Assessment of protection system positioning and models using observations of lightning strikes to structures

Abstract

This paper presents the results of an analysis of the observed incidence of lightning strikes to a wide range of earthed structures in Hong Kong. The data were obtained for 161 structures and span the period 1988{1996. These structures were protected with lightning air terminals, placed in the optimum locations on each structure using a new positioning method which is an improvement of the simple`electrogeometric model'. The aims of the paper are fourfold, namely to assess (i) the e¬ectiveness of this new lightning protection positioning method, (ii) the validity of various attractive radius models, especially since many of the structures are located in high-density city blocks, (iii) the validity of a Poisson model for describing the strike frequency, and(iv) the e¬ect of any assumed height dependence of the median peak current on the attractive radius models.The results show a signi cant positive correlation between expected and actual strike frequency and con rm that the interception e¯ciency of the lightning protection system is in accord with the speci ed protection levels. In general, attractive radius and Poisson strike models for`free-standing' structures are found to be valid except for structures of height less than 100 m in dense city blocks. The results also show an in®uence due to positive ®ashes and a decrease in attractive radius if the peak lightning stroke current is assumed to be dependent on the structure height.

Switching impulse discharge characteristics of UHV transmission line air gaps

“…Subsequently, the point charge Q at a distance s from the surface of the high-voltage electrode is set in the finite element simulation software. Since the initial leader length is about 0.7 m [22,23], it can be considered that s is in the range 0.3-0.7 m. Then, the boundary conditions should be set such that the potential at infinity is zero and the ground electrode is grounded. Although the high-voltage electrode is an equipotential body, the surface potential is actually a point outside the electrode, so no relevant boundary conditions are set.…”

Estimation of lightning current amplitudes incident to wind turbines in exposed locations

“…Furthermore, a dependence between the lightning current amplitudes and the incident free‐standing structure's (effective) height has apparently been found. However, the reasons for this dependence are not well understood nor established and are still a subject of ongoing investigation; interested reader is advised to consult, e.g., for more information and possible explanations of this dependence. More specifically, according to , this dependence could be attributed to downward lightning strikes and may be due to connection of an upward leader initiated from a structure with one of the branches of a downward lightning channel.…”

“…However, the reasons for this dependence are not well understood nor established and are still a subject of ongoing investigation; interested reader is advised to consult, e.g., for more information and possible explanations of this dependence. More specifically, according to , this dependence could be attributed to downward lightning strikes and may be due to connection of an upward leader initiated from a structure with one of the branches of a downward lightning channel. Moreover, the lightning flash, in downward lightning, may terminate at two or more points on the ground (or structure) almost simultaneously, which may give rise to this phenomenon.…”

Attachment of lightning flashes to grounded structures

“…Later, the collection volume concept proposed by Eriksson [62,63] for free standing structures was used for the analysis of lightning strikes to buildings [32], together with electric field intensification factors [93]. Even though this method is claimed to be validated with field observations [127,128], there are still doubts in the lightning community about its use [35,36,120]. Recently, a leader progression model similar to the one proposed by Dellera and Garbagnati [65,66] was implemented in three dimensions to evaluate the lightning incidence to buildings [129].…”