Calculation of attractive area by using attractive volume concept for lightning protection systems

Abstract

Lightning protection system is needed at a structure if its possible risk due to lightning strikes is greater than accepted risk. The possible risk can be acquired by calculating frequency of lightning strikes to the structure. The frequency of lightning strikes itself, needs a calculation of attractive area of the structure to be done first. There are several methods available for calculating the attractive area of the structure, but this thesis only concern about attractive volume concept which can give better risk assessment than the other methods. An attractive volume is a volume that contains all possible orientation point from which lightning can strike our structure. The area within this volume is called attractive area and it can be calculated easily by dividing this volume into several sections. Based on this method, we build a computer program to make the calculation of attractive area of a square roof building. At each section of the attractive volume of the building, its horizontal cross section area will be calculated. For a rectangular roof building that has lightning rods installed on its roof, the horizontal cross section area of the building will be reduced by the horizontal cross section of the lightning rods. Thus, the arrangement of the rods should be noticed. There are 9 arrangement of the rods discussed in this thesis. The arrangement figure and the detail information on how we calculate the horizontal cross section area are given in this thesis. Aside from giving the predicted frequency of lightning strike to the structure, the program also show figures of horizontal cross section area at certain orientation distance. This picture can help the user of the program from deciding which arrangement of the rods that is suitable for their building