Some Recent Developments In Safety Related Lightning Phenomenology

摘要

Lightning presents an ever present hazard to both individuals and to high consequence operations. Although the subject has been under study for some two centuries or so, it is still not fully understood and indeed continues to throw up new surprises, some of which lead to disastrous consequences. This paper deals with two lightning phenomena which both have the potential for causing unwanted consequences. One is relatively well known but where the consequences have not been fully analysed. The other is relatively new and where we are currently seeking to understand its underlying physical basis and potential consequences. The first phenomenon is associated with the lightning induced ejection of material at a buried conducting discontinuity in a re-bar structure. In the past this has led to an 'apparently well protected' storage munition facility to suffer disastrous consequences. This paper develops some analytic models which characterize the properties of the ejected material from such an event. The second phenomenon arises as a result of a lightning strike surveys carried out at munition sites in the UK which have apparently registered phenomenally large stroke currents and phenomenally large flash rates. This paper seeks to look for possible explanations for this phenomenon, and its potential consequences. Both topics are of core interest in the field of high consequence system safety.