Effect of the structure height and lightning current on attracting range of the structure for lightning protection design

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Effect of the structure height and lightning current on attracting range of the structure for lightning protection design

 

Author: Yuen, Ka-hang
Title: Effect of the structure height and lightning current on attracting range of the structure for lightning protection design
Degree: M.Eng.
Year: 2010
Subject: Hong Kong Polytechnic University -- Dissertations
Sustainable buildings -- Design and construction
Lightning protection
Lightning rods
Department: Dept. of Building Services Engineering
Pages: x, 101 leaves : ill. ; 31 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b2356389
URI: http://theses.lib.polyu.edu.hk/handle/200/5802
Abstract: Traditional lightning research focuses on the leader inception model. The effects of structure (e.g. building, tower, lightning rod, etc.) height and lightning current on lightning protection design are seldom considered, the absence of research in this area is the main motivation behind the study. The purpose of this project is to evaluate the possible effects of the structure height and lightning current on the lightning protection design by simulation model, i.e. geometry-electromagnetic model (GEM), so as to propose the simulation model that can easily use for the lightning protection design. This study employs fundamental knowledge of lightning theories to develop a simulation model for assessing the effect of the height of lightning rod and building structure, and different intensity lightning current on the attracting volume (AV) for lightning protection design. Maximum Collection Volume (MCV) concept was developed in this study. Leader Initiation Volume (LIV) approach were chosen to evaluate the striking distance of the structure. The geometry-electromagnetic model was adopted to predict the influence of the height and current.
The results showed that leader initiation volume, maximum collection volume and attracting volume can be reasonably simulated by the proposed model. The simulation was successful and the proposed simulation model is feasible. The results of the simulation show that the height of earthed object and the lightning are the two dominant factors affecting the attracting range of the structure for lightning protection design. The results also show that influence of the radius is small, so the influence can be neglected. But in a specific case when the height is similar to the radius, the attracting range would be affected. On the other hand, the results illustrate that the building's width would affect the attractive volume of the building, however this factor is not affect the collection area which is used for risk assessment. An application of the geometry-electromagnetic model was implemented for illustrating the prediction of the attractive range of the structure, protection angle of lightning rod and the collection area of the building structure. Directly applying the LIV approach to building structure is not recommended, as this approach is only used for the prediction of striking distance of lightning rod. The result generated from the simulation model were used to evaluate an International standard -IEC 62305 for the lightning protection design. The results proved that there are some area in the international standard should be considered. Some recommended values for lightning protection angle for the lightning rod placement and collection area for the risk assessment are under or over estimated. The study also is a prior study that can give a direction to study on the evaluation of the attracting range of structure.

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