On the Attachment of Lightning Flashes to Grounded Structures

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. Thus, a self-consistent model based on the physics of leader discharges is developed for the evaluation of the attachment of lightning flashes to any kind of grounded structure. The predictions of the model have been found to be in good agreement with the results of laboratory long air gap experiments and with classical and altitude rocket triggered lightning experiments.Due to the high application level and predictive power of the developed model, several contributions to the physical understanding of factors influencing the initiation and propagation of upward positive leaders during thunderstorms have been made. For instance, it has been found that the initiation of upward connecting leaders is strongly affected by the average velocity of the downward stepped leader. Similarly, it is shown that the switching voltage impulses used in the laboratory do not “fairly approximate” the electric fields produced by a descending downward leader, as claimed by supporters of Early Streamer Emission (ESE) devices. Furthermore, it is found that the space charge layer created by corona at ground level significantly increases the thundercloud electric fields …


1 Introduction
1.1 The lightning protection problem
1.2 Towards a better physical understanding of the attachment of lightning flashes to grounded structures
1.3 The context of this thesis
2 Initiation of lightning upward positive leaders
2.1 Positive leader discharges
2.2 Existing leader inception models
2.3 The proposed leader inception model
2.3.1 Evaluation of the static upward leader inception
2.3.2 Evaluation of the dynamic upward leader inception
2.4 On the validity of the existing leader inception models for lightning studies
2.5 On the validity of the Early Streamer Emission claim
2.6 The space charge layer and the initiation of upward lightning
3 Interception of downward lightning stepped leaders by upward connecting leaders
3.1 Leader propagation models
3.2 Self-consistent modelling of the upward leader propagation
3.3 A Self-consistent Lightning Interception Model –SLIM –
4 Lightning attachment to complex grounded structures
4.1 The International Standard on protection of structures against lightning
4.2 Physics-based analyses of lightning attachment to grounded structures
5 Conclusions
6 Future work
8 Acknowledgments

Author: Becerra, Marley

Source: Uppsala University Library

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