Buildings’ Air-termination System Arrangement Under The Shielding Effect

Reasonable placement of air-termination system has important significance to lightning protection. Under the shielding effect, the buildings’lghtning striking probability, lightning development path and the air-termination system’protection scope are important to air-termination system’s placement.This thesis studies the IEC formula, the Collection Volume Method and the stochastic simulation method, calculating buildings’lghtning striking probability. Combining with calculated data, the thesis simulate equipotential surface profile around the buildings using the finite difference method to analyze the shielding effect. The lightning leader’s fractal development path is studied in the synthetic electric field, including thunderstorm atmospheric electric field, lightning leader generating electric field and induced charge on buildings generating electric field. Under the shielding effect, according to buildings’ ghtning striking probability and lightning development path, the air-termination systems’quantity can be reduced on the basis of the lightning protection requirements. The details of research are as follows:The lightning striking condition of the architectural complex is studied on the basis of building’s lightning striking probability factors. Combining with calculated data, the equipotential surface profile simulated with the MATLAB software around the buildings is to point out the shielding effect and the influence that surrounding ones to a building’s lightning striking probability. The thesis uses finite difference method to simulate. This method chooses the grid which is constitutede by finite discrete points instead of the continuous domain, using the difference form to show the partial derivative function in the partial differential equations and getting the approximate solution in the whole area through the function of a finite grid nodes.On the basis of downward leader generating electric field, the interrelation between lightning leader and buildings is discussed, pointing out the distribution of buildings induced charge, which impacts on the electric field. Using the method of image obtains the distribution of buildings surface charge and analyzing the induced charge of circular roof generates electric field on the basis of the symmetry of the ring. This thesis establishs lightning leader stochastic model, pointing out the synthetic electric field, including thunderstorm atmospheric electric field, lightning leader generating electric field and induced charge on buildings generating electric field. According to the development probability, the lead’s next step is randomly selected from all the neighboring points to be developed, verifying the influence of synthetic electric field on the direction of development of the leader, which is useful in understanding the lightning leader connection process.On the basis of rolling ball method, introducing the attractive radius of air-termination system and the cross-section area of Collection Volume Method is to analyze the protection scope of the air-termination system, and the lightning stroke simulation tests its feasibility. According to lightning in design, this thesis puts forward the buildings’ air-termination system arrangement and the way of combining concealed laying lightning tape (net) and short lightning rod to prevent lightning. Within certain height and spacing, if building had smaller lghtning striking probability and was in the cross-section area of Collection Volume Method of other air-termination system, the air-termination systems’ quantity can be reduced.