Invetigation On Lightning Striking Characteristic Of Tall Buildings Based On Collection Volume Method

The Electrogeometric Model (EGM) which is widely accepted relates striking distance to the prospective peak stroke current. It is a oversimplified model because the striking distance is a constant value for a given prospective peak stroke current. Furthermore, we can't evaluate the influence of the buildings nearby on calculating the annual frequency of strike to structure. So far, we havn't put forward a efficient method for analyzing the lightning strike status of building colony.This paper introduces a more physically-based method which is so called the Collection Volume Method (CVM). The CVM takes a more physical approach than the basic EGM by using the well-known fact that the striking distance is dependent on both the peak stroke current (or downleader charge) and the degree of electric field enhancement. We propose a more efficient method which reflects the stochastic character of lightning stroke. We can analyze the lightning strike status of building colony using this new method.This paper describes how to calculate the annual frequency of lightning strike to air terminations and buildings in details. In this method, the attractive volume of a air termination or building is defined in terms of the lightning polarities. The exposure surfaces are located inside the attractive volume according to the striking distances. In order to obtain its equivalent exposure area, the integral of the probability density functions is performed on the exposure surfaces with respect to downward leader approach angle and striking distance. Then, the annual frequency of lightning strike to the air termination or building can be estimated by the equivalent exposure area and ground flash density. In order to verify its validity, a simulation test was conducted. Then the calculated result is compared with the measured results and both results are consistent. This new annual frequency of lightning strike which is based on CVM has comparatively higher precision and it can be applicated in practical lightning protection project.