightning Attachment

    Författare :Liliana Arevalo; Vernon Cooray; Dan Windmar; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; breakdown; discharge; leader channel; lightning attachment; negative discharge; positive discharge; streamer; Electrical engineering; Elektroteknik; Engineering Science with specialization in Atmospheric Discharges; Teknisk fysik med inriktning mot atmosfäriska urladdningar;

    Sammanfattning : The research work presented here is concerned with numerical simulations of two different electrical phenomena: Long gap electrical discharges under switching impulses and the lightning attachment process associated with positive upward leaders. The development of positive upward leaders and the progression of discharges in long gaps are attributable to two intertwined physical phenomena, namely, the leader channel and the streamer zone. LÄS MER

  7. 5. On the Attachment of Lightning Flashes to Grounded Structures

    Författare :Marley Becerra; Vernon Cooray; Rajeev Thottappillil; Mats Boman; Ivo Gallimberti; Uppsala universitet; []
    Nyckelord :Engineering physics; Lightning; Lightning attachment; Positive leader discharges; Lightning protection; Thunderstorms; Numerical modeling; Teknisk fysik;

    Sammanfattning : This thesis deals with the physical modeling of the initiation and propagation of upward positive leader discharges from grounded structures during lightning strikes. It includes the analysis of upward leaders initiated under the influence of the electric field produced by a dominant negative cloud charge and due to the combined action of a negative thundercloud and a descending downward stepped negative leader. LÄS MER